title: The Swift X-Ray Telescope: Status and Performance

abstract:
  We present science highlights and performance from the Swift X-ray Telescope
(XRT), which was launched on November 20, 2004. The XRT covers the 0.2-10 keV
band, and spends most of its time observing gamma-ray burst (GRB)afterglows,
though it has also performed observations of many other objects. By mid-August
2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of
them. The XRT positions enable followup ground-based optical observations, with
roughly 60% of the afterglows detected at optical or near IR wavelengths.
Redshifts are measured for 33% of X-ray afterglows. Science highlights include
the discovery of flaring behavior at quite late times, with implications for
GRB central engines; localization of short GRBs, leading to observational
support for compact merger progenitors for this class of bursts; a mysterious
plateau phase to GRB afterglows; as well as many other interesting observations
such as X-ray emission from comets, novae, galactic transients, and other
objects.


title: Compressed Sensing with Cross Validation

abstract:
  Compressed Sensing decoding algorithms can efficiently recover an N
dimensional real-valued vector x to within a factor of its best k-term
approximation by taking m = 2klog(N/k) measurements y = Phi x. If the sparsity
or approximate sparsity level of x were known, then this theoretical guarantee
would imply quality assurance of the resulting compressed sensing estimate.
However, because the underlying sparsity of the signal x is unknown, the
quality of a compressed sensing estimate x* using m measurements is not
assured. Nevertheless, we demonstrate that sharp bounds on the error || x - x*
||_2 can be achieved with almost no effort. More precisely, we assume that a
maximum number of measurements m is pre-imposed; we reserve 4log(p) of the
original m measurements and compute a sequence of possible estimates
(x_j)_{j=1}^p to x from the m - 4log(p) remaining measurements; the errors ||x
- x*_j ||_2 for j = 1, ..., p can then be bounded with high probability. As a
consequence, numerical upper and lower bounds on the error between x and the
best k-term approximation to x can be estimated for p values of k with almost
no cost. Our observation has applications outside of compressed sensing as
well.


title: Polynomial solutions of nonlinear integral equations

abstract:
  We analyze the polynomial solutions of a nonlinear integral equation,
generalizing the work of C. Bender and E. Ben-Naim. We show that, in some
cases, an orthogonal solution exists and we give its general form in terms of
kernel polynomials.


title:
A note on traveling wave solutions to the two component Camassa-Holm
  equation

abstract:
  In this paper we show that non-smooth functions which are distributional
traveling wave solutions to the two component Camassa-Holm equation are
distributional traveling wave solutions to the Camassa-Holm equation provided
that the set $u^{-1}(c)$, where $c$ is the speed of the wave, is of measure
zero. In particular there are no new peakon or cuspon solutions beyond those
already satisfying the Camassa-Holm equation. However, the two component
Camassa-Holm equation has distinct from Camassa-Holm equation smooth traveling
wave solutions as well as new distributional solutions when the measure of
$u^{-1}(c)$ is not zero. We provide examples of such solutions.


title:
Enhanced Transmission and Second Harmonic Generation from Subwavelength
  Slits on Metal Substrates

abstract:
  We theoretically investigate second harmonic generation that originates from
the nonlinear, magnetic Lorentz force term from single and multiple apertures
carved on thick, opaque metal substrates. The linear transmission properties of
apertures on metal substrates have been previously studied in the context of
the extraordinary transmission of light. The transmission process is driven by
a number of physical mechanisms, whose characteristics and relative importance
depend on the thickness of the metallic substrate, slit size, and slit
separation. In this work we show that a combination of cavity effects and
surface plasmon generation gives rise to enhanced second harmonic generation in
the regime of extraordinary transmittance of the pump field. We have studied
both forward and backward second harmonic generation conversion efficiencies as
functions of the geometrical parameters, and how they relate to pump
transmission efficiency. The resonance phenomenon is evident in the generated
second harmonic signal, as conversion efficiency depends on the duration of
incident pump pulse, and hence its bandwidth. Our results show that the
excitation of tightly confined modes as well as the combination of enhanced
transmission and nonlinear processes can lead to several potential new
applications such as photo-lithography, scanning microscopy, and high-density
optical data storage devices.


title:
Theory of two-photon processes in quantum dots: coherent evolution and
  phonon-induced dephasing

abstract:
  The paper discusses two-photon Rabi oscillations between the ground state of
a quantum dot and the biexciton state, as well as two-photon oscillations
between the two single-exciton states with different circular or linear
polarizations. The effect of phonon-induced decoherence on these processes is
described and optimal system properties and optical driving conditions for
coherent control are identified. It is shown that proper optimalization allows
one to control the biexciton system via two-photon transitions with a high
fidelity.


title: Induced gravity on intersecting brane-worlds Part II: Cosmology

abstract:
  We explore cosmology of intersecting braneworlds with induced gravity on the
branes. We find the cosmological equations that control the evolution of a
moving codimension one brane and a codimension two brane that sits at the
intersection. We study the Friedmann equation at the intersection, finding new
contributions from the six dimensional bulk. These higher dimensional
contributions allow us to find new examples of self-accelerating configurations
for the codimension two brane at the intersection and we discuss their
features.


title:
The Flux Auto- and Cross-Correlation of the Lyman-alpha Forest. I.
  Spectroscopy of QSO Pairs with Arcminute Separations and Similar Redshifts

abstract:
  The Lyman-alpha forest has opened a new redshift regime for cosmological
investigation. At z > 2 it provides a unique probe of cosmic geometry and an
independent constraint on dark energy that is not subject to standard candle or
ruler assumptions. In Paper I of this series on using the Lyman-alpha forest
observed in pairs of QSOs for a new application of the Alcock-Paczynski test,
we present and discuss the results of a campaign to obtain moderate-resolution
spectroscopy (FWHM ~ 2.5 Angstroms) of the Lyman-alpha forest in pairs of QSOs
with small redshift differences (Delta z < 0.25, z > 2.2) and arcminute
separations (< 5'). This data set, composed of seven individual QSOs, 35 pairs,
and one triplet, is also well-suited for future investigations of the coherence
of Lyman-alpha absorbers on ~ 1 Mpc transverse scales and the transverse
proximity effect. We note seven revisions for previously published QSO
identifications and/or redshifts.


title: On Symmetries in the Theory of Finite Rank Singular Perturbations

abstract:
  For a nonnegative self-adjoint operator $A_0$ acting on a Hilbert space
$\mathfrak{H}$ singular perturbations of the form $A_0+V, \
V=\sum_{1}^{n}{b}_{ij}<\psi_j,\cdot>\psi_i$ are studied under some additional
requirements of symmetry imposed on the initial operator $A_0$ and the singular
elements $\psi_j$. A concept of symmetry is defined by means of a one-parameter
family of unitary operators $\sU$ that is motivated by results due to R. S.
Phillips. The abstract framework to study singular perturbations with
symmetries developed in the paper allows one to incorporate physically
meaningful connections between singular potentials $V$ and the corresponding
self-adjoint realizations of $A_0+V$. The results are applied for the
investigation of singular perturbations of the Schr\"{o}dinger operator in
$L_2(\dR^3)$ and for the study of a (fractional) \textsf{p}-adic
Schr\"{o}dinger type operator with point interactions.


title:
Accuracy of the Post-Newtonian Approximation: Optimal Asymptotic
  Expansion for Quasi-Circular, Extreme-Mass Ratio Inspirals

abstract:
  We study the accuracy of the post-Newtonian (PN) approximation and its formal
region of validity, by investigating its optimal asymptotic expansion for the
quasi-circular, adiabatic inspiral of a point particle into a Schwarzschild
black hole. By comparing the PN expansion of the energy flux to numerical
calculations in the perturbative Teukolsky formalism, we show that (i) the
inclusion of higher multipoles is necessary to establish the accuracy of
high-order PN terms, and (ii) the region of validity of PN theory is largest at
relative O(1/c^6) (3PN order). The latter result suggests that the series
diverges beyond 3PN order, at least in the extreme mass-ratio limit, probably
due to the appearance of logarithmic terms in the energy flux. The study
presented here is a first formal attempt to determine the region of validity of
the PN approximation using asymptotic analysis. Therefore, it should serve as a
template to perform similar studies on other systems, such as comparable-mass
quasi-circular inspirals computed by high-accuracy numerical relativistic
simulations.


title: Effective theory of quadratic degeneracies

abstract:
  We present an effective theory for the Bloch functions of a two-dimensional
square lattice near a quadratic degeneracy point. The degeneracy is protected
by the symmetries of the crystal, and breaking these symmetries can either open
a bandgap or split the degeneracy into a pair of linear degeneracies that are
continuable to Dirac points. A degeneracy of this type occurs between the
second and third TM bands of a photonic crystal formed by a square lattice of
dielectric rods. We show that the theory agrees with numerically computed
photonic bandstructures, and discuss the resulting insight into the
reflection-free edge modes induced by parity breaking.


title: Dielectric constant boost in amorphous sesquioxides

abstract:
  High-kappa dielectrics for insulating layers are a current key ingredient of
microelectronics. X2O3 sesquioxide compounds are among the candidates. Here we
show for a typical material of this class, ScO3, that the relatively modest
dielectric constant of its crystalline phase is enhanced in the amorphous phase
by over 40% (from ~15 to ~22). This is due to the disorder-induced activation
of low frequency cation-related modes which are inactive or inefficient in the
crystal, and by the conservation of effective dynamical charges (a measure of
atomic polarizability). The analysis employs density-functional energy-force
and perturbation-theory calculations of the dielectric response of amorphous
samples generated by pair-potential molecular dynamics.


title: Strong law of large numbers with concave moments

abstract:
  In this note not intended for publication, it is observed that a wellnigh
trivial application of the ergodic theorem of Karlsson-Ledrappier yields a
strong LLN for arbitrary concave moments.


title:
The Flux Auto- and Cross-Correlation of the Lyman-alpha Forest. II.
  Modelling Anisotropies with Cosmological Hydrodynamic Simulations

abstract:
  The isotropy of the Lyman-alpha forest in real-space uniquely provides a
measurement of cosmic geometry at z > 2. The angular diameter distance for
which the correlation function along the line of sight and in the transverse
direction agree corresponds to the correct cosmological model. However, the
Lyman-alpha forest is observed in redshift-space where distortions due to
Hubble expansion, bulk flows, and thermal broadening introduce anisotropy.
Similarly, a spectrograph's line spread function affects the autocorrelation
and cross-correlation differently. In this the second paper of a series on
using the Lyman-alpha forest observed in pairs of QSOs for a new application of
the Alcock-Paczynski (AP) test, these anisotropies and related sources of
potential systematic error are investigated with cosmological hydrodynamic
simulations. Three prescriptions for galactic outflow were compared and found
to have only a marginal effect on the Lyman-alpha flux correlation (which
changed by at most 7% with use of the currently favored variable-momentum wind
model vs. no winds at all). An approximate solution for obtaining the zero-lag
cross-correlation corresponding to arbitrary spectral resolution directly from
the zero-lag cross-correlation computed at full-resolution (good to within 2%
at the scales of interest) is presented. Uncertainty in the observationally
determined mean flux decrement of the Lyman-alpha forest was found to be the
dominant source of systematic error; however, this is reduced significantly
when considering correlation ratios. We describe a simple scheme for
implementing our results, while mitigating systematic errors, in the context of
a future application of the AP test.


title: Balance, growth and diversity of financial markets

abstract:
  A financial market comprising of a certain number of distinct companies is
considered, and the following statement is proved: either a specific agent will
surely beat the whole market unconditionally in the long run, or (and this "or"
is not exclusive) all the capital of the market will accumulate in one company.
Thus, absence of any "free unbounded lunches relative to the total capital"
opportunities lead to the most dramatic failure of diversity in the market: one
company takes over all other until the end of time. In order to prove this, we
introduce the notion of perfectly balanced markets, which is an equilibrium
state in which the relative capitalization of each company is a martingale
under the physical probability. Then, the weaker notion of balanced markets is
discussed where the martingale property of the relative capitalizations holds
only approximately, we show how these concepts relate to growth-optimality and
efficiency of the market, as well as how we can infer a shadow interest rate
that is implied in the economy in the absence of a bank.


title: Euler sums and a prime numbers conundrum

abstract:
  This note highlights an interesting connection between Euler sums of even
weight and prime numbers.


title: Two remarks on the Burr-Erdos conjecture

abstract:
  The Ramsey number r(H) of a graph H is the minimum positive integer N such
that every two-coloring of the edges of the complete graph K_N on N vertices
contains a monochromatic copy of H. A graph H is d-degenerate if every subgraph
of H has minimum degree at most d. Burr and Erd\H{o}s in 1975 conjectured that
for each positive integer d there is a constant c_d such that r(H) \leq c_dn
for every d-degenerate graph H on n vertices. We show that for such graphs r(H)
\leq 2^{c_d\sqrt{\log n}}n, improving on an earlier bound of Kostochka and
Sudakov. We also study Ramsey numbers of random graphs, showing that for d
fixed, almost surely the random graph G(n,d/n) has Ramsey number linear in n.
For random bipartite graphs, our proof gives nearly tight bounds.


title: Dielectric Sensing in Epsilon-Near-Zero Narrow Waveguide Channels

abstract:
  We exploit here the dramatic field enhancement caused by energy squeezing and
tunneling (i.e., 'supercoupling') in metamaterial-inspired ultranarrow
waveguide channels with near zero effective permittivity in order to sense
small permittivity variations in a tiny object. The supercoupling effect is
accurately modeled analytically and closed form expressions are derived to
describe the presence of defects or permittivity perturbations along the
channel. Applications for tailoring its pass-band frequency and for high-Q
sensing are proposed at microwave frequencies.


title: Exploring Human Factors in Spreadsheet Development

abstract:
  In this paper we consider human factors and their impact on spreadsheet
development in strategic decision-making. This paper brings forward research
from many disciplines both directly related to spreadsheets and a broader
spectrum from psychology to industrial processing. We investigate how human
factors affect a simplified development cycle and what the potential
consequences are.


title: Measurement of the Spin of the Xi(1530) Resonance

abstract:
  The properties of the Xi(1530) resonance are investigated in the Lambdac+ -->
Xi- pi+ K+ decay process. The data sample was collected with the BaBar detector
at the SLAC PEP-II asymmetric-energy e+ e- collider operating at center of mass
energies 10.58 and 10.54 GeV. The corresponding integrated luminosity is
approximately 230 inverse fb. The spin of the Xi(1530) is established to be
3/2. The existence of an S-wave amplitude in the Xi- pi+ system is inferred,
and its interference with the Xi(1530)0 amplitude provides the first clear
demonstration of the Breit-Wigner phase motion expected for the Xi(1530). The
P_1(cos[theta(Xi-)]) Legendre polynomial moment indicates the presence of a
significant S-wave amplitude for Xi- pi+ mass values above 1.6 GeV/c^2, and a
dip in the mass distribution at approximately 1.7 GeV/c^2 is interpreted as due
to coherent addition of a Xi(1690)0 contribution to this amplitude. This would
imply J^P=1/2^- for the Xi(1690). Attempts at fitting the Xi(1530)0 lineshape
yield unsatisfactory results, and this failure is attributed to interference
effects associated with the amplitudes describing the K+ pi+ and/or Xi- K+
systems.


title:
Comment on Visualization of the interplay between high-temperature
  superconductivity, the pseudogap and impurity resonances

abstract:
  In a recent letter, Chatterjee et al. (Nature Phys. 4, 108 (2008)) reported
tunnelling data obtained below and above the critical temperature (Tc = 15 K)
by STM in overdoped Bi2-yPbySr2CuO6+x (Bi2201) and some interpretations of the
data1. The main experimental findings of their work are observations of
native-impurity resonances which coexist spatially with the superconducting
(SC) gap below Tc and survive unchanged on warming through Tc. No doubts, the
data in the letter are an important piece of information for assembling the
high-Tc SC jigsaw puzzle; however, there are inaccuracies in the discussion. In
addition, I propose another interpretation of the data.


title: Clustering, Angular Size and Dark Energy

abstract:
  The influence of dark matter inhomogeneities on the angular size-redshift
test is investigated for a large class of flat cosmological models driven by
dark energy plus a cold dark matter component (XCDM model). The results are
presented in two steps. First, the mass inhomogeneities are modeled by a
generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is
characterized by a smoothness parameter $\alpha(z)$ and a power index $\gamma$,
and, second, we provide a statistical analysis to angular size data for a large
sample of milliarcsecond compact radio sources. As a general result, we have
found that the $\alpha$ parameter is totally unconstrained by this sample of
angular diameter data.


title:
Risk Management for Complex Calculations: EuSpRIG Best Practices in
  Hybrid Applications

abstract:
  As the need for advanced, interactive mathematical models has increased,
user/programmers are increasingly choosing the MatLab scripting language over
spreadsheets. However, applications developed in these tools have high error
risk, and no best practices exist. We recommend that advanced, highly
mathematical applications incorporate these tools with spreadsheets into hybrid
applications, where developers can apply EuSpRIG best practices. Development of
hybrid applications can reduce the potential for errors, shorten development
time, and enable higher level operations. We believe that hybrid applications
are the future and over the course of this paper, we apply and extend
spreadsheet best practices to reduce or prevent risks in hybrid Excel/MatLab
applications.


title: Divergence of Teichmueller Geodesics

abstract:
  We study the asymptotic geometry of Teichmueller geodesic rays. We show that
when the transverse measures to the vertical foliations of the quadratic
differentials determining two different rays are topologically equivalent, but
are not absolutely continuous with respect to each other, then the rays diverge
in Teichmueller space.


title: Spacings between integers having typically many prime factors

abstract:
  We show that the sequence of integers which have nearly the typical number of
distinct prime factors forms a Poisson process. More precisely, for $\de$
arbitrarily small and positive, the nearest neighbor spacings between integers
$n$ with $|\om(n)-\log_2 n|\le (\log_2 n)^{\de}$ obey the Poisson distribution
law.


title:
On controllability and observability of chains formed by point masses
  connected with springs and dashpots

abstract:
  We consider a physical system constituted by a finite chain of point masses
consecutively linked by linear springs and dashpots. At one of the end points
acts an external control force aligned with the chain and the system is
observable by the position of the other end point. We show that, whatever is
the number of the point masses, if the sequence of the elastic constants is
proportional to the sequence of the dashpot constants, then the mechanical
system is completely controllable, completely observable, completely reachable
and completely re-construictible, in the sense of control theory.


title: Non-vanishing of the symmetric square $L$-function at the central point

abstract:
  Using the mollifier method, we show that for a positive proportion of
holomorphic Hecke eigenforms of level one and weight bounded by a large enough
constant, the associated symmetric square $L$-function does not vanish at the
central point of its critical strip. We note that our proportion is the same as
that found by other authors for other families of $L$-functions also having
symplectic symmetry type.


title:
Experimental verification of the feasibility of a quantum channel
  between Space and Earth

abstract:
  Extending quantum communication to Space environments would enable to perform
fundamental experiments on quantum physics as well as applications of quantum
information at planetary and interplanetary scales. Here, we report the first
experimental implementation of a scheme for single-photon exchange between a
satellite and an Earth-based station. We built an experiment that mimics a
single photon source on a satellite, exploiting the telescope at the Matera
Laser Ranging Observatory of the Italian Space Agency to detect the transmitted
photons. Weak laser pulses, emitted by the ground-based station, are directed
towards a satellite equipped with cube-corner retroreflectors. These reflect a
small portion of the pulse, with an average of less-than-one photon per pulse
directed to our receiver, as required for the faint-pulse quantum
communication. We were able to detect returns from satellite Ajisai, a
low-earth orbit geodetic satellite, whose orbit has a perigee height of 1485
km.


title:
Taxonomy of GRB optical light-curves: identification of a salient class
  of early afterglows

abstract:
  The temporal behaviour of the early optical emission from Gamma-Ray Burst
afterglows can be divided in four classes: fast-rising with an early peak,
slow-rising with a late peak, flat plateaus, and rapid decays since first
measurement. The fast-rising optical afterglows display correlations among peak
flux, peak epoch, and post-peak power-law decay index that can be explained
with a structured outflow seen off-axis, but the shock origin (reverse or
forward) of the optical emission cannot be determined. The afterglows with
plateaus and slow-rises may be accommodated by the same model, if observer
location offsets are larger than for the fast-rising afterglows, or could be
due to a long-lived injection of energy and/or ejecta in the blast-wave. If
better calibrated with more afterglows, the peak flux-peak epoch relation
exhibited by the fast and slow-rising optical light-curves could provide a way
to use this type of afterglows as standard candles.


title: Truncated su(2) moment problem for spin and polarization states

abstract:
  We address the problem whether a given set of expectation values is
compatible with the first and second moments of the generic spin operators of a
system with total spin j. Those operators appear as the Stokes operator in
quantum optics, as well as the total angular momentum operators in the atomic
ensemble literature. We link this problem to a particular extension problem for
bipartite qubit states; this problem is closely related to the symmetric
extension problem that has recently drawn much attention in different contexts
of the quantum information literature. We are able to provide operational,
approximate solutions for every large spin numbers, and in fact the solution
becomes exact in the limiting case of infinite spin numbers. Solutions for low
spin numbers are formulated in terms of a hyperplane characterization, similar
to entanglement witnesses, that can be efficiently solved with semidefinite
programming.


title: Harmonic Cheeger-Simons characters with applications

abstract:
  We initiate the study of harmonic Cheeger-Simons characters, with
applications to smooth versions of the Geometric Langlands program in the
abelian case.


title:
Breaking Out of the Cell: On The Benefits of a New Spreadsheet
  User-Interaction Paradigm

abstract:
  Contemporary spreadsheets are plagued by a profusion of errors, auditing
difficulties, lack of uniform development methodologies, and barriers to easy
comprehension of the underlying business models they represent. This paper
presents a case that most of these difficulties stem from the fact that the
standard spreadsheet user-interaction paradigm - the 'cell-matrix' approach -
is appropriate for spreadsheet data presentation but has significant drawbacks
with respect to spreadsheet creation, maintenance and comprehension when
workbooks pass a minimal threshold of complexity. An alternative paradigm for
the automated generation of spreadsheets directly from plain-language business
model descriptions is presented along with its potential benefits. Sunsight
Modeller (TM), a working software system implementing the suggested paradigm,
is briefly described.


title: Conformal invariance of the writhe of a knot

abstract:
  We give a new proof of an old theorem by Banchoff and White 1975 that claims
that the writhe of a knot is conformally invariant.


title: The numeraire portfolio in semimartingale financial models

abstract:
  We study the existence of the numeraire portfolio under predictable convex
constraints in a general semimartingale model of a financial market. The
numeraire portfolio generates a wealth process, with respect to which the
relative wealth processes of all other portfolios are supermartingales.
Necessary and sufficient conditions for the existence of the numeraire
portfolio are obtained in terms of the triplet of predictable characteristics
of the asset price process. This characterization is then used to obtain
further necessary and sufficient conditions, in terms of a no-free-lunch-type
notion. In particular, the full strength of the "No Free Lunch with Vanishing
Risk" (NFLVR) is not needed, only the weaker "No Unbounded Profit with Bounded
Risk" (NUPBR) condition that involves the boundedness in probability of the
terminal values of wealth processes. We show that this notion is the minimal
a-priori assumption required in order to proceed with utility optimization. The
fact that it is expressed entirely in terms of predictable characteristics
makes it easy to check, something that the stronger NFLVR condition lacks.


title: Raman spectroscopy of epitaxial graphene on a SiC substrate

abstract:
  The fabrication of epitaxial graphene (EG) on SiC substrate by annealing has
attracted a lot of interest as it may speed up the application of graphene for
future electronic devices. The interaction of EG and the SiC substrate is
critical to its electronic and physical properties. In this work, Raman
spectroscopy was used to study the structure of EG and its interaction with SiC
substrate. All the Raman bands of EG blue shift from that of bulk graphite and
graphene made by micromechanical cleavage, which was attributed to the
compressive strain induced by the substrate. A model containing 13 x 13
honeycomb lattice cells of graphene on carbon nanomesh was constructed to
explain the origin of strain. The lattice mismatch between graphene layer and
substrate causes the compressive stress of 2.27 GPa on graphene. We also
demonstrate that the electronic structures of EG grown on Si and C terminated
SiC substrates are quite different. Our experimental results shed light on the
interaction between graphene and SiC substrate that are critical to the future
applications of EG.


title:
Controlling nosocomial infection based on structure of hospital social
  networks

abstract:
  Nosocomial infection raises a serious public health problem, as implied by
the existence of pathogens characteristic to healthcare and hospital-mediated
outbreaks of influenza and SARS. We simulate stochastic SIR dynamics on social
networks, which are based on observations in a hospital in Tokyo, to explore
effective containment strategies against nosocomial infection. The observed
networks have hierarchical and modular structure. We show that healthcare
workers, particularly medical doctors, are main vectors of diseases on these
networks. Intervention methods that restrict interaction between medical
doctors and their visits to different wards shrink the final epidemic size more
than intervention methods that directly protect patients, such as isolating
patients in single rooms. By the same token, vaccinating doctors with priority
rather than patients or nurses is more effective. Finally, vaccinating
individuals with large betweenness centrality is superior to vaccinating ones
with large connectedness to others or randomly chosen individuals, as suggested
by previous model studies. [The abstract of the manuscript has more
information.]


title:
Dissolved deconfinement: Phase Structure of large N gauge theories with
  fundamental matter

abstract:
  A class of large N SU(N) gauge theories on a compact manifold S^3 X R (with
possible inclusion of adjoint matter) is known to show first order
deconfinement transition at the deconfinement temperature. This includes the
familiar example of pure YM theory and N=4 SYM theory. Here we study the effect
of introduction of N_f fundamental matter fields in the phase diagram of the
above mentioned gauge theories at small coupling and in the limit of large N
and finite N_f/N. We find some interesting features like the termination of the
line of first order deconfinement phase transition at a critical point as the
ratio N_f/N is increased and absence of deconfinement transition thereafter
(there is only a smooth crossover). This result may have some implication for
QCD, which unlike a pure gauge theory does not show a first order deconfinement
transition and only displays a smooth crossover at the transition temperature.


title: Monotonicity for excited random walk in high dimensions

abstract:
  We prove that the drift $\theta(d,\beta)$ for excited random walk in
dimension $d$ is monotone in the excitement parameter $\beta \in[0, 1]$, when
$d\ge 9$.


title: Cross sections of e+e- --> gamma VV and e+e- --> gamma gamma V

abstract:
  Cross sections of the e+e- annihilation into one photon plus two vector
mesons, such as J/psi rho, J/psi phi, and rho phi at the center of mass energy
\sqrt{s}=10.58GeV are calculated. These shed light on the measurement of the
e+e- annihilation cross section via radiative return in B-factories. At another
center of mass energy \sqrt{s}=3.097GeV, namely the J/psi resonance peak, the
processes e+e- --> gamma VV and e+e- --> gamma gamma V (with V being rho,
omega, or phi) are calculated with similar method. These calculations give
estimation of the background levels in the study of radiative or double
radiative decays of J/psi.


title: The Minimal Degree for a Class of Finite Complex Reflection Groups

abstract:
  We calculate the minimal degree for a class of finite complex reflection
groups $G(p,p,q)$, for $p$ and $q$ primes and establish relationships between
minimal degrees when these groups are taken in a direct product.


title: The pseudogap ground state in high temperature superconductors

abstract:
  By re-examining recently-published data from angle-resolved photoemission
spectroscopy we demonstrate that, in the superconducting region of the phase
diagram, the pseudogap ground state is an arc metal. This scenario is
consistent with results from Raman spectroscopy, specific heat and NMR. In
addition, we propose an explanation for the "Fermi pockets" inferred from
quantum oscillations in terms of a pseudogapped bilayer Fermi surface.


title:
Giant Kerr nonlinearities and slow optical solitons in coupled double
  quantum-wells

abstract:
  We show the formation of slow optical solitons in the asymmetric coupled
double quantum-wells (CQW) via a two-photon Raman resonance. With the
consideration of real parameters in AlGaAs-based CQW, we indicate the
possibility to have cancellation of the linear absorption and giant Kerr
nonlinearities. With the controllable balance between dispersion and nonlinear
effects in these solid-state based devices, this work may provide a practical
platform for nonlinear optical signal processing.


title:
Slow optical solitons via intersubband transitions in a semiconductor
  quantum well

abstract:
  We show the formation of bright and dark slow optical solitons based on
intersubband transitions in a semiconductor quantum well (SQW). Using the
coupled Schrodinger-Maxwell approach, we provide both analytical and numerical
results. Such a nonlinear optical process may be used for the control
technology of optical delay lines and optical buffers in the SQW solid-state
system. With appropriate parameters, we also show the generation of a large
cross-phase modulation (XPM). Since the the intersubband energy level can be
easily tuned by an external bias voltage, the present investigation may open
the possibility for electrically controlled phase modulator in the solid-state
system.


title: Hybrid phase-space simulation method for interacting Bose fields

abstract:
  We introduce an approximate phase-space technique to simulate the quantum
dynamics of interacting bosons. With the future goal of treating Bose-Einstein
condensate systems, the method is designed for systems with a natural
separation into highly occupied (condensed) modes and lightly occupied modes.
The method self-consistently uses the Wigner representation to treat highly
occupied modes and the positive-P representation for lightly occupied modes. In
this method, truncation of higher-derivative terms from the Fokker-Planck
equation is usually necessary. However, at least in the cases investigated
here, the resulting systematic error, over a finite time, vanishes in the limit
of large Wigner occupation numbers. We tested the method on a system of two
interacting anharmonic oscillators, with high and low occupations,
respectively. The Hybrid method successfully predicted atomic quadratures to a
useful simulation time 60 times longer than that of the positive-P method. The
truncated Wigner method also performed well in this test. For the prediction of
the correlation in a quantum nondemolition measurement scheme, for this same
system, the Hybrid method gave excellent agreement with the exact result, while
the truncated Wigner method showed a large systematic error.


title:
Suppression of absorption by quantum interference in intersubband
  transitions of tunnel-coupled double quantum wells

abstract:
  We propose and analyze an efficient scheme for suppressing the absorption of
a weak probe field based on intersubband transitions in a four-level asymmetric
coupled-quantum well (CQW) driven coherently by a probe laser field and a
control laser field. By using the numerical simulation, we find that the
magnitude of the transient absorption of the probe field is smaller than the
three-level system based on the electromagnetically induced transparency (EIT)
at line center of the probe transition, moreover, comparing with the scheme in
three-level asymmetric double QW system, the transparency hole of the present
work is much broader. By analyzing the steady-state process analytically and
numerically, our results show that the probe absorption can be completely
eliminated under the condition of Raman resonance (i.e. two-photon detuning is
zero). Besides, we can observe one transparency window without requiring one-
or two-photon detuning exactly vanish. This investigation may provide the
possible scheme for EIT in solids by using CQW.


title:
Atom-Pair Tunneling and Quantum Phase Transition in Strong Interaction
  Regime

abstract:
  We propose a Hamiltonian of ultracold spinless atoms in optical lattices
including the two-body interaction of nearest neighbors, which reduces to the
Bose-Hubbard model in weak interaction limit. An atom-pair hoping term
appearing in the new Hamiltonian explains naturally the recent experimental
observation of correlated tunneling in a double-well trap with strong atom-atom
interactions and moreover leads to a new dynamic process of atom-pair tunneling
where strongly interacting atoms can tunnel back and forth as a fragmented
pair. Finally a new dynamics of oscillations induced by the atom-pair tunneling
is found in the strong interaction regime, where the Bose-Hubbard model gives
rise to the insulator state with fixed time-averaged value of
atom-occupation-number only. Quantum phase transitions between two quantum
phases characterized by degenerate and non-degenerate ground states are shown
to be coinciding with the Landau second-order phase transition theory. In the
system of finite atom-number the degeneracy of ground states can be removed by
quantum tunneling for the even-number of atoms but not for the odd-number.


title: On the semimartingale property of discounted asset-price processes

abstract:
  A financial market model where agents trade using realistic combinations of
buy-and-hold strategies is considered. Minimal assumptions are made on the
discounted asset-price process - in particular, the semimartingale property is
not assumed. Via a natural market viability assumption, namely, absence of
arbitrages of the first kind, we establish that discounted asset-prices have to
be semimartingales. In a slightly more specialized case, we extend the previous
result in a weakened version of the Fundamental Theorem of Asset Pricing that
involves strictly positive supermartingale deflators rather than Equivalent
Martingale Measures.


title: Partition statistics and quasiweak Maass forms

abstract:
  Andrews recently introduced k-marked Durfee symbols, which are a
generalization of partitions that are connected to moments of Dyson's rank
statistic. He used these connections to find identities relating their
generating functions as well as to prove Ramanujan-type congruences for these
objects and find relations between.
  In this paper we show that the hypergeometric generating functions for these
objects are natural examples of quasimock theta functions, which are defined as
the holomorphic parts of weak Maass forms and their derivatives. In particular,
these generating functions may be viewed as analogs of Ramanujan's mock theta
functions with arbitrarily high weight. We use the automorphic properties to
prove the existence of infinitely many congruences for the Durfee symbols.
Furthermore, we show that as k varies, the modularity of the k-marked Durfee
symbols is precisely dictated by the case k=2. Finally, we use this relation in
order to prove the existence of general congruences for rank moments in terms
of level one modular forms of bounded weight.


title:
Nuclear Muon Capture in Hydrogen and its Interplay with Muon Atomic
  Physics

abstract:
  The singlet capture rate $\Lambda_S$ for the semileptonic weak process $\mu+p
\to n+\nu_\mu$ has been measured in the MuCap experiment. The novel
experimental technique is based on stopping muons in an active target,
consisting of a time projection chamber operating with ultra-pure hydrogen.
This allows the unambiguous determination of the pseudoscalar form factor $g_P$
of the charged electroweak current of the nucleon. Our first result
$g_P(q^2=-0.88 m^2_\mu) = 7.3 \pm 1.1 $ is consistent with accurate theoretical
predictions and constitutes an important test of QCD symmetries. Additional
data are being collected with the aim of a three-fold reduction of the
experimental uncertainties. Building on the developed advanced techniques, the
new MuSun experiment is being planned to measure the muon capture rate on the
deuteron to 1.5% precision. This would provide the by far most accurate
experimental information on the axial current interacting with the two-nucleon
system and determine the low energy constant $L_{1A}$ relevant for solar
neutrino reactions.
  Muon induced atomic and molecular processes represent challenges as well as
opportunities for this science program, and their interplay with the main
nuclear and weak-interaction physics aspects will be discussed.


title: Physical Properties of Tidal Features in Interacting Disk Galaxies

abstract:
  We explore tidal interactions of a galactic disk with Toomre parameter Q ~ 2
embedded in rigid halo/bulge with a point mass companion moving in a prescribed
parabolic orbit. Tidal interactions produce well-defined spiral arms and
extended tidal features such as bridge and tail that are all transient, but
distinct in nature. In the extended disks, strong tidal force is able to lock
the perturbed epicycle phases of the near-side particles to the perturber,
shaping them into a tidal bridge that corotates with the perturber. A tidal
tail develops at the opposite side as strongly-perturbed, near-side particles
overtake mildly-perturbed, far-side particles. The tail is essentially a narrow
material arm with a roughly logarithmic shape, dissolving with time because of
large velocity dispersions. Inside the disks where tidal force is relatively
weak, on the other hand, a two-armed logarithmic spiral pattern emerges due to
the kinematic alignment of perturbed particle orbits. While self-gravity makes
the spiral arms a bit stronger, the arms never become fully self-gravitating,
wind up progressively with time, and decay after the peak almost exponentially
in a time scale of ~ 1 Gyr. The arm pattern speed varying with both radius and
time converges to Omega-kappa/2 at late time, suggesting that the pattern speed
of tidally-driven arms may depend on radius in real galaxies. We present the
parametric dependences of various properties of tidal features on the tidal
strength, and discuss our findings in application to tidal spiral arms in
grand-design spiral galaxies. (Abridged)


title: Low heat conduction in white dwarf boundary layers?

abstract:
  X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton
provide new information on the boundary layers of their accreting white dwarfs.
Comparison of observations and models allows us to extract estimates for the
thermal conductivity in the accretion layer and reach conclusions on the
relevant physical processes. We calculate the structure of the dense thermal
boundary layer that forms under gravity and cooling at the white dwarf surface
on accretion of gas from a hot tenuous ADAF-type coronal inflow. The
distribution of density and temperature obtained allows us to calculate the
strength and spectrum of the emitted X-ray radiation. They depend strongly on
the values of thermal conductivity and mass accretion rate. We apply our model
to the dwarf nova system VW Hyi and compare the spectra predicted for different
values of the thermal conductivity with the observed spectrum. We find a
significant deviation for all values of thermal conductivity that are a sizable
fraction of the Spitzer conductivity. A good fit arises however for a
conductivity of about 1% of the Spitzer value. This also seems to hold for
other dwarf nova systems in quiescence. We compare this result with thermal
conduction in other astrophysical situations. The highly reduced thermal
conductivity in the boundary layer requires magnetic fields perpendicular to
the temperature gradient. Locating their origin in the accretion of magnetic
fields from the hot ADAF-type coronal flow we find that dynamical effects of
these fields will lead to a spatially intermittent, localized accretion
geometry at the white dwarf surface.


title:
Numerical extraction of de Haas - van Alphen frequencies from calculated
  band energies

abstract:
  A new algorithm for extracting de Haas-van Alphen frequencies and effective
masses from calculated band energies is presented. The algorithm creates an
interpolated k-space "super cell," which is broken into slices perpendicular to
the desired magnetic field direction. Fermi surface orbits are located within
each slice, and de Haas-van Alphen frequencies and effective masses are
calculated. Orbits are then matched across slices, and extremal orbits
determined. This technique has been successful in locating extremal orbits not
previously noticed in the complicated topology of existing UPt3 band-structure
data; these new orbits agree with experimental de Haas-van Alphen measurements
on this material, and solidify the case for a fully-itinerant model of UPt3.


title: Constraints on Gravitational Dipole Radiation from Pulsars

abstract:
  Recent suggestions for a modification of general relativity to provide an
alternative approach to gravity in connection with the dark energy (matter)
problem imply a long range vector component of the gravitational field. This
could lead to emission of gravitational dipole emission from objects such as
pulsars. Stringent observational limits on period changes of binary and
millisecond pulsars and their consistency with general relativity impose severe
limits on couplings of such forces. These bounds are tighter than those implied
by lunar laser ranging experiments.


title: An elementary optical gate for expanding entanglement web

abstract:
  We introduce an elementary optical gate for expanding polarization entangled
W states, in which every pair of photons are entangled alike. The gate is
composed of a pair of 50:50 beamsplitters and ancillary photons in the
two-photon Fock state. By seeding one of the photons in an $n$-photon W state
into this gate, we obtain an $(n+2)$-photon W state after post-selection. This
gate gives a better efficiency and a simpler implementation than previous
proposals for $\rm W$-state preparation.


title: R-parity violating supersymmetry, B_s mixing, and D_s -> l nu

abstract:
  Recently, it was pointed out that the mixing phase in the Bs-Bsbar system is
large, contrary to the expectations in the Standard Model as well as in minimal
flavour violation models. The leptonic decay widths of the D_s meson are also
found to be larger than expected. We show how a minimal set of four R-parity
violating lambda-prime type couplings can explain both these anomalies. We also
point out other phenomenological implications of such new physics.


title:
The necessary and sufficient condition for solvability of a partial
  integral equation

abstract:
  Let $T_1: L_2(\Omega^2) \to L_2(\Omega^2)$ be a partial integral operator
with the kernel from $C(\Omega^3)$ where $\Omega=[a,b ]^\nu.$ In this paper we
investigate solvability of a partial integral equation $f-\varkappa T_1 f=g_0$
in the space $L_2(\Omega^2)$ in the case when $\varkappa$ is a characteristic
number. We proved the theorem describing the necessary and sufficient condition
for solvability of the partial integral equation $f-\varkappa T_1 f=g_0.$


title: High energy properties of PKS 1830-211

abstract:
  We report on an analysis of X- and $\gamma$-ray observations of PKS 1830-211,
based on the long-term campaigns carried out by \emph{INTEGRAL} and COMPTEL.
The \emph{INTEGRAL} data currently available present a $33\sigma$ significance
detection in the 20-100 keV band, while the COMPTEL 6-years data provide a
$5.2\sigma$ significance detection in the 1-3 MeV energy band. At hard X-rays,
\emph{INTEGRAL} and supplementary \emph{SWIFT} observations show flux
variability on timescales of months. At $\gamma$-rays, the source shows
persistent emission over years. The hard X-ray spectrum is well represented by
a power-law model, with $\Gamma \sim 1.3$ in the 20-250 keV band. This photon
index is well consistent with the previous report of $\Gamma \sim 1.3$ obtained
at $E > 3.5$ keV from the best fit of \emph{XMM-Newton} data with a broken
power law model. The joint \emph{XMM-Newton}/\emph{INTEGRAL} spectrum presented
here is then fit with a broken power-law model and the parameters are refined
compared to the previous. The results show the photon index changes from $\sim
1.0$ to $\sim 1.3$ at a break energy $\sim 4$ keV. At MeV energies, the
spectrum softens to $\Gamma \sim 2.2$. These results, together with the EGRET
measurement at $E \ge 100$ MeV, constitute a broad-band spectrum containing the
peak of the power output at MeV energies, similar to most high-luminosity
$\gamma$-ray blazars. The measured spectral characterstics are then discussed
in the framework of the gravitational lens effects.


title: A Study on the Structure Functions and the radius of the Nucleons

abstract:
  We have investigated the properties of the structure functions of the
nucleons in the context of the statistical model using only the radius
parameter of the respective nucleons. The radius of the neutron has been
estimated and is found to be 0.8fm. It is interesting to observe that the
proton radius 0.865fm which exactly equals to the most accepted charge radius
of the proton and which in turn characterizes proton as a meso object, yields
reasonable results for the structure function and its properties. GT sum rule
has been investigated with some interesting conclusions.


title:
Phase diagram in the imaginary chemical potential region and extended Z3
  symmetry

abstract:
  Phase transitions in the imaginary chemical potential region are studied by
the Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model that possesses the
extended Z3 symmetry. The extended Z3 invariant quantities such as the
partition function, the chiral condensate and the modifed Polyakov loop have
the Roberge-Weiss (RW) periodicity. There appear four types of phase
transitions; deconfinement, chiral, Polykov-loop RW and chiral RW transitions.
The orders of the chiral and deconfinement transitions depend on the presence
or absence of current quark mass, but those of the Polykov-loop RW and chiral
RW transitions do not. The scalar-type eightquark interaction newly added in
the model makes the chiral transition line shift to the vicinity of the
deconfiment transition line.


title:
Mathematical Aspects and Numerical Computations of an Inverse Boundary
  Value Identification Using the Adjoint Method

abstract:
  The purpose of this study is to show some mathematical aspects of the adjoint
method that is a numerical method for the Cauchy problem, an inverse boundary
value problem. The adjoint method is an iterative method based on the
variational formulation, and the steepest descent method minimizes an objective
functional derived from our original problem. The conventional adjoint method
is time-consuming in numerical computations because of the Armijo criterion,
which is used to numerically determine the step size of the steepest descent
method. It is important to find explicit conditions for the convergence and the
optimal step size. Some theoretical results about the convergence for the
numerical method are obtained. Through numerical experiments, it is concluded
that our theories are effective.


title:
Zero-temperature generalized phase diagram of the 4d transition metals
  under pressure

abstract:
  We use an accurate implementation of density functional theory (DFT) to
calculate the zero-temperature generalized phase diagram of the 4$d$ series of
transition metals from Y to Pd as a function of pressure $P$ and atomic number
$Z$. The implementation used is full-potential linearized augmented plane waves
(FP-LAPW), and we employ the exchange-correlation functional recently developed
by Wu and Cohen. For each element, we obtain the ground-state energy for
several crystal structures over a range of volumes, the energy being converged
with respect to all technical parameters to within $\sim 1$ meV/atom. The
calculated transition pressures for all the elements and all transitions we
have found are compared with experiment wherever possible, and we discuss the
origin of the significant discrepancies. Agreement with experiment for the
zero-temperature equation of state is generally excellent. The generalized
phase diagram of the 4$d$ series shows that the major boundaries slope towards
lower $Z$ with increasing $P$ for the early elements, as expected from the
pressure induced transfer of electrons from $sp$ states to $d$ states, but are
almost independent of $P$ for the later elements. Our results for Mo indicate a
transition from bcc to fcc, rather than the bcc-hcp transition expected from
$sp$-$d$ transfer.


title:
Method of Fundamental Solutions with Optimal Regularization Techniques
  for the Cauchy Problem of the Laplace Equation with Singular Points

abstract:
  The purpose of this study is to propose a high-accuracy and fast numerical
method for the Cauchy problem of the Laplace equation. Our problem is directly
discretized by the method of fundamental solutions (MFS). The Tikhonov
regularization method stabilizes a numerical solution of the problem for given
Cauchy data with high noises. The accuracy of the numerical solution depends on
a regularization parameter of the Tikhonov regularization technique and some
parameters of MFS. The L-curve determines a suitable regularization parameter
for obtaining an accurate solution. Numerical experiments show that such a
suitable regularization parameter coincides with the optimal one. Moreover, a
better choice of the parameters of MFS is numerically observed. It is
noteworthy that a problem whose solution has singular points can successfully
be solved. It is concluded that the numerical method proposed in this paper is
effective for a problem with an irregular domain, singular points, and the
Cauchy data with high noises.


title: Excitation transfer in two two-level systems coupled to an oscillator

abstract:
  We consider a generalization of the spin-boson model in which two different
two-level systems are coupled to an oscillator, under conditions where the
oscillator energy is much less than the two-level system energies, and where
the oscillator is highly excited. We find that the two-level system transition
energy is shifted, producing a Bloch-Siegert shift in each two-level system
similar to what would be obtained if the other were absent. At resonances
associated with energy exchange between a two-level system and the oscillator,
the level splitting is about the same as would be obtained in the spin-boson
model at a Bloch-Siegert resonance. However, there occur resonances associated
with the transfer of excitation between one two-level system and the other, an
effect not present in the spin-boson model. We use a unitary transformation
leading to a rotated system in which terms responsible for the shift and
splittings can be identified. The level splittings at the anticrossings
associated with both energy exchange and excitation transfer resonances are
accounted for with simple two-state models and degenerate perturbation theory
using operators that appear in the rotated Hamiltonian.


title: Determination of the orbital parameters of binary pulsars

abstract:
  We present a simple method for determination of the orbital parameters of
binary pulsars, using data on the pulsar period at multiple observing epochs.
This method uses the circular nature of the velocity space orbit of Keplerian
motion and produces preliminary values based on two one dimensional searches.
Preliminary orbital parameter values are then refined using a computationally
efficient linear least square fit. This method works for random and sparse
sampling of the binary orbit. We demonstrate the technique on (a) the highly
eccentric binary pulsar PSR J0514-4002 (the first known pulsar in the globular
cluster NGC 1851) and (b) 47 Tuc T, a binary pulsar with a nearly circular
orbit.


title:
On the Throughput Allocation for Proportional Fairness in Multirate IEEE
  802.11 DCF under General Load Conditions

abstract:
  This paper presents a modified proportional fairness (PF) criterion suitable
for mitigating the \textit{rate anomaly} problem of multirate IEEE 802.11
Wireless LANs employing the mandatory Distributed Coordination Function (DCF)
option. Compared to the widely adopted assumption of saturated network, the
proposed criterion can be applied to general networks whereby the contending
stations are characterized by specific packet arrival rates, $\lambda_s$, and
transmission rates $R_d^{s}$.
  The throughput allocation resulting from the proposed algorithm is able to
greatly increase the aggregate throughput of the DCF while ensuring fairness
levels among the stations of the same order of the ones available with the
classical PF criterion. Put simply, each station is allocated a throughput that
depends on a suitable normalization of its packet rate, which, to some extent,
measures the frequency by which the station tries to gain access to the
channel. Simulation results are presented for some sample scenarios, confirming
the effectiveness of the proposed criterion.


title: Regularized estimation of large covariance matrices

abstract:
  This paper considers estimating a covariance matrix of $p$ variables from $n$
observations by either banding or tapering the sample covariance matrix, or
estimating a banded version of the inverse of the covariance. We show that
these estimates are consistent in the operator norm as long as $(\log
p)/n\to0$, and obtain explicit rates. The results are uniform over some fairly
natural well-conditioned families of covariance matrices. We also introduce an
analogue of the Gaussian white noise model and show that if the population
covariance is embeddable in that model and well-conditioned, then the banded
approximations produce consistent estimates of the eigenvalues and associated
eigenvectors of the covariance matrix. The results can be extended to smooth
versions of banding and to non-Gaussian distributions with sufficiently short
tails. A resampling approach is proposed for choosing the banding parameter in
practice. This approach is illustrated numerically on both simulated and real
data.


title: A paradigm for entanglement and information swapping of two qubits

abstract:
  Based on a general unitary operation of two-qubit system, we investigate the
dynamics of entanglement, entropy and purity. Distinctive features in the
different initial states settings of an interacting bipartite system are
explored. The striking effects of initial product states on entanglement shows
that zeros entanglement can be obtained during the development of the
interaction.


title: On group theory for quantum gates and quantum coherence

abstract:
  Finite group extensions offer a natural language to quantum computing. In a
nutshell, one roughly describes the action of a quantum computer as consisting
of two finite groups of gates: error gates from the general Pauli group P and
stabilizing gates within an extension group C. In this paper one explores the
nice adequacy between group theoretical concepts such as commutators, normal
subgroups, group of automorphisms, short exact sequences, wreath products...
and the coherent quantum computational primitives. The structure of the single
qubit and two-qubit Clifford groups is analyzed in detail. As a byproduct, one
discovers that M20, the smallest perfect group for which the commutator
subgroup departs from the set of commutators, underlies quantum coherence of
the two-qubit system. One recovers similar results by looking at the
automorphisms of a complete set of mutually unbiased bases.


title:
A Macro-Element for Dynamic Soil-Structure Interaction Analyses of
  Shallow Foundations

abstract:
  The scope of the paper is to present some aspects of the development of a
"macro-element" for dynamic soil-structure interaction analyses of shallow
foundations. Initially the concept of "macro-element" is introduced and is
illustrated with the aid of a very simple example originating from structural
engineering. Then the link is made with the modeling of the dynamic response of
shallow foundations and the objectives and structure of such a tool are
described with reference to the specific configuration of a circular footing
resting on the surface of a heterogeneous purely cohesive soil. The principal
features of the "macro-element" are then presented; the soil-structure
interaction domain is reduced to a point that coincides with the center of the
footing and all the (material and geometric) non-linearities are lumped at this
point. A discussion on the most appropriate way to treat these non-linearities
is undertaken based on experience gained with earlier works. It is suggested
that the non-linearities be incorporated in the model within a unified
formalism making use of the theory of multi-mechanism plasticity. Initial
results concerning the definition of the ultimate surface for such a plasticity
model, corresponding to the seismic bearing capacity of the foundation, are
finally presented.


title:
Rupture sismique des fondations par perte de capacit\'e portante: Le cas
  des semelles circulaires

abstract:
  Within the context of earthquake-resistant design of shallow foundations, the
present study is concerned with the determination of the seismic bearing
capacity of a circular footing resting on the surface of a heterogene-ous
purely cohesive semi-infinite soil layer. In the first part of the paper, a
database, containing case histories of civil engineering structures that
sustained a foundation seismic bearing capacity failure, is briefly pre-sented,
aiming at a better understanding of the studied phenomenon and offering a
number of case studies useful for validation of theoretical computations. In
the second part of the paper, the aforementioned problem is addressed using the
kinematic approach of the Yield Design theory, thus establishing optimal upper
bounds for the ultimate seismic loads supported by the soil-footing system. The
results lead to the establishment of some very simple guidelines that extend
the existing formulae for the seismic bearing capacity contained in the
European norms (proposed for strip footings on homogeneous soils) to the case
of circular footings and to that of heterogeneous cohesive soils.


title: Geometric phases and quantum phase transitions

abstract:
  Quantum phase transition is one of the main interests in the field of
condensed matter physics, while geometric phase is a fundamental concept and
has attracted considerable interest in the field of quantum mechanics. However,
no relevant relation was recognized before recent work. In this paper, we
present a review of the connection recently established between these two
interesting fields: investigations in the geometric phase of the many-body
systems have revealed so-called "criticality of geometric phase", in which
geometric phase associated with the many-body ground state exhibits
universality, or scaling behavior in the vicinity of the critical point. In
addition, we address the recent advances on the connection of some other
geometric quantities and quantum phase transitions. The closed relation
recently recognized between quantum phase transitions and some of geometric
quantities may open attractive avenues and fruitful dialog between different
scientific communities.


title:
Measurement of the proton spectra from Non-Mesonic Weak Decay of
  $^5_{\Lambda}He$, $^7_{\Lambda}Li$ and $^{12}_{\Lambda}C$

abstract:
  The results of a measurement of the proton spectra following the Non--Mesonic
Weak Decay of $\mathrm{^5_{\Lambda}He}$, $\mathrm{^7_{\Lambda}Li}$ and
$\mathrm{^{12}_{\Lambda}C}$ are presented and discussed. The experiment was
performed at the ($e^+$ $e^-$) collider DA$\Phi$NE at Laboratori Nazionale di
Frascati of INFN. It is the first measurement for $\mathrm{^7_{\Lambda}Li}$,
and for all the spectra the lower limit on the energy of the protons is 15 MeV,
never reached before. All the spectra show a similar shape, namely a peak at
around 80 MeV as expected for the free $\Lambda p \to np$ weak reaction, with a
low energy rise that should be due to Final State Interactions and/or
two--nucleon induced weak processes. The decay spectrum of
$\mathrm{^5_{\Lambda}He}$ is somehow similar to the ones reported by previous
measurements and theoretical calculations, but the same doesn't happen for the
$\mathrm{^{12}_{\Lambda}C}$ one.


title: Business Cycle and Conserved Quantity in Economics

abstract:
  We propose a dynamical model for business cycle based on an optimal DI model.
In the model there exists a conserved quantity, which corresponds to the total
energy in a dynamical system. We found that the business cycle with the period
6 or 7 years is nicely reproduced, since the model predicts a periodic motion
in the conservative system.


title: Impact parameter model for GPD

abstract:
  We propose a model for the unpolarized generalized parton distribution
function (GPD) based on impact parameter representation and discuss its x and t
dependencies at large and small values of these variables.


title:
The impact of multipole and relativistic effects on photoionization and
  radiative recombination cross sections in hot plasmas

abstract:
  It is shown in the framework of the fully relativistic Dirac-Fock treatment
of photoionization and radiative recombination processes that taking into
account all significant multipoles of the radiative field is of considerable
importance at electron energy higher than several keV. For the first time, we
show that the relativistic Maxwell-Bolzmann distribution of continuum electrons
should be used in hot thermal plasmas. This decreases the radiative
recombination rate coefficient up to several multipoles compared to the
non-relativistic distribution commonly used.


title:
The Spectral Lag of GRB060505: A Likely Member of the Long Duration
  Class

abstract:
  Two long gamma-ray bursts, GRB 060505 and GRB 060614, occurred in nearby
galaxies at redshifts of 0.089 and 0.125 respectively. Due to their proximity
and durations, deep follow-up campaigns to search for supernovae (SNe) were
initiated. However none were found in either case, to limits more than two
orders of magnitude fainter than the prototypical GRB-associated SN, 1998bw. It
was suggested that the bursts, in spite of their durations (4 and 102 s),
belonged to the population of short GRBs which has been shown to be unrelated
to SNe. In the case of GRB 060614 this argument was based on a number of
indicators, including the negligible spectral lag, which is consistent with
that of short bursts. GRB 060505 has a shorter duration, but no spectral lag
was measured. We present the spectral lag measurements of GRB 060505 using
Suzakus Wide Area Monitor and the Swift Burst Alert Telescope. We find that the
lag is 0.36+/- 0.05 s, inconsistent with the lags of short bursts and
consistent with the properties of long bursts and SN-GRBs. These results
support the association of GRB 060505 with other low-luminosity GRBs also found
in star-forming galaxies and indicates that at least some massive stars may die
without bright SNe.


title:
Spectrum and eigen functions of the operator $H_U f(x)\equiv
  f(U-1/x)/x^2$ and strange attractor's density for the mapping
  $x_{n+1}=1/(U-x_n)$

abstract:
  We solve exactly the spectral problem for the non-Hermitian operator $H_U
f(x)\equiv f(U-1/x)/x^2$. Despite the absence of orthogonality, the eigen
functions of this operator allow one to construct in a simple way the expansion
of an arbitrary function in series. Explicit formulas for the expansion
coefficients are presented. This problem is shown to be connected with that of
calculating the strange attractor's density for the map $x_{n+1}=1/(U-x_n)$.
The explicit formula for the strange attractor's density for this map is
derived. All results are confirmed by direct computer simulations.


title:
Thermodynamic versus Topological Phase Transitions: Cusp in the
  Kert\'esz Line

abstract:
  We present a study of phase transitions of the Curie--Weiss Potts model at
(inverse) temperature $\beta$, in presence of an external field $h$. Both
thermodynamic and topological aspects of these transitions are considered. For
the first aspect we complement previous results and give an explicit equation
of the thermodynamic transition line in the $\beta$--$h$ plane as well as the
magnitude of the jump of the magnetization (for $q \geqslant 3)$. The signature
of the latter aspect is characterized here by the presence or not of a giant
component in the clusters of a Fortuin--Kasteleyn type representation of the
model. We give the equation of the Kert\'esz line separating (in the
$\beta$--$h$ plane) the two behaviours. As a result, we get that this line
exhibits, as soon as $q \geqslant 3$, a very interesting cusp where it
separates from the thermodynamic transition line.


title: Smooth backfitting in generalized additive models

abstract:
  Generalized additive models have been popular among statisticians and data
analysts in multivariate nonparametric regression with non-Gaussian responses
including binary and count data. In this paper, a new likelihood approach for
fitting generalized additive models is proposed. It aims to maximize a smoothed
likelihood. The additive functions are estimated by solving a system of
nonlinear integral equations. An iterative algorithm based on smooth
backfitting is developed from the Newton--Kantorovich theorem. Asymptotic
properties of the estimator and convergence of the algorithm are discussed. It
is shown that our proposal based on local linear fit achieves the same bias and
variance as the oracle estimator that uses knowledge of the other components.
Numerical comparison with the recently proposed two-stage estimator [Ann.
Statist. 32 (2004) 2412--2443] is also made.


title: Shannon Information Capacity of Discrete Synapses

abstract:
  There is evidence that biological synapses have only a fixed number of
discrete weight states. Memory storage with such synapses behaves quite
differently from synapses with unbounded, continuous weights as old memories
are automatically overwritten by new memories. We calculate the storage
capacity of discrete, bounded synapses in terms of Shannon information. For
optimal learning rules, we investigate how information storage depends on the
number of synapses, the number of synaptic states and the coding sparseness.


title: Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy

abstract:
  The GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a
resolution of about 8 A in the FUV (1350 - 1750 A) and about 20 A in the NUV
(1950 - 2750 A) is used for a systematic search of Ly-a emitting galaxies at
low redshift. This aims at filling a gap between high-redshift surveys and a
small set of objects studied in detail in the nearby universe. A blind search
of 7018 spectra extracted in 5 deep exposures (5.65 sq.deg) has resulted in 96
Ly-a emitting galaxy candidates in the FUV domain, after accounting for
broad-line AGNs. The Ly-a EWs (equivalent width) are consistent with stellar
population model predictions and show no trends as a function of UV color or UV
luminosity, except a possible decrease in the most luminous that may be due to
small-number statistics. Their distribution in EW is similar to that at z about
3 but their fraction among star-forming galaxies is smaller. Avoiding uncertain
candidates, a sub-sample of 66 objects in the range 0.2 < z < 0.35 has been
used to build a Ly-a LF (luminosity function). The incompleteness due to
objects with significant Ly-a emission but a UV continuum too low for spectral
extraction has been evaluated. A comparison with H-a LF in the same redshift
domain is consistent with an average Ly-a/H-a of about 1 in about 15 % of the
star-forming galaxies. A comparison with high-redshift Ly-a LFs implies an
increase of the Ly-a luminosity density by a factor of about 16 from z about
0.3 to z about 3. By comparison with the factor 5 increase of the UV luminosity
density in the same redshift range, this suggests an increase of the average
Ly-a escape fraction with redshift.


title: Weak solution for compressible fluid models of Korteweg type

abstract:
  This work is devoted to proving existence of global weak solutions for a
general isothermal model of capillary fluids derived by J.E Dunn and J.Serrin
(1985) \cite{3DS}, which can be used as a phase transition model.
  We distinguish two cases when the dimension N=2 and N=1, in the first case we
need that $\frac{1}{\rho}\in L^{\infty}$, when N=1 we get a weak solution in
finite time in the energy space.


title: Improved evolutionary generation of XSLT stylesheets

abstract:
  This paper introduces a procedure based on genetic programming to evolve XSLT
programs (usually called stylesheets or logicsheets). XSLT is a general
purpose, document-oriented functional language, generally used to transform XML
documents (or, in general, solve any problem that can be coded as an XML
document). The proposed solution uses a tree representation for the stylesheets
as well as diverse specific operators in order to obtain, in the studied cases
and a reasonable time, a XSLT stylesheet that performs the transformation.
Several types of representation have been compared, resulting in different
performance and degree of success.


title: Quantum Crystals and Spin Chains

abstract:
  In this note, we discuss the quantum version of the melting crystal corner in
one, two, and three dimensions, generalizing the treatment for the quantum
dimer model. Using a mapping to spin chains we find that the two--dimensional
case (growth of random partitions) is integrable and leads directly to the
Hamiltonian of the Heisenberg XXZ ferromagnet. The three--dimensional case of
the melting crystal corner is described in terms of a system of coupled XXZ
spin chains. We give a conjecture for its mass gap and analyze the system
numerically.

categories: cond-mat.stat-mech hep-th math-ph math.MP


title: Holographic entanglement entropy probes (non)locality

abstract:
  We study the short-distance structure of geometric entanglement entropy in
certain theories with a built-in scale of nonlocality. In particular we examine
the cases of Little String Theory and Noncommutative Yang-Mills theory, using
their AdS/CFT descriptions. We compute the entanglement entropy via the
holographic ansatz of Ryu and Takayanagi to conclude that the area law is
violated at distance scales that sample the nonlocality of these models, being
replaced by an extensive volume law. In the case of the noncommutative model,
the critical length scale that reveals the area/volume law transition is
strongly affected by UV/IR mixing effects. We also present an argument showing
that Lorentz symmetry tends to protect the area law for theories with
field-theoretical density of states.


title: Geometrical Structures of Space-Time in General Relativity

abstract:
  Space-Time in general relativity is a dynamical entity because it is subject
to the Einstein field equations. The space-time metric provides different
geometrical structures: conformal, volume, projective and linear connection. A
deep understanding of them has consequences on the dynamical role played by
geometry. We present a unified description of those geometrical structures,
with a standard criterion of naturalness, and then we establish relationships
among them and try to clarify the meaning of associated geometric magnitudes.


title:
Existence of global weak solution for compressible fluid models with a
  capillary tensor for discontinuous interfaces

abstract:
  This work is devoted to the global existence of weak solution for a general
isothermal model of capillary fluids derived by C. Rohde, which can be used as
a phase transition model. This article is structured in the following way:
first of all inspired by the result by P.-L. Lions on the Navier-Stokes
compressible system we will show the global stability of weak solutions for our
system with isentropic pressure and next with general pressure. Next we will
consider perturbations close to a stable equilibrium as in the case of strong
solutions.


title: Variable selection in semiparametric regression modeling

abstract:
  In this paper, we are concerned with how to select significant variables in
semiparametric modeling. Variable selection for semiparametric regression
models consists of two components: model selection for nonparametric components
and selection of significant variables for the parametric portion. Thus,
semiparametric variable selection is much more challenging than parametric
variable selection (e.g., linear and generalized linear models) because
traditional variable selection procedures including stepwise regression and the
best subset selection now require separate model selection for the
nonparametric components for each submodel. This leads to a very heavy
computational burden. In this paper, we propose a class of variable selection
procedures for semiparametric regression models using nonconcave penalized
likelihood. We establish the rate of convergence of the resulting estimate.
With proper choices of penalty functions and regularization parameters, we show
the asymptotic normality of the resulting estimate and further demonstrate that
the proposed procedures perform as well as an oracle procedure. A
semiparametric generalized likelihood ratio test is proposed to select
significant variables in the nonparametric component. We investigate the
asymptotic behavior of the proposed test and demonstrate that its limiting null
distribution follows a chi-square distribution which is independent of the
nuisance parameters. Extensive Monte Carlo simulation studies are conducted to
examine the finite sample performance of the proposed variable selection
procedures.


title: Cascading Dynamics in Modular Networks

abstract:
  In this paper we study a simple cascading process in a structured
heterogeneous population, namely, a network composed of two loosely coupled
communities. We demonstrate that under certain conditions the cascading
dynamics in such a network has a two--tiered structure that characterizes
activity spreading at different rates in the communities. We study the dynamics
of the model using both simulations and an analytical approach based on
annealed approximation, and obtain good agreement between the two. Our results
suggest that network modularity might have implications in various
applications, such as epidemiology and viral marketing.


title:
Existence of axially symmetric solutions to the Vlasov-Poisson system
  depending on Jacobi's integral

abstract:
  We prove the existence of axially symmetric solutions to the Vlasov--Poisson
system in a rotating setting for sufficiently small angular velocity. The
constructed steady states depend on Jacobi's integral and the proof relies on
an implicit function theorem for operators.


title: Dust content of core-collapse supernova hosts

abstract:
  We study a small sample of z=0.1-0.6 core-collapse supernova (CCSN) host
galaxies. Continuum observations at 250GHz have been performed with MAMBO at
the IRAM-30m telescope. None of these sources has been detected and the
error-weighted mean flux is 0.25+/-0.32 mJy. Upper limits on their dust masses
are derived and the corresponding sample mean corresponds to 1.4 +/- 2.2 x 10^8
Msol. These results are comparable with previous submillimetre observations of
SN-Ia hosts performed by Farrah et al. and by Clements et al. We conclude that
CCSN hosts are not extreme at millimetre wavelengths, and as confirmed with the
optical luminosities of a subset of our sample, they are typical of the local
galaxy population.


title:
Low-energy signatures of charge and spin fluctuations in Raman and
  optical spectra of the cuprates

abstract:
  We calculate the optical and Raman response within a phenomenological model
of fermion quasiparticles coupled to nearly critical collective modes. We find
that, whereas critical scaling properties might be masked in optical spectra
due to charge conservation, distinct critical signatures of charge and spin
fluctuations can be detected in Raman spectra exploiting specific symmetry
properties. We compare our results with recent experiments on the cuprates.


title:
XANES analysis of structural changes in a transient photoexcited state
  of metalloporphyrin

abstract:
  We have performed a structural analysis of the Ni K-edge XANES spectrum of a
square planar coordination complex, Ni-tetramesitylporphyrin, Ni(II)TMP, in
dilute toluene solution. The fit of the spectrum was carried out in the frame
of the full multiple scattering (FMS) approach, via the MXAN program, starting
from a muffin-tin (MT) form of the molecular potential. We have applied the
MXAN analysis to the time-resolved XANES difference spectrum obtained between a
100 ps life-time photoexcited state of Ni(II)TMP (a relaxed triplet state, T1,
obtained by exciting the Soret band) and the ground state, S0. From our direct
simulation of the laser on/laser off difference spectrum, we obtain the
fraction of T1 population (0.41-0.63) A in agreement with optical transient
absorption determination, and a 0.05-0.1 A elongation of the d(Ni-N) and
d(Ni-C) distances. The overall uncertainty on these results mostly depends on
uncertainty on the chemical shift between the T1 and S0 state, that is assumed
a priori in the differential analysis. Still our results are in good agreement
with previous EXAFS data (obtained on a reconstructed absolute spectrum of the
T1 state). Our best fit corresponds to no chemical shift, 54% fraction of T1
state, and either a (0.04 +/- 0.01) elongation of the average d(Ni-N) or a
(0.06 +/- 0.01) elongation of the average d(Ni-pyrrol) when pyrrol rings are
treated as perfectly rigid bodies. This work demonstrates that XANES
spectroscopy can be used to provide structural information on square-planar
transition metal compounds by analysing the metal K-edge via MS method under
the MT approximation, and that XANES differential analysis can be successfully
applied to study electronic/structural relationships in transient photoexcited
species from time-resolved experiments.


title: Existence of solutions for compressible fluid models of Korteweg type

abstract:
  This work is devoted to the study of the initial boundary value problem for a
general non isothermal model of capillary fluids derived by J.E Dunn and
J.Serrin (1985), which can be used as a phase transition model. We distinguish
two cases, when the physical coefficients depend only on the density, and the
general case. In the first case we can work in critical scaling spaces, and we
prove global existence of solution and uniqueness for data close to a stable
equilibrium. For general data, existence and uniqueness is stated on a short
time interval.
  In the general case with physical coefficients depending on density and on
temperature, additional regularity is required to control the temperature in
$L^{\infty}$ norm. We prove global existence of solution close to a stable
equilibrium and local in time existence of solution with more general data.
Uniqueness is also obtained.


title: Interplay of topological and structural defects in the 2D XY model

abstract:
  The present work is devoted to the investigation of the interaction between
vortices (topological defects) and site-impurities (structural defects) in the
2D XY model and its influence on the well-known properties of the pure system.
The main goal is a theoretical description of the
Berezinskii-Kosterlitz-Thouless (BKT) temperature reduction by quenched
non-magnetic impurities, based on the vacancy-vortex interactions and the
vortex-pair dissociation mechanism of the transition. The non-magnetic impurity
interaction with a system of vortices can be found either from the
phenomenological theory of topological defects or from the Villain model. We
take both paths and compare the results obtained. Our prediction for the BKT
temperature reduction is confirmed by the available Monte Carlo data.


title:
Cauchy problem for viscous shallow water equations with a term of
  capillarity

abstract:
  In this article, we consider the compressible Navier-Stokes equation with
density dependent viscosity coefficients and a term of capillarity introduced
by Coquel et al in \cite{5CR}. This model includes at the same time the
barotropic Navier-Stokes equations with variable viscosity coefficients,
shallow-water system and the model of Rohde. We first study the well-posedness
of the model in critical regularity spaces with respect to the scaling of the
associated equations. In a functional setting as close as possibleto the
physical energy spaces, we prove global existence of solutions close to a
stable equilibrium, and local in time existence for solutions with general
initial data. Uniqueness is also obtained.


title:
Next-to-leading order QCD corrections to spin-dependent hadron-pair
  photoproduction

abstract:
  We compute the next-to-leading order QCD corrections to the ``direct'' part
of the spin-dependent cross section for hadron-pair photoproduction. The
calculation is performed using largely analytical methods. We present a brief
phenomenological study of our results focussing on the $K$-factors and scale
dependence of the next-to-leading order cross sections. This process is
relevant for the extraction of the gluon polarization in present and future
spin-dependent lepton-nucleon scattering experiments.


title: Further study of $D^+_s$ decays into $\pi^- \pi^+ \pi^+$

abstract:
  A Dalitz plot analysis of the OZI rule violating decay $D^+_s$ into $\pi^-
\pi^+ \pi^+$ is presented using different partial wave approaches. Scalar and
vector waves are described by $K$-matrices; their production is parameterized
in a $P$-vector approach. Alternatively, Breit-Wigner amplitudes and Flatt\'e
parametrization are used. Special emphasis is devoted to scalar mesons. The
$f_0(980)$ resonance provides the most significant contribution. Adding
$f_0(1500)$ to the scalar wave leads to an acceptable fit while introduction of
$f_0(1370)$ and/or $f_0(1710)$ does not lead to significant improvements. A
scan of the scalar wave optimizes for $M=1452\pm 22$ MeV/c$^2$. When
$f_0(1710)$ is added, the mass uncertainty increases, and the fit yields
$M=1470\pm 60$ MeV/c$^2$ which is fully compatible with the nominal $f_0(1500)$
mass. The scalar wave seems to exhibit a phase motion of 270$^{\circ}$ units in
the mass range from 1200 to 1650 MeV/c$^2$.


title: Mixed-rates asymptotics

abstract:
  A general method is presented for deriving the limiting behavior of
estimators that are defined as the values of parameters optimizing an empirical
criterion function. The asymptotic behavior of such estimators is typically
deduced from uniform limit theorems for rescaled and reparametrized criterion
functions. The new method can handle cases where the standard approach does not
yield the complete limiting behavior of the estimator. The asymptotic analysis
depends on a decomposition of criterion functions into sums of components with
different rescalings. The method is explained by examples from Lasso-type
estimation, $k$-means clustering, Shorth estimation and partial linear models.


title:
The generic points for the horocycle flow on a class of hyperbolic
  surfaces with infinite genus

abstract:
  A point is called generic for a flow preserving an infinite ergodic invariant
Radon measure, if its orbit satisfies the conclusion of the ratio ergodic
theorem for every pair of continuous functions with compact support and
non-zero integrals. The generic points for horocycle flows on hyperbolic
surfaces of finite genus are understood, but there are no results in infinite
genus. We give such a result, by characterizing the generic points for
$\Z^d$--covers.


title:
Early Experiences in Traffic Engineering Exploiting Path Diversity: A
  Practical Approach

abstract:
  Recent literature has proved that stable dynamic routing algorithms have
solid theoretical foundation that makes them suitable to be implemented in a
real protocol, and used in practice in many different operational network
contexts. Such algorithms inherit much of the properties of congestion
controllers implementing one of the possible combination of AQM/ECN schemes at
nodes and flow control at sources. In this paper we propose a linear program
formulation of the multi-commodity flow problem with congestion control, under
max-min fairness, comprising demands with or without exogenous peak rates. Our
evaluations of the gain, using path diversity, in scenarios as intra-domain
traffic engineering and wireless mesh networks encourages real implementations,
especially in presence of hot spots demands and non uniform traffic matrices.
We propose a flow aware perspective of the subject by using a natural
multi-path extension to current congestion controllers and show its performance
with respect to current proposals. Since flow aware architectures exploiting
path diversity are feasible, scalable, robust and nearly optimal in presence of
flows with exogenous peak rates, we claim that our solution rethinked in the
context of realistic traffic assumptions performs as better as an optimal
approach with all the additional benefits of the flow aware paradigm.


title:
Resampling and requantization of band-limited Gaussian stochastic
  signals with flat power spectrum

abstract:
  A theoretical analysis, aimed at characterizing the degradation induced by
the resampling and requantization processes applied to band-limited Gaussian
signals with flat power spectrum, available through their digitized samples, is
presented. The analysis provides an efficient algorithm for computing the
complete {joint} bivariate discrete probability distribution associated to the
true quantized version of the Gaussian signal and to the quantity estimated
after resampling and requantization of the input digitized sequence. The use of
Fourier transform techniques allows deriving {approximate} analytical
expressions for the quantities of interest, as well as implementing their
efficient computation. Numerical experiments are found to be in good agreement
with the theoretical results, and confirm the validity of the whole approach.


title: Maximal qubit tomography

abstract:
  A new qubit tomography protocol is introduced, based on a continuous positive
operator valued measure, which is supported by the set of pure states, and
equivariant under the symmetry group SO(3,R) of the qubit state space. Thus the
sample data for the tomography protocol is a discrete set of points on the
Bloch sphere obtained by a series of independent measurements on identical
replicas of the qubit. Although the maximum likelihood estimator uniquely
exists, it cannot be explicitly calculated. Instead, we present another
convenient, simple estimator, show that it is unbiased and calculate its
variance. Furthermore, a detailed account is given about known properties of
related discrete qubit state estimation protocols (like ``minimal qubit
tomography''), and the results are compared, discussed.


title: SPM Bulletin 24

abstract:
  1. A Wikipedia entry on topological games 2. On a fragment of the universal
Baire property for sigma^1_2 sets 3. The coarse classification of homogeneous
ultra-metric spaces 4. Ramsey-like embeddings 5. Proper and piecewise proper
families of reals 6. Measures and their random reals 7. Obtainable Sizes of
Topologies on Finite Sets 8. Spaces of R-places of rational function fields 9.
All properties in the Scheepers Diagram are linearly-sigma-additive.


title:
Linking rigidity transitions with enthalpic changes at the glass
  transition and the fragility of glass-forming liquids

abstract:
  A low temperature Monte Carlo dynamics of a Keating like oscillator model is
used to study the relationship between the nature of glasses from the viewpoint
of rigidity, and the strong-fragile behaviour of glass-forming liquids. The
model shows that a Phillips optimal glass formation with minimal enthalpic
changes is obtained under a cooling/annealing cycle when the system is
optimally constrained by the harmonic interactions, i.e. when it is
isostatically rigid. For these peculiar systems, the computed fragility shows
also a minimum, which demonstrates that isostatically rigid glasses are strong
(Arrhenius-like) glass-forming liquids. Experiments on chalcogenide and oxide
glass-forming liquids are discussed under this new perspective and confirm the
theoretical prediction for chalcogenide network glasses.


title: Very Special (de Sitter) Relativity

abstract:
  The effects of a non-vanishing value for the cosmological constant in the
scenario of Lorentz symmetry breaking recently proposed by Cohen and Glashow
(which they denote as Very Special Relativity) are explored and observable
consequences are pointed out.


title: Growth of balls of holomorphic sections and energy at equilibrium

abstract:
  Let X be a compact complex manifold endowed with a big line bundle L. We
define the energy at equilibrium of a weighted subset as the Monge-Ampere
energy of the associated extremal plurisubharmonic weight. We prove the
differentiability of the energy at equilibrium with respect to the weight, and
show that this energy describes the asymptotic behaviour as k goes to infinity
of the volume of the induced sup-norm unit ball in the space of global sections
of kL. As a consequence of these results, we extend Rumely's Robin-type formula
for the transfinite diameter. We also obtain an asymptotic description of the
analytic torsion and extend Yuan's equidistribution theorem for algebraic
points of small height to the case of a big line bundle.


title:
Direct evidence of enhanced Ga interdiffusion in InAs vertically aligned
  free-standing nanowires

abstract:
  We present direct evidence of enhanced Ga interdiffusion in InAs
free-standing nanowires grown at moderate temperatures by molecular beam
epitaxy on GaAs (111)B. Scanning electron microscopy together with X-ray
diffraction measurements in coplanar and grazing incidence geometries show that
nominally grown InAs NWs are actually made of In$_{0.86}$Ga$_{0.14}$As. Unlike
typical vapor-liquid-solid growth, these nanowires are formed by
diffusion-induced growth combined with strong interdiffusion from substrate
material. Based on the experimental results, a simple nanowire growth model
accounting for the Ga interdiffusion is also presented. This growth model could
be generally applicable to the molecular beam heteroepitaxy of III-V nanowires.


title: Properties of Active Galaxies Deduced from H I Observations

abstract:
  We completed a new survey for H I emission for a large, well-defined sample
of 154 nearby (z < 0.1) galaxies with type 1 AGNs. We make use of the extensive
database presented in a companion paper to perform a comprehensive appraisal of
the cold gas content in active galaxies and to seek new strategies to
investigate the global properties of the host galaxies and their relationship
to their central black holes (BHs). We show that the BH mass obeys a strong,
roughly linear relation with the host galaxy's dynamical mass. BH mass follows
a looser, though still highly significant, correlation with the maximum
rotation velocity of the galaxy, as expected from the known scaling between
rotation velocity and central velocity dispersion. Neither of these H I-based
correlations is as tight as the more familiar relations between BH mass and
bulge luminosity or velocity dispersion, but they offer the advantage of being
insensitive to the glare of the nucleus and therefore are promising new tools
for probing the host galaxies of both nearby and distant AGNs. We present
evidence for substantial ongoing BH growth in the most actively accreting AGNs.
In these nearby systems, BH growth appears to be delayed with respect to the
assembly of the host galaxy but otherwise has left no detectable perturbation
to its mass-to-light ratio or its global gas content. The host galaxies of type
1 AGNs, including those luminous enough to qualify as quasars, are generally
gas-rich systems, possessing a cold interstellar medium reservoir at least as
abundant as that in inactive galaxies of the same morphological type. This
calls into question current implementations of AGN feedback in models of galaxy
formation that predict strong cold gas depletion in unobscured AGNs. (Abridged)


title: Mixed 3-Sasakian structures and curvature

abstract:
  In this paper we deal with two classes of mixed metric 3-structures, namely
the mixed 3-Sasakian structures and the mixed metric 3-contact structures.
Firstly we study some properties of the curvature of mixed 3-Sasakian
structures, proving that any manifold endowed with such a structure is
Einstein. Then we prove the identity between the class of mixed 3-Sasakian
structures and the class of mixed metric 3-contact structures.