title: Mid-infrared interferometry of massive young stellar objects

abstract:
  The very inner structure of massive young stellar objects (YSOs) is difficult
to trace. With conventional observational methods we identify structures still
several hundreds of AU in size. However, the (proto-)stellar growth takes place
at the innermost regions (<100 AU) where the actual mass transfer onto the
forming high-mass star occurs. We present results from our programme toward
massive YSOs at the VLTI, utilising the two-element interferometer MIDI. To
date, we observed 10 well-known massive YSOs down to scales of 20 mas
(typically corresponding to 20 - 40 AU for our targets) in the 8-13 micron
region. We clearly resolve these objects which results in low visibilities and
sizes in the order of 30-50 mas. For two objects, we show results of our
modelling. We demonstrate that the MIDI data can reveal decisive structure
information for massive YSOs. They are often pivotal in order to resolve
ambiguities still immanent in model parameters derived from sole SED fitting.


title: Dynamical dark energy from extra dimensions

abstract:
  We consider multidimensional cosmological model with a higher-dimensional
product manifold M = R x R^{d_0} x H^{d_1}/\Gamma where R^{d_0} is
d_0-dimensional Ricci-flat external (our) space and H^{d_1}/\Gamma is
d_1-dimensional compact hyperbolic internal space. M2-brane solution for this
model has the stage of accelerating expansion of the external space. We apply
this model to explain the late time acceleration of our Universe. Recent
observational data (the Hubble parameter at the present time and the redshift
when the deceleration parameter changes its sign) fix fully all free parameters
of the model. As a result, we find that considered model has too big size of
the internal space at the present time and variation of the effective
four-dimensional fine structure constant strongly exceeds the observational
limits.


title:
Vari'et'es presque rationnelles, leurs points rationnels et leurs
  d'eg'en'erescences

abstract:
  This survey, which contains very few proofs, addresses the general question:
Over a given type of field, is there a natural class of varieties which
automatically have a rational point? Fields under consideration here include:
finite fields, p-adic fields, function fields in one or two variables over an
algebraically closed field. Classical answers are given by the
Chevalley-Warning theorem and by Tsen's theorem. More general answers were
provided by a theorem of Graber, Harris and Starr and by a theorem of Esnault.
The latter results apply to rationally connected varieties. We discuss these
varieties from various angles : weak approximation, R-equivalence, Chow group
of zero-cycles. Ongoing work on `rationally simply connected' varieties over
function fields in two variables is also mentioned. A common thread in this
report is the study of the special fibre of a scheme over a discrete valuation
ring: if the generic fibre has a simple geometry, what does it imply for the
special fibre?


title:
Integral models of unitary representations of current groups with values
  in semidirect products

abstract:
  We describe a general construction of irreducible unitary representations of
the group of currents with values in the semidirect product of a locally
compact subgroup $P_0$ and a one-parameter group ${\mathbb R {}}^*_+=\{r:r>0\}$
of automorphisms of $P_0$. This construction is determined by a a faithful
unitary representation of $P_0$ (canonical representation) whose images under
the action of the group of automorphisms tend to the identity representation as
$r\to 0$. We apply this construction to the groups of currents of the maximal
parabolic subgroups of the groups of motions of the $n$-dimensional real and
complex Lobachevsky spaces. The obtained representations of the groups of
parabolic currents can be uniquely extended to the groups of currents with
values in the semisimple groups O(n,1) and U(n,1). This gives a new description
of the representations of the groups of currents of these groups constructed in
the 70s and realized in the Fock space. The key role in our construction is
played by the so-called special representation of the parabolic subgroup $P$
and the remarkable $\sigma$-finite measure (Lebesgue measure) $\mathcal L$ in
the space of distributions.


title: M31N 2007-11d: A Slowly-Rising, Luminous Nova in M31

abstract:
  We report a series of extensive photometric and spectroscopic observations of
the luminous M31 nova M31N 2007-11d. Our photometric observations coupled with
previous measurements show that the nova took at least four days to reach peak
brightness at R~14.9 on 20 Nov 2007 UT. After reaching maximum, the time for
the nova to decline 2 and 3 magnitudes from maximum light (t_2 and t_3) was
~9.5 and ~13 days, respectively, establishing that M31N 2007-11d was a
moderately fast declining nova. During the nova's evolution a total of three
spectra were obtained. The first spectrum was obtained one day after maximum
light (5 days post-discovery), followed by two additional spectra taken on the
decline at two and three weeks post-maximum. The initial spectrum reveals
narrow Balmer and Fe II emission with P Cygni profiles superimposed on a blue
continuum. These data along with the spectra obtained on the subsequent decline
clearly establish that M31N 2007-11d belongs to the Fe II spectroscopic class.
The properties of M31N 2007-11d are discussed within the context of other
luminous novae in M31, the Galaxy, and the LMC. Overall, M31N 2007-11d appears
to be remarkably similar to Nova LMC 1991, which was another bright,
slowly-rising, Fe II nova. A comparison of the available data for luminous
extragalactic novae suggest that the >~4 day rise to maximum light seen in M31N
2007-11d may not be unusual, and that the rise times of luminous Galactic
novae, usually assumed to be <~2 days, may have been underestimated.


title: A time - luminosity correlation for Gamma Ray Bursts in the X - rays

abstract:
  Gamma ray bursts (GRBs) have recently attracted much attention as a possible
way to extend the Hubble diagram to very high redshift. However, the large
scatter in their intrinsic properties prevents directly using them as distance
indicator so that the hunt is open for a relation involving an observable
property to standardize GRBs in the same way as the Phillips law makes it
possible to use Type Ia Supernovae (SNeIa) as standardizable candles. We use
here the data on the X - ray decay curve and spectral index of a sample of GRBs
observed with the Swift satellite. These data are used as input to a Bayesian
statistical analysis looking for a correlation between the X - ray luminosity
L_X(T_a) and the time constant T_a of the afterglow curve. We find a linear
relation between \log{[L_X(T_a)]} and \log{[T_a/(1+z)]} with an intrinsic
scatter sigma_{int} = 0.33 comparable to previously reported relations.
Remarkably, both the slope and the intrinsic scatter are almost independent on
the matter density Omega_M and the constant equation of state w of the dark
energy component thus suggesting that the circularity problem is alleviated for
the $L_X - T_a$ relation.


title:
Flavour Changing Neutral Current Constraints from Kaluza-Klein Gluons
  and Quark Mass Matrices in RS1

abstract:
  We continue our previous study on what are the allowed forms of quark mass
matrices in the Randall-Sundrum (RS) framework that can reproduce the
experimentally observed quark mass spectrum and the CKM mixing pattern. We
study the constraints the $\Delta F = 2$ processes in the neutral meson sector
placed on the admissible forms found there, and we found only the asymmetrical
type of quark mass matrices arising from anarchical Yukawa structures stay
viable at the few TeV scale reachable at the LHC. We study also the decay of
the first Kaluza-Klein (KK) excitation of the gluon. We give the decay
branching ratios into quark pairs, and we point out that measurements of the
decay width and just one of the quark spins in the dominant $\bar{t}t$ decays
can be used to extract the effective coupling of the first KK gluon to top
quarks for both chiralities. This provides further probe to the flavour
structure of the RS framework.


title: The superstring cosmological constant and the Schottky form in genus 5

abstract:
  Combining certain identities for modular forms due to Igusa with
Schottky-Jung relations, we study the cosmological constant for the recently
proposed ansatz for the chiral superstring measure in genus 5. The vanishing of
this cosmological constant turns out to be equivalent to the long-conjectured
vanishing of a certain explicit modular form of genus 5 on the moduli of curves
M_5, and we disprove this conjecture, thus showing that the cosmological
constant for the proposed ansatz does not vanish identically. We exhibit an
easy modification of the genus 5 ansatz satisfying factorization constraints
and yielding a vanishing cosmological constant. We also give an expression for
the cosmological constant for the proposed ansatz that should hold for any
genus if certain generalized Schottky-Jung identities hold.


title:
Interface states and anomalous quantum oscillations in graphene hybrid
  structures

abstract:
  One- and two-layer graphene have recently been shown to feature new physical
phenomena such as unconventional quantum Hall effects and prospects of
supporting a non-silicon technological platform using epitaxial graphene. While
both one- and two-layer graphene have been studied extensively, continuous
sheets of graphene possessing both parts have not yet been explored. Here we
report a study of such graphene hybrid structures. In a bulk hybrid featuring
two large-area one- and two-layer graphene and an interface between them, two
sets of Landau levels and features related to the interface were found. In edge
hybrids featuring a large two-layer graphene with narrow one-layer graphene
edges, we observed an anomalous suppression in quantum oscillation amplitude
due to the locking of one- and two-layer graphene Fermi energies and emergent
chiral interface states. These findings demonstrate the importance of these
hybrid structures whose unique interface states and related phenomena deserve
further studies.


title: Graphical models for correlated defaults

abstract:
  A simple graphical model for correlated defaults is proposed, with explicit
formulas for the loss distribution. Algebraic geometry techniques are employed
to show that this model is well posed for default dependence: it represents any
given marginal distribution for single firms and pairwise correlation matrix.
These techniques also provide a calibration algorithm based on maximum
likelihood estimation. Finally, the model is compared with standard normal
copula model in terms of tails of the loss distribution and implied correlation
smile.


title: First Results from the Catalina Real-time Transient Survey

abstract:
  We report on the results from the first six months of the Catalina Real-time
Transient Survey (CRTS). In order to search for optical transients with
timescales of minutes to years, the CRTS analyses data from the Catalina Sky
Survey which repeatedly covers twenty six thousand of square degrees on the
sky. The CRTS provides a public stream of transients that are bright enough to
be followed up using small telescopes. Since the beginning of the survey, all
CRTS transients have been made available to astronomers around the world in
real-time using HTML tables, RSS feeds and VOEvents. As part of our public
outreach program the detections are now also available in KML through Google
Sky.
  The initial discoveries include over 350 unique optical transients rising
more than two magnitudes from past measurements. Sixty two of these are
classified as supernovae, based on light curves, prior deep imaging and
spectroscopic data. Seventy seven are due to cataclysmic variables (only 13
previously known), while an additional 100 transients were too infrequently
sampled to distinguish between faint CVs and SNe. The remaining optical
transients include AGN, Blazars, high proper motions stars, highly variable
stars (such as UV Ceti stars) and transients of an unknown nature. Our results
suggest that there is a large population of SNe missed by many current
supernova surveys because of selection biases. These objects appear to be
associated with faint host galaxies. We also discuss the unexpected discovery
of white dwarf binary systems through dramatic eclipses.


title: Degeneracy and decomposability in abelian crossed products

abstract:
  In this paper we study the relationship between degeneracy and
decomposability in abelian crossed products. In particular we construct an
indecomposable abelian crossed product division algebra of exponent $p$ and
index $p^2$ for $p$ an odd prime. The algebra we construct is generic in the
sense of Amitsur and Saltman and has the property that its underlying abelian
crossed product is a decomposable division algebra defined by a non-degenerate
matrix. This algebra gives an example of an indecomposable generic abelian
crossed product which is shown to be indecomposable without using torsion in
the Chow group of the corresponding Severi-Brauer variety as was needed in
[Karpenko, Codimension 2 cycles on Severi-Brauer varieites (1998)] and
[McKinnie, Indecomposable $p$-algebras and Galois subfields in generic abelian
crossed products (2008)]. It also gives an example of a Brauer class which is
in Tignol's Dec group with respect to one abelian maximal subfield, but not in
the Dec group with respect to another.


title: The Monoceros R2 Molecular Cloud

abstract:
  The Monoceros R2 region was first recognized as a chain of reflection nebulae
illuminated by A- and B-type stars. These nebulae are associated with a giant
molecular cloud that is one of the closest massive star forming regions to the
Sun. This chapter reviews the properties of the Mon R2 region, including the
namesake reflection nebulae, the large scale molecular cloud, global star
formation activity, and properties of prominent star forming regions in the
cloud.


title: Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds

abstract:
  The properties of Galactic molecular clouds tabulated by Solomon etal (1987)
(SRBY) are re-examined using the Boston University-FCRAO Galactic Ring Survey
of 13CO J=1-0 emission. These new data provide a lower opacity tracer of
molecular clouds and improved angular and spectral resolution than previous
surveys of molecular line emission along the Galactic Plane. We calculate GMC
masses within the SRBY cloud boundaries assuming LTE conditions throughout the
cloud and a constant H2 to 13CO abundance, while accounting for the variation
of the 12C/13C with Galacto-centric radius. The LTE derived masses are
typically five times smaller than the SRBY virial masses. The corresponding
median mass surface density of molecular hydrogen for this sample is 42
Msun/pc^2, which is significantly lower than the value derived by SRBY (median
206 Msun/pc^2) that has been widely adopted by most models of cloud evolution
and star formation. This discrepancy arises from both the extrapolation by SRBY
of velocity dispersion, size, and CO luminosity to the 1K antenna temperature
isophote that likely overestimates the GMC masses and our assumption of
constant 13CO abundance over the projected area of each cloud. Owing to the
uncertainty of molecular abundances in the envelopes of clouds, the mass
surface density of giant molecular clouds could be larger than the values
derived from our 13CO measurements. From velocity dispersions derived from the
13CO data, we find that the coefficient of the cloud structure functions,
vo=sigma_v/R^{1/2}, is not constant, as required to satisfy Larson's scaling
relationships, but rather systematically varies with the surface density of the
cloud as Sigma^{0.5} as expected for clouds in self-gravitational equlibrium.


title:
Stability of Maximum likelihood based clustering methods: exploring the
  backbone of classifications (Who is keeping you in that community?)

abstract:
  Components of complex systems are often classified according to the way they
interact with each other. In graph theory such groups are known as clusters or
communities. Many different techniques have been recently proposed to detect
them, some of which involve inference methods using either Bayesian or Maximum
Likelihood approaches. In this article, we study a statistical model designed
for detecting clusters based on connection similarity. The basic assumption of
the model is that the graph was generated by a certain grouping of the nodes
and an Expectation Maximization algorithm is employed to infer that grouping.
We show that the method admits further development to yield a stability
analysis of the groupings that quantifies the extent to which each node
influences its neighbors group membership. Our approach naturally allows for
the identification of the key elements responsible for the grouping and their
resilience to changes in the network. Given the generality of the assumptions
underlying the statistical model, such nodes are likely to play special roles
in the original system. We illustrate this point by analyzing several empirical
networks for which further information about the properties of the nodes is
available. The search and identification of stabilizing nodes constitutes thus
a novel technique to characterize the relevance of nodes in complex networks.

categories: physics.soc-ph cond-mat.stat-mech cs.IT math.IT physics.comp-ph physics.data-an


title:
Solving the Imaging Problem with Coherently Integrated Multiwavelength
  Data

abstract:
  Recovering images from optical interferometric observations is one of the
major challenges in the field. Unlike the case of observations at radio
wavelengths, in the optical the atmospheric turbulence changes the phases on a
very short time scale, which results in corrupted phase measurements. In order
to overcome these limitations, several groups developed image reconstruction
techniques based only on squared visibility and closure phase information,
which are unaffected by atmospheric turbulence. We present the results of two
techniques used by our group, which employed coherently integrated data from
the Navy Prototype Optical Interferometer. Based on these techniques we were
able to recover complex visibilities for several sources and image them using
standard radio imaging software. We describe these techniques, the corrections
applied to the data, present the images of a few sources, and discuss the
implications of these results.


title:
Symmetry-preserving observers for some water tank problems: theory and
  application to a shallow water model

abstract:
  In this paper we consider a tank containing fluid and we want to estimate the
horizontal currents when the fluid surface height is measured. The fluid motion
is described by shallow water equations in two horizontal dimensions. We build
a simple non-linear observer which takes advantage of the symmetries of fluid
dynamics laws. As a result its structure is based on convolutions with smooth
isotropic kernels, and the observer is remarkably robust to noise. We prove the
convergence of the observer around a steady-state. In numerical applications
local exponential convergence is expected. The observer is also applied to the
problem of predicting the ocean circulation. Realistic simulations illustrate
the relevance of the approach compared with some standard oceanography
techniques.


title:
The Zeta Functions of Complexes from $\PGL(3)$: a
  Representation-theoretic Approach

abstract:
  The zeta function attached to a finite complex $X_\Gamma$ arising from the
Bruhat-Tits building for $\PGL_3(F)$ was studied in \cite{KL}, where a closed
form expression was obtained by a combinatorial argument. This identity can be
rephrased using operators on vertices, edges, and directed chambers of
$X_\Gamma$. In this paper we reprove the zeta identity from a different aspect
by analyzing the eigenvalues of these operators using representation theory. As
a byproduct, we obtain equivalent criteria for a Ramanujan complex in terms of
the eigenvalues of the operators on vertices, edges, and directed chambers,
respectively.


title:
Central engines of Gamma Ray Bursts. Magnetic mechanism in the collapsar
  model

abstract:
  In this study we explore the magnetic mechanism of hypernovae and
relativistic jets of long duration gamma ray bursts within the collapsar
scenario. This is an extension of our earlier work [1]. We track the collapse
of massive rotating stars onto a rotating central black hole using axisymmetric
general relativistic magnetohydrodynamic code that utilizes a realistic
equation of state and takes into account the cooling associated with emission
of neutrinos and the energy losses due to dissociation of nuclei. The neutrino
heating is not included. We describe solutions with different black hole
rotation, mass accretion rate, and strength of progenitor's magnetic field.
Some of them exhibits strong explosions driven by Poynting-dominated jets with
power up to $12\times10^{51} {erg s}^{-1}$. These jets originate from the black
hole and powered via the Blandford-Znajek mechanism. A provisional criterion
for explosion is derived. A number of simulation movies can be downloaded from
http://www.maths.leeds.ac.uk/~serguei/research/movies/anim.html


title:
Digital control of force microscope cantilevers using a field
  programmable gate array

abstract:
  This report describes a cantilever controller for magnetic resonance force
microscopy (MRFM) based on a field programmable gate array (FPGA), along with
the hardware and software used to integrate the controller into an experiment.
The controller is assembled from a low-cost commercially available software
defined radio (SDR) device and libraries of open-source software. The
controller includes a digital filter comprising two cascaded second-order
sections ("biquads"), which together can implement transfer functions for
optimal cantilever controllers. An appendix in this report shows how to
calculate filter coefficients for an optimal controller from measured
cantilever characteristics. The controller also includes an input multiplexer
and adder used in calibration protocols. Filter coefficients and multiplexer
settings can be set and adjusted by control software while an experiment is
running. The input is sampled at 64 MHz; the sampling frequency in the filters
can be divided down under software control to achieve a good match with filter
characterisics. Data reported here were sampled at 500 kHz, chosen for acoustic
cantilevers with resonant frequencies near 8 kHz. Inputs are digitized with 12
bits resolution, outputs with 14 bits. The experiment software is organized as
a client and server to make it easy to adapt the controller to different
experiments. The server encapusulates the details of controller hardware
organization, connection technology, filter architecture, and number
representation. The same server could be used in any experiment, while a
different client encodes the particulars of each experiment.


title: On the unfolding of simple closed curves

abstract:
  I show that every rectifiable simple closed curve in the plane can be
continuously deformed into a convex curve in a motion which preserves arc
length and does not decrease the Euclidean distance between any pair of points
on the curve. This result is obtained by approximating the curve with polygons
and invoking the result of Connelly, Demaine, and Rote that such a motion
exists for polygons. I also formulate a generalization of their program,
thereby making steps toward a fully continuous proof of the result. To
facilitate this, I generalize two of the primary tools used in their program:
the Farkas Lemma of linear programming to Banach spaces and the Maxwell-Cremona
Theorem of rigidity theory to apply to stresses represented by measures on the
plane.


title: Non-commutative Supersymmetric Quantum Mechanics

abstract:
  General non-commutative supersymmetric quantum mechanics models in two and
three dimensions are constructed and some two and three dimensional examples
are explicitly studied. The structure of the theory studied suggest other
possible applications in physical systems with potentials involving spin and
non-local interactions.


title: Comment on "Central limit behavior in deterministic dynamical systems"

abstract:
  We check claims for a generalized central limit theorem holding at the
Feigenbaum (infinite bifurcation) point of the logistic map, made recently by
U. Tirnakli, C. Beck, and C. Tsallis (Phys. Rev. {\bf 75}, 040106(R) (2007)).
We show that there is no obvious way that these claims can be made consistent
with high statistics simulations. We also refute more recent claims by the same
authors that extend the claims made in the above reference.


title: W/Z + Light Flavor Jets and W/Z + Heavy Flavor Jets at the Tevatron

abstract:
  Collider signatures containing bosons and jets are particularly interesting.
Recent theoretical effort has been devoted to determining predictions of W/Z +
multiple parton production; the high statistics sample of W/Z + jets events
collected at the Tevatron is a valuable testbed for probing the validity of
these calculations. The final state containing a Z or W boson and one or more
b-jets is a promising Higgs search channel at the Tevatron and could be a
window to new physics at the LHC. These searches benefit from a deep
understanding of the production of W/Z + heavy flavor jets which constitutes a
significant background to the more exotic sources of this signature. Herein the
latest Tevatron results on these production mechanisms are reviewed with an
emphasis on comparison of data results to the latest theoretical models.


title: Classification of BPS equations in higher dimensions

abstract:
  We systematically classify all possible Bogomol'nyi-Prasad-Sommerfield (BPS)
equations in Euclidean dimension $d\leq8$. We discuss symmetries of BPS
equations and their connection with the self-dual Yang-Mills equations. Also,
we present a general method allowing to obtain the BPS equations in any
dimension. In addition, we find all BPS equations in the Minkowski space of
dimension $d\leq6$ and apply the obtained results to the supersymmetric
Yang-Mills theories. In conclusion, we discuss the possibility of using the
classification to construct soliton solutions of the low-energy effective
theory of the heterotic string.


title: Domain Specific Software Architecture for Design Center Automation

abstract:
  Domain specific software architecture aims at software reuse through
construction of domain architecture reference model. The constructed reference
model presents a set of individual components and their interaction points.
When starting on a new large software project, the design engineer starts with
pre-constructed model, which can be easily browsed and picks up opportunities
of use in the new solution design. This report discusses application of domain
reference design methods by deriving domain specific reference architecture for
a product ordering system in a design center. The product in this case is
instock and special order blinds from different manufacturers in a large supply
store. The development of mature domain specific reference software
architecture for this domain is not the objective of this report. However, this
report would like to capture the method used in one such process and that is
the primary concern of this report. This report lists subjective details of
such a process applied to the domain of ordering custom and instock blinds from
a large home construction and goods supply store. This report also describes
the detailed process of derivation of knowledge models, unified knowledge
models and the reference architecture for this domain. However, this domain
model is only partially complete which may not be used for any real
applications. This report is a result of a course project undertaken while
studying this methodology.


title: Anisotropic three-dimensional magnetism in CaFe2As2

abstract:
  Inelastic neutron scattering measurements on the low energy spin waves in
CaFe2As2 show that the magnetic exchange interactions in the Fe layers are
exceptionally large and similar to the cuprates. However, the exchange between
layers is ~10% of the coupling in the layers and the magnetism is more
appropriately categorized as anisotropic three-dimensional, in contrast to the
two-dimensional cuprates. Band structure calculations of the spin dynamics and
magnetic exchange interactions are in good agreement with the experimental
data.


title: On a family of tridiagonal matrices

abstract:
  We show that certain integral positive definite symmetric tridiagonal
matrices of determinant $n$ are in one to one correspondence with elements of
$(\mathbb Z/n\mathbb Z)^*$. We study some properties of this correspondence. In
a somewhat unrelated second part we discuss a construction which associates a
sequence of integral polytopes to every integral symmetric matrix.


title: Fisher zeros in the Kallen-Lehmann approach to 3D Ising model

abstract:
  The distribution of the Fisher zeros in the Kallen-Lehmann approach to
three-dimensional Ising model is studied. It is argued that the presence of a
non-trivial angle (a cusp) in the distribution of zeros in the complex
temperatures plane near the physical singularity is realized through a strong
breaking of the 2D Ising self-duality. Remarkably, the realization of the cusp
in the Fisher distribution ultimately leads to an improvement of the results of
the Kallen-Lehmann ansatz. In fact, excellent agreement with Monte Carlo
predictions both at high and at low temperatures is observed. Besides,
agreement between both approaches is found for the predictions of the critical
exponent alpha and of the universal amplitude ratio Delta = A_+/A_-, within the
3.5% and 7% of the Monte Carlo predictions, respectively.


title: Cosmology of Bifundamental Fields

abstract:
  If a field theory contains gauged, non-Abelian, bi-fundamental fields i.e.
fields that are charged under two separate non-Abelian gauge groups, the
transition from a deconfined phase to a hadronic phase may be frustrated.
Similar frustration may occur in non-Abelian gauge models containing matter
only in higher dimensional representations e.g. models with pure glue, or if
ordinary quarks are confined by two flux tubes, as implied in the triangular
configuration of baryons within QCD. In a cosmological setting, such models can
lead to the formation of a web of confining electric flux tubes that can
potentially have observational signatures.


title:
Optimal control of entangling operations for trapped ion quantum
  computing

abstract:
  Optimal control techniques are applied for the decomposition of unitary
quantum operations into a sequence of single-qubit gates and entangling
operations. To this end, we modify a gradient-ascent algorithm developed for
systems of coupled nuclear spins in molecules to make it suitable for trapped
ion quantum computing. We decompose unitary operations into entangling gates
that are based on a nonlinear collective spin operator and complemented by
global spinflip and local light shift gates. Among others, we provide explicit
decompositions of controlled-NOT and Toffoli gates, and a simple quantum error
correction protocol.


title:
Non-equilibrium transport through a point contact in the $\nu=5/2$
  non-Abelian quantum Hall state

abstract:
  We analyze charge-$e/4$ quasiparticle tunneling between the edges of a point
contact in a non-Abelian model of the $\nu=5/2$ quantum Hall state. We map this
problem to resonant tunneling between attractive Luttinger liquids and use the
time-dependent density-matrix renormalization group (DMRG) method to compute
the current through the point contact in the presence of a {\it finite voltage
difference} between the two edges. We confirm that, as the voltage is
decreases, the system is broken into two pieces coupled by electron hopping. In
the limits of small and large voltage, we recover the results expected from
perturbation theory about the infrared and ultraviolet fixed points. We test
our methods by finding the analogous non-equilibrium current through a point
contact in a $\nu=1/3$ quantum Hall state, confirming the Bethe ansatz solution
of the problem.


title: Truncated Heat Kernel and One-Loop Determinants for the BTZ Geometry

abstract:
  There is a special relation between the spectrum and the {\it truncated} heat
kernel of the Euclidean BTZ black hole with the Patterson-Selberg zeta
function. Using an orbifold description of this relation we calculate the
on-shell corrections of the gravitational quantum fluctuations.


title: Future Evolution of Bound Superclusters in an Accelerating Universe

abstract:
  The evolution of marginally bound supercluster-like objects in an
accelerating LambdaCDM Universe is followed, by means of cosmological
simulations, from the present time to an expansion factor a = 100. The objects
are identified on the basis of the binding density criterion introduced by
Dunner et al. (2006). superclusters are identified with the ones whose mass M >
10^15 M_sun/h, the most massive one with M ~ 8x10^15 M_sun/h, comparable to the
Shapley supercluster. The spatial distribution of the superclusters remains
essentially the same after the present epoch, reflecting the halting growth of
the Cosmic Web as Lambda gets to dominate the expansion of the Universe. The
same trend can be seen in the stagnation of the development of the mass
function of virialized haloes and bound objects. The situation is considerably
different when looking at the internal evolution, quantified in terms of their
shape, compactness and density profile, and substructure in terms of their
multiplicity function. We find a continuing evolution from a wide range of
triaxial shapes at a = 1 to almost perfect spherical shapes at a = 100. We also
find a systematic trend towards a higher concentration. Meanwhile, we see their
substructure gradually disappearing, as the surrounding subclumps fall in and
merge to form one coherent, virialized system.


title:
Formation of Jupiter and Conditions for Accretion of the Galilean
  Satellites

abstract:
  We present an overview of the formation of Jupiter and its associated
circumplanetary disk. Jupiter forms via a combination of planetesimal accretion
and gravitational accumulation of gas from the surrounding solar nebula. The
formation of the circumjovian gaseous disk, or subnebula, straddles the
transitional stage between runaway gas accretion and Jupiter's eventual
isolation from the solar disk. This isolation, which effectively signals the
termination of Jupiter's accretion, takes place as Jupiter opens a deep gas gap
in the solar nebula, or the solar nebula gas dissipates. We describe the
conditions for accretion of the Galilean satellites, including the timescales
for their formation, and mechanisms for their survival, all within the context
of key constraints for satellite formation models. The environment in which the
regular satellites form is tied to the timescale for circumplanetary disk
dispersal, which depends on the nature and persistence of turbulence. In the
case that subnebula turbulence decays as gas inflow wanes, we present a novel
mechanism for satellite survival involving gap opening by the largest
satellites. On the other hand, assuming that sustained turbulence drives
subnebula evolution on a short timescale compared to the satellite formation
timescale, we review a model that emphasizes collisional processes to explain
satellite observations. We briefly discuss the mechanisms by which solids may
be delivered to the circumplanetary disk. However, we expect that planetesimal
delivery mechanisms likely provide the bulk of material for satellite
accretion.


title:
First fragmentation function measurements from full jet reconstruction
  in heavy-ion collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV by STAR

abstract:
  Measurements of inclusive hadron suppression and di-hadron azimuthal
correlations in ultra-relativistic nuclear collisions at RHIC have provided
important insights into jet quenching in hot QCD matter, but are limited in
their sensitivity due to well-known biases. Full jet reconstruction in
heavy-ion collisions would conceptually provide a direct measurement of the
energy of the scattered parton before energy loss, alleviating such biases and
allowing a measurement of the energy loss probability distribution in a
model-independent way from hard probes. In these proceedings we utilize recent
progress in the reconstruction of jets in the heavy ion environment and present
the first measurement of the fragmentation function from fully reconstructed
jets in heavy ion collisions. The fragmentation function measured in central
Au+Au collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV will be presented and
discussed with respect to p+p reference measurements.


title: Some Properties of the Spin-Polarized Attractive Hubbard Model

abstract:
  The influence of a Zeeman magnetic field on the superconducting
characteristics of the attractive Hubbard model was investigated. The ground
state and temperature phase diagrams were obtained for a fixed number of
particles. Two critical magnetic fields were found for the first order phase
transition from the superconducting to the normal state for $n\neq 1$. For some
range of parameters a reentrant transition was found and gapless
superconductivity was obtained. The significance of the Hartree term was also
analyzed.


title: An Application of Topological Multiple Recurrence to Tiling

abstract:
  We show that given any tiling of Euclidean space, any geometric patterns of
points, we can find a patch of tiles (of arbitrarily large size) so that copies
of this patch appear in the tiling nearly centered on a scaled and translated
version of the pattern. The rather simple proof uses Furstenberg's topological
multiple recurrence theorem.


title: Quantum phases of a Two-Dimensional Dipolar Fermi Gas

abstract:
  We examine the superfluid and collapse instabilities of a quasi
two-dimensional gas of dipolar fermions aligned by an orientable external
field. It is shown that the interplay between the anisotropy of the dipolar
interaction, the geometry of the system, and the p-wave symmetry of the
superfluid order parameter means that the effective interaction for pairing can
be made very large without the system collapsing. This leads to a broad region
in the phase diagram where the system forms a stable superfluid. Analyzing the
superfluid transition at finite temperatures, we calculate the
Berezinskii--Kosterlitz--Thouless temperature as a function of the dipole
angle.


title: Effects of Strong Correlations and Disorder in d-Wave Superconductors

abstract:
  We use exact diagonalization techniques to study the interplay between strong
correlations, superconductivity, and disorder in a model system. We study an
extension of the t-J model by adding an infinite-range d-wave superconductivity
inducing term and disorder. Our work shows that in the clean case the magnitude
of the order parameter is surprisingly small for low-hole filling, thus
implying that mean-field theories might be least accurate in that important
regime. We demonstrate that substantial disorder is required to destroy a
d-wave superconducting state for low-hole doping. We provide the first bias
free numerical results for the local density of states of a strongly correlated
d-wave superconducting model, relevant for STM measurements at various fillings
and disorders.


title:
Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion
  to a Young Solar Analog

abstract:
  We present Gemini near-infrared adaptive optics imaging and spectroscopy of a
planetary mass candidate companion to 1RXS J160929.1-210524, a roughly
solar-mass member of the 5 Myr-old Upper Scorpius association. The object,
separated by 2.22" or 330 AU at ~150 pc, has infrared colors and spectra
suggesting a temperature of 1800(-100/+200) K, and spectral type of L4(-2/+1).
The H- and K-band spectra provide clear evidence of low surface gravity, and
thus youth. Based on the widely used DUSTY models, we infer a mass of
8(-2/+4)Mjupiter. If gravitationally bound, this would be the lowest mass
companion imaged around a normal star thus far, and its existence at such a
large separation would pose a serious challenge to theories of star and planet
formation.


title: Effective medium theory for disordered two-dimensional graphene

abstract:
  We develop an Effective Medium Theory to study the electrical transport
properties of disordered graphene. The theory includes non-linear screening and
exchange-correlation effects allowing us to consider experimentally relevant
strengths of the Coulomb interaction. Assuming random Coulomb impurities, we
calculate the electrical conductivity as a function of gate voltage describing
quantitatively the full cross-over from the fluctuations dominated regime
around the Dirac point to the large doping regime at high gate voltages. We
find that the conductivity at the Dirac point is strongly affected by exchange
correlation effects.


title:
The evolution of the specific star formation rate of massive galaxies to
  z ~ 1.8 in the E-CDFS

abstract:
  We study the evolution of the star formation rate (SFR) of mid-infrared (IR)
selected galaxies in the extended Chandra Deep Field South (E-CDFS). We use a
combination of U-K GaBoDS and MUSYC data, deep IRAC observations from SIMPLE,
and deep MIPS data from FIDEL. This unique multi-wavelength data set allows us
to investigate the SFR history of massive galaxies out to redshift z ~ 1.8. We
determine star formation rates using both the rest-frame ultraviolet luminosity
from young, hot stars and the total IR luminosity of obscured star formation
obtained from the MIPS 24 um flux. We find that at all redshifts the galaxies
with higher masses have substantially lower specific star formation rates than
lower mass galaxies. The average specific star formation rates increase with
redshift, and the rate of incline is similar for all galaxies (roughly
(1+z)^{n}, n = 5.0 +/- 0.4). It does not seem to be a strong function of galaxy
mass. Using a subsample of galaxies with masses M_*> 10^11 M_sun, we measured
the fraction of galaxies whose star formation is quenched. We consider a galaxy
to be in quiescent mode when its specific star formation rate does not exceed
1/(3 x t_H), where t_H is the Hubble time. The fraction of quiescent galaxies
defined as such decreases with redshift out to z ~ 1.8. We find that, at that
redshift, 19 +/-9 % of the M_* > 10^11 M_sun sources would be considered
quiescent according to our criterion.


title:
Interpreting Helioseismic Structure Inversion Results of Solar Active
  Regions

abstract:
  Helioseismic techniques such as ring-diagram analysis have often been used to
determine the subsurface structural differences between solar active and quiet
regions. Results obtained by inverting the frequency differences between the
regions are usually interpreted as the sound-speed differences between them.
These in turn are used as a measure of temperature and magnetic-field strength
differences between the two regions. In this paper we first show that the
"sound-speed" difference obtained from inversions is actually a combination of
sound-speed difference and a magnetic component. Hence, the inversion result is
not directly related to the thermal structure. Next, using solar models that
include magnetic fields, we develop a formulation to use the inversion results
to infer the differences in the magnetic and thermal structures between active
and quiet regions. We then apply our technique to existing structure inversion
results for different pairs of active and quiet regions. We find that the
effect of magnetic fields is strongest in a shallow region above 0.985R_sun and
that the strengths of magnetic-field effects at the surface and in the deeper
(r < 0.98R_sun) layers are inversely related, i.e., the stronger the surface
magnetic field the smaller the magnetic effects in the deeper layers, and vice
versa. We also find that the magnetic effects in the deeper layers are the
strongest in the quiet regions, consistent with the fact that these are
basically regions with weakest magnetic fields at the surface. Because the
quiet regions were selected to precede or follow their companion active
regions, the results could have implications about the evolution of magnetic
fields under active regions.


title: First nonlinear force-free field extrapolations of SOLIS/VSM data

abstract:
  We study the coronal magnetic field structure inside active regions and its
temporal evolution. We attempt to compare the magnetic configuration of an
active region in a very quiet period with that for the same region during a
flare. Probably for the first time, we use vector magnetograph data from the
Synoptic Optical Long-term Investigations of the Sun survey (SOLIS) to model
the coronal magnetic field as a sequence of nonlinear force-free equilibria. We
study the active region NOAA 10960 observed on 2007 June 7 with three snapshots
taken during a small C1.0 flare of time cadence 10 minutes and six snapshots
during a quiet period. The total magnetic energy in the active region was
approximately $3 \times 10^{25}$ J. Before the flare the free magnetic energy
was about 5% of the potential field energy. A part of this excess energy was
released during the flare, producing almost a potential configuration at the
beginning of the quiet period. During the investigated period, the coronal
magnetic energy was only a few percent higher than that of the potential field
and consequently only a small C1.0 flare occurred. This was compared with an
earlier investigated active region 10540, where the free magnetic energy was
about 60% higher than that of the potential field producing two M-class flares.
However, the free magnetic energy accumulates before and is released during the
flare which appears to be the case for both large and small flares.


title: Smoking Guns for On-Shell New Physics at the LHC

abstract:
  Using Tevatron bounds we derive upper limits on the LHC Higgs production rate
under the assumption that no beyond the Standard Model (BSM) particles are
being produced near their mass shell. A violation of these limits would
constitute a smoking gun for light BSM particles. Furthermore, we demonstrate
how R_T, the ratio of the partially integrated Higgs transverse momentum
distribution to the inclusive rate, can also be used as a probe of light BSM
particles. This ratio is insensitive to heavy virtual effects and can be
well-approximated by its SM value, i.e. it is model independent. The
perturbative expansion for R_T has reduced renormalization scale dependence, at
the order of 5% at next-to-leading order in QCD, due to a cancellation of
Wilson coefficients. A deviation from the SM value implies that light BSM
particles are being produced near their mass shell. We discuss a possible
loophole to this conclusion, namely the existence of a non-perturbative, CP
violating sector that couples to the Higgs. We use a toy model with colored
scalars to demonstrate how the model independent prediction for R_T is
approached as the mass of the scalar becomes large.


title: Galaxies in a simulated $\Lambda$CDM Universe I: cold mode and hot cores

abstract:
  We study the formation of galaxies in a (50 Mpc/h)^3 cosmological simulation
(2x288^3 particles), evolved using the entropy conserving SPH code Gadget-2.
Most of the baryonic mass in galaxies of all masses is originally acquired
through filamentary "cold mode" accretion of gas that was never shock heated to
its halo virial temperature, confirming the key feature of our earlier results
obtained with a different SPH code (Keres et al. 2005). Atmospheres of hot,
virialized gas develop in halos above ~2.5e11 Msun, a transition mass that is
nearly constant from z=3 to z=0. Cold accretion persists in halos above the
transition mass, especially at z>=2. It dominates the growth of galaxies in low
mass halos at all times, and it is the main driver of the cosmic star formation
history. Satellite galaxies have accretion rates similar to central galaxies of
the same baryonic mass at high redshifts, but they have less accretion than
comparable central galaxies at low redshift. Relative to our earlier results,
the Gadget-2 simulations predict much lower rates of "hot mode" accretion from
the virialized gas component of massive halos. At z<=1, typical hot accretion
rates in halos above 5e12 Msun are below 1 Msun/yr, even though our simulation
does not include AGN heating or other forms of "preventive" feedback. The inner
density profiles of hot gas in these halos are shallow, with long associated
cooling times. The cooling recipes typically used in semi-analytic models can
overestimate the accretion rates in these halos by orders of magnitude, so such
models may overemphasize the role of preventive feedback in producing observed
galaxy masses and colors. A fraction of the massive halos develop cuspy
profiles and significant cooling rates between z=1 and z=0, a redshift trend
similar to the observed trend in the frequency of cooling flow clusters.


title:
Multivariate Jacobi and Laguerre polynomials, infinite-dimensional
  extensions, and their probabilistic connections with multivariate Hahn and
  Meixner polynomials

abstract:
  Multivariate versions of classical orthogonal polynomials such as Jacobi,
Hahn, Laguerre and Meixner are reviewed and their connection explored by
adopting a probabilistic approach. Hahn and Meixner polynomials are interpreted
as posterior mixtures of Jacobi and Laguerre polynomials, respectively. By
using known properties of gamma point processes and related transformations, a
new infinite-dimensional version of Jacobi polynomials is constructed with
respect to the size-biased version of the Poisson--Dirichlet weight measure and
to the law of the gamma point process from which it is derived.


title:
Black hole mass measurements using ionized gas discs: systematic dust
  effects

abstract:
  Using detailed Monte Carlo radiative transfer simulations in realistic models
for galactic nuclei, we investigate the influence of interstellar dust in
ionized gas discs on the rotation curves and the resulting black hole mass
measurements. We find that absorption and scattering by interstellar dust
leaves the shape of the rotation curves basically unaltered, but slightly
decreases the central slope of the rotation curves. As a result, the "observed"
black hole masses are systematically underestimated by some 10 to 20% for
realistic optical depths. We therefore argue that the systematic effect of dust
attenuation should be taken into account when estimating SMBH masses using
ionized gas kinematics.


title: Isoparametric and Dupin Hypersurfaces

abstract:
  A hypersurface $M^{n-1}$ in a real space-form ${\bf R}^n$, $S^n$ or $H^n$ is
isoparametric if it has constant principal curvatures. For ${\bf R}^n$ and
$H^n$, the classification of isoparametric hypersurfaces is complete and
relatively simple, but as Elie Cartan showed in a series of four papers in
1938-1940, the subject is much deeper and more complex for hypersurfaces in the
sphere $S^n$. A hypersurface $M^{n-1}$ in a real space-form is proper Dupin if
the number $g$ of distinct principal curvatures is constant on $M^{n-1}$, and
each principal curvature function is constant along each leaf of its
corresponding principal foliation. This is an important generalization of the
isoparametric property that has its roots in nineteenth century differential
geometry and has been studied effectively in the context of Lie sphere
geometry. This paper is a survey of the known results in these fields with
emphasis on results that have been obtained in more recent years and discussion
of important open problems in the field.


title:
Correlations among the properties of galaxies found in a blind HI
  survey, which also have SDSS optical data

abstract:
  We have used the Parkes Multibeam system and the Sloan Digital Sky Survey
(SDSS) to assemble a sample of 195 galaxies selected originally from their HI
signature to avoid biases against unevolved or low surface brightness objects.
For each source 9 intrinsic properties are measured homogeneously, as well as
inclination and an optical spectrum. The sample, which should be almost
entirely free of either misidentification or confusion, includes a wide
diversity of galaxies ranging from inchoate, low surface brightness dwarfs to
giant spirals. Despite this diversity there are 5 clear correlations among
their properties. They include a common dynamical mass-to-light ratio within
their optical radii, a correlation between surface-brightness and Luminosity
and a common HI surface-density. Such correlation should provide strong
constrains on models of galaxy formation and evolution.


title:
High Precision Radial Velocity Measurements in the Infrared: A First
  Assessment of the RV Stability of CRIRES

abstract:
  High precision radial velocity (RV) measurements in the near infrared are on
high demand, especially in the context of exoplanet search campaigns shifting
their interest to late type stars in order to detect planets with ever lower
mass or targeting embedded pre-main-sequence objects.
  ESO is offering a new spectrograph at the VLT -- CRIRES -- designed for high
resolution near-infrared spectroscopy with a comparably broad wavelength
coverage and the possibility to use gas-cells to provide a stable RV
zero-point.
  We investigate here the intrinsic short-term RV stability of CRIRES, both
with gas-cell calibration data and on-sky measurements using the absorption
lines of the Earth's atmosphere imprinted in the source spectrum as a local RV
rest frame. Moreover, we also investigate for the first time the intrinsic
stability of telluric lines at 4100 nm for features originating in the lower
troposphere.
  Our analysis of nearly 5 hours of consecutive observations of MS Vel, a M2II
bright giant centred at two SiO first overtone band-heads at 4100 nm,
demonstrates that the intrinsic short-term stability of CRIRES is very high,
showing only a slow and fully compensateable drift of up to 60 m/s after 4.5
hours. The radial velocity of the telluric lines is constant down to a level of
approx. +/- 10 m/s (or 7/1000 of one pixel). Utilising the same telluriclines
as a rest frame for our radial velocity measurements of the science target, we
obtain a constant RV with a precision of approx. +/- 20 m/s for MS Vel as
expected for a M-giant.


title:
A Large-Area Search for Low-Mass Objects in Upper Scorpius II: Age and
  Mass Distributions

abstract:
  We present continued results from a wide-field, ~150 deg^2, optical
photometric and spectroscopic survey of the northern part of the ~5 Myr-old
Upper Scorpius OB Association. Photometry and spectral types were used to
derive effective temperatures and luminosities and place newly identified
association members onto a theoretical Hertzsprung-Russell diagram. From our
survey, we have discovered 145 new low mass members of the association, and
determined ~10% of these objects to be actively accreting material from a
surrounding circumstellar disk. Based on comparison of the spatial
distributions of low and high mass association members, we find no evidence for
spatial segregation by mass within the northern portion of the association.
Measured data are combined with pre-main sequence evolutionary models to derive
a mass and age for each star. Using Monte Carlo simulations we show that,
taking into account known observational uncertainties, the observed age
dispersion for the low mass population in USco is consistent with all stars
forming in a single burst ~5 Myr ago, and place an upper limit of +/-3 Myr on
the age spread if the star formation rate has been constant in time. We derive
the first spectroscopic mass function for USco that extends into the substellar
regime, and compare these results to those for three other young clusters and
associations.


title:
How applicable is Python as first computer language for teaching
  programming in a pre-university educational environment, from a teacher's
  point of view?

abstract:
  This project report attempts to evaluate the educational properties of the
Python computer language, in practice. This is done by examining computer
language evolution history, related scientific background work, the existing
educational research on computer languages and Python's experimental
application in higher secondary education in Greece, during first half of year
2002. This Thesis Report was delivered in advance of a thesis defense for a
Masters/Doctorandus (MSc/Drs) title with the Amstel Institute/Universiteit van
Amsterdam, during the same year.


title:
Formation and Dynamical Evolution of Multiple Stellar Generations in
  Globular Clusters

abstract:
  Some globular clusters are observed to host a population of second generation
(SG) stars which show chemical anomalies and must have formed from gas
containing matter processed in the envelopes of first generation (FG) cluster
stars. We study the SG formation process by means of 1D hydrodynamical
simulations, assuming that the SG is formed by the gas ejected by AGB stars.
This gas collects in a cooling flow into the cluster core, where it forms a SG
star subsystem strongly concentrated in the cluster innermost regions with
structural properties largely independent of the FG initial properties. We also
present the results of a model in which pristine gas contributes to the SG
formation. In this model a very helium-rich SG population and one with a
moderate helium enrichment form; the resulting SG bimodal helium distribution
resembles that observed for SG stars in NGC 2808. By means of N-body
simulations, we study the two-population cluster dynamical evolution. In our
simulations, a large fraction of FG stars are lost early in the cluster
evolution due to the expansion and stripping of the cluster outer layers
resulting from early mass loss associated with FG SN ejecta. The SG population
is largely unscathed by this early mass loss, and this early evolution leads to
values of the SG to FG number ratio consistent with observations. We also
demonstrate possible evolutionary routes leading to the loss of most of the FG
population, leaving an SG-dominated cluster. Until mixing of the two
populations is complete, the radial profile of the SG to FG number ratio is
characterized by a flat inner part and a declining portion in the outer cluster
regions. (abridged)


title: Phase-Space Density Profiles in Scale-Free Cosmologies

abstract:
  We use a set of high-resolution simulations of scale-free Einstein-de Sitter
cosmologies to investigate the logarithmic slope of the phase-space density
profile $Q(r) = \rho(r)/\sigma^3(r)$ of dark matter (DM) haloes. The initial
conditions for the simulations are determined by a power law power spectrum of
the form $P(k) \propto k^n$. We compute the Q(r) profiles using the radial,
tangential and full velocity dispersion, and the velocity anisotropy parameter,
$\beta(r)$. We express Q(r) as a single power-law $Q(r) \propto r^\alpha$ and
derive a median slope $\alpha$ in each simulation and for each definition of Q.
Our main findings are: 1. The various Q(r) profiles follow a power law to a
good approximation. 2. The slopes depend on the concentration parameter c of
the DM haloes, where for $c \gtrsim 10$ the slopes steepen with rising
concentration and for $c \lesssim 10$ the trend flattens and even turns around.
3. The asymptotic value of $\beta$ as $r\to R_{\mathrm{vir}}$ increases with
the value of c. 4. In accordance with Zait et al. 2007 $\alpha_{\mathrm{rad}}$
becomes more negative as the asymptotic value of $\beta$ at the virial radius
increases. 5. This introduces a weak dependence of the $Q(r)$ slopes on the
slope of the power spectrum.


title: Brane Tilings and M2 Branes

abstract:
  Brane tilings are efficient mnemonics for Lagrangians of N=2
Chern-Simons-matter theories. Such theories are conjectured to arise on
M2-branes probing singular toric Calabi-Yau fourfolds. In this paper, a simple
modification of the Kasteleyn technique is described which is conjectured to
compute the three dimensional toric diagram of the non-compact moduli space of
a single probe. The Hilbert Series is used to compute the spectrum of
non-trivial scaling dimensions for a selected set of examples.


title: F-term uplifting and the supersymmetric integration of heavy moduli

abstract:
  We study in detail the stability properties of the simplest F-term uplifting
mechanism consistent with the integration of heavy moduli. This way of
uplifting vacua guarantees that the interaction of the uplifting sector with
the moduli sector is consistent with integrating out the heavy fields in a
supersymmetric way. The interactions between light and heavy fields are
characterized in terms of the Kahler invariant function, G = K + log |W|^2,
which is required to be separable in the two sectors. We generalize earlier
results that when the heavy fields are stabilized at a minimum of the Kahler
function G before the uplifting (corresponding to stable AdS maxima of the
potential), they remain in a perturbatively stable configuration for
arbitrarily high values of the cosmological constant (or the Hubble parameter
during inflation). By contrast, supersymmetric minima and saddle points of the
scalar potential are always destabilized for sufficiently large amount of
uplifting. We prove that these results remain unchanged after including gauge
couplings in the model. We also show that in more general scenarios, where the
Kahler function is not separable in the light and heavy sectors, the minima of
the Kahler function still have better stability properties at large uplifting
than other types of critical points.


title: Twistor-inspired construction of massive quark amplitudes

abstract:
  The analog of the Cachazo-Svrvcek-Witten rules for scattering amplitudes with
massive quarks is derived following an approach previously employed for
amplitudes with massive scalars. A prescription for the external wave-functions
is given that leads to a one-to one relation between fields in the action and
spin-states of massive quarks. Several examples for the application of the
rules are given and the structure of some all-multiplicity amplitudes with a
pair of massive quarks is discussed. The rules make supersymmetric relations to
amplitudes with massive scalars manifest at the level of the action. The
formalism is extended to several quark flavors with different masses.


title: Candidate AGNs in Late-Type Galaxies

abstract:
  We have assembled a sample of 64 late-type spiral galaxies (T types 6.0-9.0,
corresponding to Hubble types Scd-Sm) with archival Chandra data. At a
signal-to-noise (S/N) threshold of 3, we find 12 objects with X-ray
point-source detections in close proximity with the optical or near-infrared
position of the nucleus (median offset \delta = 1.6"), suggestive of possible
low-luminosity active galactic nuclei (AGNs). Including measurements with 3 >
S/N > 1.5, our detections increase to 18. These X-ray sources range in
luminosity from L_X(2-10 keV) = 10^{37.1} to 10^{39.6} ergs s^-1. Considering
possible contamination from low-mass X-ray binaries (LMXBs), we estimate that
~5 detections are possible LMXBs instead of true AGNs, based on the probability
of observing a LMXB in a nuclear star cluster typically found in these
late-type spiral galaxies. Given the typical ages of nuclear star clusters,
contamination by high-mass X-ray binaries is unlikely. This AGN fraction is
higher than that observed in optical surveys, indicating that active nuclei,
and hence central black holes, are more common than previously suggested. The
incidence of AGN activity in such late-type spiral galaxies also suggests that
nuclear massive black holes can form and grow in galaxies with little or no
evidence for bulges. Follow-up multiwavelength observations will be necessary
to confirm the true nature of these sources.


title: Solar Activity: Triennial Report of IAU Commission 10 (2006-2009)

abstract:
  Commission 10 deals with solar activity in all of its forms, ranging from the
smallest nanoflares to the largest coronal mass ejections. This report reviews
scientific progress over the roughly two-year period ending in the middle of
2008. This has been an exciting time in solar physics, highlighted by the
launches of the Hinode and STEREO missions late in 2006. The report is
reasonably comprehensive, though it is far from exhaustive. Limited space
prevents the inclusion of many significant results. The report is divided into
the following sections: Photosphere and Chromosphere; Transition Region; Corona
and Coronal Heating; Coronal Jets; Flares; Coronal Mass Ejection Initiation;
Global Coronal Waves and Shocks; Coronal Dimming; The Link Between Low Coronal
CME Signatures and Magnetic Clouds; Coronal Mass Ejections in the Heliosphere;
and Coronal Mass Ejections and Space Weather. Primary authorship is indicated
at the beginning of each section.


title:
Three-Dimensional two-pion source image from Pb+Pb Collisions at
  Sqrts_NN=17.3 GeV: New constraints for source breakup dynamics

abstract:
  Source imaging methodology is used to provide a three-dimensional two-pion
source function for mid-rapidity pion pairs with $p_T<70$ MeV/c in central
($0-7%$) Pb+Pb collisions at $\sqrt s_{NN}$=17.3 GeV. Prominent non-Gaussian
tails are observed in the pion pair transverse momentum (outward) and in the
beam (longitudinal) directions. Model calculations reproduce them with the
assumption of Bjorken longitudinal boost invariance and transverse flow
blast-wave dynamics coupled with "outside-in burning" in the transverse
direction; they also yield a proper time for breakup and emission duration for
the pion source.


title:
Decoherence and Irreversibility: the role of the reservoir effective
  Hilbert space size

abstract:
  We show that decoherence is determined by the effective Hilbert space size,
and demonstrate that a few degrees of freedom system can simulate a "N" degrees
of freedom environment if they have the same effective Hilbert space. The
effective Hilbert space size of the environment also determines its long time
efficiency as generator of irreversible coherence loss.


title: Pixelization and Dynamic Range in Radio Interferometry

abstract:
  This study investigates some of the consequences of representing the sky by a
rectangular grid of pixels on the dynamic range of images derived from radio
interferometric measurements. In particular, the effects of image pixelization
coupled to the CLEAN deconvolution representation of the sky as a set of
discrete delta functions can limit the dynamic range obtained when representing
bright emission not confined to pixels on the grid. Sky curvature effects on
non-coplanar arrays will limit the dynamic range even if strong sources are
centered on a pixel in a "fly's eye" representation when such pixel is not
located at the corresponding facet's tangent point. Uncertainties in the
response function of the individual antennas as well as in the calibration of
actual data due to ionospheric, atmospheric or other effects will limit the
dynamic range even when using grid-less subtraction (i.e. in the visibility
domain) of strong sources located within the field of view of the observation.
A technique to reduce these effects is described and examples from an
implementation in the Obit package are given. Application of this technique
leads to significantly superior results without a significant increase in the
computing time.


title:
Beyond mean field effects in the high momentum energy spectrum of a Bose
  gas: revisiting Beliaev's theory

abstract:
  The well-known Bogoliubov expression for the spectrum of a weakly interacting
dilute Bose gas becomes inadequate when the density or interactions strength
are increased. The corrections to the spectrum due to stronger interactions
were first considered by Beliaev (S. T. Beliaev, Sov. Phys.-JETP, 7:289,
(1958)). We revisit Beliaev's theory and consider its application to a dilute
gas with van der Waals interactions, where the scattering length may be tuned
via a Fano-Feshbach resonance. We numerically evaluate Beliaev's expression for
the excitation spectrum in the intermediate momentum regime, and we also
examine the consequences of the momentum dependence of the two-body scattering
amplitude.These results are relevant to the interpretation of a recent Bragg
spectroscopy experiment of a strongly interacting Bose gas.


title:
Applicability of the Linear delta Expansion for the lambda phi^4 Field
  Theory at Finite Temperature in the Symmetric and Broken Phases

abstract:
  The thermodynamics of a scalar field with a quartic interaction is studied
within the linear delta expansion (LDE) method. Using the imaginary-time
formalism the free energy is evaluated up to second order in the LDE. The
method generates nonperturbative results that are then used to obtain
thermodynamic quantities like the pressure. The phase transition pattern of the
model is fully studied, from the broken to the symmetry restored phase. The
results are compared with those obtained with other nonperturbative methods and
also with ordinary perturbation theory. The results coming from the two main
optimization procedures used in conjunction with the LDE method, the Principle
of Minimal Sensitivity (PMS) and the Fastest Apparent Convergence (FAC) are
also compared with each other and studied in which cases they are applicable or
not. The optimization procedures are applied directly to the free energy.

categories: hep-ph cond-mat.stat-mech hep-th nucl-th


title: The Relative Burnside Kernel - The Elementary Abelian Case

abstract:
  We give a conjectural description for the kernel of the map assigning to each
finite $\mathbb Z_p$-free $G\times\mathbb Z_p$-set its rational permutation
module where G is a finite p-group. We prove that this conjecture is true when
G is an elementary abelian p-group or a cyclic p-group.


title: Hitchin Functionals and Nonspontaneous Supersymmetry Breaking

abstract:
  A new mechanism of supersymmetry breaking involving a dynamical parameter is
introduced. It is independent of particle phenomenology and gauge groups. An
explicit realization of this mechanism takes place in Type II superstring
compactifications which admit eight supercharges (also known as generalized
SU(3) structures). The resulting Kahler potentials are expressed in terms of
Hitchin functionals.


title: Physical Interpretation of Coordinates for the Schwarzschild Metric

abstract:
  Since its first introduction, the Schwarzschild metric has been written in
various coordinate systems. This has been done primarily to understand the
nature of the coordinate singularity at the event horizon. However, very often,
the mathematics of a coordinate system does not provide a clear physical
interpretation. In Schwarzschild's original work, the origin of the radial
coordinate was at the event horizon. Hence, there was no black hole. The
generally accepted current definition of the radial coordinate has an origin
beyond the horizon. This necessitates the discussion of black holes. Here, some
well-known and some not-so-well-known coordinate systems will be visited in
search of a physical interpretation. It will be noted that they all agree at
large radial distances. However, the location of the origin of the radial
coordinate can be different for different systems. Some "natural" coordinate
systems can exclude the entirety of the interior of a black hole from the
physical manifold. Such coordinate systems maybe physically more acceptable as
they avoid the issue of the metric signature change across the horizon.
Mathematically, the metric signature alone can distinguish time from space
coordinates. Hence, coordinate systems that include the interior of the black
hole need to switch the physical meanings of time and one of the space
coordinates.


title:
Absence of Critical Thickness in an Ultrathin Improper Ferroelectric
  Film

abstract:
  We study the ferroelectric stability and surface structural properties of an
oxygen-terminated hexagonal YMnO$_3$ ultra-thin film using density functional
theory. Under an open circuit boundary condition, the ferroelectric state with
the spontaneous polarization normal to the (0001) surface, is found to be
metastable in a single domain state despite the presence of a depolarizing
field. We establish a connection between the result and the role of improper
ferroelectric transition. Our results imply that improper ferroelectric
ultrathin films can have rather unique properties that are distinctive from
those of very thin films of ordinary ferroelectrics.


title:
Relic High Frequency Gravitational waves from the Big Bang, and How to
  Detect Them

abstract:
  We show conditions for HFGW detection, employing an entropy concept written
up by Jack Ng, and Steinhard's proceedure for reconstructing tensorial
representations for relic HFGW from the onset of the big bang. The issue of the
reality of gravitons as a measurable physical object which was raised by
Rothman in 2006 is indirectly answered via a proceedure obtained from
Weinberg's 1972 book on gravitation, and all the methodologies so obtained are
referenced with respect to engineering specifications of the Li-Baker HFGW
detector. In addition, the document also refers to entanglement entropy, and
its possible aid in refining measurement predictions. Finally, commentary about
HFGW and relic neutrino physics data sets is included, with regards to
inflationary model candidates


title:
Local dynamical lattice instabilities: Prerequisites for resonant
  pairing superconductivity

abstract:
  Fluctuating local diamagnetic pairs of electrons, embedded in a Fermi sea,
are candidates for non-phonon-mediated superconductors without the stringent
conditions on Tc which arise in phonon-mediated BCS classical low-Tc
superconductors. The local accumulations of charge, from which such diamagnetic
fluctuations originate, are irrevocably coupled to local dynamical lattice
instabilities and form composite charge-lattice excitations of the system. For
a superconducting phase to be realized, such excitations must be itinerant
spatially phase-coherent modes. This can be achieved by resonant pair tunneling
in and out of polaronic cation-ligand sites. Materials in which
superconductivity driven by such local lattice instability can be expected,
have a Tc which is controlled by the phase stiffness rather than the amplitude
of the diamagnetic pair fluctuations. Above Tc, a pseudogap phase will be
maintained up to a T*, where this pairing amplitude disappears. We discuss the
characteristic local charge and lattice properties which characterize this
pseudogap phase and which form the prerequisites for establishing a
phase-coherent macroscopic superconducting state.


title:
Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison
  to Observations of Type I Planetary Nebulae

abstract:
  Type I planetary nebulae (PNe) have high He/H and N/O ratios and are thought
to be descendants of stars with initial masses of ~3-8Msun. These
characteristics indicate that the progenitor stars experienced proton-capture
nucleosynthesis at the base of the convective envelope, in addition to the slow
neutron capture process operating in the He-shell (the s-process). We compare
the predicted abundances of elements up to Sr from models of intermediate-mass
asymptotic giant branch (AGB) stars to measured abundances in Type I PNe. In
particular, we compare predictions and observations for the light trans-iron
elements Se and Kr, in order to constrain convective mixing and the s-process
in these stars. A partial mixing zone is included in selected models to explore
the effect of a 13C pocket on the s-process yields. The solar-metallicity
models produce enrichments of [(Se, Kr)/Fe] < 0.6, consistent with Galactic
Type I PNe where the observed enhancements are typically < 0.3 dex, while lower
metallicity models predict larger enrichments of C, N, Se, and Kr. O
destruction occurs in the most massive models but it is not efficient enough to
account for the > 0.3 dex O depletions observed in some Type I PNe. It is not
possible to reach firm conclusions regarding the neutron source operating in
massive AGB stars from Se and Kr abundances in Type I PNe; abundances for more
s-process elements may help to distinguish between the two neutron sources. We
predict that only the most massive models would evolve into Type I PNe,
indicating that extra-mixing processes are active in lower-mass stars
(3-4Msun), if these stars are to evolve into Type I PNe.


title: The Inevitable Future of the Starless Core Barnard 68

abstract:
  Dense, small molecular cloud cores have been identified as the direct
progenitors of stars. One of the best studied examples is Barnard 68 which is
considered a prototype stable, spherical gas core, confined by a diffuse
high-pressure environment. Observations of its radial density structure however
indicate that Barnard 68 should be gravitationally unstable and collapsing
which appears to be inconsistent with its inferred long lifetime and stability.
We argue that Barnard 68 is currently experiencing a fatal collision with
another small core which will lead to gravitational collapse. Despite the fact
that this system is still in an early phase of interaction, our numerical
simulations imply that the future gravitational collapse is already detectable
in the outer surface density structure of the globule which mimicks the profile
of a gravitationally unstable Bonnor-Ebert sphere. Within the next 200,000
years Barnard 68 will condense into a low-mass solar-type star(s), formed in
isolation, and surrounded by diffuse, hot interstellar gas. As witnessed in
situ for Barnard 68, core mergers might in general play an important role in
triggering star formation and shaping the molecular core mass distribution and
by that also the stellar initial mass function.


title: Topological Cohen-Macaulay criteria for monomial ideals

abstract:
  Scattered over the past few years have been several occurrences of simplicial
complexes whose topological behavior characterize the Cohen-Macaulay property
for quotients of polynomial rings by arbitrary (not necessarily squarefree)
monomial ideals. The purpose of this survey is to gather the developments into
one location, with self-contained proofs, including direct combinatorial
topological connections between them.


title: ATLAS reach for Quarkonium cross section and polarization measurement

abstract:
  The ATLAS detector at CERN's LHC is preparing to take data from the first
proton-proton collisions expected in the next few months. We report on the
analysis of simulated data samples for production of heavy Quarkonium states
J/psi and Upsilon, corresponding to an integrated luminosity of 10 pb^-1 with
center of mass energy of 14 TeV expected at the early ATLAS data. We review
various aspects of prompt Quarkonium production at LHC: the accessible ranges
in transverse momentum and pseudorapidity, spin alignment of vector states,
separation of color octet and color singlet production mechanism and
feasibility of observing radiative decays Xi_c and Xi_b decays. Strategies of
various measurements are outlined and methods of separating promptly produced
J/psi and Upsilon mesons from various backgrounds are discussed.


title:
Computation of Maximal Resolution of Copy Number Variation on a
  Nanofluidic Device using Digital PCR

abstract:
  Copy Number Variations (CNVs) of regions of the human genome are important in
disease association studies.The digital array is a nanofluidic biochip which
utilizes integrated channels and valves that partition mixtures of sample and
reagents into 765 nanovolume reaction chambers. It was recently shown how one
can perform statistical analysis of CNV in a DNA sample the digital array. In
particular, it was shown how one can accurately estimate the true concentration
of the molecules in the DNA sample and then determine the ratios of different
sequences along with statistical confidence intervals on these estimations. In
this paper we perform computation of maximum number of copies which can be
distinguished using the digital array which gives its resolution in terms of
its ability to determine CNV. Then, we demonstrate the usefulness of the
mathematical analysis to solve an important real-world problem of determination
of the copy number of X chromosome as our example application.


title: The spherical Hecke algebra for affine Kac-Moody groups I

abstract:
  We define the spherical Hecke algebra for an (untwisted) affine Kac-Moody
group over a local non-archimedian field. We prove a generalization of the
Satake isomorphism for these algebras, relating it to integrable
representations of the Langlands dual affine Kac-Moody group. In the next
publication we shall use these results to define and study the notion of Hecke
eigenfunction for the group $G_{\aff}$


title:
Modified Fragmentation Function in Heavy Ion Collisions at RHIC via
  Direct photon-Jet Measurements

abstract:
  The presented results are the first measurements at RHIC for direct
$\gamma$-charged hadron azimuthal correlations in heavy ion collisions. We use
these correlations to study the color charge density of the medium through the
medium-induced modification of high-p$_T$ parton fragmentation. Azimuthal
correlations of direct photons at high transverse energy (8 $<$ p$_T$ $<$ 16
GeV) with away-side charged hadrons of transverse momentum (3 $<$ p$_T$ $<$ 6
GeV/c) have been measured over a broad range of centrality for $Au+Au$
collisions and $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV in the STAR
experiment. A transverse shower shape analysis in the STAR Barrel
Electromagnetic Calorimeter Shower Maximum Detector is used to discriminate
between the direct photons and photons from the decays of high p$_T$ $\pi^{0}$.
The per-trigger away-side yield of direct $\gamma$ is smaller than from
$\pi^{0}$ trigger at the same centrality class. Within the current uncertainty
the I$_{CP}$ of direct $\gamma$ and $\pi^{0}$ are similar.


title:
On Resolvent Identities in Gaussian Ensembles at the Edge of the
  Spectrum

abstract:
  We obtain the recursive identities for the joint moments of the traces of the
powers of the resolvent for Gaussian ensembles of random matrices at the soft
and hard edges of the spectrum. We also discuss the possible ways to extend
these results to the non-Gaussian case.


title:
Metallic and Insulating Phases of Repulsively Interacting Fermions in a
  3D Optical Lattice

abstract:
  The fermionic Hubbard model plays a fundamental role in the description of
strongly correlated materials. Here we report on the realization of this
Hamiltonian using a repulsively interacting spin mixture of ultracold $^{40}$K
atoms in a 3D optical lattice. We have implemented a new method to directly
measure the compressibility of the quantum gas in the trap using in-situ
imaging and independent control of external confinement and lattice depth.
Together with a comparison to ab-initio Dynamical Mean Field Theory
calculations, we show how the system evolves for increasing confinement from a
compressible dilute metal over a strongly-interacting Fermi liquid into a band
insulating state. For strong interactions, we find evidence for an emergent
incompressible Mott insulating phase.


title: Probabilistic Systems with LimSup and LimInf Objectives

abstract:
  We give polynomial-time algorithms for computing the values of Markov
decision processes (MDPs) with limsup and liminf objectives. A real-valued
reward is assigned to each state, and the value of an infinite path in the MDP
is the limsup (resp. liminf) of all rewards along the path. The value of an MDP
is the maximal expected value of an infinite path that can be achieved by
resolving the decisions of the MDP. Using our result on MDPs, we show that
turn-based stochastic games with limsup and liminf objectives can be solved in
NP \cap coNP.


title: Metastable Quasimolecules in Excited Gases

abstract:
  Quasimolecules, which consist of two differently excited atoms in a
resonantly excited gas, are considered. The energy of dissociation and typical
sizes of such molecules are calculated in the first order of quantum-mechanical
perturbation theory with the help of the dipole-dipole interaction operator. It
is shown that there exist metastable quasimolecules, whose dipole radiative
transition to the ground state (two non-excited atoms) is forbidden. The
lifetime of such molecules is estimated and it is shown that quasimolecules may
considerably affect the transport processes in a resonantly excited gas.


title: Hot neutron matter from a Self-Consistent Green's Functions approach

abstract:
  A systematic study of the microscopic and thermodynamical properties of pure
neutron matter at finite temperature within the Self-Consistent Green's
Function approach is performed. The model dependence of these results is
analyzed by both comparing the results obtained with two different microscopic
interactions, the CD-BONN and the Argonne V18 potentials, and by analyzing the
results obtained with other approaches, such as the Brueckner--Hartree--Fock
approximation, the variational approach and the virial expansion.


title:
Bose-Einstein condensation in an optical lattice: A perturbation
  approach

abstract:
  We derive closed analytical expressions for the order parameter $\Phi (x)$
and for the chemical potential $\mu $ of a Bose-Einstein Condensate loaded into
a harmonically confined, one dimensional optical lattice, for sufficiently
weak, repulsive or attractive interaction, and not too strong laser
intensities. Our results are compared with exact numerical calculations in
order to map out the range of validity of the perturbative analytical approach.
We identify parameter values where the optical lattice compensates the
interaction-induced nonlinearity, such that the condensate ground state
coincides with a simple, single particle harmonic oscillator wave function.


title:
Intermediate Phases, structural variance and network demixing in
  chalcogenides: the unusual case of group V sulfides

abstract:
  We review Intermediate Phases (IPs) in chalcogenide glasses and provide a
structural interpretation of these phases. In binary group IV selenides, IPs
reside in the 2.40 < r < 2.54 range, and in binary group V selenides they shift
to a lower r, in the 2.29< r < 2.40 range. Here r represents the mean
coordination number of glasses. In ternary alloys containing equal proportions
of group IV and V selenides, IPs are wider and encompass ranges of respective
binary glasses. These data suggest that the local structural variance
contributing to IP widths largely derives from four isostatic local structures
of varying connectivity r; two include group V based quasi-tetrahedral (r =
2.29) and pyramidal (r = 2.40) units, and the other two are group IV based
corner-sharing (r = 2.40) and edge-sharing (r = 2.67) tetrahedral units.
Remarkably, binary group V (P, As) sulfides exhibit IPs that are shifted to
even a lower r than their selenide counterparts; a result that we trace to
excess Sn chains either partially (As-S) or completely (P-S) demixing from
network backbone, in contrast to excess Sen chains forming part of the backbone
in corresponding selenide glasses. In ternary chalcogenides of Ge with the
group V elements (As, P), IPs of the sulfides are similar to their selenide
counterparts, suggesting that presence of Ge serves to reign in the excess Sn
chain fragments back in the backbone as in their selenide counterparts.


title:
Sign reversal of ac Josephson current in a ferromagnetic Josephson
  junction

abstract:
  The ac Josephson effect in a ferromagnetic Josephson junction, which is
composed of two superconductors separated by a ferromagnetic metal (FM), is
studied by a tunneling Hamiltonian and Green's function method. We obtain two
types of superconducting phase dependent current, i.e., Josephson current and
quasiparticle-pair-interference current (QPIC). These currents change their
signs with thickness of the FM layer due to the 0-$\pi$ transition
characteristic to the ferromagnetic Josephson junction. As a function of
applied voltage, the Josephson critical current shows a logarithmic divergence
called the Riedel peak at the gap voltage, while the QPIC shows a discontinuous
jump. The Riedel peak reverses due to the 0-$\pi$ transition and disappears
near the 0-$\pi$ transition point. The discontinuous jump in the QPIC also
represents similar behaviors to the Riedel peak. These results are in contrast
to the conventional ones.


title:
Corpos no interior de um recipiente fechado e transparente em queda
  livre

abstract:
  Neste artigo discutimos uma nova demonstracao experimental da independencia
das propriedades dos corpos (massa, composicao quimica, forma, etc.) na queda
livre. Eh uma das experiencias mais simples, porem uma das mais importantes da
Mecanica, tendo sido realizada e repensada repetidamente por diversos
cientistas tais como Galileu e Newton. Nossa versao eh introduzir dentro de uma
garrafa fechada e transparente uma pena e uma pedra observando a queda
simultanea destes corpos. Por nao haver a necessidade de produzir vacuo, esta
versao pode ser repetida por qualquer aluno e professor de ensino medio e
universitario em qualquer ambiente, evidenciando sua viabilidade e
aplicabilidade na sala de aula.
  English version of abstract: In this paper we discuss a new experimental
demonstration of the independence of the properties of bodies (mass, chemical
composition, shape, etc) in free fall. This is one of the simplest experiments
in mechanics, though one of the most important ones, having been repeatedly
carried out and rethought by several scientists such as Galileo and Newton. Our
version of this famous experiment uses one bottle (closed and transparent), in
which we introduce a feather and a stone, observing the simultaneous free fall
of these bodies. Because it is not necessary to create vacuum, this version can
be repeated by teachers and students alike either in secondary schools or
universities in any environment. Thus its viability and applicability in the
classroom is evident.


title: Coalescence of Low-Viscosity Fluids in Air

abstract:
  An electrical method is used to study the early stages of coalescence of two
low-viscosity drops. A drop of aqueous NaCl solution is suspended in air above
a second drop of the same solution which is grown until the drops touch. At
that point a rapidly widening bridge forms between them. By measuring the
resistance and capacitance of the system during this coalescence event, one can
obtain information about the time dependence of the characteristic bridge
radius and its characteristic height. At early times, a new asymptotic regime
is observed that is inconsistent with previous theoretical predictions. The
measurements at several drop radii and approach velocities are consistent with
a model in which the two liquids coalesce with a slightly deformed interface.


title: Parametric k-best alignment

abstract:
  Optimal sequence alignments depend heavily on alignment scoring parameters.
Given input sequences, {\em parametric alignment} is the well-studied problem
that asks for all possible optimal alignment summaries as parameters vary, as
well as the {\em optimality region} of alignment scoring parameters which yield
each optimal alignment. But biologically correct alignments might be {\em
suboptimal} for all parameter choices. Thus we extend parametric alignment to
{\em parametric $k$-best alignment}, which asks for all possible $k$-tuples of
$k$-best alignment summaries $(s_1, s_2, ..., s_k)$, as well as the {\em
$k$-best optimality region} of scoring parameters which make $s_1, s_2, ...,
s_k$ the top $k$ summaries. By exploiting the integer-structure of alignment
summaries, we show that, astonishingly, the complexity of parametric $k$-best
alignment is only polynomial in $k$. Thus parametric $k$-best alignment is
tractable, and can be applied at the whole-genome scale like parametric
alignment.


title:
Doping and Temperature Dependence of Raman Scattering of NdFeAsO1-xFx
  (x=0.0, 0.1, 0.2) Superconductor

abstract:
  Raman spectra of polycrystalline NdFeAsO1-xFx (x=0.0, 0.1, 0.2) compound have
been systematically investigated as functions of temperature and fluorine
concentration. Scanning electron microscopic and Raman microscopic
characterization demonstrates that the polycrystalline samples mainly contain
two phases, i.e. superconductor NdFeAsO1-xFx compound and a MnP-type FeAs
phase, with dissimilar characteristic Raman bands. It was found that fluorine
doping leads to structure disorder in the insulator Nd-O layers and high
temperature coefficient of Fe-As vibrational mode.


title: Photo-induced Tomonaga-Luttinger-like liquid in a Mott insulator

abstract:
  Photo-induced metallic states in a Mott insulator are studied for the
half-filled, one-dimensional Hubbard model with the time-dependent density
matrix renormalization group. An irradiation of strong AC field is found to
create a linear dispersion in the optical spectrum (current-current
correlation) in the nonequilibrium steady state reminiscent of the
Tomonaga-Luttinger liquid for the doped Mott insulator in equilibrium. The spin
spectrum in nonequilibrium retains the des Cloizeaux-Pearson mode with the spin
velocity differing from the charge velocity. The mechanism of the
photocarrier-doping, along with the renormalization in the charge velocity, is
analyzed in terms of an effective Dirac model.


title: Obtaining Exact Interpolation Multivariate Polynomial by Approximation

abstract:
  In some fields such as Mathematics Mechanization, automated reasoning and
Trustworthy Computing etc., exact results are needed. Symbolic computations are
used to obtain the exact results. Symbolic computations are of high complexity.
In order to improve the situation, exactly interpolating methods are often
proposed for the exact results and approximate interpolating methods for the
approximate ones. In this paper, we study how to obtain exact interpolation
polynomial with rational coefficients by approximate interpolating methods.


title:
Quantum Critical Point at Finite Doping in the 2D Hubbard Model: A
  Dynamical Cluster Quantum Monte Carlo Study

abstract:
  We explore the Matsubara quasiparticle fraction and the pseudogap of the
two-dimensional Hubbard model with the dynamical cluster quantum Monte Carlo
method. The character of the quasiparticle fraction changes from non-Fermi
liquid, to marginal Fermi liquid to Fermi liquid as a function of doping,
indicating the presence of a quantum critical point separating non-Fermi liquid
from Fermi liquid character. Marginal Fermi liquid character is found at low
temperatures at a very narrow range of doping where the single-particle density
of states is also symmetric. At higher doping the character of the
quasiparticle fraction is seen to cross over from Fermi Liquid to Marginal
Fermi liquid as the temperature increases.


title:
Value of interparticle interaction potential as a variable in solving
  many-body Schr\"{o}dinger equation

abstract:
  A many-body wave function is approximated by a product of two functions: the
wave function $\phi$ depending on the particle coordinates and the function
$\chi$ depending only on the value of interparticle interaction potential. For
the given $\phi$ an ordinary linear differential equation for $\chi$ is derived
by averaging the Hamiltonian over the constant interparticle interaction
potential surface. Generalized Hartree-Fock equations containing correlation
effects are obtained. To test the proposed technique the ground $1^{1}S_0$ and
excited $2^{3}S_1$ states of two-electron ions from H$^-$ up to Ne$^{8+}$ are
calculated. In all cases the calculated energies are more accurate than those
obtained with the Hartree-Fock theory even taking as $\phi$ the symmetrized
product of electron wave functions in the Coulomb field of nucleus complitly
disregarded the electron-electron interaction. Variation of factors in the
one-particle wave function exponents leads to the results close to those of
configuration interaction approach.


title: Random mobility and spatial structure often enhance cooperation

abstract:
  The effects of an unconditional move rule in the spatial Prisoner's Dilemma,
Snowdrift and Stag Hunt games are studied. Spatial structure by itself is known
to modify the outcome of many games when compared with a randomly mixed
population, sometimes promoting, sometimes inhibiting cooperation. Here we show
that random dilution and mobility may suppress the inhibiting factors of the
spatial structure in the Snowdrift game, while enhancing the already larger
cooperation found in the Prisoner's dilemma and Stag Hunt games.


title:
Black hole complementarity with local horizons and Horowitz-Maldacena's
  proposal

abstract:
  To implement the consistent black hole complementarity principle, we need two
assumptions: first, there exists a singularity near the center, and second,
global horizons are the same as local horizons. However, these assumptions are
not true in general. In this paper, the authors study a charged black hole in
which the second assumption may not hold. From the previous simulations, we
have argued that the event horizon is quite close to the outer horizon, and it
seems not harmful to black hole complementarity; however, the Cauchy horizon
can be different from the inner horizon, and a violation of complementarity
will be possible. To maintain complementarity, we need to assume a selection
principle between the singularity and the Hawking radiation generating surface;
we suggest that Horowitz-Maldacena's proposal can be useful for this purpose.
Finally, we discussed some conditions under which the selection principle may
not work.


title:
Vertex Corrections and the Korringa Ratio in Strongly Correlated
  Electron Materials

abstract:
  We show that the Korringa ratio, associated with nuclear magnetic resonance
in metals, is unity if vertex corrections for the dynamic spin susceptibility
are negligible and the hyperfine coupling is momentum independent. In the
absence of vertex corrections we also find a Korringa behaviour for $T_1$, the
nuclear spin relaxation rate, i.e., $1/T_1\propto T$, and a temperature
independent Knight shift. These results are independent of the form and
magnitude of the self-energy (so far as is consistent with neglecting vertex
corrections) and of the dimensionality of the system.