title: Contact resistance and shot noise in graphene transistors

abstract:
  Potential steps naturally develop in graphene near metallic contacts. We
investigate the influence of these steps on the transport in graphene Field
Effect Transistors. We give simple expressions to estimate the
voltage-dependent contribution of the contacts to the total resistance and
noise in the diffusive and ballistic regimes.


title: Hyperbolicity of Semigroup Algebras II

abstract:
  In 1996 Jespers and Wang classified finite semigroups whose integral
semigroup ring has finitely many units. In a recent paper, Iwaki-Juriaans-Souza
Filho continued this line of research by partially classifying the finite
semigroups whose rational semigroup algebra %over a field of characteristic
zero, contains a ${\mathbb{Z}}$-order with hyperbolic unit group. In this paper
we complete this classification by handling the case in which the semigroup is
semi-simple.


title:
Detection of Hard X-Rays from the Compton-Thick Seyfert 2 Galaxy NGC
  2273 with Suzaku

abstract:
  We have obtained a broad-band spectrum of the Compton-thick Seyfert 2 galaxy
NGC 2273 with Suzaku. The spectrum reveals the first detection of hard X-rays
above ~10 keV from NGC 2273. The broad-band spectrum is well represented by a
three-component model, accompanied by both a strong iron Ka line with an
equivalent width of ~ 1.8 keV and several weak lines. The three-component model
consists of a soft component, a reflection component from cold matter, and an
absorbed power-law component. The soft component can be represented by thin
thermal emission with kT~0.56 keV or by a scattered component with a scattering
fraction of 0.4%. Fixing the photon indices of the power law and reflection
components at 1.9, we found that the power law component, heavily absorbed by
gas with a column density of ~1.5x10^24 cm^-2, has an intrinsic 2-10 keV
luminosity of ~1.7x10^42 erg/s. We also apply a reflection model based on a
Monte Carlo simulation, assuming a simple torus geometry. We found that the
model fits the broad band spectrum well, and we place some tentative
constraints on the geometry of the putative torus in NGC2273.


title: Smoothness and jet schemes

abstract:
  This paper shows some criteria for a scheme of finite type over an
algebraically closed field to be non-singular in terms of jet schemes.
  For the base field of characteristic zero, the scheme is non-singular if and
only if one of the truncation morphisms of its jet schemes is flat. For the
positive characteristic case, we obtain a similar characterization under the
reducedness condition on the scheme. We also obtain by a simple discussion that
the scheme is non-singular if and only if one of its jet schemes is
non-singular.


title:
Stellar spectropolarimetry with HiVIS: Herbig Ae/Be stars, circumstellar
  environments and optical pumping

abstract:
  The polarization of light across spectral lines contains information about
the circumstellar material on small spatial scales. Many models relate the
circumstellar environment to observable polarization changes across spectral
lines. However, measuring signals at the 0.1% level requires a very careful
control of systematic effects.
  We have recently built a high-resolution spectropolarimeter for the HiVIS
spectrograph on the 3.67m AEOS telescope and have obtained a large number of
high precision spectropolarimetric observations of Herbig Ae/Be, Classical Be
and other stars. The detected linear polarization varies from our typical
detection threshold near 0.1% up to 2%. This polarization effect is generally
not coincident with the H-alpha emission peak but is detected only in the
absorptive part of the line profile and varies with the absorption. These
detections are largely inconsistent with the traditional scattering models and
inspired a new explanation of their polarization.
  We developed a new spectropolarimetric model and argue that polarization in
absorption is evidence of optical pumping. We argue that, while scattering
theory fits many Be and emission-line star observations, this new theory has
much more potential to explain polarization-in-absorption as seen in Herbig
Ae/Be and other stellar systems.
  This thesis presents a large spectropolarimetric study that combines new
instrumentation, custom processing software, thorough calibrations,
cross-instrument comparisons, a massive observing campaign on many targets,
comparison of current theories on multiple objects and finally the creation of
a new theory.


title: Dark Matter in B-L Extended MSSM Models

abstract:
  We analyze the dark matter problem in the context of supersymmetric
U(1)_{B-L} model. In this model, the lightest neutalino can be the B-L gaugino
widetilde {Z}_{B-L} or the extra Higgsinos widetilde{chi}_{1,2} dominated. We
compute the thermal relic abundance of these particles and show that, unlike
the LSP in MSSM, they can account for the observed relic abundance with no
conflict with other phenomenological constraints. The prospects for their
direct detection, if they are part of our galactic halo, are also discussed.


title: Late Time Decay of the False Vacuum, Measurement, and Quantum Cosmology

abstract:
  The recent suggestion that late time quantum dynamics may be important for
resolving cosmological issues associated with our observed universe requires a
consideration of several subtle issues associated with quantum cosmology, as we
describe here. The resolution of these issues will be important if we are to be
able to properly ascribe probability measures associated with eternal
inflation, and a string landscape.


title: A slowly accreting ~10 Myr old transitional disk in Orion OB1a

abstract:
  Here we present the Spitzer IRS spectrum of CVSO 224, the sole transitional
disk located within the ~10 Myr old 25 Orionis group in Orion OB1a. A model fit
to the spectral energy distribution of this object indicates a ~7 AU inner disk
hole that contains a small amount of optically thin dust. In previous studies,
CVSO 224 had been classified as a weak-line T Tauri star based on its Halpha
equivalent width, but here we find an accretion rate of 7x10^-11 Msun/yr based
on high-resolution Hectochelle data. CVSO 224's low mass accretion rate is in
line with photoevaporative clearing theories. However, the Spitzer IRS spectrum
of CVSO 224 has a substantial mid-infrared excess beyond 20microns which
indicates that it is surrounded by a massive outer disk. Millimeter
measurements are necessary to constrain the mass of the outer disk around CVSO
224 in order to confirm that photoevaporation is not the mechanism behind
creating its inner disk hole.


title:
New Constructions for Query-Efficient Locally Decodable Codes of
  Subexponential Length

abstract:
  A $(k,\delta,\epsilon)$-locally decodable code $C: F_{q}^{n} \to F_{q}^{N}$
is an error-correcting code that encodes each message
$\vec{x}=(x_{1},x_{2},...,x_{n}) \in F_{q}^{n}$ to $C(\vec{x}) \in F_{q}^{N}$
and has the following property: For any $\vec{y} \in {\bf F}_{q}^{N}$ such that
$d(\vec{y},C(\vec{x})) \leq \delta N$ and each $1 \leq i \leq n$, the symbol
$x_{i}$ of $\vec{x}$ can be recovered with probability at least $1-\epsilon$ by
a randomized decoding algorithm looking only at $k$ coordinates of $\vec{y}$.
The efficiency of a $(k,\delta,\epsilon)$-locally decodable code $C: F_{q}^{n}
\to F_{q}^{N}$ is measured by the code length $N$ and the number $k$ of
queries. For any $k$-query locally decodable code $C: F_{q}^{n} \to F_{q}^{N}$,
the code length $N$ is conjectured to be exponential of $n$, however, this was
disproved. Yekhanin [In Proc. of STOC, 2007] showed that there exists a 3-query
locally decodable code $C: F_{2}^{n} \to F_{2}^{N}$ such that
$N=\exp(n^{(1/\log \log n)})$ assuming that the number of Mersenne primes is
infinite. For a 3-query locally decodable code $C: F_{q}^{n} \to F_{q}^{N}$,
Efremenko [ECCC Report No.69, 2008] reduced the code length further to
$N=\exp(n^{O((\log \log n/ \log n)^{1/2})})$, and also showed that for any
integer $r>1$, there exists a $k$-query locally decodable code $C: F_{q}^{n}
\to F_{q}^{N}$ such that $k \leq 2^{r}$ and $N=\exp(n^{O((\log \log n/ \log
n)^{1-1/r})})$. In this paper, we present a query-efficient locally decodable
code and show that for any integer $r>1$, there exists a $k$-query locally
decodable code $C: F_{q}^{n} \to F_{q}^{N}$ such that $k \leq 3 \cdot 2^{r-2}$
and $N=\exp(n^{O((\log \log n/ \log n)^{1-1/r})})$.


title:
Periodicities in the high-mass X-ray binary system RX J0146.9+6121/LS
  I+61 235

abstract:
  The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61
235 (V831 Cas), is an intriguing system on the outskirts of the open cluster
NGC 663. It contains the slowest X-ray pulsar known with a pulse period of
around 1400s and, primarily from the study of variation in the emission line
profile of H alpha, it is known to have a Be decretion disk with a one-armed
density wave period of approximately 1240d. Here we present the results of an
extensive photometric campaign, supplemented with optical spectroscopy, aimed
at measuring short time-scale periodicities. We find three significant
periodicities in the photometric data at, in order of statistical significance,
0.34d, 0.67d and 0.10d. We give arguments to support the interpretation that
the 0.34d and 0.10d periods could be due to stellar oscillations of the B type
primary star and that the 0.67d period is the spin period of the Be star with a
spin axis inclination of 23 +10 -8 degrees. We measured a systemic velocity of
-37.0 +- 4.3 km/s confirming that LS I+61 235 has a high probability of
membership in the young cluster NGC 663 from which the system's age can be
estimated as 20-25 Myr. From archival RXTE ASM data we further find "super"
X-ray outbursts roughly every 450d. If these super outbursts are caused by the
alignment of the compact star with the one-armed decretion disk enhancement,
then the orbital period is approximately 330d.


title: Harmonic forms on principal bundles

abstract:
  We show a relationship between Chern-Simons 1- and 3-forms and harmonic forms
on a principal bundle. Doing so requires one to consider an adiabatic limit.
For the 3-form case, assume that G is simple and the corresponding Chern-Weil
4-form is exact. Then, the Chern-Simons 3-form on the princpal bundle G-bundle,
minus a canonical term from the base, is harmonic in the adiabatic limit.


title: Nonreflexive Banach SSD spaces

abstract:
  In this paper, we unify the theory of SSD spaces, part of the theory of
strongly representable multifunctions, and the theory of the equivalence of
various classes of maximally monotone multifunctions.


title: A Mathematical Model of Chaotic Attractor in Tumor Growth and Decay

abstract:
  We propose a strange-attractor model of tumor growth and metastasis. It is a
4-dimensional spatio-temporal cancer model with strong nonlinear couplings.
Even the same type of tumor is different in every patient both in size and
appearance, as well as in temporal behavior. This is clearly a characteristic
of dynamical systems sensitive to initial conditions. The new chaotic model of
tumor growth and decay is biologically motivated. It has been developed as a
live Mathematica demonstration, see Wolfram Demonstrator site:
http://demonstrations.wolfram.com/ChaoticAttractorInTumorGrowth/ Key words:
Reaction-diffusion tumor growth model, chaotic attractor, sensitive dependence
on initial tumor characteristics


title:
Band structure of tetragonal and orthorhombic fluorine-arsenide SrFeAsF
  as a parent phases for a new group of oxygen-free FeAs superconductors

abstract:
  The full-potential linearized augmented plane wave method with the
generalized gradient approximation for the exchange and correlation potential
(LAPW-GGA) is used to understand the electronic band structure of
fluorine-arsenide SrFeAsF as a possible parent material for a new group of
oxygen-free FeAs superconductors. The electronic bands, density of states,
Fermi surface and atomic charges have been evaluated and discussed for
high-temperature tetragonal and low-temperature orthorhombic SrFeAsF phases.


title:
The Deformation Effect on the Electronic Structure of the Graphite
  Nanoribbon Arrays

abstract:
  We have performed a first-principles study on the deformation effect of the
electronic structures of graphite nanoribbon arrays with zigzag edges on both
sides, and the edge atoms are terminated with hydrogen atoms. A uniaxial strain
is considered to have deformation effect on the graphite nanoribbons. We found
that the antiferromagnetic arrangement of the spin polarizing edges of graphite
nanoribbon is still more favorable than that with the ferromagnetic arrangement
under deformation. We also learned that a tensile strain increases the
magnetization of the graphite ribbon while a compressive strain decreases it. A
positive pressure derivative of the band gap of antiferromagnetic state is
observed for the graphite nanoribbon under uniaxial strains. The strain changes
the shape of band structure and the band gap; in here, the edge atoms play a
crucial role. The deformations are also found to influence the contribution of
the edge atoms to the bands near the Fermi level. The deformation effect for
the graphite nanoribbon under transverse electric field is also studied.


title:
Analytical and Numerical Investigation of Ant Behavior Under Crowded
  Conditions

abstract:
  Swarm intelligence is widely recognized as a powerful paradigm of
self-organized optimization, with numerous examples of successful applications
in distributed artificial intelligence. However, the role of physical
interactions in the organization of traffic flows in ants under crowded
conditions has only been studied very recently. The related results suggest new
ways of congestion control and simple algorithms for optimal resource usage
based on local interactions and, therefore, decentralized control concepts.
Here, we present a mathematical analysis of such a concept for an experiment
with two alternative ways with limited capacities between a food source and the
nest of an ant colony. Moreover, we carry out microscopic computer simulations
for generalized setups, in which ants have more alternatives or the alternative
ways are of different lengths. In this way and by variation of interaction
parameters, we can get a better idea, how powerful congestion control based on
local repulsive interactions may be. Finally, we will discuss potential
applications of this design principle to routing in traffic or data networks
and machine usage in supply systems.


title: On thermalization in Kitaev's 2D model

abstract:
  The thermalization process of the 2D Kitaev model is studied within the
Markovian weak coupling approximation. It is shown that its largest relaxation
time is bounded from above by a constant independent of the system size and
proportional to $\exp(2\Delta/kT)$ where $\Delta$ is an energy gap over the
4-fold degenerate ground state. This means that the 2D Kitaev model is not an
example of a memory, neither quantum nor classical.


title: A Cornucopia of Experiment at RHIC

abstract:
  I outline experimental results on heavy ion collisions at the Relativistic
Heavy Ion Collider for a non-technical audience. This includes: elliptic flow
and nearly ideal hydrodynamics; the suppression of hard particles and the ratio
R_AA; and electromagnetic signals, including dileptons and direct photons.
Especially puzzling is why the behavior of heavy (charm) quarks appears to be
so similar to that of light quarks.


title: Chaotic Spin Correlations in Frustrated Ising Hierarchical Lattices

abstract:
  Spin-spin correlations are calculated in frustrated hierarchical Ising models
that exhibit chaotic renormalization-group behavior. The spin-spin
correlations, as a function of distance, behave chaotically. The far
correlations, but not the near correlations, are sensitive to small changes in
temperature or frustration, with temperature changes having a larger effect. On
the other hand, the calculated free energy, internal energy, and entropy are
smooth functions of temperature. The recursion-matrix calculation of
thermodynamic densities in a chaotic band is demonstrated. The leading Lyapunov
exponents are calculated as a function of frustration.


title:
Specification of the social force pedestrian model by evolutionary
  adjustment to video tracking data

abstract:
  Based on suitable video recordings of interactive pedestrian motion and
improved tracking software, we apply an evolutionary optimization algorithm to
determine optimal parameter specifications for the social force model. The
calibrated model is then used for large-scale pedestrian simulations of
evacuation scenarios, pilgrimage, and urban environments.


title:
Extra extension properties of equidimensional holomorphic mappings:
  results and open questions

abstract:
  Holomorphic (nondegenerate) mappings between complex manifolds of the same
dimension are of special interest. For example, they appear as coverings of
complex manifolds. At the same time they have very strong "extra" extension
properties in compare with mappings in different dimensions. The aim of this
paper is to put together the known results on this subject, give some
perspective on the general strategy for future progress, prove some new results
and formulate open questions.


title: X-ray spectral states of microquasars

abstract:
  We discuss the origin of the dramatically different X-ray spectral shapes
observed in the Low Hard State (LHS: dominated by thermal comptonisation) and
the High Soft State (HSS: dominated by the accretion disc thermal emission and
non-thermal comptonisation in the corona). We present numerical simulations
using a new code accounting for the so-called synchrotron boiler effect. These
numerical simulations when compared to the data allow us to constrain the
magnetic field and temperature of the hot protons in the corona. For the hard
state of Cygnus X-1 we find a magnetic field below equipartition with
radiation, suggesting that the corona is not powered through magnetic field
dissipation (as assumed in most accretion disc corona models). On the other
hand, our results also point toward proton temperatures that are substantially
lower than typical temperatures of the ADAF models. Finally, we show that in
both spectral states Comptonising plasma could be powered essentially through
power-law acceleration of non-thermal electrons, which are then partly
thermalised by the synchrotron and Coulomb boiler. This suggests that, contrary
to current beliefs, the corona of the HSS and that of the LHS could be of very
similar nature. The differences between the LHS and HSS coronal spectra would
then be predominantly caused by the strong disc soft cooling emission which is
present in the HSS and absent in the LHS.


title: From Crowd Dynamics to Crowd Safety: A Video-Based Analysis

abstract:
  The study of crowd dynamics is interesting because of the various
self-organization phenomena resulting from the interactions of many
pedestrians, which may improve or obstruct their flow. Besides formation of
lanes of uniform walking direction and oscillations at bottlenecks at moderate
densities, it was recently discovered that stop-and-go waves [D. Helbing et
al., Phys. Rev. Lett. 97, 168001 (2006)] and a phenomenon called "crowd
turbulence" can occur at high pedestrian densities [D. Helbing et al., Phys.
Rev. E 75, 046109 (2007)]. Although the behavior of pedestrian crowds under
extreme conditions is decisive for the safety of crowds during the access to or
egress from mass events as well as for situations of emergency evacuation,
there is still a lack of empirical studies of extreme crowding. Therefore, this
paper discusses how one may study high-density conditions based on suitable
video data. This is illustrated at the example of pilgrim flows entering the
previous Jamarat Bridge in Mina, 5 kilometers from the Holy Mosque in Makkah,
Saudi-Arabia. Our results reveal previously unexpected pattern formation
phenomena and show that the average individual speed does not go to zero even
at local densities of 10 persons per square meter. Since the maximum density
and flow are different from measurements in other countries, this has
implications for the capacity assessment and dimensioning of facilities for
mass events. When conditions become congested, the flow drops significantly,
which can cause stop-and-go waves and a further increase of the density until
critical crowd conditions are reached. Then, "crowd turbulence" sets in, which
may trigger crowd disasters.


title:
The $\Lambda$-$\Sigma$ coupling effect in the neutron-rich
  $\Lambda$-hypernucleus $_{\Lambda}^{10}$Li by microscopic shell model

abstract:
  We investigate the structure of the neutron-rich $\Lambda$-hypernucleus
$_{\Lambda}^{10}$Li by using microscopic shell-model calculations considering a
$\Lambda$-$\Sigma$ coupling effect. The calculated $\Sigma$-mixing probability
in the $_{\Lambda}^{10}$Li ground state is found to be about 0.34 % which is
coherently enhanced by the $\Lambda$-$\Sigma$ coupling configurations, leading
to the energy shift 0.28 MeV which is about 3 times larger than that in
$_{\Lambda}^{7}$Li. The importance of the $\Sigma$ configuration obtained by
the $\Sigma N$ interaction and the potentiality of the neutron-rich environment
are discussed.


title: Robustness of Spin Polarization in Graphene-based Spin Valves

abstract:
  Decrease of spin polarization in spintronics devices under an application of
bias voltage is one of currently important problems which should be solved. We
reveal unprecedented robustness of spin polarization in multi-layer graphene
spin valves at room temperature. Surprisingly, the spin polarization of
injected spins is constant up to a bias voltage of +2.7 V and -0.6 V in
positive and negative bias voltage applications, which is dramatically superior
to all spintronics devices. Our finding is induced by suppression of spin
scattering due to an ideal interface formation. Furthermore, we firstly report
on important accordance between theory and experiment in molecular spintronics
by observing the fact that signal intensity in a local scheme is double of that
in a non-local scheme as theory predicts, which provides construction of a
steadfast physical basis in this field.


title:
The drive system of the Major Atmospheric Gamma-ray Imaging Cherenkov
  Telescope

abstract:
  The MAGIC telescope is an imaging atmospheric Cherenkov telescope, designed
to observe very high energy gamma-rays while achieving a low energy threshold.
One of the key science goals is fast follow-up of the enigmatic and short lived
gamma-ray bursts. The drive system for the telescope has to meet two basic
demands: (1) During normal observations, the 72-ton telescope has to be
positioned accurately, and has to track a given sky position with high
precision at a typical rotational speed in the order of one revolution per day.
(2) For successfully observing GRB prompt emission and afterglows, it has to be
powerful enough to position to an arbitrary point on the sky within a few ten
seconds and commence normal tracking immediately thereafter. To meet these
requirements, the implementation and realization of the drive system relies
strongly on standard industry components to ensure robustness and reliability.
In this paper, we describe the mechanical setup, the drive control and the
calibration of the pointing, as well as present measurements of the accuracy of
the system. We show that the drive system is mechanically able to operate the
motors with an accuracy even better than the feedback values from the axes. In
the context of future projects, envisaging telescope arrays comprising about
100 individual instruments, the robustness and scalability of the concept is
emphasized.


title: Superlens made of a metamaterial with extreme effective parameters

abstract:
  We propose a superlens formed by an ultra-dense array of crossed metallic
wires. It is demonstrated that due to the anomalous interaction between crossed
wires, the structured substrate is characterized by an anomalously high index
of refraction and supports strongly confined guided modes with very short
propagation wavelengths. It is theoretically proven that a planar slab of such
structured material makes a superlens that may compensate for the attenuation
introduced by free-space propagation and restore the subwavelength details of
the source. The bandwidth of the proposed device can be quite significant since
the response of the structured substrate is non-resonant. The theoretical
results are fully supported by numerical simulations.


title:
Obtainment of internal labelling operators as broken Casimir operators
  by means of contractions related to reduction chains in semisimple Lie
  algebras

abstract:
  We show that the In\"on\"u-Wigner contraction naturally associated to a
reduction chain $\frak{s}\supset \frak{s}^{\prime}$ of semisimple Lie algebras
induces a decomposition of the Casimir operators into homogeneous polynomials,
the terms of which can be used to obtain additional mutually commuting missing
label operators for this reduction. The adjunction of these scalars that are no
more invariants of the contraction allow to solve the missing label problem for
those reductions where the contraction provides an insufficient number of
labelling operators.


title:
Virtual copies of semisimple Lie algebras in enveloping algebras of
  semidirect products and Casimir operators

abstract:
  Given a semidirect product $\frak{g}=\frak{s}\uplus\frak{r}$ of semisimple
Lie algebras $\frak{s}$ and solvable algebras $\frak{r}$, we construct
polynomial operators in the enveloping algebra $\mathcal{U}(\frak{g})$ of
$\frak{g}$ that commute with $\frak{r}$ and transform like the generators of
$\frak{s}$, up to a functional factor that turns out to be a Casimir operator
of $\frak{r}$. Such operators are said to generate a virtual copy of $\frak{s}$
in $\mathcal{U}(\frak{g})$, and allow to compute the Casimir operators of
$\frak{g}$ in closed form, using the classical formulae for the invariants of
$\frak{s}$. The behavior of virtual copies with respect to contractions of Lie
algebras is analyzed. Applications to the class of Hamilton algebras and their
inhomogeneous extensions are given.


title:
Experimental Demonstration of a Structured Material with Extreme
  Effective Parameters at Microwaves

abstract:
  Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes,
Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of
crossed metallic wires may behave as a nonresonant material with extremely
large index of refraction at microwaves, and may enable the realization of
ultra-subwavelength waveguides.


title:
Magnetic-field induced superconductor-antiferromagnet transition in
  lightly doped RBa_2Cu_3O_{6+x} (R = Lu, Y) crystals

abstract:
  The remarkable sensitivity of the c-axis resistivity and magnetoresistance in
cuprates to the spin ordering is used to clarify the doping-induced
transformation from an antiferromagnetic (AF) insulator to a superconducting
(SC) metal in RBa_2Cu_3O_{6+x} (R = Lu, Y) single crystals. The established
phase diagram demonstrates that the AF and SC regions apparently overlap: the
superconductivity in RBa_2Cu_3O_{6+x}, in contrast to La_{2-x}Sr_xCuO_4, sets
in before the long-range AF order is completely destroyed by hole doping.
Magnetoresistance measurements of superconducting crystals with low T_c<15-20 K
give a clear view of the magnetic-field induced superconductivity suppression
and recovery of the long-range AF state. What still remains to be understood is
whether the AF order actually persists in the SC state or just revives when the
superconductivity is suppressed, and, in the former case, whether the
antiferromagnetism and superconductivity reside in nanoscopically separated
phases or coexist on an atomic scale.


title: Algorithmic comparisons of decaying, isothermal, supersonic turbulence

abstract:
  Contradicting results have been reported in the literature with respect to
the performance of the numerical techniques employed for the study of
supersonic turbulence. We aim at characterising the performance of different
particle-based and grid-based techniques on the modelling of decaying
supersonic turbulence. Four different grid codes (ENZO, FLASH, TVD, ZEUS) and
three different SPH codes (GADGET, PHANTOM, VINE) are compared. We additionally
analysed two calculations denoted as PHANTOM A and PHANTOM B using two
different implementations of artificial viscosity. Our analysis indicates that
grid codes tend to be less dissipative than SPH codes, though details of the
techniques used can make large differences in both cases. For example, the
Morris & Monaghan viscosity implementation for SPH results in less dissipation
(PHANTOM B and VINE versus GADGET and PHANTOM A). For grid codes, using a
smaller diffusion parameter leads to less dissipation, but results in a larger
bottleneck effect (our ENZO versus FLASH runs). As a general result, we find
that by using a similar number of resolution elements N for each spatial
direction means that all codes (both grid-based and particle-based) show
encouraging similarity of all statistical quantities for isotropic supersonic
turbulence on spatial scales k<N/32 (all scales resolved by more than 32 grid
cells), while scales smaller than that are significantly affected by the
specific implementation of the algorithm for solving the equations of
hydrodynamics. At comparable numerical resolution, the SPH runs were on average
about ten times more computationally intensive than the grid runs, although
with variations of up to a factor of ten between the different SPH runs and
between the different grid runs. (abridged)


title: Ad-nilpotent Ideals and Equivalence Relations

abstract:
  In this paper we study ad-nilpotent ideals of a complex simple Lie algebra
$\ccg$ and their connections with affine Weyl groups and nilpotent orbits. We
define a left equivalence relation for ad-nilpotent ideals based on their
normalizer and generators, and prove that the equivalence relation is
compatible with the left cell structure of affine Weyl group of $\ccg$ and
Lusztig's star operator for type $\tilde A_{n-1}$.


title: Ad-nilpotent Ideals of Minimal Dimension

abstract:
  n this paper we study ad-nilpotent ideals of a complex simple Lie algebra
$\ccg$ and their connections with affine Weyl groups and nilpotent orbits. We
define a left equivalence relation for ad-nilpotent ideals based on their
normalizer and generators, and prove that the equivalence relation is
compatible with the left cell structure of affine Weyl group of $\ccg$ and
Lusztig's star operator for type $\tilde A_{n-1}$.


title: Disentangling Neutrino Oscillations

abstract:
  The theory underlying neutrino oscillations has been described at length in
the literature. The neutrino state produced by a weak decay is usually
portrayed as a linear superposition of mass eigenstates with, variously, equal
energies or equal momenta. We point out that such a description is incomplete,
that in fact, the neutrino is entangled with the other particle or particles
emerging from the decay. We offer an analysis of oscillation phenomena
involving neutrinos (applying equally well to neutral mesons) that takes
entanglement into account. Thereby we present a theoretically sound proof of
the universal validity of the oscillation formulae ordinarily used. In so
doing, we show that the departures from exponential decay reported by the GSI
experiment cannot be attributed to neutrino mixing. Furthermore, we demonstrate
that the `Mossbauer' neutrino oscillation experiment proposed by Raghavan,
while technically challenging, is correctly and unambiguously describable by
means of the usual oscillation formalae.


title:
Emergence of entanglement from a noisy environment: The case of
  polaritons

abstract:
  We show theoretically that polariton pairs with a high degree of polarization
entanglement can be produced through parametric scattering. We demonstrate that
it can emerge in coincidence experiments, even at low excitation densities
where the dynamics is dominated by incoherent photoluminesce. Our analysis is
based on a microscopic quantum statistical approach that treats coherent and
incoherent processes on an equal footing, thus allowing for a quantitative
assessment of the amount of entanglement under realistic experimental
conditions. This result puts forward the robustness of pair correlations in
solid-state devices, even when noise dominates one-body correlations.


title:
Lattice Dynamics and Specific Heat of $\alpha$ - GeTe: a theoretical and
  experimental study

abstract:
  We extend recent \textit{ab initio} calculations of the electronic band
structure and the phonon dispersion relations of rhombohedral GeTe to
calculations of the density of phonon states and the temperature dependent
specific heat. The results are compared with measurements of the specific heat.
It is discovered that the specific heat depends on hole concentration, not only
in the very low temperature region (Sommerfeld term) but also at the maximum of
$C_p/T^3$ (around 16 K). To explain this phenomenon, we have performed
\textit{ab initio} lattice dynamical calculations for GeTe rendered metallic
through the presence of a heavy hole concentration ($p$ $\sim$ 2$\times$
10$^{21}$ cm$^{-3}$). They account for the increase observed in the maximum of
$C_p/T^3$.


title:
Supercell studies of the Fermi surface changes in the electron-doped
  superconductor LaFeAsO$_{1-x}$F$_x$

abstract:
  We study the changes in the Fermi surface with electron doping in the
LaFeAsO$_{1-x}$F$_x$ superconductors with density-functional supercell
calculations using the linearized augmented planewave (LAPW) method. The
supercell calculations with explicit F substitution are compared with those
obtained from the virtual crystal approximation (VCA) and from a simple rigid
band shift. We find significant differences between the supercell results and
those obtained from the rigid-band shift with electron doping, although quite
remarkably the supercell results are in good agreement with the virtual crystal
approximation (VCA) where the nuclear charges of the O atoms are slightly
increased to mimic the addition of the extra electrons. With electron doping,
the two cylindrical hole pockets along $\Gamma-Z$ shrink in size, and the third
hole pocket around $Z$ disappears for an electron doping concentration in
excess of about 7-8%, while the two elliptical electron cylinders along $M-A$
expand in size. The spin-orbit coupling does not affect the Fermi surface much
except to somewhat reduce the size of the third hole pocket in the undoped
case. We find that with the addition of the electrons the antiferromagnetic
state becomes energetically less stable as compared to the nonmagnetic state,
indicating that the electron doping may provide an extra degree of stability to
the formation of the superconducting ground state.


title:
A Realistic Extension of Gauge-Mediated SUSY-Breaking Model with
  Superconformal Hidden Sector

abstract:
  The sequestering of supersymmetry (SUSY) breaking parameters, which is
induced by superconformal hidden sector, is one of the solutions for the
mu/B_mu problem in gauge-mediated SUSY-breaking scenario. However, it is found
that the minimal messenger model does not derive the correct electroweak
symmetry breaking. In this paper we present a model which has the coupling of
the messengers with the SO(10) GUT-symmetry breaking Higgs fields. The model is
one of the realistic extensions of the gauge mediation model with
superconformal hidden sector. It is shown that the extension is applicable for
a broad range of conformality breaking scale.


title:
Reply to the "Comment on: Testing the speed of 'spooky action at a
  distance' "

abstract:
  This is the reply to the comment arXiv:0810.4452 by Kofler, Ursin, Brukner,
and Zeilinger.


title: Trust! Why it Has Been Lost and How to Regain It

abstract:
  This essay suggests that a proper assessment of the presently unfolding
financial crisis, and its cure, requires going back at least to the late 1990s,
accounting for the cumulative effect of the ITC, real-estate and financial
derivative bubbles. We focus on the deep loss of trust, not only in Wall
Street, but more importantly in Main Street, and how to recover it on the short
and long terms. A multi-disciplinary approach is needed to deal with the
nonlinear complex systems of the present world, in order to develop a culture
of fairness, and of upside opportunities associated with a risky world.


title: On ergodicity of some Markov processes

abstract:
  We formulate a criterion for the existence and uniqueness of an invariant
measure for a Markov process taking values in a Polish phase space. In
addition, weak-$^*$ ergodicity, that is, the weak convergence of the ergodic
averages of the laws of the process starting from any initial distribution, is
established. The principal assumptions are the existence of a lower bound for
the ergodic averages of the transition probability function and its local
uniform continuity. The latter is called the e-property. The general result is
applied to solutions of some stochastic evolution equations in Hilbert spaces.
As an example, we consider an evolution equation whose solution describes the
Lagrangian observations of the velocity field in the passive tracer model. The
weak-$^*$ mean ergodicity of the corresponding invariant measure is used to
derive the law of large numbers for the trajectory of a tracer.


title:
Effects of accretion flow on the chemical structure in the inner regions
  of protoplanetary disks

abstract:
  We have studied the dependence of the profiles of molecular abundances and
line emission on the accretion flow in the hot ($\ga 100$K) inner region of
protoplanetary disks. The gas-phase reactions initiated by evaporation of the
ice mantle on dust grains are calculated along the accretion flow. We focus on
methanol, a molecule that is formed predominantly through the evaporation of
warm ice mantles, to show how the abundance profile and line emission depend on
the accretion flow. Our results show that some evaporated molecules keep high
abundances only when the accretion velocity is large enough, and that methanol
could be useful as a diagnostic of the accretion flow by means of ALMA
observations at the disk radius of $\la 10$AU.


title: Learning Isometric Separation Maps

abstract:
  Maximum Variance Unfolding (MVU) and its variants have been very successful
in embedding data-manifolds in lower dimensional spaces, often revealing the
true intrinsic dimension. In this paper we show how to also incorporate
supervised class information into an MVU-like method without breaking its
convexity. We call this method the Isometric Separation Map and we show that
the resulting kernel matrix can be used as a binary/multiclass Support Vector
Machine-like method in a semi-supervised (transductive) framework. We also show
that the method always finds a kernel matrix that linearly separates the
training data exactly without projecting them in infinite dimensional spaces.
In traditional SVMs we choose a kernel and hope that the data become linearly
separable in the kernel space. In this paper we show how the hyperplane can be
chosen ad-hoc and the kernel is trained so that data are always linearly
separable. Comparisons with Large Margin SVMs show comparable performance.


title:
Effect of Fermi-liquid interactions on the low-temperature de Haas - van
  Alphen oscillations in quasi-two-dimensional conductors

abstract:
  In this work we present the results of theoretical analysis of the de
Haas-van Alphen oscillations in quasi-two-dimensional conductors. We have been
studying the effect of the Fermi-liquid correlations of charge carriers on the
above oscillations. It was shown that at reasonably low temperatures and weak
electron scattering the Fermi-liquid interactions may cause noticeable changes
in both amplitude and shape of the oscillations even at realistically small
values of the Fermi-liquid parameters. Also, we show that the Fermi-liquid
interactions in the system of the charge carriers may cause magnetic
instability of a quasi-two-dimensional conductor near the peaks of quantum
oscillations in the electron density of states at the Fermi surface, indicating
the possibility for the diamagnetic phase transition within the relevant ranges
of the applied magnetic fields.


title: Black Holes and the LHC

abstract:
  The relevant physics for the possible formation of black holes in the LHC is
discussed.


title: Experimental determination of the dipolar field in Mn12-acetate

abstract:
  Crystals of the molecular magnet Mn12-acetate are known to contain a small
fraction of low- symmetry (minor) species with a small anisotropy barrier
against spin reversal. The lower barrier leads to faster magnetic relaxation
and lower coercive field. We exploit the low coercive fields of the minor
species to make a direct determination of the dipole field in Mn12-ac. We find
that the dipolar field of a fully magnetized crystal is 51.5 \pm 8.5 mT,
consistent with theoretical expectations.


title: Gravitational Effects of Weak Interactions at TeV Energies

abstract:
  Recently there has been a lot of interest in the search for extra dimensions.
If gravity propagates in extra dimensions then gravity would become as strong
as other interactions. This could also lead to the production of mini black
holes. Here we have discussed how even without considering extra dimensions
gravitational effects of weak interactions could show up at TeV energies.


title: Assembling Actor-based Mind-Maps from Text Stream

abstract:
  For human beings, the processing of text streams of unknown size leads
generally to problems because e.g. noise must be selected out, information be
tested for its relevance or redundancy, and linguistic phenomenon like
ambiguity or the resolution of pronouns be advanced. Putting this into
simulation by using an artificial mind-map is a challenge, which offers the
gate for a wide field of applications like automatic text summarization or
punctual retrieval. In this work we present a framework that is a first step
towards an automatic intellect. It aims at assembling a mind-map based on
incoming text streams and on a subject-verb-object strategy, having the verb as
an interconnection between the adjacent nouns. The mind-map's performance is
enriched by a pronoun resolution engine that bases on the work of D. Klein, and
C. D. Manning.


title: Graph-based classification of multiple observation sets

abstract:
  We consider the problem of classification of an object given multiple
observations that possibly include different transformations. The possible
transformations of the object generally span a low-dimensional manifold in the
original signal space. We propose to take advantage of this manifold structure
for the effective classification of the object represented by the observation
set. In particular, we design a low complexity solution that is able to exploit
the properties of the data manifolds with a graph-based algorithm. Hence, we
formulate the computation of the unknown label matrix as a smoothing process on
the manifold under the constraint that all observations represent an object of
one single class. It results into a discrete optimization problem, which can be
solved by an efficient and low complexity algorithm. We demonstrate the
performance of the proposed graph-based algorithm in the classification of sets
of multiple images. Moreover, we show its high potential in video-based face
recognition, where it outperforms state-of-the-art solutions that fall short of
exploiting the manifold structure of the face image data sets.


title: A New Case for Direct Action

abstract:
  An obstacle to the development of direct action version of electromagnetism
was that in the end it failed to fulfill its initial promise of avoiding the
problem of infinite Coulomb self-energy in the Maxwell theory of the classical
point charge. This paper suggests a small but significant modification of the
traditional direct action theory which overcomes that obstacle. Self-action is
retained but the associated energy is rendered finite and equal to zero in the
special case of null motion.


title:
New two-colour light curves of Q0957+561: time delays and the origin of
  intrinsic variations

abstract:
  We extend the gr-band time coverage of the gravitationally lensed double
quasar Q0957+561. New gr light curves permit us to detect significant intrinsic
fluctuations, to determine new time delays, and thus to gain perspective on the
mechanism of intrinsic variability in Q0957+561. We use new optical frames of
Q0957+561 in the g and r passbands from January 2005 to July 2007. These frames
are part of an ongoing long-term monitoring with the Liverpool robotic
telescope. We also introduce two photometric pipelines that are applied to the
new gr frames of Q0957+561. The transformation pipeline incorporates
zero-point, colour, and inhomogeneity corrections to the instrumental
magnitudes, so final photometry to the 1-2% level is achieved for both quasar
components. The two-colour final records are then used to measure time delays.
The gr light curves of Q0957+561 show several prominent events and gradients,
and some of them (in the g band) lead to a time delay between components of 417
+/- 2 d (1 sigma). We do not find evidence of extrinsic variability in the
light curves of Q0957+561. We also explore the possibility of a delay between a
large event in the g band and the corresponding event in the r band. The gr
cross-correlation reveals a time lag of 4.0 +/- 2.0 d (1 sigma; the g-band
event is leading) that confirms a previous claim of the existence of a delay
between the g and r band in this lensed quasar. The time delays (between quasar
components and between optical bands) from the new records and previous ones in
similar bands indicate that most observed variations in Q0957+561 (amplitudes
of about 100 mmag and timescales of about 100 d) are very probably due to
reverberation within the gas disc around the supermassive black hole.


title: Some structural results on the non-abelian tensor square of groups

abstract:
  We study the non-abelian tensor square $G\otimes G$ for the class of groups G
that are finitely generated modulo their derived subgroup. In particular, we
find conditions on G/G' so that $G\otimes G$ is isomorphic to the direct
product of $\nabla(G)$ and the non-abelian exterior square $G\wedge G$. For any
group G, we characterize the non-abelian exterior square $G\wedge G$ in terms
of a presentation of G. Finally, we apply our results to some classes of
groups, such as the classes of free soluble and free nilpotent groups of finite
rank, and some classes of finite p-groups.


title: Globular Cluster Populations in Four Early-Type Poststarburst Galaxies

abstract:
  We present a study of the globular cluster systems of four early-type
poststarburst galaxies using deep g and I-band images from the ACS camera
aboard the Hubble Space Telescope (HST). All the galaxies feature shells
distributed around their main bodies and are thus likely merger remnants. The
color distribution of the globular clusters in all four galaxies shows a broad
peak centered on g-I ~ 1.4, while PGC 6240 and PGC 42871 show a significant
number of globular clusters with g-I ~ 1.0. The latter globular clusters are
interpreted as being of age ~ 500 Myr and likely having been formed in the
merger. The color of the redder peak is consistent with that expected for an
old metal-poor population that is very commonly found around normal galaxies.
However, all galaxies except PGC 10922 contain several globular clusters that
are significantly brighter than the maximum luminosity expected of a single old
metal-poor population. To test for multiple-age populations of overlapping g-I
color, we model the luminosity functions of the globular clusters as composites
of an old metal-poor subpopulation with a range of plausible specific
frequencies and an intermediate-age subpopulation of solar metallicity. We find
that three of the four sample galaxies show evidence for the presence of an
intermediate-age (~ 1 Gyr) globular cluster population, in addition to the old
metal-poor GC population seen in normal early-type galaxies. None of the
galaxies show a significant population of clusters consistent with an old,
metal-rich red cluster population that is typically seen in early-type
galaxies.


title:
Information Geometry and Chaos on Negatively Curved Statistical
  Manifolds

abstract:
  A novel information-geometric approach to chaotic dynamics on curved
statistical manifolds based on Entropic Dynamics (ED) is suggested.
Furthermore, an information-geometric analogue of the Zurek-Paz quantum chaos
criterion is proposed. It is shown that the hyperbolicity of a non-maximally
symmetric 6N-dimensional statistical manifold M_{s} underlying an ED Gaussian
model describing an arbitrary system of 3N non-interacting degrees of freedom
leads to linear information-geometric entropy growth and to exponential
divergence of the Jacobi vector field intensity, quantum and classical features
of chaos respectively.


title:
Geometrodynamics of Information on Curved Statistical Manifolds and its
  Applications to Chaos

abstract:
  A novel information-geometrodynamical approach to chaotic dynamics (IGAC) on
curved statistical manifolds based on Entropic Dynamics (ED) is presented and a
new definition of information geometrodynamical entropy (IGE) as a measure of
chaoticity is proposed. The general classical formalism is illustrated in a
relatively simple example. It is shown that the hyperbolicity of a
non-maximally symmetric 6N-dimensional statistical manifold M_{s} underlying an
ED Gaussian model describing an arbitrary system of 3N degrees of freedom leads
to linear information-geometric entropy growth and to exponential divergence of
the Jacobi vector field intensity, quantum and classical features of chaos
respectively. An information-geometric analogue of the Zurek-Paz quantum chaos
criterion in the classical reversible limit is proposed. This analogy is
illustrated applying the IGAC to a set of n-uncoupled three-dimensional
anisotropic inverted harmonic oscillators characterized by a Ohmic distributed
frequency spectrum.


title:
Information Geometry, Inference Methods and Chaotic Energy Levels
  Statistics

abstract:
  In this Letter, we propose a novel information-geometric characterization of
chaotic (integrable) energy level statistics of a quantum antiferromagnetic
Ising spin chain in a tilted (transverse) external magnetic field. Finally, we
conjecture our results might find some potential physical applications in
quantum energy level statistics.


title:
Recent theoretical progress on an information geometrodynamical approach
  to chaos

abstract:
  In this paper, we report our latest research on a novel theoretical
information-geometric framework suitable to characterize chaotic dynamical
behavior of arbitrary complex systems on curved statistical manifolds.
Specifically, an information-geometric analogue of the Zurek-Paz quantum chaos
criterion of linear entropy growth and an information-geometric
characterization of chaotic (integrable) energy level statistics of a quantum
antiferromagnetic Ising spin chain in a tilted (transverse) external magnetic
field are presented.


title:
Can chaotic quantum energy levels statistics be characterized using
  information geometry and inference methods?

abstract:
  In this paper, we review our novel information geometrodynamical approach to
chaos (IGAC) on curved statistical manifolds and we emphasize the usefulness of
our information-geometrodynamical entropy (IGE) as an indicator of chaoticity
in a simple application. Furthermore, knowing that integrable and chaotic
quantum antiferromagnetic Ising chains are characterized by asymptotic
logarithmic and linear growths of their operator space entanglement entropies,
respectively, we apply our IGAC to present an alternative characterization of
such systems. Remarkably, we show that in the former case the IGE exhibits
asymptotic logarithmic growth while in the latter case the IGE exhibits
asymptotic linear growth. At this stage of its development, IGAC remains an
ambitious unifying information-geometric theoretical construct for the study of
chaotic dynamics with several unsolved problems. However, based on our recent
findings, we believe it could provide an interesting, innovative and
potentially powerful way to study and understand the very important and
challenging problems of classical and quantum chaos.


title: Open maps between shift spaces

abstract:
  Given a code from a shift space to an irreducible sofic shift, any two of the
following three conditions -- open, constant-to-one, (right or left) closing --
imply the third. If the range is not sofic, then the same result holds when
bi-closingness replaces closingness. Properties of open mappings between shift
spaces are investigated in detail. In particular, we show that a closing open
(or constant-to-one) extension preserves the structure of a sofic shift.


title:
Automorphism groups of domains that depend on fewer than the maximal
  number of parameters

abstract:
  We study domains in complex $n$-space with automorphism group that does not
depend on the full $n$ dimensions of the ambient space. A sufficient geometric
condition is obtained to guarantee that a domain has such a "thin" automorphism
group. Examples are provided to illustrate the ideas.


title:
Performance augmentation in hybrid bionic systems: techniques and
  experiment

abstract:
  Recent developments in hybrid biological-technological systems (hybrid bionic
systems) has made clear the need for evaluating ergonomic fit in such systems,
especially as users first become adjusted to using such systems. This training
is accompanied by physiological adaptation, and can be thought of
computationally as a relative degree of matching between prosthetic devices,
physiology, and behavior. Achieving performance augmentation involves two
features of performance: a specific form of learning, memory, and
mechanotransduction called sensorimotor learning, and physiological adaptation
to novel physical information imposed by the augmented environment of hybrid
bionic systems. A method borrowed from environmental medicine involving
perturbing the environment for a range of internal physiological conditions was
used to induce sensorimotor learning and memory associated physiological
changes. In addition, features of the adult phenotype were considered as a
mitigator of learning-related adaptations. Using a series of statistical tests
and techniques, the results demonstrate than three forms of regulation are at
work related to morphological, neural, and muscular control. A discussion of
the conceptual relationship between homeostasis and adaptation will then be
discussed in addition to potential applications to performance augmentation
strategies.


title:
Performance of the Two Aerogel Cherenkov Detectors of the JLab Hall A
  Hadron Spectrometer

abstract:
  We report on the design and commissioning of two silica aerogel Cherenkov
detectors with different refractive indices. In particular, extraordinary
performance in terms of the number of detected photoelectrons was achieved
through an appropriate choice of PMT type and reflector, along with some design
considerations. After four years of operation, the number of detected
photoelectrons was found to be noticeably reduced in both detectors as a result
of contamination, yellowing, of the aerogel material. Along with the details of
the set-up, we illustrate the characteristics of the detectors during different
time periods and the probable causes of the contamination. In particular we
show that the replacement of the contaminated aerogel and parts of the
reflecting material has almost restored the initial performance of the
detectors.


title:
Strong Influence of a Small Fiber on Shear Stress in Fiber-Reinforced
  Composites

abstract:
  In stiff fiber-reinforced material, the high shear stress concentration
occurs in the narrow region between fibers. With the addition of a small
geometric change in cross-section, such as a thin fiber or a overhanging part
of fiber, the concentration is significantly increased. This paper presents
mathematical analysis to explain the rapidly increased growth of the stress by
a small particle in cross-section. To do so, we consider two crucial cases
where a thin fiber exists between a pair of fibers, and where one of two fibers
has a protruding small lump in cross-section. For each case, the optimal lower
and upper bounds on the stress associated with the geometrical factors of
fibers is established to explain the strongly increased growth of the stress by
a small particle.


title: On the existence of open and bi-continuing codes

abstract:
  Given an irreducible sofic shift X, we show that an an irreducible SFT Y of
lower entropy is a factor of X if and only if it is a factor of X by an open
bi-continuing code. If these equivalent conditions hold and Y is mixing, then
any code from a proper subshift of X to Y can be extended to an open
bi-continuing code on X. These results are still valid when X is assumed to be
only an almost specified shift, i.e., a subshift satisfying an irreducible
version of the specification property.


title: The domain wall spin torque-meter

abstract:
  We report the direct measurement of the non-adiabatic component of the
spin-torque in domain walls. Our method is independent of both the pinning of
the domain wall in the wire as well as of the Gilbert damping parameter. We
demonstrate that the ratio between the non-adiabatic and the adiabatic
components can be as high as 1, and explain this high value by the importance
of the spin-flip rate to the non-adiabatic torque. Besides their fundamental
significance these results open the way for applications by demonstrating a
significant increase of the spin torque efficiency.


title: Unital versions of the higher order peak algebras

abstract:
  We construct unital extensions of the higher order peak algebras defined by
Krob and the third author in [Ann. Comb. 9 (2005), 411--430.], and show that
they can be obtained as homomorphic images of certain subalgebras of the
Mantaci-Reutenauer algebras of type B. This generalizes a result of Bergeron,
Nyman and the first author [Trans. AMS 356 (2004), 2781--2824.].


title: Muon simulation codes MUSIC and MUSUN for underground physics

abstract:
  The paper describes two Monte Carlo codes dedicated to muon simulations:
MUSIC (MUon SImulation Code) and MUSUN (MUon Simulations UNderground). MUSIC is
a package for muon transport through matter. It is particularly useful for
propagating muons through large thickness of rock or water, for instance from
the surface down to underground/underwater laboratory. MUSUN is designed to use
the results of muon transport through rock/water to generate muons in or around
underground laboratory taking into account their energy spectrum and angular
distribution.


title:
Exit and Occupation times for Brownian Motion on Graphs with General
  Drift and Diffusion Constant

abstract:
  We consider a particle diffusing along the links of a general graph
possessing some absorbing vertices. The particle, with a spatially-dependent
diffusion constant D(x) is subjected to a drift U(x) that is defined in every
point of each link. We establish the boundary conditions to be used at the
vertices and we derive general expressions for the average time spent on a part
of the graph before absorption and, also, for the Laplace transform of the
joint law of the occupation times. Exit times distributions and splitting
probabilities are also studied and several examples are discussed.


title: Bracket relations for relativity groups

abstract:
  Poisson bracket relations for generators of canonical transformations are
derived directly from the Galilei and Poincar\'e groups of changes of
space-time coordinates. The method is simple but rigorous. The meaning of each
step is clear because it corresponds to an operation in the group of changes of
space-time coordinates. Only products and inverses are used; differences are
not used. It is made explicitly clear why constants occur in some bracket
relations but not in others, and how some constants can be removed, so that in
the end there is a constant in the bracket relations for the Galilei group but
not for the Poincar\'e group. Each change of coordinates needs to be only to
first order, so matrices are not needed for rotations or Lorentz
transformations; simple three-vector descriptions are enough.
  Conversion to quantum mechanics is immediate. One result is a simpler
derivation of the commutation relations for angular momentum directly from
rotations. Problems are included.


title: Testing ultrafast mode-locking at microhertz relative optical linewidth

abstract:
  We report new limits on the phase coherence of the ultrafast mode-locking
process in an octave-spanning Ti:sapphire comb. We find that the mode-locking
mechanism correlates optical phase across a full optical octave with less than
2.5 micro Hz relative linewidth. This result is at least two orders of
magnitude below recent predictions for quantum-limited individual comb-mode
linewidths, verifying that the mode-locking mechanism strongly correlates
quantum noise across the comb spectrum.


title: Works on an information geometrodynamical approach to chaos

abstract:
  In this paper, I propose a theoretical information-geometric framework
suitable to characterize chaotic dynamical behavior of arbitrary complex
systems on curved statistical manifolds. Specifically, I present an
information-geometric analogue of the Zurek-Paz quantum chaos criterion of
linear entropy growth and an information-geometric characterization of regular
and chaotic quantum energy level statistics.


title: Exploration of a physical picture for the QCD scalar channel

abstract:
  A generalized linear sigma model is employed to study the quark structure of
low lying scalar as well as pseudoscalar states. The model allows the possible
mixing of quark anti-quark states with others made of two quarks and two
antiquarks but no a priori assumption is made about the quark contents of the
predicted physical states. Effects of SU(3) symmetry breaking are included. The
lighter conventional pseudoscalars turn out to be primarily of two quark type
whereas the lighter scalars have very large four quark admixtures.


title: Structure function of the UV variability of Q0957+561

abstract:
  We present a detailed structure function analysis of the UV variability of
Q0957+561. From new optical observations, we constructed normalized structure
functions of the quasar luminosity at restframe wavelengths of 2100 and 2600
\AA. Old optical records also allow the structure function to be obtained at
2100 \AA, but 10 years ago in the observer's frame. These three structure
functions are then compared to predictions of both simple and relatively
sophisticated (incorporating two independent variable components) Poissonian
models. We do not find clear evidence of a chromatic mechanism of variability.
  From the recent data, 100-d time-symmetric and 170-d time-asymmetric flares
are produced at both restframe wavelengths. Taking into account measurements of
time delays and the existence of an EUV/radio jet, reverberation is probably
the main mechanism of variability. Thus, two types of EUV/X-ray fluctuations
would be generated within or close to the jet and later reprocessed by the disc
gas in the two emission rings. The 100-d time-symmetric shots are also
responsible for most of the 2100 \AA variability detected in the old
experiment. However, there is no evidence of asymmetric shots in the old UV
variability. If reverberation is the involved mechanism of variability, this
could mean an intermittent production of high-energy asymmetric fluctuations.
The old records are also consistent with the presence of very short-lifetime
(10 d) symmetric flares, which may represent additional evidence of time
evolution. We also discuss the quasar structure that emerges from the
variability scenario.


title: On deformation of electron holes in phase space

abstract:
  This Letter shows that for particularly shaped background particle
distributions momentum exchange between phase space holes and the distribution
causes acceleration of the holes along the magnetic field. In the particular
case of a non-symmetric ring distribution (ring with loss cone) this
acceleration is nonuniform in phase space being weaker at larger perpendicular
velocities thus causing deformation of the hole in phase space.


title: Ising t-J model close to half filling: A Monte Carlo study

abstract:
  Within the recently proposed doped-carrier representation of the projected
lattice electron operators we derive a full Ising version of the t-J model.
This model possesses the global discrete Z_2 symmetry as a maximal spin
symmetry of the Hamiltonian at any values of the coupling constants, t and J.
In contrast, in the spin anisotropic limit of the t-J model, usually referred
to as the t-J_z model, the global SU(2) invariance is fully restored at J_z=0,
so that only the spin-spin interaction has in that model the true Ising form.
We discuss a relationship between those two models and the standard isotropic
t-J model. We show that the low-energy quasiparticles in all three models share
the qualitatively similar properties at low doping and small values of J/t. The
main advantage of the proposed Ising t-J model over the t-J_z one is that the
former allows for the unbiased Monte Carlo calculations on large clusters of up
to 10^3 sites. Within this model we discuss in detail the destruction of the
antiferromagnetic order by doping as well as the interplay between the AF order
and hole mobility. We also discuss the effect of the exchange interaction and
that of the next nearest neighbour hoppings on the destruction of the AF order
at finite doping. We show that the short-range AF order is observed in a wide
range of temperatures and dopings, much beyond the boundaries of the AF phase.
We explicitly demonstrate that the local no double occupancy constraint plays
the dominant role in destroying the magnetic order at finite doping. Finally, a
role of inhomogeneities is discussed.


title: Stochastic flows with reflection

abstract:
  Some topological properties of stochastic flow $\varphi_t(x)$ generated by
stochastic differential equation in a ${\mathbb R}^d_+$ with normal reflection
at the boundary are investigated. Sobolev differentiability in initial
condition is received. The absolute continuity of the measure-valued process
$\mu\circ\varphi_t^{-1}$, where $\mu\ll\lambda^d,$ is studied.


title: Light nuclei quasiparticle energy shift in hot and dense nuclear matter

abstract:
  Nuclei in dense matter are influenced by the medium. In the cluster mean
field approximation, an effective Schr\"odinger equation for the $A$-particle
cluster is obtained accounting for the effects of the correlated medium such as
self-energy, Pauli blocking and Bose enhancement. Similar to the single-baryon
states (free neutrons and protons), the light elements ($2 \le A \le 4$,
internal quantum state $\nu$) are treated as quasiparticles with energies
$E_{A,\nu}(\vec P; T, n_n,n_p)$. These energies depend on the center of mass
momentum $\vec P$, as well as temperature $T$ and the total densities $n_n,n_p$
of neutrons and protons, respectively. No $\beta$ equilibrium is considered so
that $n_n, n_p$ (or the corresponding chemical potentials $\mu_n, \mu_p$) are
fixed independently.
  For the single nucleon quasiparticle energy shift, different approximate
expressions such as Skyrme or relativistic mean field approaches are well
known. Treating the $A$-particle problem in appropriate approximations, results
for the cluster quasiparticle shifts are given. Properties of dense nuclear
matter at moderate temperatures in the subsaturation density region considered
here are influenced by the composition. This in turn is determined by the
cluster quasiparticle energies, in particular the formation of clusters at low
densities when the temperature decreases, and their dissolution due to Pauli
blocking as the density increases. Our finite-temperature Green function
approach covers different limiting cases: The low-density region where the
model of nuclear statistical equilibrium and virial expansions can be applied,
and the saturation density region where a mean field approach is possible.


title: Edge effects in Bilayer Graphene Nanoribbons

abstract:
  We show that the ground state of zigzag bilayer graphene nanoribbons is
non-magnetic. It also possesses a finite gap, which has a non-monotonic
dependence with the width as a consequence of the competition between bulk and
strongly attractive edge interactions. All results were obtained using {ab
initio} total energy density functional theory calculations with the inclusion
of parametrized van der Waals interactions.


title:
Exact Half-BPS Flux Solutions in M-theory II: Global solutions
  asymptotic to AdS_7 x S^4

abstract:
  General local half-BPS solutions in M-theory, which have $SO(2,2)\times
SO(4)\times SO(4)$ symmetry and are asymptotic to $AdS_{7}\times S^{4}$, were
constructed in exact form by the authors in [arXiv:0806.0605]. In the present
paper, suitable regularity conditions are imposed on these local solutions, and
corresponding globally well-defined solutions are explicitly constructed. The
physical properties of these solutions are analyzed, and interpreted in terms
of the gravity duals to extended 1+1-dimensional half-BPS defects in the
6-dimensional CFT with maximal supersymmetry.


title: The M2/M5 BPS Partition Functions from Supergravity

abstract:
  In the framework of the AdS/CFT duality, we calculate the supersymmetric
partition function of the superconformal field theories living in the world
volume of either $N$ $M2$-branes or $N$ $M5$-branes. We used the dual
supergravity partition function in a saddle point approximation over
supersymmetric Black Holes. Since our BHs are written in asymptotically global
$AdS_{d+1}$ co-ordinates, the dual SCFTs are in $R x S^{d}$ for $d=2,5$. The
resulting partition function shows phase transitions, constraints on the phase
space and allowed us to identify unstable BPS Black hole in the $AdS$ phase.
These configurations should correspond to unstable configurations in the dual
theory. We also report an intriguing relation between the most general Witten
Index, computed in the above theories, and our BPS partition functions.


title: Gram determinant of planar curves

abstract:
  We investigate the Gram determinant of the bilinear form based on curves in a
planar surface, with a focus on the disk with two holes. We prove that the
determinant based on $n-1$ curves divides the determinant based on $n$ curves.
Motivated by the work on Gram determinants based on curves in a disk and curves
in an annulus (Temperley-Lieb algebra of type $A$ and $B$, respectively), we
calculate several examples of the Gram determinant based on curves in a disk
with two holes and advance conjectures on the complete factorization of Gram
determinants.


title:
Abell 1201: The anatomy of a cold front cluster from combined optical
  and X-ray data

abstract:
  We present a combined X-ray and optical analysis of the cold front cluster
Abell 1201 using archival Chandra, data and multi-object spectroscopy taken
with the 3.9m Anglo Australian and 6.5m Multiple Mirror Telescopes. This paper
represents the first in a series presenting a study of a sample of cold front
clusters selected from the Chandra, archives with the aim of relating cold
fronts to merger activity, understanding the dynamics of mergers and their
effect on the cluster constituents. The Chandra X-ray imagery of Abell 1201
reveals two conspicuous surface brightness discontinuities, which are shown to
be cold fronts, and a remnant core structure. Temperature maps reveal a complex
multi-phase temperature structure with regions of hot gas interspersed with
fingers of cold gas. Our optical analysis is based on a sample of 321 confirmed
members, whose mean redshift is z=0.1673 +/- 0.0002 and velocity dispersion is
778 +/- 36 km/s. We search for dynamical substructure and find clear evidence
for multiple localized velocity substructures coincident with over-densities in
the galaxy surface density. Most notably, we find structure coincident with the
remnant X-ray core. Despite the clear evidence for dynamical activity, we find
the peculiar velocity distribution does not deviate significantly from
Gaussian. We apply two-body dynamical analyses in order to assess which of the
substructures are bound, and thus dynamically important in terms of the cluster
merger history. We propose that the cold fronts in Abell 1201 are a consequence
of its merger with a smaller subunit, which has induced gas motions that gave
rise to `sloshing' cold fronts. Abell 1201 illustrates the value of combining
multi-wavelength data and multiple substructure detection techniques when
attempting to ascertain the dynamical state of a cluster.


title: Endpoint maximal and smoothing estimates for Schroedinger equations

abstract:
  For $\alpha >1$ we consider the initial value problem for the dispersive
equation $i\partial_t u +(-\Delta)^{\alpha/2} u= 0$. We prove an endpoint $L^p$
inequality for the maximal function $\sup_{t\in[0,1]}|u(\cdot,t)|$ with initial
values in $L^p$-Sobolev spaces, for $p\in(2+4/(d+1),\infty)$. This strengthens
the fixed time estimates due to Fefferman and Stein, and Miyachi. As an
essential tool we establish sharp $L^p$ space-time estimates (local in time)
for the same range of $p$.


title: Electrolytically Generated Nanobubbles on HOPG Surfaces

abstract:
  Electrolysis of water is employed to produce surface nanobubbles on highly
orientated pyrolytic graphite (HOPG) surfaces. Hydrogen (oxygen) nanobubbles
are formed when the HOPG surface acts as negative (positive) electrode.
Coverage and volume of the nanobubbles enhance with increasing voltage. The
yield of hydrogen nanobubbles is much larger than the yield of oxygen
nanobubbles. The growth of the individual nanobubbles during the electrolysis
process is recorded in time with the help of AFM measurements and correlated
with the total current. Both the size of the individual nanobubbles and the
total current saturate after typical 1 minute; then the nanobubbles are in a
dynamic equilibrium, meaning that they do not further grow, in spite of ongoing
gas production and nonzero current. The surface area of nanobubbles shows a
good correlation with the nanobubble volume growth rate, suggesting that either
the electrolytic gas emerges directly at the nanobubbles' surface, or it
emerges at the electrode's surface and then diffuses through the nanobubbles'
surface. Moreover, the experiments reveal that the time constants of the
current and the aspect ratio of nanobubbles are the same under all conditions.
Replacement of pure water by water containing a small amount of sodium chloride
(0.01 M) allows for larger currents, but qualitatively gives the same results.


title:
Bounds on new light particles from high-energy and very small momentum
  transfer np elastic scattering data

abstract:
  We found that spin-one new light particle exchanges are strongly bounded by
high-energy and small momentum transfer np elastic scattering data; the
analogous bound for a scalar particle is considerably weaker, while for a
pseudoscalar particle no bounds can be set. These bounds are compared with the
bounds extracted from low-energy n-Pb scattering experiments and from the
bounds of pi0 and K+ meson decays.


title: Generalized improper integral definition for finite limit

abstract:
  A generalization of the definition of a one-dimensional improper integral
with a finite limit is presented. The new definition extends the range of valid
integrals to include integrals which were previously considered to not be
integrable. This definition is shown to be equivalent to the infinite limit
definition presented in "Generalized improper integral definition for infinite
limit" (arXiv:0805.3559) via a particular change of variable of integration.
The definition preserves linearity and uniqueness. Integrals which are valid
under the conventional definition have the same value under the new definition.
Criteria for interchanging the order of integration and differentiation, and
for interchanging the order with a second integration, are obtained. Examples
are provided.


title: A note on lattice-face polytopes and their Ehrhart polynomials

abstract:
  We give a new definition of lattice-face polytopes by removing an unnecessary
restriction in the paper "Ehrhart polynomials of lattice-face polytopes", and
show that with the new definition, the Ehrhart polynomial of a lattice-face
polytope still has the property that each coefficient is the normalized volume
of a projection of the original polytope. Furthermore, we show that the new
family of lattice-face polytopes contains all possible combinatorial types of
rational polytopes.


title: The Yoneda algebra of a K_2 algebra need not be another K_2 algebra

abstract:
  The Yoneda algebra of a Koszul algebra or a D-Koszul algebra is Koszul. K_2
algebras are a natural generalization of Koszul algebras, and one would hope
that the Yoneda algebra of a K_2 algebra would be another K_2 algebra. We show
that this is not necessarily the case by constructing a monomial K_2 algebra
for which the corresponding Yoneda algebra is not K_2.


title:
Cooperative Strategies for the Half-Duplex Gaussian Parallel Relay
  Channel: Simultaneous Relaying versus Successive Relaying

abstract:
  This study investigates the problem of communication for a network composed
of two half-duplex parallel relays with additive white Gaussian noise. Two
protocols, i.e., \emph{Simultaneous} and \emph{Successive} relaying, associated
with two possible relay orderings are proposed. The simultaneous relaying
protocol is based on \emph{Dynamic Decode and Forward (DDF)} scheme. For the
successive relaying protocol: (i) a \emph{Non-Cooperative} scheme based on the
\emph{Dirty Paper Coding (DPC)}, and (ii) a \emph{Cooperative} scheme based on
the \emph{Block Markov Encoding (BME)} are considered. Furthermore, the
composite scheme of employing BME at one relay and DPC at another always
achieves a better rate when compared to the \emph{Cooperative} scheme. A
\emph{"Simultaneous-Successive Relaying based on Dirty paper coding scheme"
(SSRD)} is also proposed. The optimum ordering of the relays and hence the
capacity of the half-duplex Gaussian parallel relay channel in the low and high
signal-to-noise ratio (SNR) scenarios is derived. In the low SNR scenario, it
is revealed that under certain conditions for the channel coefficients, the
ratio of the achievable rate of the simultaneous relaying based on DDF to the
cut-set bound tends to be 1. On the other hand, as SNR goes to infinity, it is
proved that successive relaying, based on the DPC, asymptotically achieves the
capacity of the network.


title:
Indexability of Restless Bandit Problems and Optimality of Whittle's
  Index for Dynamic Multichannel Access

abstract:
  We consider a class of restless multi-armed bandit problems (RMBP) that
arises in dynamic multichannel access, user/server scheduling, and optimal
activation in multi-agent systems. For this class of RMBP, we establish the
indexability and obtain Whittle's index in closed-form for both discounted and
average reward criteria. These results lead to a direct implementation of
Whittle's index policy with remarkably low complexity. When these Markov chains
are stochastically identical, we show that Whittle's index policy is optimal
under certain conditions. Furthermore, it has a semi-universal structure that
obviates the need to know the Markov transition probabilities. The optimality
and the semi-universal structure result from the equivalency between Whittle's
index policy and the myopic policy established in this work. For non-identical
channels, we develop efficient algorithms for computing a performance upper
bound given by Lagrangian relaxation. The tightness of the upper bound and the
near-optimal performance of Whittle's index policy are illustrated with
simulation examples.


title: A New Approach to Quantum Gravity from a Model of an Elastic Solid

abstract:
  We show that the dynamics of an elastic solid embedded in a Minkowski space
consist of a set of coupled equations describing a spin-1/2 field, $\Psi$,
obeying Dirac's equation, a vector potential, $A_\mu$, obeying Maxwell's
equations and a metric, $g_{\mu\nu}$, which satisfies the Einstein field
equations. The combined set of Dirac's, Maxwell's and the Einstein field
equations all emerge from a simple elastic model in which the field variables
$\Psi$, $A_\mu$ and $g_{\mu\nu}$ are each identified as derived quantities from
the field displacements of ordinary elasticity theory. By quantizing the
elastic field displacements, a quantization of all of the derived fields are
obtained even though they do not explicitly appear in the Lagrangian. We
demonstrate the approach in a three dimensional setting where explicit
solutions of the Dirac field in terms of fractional derivatives are obtained. A
higher dimensional version of the theory would provide an alternate approach to
theories of quantum gravity.


title: Energy Transfer in Multi Field Inflation and Cosmological Perturbations

abstract:
  In cascade inflation and some other string inflation models, collisions of
mobile branes with other branes or orbifold planes occur and lead to
interesting cosmological signatures. The fundamental M/string-theory
description of these collisions is still lacking but it is clear that the
inflaton looses part of its energy to some form of brane matter, e.g. a
component of tensionless strings. In the absence of a fundamental description,
we assume a general barotropic fluid on the brane, which absorbs part of the
inflaton's energy. The fluid is modeled by a scalar with a suitable exponential
potential to arrive at a full-fledged field theory model. We study numerically
the impact of the energy transfer from the inflaton to the scalar on curvature
and isocurvature perturbations and demonstrate explicitly that the curvature
power spectrum gets modulated by oscillations which damp away toward smaller
scales. Even though, the contribution of isocurvature perturbations decays
toward the end of inflation, they induce curvature perturbations on scales that
exit the horizon before the collision. We consider cases where the scalar
behaves like radiation, matter or a web of cosmic strings and discuss the
differences in the resulting power spectra.


title: Equidistribution of sparse sequences on nilmanifolds

abstract:
  We study equidistribution properties of nil-orbits $(b^nx)_{n\in\N}$ when the
parameter $n$ is restricted to the range of some sparse sequence that is not
necessarily polynomial. For example, we show that if $X=G/\Gamma$ is a
nilmanifold, $b\in G$ is an ergodic nilrotation, and $c\in \R\setminus \Z$ is
positive, then the sequence $(b^{[n^c]}x)_{n\in\N}$ is equidistributed in $X$
for every $x\in X$. This is also the case when $n^c$ is replaced with $a(n)$,
where $a(t)$ is a function that belongs to some Hardy field, has polynomial
growth, and stays logarithmically away from polynomials, and when it is
replaced with a random sequence of integers with sub-exponential growth.
Similar results have been established by Boshernitzan when $X$ is the circle.


title:
The HARPS search for southern extra-solar planets XVII. Six long-period
  giant planets around BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377,
  HD 153950

abstract:
  We report the discovery of six new substellar companions of main-sequence
stars, detected through multiple Doppler measurements with the instrument HARPS
installed on the ESO 3.6m telescope, La Silla, Chile. These extrasolar planets
are orbiting the stars BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377,
HD 153950. The orbital characteristics which best fit the observed data are
depicted in this paper, as well as the stellar and planetary parameters. Masses
of the companions range from 2 to 18 Jupiter masses, and periods range from 100
to 2000 days. The observational data are carefully analysed for
activity-induced effects and we conclude on the reliability of the observed
radial-velocity variations as of exoplanetary origin. Of particular interest is
the very massive planet (or brown-dwarf companion) around the metal-rich HD
131664 with M2sini= 18.15 MJup, and a 5.34-year orbital period. These new
discoveries reinforces the observed statistical properties of the exoplanet
sample as known so far.


title: An efficient method for calculating thermoelastic properties

abstract:
  First-principles quasi-harmonic calculations play a very important role in
mineral physics because they can accurately predict the structure and
thermodynamic properties of materials at pressure and temperature conditions
that are still challenging for experiments. It also enables calculations of
thermoelastic properties by obtaining the second-order derivatives of the free
energies with respect to strain. However, these are exceedingly demanding
computations requiring thousands of large jobs running on 101 processors each.
Here we introduce a simpler approach that requires only calculations of static
elastic constants and phonon density of states for unstrained configurations.
This approach decreases the computational time by more than one order of
magnitude. We show results on MgO and forsterite that are in very good
agreement with previous first-principles results and experimental data.


title:
A Stochastic Representation for Backward Incompressible Navier-Stokes
  Equations

abstract:
  By reversing the time variable we derive a stochastic representation for
backward incompressible Navier-Stokes equations in terms of stochastic
Lagrangian paths, which is similar to Constantin and Iyer's forward
formulations in \cite{Co-Iy}. Using this representation, a self-contained proof
of local existence of solutions in Sobolev spaces are provided for
incompressible Navier-Stokes equations in the whole space. In two dimensions or
large viscosity, an alternative proof to the global existence is also given.
Moreover, a large deviation estimate for stochastic particle trajectories is
presented when the viscosity tends to zero.


title: Instability of Axions and Photons In The Presence of Cosmic Strings

abstract:
  We report that axions and photons exhibit instability in the presence of
cosmic strings that are carrying magnetic flux in their core. The strength of
the instability is determined by the symmetry breaking scale of the cosmic
string theory. This result would be evident in gamma ray bursts and axions
emanating from the cosmic string. These effects will eventually lead to
evaporation of the cosmic string.


title: Computing inclusions of Schur modules

abstract:
  We describe a software package for constructing minimal free resolutions of
GL_n(Q)-equivariant graded modules M over Q[x_1, ..., x_n] such that for all i,
the ith syzygy module of M is generated in a single degree. We do so by
describing some algorithms for manipulating polynomial representations of the
general linear group GL_n(Q) following ideas of Olver and
Eisenbud-Floystad-Weyman.


title: On total dominating sets in graphs

abstract:
  A set $S$ of vertices in a graph $G(V,E)$ is called a dominating set if every
vertex $v\in V$ is either an element of $S$ or is adjacent to an element of
$S$. A set $S$ of vertices in a graph $G(V,E)$ is called a total dominating set
if every vertex $v\in V$ is adjacent to an element of $S$. The domination
number of a graph $G$ denoted by $\gamma(G)$ is the minimum cardinality of a
dominating set in $G$. Respectively the total domination number of a graph $G$
denoted by $\gamma_t(G)$ is the minimum cardinality of a total dominating set
in $G$. An upper bound for $\gamma_t(G)$ which has been achieved by Cockayne
and et al. in $\cite{coc}$ is: for any graph $G$ with no isolated vertex and
maximum degree $\Delta(G)$ and $n$ vertices, $\gamma_t(G)\leq n-\Delta(G)+1$.
Here we characterize bipartite graphs and trees which achieve this upper bound.
Further we present some another upper and lower bounds for $\gamma_t(G)$. Also,
for circular complete graphs, we determine the value of $\gamma_t(G)$.


title: On Granular Knowledge Structures

abstract:
  Knowledge plays a central role in human and artificial intelligence. One of
the key characteristics of knowledge is its structured organization. Knowledge
can be and should be presented in multiple levels and multiple views to meet
people's needs in different levels of granularities and from different
perspectives. In this paper, we stand on the view point of granular computing
and provide our understanding on multi-level and multi-view of knowledge
through granular knowledge structures (GKS). Representation of granular
knowledge structures, operations for building granular knowledge structures and
how to use them are investigated. As an illustration, we provide some examples
through results from an analysis of proceeding papers. Results show that
granular knowledge structures could help users get better understanding of the
knowledge source from set theoretical, logical and visual point of views. One
may consider using them to meet specific needs or solve certain kinds of
problems.


title: Parametrized Borsuk-Ulam problem for projective space bundles

abstract:
  Let $\pi: E \to B$ be a fiber bundle with fiber having the mod 2 cohomology
algebra of a real or a complex projective space and let $\pi^{'}: E^{'} \to B$
be vector bundle such that $\mathbb{Z}_2$ acts fiber preserving and freely on
$E$ and $E^{'}-0$, where 0 stands for the zero section of the bundle
$\pi^{'}:E^{'} \to B$. For a fiber preserving $\mathbb{Z}_2$-equivariant map
$f:E \to E^{'}$, we estimate the cohomological dimension of the zero set $Z_f =
\{x \in E | f(x)= 0\}.$ As an application, we also estimate the cohomological
dimension of the $\mathbb{Z}_2$-coincidence set $A_f=\{x \in E | f(x) = f(T(x))
\}$ of a fiber preserving map $f:E \to E^{'}$.


title:
Polynomial Representation of $F_4$ and a New Combinatorial Identity
  about Twenty-Four

abstract:
  Singular vectors of a representation of a finite-dimensional simple Lie
algebra are weight vectors in the underlying module that are nullified by
positive root vectors. In this article, we use partial differential equations
to find all the singular vectors of the polynomial representation of the simple
Lie algebra of type $F_4$ over its basic irreducible module. As applications,
we obtain a new combinatorial identity about the number 24 and explicit
generators of invariants. Moreover, we show that the number of irreducible
submodules contained in the space of homogeneous harmonic polynomials with
degree $k\geq 2$ is $\geq [|k/3|]+[|(k-2)/3|]+2$.


title: Geometry induced charge separation on a helicoidal ribbon

abstract:
  We present an exact calculation of the effective geometry-induced quantum
potential for a particle confined on a helicoidal ribbon. This potential leads
to the appearance of localized states at the rim of the helicoid. In this
geometry the twist of the ribbon plays the role of an effective transverse
electric field on the surface and thus this is reminiscent of the quantum Hall
effect.


title: Scientists who engage with society perform better academically

abstract:
  Most scientific institutions acknowledge the importance of opening the
so-called 'ivory tower' of academic research through popularization, industrial
collaboration or teaching. However, little is known about the actual openness
of scientific institutions and how their proclaimed priorities translate into
concrete measures. This paper gives an idea of some actual practices by
studying three key points: the proportion of researchers who are active in
wider dissemination, the academic productivity of these scientists, and the
institutional recognition of their wider dissemination activities in terms of
their careers. We analyze extensive data about the academic production, career
recognition and teaching or public/industrial outreach of several thousand of
scientists, from many disciplines, from France's Centre National de la
Recherche Scientifique. We find that, contrary to what is often suggested,
scientists active in wider dissemination are also more active academically.
However, their dissemination activities have almost no impact (positive or
negative) on their careers.


title: Cylindrical solutions in metric f(R) gravity

abstract:
  We study static cylindrically symmetric vacuum solutions in Weyl coordinates
in the context of the metric f(R) theories of gravity. The set of the modified
Einstein equations is reduced to a single equation and it is shown how one can
construct exact solutions corresponding to different $f(R)$ models. In
particular the family of solutions with constant Ricci scalar ($R=R_{0}$) is
found explicitly which, as a special case (R=0), includes the exterior
spacetime of a cosmic string. Another new solution with constant, non-zero
Ricci scalar is obtained and its possible relation to the Linet-Tian solution
in general relativity is discussed.


title:
Monitoring stellar orbits around the Massive Black Hole in the Galactic
  Center

abstract:
  We present the results of 16 years of monitoring stellar orbits around the
massive black hole in center of the Milky Way using high resolution NIR
techniques. This work refines our previous analysis mainly by greatly improving
the definition of the coordinate system, which reaches a long-term astrometric
accuracy of 300 microarcsecond, and by investigating in detail the individual
systematic error contributions. The combination of a long time baseline and the
excellent astrometric accuracy of adaptive optics data allow us to determine
orbits of 28 stars, including the star S2, which has completed a full
revolution since our monitoring began. Our main results are: all stellar orbits
are fit extremely well by a single point mass potential to within the
astrometric uncertainties, which are now 6 times better than in previous
studies. The central object mass is (4.31 +- 0.06|stat +- 0.36|R0) * 10^6 M_sun
where the fractional statistical error of 1.5 percent is nearly independent
from R0 and the main uncertainty is due to the uncertainty in R0. Our current
best estimate for the distance to the Galactic Center is R0 = 8.33 +- 0.35 kpc.
The dominant errors in this value is systematic. The mass scales with distance
as (3.95 +- 0.06) * 10^6 M_sun * (R0/8kpc)^2.19. The orientations of orbital
angular momenta for stars in the central arcsecond are random. We identify six
of the stars with orbital solutions as late type stars, and six early-type
stars as members of the clockwise rotating disk system, as was previously
proposed. We constrain the extended dark mass enclosed between the pericenter
and apocenter of S2 at less than 0.066, at the 99% confidence level, of the
mass of Sgr A*. This is two orders of magnitudes larger than what one would
expect from other theoretical and observational estimates.


title: Dynamics of automorphisms on projective complex manifolds

abstract:
  We show that the dynamics of automorphisms on all projective complex
manifolds X (of dimension 3, or of any dimension but assuming the Good Minimal
Model Program or Mori's Program) are canonically built up from the dynamics on
just three types of projective complex manifolds: complex tori, weak Calabi-Yau
manifolds and rationally connected manifolds. As a by-product, we confirm the
conjecture of Guedj for automorphisms on 3-dimensional projective manifolds,
and also determine pi_1(X).


title:
The dispersionless 2D Toda equation: dressing, Cauchy problem, longtime
  behavior, implicit solutions and wave breaking

abstract:
  We have recently solved the inverse spectral problem for one-parameter
families of vector fields, and used this result to construct the formal
solution of the Cauchy problem for a class of integrable nonlinear partial
differential equations in multidimensions, including the second heavenly
equation of Plebanski and the dispersionless Kadomtsev - Petviashvili (dKP)
equation, arising as commutation of vector fields. In this paper we make use of
the above theory i) to construct the nonlinear Riemann-Hilbert dressing for the
so-called two dimensional dispersionless Toda equation
$(exp(\phi))_{tt}=\phi_{\zeta_1\zeta_2}$, elucidating the spectral mechanism
responsible for wave breaking; ii) we present the formal solution of the Cauchy
problem for the wave form of it: $(exp(\phi))_{tt}=\phi_{xx}+\phi_{yy}$; iii)
we obtain the longtime behaviour of the solutions of such a Cauchy problem,
showing that it is essentially described by the longtime breaking formulae of
the dKP solutions, confirming the expected universal character of the dKP
equation as prototype model in the description of the gradient catastrophe of
two-dimensional waves; iv) we finally characterize a class of spectral data
allowing one to linearize the RH problem, corresponding to a class of implicit
solutions of the PDE.


title:
A Nonsingular Cosmology with a Scale-Invariant Spectrum of Cosmological
  Perturbations from Lee-Wick Theory

abstract:
  We study the cosmology of a Lee-Wick type scalar field theory. First, we
consider homogeneous and isotropic background solutions and find that they are
nonsingular, leading to cosmological bounces. Next, we analyze the spectrum of
cosmological perturbations which result from this model. Unless either the
potential of the Lee-Wick theory or the initial conditions are finely tuned, it
is impossible to obtain background solutions which have a sufficiently long
period of inflation after the bounce. More interestingly, however, we find that
in the generic non-inflationary bouncing cosmology, perturbations created from
quantum vacuum fluctuations in the contracting phase have the correct form to
lead to a scale-invariant spectrum of metric inhomogeneities in the expanding
phase. Since the background is non-singular, the evolution of the fluctuations
is defined unambiguously through the bounce. We also analyze the evolution of
fluctuations which emerge from thermal initial conditions in the contracting
phase. The spectrum of gravitational waves stemming for quantum vacuum
fluctuations in the contracting phase is also scale-invariant, and the tensor
to scalar ratio is not suppressed.