title: G-gerbes, principal 2-group bundles and characteristic classes

abstract:
  Let $G$ be a Lie group and $G\to\Aut(G)$ be the canonical group homomorphism
induced by the adjoint action of a group on itself. We give an explicit
description of a 1-1 correspondence between Morita equivalence classes of, on
the one hand, principal 2-group $[G\to\Aut(G)]$-bundles over Lie groupoids and,
on the other hand, $G$-extensions of Lie groupoids (i.e.\ between principal
$[G\to\Aut(G)]$-bundles over differentiable stacks and $G$-gerbes over
differentiable stacks). This approach also allows us to identify $G$-bound
gerbes and $[Z(G)\to 1]$-group bundles over differentiable stacks, where $Z(G)$
is the center of $G$. We also introduce universal characteristic classes for
2-group bundles. For groupoid central $G$-extensions, we introduce
Dixmier--Douady classes that can be computed from connection-type data
generalizing the ones for bundle gerbes. We prove that these classes coincide
with universal characteristic classes. As a corollary, we obtain further that
Dixmier--Douady classes are integral.


title: Packing 3-vertex paths in cubic 3-connected graphs

abstract:
  Let v(G) and p(G) be the number of vertices and the maximum number of
disjoint 3-vertex paths in G, respectively. We discuss the following old
Problem: Is the following claim (P) true ?
  (P) if G is a 3-connected and cubic graph, then p(G) = [v(G)/3], where
[v(G)/3] is the floor of v(G)/3.
  We show, in particular, that claim (P) is equivalent to some seemingly
stronger claims. It follows that if claim (P) is true, then Reed's dominating
graph conjecture (see [14]) is true for cubic 3-connected graphs.


title:
Efficient prediction of thermodynamic properties of quadrupolar fluids
  from simulation of a coarse-grained model: The case of carbon dioxide

abstract:
  Monte Carlo simulations are presented for a coarse-grained model of real
quadrupolar fluids. Molecules are represented by particles interacting with
Lennard-Jones forces plus the thermally averaged quadrupole-quadrupole
interaction. The properties discussed include the vapor-liquid coexistence
curve, the vapor pressure along coexistence, and the surface tension. The full
isotherms are also accessible over a wide range of temperatures and densities.
It is shown that the critical parameters (critical temperature, density, and
pressure) depend almost linearly on a quadrupolar parameter $q=Q^{*4} /T^*$,
$Q^*$ is the reduced quadrupole moment of the molecule and $T^*$ the reduced
temperature.
  The model can be applied to a variety of small quadrupolar molecules. We
focus on carbon dioxide as a test case, but consider nitrogen and benzene, too.
Experimental critical temperature, density and quadrupolar moment are
sufficient to fix the parameters of the model. The resulting agreement with
experiments is excellent and marks a significant improvement over approaches
which neglect quadrupolar effects. The same coarse-grained model was also
applied in the framework of Perturbation Theory (PT) in the Mean Spherical
Approximation (MSA). As expected, the latter deviates from the Monte Carlo
results in the critical region, but is reasonably accurate at lower
temperatures.


title: On the iterative decoding of sparse quantum codes

abstract:
  We address the problem of decoding sparse quantum error correction codes. For
Pauli channels, this task can be accomplished by a version of the belief
propagation algorithm used for decoding sparse classical codes. Quantum codes
pose two new challenges however. Firstly, their Tanner graph unavoidably
contain small loops which typically undermines the performance of belief
propagation. Secondly, sparse quantum codes are by definition highly
degenerate. The standard belief propagation algorithm does not exploit this
feature, but rather it is impaired by it. We propose heuristic methods to
improve belief propagation decoding, specifically targeted at these two
problems. While our results exhibit a clear improvement due to the proposed
heuristic methods, they also indicate that the main source of errors in the
quantum coding scheme remains in the decoding.


title:
Orbital moment of a single Co atom on a Pt(111) surface - a view from
  correlated band theory

abstract:
  The orbital magnetic moment of a Co adatom on a Pt(111) surface is calculated
in good agreement with experimental data making use of the LSDA+U method. It is
shown that both electron correlation induced orbital polarization and
structural relaxation play essential roles in orbital moment formation. The
microscopic origins of the orbital moment enhancement are discussed.


title:
Structural tendencies - Effects of adaptive evolution of complex
  (chaotic) systems

abstract:
  We describe systems using Kauffman and similar networks. They are directed
funct ioning networks consisting of finite number of nodes with finite number
of discr ete states evaluated in synchronous mode of discrete time. In this
paper we introduce the notion and phenomenon of `structural tendencies'.
  Along the way we expand Kauffman networks, which were a synonym of Boolean
netw orks, to more than two signal variants and we find a phenomenon during
network g rowth which we interpret as `complexity threshold'. For simulation we
define a simplified algorithm which allows us to omit the problem of periodic
attractors. We estimate that living and human designed systems are chaotic (in
Kauffman sens e) which can be named - complex. Such systems grow in adaptive
evolution. These two simple assumptions lead to certain statistical effects
i.e. structural tendencies observed in classic biology but still not explained
and not investigated on theoretical way. E.g. terminal modifications or
terminal predominance of additions where terminal means: near system outputs.
We introduce more than two equally probable variants of signal, therefore our
networks generally are not Boolean networks. T hey grow randomly by additions
and removals of nodes imposed on Darwinian elimination. Fitness is defined on
external outputs of system. During growth of the system we observe a phase
transition to chaos (threshold of complexity) in damage spreading. Above this
threshold we identify mechanisms of structural tendencies which we investigate
in simulation for a few different networks types, including scale-free BA
networks.


title:
Measuring the deformation of a ferrogel sphere in a homogeneous magnetic
  field

abstract:
  A sphere of a ferrogel is exposed to a homogeneous magnetic field. In
accordance to theoretical predictions, it gets elongated along the field lines.
The time-dependence of the elastic shear modulus causes the elongation to
increase with time analogously to mechanic creep experiments, and the rapid
excitation causes the sphere to vibrate. Both phenomena can be well described
by a damped harmonic oscillator model. By comparing the elongation along the
field with the contraction perpendicular to it, we can calculate Poisson's
ratio of the gel. The magnitude of the elongation is compared with the
theoretical predictions for elastic spheres in homogeneous fields.


title: Matrix Graph Grammars

abstract:
  This book objective is to develop an algebraization of graph grammars.
Equivalently, we study graph dynamics. From the point of view of a computer
scientist, graph grammars are a natural generalization of Chomsky grammars for
which a purely algebraic approach does not exist up to now. A Chomsky (or
string) grammar is, roughly speaking, a precise description of a formal
language (which in essence is a set of strings). On a more discrete
mathematical style, it can be said that graph grammars -- Matrix Graph Grammars
in particular -- study dynamics of graphs. Ideally, this algebraization would
enforce our understanding of grammars in general, providing new analysis
techniques and generalizations of concepts, problems and results known so far.


title:
Homogeneous geodesics of non-unimodular Lorentzian Lie groups and
  naturally reductive Lorentzian spaces in dimension three

abstract:
  We determine, for all three-dimensional non-unimodular Lie groups equipped
with a Lorentzian metric, the set of homogeneous geodesics through a point.
Together with the results of [C] and [CM2], this leads to the full
classification of three-dimensional Lorentzian g.o. spaces and naturally
reductive spaces.


title: Exact symmetry breaking ground states for quantum spin chains

abstract:
  We introduce a family of spin-1/2 quantum chains, and show that their exact
ground states break the rotational and translational symmetries of the original
Hamiltonian. We also show how one can use projection to construct a spin-3/2
quantum chain with nearest neighbor interaction, whose exact ground states
break the rotational symmetry of the Hamiltonian. Correlation functions of both
models are determined in closed form. Although we confine ourselves to
examples, the method can easily be adapted to encompass more general models.

categories: cond-mat.str-el math-ph math.MP quant-ph


title:
Local and Nonlocal Strain Rate Fields and Vorticity Alignment in
  Turbulent Flows

abstract:
  Local and nonlocal contributions to the total strain rate tensor at any point
in a flow are formulated from an expansion of the vorticity field in a local
spherical neighborhood of radius R centered on x. The resulting exact
expression allows the nonlocal (background) strain rate tensor to be obtained
from the total strain rate tensor. In turbulent flows, where the vorticity
naturally concentrates into relatively compact structures, this allows the
local alignment of vorticity with the most extensional principal axis of the
background strain rate tensor to be evaluated. In the vicinity of any vortical
structure, the required radius R and corresponding order n to which the
expansion must be carried are determined by the viscous lengthscale. We
demonstrate the convergence to the background strain rate field with increasing
R and n for an equilibrium Burgers vortex, and show that this resolves the
anomalous alignment of vorticity with the intermediate eigenvector of the total
strain rate tensor. We then evaluate the background strain field in DNS of
homogeneous isotropic turbulence where, even for the limited R and n
corresponding to the truncated series expansion, the results show an increase
in the expected equilibrium alignment of vorticity with the most extensional
principal axis of the background strain rate tensor.


title: Quantum algorithm for the longest common subsequence problem

abstract:
  This paper has been withdrawn by the author(s), due a crucial error on the
entanglement of $\Gamma$ registers.


title:
Strong horizontal photospheric magnetic field in a surface dynamo
  simulation

abstract:
  Observations with the Hinode spectro-polarimeter have revealed strong
horizontal internetwork magnetic fields in the quiet solar photosphere. We aim
at interpreting the observations by means of results from numerical
simulations. Radiative MHD simulations of dynamo action by near-surface
convection are analyzed with respect to the relation between vertical and
horizontal magnetic field components. The dynamo-generated fields show a clear
dominance of the horizontal field in the height range where the spectral lines
used for the observations are formed. The ratio between the averaged horizontal
and vertical field components is consistent with the values derived from the
observations. This behavior results from the intermittent nature of the dynamo
field with polarity mixing on small scales in the surface layers. Our results
provide further evidence that local near-surface dynamo action contributes
significantly to the solar internetwork fields.


title: Generative Unbinding of Names

abstract:
  This paper is concerned with the form of typed name binding used by the
FreshML family of languages. Its characteristic feature is that a name binding
is represented by an abstract (name,value)-pair that may only be deconstructed
via the generation of fresh bound names. The paper proves a new result about
what operations on names can co-exist with this construct. In FreshML the only
observation one can make of names is to test whether or not they are equal.
This restricted amount of observation was thought necessary to ensure that
there is no observable difference between alpha-equivalent name binders. Yet
from an algorithmic point of view it would be desirable to allow other
operations and relations on names, such as a total ordering. This paper shows
that, contrary to expectations, one may add not just ordering, but almost any
relation or numerical function on names without disturbing the fundamental
correctness result about this form of typed name binding (that object-level
alpha-equivalence precisely corresponds to contextual equivalence at the
programming meta-level), so long as one takes the state of dynamically created
names into account.


title:
Real Time Global Tests of the ALICE High Level Trigger Data Transport
  Framework

abstract:
  The High Level Trigger (HLT) system of the ALICE experiment is an online
event filter and trigger system designed for input bandwidths of up to 25 GB/s
at event rates of up to 1 kHz. The system is designed as a scalable PC cluster,
implementing several hundred nodes. The transport of data in the system is
handled by an object-oriented data flow framework operating on the basis of the
publisher-subscriber principle, being designed fully pipelined with lowest
processing overhead and communication latency in the cluster. In this paper, we
report the latest measurements where this framework has been operated on five
different sites over a global north-south link extending more than 10,000 km,
processing a ``real-time'' data flow.


title: Linear Logic by Levels and Bounded Time Complexity

abstract:
  We give a new characterization of elementary and deterministic polynomial
time computation in linear logic through the proofs-as-programs correspondence.
Girard's seminal results, concerning elementary and light linear logic, achieve
this characterization by enforcing a stratification principle on proofs, using
the notion of depth in proof nets. Here, we propose a more general form of
stratification, based on inducing levels in proof nets by means of indexes,
which allows us to extend Girard's systems while keeping the same complexity
properties. In particular, it turns out that Girard's systems can be recovered
by forcing depth and level to coincide. A consequence of the higher flexibility
of levels with respect to depth is the absence of boxes for handling the
paragraph modality. We use this fact to propose a variant of our polytime
system in which the paragraph modality is only allowed on atoms, and which may
thus serve as a basis for developing lambda-calculus type assignment systems
with more efficient typing algorithms than existing ones.


title: Partial conservation of seniority and nuclear isomerism

abstract:
  We point out the possibility of the {\em partial} conservation of the
seniority quantum number when most eigenstates are mixed in seniority but some
remain pure. This situation occurs in nuclei for the $g_{9/2}$ and $h_{9/2}$
shells where it is at the origin of the existence of seniority isomers in the
ruthenium and palladium isotopes. It also occurs for $f$ bosons.


title:
Isolated X-ray -- infrared sources in the region of interaction of the
  supernova remnant IC 443 with a molecular cloud

abstract:
  The nature of the extended hard X-ray source XMMU J061804.3+222732 and its
surroundings is investigated using XMM-Newton, Chandra, and Spitzer
observations. This source is located in an interaction region of the IC 443
supernova remnant with a neighboring molecular cloud. The X-ray emission
consists of a number of bright clumps embedded in an extended structured
non-thermal X-ray nebula larger than 30" in size. Some clumps show evidence for
line emission at ~1.9 keV and ~3.7 keV at the 99% confidence level. Large-scale
diffuse radio emission of IC 443 passes over the source region, with an
enhancement near the source. An IR source of about 14" x 7" size is prominent
in the 24 um, 70 um, and 2.2 um bands, adjacent to a putative Si K-shell X-ray
line emission region. The observed IR/X-ray morphology and spectra are
consistent with those expected for J/C-type shocks of different velocities
driven by fragmented supernova ejecta colliding with the dense medium of a
molecular cloud. The IR emission of the source detected by Spitzer can be
attributed to both continuum emission from an HII region created by the ejecta
fragment and line emission excited by shocks. This source region in IC 443 may
be an example of a rather numerous population of hard X-ray/IR sources created
by supernova explosions in the dense environment of star-forming regions.
Alternative Galactic and extragalactic interpretations of the observed source
are also discussed.


title:
Dynamical Dirac Mass Generation in the Supersymmetric
  Nambu--Jona-Lasinio Model with the Seesaw Mechanism of Neutrinos

abstract:
  The dynamical generation of Dirac mass in the supersymmetric
Nambu$-$Jona-Lasinio (SNJL) model with the seesaw mechanism of neutrino is
investigeted. The right and left handed Majorana mass parameters are introduced
into the SNJL model; we regard them as external model parameters. The question
on the origin of these Majorana masses are set aside, and we concentrate on the
examination of the effect of the Majorana mass parameters on the dynamical
generation of Dirac mass. The effective potential of the model and the gap
equation for the self-consistent determination of Dirac mass are derived and
solved. We use both the four-dimensional covariant and three-dimensional
non-covariant cutoff schemes for the regularizations of the effective
potential. We find there are cases of the first and second order phase
transitions with respect to variation of the coupling constant of the
Nambu$-$Jona-Lasinio-type four-body interaction of the SNJL model. In the case
of second-order phase transition, the dynamically generated Dirac mass
$|\phi_{S}|$ can arbitrarily be small compared with the right-handed Majorana
mass parameter $|M|$ and thus the seesaw condition $0<|\phi_{S}|\ll|M|$ can be
satisfied by a fine tuning of the coupling constant, while at the first-order
case it seems very difficult and/or "unnatural" to satisfy the condition. The
numerical results do not depend on the difference of the cutoff schemes
qualitatively.

categories: hep-ph cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con gr-qc hep-th


title:
Third quantization: a general method to solve master equations for
  quadratic open Fermi systems

abstract:
  The Lindblad master equation for an arbitrary quadratic system of n fermions
is solved explicitly in terms of diagonalization of a 4n x 4n matrix, provided
that all Lindblad bath operators are linear in the fermionic variables. The
method is applied to the explicit construction of non-equilibrium steady states
and the calculation of asymptotic relaxation rates in the far from equilibrium
problem of heat and spin transport in a nearest neighbor Heisenberg XY spin 1/2
chain in a transverse magnetic field.


title: Constraints to Uranus' Great Collision. IV. The Origin of Prospero

abstract:
  It is widely accepted that the large obliquity of Uranus is the result of a
great tangential collision (GC) with an Earth size proto-planet at the end of
the accretion. We attempt to constraint the GC scenario as the cause of Uranus'
obliquity as well as on the mechanisms able to give origin to the Uranian
irregulars. Different capture mechanisms for irregulars operate at different
stages on the giant planets formation process. The mechanisms able to capture
the uranian irregulars before and after the GC are analysed. Assuming that they
were captured before the GC, we calculate the orbital transfer of the nine
irregulars by the impulse imparted by the GC. If their orbital transfer results
dynamically implausible, they should have originated after the GC. We
investigate and discuss the dissipative mechanisms able to operate later. In
particular Prospero could not exist at the time of the GC. Different capture
mechanisms for Prospero after the GC are investigated. Gas drag by
Uranus'envelope and pull-down capture are not plausible mechanisms. Capture of
Prospero through a collisionless interaction seems to be difficult. The GC
itself provides a mechanism of permanent capture. However, the capture of
Prospero by the GC is a low probable event. Catastrophic collisions could be a
possible mechanism for the birth of Prospero and the other irregulars after the
GC. Orbital and physical clusterings should then be expected. Either Prospero
had to originate after the GC or the GC did not occur. In the former case, the
mechanism for the origin of Prospero after the GC remains an open question. In
the latter case, another theory to account for Uranus' obliquity and the
formation of the Uranian regular satellites on the equatorial plane of the
planet would be needed.


title:
Simultaneous multi-wavelength observations of the TeV Blazar Mrk 421
  during February - March 2003: X-ray and NIR correlated variability

abstract:
  In the present paper, we have reported the result of simultaneous
multi-wavelength observations of the TeV blazar Mrk 421 during February $-$
March 2003. In this period, we have observed Mrk 421 using Pachmarhi Array of
\v{C}erenkov Telescopes (PACT) of Tata Institute of Fundamental Research at
Pachmarhi, India. Other simultaneous data were taken from the published
literature and public data archives. We have analyzed the high quality X-ray
(2-20 keV) observations from the NASA Rossi X-Ray Timing Explorer (RXTE). We
have seen a possible correlated variability between X-ray and J band (1.25
$\mu$) near infrared (NIR) wavelength. This is the first case of X-ray and NIR
correlated variability in Mrk 421 or any high energy peaked (HBL) blazar. The
correlated variability reported here is indicating a similar origin for NIR and
X-ray emission. The emission is not affected much by the environment of the
surrounding medium around the central engine of the Mrk 421. The observations
are consistent with the shock-in-jet model for the emission of radiations.


title: Balanced routing of random calls

abstract:
  We consider an online network routing problem in continuous time, where calls
have Poisson arrivals and exponential durations. The first-fit dynamic
alternative routing algorithm sequentially selects up to $d$ random two-link
routes between the two endpoints of a call, via an intermediate node, and
assigns the call to the first route with spare capacity on each link, if there
is such a route. The balanced dynamic alternative routing algorithm
simultaneously selects $d$ random two-link routes, and the call is accepted on
a route minimising the maximum of the loads on its two links, provided neither
of these two links is saturated. We determine the capacities needed for these
algorithms to route calls successfully and find that the balanced algorithm
requires a much smaller capacity. In order to handle such interacting random
processes on networks, we develop appropriate tools such as lemmas on biased
random walks.


title: Noise effect on Grover algorithm

abstract:
  The decoherence effect on Grover algorithm has been studied numerically
through a noise modelled by a depolarizing channel. Two types of error are
introduced characterizing the qubit time evolution and gate application, so the
noise is directly related to the quantum network construction. The numerical
simulation concludes an exponential damping law for the successive probability
of the maxima as time increases. We have obtained an allowed-error law for the
algorithm: the error threshold for the allowed noise behaves as Eth(N) ~ 1/N1.1
(N being the size of the data set). As the power of N is almost one, we
consider the Grover algorithm as robust to a certain extent against
decoherence. This law also provides an absolute threshold: if the free
evolution error is greater than 0.043, Grover algorithm does not work for any
number of qubits affected by the present error model. The improvement in the
probability of success, in the case of two qubits has been illustrated by using
a fault-tolerant encoding of the initial state by means of the [[7,1,3]]
quantum code.


title: Finitely Additive Supermartingales

abstract:
  The concept of finitely additive supermartingales, originally due to Bochner,
is revived and developed. We exploit it to study measure decompositions over
filtered probability spaces and the properties of the associated
Dol\'{e}ans-Dade measure. We obtain versions of the Doob Meyer decomposition
and, as an application, we establish a version of the Bichteler and Dellacherie
theorem with no exogenous probability measure.


title: Experimental Test

abstract:
  An experiment is described that empirically distinguishes the previously
proposed q-rules governing the collapse of a wave function, and contrasts it
with the conventional idea of a collapse as well as the current leading theory
of collapse advanced by Ghirardi and Pearle. Keywords: foundation theory,
measurement, qRules, state reduction, wave collapse.


title: The Discovery of Soft X-ray Loud Broad Absorption Line Quasars

abstract:
  It is been known for more than a decade that BALQSOs (broad absorption line
quasars) are highly attenuated in the X-ray regime compared to other quasars,
especially in the soft band ($< $ 1 keV). Using X-ray selection techniques we
have found "soft X-ray loud" BALQSOs that, by definition, have soft X-ray (0.3
keV) to UV ($3000 \AA$) flux density ratios that are higher than typical nonBAL
radio quiet quasars. Our sample of 3 sources includes one LoBALQSO (low
ionization BALQSO) which are generally considered to be the most highly
attenuated in the X-rays. The three QSOs are the only known BALQSOs that have
X-ray observations that are consistent with no intrinsic soft X-ray absorption.
The existence of a large X-ray luminosity and the hard ionizing continuum that
it presents to potential UV absorption gas is in conflict with the ionization
states that are conducive to line driving forces within BAL winds (especially
for the LoBALs).


title: Exchangeable lower previsions

abstract:
  We extend de Finetti's (1937) notion of exchangeability to finite and
countable sequences of variables, when a subject's beliefs about them are
modelled using coherent lower previsions rather than (linear) previsions. We
prove representation theorems in both the finite and the countable case, in
terms of sampling without and with replacement, respectively. We also establish
a convergence result for sample means of exchangeable sequences. Finally, we
study and solve the problem of exchangeable natural extension: how to find the
most conservative (point-wise smallest) coherent and exchangeable lower
prevision that dominates a given lower prevision.


title:
Charge transfer and coherence dynamics of tunnelling system coupled to a
  harmonic oscillator

abstract:
  We study the transition probability and coherence of a two-site system,
interacting with an oscillator. Both properties depend on the initial
preparation. The oscillator is prepared in a thermal state and, even though it
cannot be considered as an extended bath, it produces decoherence because of
the large number of states involved in the dynamics. In the case in which the
oscillator is intially displaced a coherent dynamics of change entangled with
oscillator modes takes place. Coherency is however degraded as far as the
oscillator mass increases producing a increasingly large recoherence time.
Calculations are carried on by exact diagonalization and compared with two
semiclassical approximations. The role of the quantum effects are highlighted
in the long-time dynamics, where semiclassical approaches give rise to a
dissipative behaviour. Moreover, we find that the oscillator dynamics has to be
taken into account, even in a semiclassical approximation, in order to
reproduce a thermally activated enhancement of the transition probability.


title:
Surface plasmon polariton modes in a single-crystal Au nanoresonator
  fabricated using focused-ion-beam milling

abstract:
  We use focused-ion-beam milling of a single-crystal Au surface to fabricate a
590-nm-long linear ridge that acts as a surface plasmon nanoresonator.
Cathodoluminescence imaging spectroscopy is then used to excite and image
surface plasmons on the ridge. Principal component analysis reveals distinct
plasmonic modes, which proves confinement of surface-plasmon oscillations to
the ridge. Boundary-element-method calculations confirm that a linear ridge is
able to support highly-localized surface-plasmon modes (mode diameter < 100
nm). The results demonstrate that focused-ion-beam milling can be used in rapid
prototyping of nanoscale single-crystal plasmonic components.


title: Transport in quasi one-dimensional spin-1/2 systems

abstract:
  We present numerical results for the spin and thermal conductivity of
one-dimensional (1D) quantum spin systems. We contrast the properties of
integrable models such as the spin-1/2 XXZ chain against nonintegrable ones
such as frustrated and dimerized chains. The thermal conductivity of the XXZ
chain is ballistic at finite temperatures, while in the nonintegrable models,
this quantity is argued to vanish. For the case of frustrated and dimerized
chains, we discuss the frequency dependence of the transport coefficients.
Finally, we give an overview over related theoretical work on intrinsic and
extrinsic scattering mechanisms of quasi-1D spin systems.


title:
Plasmon Annihilation into Kaluza-Klein Graviton: New Astrophysical
  Constraints on Large Extra Dimensions

abstract:
  In large extra dimensional Kaluza-Klein (KK) scenario, where the usual
Standard Model (SM) matter is confined to a 3+1-dimensional hypersurface called
the 3-brane and gravity can propagate to the bulk (D=4+d, d being the number of
extra spatial dimensions), the light graviton KK modes can be produced inside
the supernova core due to the usual nucleon-nucleon bremstrahlung,
electron-positron and photon-photon annihilations. This photon inside the
supernova becomes plasmon due to the plasma effect. In this paper, we study the
energy-loss rate of SN 1987A due to the KK gravitons produced from the
plasmon-plasmon annihilation. We find that the SN 1987A cooling rate leads to
the conservative bound $M\_D$ > 22.9 TeV and 1.38 TeV for the case of two and
three space-like extra dimensions.


title: Limits to the sensitivity of a low noise compact atomic gravimeter

abstract:
  A detailed analysis of the most relevant sources of phase noise in an atomic
interferometer is carried out, both theoretically and experimentally. Even a
short interrogation time of 100 ms allows our cold atom gravimeter to reach an
excellent short term sensitivity to acceleration of $1.4\times 10^{-8}$g at 1s.
This result relies on the combination of a low phase noise laser system,
efficient detection scheme and good shielding from vibrations. In particular,
we describe a simple and robust technique of vibration compensation, which is
based on correcting the interferometer signal by using the AC acceleration
signal measured by a low noise seismometer.


title: On the remainder in the Taylor theorem

abstract:
  We give a short straightforward proof for the bound of the reminder term in
the Taylor theorem. The proof uses only induction and the fact that $f'\geq 0$
implies the monotonicity of $f$, so it might be an attractive proof to give to
undergraduate students.


title:
Spurious source generation in mapping from noisy phase-self-calibrated
  data

abstract:
  Phase self-calibration (or selfcal) is an algorithm often used in the
calibration of interferometric observations in astronomy. Although a powerful
tool, this algorithm presents strong limitations when applied to data with a
low signal-to-noise ratio. We analyze the artifacts that the phase selfcal
algorithm produces when applied to extremely noisy data. We show how the phase
selfcal may generate a spurious source in the sky from a distribution of
completely random visibilities. This spurious source is indistinguishable from
a real one. We numerically and analytically compute the relationship between
the maximum spurious flux density generated by selfcal from noise and the
particulars of the interferometric observations. Finally, we present two simple
tests that can be applied to interferometric data for checking whether a source
detection is real or whether the source is an artifact of the phase
self-calibration algorithm.


title: X-Ray Propagation in Tapered Waveguides: Simulation and Optimization

abstract:
  We use the parabolic wave equation to study the propagation of x-rays in
tapered waveguides by numercial simulation and optimization. The goal of the
study is to elucidate how beam concentration can be best achieved in x-ray
optical nanostructures. Such optimized waveguides can e.g. be used to
investigate single biomolecules. Here, we compare tapering geometries, which
can be parametrized by linear and third-order (Bezier-type) functions and can
be fabricated using standard e-beam litography units. These geometries can be
described in two and four-dimensional parameter spaces, respectively. In both
geometries, we observe a rugged structure of the optimization problem's ``gain
landscape''. Thus, the optimization of x-ray nanostructures in general will be
a highly nontrivial optimization problem.


title: Wilson loop and magnetic monopole through a non-Abelian Stokes theorem

abstract:
  We show that the Wilson loop operator for SU(N) Yang-Mills gauge connection
is exactly rewritten in terms of conserved gauge-invariant magnetic and
electric currents through a non-Abelian Stokes theorem of the Diakonov-Petrov
type. Here the magnetic current originates from the magnetic monopole derived
in the gauge-invariant way from the pure Yang--Mills theory even in the absence
of the Higgs scalar field, in sharp contrast to the 't Hooft-Polyakov magnetic
monopole in the Georgi-Glashow gauge-Higgs model. The resulting representation
indicates that the Wilson loop operator in fundamental representations can be a
probe for a single magnetic monopole irrespective of $N$ in SU(N) Yang-Mills
theory, against the conventional wisdom. Moreover, we show that the
quantization condition for the magnetic charge follows from the fact that the
non-Abelian Stokes theorem does not depend on the surface chosen for writing
the surface integral. The obtained geometrical and topological representations
of the Wilson loop operator have important implications to understanding quark
confinement according to the dual superconductor picture.


title: Le terme et le concept : fondements d'une ontoterminologie

abstract:
  Most definitions of ontology, viewed as a "specification of a
conceptualization", agree on the fact that if an ontology can take different
forms, it necessarily includes a vocabulary of terms and some specification of
their meaning in relation to the domain's conceptualization. And as domain
knowledge is mainly conveyed through scientific and technical texts, we can
hope to extract some useful information from them for building ontology. But is
it as simple as this? In this article we shall see that the lexical structure,
i.e. the network of words linked by linguistic relationships, does not
necessarily match the domain conceptualization. We have to bear in mind that
writing documents is the concern of textual linguistics, of which one of the
principles is the incompleteness of text, whereas building ontology - viewed as
task-independent knowledge - is concerned with conceptualization based on
formal and not natural languages. Nevertheless, the famous Sapir and Whorf
hypothesis, concerning the interdependence of thought and language, is also
applicable to formal languages. This means that the way an ontology is built
and a concept is defined depends directly on the formal language which is used;
and the results will not be the same. The introduction of the notion of
ontoterminology allows to take into account epistemological principles for
formal ontology building.


title: On the guaranteed error correction capability of LDPC codes

abstract:
  We investigate the relation between the girth and the guaranteed error
correction capability of $\gamma$-left regular LDPC codes when decoded using
the bit flipping (serial and parallel) algorithms. A lower bound on the number
of variable nodes which expand by a factor of at least $3 \gamma/4$ is found
based on the Moore bound. An upper bound on the guaranteed correction
capability is established by studying the sizes of smallest possible trapping
sets.


title: On asymptotic stability in energy space of ground states of NLS in 2D

abstract:
  We transpose work by K.Yajima and by T.Mizumachi to prove dispersive and
smoothing estimates for dispersive solutions of the linearization at a ground
state of a Nonlinear Schr\"odinger equation (NLS) in 2D. As an application we
extend to dimension 2D a result on asymptotic stability of ground states of NLS
proved in the literature for all dimensions different from 2.


title: Random walks on complex trees

abstract:
  We study the properties of random walks on complex trees. We observe that the
absence of loops reflects in physical observables showing large differences
with respect to their looped counterparts. First, both the vertex discovery
rate and the mean topological displacement from the origin present a
considerable slowing down in the tree case. Second, the mean first passage time
(MFPT) displays a logarithmic degree dependence, in contrast to the inverse
degree shape exhibited in looped networks. This deviation can be ascribed to
the dominance of source-target topological distance in trees. To show this, we
study the distance dependence of a symmetrized MFPT and derive its logarithmic
profile, obtaining good agreement with simulation results. These unique
properties shed light on the recently reported anomalies observed in diffusive
dynamical systems on trees.


title:
Cataclysmic Variables in Globular Clusters, the Galactic Center, and
  Local Space

abstract:
  We compare the X-ray spectra and luminosities, in the 2-8 keV band, of known
and suspected cataclysmic variables (CVs) in different environments, assessing
the nature of these source populations. These objects include nearby CVs
observed with ASCA; the Galactic Center X-ray source population identified by
Muno et al.; and likely CVs identified in globular clusters. Both of the latter
have been suggested to be dominated by magnetic CVs. We find that the brighter
objects in both categories are likely to be magnetic CVs, but that the fainter
objects are likely to include a substantial contribution from normal CVs. The
strangely hard spectra observed from the Galactic Center sources reflect the
high and variable extinction, which is significantly greater than the canonical
6e22 /cm2 over much of the region, and the magnetic nature of many of the
brightest CVs. The total numbers of faint Galactic Center sources are
compatible with expectations of the numbers of CVs in this field.


title: LR-algebras

abstract:
  In the study of NIL-affine actions on nilpotent Lie groups we introduced so
called LR-structures on Lie algebras. The aim of this paper is to consider the
existence question of LR-structures, and to start a structure theory of
LR-algebras. We show that any Lie algebra admitting an LR-structure is 2-step
solvable. Conversely we find several classes of 2-step solvable Lie algebras
admitting an LR-structure, but also classes not admitting such a structure. We
study also ideals in LR-algebras, and classify low-dimensional real
LR-algebras.


title:
Quantum oscillations and the Fermi surface in an underdoped high-Tc
  superconductor

abstract:
  Despite twenty years of research, the phase diagram of high transition-
temperature superconductors remains enigmatic. A central issue is the origin of
the differences in the physical properties of these copper oxides doped to
opposite sides of the superconducting region. In the overdoped regime, the
material behaves as a reasonably conventional metal, with a large Fermi
surface. The underdoped regime, however, is highly anomalous and appears to
have no coherent Fermi surface, but only disconnected "Fermi arcs". The
fundamental question, then, is whether underdoped copper oxides have a Fermi
surface, and if so, whether it is topologically different from that seen in the
overdoped regime. Here we report the observation of quantum oscillations in the
electrical resistance of the oxygen-ordered copper oxide YBa2Cu3O6.5,
establishing the existence of a well-defined Fermi surface in the ground state
of underdoped copper oxides, once superconductivity is suppressed by a magnetic
field. The low oscillation frequency reveals a Fermi surface made of small
pockets, in contrast to the large cylinder characteristic of the overdoped
regime. Two possible interpretations are discussed: either a small pocket is
part of the band structure specific to YBa2Cu3O6.5 or small pockets arise from
a topological change at a critical point in the phase diagram. Our
understanding of high-transition temperature (high-Tc) superconductors will
depend critically on which of these two interpretations proves to be correct.


title: LDPC Codes Which Can Correct Three Errors Under Iterative Decoding

abstract:
  In this paper, we provide necessary and sufficient conditions for a
column-weight-three LDPC code to correct three errors when decoded using
Gallager A algorithm. We then provide a construction technique which results in
a code satisfying the above conditions. We also provide numerical assessment of
code performance via simulation results.


title:
Possible resolution of the Casimir force finite temperature correction
  "controversies"

abstract:
  By considering the effect of diffusion on the external electric field
response of charge carriers in metals and semiconductors, it is shown that the
finite temperature correction proposed Bostrom and Sernelius requires
substantial modification, and there is no large correction as suggested for
good conductors. The apparent violation of the Third Law of Thermodynamics of
the various proposed temperature corrections to the Casimir force is also
resolved. Finally, the effect of Debye screening on electrostatic calibrations
between pure germanium surfaces is calculated


title: Fuzzy Scalar Field Theories: Numerical and Analytical Investigations

abstract:
  This thesis is devoted to the study of Quantum Field Theories (QFT) on fuzzy
spaces. Fuzzy spaces are approximations to the algebra of functions of a
continuous space by a finite matrix algebra. In the limit of infinitely large
matrices the formulation is exact. An attractive feature of this approach is
that it transparently shows how the geometrical properties of the continuous
space are preserved. In the study of the non-perturbative regime of QFT, fuzzy
spaces provide a possible alternative to the lattice as a regularisation
method. The thesis is divided into two parts. We perform Monte Carlo
simulations of a $\lambda \phi^4$ theory on a 3-dimensional Euclidean space. We
identify the phase diagram of this model. In addition to the usual disordered
and uniform ordered phases we find a third phase of non-uniform ordering. This
indicates the existence of the phenomenon called UV-IR mixing in the strong
coupling regime. Second we present a geometrical analysis of the scalar field
theory on a 4-dimensional fuzzy sphere, S4_F. Nevertheless a fuzzy version of
S4 cannot be achieved by quantisation of the classical space. The problem is
circumvented by defining a scalar theory on a larger space, CP3 which is
6-dimensional. It includes degrees of freedom related to S^4 plus others beyond
S4. Those extra degrees of freedom are dynamically suppressed through a
probabilistic method. The analysis of the geometrical structures allows us to
interpret this procedure as a Kaluza-Klein reduction of CP3 to S4.


title:
Nano granular metallic Fe - oxygen deficient TiO$_{2-\delta}$ composite
  films: A room temperature, highly carrier polarized magnetic semiconductor

abstract:
  Nano granular metallic iron (Fe) and titanium dioxide (TiO$_{2-\delta}$) were
co-deposited on (100) lanthanum aluminate (LaAlO$_3$) substrates in a low
oxygen chamber pressure using a pulsed laser ablation deposition (PLD)
technique. The co-deposition of Fe and TiO$_2$ resulted in $\approx$ 10 nm
metallic Fe spherical grains suspended within a TiO$_{2-\delta}$ matrix. The
films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss
at room temperature. Our estimate of the saturation magnetization based on the
size and distribution of the Fe spheres agreed well with the measured value.
The film composite structure was characterized as p-type magnetic semiconductor
at 300 K with a carrier density of the order of $ 10^{22} /{\rm cm^3}$. The
hole carriers were excited at the interface between the nano granular Fe and
TiO$_{2-\delta}$ matrix similar to holes excited in the metal/n-type
semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS)
devices. From the large anomalous Hall effect directly observed in these films
it follows that the holes at the interface were strongly spin polarized.
Structure and magneto transport properties suggested that these PLD films have
potential nano spintronics applications.


title: Hot QCD equations of state and response functions for quark-gluon plasma

abstract:
  We study the response functions (chromo-electric susceptibilities) of
quark-gluon plasma as a function of temperature in the presence of
interactions. We consider two equations of state for hot QCD. The first one is
fully perturbative, of $O(g^5)$ EOS and, and the second one which is
$O[g^6\ln(1/g)+\delta]$, incorporates some non-perturbative effects. Following
a recent work (Physical Review {\bf C 76}, 054909(2007)), the interaction
effects contained in the EOS are encapsulated in terms of effective chemical
potentials($\tilde\mu$) in the equilibrium distribution functions for the
partons.By using them in another recent formulation of the response
functions({\tt arXiv:0707.3697}), we determine explicitly the chromo-electric
susceptibilities for QCD plasma. We find that it shows large deviations from
the ideal behavior. We further study the modification in the heavy quark
potential due to the medium effects. In particular, we determine the
temperature dependence of the screening lengths by fixing the effective
coupling constant $Q$ which appears in the transport equation by comparing the
screening in the present formalism with exact lattice QCD results. Finally, we
study the dissociation phenomena of heavy quarkonium states such as $c\bar{c}$
and $b\bar{b}$, and determine the dissociation temperatures. Our results are in
good agreement with recent lattice results.


title: Power of Black Hole Physics: Seeing through the Vacuum Landscape

abstract:
  In this paper we generalize the black hole bound of arXiv:0706.2050 to de
Sitter spaces, and apply it to various vacua in the landscape, with a special
emphasis on slow-roll inflationary vacua. Non-trivial constraints on the
lifetime and the Hubble expansion rate emerge. For example, the general
tendency is, that for the fixed number and the increasing mass of the species,
vacua must become more curved and more unstable, either classically or quantum
mechanically. We also discuss the constraints on the lifetime of vacua in the
landscape, due to decay into the neighboring states.


title: GIT stability of weighted pointed curves

abstract:
  Here I give a direct proof that smooth curves with distinct marked points are
asymptotically Hilbert stable with respect to a wide range of parameter spaces
and linearizations. This result can be used to construct the coarse moduli
space of Deligne-Mumford stable pointed curves \bar M_g,n and Hassett's moduli
spaces of weighted pointed curves \bar M_g,A (though the full construction of
the moduli spaces is not contained in this paper, only the stability proof). My
proof follows Gieseker's approach to reduce to the GIT problem to a
combinatorial problem, though the solution is very different. The action of any
1-PS lambda on a curve C in P^N gives rise to weighted filtrations of H^0 (C,
O(1)) and H^0 (C, O(m)), and I give a recipe in terms of the combinatorics of
the base loci of the stages of these filtrations for showing that C is stable
with respect to lambda.


title:
Radial components, prehomogeneous vector spaces, and rational Cherednik
  algebras

abstract:
  Let V be a finite dimensional representation of the connected complex
reductive group H. Denote by G the derived subgroup of H and assume that the
categorical quotient of V by G is one dimensional. In this situation there
exists a homomorphism, denoted by rad, from the algebra A of G-invariant
differential operators on V to the first Weyl algebra. We show that the image
of rad is isomorphic to the spherical subalgebra of a Cherednik algebra, whose
parameters are determined by the b-function of the relative invariant
associated to the prehomogeneous vector space (H : V). If (H : V) is furthemore
assumed to be multiplicity free we obtain a Howe duality between a set of
representations of G and modules over a subalgebra of the associative Lie
algebra A. Some applications to holonomic modules and H-equivariant D-modules
on V are also given.


title: Effective Hamiltonian for a half-filled tetramerized ionic-Hubbard chain

abstract:
  We derive an effective spin Hamiltonian for the one-dimensional half-filled
tetramerized ionic-Hubbard model in the limit of strong on-site repulsion. We
show that the effective Hamiltonian which describes the low-energy spin sector
of the model is a spin S=1/2 Heisenberg Hamiltonian with alternating
nearest-neighbour exchange.


title: Chirality-induced Dynamic Kohn Anomalies in Graphene

abstract:
  We develop a theory for the renormalization of the phonon energy dispersion
in graphene due to the combined effects of both Coulomb and electron-phonon
(e-ph) interactions. We obtain the renormalized phonon energy spectrum by an
exact analytic derivation of the phonon self-energy, finding three distinct
Kohn anomalies (KAs) at the phonon wavevector $q = \omega/v, 2k_F\pm\omega/v$
for LO phonons and one at $q = \omega/v$ for TO phonons. The presence of these
new KAs in graphene, in contrast to the usual KA $q = 2k_F$ in ordinary metals,
originates from the dynamical screening of e-ph interaction (with a concomitant
breakdown of the Born-Oppenheimer approximation) and the peculiar chirality of
the graphene e-ph coupling.


title: Geometric information in eight dimensions vs. quantum information

abstract:
  Complementary idempotent paravectors and their ordered compositions, are used
to represent multivector basis elements of geometric Clifford algebra for 3D
Euclidean space as the states of a geometric byte in a given frame of
reference. Two layers of information, available in real numbers, are
distinguished. The first layer is a continuous one. It is used to identify
spatial orientations of similar geometric objects in the same computational
basis. The second layer is a binary one. It is used to manipulate with 8D
structure elements inside the computational basis itself. An oriented unit cube
representation, rather than a matrix one, is used to visualize an inner
structure of basis multivectors. Both layers of information are used to
describe unitary operations -- reflections and rotations -- in Euclidian and
Hilbert spaces. The results are compared with ones for quantum gates. Some
consequences for quantum and classical information technologies are discussed.


title: The ESO Large Programme First Stars

abstract:
  In ESO period 65 (April-September 2000) the large programme 165.N-0276, led
by Roger Cayrel, began making use of UVES at the Kueyen VLT telescope. Known
within the Team and outside as ``First Stars'', it was aimed at obtaining high
resolution, high signal-to-noise ratio spectra in the range 320 nm -- 1000 nm
for a large sample of extremely metal-poor (EMP) stars identified from the HK
objective prism survey.In this contribution we highlight the main results of
the large programme.


title: Gauged Supergravities, Tensor Hierarchies, and M-Theory

abstract:
  Deformations of maximal supergravity theories induced by gauging non-abelian
subgroups of the duality group reveal the presence of charged M-theory degrees
of freedom that are not necessarily contained in supergravity. The relation
with M-theory degrees of freedom is confirmed by the representation assignments
under the duality group of the gauge charges and the ensuing vector and tensor
gauge fields. The underlying hierarchy of these gauge fields is required for
consistency of general gaugings. As an example gauged maximal supergravity in
three space-time dimensions is presented in a version where all possible tensor
fields appear.


title: The structure of weak shocks in quantum plasmas

abstract:
  The structure of a weak shock in a quantum plasma is studied, taking into
account both dissipation terms due to thermal conduction and dispersive quantum
terms due to the Bohm potential. Unlike quantum systems without dissipations,
even a small thermal conduction may lead to a stationary shock structure. In
the limit of zero quantum effects, the monotonic Burgers solution for the weak
shock is recovered. Still, even small quantum terms make the structure
non-monotonic with the shock driving a train of oscillations into the initial
plasma. The oscillations propagate together with the shock. The oscillations
become stronger as the role of Bohm potential increases in comparison with
thermal conduction. The results could be of importance for laser-plasma
interactions, such as inertial confinement fusion plasmas, and in astrophysical
environments, as well as in condensed matter systems.


title:
Gene regulation in continuous cultures: A unified theory for bacteria
  and yeasts

abstract:
  During batch growth on mixtures of two growth-limiting substrates, microbes
consume the substrates either sequentially or simultaneously. These growth
patterns are manifested in all types of bacteria and yeasts. The ubiquity of
these growth patterns suggests that they are driven by a universal mechanism
common to all microbial species. In previous work, we showed that a minimal
model accounting only for enzyme induction and dilution explains the phenotypes
observed in batch cultures of various wild-type and mutant/recombinant cells.
Here, we examine the extension of the minimal model to continuous cultures. We
show that: (1) Several enzymatic trends, usually attributed to specific
regulatory mechanisms such as catabolite repression, are completely accounted
for by dilution. (2) The bifurcation diagram of the minimal model for
continuous cultures, which classifies the substrate consumption pattern at any
given dilution rate and feed concentrations, provides a a precise explanation
for the empirically observed correlation between the growth patterns in batch
and continuous cultures. (3) Numerical simulations of the model are in
excellent agreement with the data. The model captures the variation of the
steady state substrate concentrations, cell densities, and enzyme levels during
the single- and mixed-substrate growth of bacteria and yeasts at various
dilution rates and feed concentrations. (4) This variation is well-approximated
by simple analytical expressions that furnish physical insights into the steady
states of continuous cultures. The minimal model provides a framework for
quantitating the effect of regulatory mechanisms. We illustrate this by
analyzing several data sets from the literature.


title: Supersymmetric Barotropic FRW Model and Dark Energy

abstract:
  Using the superfield approach we construct the $n=2$ supersymmetric
lagrangian for the FRW Universe with barotropic perfect fluid as matter field.
The obtained supersymmetric algebra allowed us to take the square root of the
Wheeler-DeWitt equation and solve the corresponding quantum constraint. This
model leads to the relation between the vacuum energy density and the energy
density of the dust matter.


title:
Time Variation in G24.78+0.08 A1: Evidence for an Accreting Hypercompact
  H II Region?

abstract:
  Over a timescale of a few years, an observed change in the optically thick
radio continuum flux can indicate whether an unresolved H II region around a
newly formed massive star is changing in size. In this Letter we report on a
study of archival VLA observations of the hypercompact H II region G24.78+0.08
A1 that shows a decrease of ~ 45 % in the 6-cm flux over a five year period.
Such a decrease indicates a contraction of ~ 25 % in the ionized radius and
could be caused by an increase in the ionized gas density if the size of the H
II region is determined by a balance between photoionization and recombination.
This finding is not compatible with continuous expansion of the H II region
after the end of accretion onto the ionizing star, but is consistent with the
hypothesis of gravitational trapping and ionized accretion flows if the
mass-accretion rate is not steady.


title: Isospin-breaking two-nucleon force with explicit Delta-excitations

abstract:
  We study the leading isospin-breaking contributions to the two-nucleon
two-pion exchange potential due to explicit Delta degrees of freedom in chiral
effective field theory. In particular, we find important contributions due to
the delta mass splittings to the charge symmetry breaking potential that act
opposite to the effects induced by the nucleon mass splitting.


title: Almost 2-SAT is Fixed-Parameter Tractable

abstract:
  We consider the following problem. Given a 2-CNF formula, is it possible to
remove at most $k$ clauses so that the resulting 2-CNF formula is satisfiable?
This problem is known to different research communities in Theoretical Computer
Science under the names 'Almost 2-SAT', 'All-but-$k$ 2-SAT', '2-CNF deletion',
'2-SAT deletion'. The status of fixed-parameter tractability of this problem is
a long-standing open question in the area of Parameterized Complexity. We
resolve this open question by proposing an algorithm which solves this problem
in $O(15^k*k*m^3)$ and thus we show that this problem is fixed-parameter
tractable.


title: Quantized amplitudes in a nonlinear resonant electrical circuit

abstract:
  We present a simple nonlinear resonant analog circuit which demonstrates
quantization of resonating amplitudes, for a given excitation level. The system
is a simple RLC resonator where C is an active capacitor whose value is related
to the current in the circuit. This variation is energetically equivalent to a
variation of the potential energy and the circuit acts as a pendulum in the
gravitational field. The excitation voltage, synchronously switched at the
current frequency, enables electrical supply and keeping the oscillation of the
system. The excitation frequency has been set to high harmonic of the
fundamental oscillation so that anisochronicity can keep constant the amplitude
of the circuit voltage and current. The behavior of the circuit is unusual:
different stable amplitudes have been measured depending on initial conditions
and excitation frequency, for the same amplitude of the excitation. The
excitation frequency is naturally divided by the circuit and the ratio is kept
constant without external disturbance. Moreover, a variation of the dumping
does not affect significantly the amplitudes as long as the oscillation is
observed. And lastly, electrical pulses can change, as in quantum systems, the
operating amplitude which is auto-stable without disturbances. Many
applications of this circuit can be imagined in microelectronics (including
computing), energy conversion and time and frequency domains.


title:
Automated Reconstruction of Particle Cascades in High Energy Physics
  Experiments

abstract:
  We present a procedure for reconstructing particle cascades from event data
measured in a high energy physics experiment. For evaluating the hypothesis of
a specific physics process causing the observed data, all possible
reconstruction versions of the scattering process are constructed from the
final state objects. We describe the procedure as well as examples of physics
processes of different complexity studied at hadron-hadron colliders. We
estimate the performance by 20 microseconds per reconstructed decay vertex, and
0.6 kByte per reconstructed particle in the decay trees.


title: Magnetic excitations in SrCu2O3: a Raman scattering study

abstract:
  We investigated temperature dependent Raman spectra of the one-dimensional
spin-ladder compound SrCu2O3. At low temperatures a two-magnon peak is
identified at 3160+/-10 cm^(-1) and its temperature dependence analyzed in
terms of a thermal expansion model. We find that the two-magnon peak position
must include a cyclic ring exchange of J_cycl/J_perp=0.09-0.25 with a coupling
constant along the rungs of J_perp approx. 1215 cm^(-1) (1750 K) in order to be
consistent with other experiments and theoretical results.


title:
Spin-dependent transition rates through exchange coupled localized spin
  pairs during coherent spin excitation

abstract:
  The effect of exchange interactions within spin pairs on spin-dependent
transport and recombination rates through localized states in semiconductors
during coherent electron spin resonant excitation is studied theoretically. It
is shown that for identical spin systems, significant quantitative differences
are to be expected between the results of pEDMR/pODMR experiments were
permutation symmetry is the observable as compared to pESR experiments with
polarization as the observable. It is predicted that beat oscillations of the
spin nutations and not the nutations themselves dominate the transport or
recombination rates when the exchange coupling strength or the field strength
of the exciting radiation exceed the difference of the Zeeman energies within
the spin pair. Furthermore, while the intensities of the rate oscillations
decrease with increasing exchange within the spin pairs, the singlet and
triplet signals retain their relative strength. This means that pEDMR and pODMR
experiments could allow better experimental access to ESR forbidden singlet
transitions which are hardly or not at all accessible with conventional pulsed
electron spin resonance spectroscopy.


title: Scaling laws for the decay of multiqubit entanglement

abstract:
  We investigate the decay of entanglement of generalized N-particle
Greenberger-Horne-Zeilinger (GHZ) states interacting with independent
reservoirs. Scaling laws for the decay of entanglement and for its finite-time
extinction (sudden death) are derived for different types of reservoirs. The
latter is found to increase with the number of particles. However, entanglement
becomes arbitrarily small, and therefore useless as a resource, much before it
completely disappears, around a time which is inversely proportional to the
number of particles. We also show that the decay of multi-particle GHZ states
can generate bound entangled states.


title: Capacity Bounds for the Gaussian Interference Channel

abstract:
  The capacity region of the two-user Gaussian Interference Channel (IC) is
studied. Three classes of channels are considered: weak, one-sided, and mixed
Gaussian IC. For the weak Gaussian IC, a new outer bound on the capacity region
is obtained that outperforms previously known outer bounds. The sum capacity
for a certain range of channel parameters is derived. For this range, it is
proved that using Gaussian codebooks and treating interference as noise is
optimal. It is shown that when Gaussian codebooks are used, the full
Han-Kobayashi achievable rate region can be obtained by using the naive
Han-Kobayashi achievable scheme over three frequency bands (equivalently, three
subspaces). For the one-sided Gaussian IC, an alternative proof for the Sato's
outer bound is presented. We derive the full Han-Kobayashi achievable rate
region when Gaussian codebooks are utilized. For the mixed Gaussian IC, a new
outer bound is obtained that outperforms previously known outer bounds. For
this case, the sum capacity for the entire range of channel parameters is
derived. It is proved that the full Han-Kobayashi achievable rate region using
Gaussian codebooks is equivalent to that of the one-sided Gaussian IC for a
particular range of channel parameters.


title: Alternating Hierarchies for Time-Space Tradeoffs

abstract:
  Nepomnjascii's Theorem states that for all 0 <= \epsilon < 1 and k > 0 the
class of languages recognized in nondeterministic time n^k and space
n^\epsilon, NTISP[n^k, n^\epsilon ], is contained in the linear time hierarchy.
By considering restrictions on the size of the universal quantifiers in the
linear time hierarchy, this paper refines Nepomnjascii's result to give a sub-
hierarchy, Eu-LinH, of the linear time hierarchy that is contained in NP and
which contains NTISP[n^k, n^\epsilon ]. Hence, Eu-LinH contains NL and SC. This
paper investigates basic structural properties of Eu-LinH. Then the
relationships between Eu-LinH and the classes NL, SC, and NP are considered to
see if they can shed light on the NL = NP or SC = NP questions. Finally, a new
hierarchy, zeta -LinH, is defined to reduce the space requirements needed for
the upper bound on Eu-LinH.


title:
Strict convexity of the free energy for non-convex gradient models at
  moderate $\beta$

abstract:
  We consider a gradient interface model on the lattice with interaction
potential which is a non-convex perturbation of a convex potential. We show
using a one-step multiple scale analysis the strict convexity of the surface
tension at high temperature. This is an extension of Funaki and Spohn's result,
where the strict convexity of potential was crucial in their proof that for
every tilt there is a unique, shift invariant, ergodic Gibbs measure for the
$\nabla\phi$ field.


title: Game-theoretic Brownian motion

abstract:
  This paper suggests a perfect-information game, along the lines of Levy's
characterization of Brownian motion, that formalizes the process of Brownian
motion in game-theoretic probability. This is perhaps the simplest situation
where probability emerges in a non-stochastic environment.


title:
Discontinuous condensation transition and nonequivalence of ensembles in
  a zero-range process

abstract:
  We study a zero-range process where the jump rates do not only depend on the
local particle configuration, but also on the size of the system. Rigorous
results on the equivalence of ensembles are presented, characterizing the
occurrence of a condensation transition. In contrast to previous results, the
phase transition is discontinuous and the system exhibits ergodicity breaking
and metastable phases. This leads to a richer phase diagram, including
nonequivalence of ensembles in certain phase regions. The paper is motivated by
results from granular clustering, where these features have been observed
experimentally.


title: On a representation of the inverse Fq transform

abstract:
  A recent generalization of the Central Limit Theorem consistent with
nonextensive statistical mechanics has been recently achieved through a
generalized Fourier transform, noted $q$-Fourier transform. A representation
formula for the inverse $q$-Fourier transform is here obtained in the class of
functions $\mathcal{G}=\bigcup_{1\le q<3}\mathcal{G}_q,$ where
$\mathcal{G}_{q}=\{f = a e_{q}^{-\beta x2}, \, a>0, \, \beta>0 \}$. This
constitutes a first step towards a general representation of the inverse
$q$-Fourier operation, which would enable interesting physical and other
applications.


title:
A New Integrable Model of (1+1)-Dimensional Dilaton Gravity Coupled to
  Toda Matter

abstract:
  A new class of integrable two-dimensional dilaton gravity theories, in which
scalar matter fields satisfy the Toda equations, is proposed. The simplest case
of the Toda system is considered in some detail, and on this example we outline
how the general solution can be obtained. Then we demonstrate how the wave-like
solutions of the general Toda systems can be simply derived. In the dilaton
gravity theory this solutions describe nonlinear waves coupled to gravity. A
special attention is paid to making the analytic structure of the solutions of
the Toda equations as simple and transparent as possible, with the aim to apply
the idea of the separation of variables to non-integrable theories.


title: N=4 SYM on K3 and the AdS(3)/CFT(2) Correspondence

abstract:
  We study the Fareytail expansion of the topological partition function of N=4
SU(N) super Yang-Mills theory on K3. We argue that this expansion corresponds
to a sum over geometries in asymptotically AdS_3 spacetime, which is
holographically dual to a large number of coincident fundamental heterotic
strings.


title:
Modeling Heterogeneous Materials via Two-Point Correlation Functions:
  II. Algorithmic Details and Applications

abstract:
  In the first part of this series of two papers, we proposed a theoretical
formalism that enables one to model and categorize heterogeneous materials
(media) via two-point correlation functions S2 and introduced an efficient
heterogeneous-medium (re)construction algorithm called the "lattice-point"
algorithm. Here we discuss the algorithmic details of the lattice-point
procedure and an algorithm modification using surface optimization to further
speed up the (re)construction process. The importance of the error tolerance,
which indicates to what accuracy the media are (re)constructed, is also
emphasized and discussed. We apply the algorithm to generate three-dimensional
digitized realizations of a Fontainebleau sandstone and a boron
carbide/aluminum composite from the two- dimensional tomographic images of
their slices through the materials. To ascertain whether the information
contained in S2 is sufficient to capture the salient structural features, we
compute the two-point cluster functions of the media, which are superior
signatures of the micro-structure because they incorporate the connectedness
information. We also study the reconstruction of a binary laser-speckle pattern
in two dimensions, in which the algorithm fails to reproduce the pattern
accurately. We conclude that in general reconstructions using S2 only work well
for heterogeneous materials with single-scale structures. However, two-point
information via S2 is not sufficient to accurately model multi-scale media.
Moreover, we construct realizations of hypothetical materials with desired
structural characteristics obtained by manipulating their two-point correlation
functions.


title: Emergence of a Cyclic Universe from the Hagedorn Soup

abstract:
  One of the challenges of constructing a successful cyclic universe scenario
is to be able to incorporate the second law of thermodynamics which typically
leads to Tolman's problem of ever shrinking cycles. In this paper we construct
a non-singular toy model where as the cycles shrink in the past they also spend
more and more time in the entropy conserving Hagedorn phase. Thus in such a
scenario the entropy asymptotes to a finite non-zero constant in the infinite
past. The universe ``emerges'' from a small (string size) geodesically complete
quasi-periodic space-time. This paradigm also naturally addresses some of the
classic puzzles of Big Bang cosmology, such as the largeness, horizon and
flatness problems.


title: Multiscale theory of valley splitting

abstract:
  The coupling between $z$ valleys in the conduction band of a Si quantum well
arises from phenomena occurring within several atoms from the interface, thus
ruling out a theoretical description based on pure effective mass theory.
However, the complexity and size of a realistic device precludes an analytical
atomistic description. Here, we develop a fully analytical multiscale theory of
valley coupling, by combining effective mass and tight binding approaches. The
results are of particular interest for silicon qubits and quantum devices, but
also provide insight for GaAs quantum wells.


title: Gravitational collapse in quantum gravity

abstract:
  We give a review of recent work aimed at understanding the dynamics of
gravitational collapse in quantum gravity. Its goal is to provide a
non-perturbative computational framework for understanding the emergence of the
semi-classical approximation and Hawking radiation. The model studied is the
gravity-scalar field theory in spherical symmetry. A quantization of this
theory is given in which operators corresponding to null expansions and
curvature are well defined. Together with the Hamiltonian, these operators
allow one to follow the evolution of an initial matter-geometry state to a
trapped configuration and beyond, in a singularity free and unitary setting.


title:
Experimental studies of the fractional quantum Hall effect in the first
  excited Landau level

abstract:
  We present a spectrum of experimental data on the fractional quantum Hall
effect (FQHE) states in the first excited Landau level, obtained in an
ultrahigh mobility two-dimensional electron system (2DES) and at very low
temperatures and report the following results: For the even-denominator FQHE
states, the sample dependence of the nu=5/2 state clearly shows that disorder
plays an important role in determining the energy gap at nu=5/2. For the
developing nu=19/8 FQHE state the temperature dependence of the Rxx minimum
implies an energy gap of ~5mK.The energy gaps of the odd-denominator FQHE
states at nu=7/3 and 8/3 also increase with decreasing disorder, similar to the
gap at 5/2 state. Unexpectedly and contrary to earlier data on lower mobility
samples, in this ultra-high quality specimen, the nu=13/5 state is missing,
while its particle-hole conjugate state, the nu=12/5 state, is a fully
developed FQHE state. We speculate that this disappearance might indicate a
spin polarization of the nu=13/5 state. Finally, the temperature dependence is
studied for the two-reentrant integer quantum Hall states around nu=5/2 and is
found to show a very narrow temperature range for the transition from quantized
to classical value.


title:
Longest increasing subsequences, Plancherel-type measure and the Hecke
  insertion algorithm

abstract:
  We define and study the Plancherel-Hecke probability measure on Young
diagrams; the Hecke algorithm of [Buch-Kresch-Shimozono-Tamvakis-Yong '06] is
interpreted as a polynomial-time exact sampling algorithm for this measure.
Using the results of [Thomas-Yong '07] on jeu de taquin for increasing
tableaux, a symmetry property of the Hecke algorithm is proved, in terms of
longest strictly increasing/decreasing subsequences of words. This parallels
classical theorems of [Schensted '61] and of [Knuth '70], respectively, on the
Schensted and Robinson-Schensted-Knuth algorithms. We investigate, and
conjecture about, the limit typical shape of the measure, in analogy with work
of [Vershik-Kerov '77], [Logan-Shepp '77] and others on the ``longest
increasing subsequence problem'' for permutations. We also include a related
extension of [Aldous-Diaconis '99] on patience sorting. Together, these results
provide a new rationale for the study of increasing tableau combinatorics,
distinct from the original algebraic-geometric ones concerning K-theoretic
Schubert calculus.


title: Scale dependence of alpha effect and turbulent diffusivity

abstract:
  Aims: To determine alpha effect and turbulent magnetic diffusivity for mean
magnetic fields with profiles of different length scale from simulations of
isotropic turbulence, and to relate these results to nonlocal formulations in
which alpha and the turbulent magnetic diffusivity correspond to integral
kernels. Methods: A set of evolution equations for magnetic fields is solved
which gives the response to imposed test fields, that is, mean magnetic fields
with various wavenumbers. Both an imposed fully helical steady flow consisting
of a pattern of screw-like motions (Roberts flow) and time-dependent
statistically steady isotropic turbulence are considered. In the latter case
the aforementioned evolution equations are solved simultaneously with the
momentum and continuity equations. The corresponding results for the
electromotive force are used to calculate alpha and magnetic diffusivity
tensors. Results: For both the Roberts flow under the second--order correlation
approximation and isotropic turbulence alpha and turbulent magnetic diffusivity
are largest at large scales and these values diminish toward smaller scales. In
both cases the alpha effect and turbulent diffusion kernels are well
approximated by exponentials, corresponding to Lorentzian profiles in Fourier
space. For isotropic turbulence the turbulent diffusion kernel is half as wide
as the alpha effect kernel. For the Roberts flow beyond the second--order
correlation approximation the turbulent diffusion kernel becomes negative at
large scales.


title: Convection during the Late Stages of Simmering in Type Ia Supernovae

abstract:
  Following unstable ignition of carbon, but prior to explosion, a white dwarf
(WD) in a Type Ia supernova (SN Ia) undergoes a simmering phase. During this
time, a central convective region grows and encompasses ~1 Msun of the WD over
a timescale of ~1000 yrs, which sets the thermal and turbulent profile for the
subsequent explosion. We study this time-dependent convection and summarize
some of the key features that differ from the traditional, steady-state case.
We show that the long conductive timescale above the convective zone and the
extraction of energy to heat the WD core leads to a decrease of the convective
luminosity and characteristic velocities near the convective zone's top
boundary. In addition, differences in the composition between the convective
core and the conductive exterior will significantly alter the location of this
boundary. In this respect, we find the biggest effect due to complete 22Ne
sedimentation prior to carbon ignition. These effects add diversity to the
possible WD models, which may alter the properties of the SN Ia explosion.


title:
Without Spectroscopy at the Beginning, Catalysis Research Proceeded in
  the Wrong Direction for More Than 100 Years

abstract:
  A study by infrared spectroscopy of the physisorbed region of catalysis
demonstrated that the intermediates of catalysis exist on the surface as a two
dimensional gas. Data in the Atomic Energy Level tables show that of the
thousands of positive ions tabulated only approximately one hundred have the
low-lying excited states that produce surface electric fields with a fractional
charge. The specific catalyst for a reaction has the electric field with the
fractional charge which when imparted to the two reactants changes the
frequency of the fields at the sites of reaction on each so that they are
harmonically equal, that is their ratio is a power of two. When the two
reactants meet in the electric field of the catalyst resonance occurs. It is
during resonance that electrons are shared, paired and exchanged and bonds are
broken and made. This analysis of catalysis explains the most extraordinary
observation that a catalyst is Not consumed when used because the catalyst is
the electric fields. These discoveries are applied to explain such diverse
reactions as the oxidation and chlorination of carbon monoxide and the
destruction of nitric oxide in automobile exhaust. The use of electric fields
to produce reactions may have application not only in chemistry but in biology
and mechanics as well.


title:
Modeling elastic and photoassisted transport in organic molecular wires:
  length dependence and current-voltage characteristics

abstract:
  Using a pi-orbital tight-binding model, we study the elastic and
photoassisted transport properties of metal-molecule-metal junctions based on
oligophenylenes of varying lengths. The effect of monochromatic light is
modeled with an ac voltage over the contact. We first show how the low-bias
transmission function can be obtained analytically, using methods previously
employed for simpler chain models. In particular, the decay coefficient of the
off-resonant transmission is extracted by considering both a finite-length
chain and infinitely extended polyphenylene. Based on these analytical results,
we discuss the length-dependence of the linear-response conductance, the
thermopower, and the light-induced enhancement of the conductance in the limit
of weak intensity and low frequency. In general the conductance-enhancement is
calculated numerically as a function of the light frequency. Finally, we
compute the current-voltage characteristics at finite dc voltages, and show
that in the low-voltage regime, the effect of low-frequency light is to induce
current steps with a voltage separation determined by twice the frequency.
These effects are more pronounced for longer molecules. We study two different
profiles for the dc and ac voltages, and it is found that the results are
robust with respect to such variations. Although we concentrate here on the
specific model of oligophenylenes, the results should be qualitatively similar
for many other organic molecules with a large enough electronic gap.


title:
Nonequilibrium transport in mesoscopic multi-terminal SNS Josephson
  junctions

abstract:
  We report the results of several nonequilibrium experiments performed on
superconducting/normal/superconducting (S/N/S) Josephson junctions containing
either one or two extra terminals that connect to normal reservoirs. Currents
injected into the junctions from the normal reservoirs induce changes in the
electron energy distribution function, which can change the properties of the
junction. A simple experiment performed on a 3-terminal sample demonstrates
that quasiparticle current and supercurrent can coexist in the normal region of
the S/N/S junction. When larger voltages are applied to the normal reservoir,
the sign of the current-phase relation of the junction can be reversed,
creating a "$\pi$-junction." We compare quantitatively the maximum critical
currents obtained in 4-terminal $\pi$-junctions when the voltages on the normal
reservoirs have the same or opposite sign with respect to the superconductors.
We discuss the challenges involved in creating a "Zeeman" $\pi$-junction with a
parallel applied magnetic field and show in detail how the orbital effect
suppresses the critical current. Finally, when normal current and supercurrent
are simultaneously present in the junction, the distribution function develops
a spatially inhomogeneous component that can be interpreted as an effective
temperature gradient across the junction, with a sign that is controllable by
the supercurrent. Taken as a whole, these experiments illustrate the richness
and complexity of S/N/S Josephson junctions in nonequilibrium situations.


title: An RMHD study of transition between prompt and afterglow GRB phases

abstract:
  We study the afterglow phases of a GRB through relativistic
magnetohydrodynamic simulations. The evolution of a relativistic shell
propagating into a homogeneous external medium is followed. We focus on the
effect of the magnetization of the ejecta on the initial phases of the
ejecta-external medium interaction. In particular we are studying the condition
for the existence of a reverse shock into the ejecta, the timescale for the
transfer of the energy from the shell to the shocked medium and the resulting
multiwavelength light curves. To this end, we have developed a novel scheme to
include non-thermal processeses which is coupled to the relativistic
magnetohydrodynamic code MRGENESIS in order to compute the non-thermal
synchrotron radiation.


title:
Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top
  quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV

abstract:
  We present the first simultaneous measurement of the ratio of branching
fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top
quark pair production cross section sigma_ttbar in the lepton plus jets channel
using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the
D0 detector. We extract R and sigma_ttbar by analyzing samples of events with
0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and
sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with
the standard model prediction.


title:
Famed Bulgarian physicists. I. St. Petroff's Goettingen research of the
  photostimulated interconversions of color centers in alkali halides: the
  discovery of the photostimulated aggregation

abstract:
  This essay tells briefly of the life and work of one of the most successful
scientists originating from a Balkan settlement whose name and popularity have
greatly exceeded its realm. The word is of a discovery during WWII of the
photostimulated aggregation of the F centers (else alkali atoms) dissolved from
the vapor into an alkali halide crystal. Using optical absorption techniques
while a grantee of Humboldt's Foundation in Goettingen, Germany between
1943-1944, he found new absorption bands pertaining to small-size F center
aggregates and followed their interconversions. A primary photochemical solid
state reaction was evidenced for the first time leading to nanoscale products.


title: Monodromy in Hamiltonian Floer theory

abstract:
  Schwarz showed that when a closed symplectic manifold (M,\om) is
symplectically aspherical (i.e. the symplectic form and the first Chern class
vanish on \pi_2(M)) then the spectral invariants, which are initially defined
on the universal cover of the Hamiltonian group, descend to the Hamiltonian
group Ham (M,\om). In this note we describe less stringent conditions on the
Chern class and quantum homology of M under which the (asymptotic) spectral
invariants descend to Ham (M,\om). For example, they descend if the quantum
multiplication of M is undeformed and H_2(M) has rank >1, or if the minimal
Chern number is at least n+1 (where \dim M=2n) and the even cohomology of M is
generated by divisors. The proofs are based on certain calculations of genus
zero Gromov--Witten invariants.
  As an application, we show that the Hamiltonian group of the one point blow
up of T^4 admits a Calabi quasimorphism. Moreover, whenever the (asymptotic)
spectral invariants descend it is easy to see that Ham (M,\om) has infinite
diameter in the Hofer norm. Hence our results establish the infinite diameter
of Ham in many new cases. We also show that the area pseudonorm -- a geometric
version of the Hofer norm -- is nontrivial on the (compactly supported)
Hamiltonian group for all noncompact manifolds as well as for a large class of
closed manifolds.


title: The Distribution of Stellar Mass in the Pleiades

abstract:
  As part of an effort to understand the origin of open clusters, we present a
statistical analysis of the currently observed Pleiades. Starting with a
photometric catalog of the cluster, we employ a maximum likelihood technique to
determine the mass distribution of its members, including single stars and both
components of binary systems. We find that the overall binary fraction for
unresolved pairs is 68%. Extrapolating to include resolved systems, this
fraction climbs to about 76%, significantly higher than the accepted field-star
result. Both figures are sensitive to the cluster age, for which we have used
the currently favored value of 125 Myr. The primary and secondary masses within
binaries are correlated, in the sense that their ratios are closer to unity
than under the hypothesis of random pairing. We map out the spatial variation
of the cluster's projected and three-dimensional mass and number densities.
Finally, we revisit the issue of mass segregation in the Pleiades. We find
unambiguous evidence of segregation, and introduce a new method for quantifying
it.


title: Sculptured-thin-film plasmonic-polaritonics

abstract:
  The solution of a boundary--value problem formulated for the Kretschmann
configuration shows that the phase speed of a surface--plasmon--polariton (SPP)
wave guided by the planar interface of a sufficiently thin metal film and a
sculptured thin film (STF) depends on the vapor incidence angle used while
fabricating the STF by physical vapor deposition. Furthermore, it may be
possible to engineer the phase speed by periodically varying the vapor
incidence angle. The phase speed of the SPP wave can be set by selecting higher
mean value and/or the modulation amplitude of the vapor incidence angle.


title: Senenmut: An Ancient Egyptian Astronomer

abstract:
  The celestial phenomenon have always been a source of wonder and interest to
people, even as long ago as the ancient Egyptians. While the ancient Egyptians
did not know all the things about astronomy that we do now, they had a good
understanding of the some celestial phenomenon. The achievements in astronomy
of ancient Egyptians are relatively well known, but we know very little about
the people who made these achievements. The goal of this paper is to bring some
light on the life of Senenmut, the chief architect and astronomer during the
reign of Queen Hatshepsut.


title: SL(n,Z[t]) is not FP_{n-1}

abstract: We prove the result from the title using the geometry of Euclidean buildings.


title: Personal Recommendation via Modified Collaborative Filtering

abstract:
  In this paper, we propose a novel method to compute the similarity between
congeneric nodes in bipartite networks. Different from the standard Person
correlation, we take into account the influence of node's degree. Substituting
this new definition of similarity for the standard Person correlation, we
propose a modified collaborative filtering (MCF). Based on a benchmark
database, we demonstrate the great improvement of algorithmic accuracy for both
user-based MCF and object-based MCF.


title: Collider Physics and Cosmology

abstract:
  In the coming year, the Large Hadron Collider will begin colliding protons at
energies nearly an order of magnitude beyond the current frontier. The LHC
will, of course, provide unprecedented opportunities to discover new particle
physics. Less well-known, however, is that the LHC may also provide insights
about gravity and the early universe. I review some of these connections,
focusing on the topics of dark matter and dark energy, and highlight
outstanding prospects for breakthroughs at the interface of particle physics
and cosmology.


title: A non-standard evolution problem arising in population genetics

abstract:
  We study the evolution of the probability density of an asexual, one locus
population under natural selection and random evolution. This evolution is
governed by a Fokker-Planck equation with degenerate coefficients on the
boundaries, supplemented by a pair of conservation laws. It is readily shown
that no classical or standard weak solution definition yields solvability of
the problem. We provide an appropriate definition of weak solution for the
problem, for which we show existence and uniqueness. The solution displays a
very distinctive structure and, for large time, we show convergence to a unique
stationary solution that turns out to be a singular measure supported at the
endpoints. An exponential rate of convergence to this steady state is also
proved.


title: Stream Computing

abstract:
  Stream computing is the use of multiple autonomic and parallel modules
together with integrative processors at a higher level of abstraction to embody
"intelligent" processing. The biological basis of this computing is sketched
and the matter of learning is examined.


title: Highest weight theory for finite W-algebras

abstract:
  We define analogues of Verma modules for finite W-algebras. By the usual
ideas of highest weight theory, this is a first step towards the classification
of finite dimensional irreducible modules. Motivated by known results in type
A, we then formulate some precise conjectures in the case of nilpotent orbits
of standard Levi type.


title: A Beurling-Helson type theorem for modulation spaces

abstract:
  We prove a Beurling-Helson type theorem on modulation spaces. More precisely,
we show that the only $\mathcal{C}^{1}$ changes of variables that leave
invariant the modulation spaces $\M{p,q}(\rd)$ are affine functions on $\rd$. A
special case of our result involving the Sj\"ostrand algebra was considered
earlier by A. Boulkhemair.


title: Cosmic ray acceleration at relativistic shocks, shear layers, .

abstract:
  A review of theoretical results on cosmic ray first-order Fermi acceleration
at relativistic shock waves is presented, with recent results substantially
changing the existing knowledge on these processes. In particular one can not
expect such shocks to form particle distributions extending to very high
energies. Instead, distributions with the shock compressed injected component
followed by a more or less extended high energy tail are usually created.
Increasing the shock Lorentz factor leads to steepening of the energetic tail.
  An observational check of real electron spectra in the Cyg A hot spots
provides results clearly deviating from the standard expectations. The spectrum
consist of a very flat low energy part (sigma ~1.5)up to electron energies ~1
GeV, and a much steeper part (sigma > 3)at higher energies. We conclude with
remarks on the Fermi second-order processes acting in relativistic plasmas,
possibly the main accelerating agent for very high energy cosmic rays.


title: Spontaneous and Stimulated Star Formation in Galaxies

abstract:
  We present recent results from several on-going studies: The first addresses
the question of gas-density thresholds for star formation, as probed by the
outer disks of normal nearby galaxies. The second concerns the observational
evidence for the existence of gravitating non-luminous (GNL) galaxies, as
predicted by most recent simulations of galaxy formation in Lambda-CDM
cosmologies. We find that (1) If star formation is traced by far-ultraviolet
light, then there is no evidence for a threshold to star formation at any gas
density so far probed, and (2) there is no evidence for GNL galaxies
gravitationally interacting with known optical systems based on the
observations (a) that there are no ring galaxies without plausible optically
visible intruders, (b) all peculiar galaxies in the Arp Atlas that are bodily
distorted have nearby plausibly interacting companions, and (c) there are no
convincingly distorted/peculiar galaxies within Karachentsev's sample of more
than 1,000 apparently/optically isolated galaxies.


title:
Factorization in categories of systems of linear partial differential
  equations

abstract:
  We start with elementary algebraic theory of factorization of linear ordinary
differential equations developed in the period 1880-1930. After exposing these
classical results we sketch more sophisticated algorithmic approaches developed
in the last 20 years.
  The main part of this paper is devoted to modern generalizations of the
notion of factorization to the case of systems of linear partial differential
equations and their relation with explicit solvability of nonlinear partial
differential equations based on some constructions from the theory of abelian
categories.


title: Cepheid Mass-loss and the Pulsation -- Evolutionary Mass Discrepancy

abstract:
  I investigate the discrepancy between the evolution and pulsation masses for
Cepheid variables. A number of recent works have proposed that non-canonical
mass-loss can account for the mass discrepancy. This mass-loss would be such
that a 5Mo star loses approximately 20% of its mass by arriving at the Cepheid
instability strip; a 14Mo star, none. Such findings would pose a serious
challenge to our understanding of mass-loss. I revisit these results in light
of the Padova stellar evolutionary models and find evolutionary masses are
($17\pm5$)% greater than pulsation masses for Cepheids between 5<M/Mo<14. I
find that mild internal mixing in the main-sequence progenitor of the Cepheid
are able to account for this mass discrepancy.


title: Transmission code optimization method for incoherent scatter radar

abstract:
  When statistical inversion of a lag profile is used to determine an
incoherent scatter target, the posterior variance of the estimated target can
be used to determine how well a certain set of transmission codes perform. In
this work we present an incoherent scatter radar transmission code optimization
search method suitable for different modulation types, including binary phase,
polyphase and amplitude modulation. We find that the combination of amplitude
and phase modulation provides better performance than traditional binary phase
coding, in some cases giving better accuracy than alternating codes.


title:
Homological algebra in bivariant K-theory and other triangulated
  categories. II

abstract:
  We use homological ideals in triangulated categories to get a sufficient
criterion for a pair of subcategories in a triangulated category to be
complementary. We apply this criterion to construct the Baum-Connes assembly
map for locally compact groups and torsion-free discrete quantum groups. Our
methods are related to the abstract version of the Adams spectral sequence by
Brinkmann and Christensen.


title: The Physics of Heavy Z' Gauge Bosons

abstract:
  The U(1)' symmetry associated with a possible heavy Z' would have profound
implications for particle physics and cosmology. The motivations for such
particles in various extensions of the standard model, possible ranges for
their masses and couplings, and classes of anomaly-free models are discussed.
Present limits from electroweak and collider experiments are briefly surveyed,
as are prospects for discovery and diagnostic study at future colliders.
Implications of a Z' are discussed, including an extended Higgs sector,
extended neutralino sector, and solution to the mu problem in supersymmetry;
exotic fermions needed for anomaly cancellation; possible flavor changing
neutral current effects; neutrino mass; possible Z' mediation of supersymmetry
breaking; and cosmological implications for cold dark matter and electroweak
baryogenesis.


title: Reaching the End of the White Dwarf Cooling Sequence in NGC 6791

abstract:
  We present new observations of the white dwarf sequence of the old open
cluster NGC 6791. The brighter peak previously observed in the white dwarf
luminosity function (WDLF) is now better delineated, and the second, fainter
peak that we suggested earlier is now confirmed. A careful study suggests that
we have reached the end of the white dwarf sequence. The WDs that create the
two peaks in the WDLF show a significant turn to the blue in the
color-magnitude diagram. The discrepancy between the age from the WDs and that
from the main sequence turnoff remains, and we have an additional puzzle in the
second peak in the WDLF. Canonical WD models seem to fail --at least at
~25%-level-- in reproducing the age of clusters of this metallicity. We discuss
briefly possible ways of arriving at a theoretical understanding of the WDLF.