title:
Coulomb corrections to density and temperature of bosons in heavy ion
  collisions

abstract:
  A recently proposed method, based on quadrupole and multiplicity fluctuations
in heavy ion collisions, is modified in order to take into account distortions
due to the Coulomb field. This is particularly interesting for bosons produced
in heavy ion collisions, such as $d$ and $\alpha$ particles. We derive
temperatures and densities seen by the bosons and compare to similar
calculations for fermions. The resulting energy densities agree rather well
with each other and with the one derived from neutrons. This suggests that a
common phenomenon, such as the sudden opening of many reaction channels and/or
a liquid gas phase transition, is responsible for the agreement.


title: Sur deux formules de Frobenius et Stickelberger et inversion de Lagrange

abstract:
  We give a proof and extension of two formulas of Frobenius and Stickelberger
of Differential Calculus that they used in a fundamental paper concerning
elliptic functions theory. Our main ingredient is the introduction of a
bilinear form which is a vast generalization of Leibniz formula. This bilinear
form is also connected to the Lagrange product formula. As a corollary, we give
a different proof of a theorem of P.J. Olver.


title: Cosmological perturbations of massive gravity coupled to DBI Galileons

abstract:
  Certain scalar fields with higher derivative interactions and novel classical
and quantum mechanical properties - the Galileons - can be naturally
covariantized by coupling to nonlinear massive gravity in such a way that their
symmetries and number of degrees of freedom are unchanged. We study the
propagating degrees of freedom in these models around cosmologically
interesting backgrounds. We identify the conditions necessary for such a theory
to remain ghost free, and consider when tachyonic instabilities can be avoided.
We show that on the self-accelerating branch of solutions, the kinetic terms
for the vector and scalar modes of the massive graviton vanish, as in the case
of pure massive gravity.


title: Fluids in cosmology

abstract:
  We review the role of fluids in cosmology by first introducing them in
General Relativity and then by applying them to a FRW Universe's model. We
describe how relativistic and non-relativistic components evolve in the
background dynamics. We also introduce scalar fields to show that they are able
to yield an inflationary dynamics at very early times (inflation) and late
times (quintessence). Then, we proceed to study the thermodynamical properties
of the fluids and, lastly, its perturbed kinematics. We make emphasis in the
constrictions of parameters by recent cosmological probes.


title:
The imprint of inhomogeneous HeII reionization on the HI and HeII
  Ly-alpha forest

abstract:
  We use a set of AMR hydrodynamic simulations post-processed with the
radiative-transfer code RADAMESH to study how inhomogeneous HeII reionization
affects the intergalactic medium (IGM). We propagate radiation from active
galactic nuclei (AGNs) considering two scenarios for the time evolution of the
ionizing sources. We find that HeII reionization takes place in a very
inhomogeneous fashion, through the production of well separated bubbles of the
ionized phase that subsequently percolate. Overall, the reionization process is
extended in time and lasts for a redshift interval Delta z>1. At fixed gas
density, the temperature distribution is bimodal during the early phases of
HeII reionization and cannot be described by a simple effective equation of
state. When HeII reionization is complete, the IGM is characterized by a
polytropic equation of state with index gamma~1.20. This relation is
appreciably flatter than at the onset of the reionization process (gamma=1.56)
and also presents a much wider dispersion around the mean. We extract HI and
HeII Ly-alpha absorption spectra from the simulations and fit Voigt profiles to
them. We find that the regions where helium is doubly ionized are characterized
by different probability density functions of the curvature and of the Doppler
b parameters of the HI Ly-alpha forest as a consequence of the bimodal
temperature distribution during the early phases of HeII reionization. The
column-density ratio in HeII and HI shows a strong spatial variability. Its
probability density function rapidly evolves with time reflecting the
increasing volume fraction in which ionizing radiation is harder due to the AGN
contribution. Finally we show that the number density of the flux-transmission
windows per unit redshift and the mean size of the dark gaps in the HeII
spectra have the potential to distinguish between different reionization
scenarios. (abridged)


title: Luminosity of young Jupiters revisited. Massive cores make hot planets

abstract:
  The intrinsic luminosity of young Jupiters is of high interest for planet
formation theory. It is an observable quantity that is determined by important
physical mechanisms during formation, namely the accretion shock structure, and
even more fundamentally, the basic formation mechanism (core accretion or
gravitational instability). We study the impact of the core mass on the
post-formation entropy and luminosity of young giant planets forming via core
accretion with a supercritical shock (cold accretion). For this, we conduct
self-consistently coupled formation and evolution calculations of giant planets
with masses between 1 and 12 Jovian masses and core masses between 20 and 120
Earth masses. We find that the post-formation luminosity of massive giant
planets is very sensitive to the core mass. An increase of the core mass by a
factor 6 results in an increase of the post-formation luminosity of a 10 Jovian
mass planet by a factor 120. Due to this dependency, there is no single well
defined post-formation luminosity for core accretion, but a wide range. For
massive cores (~100 Earth masses), the post-formation luminosities of core
accretion planets become so high that they approach those in the hot start
scenario that is often associated with gravitational instability. For the
mechanism to work, it is necessary that the solids are accreted before or
during gas runaway accretion, and that they sink deep into the planet. We make
no claims whether or not such massive cores can actually form in giant planets.
But if yes, it becomes difficult to rule out core accretion as formation
mechanism based solely on luminosity for directly imaged planets that are more
luminous than predicted for low core masses. Instead of invoking gravitational
instability as the consequently necessary formation mode, the high luminosity
could also be caused simply by a more massive core.


title:
Local stellar kinematics from RAVE data: IV. Solar neighbourhood
  age-metallicity relation

abstract:
  We investigated the age-metallicity relation using a sample of 5691 F and G
type dwarfs from RAVE DR3 by applying several constraints: i) We selected stars
with surface gravities log g < 3.8 and effective temperatures in the
5310<T_{eff}(K)<7300 range and obtained a dwarf sample. ii) We plotted the
dwarfs in metallicity sub-samples in the T_{eff}-(J-K_s)_0 plane to compare
with the corresponding data of Gonzalez Hernandez & Bonifacio (2009) and
identified the ones in agreement. iii) We fitted the reduced dwarf sample
obtained from constraints (i) and (ii) to the Padova isochrones and
re-identified those which occupy the plane defined by isochrones with ages t <
13 Gyr. iv) Finally, we omitted dwarfs with total velocity errors larger than
10.63 km/s. We estimated the ages using the Bayesian procedure of Jorgensen &
Lindegren (2005). The largest age-metallicity slope was found for early F-type
dwarfs. We found steeper slopes when we plotted the data as a function of
spectral type rather than Galactic population. We noticed a substantial scatter
in metallicity distribution at all ages. The metal-rich old dwarfs turned out
to be G-type stars which can be interpreted as they migrated from the inner
disc or bulge.


title: Cosmological Simulations of Isotropic Conduction in Galaxy Clusters

abstract:
  Simulations of galaxy clusters have a difficult time reproducing the radial
gas-property gradients and red central galaxies observed to exist in the cores
of galaxy clusters. Thermal conduction has been suggested as a mechanism that
can help bring simulations of cluster cores into better alignment with
observations by stabilizing the feedback processes that regulate gas cooling,
but this idea has not yet been well tested with cosmological numerical
simulations. Here we present cosmological simulations of ten galaxy clusters
performed with five different levels of isotropic Spitzer conduction, which
alters both the cores and outskirts of clusters, but not dramatically. In the
cores, conduction flattens central temperature gradients, making them nearly
isothermal and slightly lowering the central density but failing to prevent a
cooling catastrophe there. Conduction has little effect on temperature
gradients outside of cluster cores because outward conductive heat flow tends
to inflate the outer parts of the intracluster medium (ICM) instead of raising
its temperature. In general, conduction tends reduce temperature inhomogeneity
in the ICM, but our simulations indicate that those homogenizing effects would
be extremely difficult to observe in ~5 keV clusters. Outside the virial
radius, our conduction implementation lowers the gas densities and temperatures
because it reduces the Mach numbers of accretion shocks. We conclude that
despite the numerous small ways in which conduction alters the structure of
galaxy clusters, none of these effects are significant enough to make the
efficiency of conduction easily measurable unless its effects are more
pronounced in clusters hotter than those we have simulated.


title:
Symmetry breaking via Kondo hybridization: Chiral nematic metal in
  Pr2Ir2O7

abstract:
  In frustrated magnets when magnetic ordering is suppressed down to low
temperature, the formation of a quantum spin liquid becomes a possibility. How
such a spin liquid manifests in the presence of conduction electrons is a
question with potentially rich physical consequences, particularly when both
the localized spins and conduction electrons reside on frustrated lattices. We
propose a novel mechanism for symmetry breaking in systems where conduction
electrons hybridize with a quantum spin liquid through Kondo couplings. We
apply this to the pyrochlore iridate Pr2Ir2O7, which exhibits an anomalous Hall
effect without clear indications of magnetic order. We show that Kondo
hybridization between the localized Pr pseudo-spins and Ir conduction electrons
breaks some of the spatial symmetries, in addition to time-reversal regardless
of the form ofthe coupling. These broken symmetries result in an anomalous Hall
conductivity and induce small magnetic, quadrupolar and charge orderings.
Further experimental signatures are proposed.


title: Note on Gauge Invariance and Causal Propagation

abstract:
  Interactions of gauge-invariant systems are severely constrained by several
consistency requirements. One is the preservation of the number of gauge
symmetries, another is causal propagation. For lower-spin fields, the emphasis
is usually put on gauge invariance that happens to be very selective by itself.
We demonstrate with an explicit example, however, that gauge invariance, albeit
indispensable for constructing interactions, may not suffice as a consistency
condition. The chosen example that exhibits this feature is the theory of a
massless spin-3/2 field coupled to electromagnetism. We show that this system
admits an electromagnetic background in which the spin-3/2 gauge field may move
faster than light. Requiring causal propagation rules out otherwise allowed
gauge-invariant couplings. This emphasizes the importance of causality analysis
as an independent test for a system of interacting gauge fields. We comment on
the implications of allowing new degrees of freedom and non-locality in a
theory, on higher-derivative gravity and Vasiliev's higher-spin theories.


title: Teasing bits of information out of the CMB energy spectrum

abstract:
  Departures of the Cosmic Microwave Background (CMB) frequency spectrum from a
blackbody - commonly referred to as spectral distortions - encode information
about the thermal history of the early Universe (redshift z < few x 10^6).
While the signal is usually characterized as mu- and y-type distortion, a
smaller residual (non-y/non-mu) distortion can also be created at intermediate
redshifts 10^4 < z < 3 x 10^5. Here, we construct a new set of observables,
mu_k, that describes the principal components of this residual distortion. The
principal components are orthogonal to temperature shift, y- and mu-type
distortion, and ranked by their detectability, thereby delivering a compression
of all valuable information offered by the CMB spectrum. This method provides
an efficient way of analyzing the spectral distortion for given experimental
settings, and can be applied to a wide range of energy-release scenarios. As an
illustration, we discuss the analysis of the spectral distortion signatures
caused by dissipation of small-scale acoustic waves and decaying/annihilating
particles for a PIXIE-type experiments. We provide forecasts for the expected
measurement uncertainties of model parameters and detections limits in each
case. We furthermore show that a PIXIE-type experiments can in principle
distinguish dissipative energy release from particle decays for a nearly
scale-invariant primordial power spectrum with small running. Future CMB
spectroscopy thus offers a unique probe of physical processes in the primordial
Universe.


title:
Galaxy and Mass Assembly (GAMA): Witnessing the assembly of the cluster
  Abell 1882

abstract:
  We present a combined optical and X-ray analysis of the rich cluster Abell
1882 with the aim of identifying merging substructure and understanding the
recent assembly history of this system. Our optical data consist of spectra
drawn from the Galaxy and Mass Assembly (GAMA) survey, which lends itself to
this kind of detailed study thanks to its depth and high spectroscopic
completeness. We use 283 spectroscopically confirmed cluster members to detect
and characterize substructure. We complement the optical data with X-ray data
taken with both Chandra and XMM. Our analysis reveals that A1882 harbors two
main components, A1882A and A1882B, which have a projected separation of 2Mpc
and a line of sight velocity difference of v_{los}=-428km/s. The primary
system, A1882A, has velocity dispersion sigma_v=500km/s and Chandra (XMM)
temperature kT=3.57keV (3.31keV) while the secondary, A1882B, has
sigma_v=457km/s and Chandra (XMM) temperature kT=2.39keV (2.12keV). The optical
and X-ray estimates for the masses of the two systems are consistent within the
uncertainties and indicate that there is twice as much mass in A1882A
(M_{500}=1.5-1.9x10^{14}Msolar) when compared with A1882B
(M_{500}=0.8-1.0x10^{14}Msolar). We interpret the A1882A/A1882B system as being
observed prior to a core passage. Supporting this interpretation is the large
projected separation of A1882A and A1882B and the dearth of evidence for a
recent (<2Gyr) major interaction in the X-ray data. Two-body analyses indicate
that A1882A and A1882B form a bound system with bound incoming solutions
strongly favored. We compute blue fractions of f_b=0.28 and 0.18 for the
spectroscopically confirmed member galaxies within r_{500} of the centers of
A1882A and A1882B, respectively. These blue fractions do not differ
significantly from the blue fraction measured from an ensemble of 20 clusters
with similar mass and redshift.


title:
Area laws in a many-body localized state and its implications for
  topological order

abstract:
  The question whether Anderson insulators can persist to finite-strength
interactions - a scenario dubbed many-body localization - has recently received
a great deal of interest. The origin of such a many-body localized phase has
been described as localization in Fock space, a picture we examine numerically.
We then formulate a precise sense in which a single energy eigenstate of a
Hamiltonian can be adiabatically connected to a state of a non-interacting
Anderson insulator. We call such a state a many-body localized state and define
a many-body localized phase as one in which almost all states are many-body
localized states. We explore the possible consequences of this; the most
striking is an area law for the entanglement entropy of almost all excited
states in a many-body localized phase. We present the results of numerical
calculations for a one-dimensional system of spinless fermions. Our results are
consistent with an area law and, by implication, many-body localization for
almost all states and almost all regions for weak enough interactions and
strong disorder. However, there are rare regions and rare states with much
larger entanglement entropies. Furthermore, we study the implications that
many-body localization may have for topological phases and self-correcting
quantum memories. We find that there are scenarios in which many-body
localization can help to stabilize topological order at non-zero energy
density, and we propose potentially useful criteria to confirm these scenarios.


title: A thermoelectric heat engine with ultracold atoms

abstract:
  Thermoelectric effects, such as the generation of a particle current by a
temperature gradient, have their origin in a reversible coupling between heat
and particle flows. These effects are fundamental probes for materials and have
applications to cooling and power generation. Here we demonstrate
thermoelectricity in a fermionic cold atoms channel, ballistic or diffusive,
connected to two reservoirs. We show that the magnitude of the effect and the
efficiency of energy conversion can be optimized by controlling the geometry or
disorder strength. Our observations are in quantitative agreement with a
theoretical model based on the Landauer-Bu ttiker formalism. Our device
provides a controllable model-system to explore mechanisms of energy conversion
and realizes a cold atom based heat engine.


title: PTF12gzk - A Rapidly Declining, High-Velocity Type Ic Radio Supernova

abstract:
  Only a few cases of type Ic supernovae (SNe) with high-velocity ejecta have
been discovered and studied. Here we present our analysis of radio and X-ray
observations of a Type Ic SN, PTF12gzk. The radio emission rapidly declined
less than 10 days after explosion, suggesting SN ejecta expanding at high
velocity (~0.3c). The radio data also indicate that the density of the
circumstellar material (CSM) around the supernova is lower by a factor of ~10
than the CSM around normal Type Ic SNe. Our observations of this rapidly
declining radio SN at a distance of 58 Mpc demonstrates the potential to detect
many additional radio SNe, given the new capabilities of the VLA (improved
sensitivity and dynamic scheduling), that are currently missed, leading to a
biased view of radio SNe Ic. Early optical discovery followed by rapid radio
observations would provide a full description of the ejecta velocity
distribution and CSM densities around stripped massive star explosions, as well
as strong clues about the nature of their progenitor stars.


title: Reentrant Phase Transitions in Rotating AdS Black Holes

abstract:
  We study the thermodynamics of higher-dimensional singly spinning
asymptotically AdS black holes in the canonical (fixed J) ensemble of extended
phase space, where the cosmological constant is treated as pressure and the
corresponding conjugate quantity is interpreted as thermodynamic volume. Along
with the usual small/large black hole phase transition, we find a new
phenomenon of reentrant phase transitions for all d>5 dimensions, in which a
monotonic variation of the temperature yields two phase transitions from large
to small and back to large black holes. This situation is similar to that seen
in multicomponent liquids.


title:
The protoplanetary disks in the nearby massive star forming region
  Cygnus OB2

abstract:
  The formation of stars in massive clusters is one of the main modes of the
star formation process. However, the study of massive star forming regions is
hampered by their typically large distances to the Sun. One exception to this
is the massive star forming region Cygnus OB2 in the Cygnus X region, at the
distance of about 1400 pc. Cygnus OB2 hosts very rich populations of massive
and low-mass stars, being the best target in our Galaxy to study the formation
of stars, circumstellar disks, and planets in presence of massive stars. In
this paper we combine a wide and deep set of photometric data, from the r band
to 24 micron, in order to select the disk bearing population of stars in Cygnus
OB2 and identify the class I, class II, and stars with transition and
pre-transition disks. We selected 1843 sources with infrared excesses in an
area of 1 degree x 1 degree centered on Cyg OB2 in several evolutionary stages:
8.4% class I, 13.1% flat-spectrum sources, 72.9% class II, 2.3% pre-transition
disks, and 3.3% transition disks. The spatial distribution of these sources
shows a central cluster surrounded by a annular overdensity and some clumps of
recent star formation in the outer region. Several candidate subclusters are
identified, both along the overdensity and in the rest of the association.


title: Explaining two circumnuclear star forming rings in NGC5248

abstract:
  The distribution of gas in the central kiloparsec of a galaxy has a
dynamically rapid evolution. Nonaxisymmetries in the gravitational potential of
the galactic disk, such as a large scale stellar bar or spiral, can lead to
significant radial motion of gaseous material from larger radii to the central
region. The large influx of gas and the subsequent star formation keep the
central region constantly changing. However, the ability of gas to reach the
nucleus proper to fuel an AGN phase is not guaranteed. Gas inflow can be halted
at a circumnuclear star forming ring several hundred parsec away. The nearby
galaxy NGC5248 is especially interesting in this sense since it is said to host
2 circumnuclear star forming rings at 100pc and 370pc from its quiescent
nucleus. Here we present new subarcsecond PdBI+30m CO(2-1) emission line
observations of the central region. For the first time the molecular gas
distribution at the smallest stellar ring is resolved into a gas ring,
consistent with the presence of a quiescent nucleus. However, the molecular gas
shows no ring structure at the larger ring. We combine analyses of the gaseous
and stellar content in the central kiloparsec of this galaxy to understand the
gas distribution and dynamics of this star forming central region. We discuss
the probability of two scenarios leading to the current observations, given our
full understanding of this system, and discuss whether there are really two
circumnuclear star forming rings in this galaxy.


title: Stellar population properties for a sample of hard X-ray AGNs

abstract:
  The aim of this paper is to study the stellar population of galaxies hosting
an active galactic nucleus (AGN). We studied a sub-sample of hard X-ray
emitting AGNs from the INTEGRAL and Swift catalogs which were previously
identified and characterized through optical spectroscopy. Our analysis
provides complementary information, namely age and metallicity, which is
necessary to complete the panoramic view of such interesting objects.
  We selected hard X-ray emitting objects identified as AGNs by checking their
optical spectra in search for absorption lines suitable for the stellar
population analysis. We obtained a final sample consisting of 20 objects with
redshift lower than 0.3. We used the full-spectrum fitting method and, in
particular, the penalized pixel one applying the PPXF code. After masking all
the regions affected by emission lines, we fitted the spectra with the MILES
single stellar population templates and we derived mass-weighted ages and
metallicities.
  Most of the objects in our sample show an old stellar population, but three
of them are characterized by a bimodal distribution with a non negligible
contribution from young stars. The values of the mass-weighted metallicity span
a large range of metallicity with most of them slightly above the solar value.
No relations between the stellar population properties and the morphological
ones have been found.


title: On quasinormal modes of asymptotically anti-de Sitter black holes

abstract:
  We consider the problem of quasinormal modes (QNM) for strongly hyperbolic
systems on stationary, asymptotically anti-de Sitter black holes, with very
general boundary conditions at infinity. We argue that for a time slicing
regular at the horizon the QNM should be identified with certain H^k
eigenvalues of the infinitesimal generator of the solution semigroup. Using
this definition we are able to prove directly that the quasinormal frequencies
form a discrete, countable subset of the complex plane, which in the globally
stationary case accumulates only at infinity. We avoid any need for meromorphic
extension, and the quasinormal modes are honest eigenfunctions of an operator
on a Hilbert space. Our results apply to any of the linear fields usually
considered (Klein-Gordon, Maxwell, Dirac etc.) on a stationary black hole
background, and do not rely on any separability or analyticity properties of
the metric. Our methods and results largely extend to the locally stationary
case. We provide a counter-example to the conjecture that quasinormal modes are
complete. We relate our approach directly to the approach via meromorphic
continuation.


title:
Are the halo occupation predictions consistent with large scale galaxy
  clustering?

abstract:
  We study how well we can reconstruct the 2-point clustering of galaxies on
linear scales, as a function of mass and luminosity, using the halo occupation
distribution (HOD) in several semi-analytical models (SAMs) of galaxy formation
from the Millennium Simulation. We find that HOD with Friends of Friends groups
can reproduce galaxy clustering better than gravitationally bound haloes. This
indicates that Friends of Friends groups are more directly related to the
clustering of these regions than the bound particles of the overdensities. In
general we find that the reconstruction works at best to 5% accuracy: it
underestimates the bias for bright galaxies. This translates to an
overestimation of 50% in the halo mass when we use clustering to calibrate
mass. We also found a degeneracy on the mass prediction from the clustering
amplitude that affects all the masses. This effect is due to the clustering
dependence on the host halo substructure, an indication of assembly bias. We
show that the clustering of haloes of a given mass increases with the number of
subhaloes, a result that only depends on the underlying matter distribution. As
the number of galaxies increases with the number of subhaloes in SAMs, this
results in a low bias for the HOD reconstruction. We expect this effect to
apply to other models of galaxy formation, including the real universe, as long
as the number of galaxies incresases with the number of subhaloes. We have also
found that the reconstructions of galaxy bias from the HOD model fails for low
mass haloes with M = 3-5x10^11 Msun/h. We find that this is because galaxy
clustering is more strongly affected by assembly bias for these low masses.


title: Quantization of Perturbations in an Inflating Elastic Solid

abstract:
  A sufficiently rigid relativistic elastic solid can be stable for negative
pressure values and thus is capable of driving a stage of accelerated
expansion. If a relativistic elastic solid drove an inflationary stage in the
early Universe, quantum mechanically excited perturbations would arise in the
medium. We quantize the linear scalar and tensor perturbations and investigate
the observational consequences of having such an inflationary period. We find
that slowly varying sound speeds of the perturbations and a slowing varying
equation of state of the solid can produce a slightly red-tilted scalar power
spectrum that agrees with current observational data. Even in the absence of
nonadiabatic pressures, perturbations evolve on superhorizon scales, due to the
shear stresses within the solid. As such, the spectra of perturbations are in
general sensitive to the details of the end of inflation and we characterize
this dependence. Interestingly, we uncover here accelerating solutions for
elastic solids with (1 + P/\rho) significantly greater than 0 that nevertheless
have nearly scale-invariant scalar and tensor spectra. Beyond theoretical
interest, this may allow for the possibility of viable inflationary
phenomenology relatively far from the de Sitter regime.


title:
Polarization Controlled Ohmic to Schottky Transition at a Metal/Doped
  Ferroelectric Interface

abstract:
  Ferroelectric polar displacements have recently been observed in conducting
electron-doped BaTiO3. The co-existence of a ferroelectric phase and
conductivity opens the door to new functionalities which may provide a unique
route for novel device applications. Using first-principles methods and
electrostatic modeling we explore the effect that the switchable polarization
of electron-doped BaTiO3 (n-BaTiO3) has on the electronic properties of the
SrRuO3/n-BaTiO3 (001) interface. Ferroelectric polarization controls the
accumulation or depletion of electron charge at the interface, and the
associated bending of the n-BTO conduction band determines the transport regime
across the interface. The interface exhibits a Schottky tunnel barrier for one
polarization orientation, whereas an Ohmic contact is present for the opposite
polarization orientation, leading to a large change in interface resistance
associated with polarization reversal. Calculations reveal a large (five orders
of magnitude) change in the interface resistance as a result of polarization
switching.


title: Dispersive Hydrodynamics in Viscous Fluid Conduits

abstract:
  The evolution of the interface separating a conduit of light, viscous fluid
rising buoyantly through a heavy, more viscous, exterior fluid at small
Reynolds numbers is governed by the interplay between nonlinearity and
dispersion. Previous authors have proposed an approximate model equation based
on physical arguments, but a precise theoretical treatment for this two fluid
system with a free boundary is lacking. Here, a derivation of the interfacial
equation via a multiple scales, perturbation technique is presented.
Perturbations about a state of vertically uniform, laminar conduit flow are
considered in the context of the Navier-Stokes equations with appropriate
boundary conditions. The ratio of interior to exterior viscosities is the small
parameter used in the asymptotic analysis, which leads systematically to a
maximal balance between buoyancy driven, nonlinear self-steepening and viscous,
interfacial stress induced, nonlinear dispersion. This results in a scalar,
nonlinear partial differential equation describing large amplitude dynamics of
the cross-sectional area of the intrusive fluid conduit, in agreement with
previous derivations. The leading order behavior of the two fluid system is
completely characterized in terms of the interfacial dynamics. The regime of
model validity is characterized and shown to agree with previous experimental
studies. Viscous fluid conduits provide a robust setting for the study of
nonlinear, dispersive wave phenomena.


title: Index theory and dynamical symmetry enhancement near IIB horizons

abstract:
  We show that the number of supersymmetries of IIB black hole horizons is N=2
N_- + 2 index(D_\lambda), where index(D_\lambda) is the index of the Dirac
operator twisted with the line bundle \lambda^{1/2} of IIB scalars, and N_- is
the dimension of the kernel of a horizon Dirac operator which depends on IIB
fluxes. Therefore, all IIB horizons preserve an even number of supersymmetries.
In addition if the horizons have non-trivial fluxes and N_- is nonzero, then
index(D_\lambda) is non-negative, and the horizons admit an sl(2,R) symmetry
subalgebra. This provides evidence that all such horizons have an AdS/CFT dual.
Furthermore if the orbits of sl(2,R) are two-dimensional, the IIB horizons are
warped products AdS_2 X S.


title:
The MaGICC Baryon Cycle: The Enrichment History of Simulated Disc
  Galaxies

abstract:
  Using cosmological galaxy formation simulations from the MaGICC project,
spanning more than three magnitudes in stellar mass (~10^7-3x10^{10} Msun), we
trace the baryonic cycle of infalling gas from the virial radius through to its
participation in the star formation process. An emphasis is placed upon the
temporal history of chemical enrichment during its passage through the corona
and CGM. We derive the distributions of time between gas crossing the virial
radius and being accreted to the star forming region (which allows mixing
within the corona), as well as the time between gas being accreted to the star
forming region and then forming stars (which allows mixing within the disc).
Significant numbers of stars are formed from gas that cycles back through the
hot halo after first accreting to the star forming region. Gas entering high
mass galaxies is pre-enriched in low mass proto-galaxies prior to entering the
virial radius of the central progenitor, with only small amounts of primordial
gas accreted, even at high redshift (z~5). After entering the virial radius,
significant further enrichment occurs prior to the accretion of the gas to the
star forming region, with gas that is feeding the star forming region
surpassing 0.1Z by z=0. Mixing with halo gas, itself enriched via galactic
fountains, is thus crucial in determining the metallicity at which gas is
accreted to the disc. The lowest mass simulation (Mvir~2x10^{10}Msun, with
M*~10^7Msun), by contrast, accretes primordial gas through the virial radius
and onto the disc at all times. Much like the classical analytical solutions to
the `G-dwarf problem', overproduction of low-metallicity stars is ameliorated
by the inefficiency of star formation. Finally, gas outflow/metal removal rates
from star forming regions as a function of galactic mass are presented.


title:
$H\rightarrow \gamma\gamma$ as a Triangle Anomaly: Possible Implications
  for the Hierarchy Problem

abstract:
  The Standard Model calculation of $H\rightarrow\gamma\gamma$ has the curious
feature of being finite but regulator-dependent. While dimensional
regularization yields a result which respects the electromagnetic Ward
identities, additional terms which violate gauge invariance arise if the
calculation is done setting $d=4$. This discrepancy between the $d=4-\epsilon$
and $d=4$ results is recognized as a true ambiguity which must be resolved
using physics input; as dimensional regularization respects gauge invariance,
the $d=4-\epsilon$ calculation is accepted as the correct SM result. However,
here we point out another possibility; working in analogy with the gauge chiral
anomaly, we note that it is possible that the individual diagrams do violate
the electromagnetic Ward identities, but that the gauge-invariance-violating
terms cancel when all contributions to $H\rightarrow\gamma\gamma$, both from
the SM and from new physics, are included. We thus examine the consequences of
the hypothesis that the $d=4$ calculation is valid, but that such a
cancellation occurs. We work in general renormalizable gauge, thus avoiding
issues with momentum routing ambiguities. We point out that the
gauge-invariance-violating terms in $d=4$ arise not just for the diagram
containing a SM $W^{\pm}$ boson, but also for general fermion and scalar loops,
and relate these terms to a lack of shift invariance in Higgs tadpole diagrams.
We then derive the analogue of "anomaly cancellation conditions", and find
consequences for solutions to the hierarchy problem. In particular, we find
that supersymmetry obeys these conditions, even if it is softly broken at an
arbitrarily high scale.


title: Energy cascade and scaling in supersonic isothermal turbulence

abstract:
  Supersonic turbulence plays an important role in a number of extreme
astrophysical and terrestrial environments, yet its understanding remains
rudimentary. We use data from a three-dimensional simulation of supersonic
isothermal turbulence to reconstruct an exact fourth-order relation derived
analytically from the Navier-Stokes equations (Galtier and Banerjee, Phys. Rev.
Lett., vol. 107, 2011, p. 134501). Our analysis supports a Kolmogorov-like
inertial energy cascade in supersonic turbulence previously discussed on a
phenomenological level. We show that two compressible analogues of the
four-fifths law exist describing fifth- and fourth-order correlations, but only
the fourth-order relation remains `universal' in a wide range of Mach numbers
from incompressible to highly compressible regimes. A new approximate relation
valid in the strongly supersonic regime is derived and verified. We also
briefly discuss the origin of bottleneck bumps in simulations of compressible
turbulence.


title: Geometrie und Astronomie im Stadtplan des hethitischen Sarissa

abstract:
  The Hittite city Sarissa was founded in the 16th century BC and has been
systematically constructed. The city gates and the bigger public buildings were
arranged at about 45{\deg} relative to the cardinal directions. However, one of
the temples features a remarkable deviation from this general orientation. The
following analysis shows that both, the general orientation of the public
buildings and the deviation of one of the temples are related to astronomical
observations, particularly to the course of the sun, and maybe also to some
special points of the course of the Venus.


title: Higgs boson decays to quarkonia and the Hccbar coupling

abstract:
  In this paper we discuss decays of the Higgs boson to quarkonia in
association with a photon. We identify a new mechanism for producing such final
states in Higgs decays that leads to predictions for the decay rates that
differ by an order of magnitude from previous estimates. Although the branching
ratios for these processes are still small, the processes are experimentally
clean, and the H \to J/\psi+gamma decay should be observable at a 14 TeV LHC.
We point out that quantum interference between two different production
mechanisms makes the decay rates sensitive to the HQQbar couplings.
Consequently, measurements of the H \to J/\psi+gamma decay rate would allow one
to probe the Higgs-charm coupling directly at the LHC. We discuss the
experimental prospects for the observation of these decays and for the direct
measurement of the Hccbar coupling.


title: Panphasia: a user guide

abstract:
  We make a very large realisation of a Gaussian white noise field, called
PANPHASIA, public by releasing software that computes this field. Panphasia is
designed specifically for setting up Gaussian initial conditions for
cosmological simulations and resimulations of structure formation. We make
available both software to compute the field itself and codes to illustrate
applications including a modified version of a public serial initial conditions
generator. We document the software and present the results of a few basic
tests of the field. The properties and method of construction of Panphasia are
described in full in a companion paper Jenkins 2013.


title: Detection-Loophole-Free Test of Quantum Nonlocality, and Applications

abstract:
  We present a source of entangled photons that violates a Bell inequality free
of the "fair-sampling" assumption, by over 7 standard deviations. This
violation is the first experiment with photons to close the detection loophole,
and we demonstrate enough "efficiency" overhead to eventually perform a fully
loophole-free test of local realism. The entanglement quality is verified by
maximally violating additional Bell tests, testing the upper limit of quantum
correlations. Finally, we use the source to generate secure private quantum
random numbers at rates over 4 orders of magnitude beyond previous experiments.


title: Displaced vertices in GMSB models at LHC

abstract:
  We consider minimal Gauge Mediated Supersymmetry Breaking models at which the
next to lightest supersymmetric particle is a neutralino with a large enough
decay length to be detected at the CERN Large Hadron Collider. We analyze the
potential of the LHCb experiment to determine the discovery reach for such
models and found that the LHCb will be able to probe such models up to the
energy breaking scale of \Lambda = 130 TeV.


title:
Generalized energy and time-translation invariance in a driven,
  dissipative system

abstract:
  Driven condensed matter systems consistently pose substantial challenges to
theoretical understanding. Progress in the study of such systems has been
achieved using the Floquet formalism, but certain aspects of this approach are
not well understood. In this paper, we consider the exceptionally simple case
of the rotating Kekul\'e mass in graphene through the lens of Floquet theory.
We show that the fact that this problem is gauge-equivalent to a
time-independent problem implies that the "quasi-energies" of Floquet theory
correspond to a continuous symmetry of the full time-dependent Lagrangian. We
use the conserved Noether charge associated with this symmetry to recover
notions of equilibrium statistical mechanics.


title: Spinon confinement: dynamics of weakly coupled Hubbard chains

abstract:
  Using large-scale determinant quantum Monte Carlo simulations in combination
with the stochastic analytical continuation, we study two-particle dynamical
correlation functions in the anisotropic square lattice of weakly coupled
one-dimensional (1D) Hubbard chains at half-filling and in the presence of weak
frustration. The evolution of the static spin structure factor upon increasing
the interchain coupling is suggestive of the transition from the power-law
decay of spin-spin correlations in the 1D limit to long-range antiferromagnetic
order in the quasi-1D regime and at $T=0$. In the numerically accessible regime
of interchain couplings, the charge sector remains gapped. The low-energy
momentum dependence of the spin excitations is well described by the linear
spin-wave theory with the largest intensity located around the
antiferromagnetic wave vector. This magnon mode corresponds to a bound state of
two spinons. At higher energies the spinons deconfine and we observe signatures
of the two-spinon continuum which progressively fade away as a function of
interchain hopping.


title: Two-Part Reconstruction in Compressed Sensing

abstract:
  Two-part reconstruction is a framework for signal recovery in compressed
sensing (CS), in which the advantages of two different algorithms are combined.
Our framework allows to accelerate the reconstruction procedure without
compromising the reconstruction quality. To illustrate the efficacy of our
two-part approach, we extend the author's previous Sudocodes algorithm and make
it robust to measurement noise. In a 1-bit CS setting, promising numerical
results indicate that our algorithm offers both a reduction in run-time and
improvement in reconstruction quality.


title: Chaos at Fifty

abstract:
  In 1963 Edward Lorenz revealed deterministic predictability to be an illusion
and gave birth to a field that still thrives. This Feature Article discusses
Lorenz's discovery and developments that followed from it.

categories: nlin.CD cond-mat.dis-nn math.DS physics.class-ph


title:
Many-body effects on the electronic and optical properties of strained
  semiconducting carbon nanotubes

abstract:
  We present many-body \textit{ab initio} calculations of the electronic and
optical properties of semiconducting zigzag carbon nanotubes under uniaxial
strain. The GW approach is utilized to obtain the quasiparticle bandgaps and is
combined with the Bethe-Salpeter equation to obtain the optical absorption
spectrum. We find that the dependence of the electronic bandgaps on strain is
more complex than previously predicted based on tight-binding models or
density-functional theory. In addition, we show that the exciton energy and
exciton binding energy depend significantly on strain, with variations of tens
of meVs per percent strain, but that despite these strong changes the
absorbance is found to be nearly independent of strain. Our results provide new
guidance for the understanding and design of optomechanical systems based on
carbon nanotubes.


title: k-nets embedded in a projective plane over a field

abstract:
  We investigate $k$-nets with $k\geq 4$ embedded in the projective plane
$PG(2,\mathbb{K})$ defined over a field $\mathbb{K}$; they are line
configurations in $PG(2,\mathbb{K})$ consisting of $k$ pairwise disjoint
line-sets, called components, such that any two lines from distinct families
are concurrent with exactly one line from each component. The size of each
component of a $k$-net is the same, the order of the $k$-net. If $\mathbb{K}$
has zero characteristic, no embedded $k$-net for $k\geq 5$ exists; see [1,2].
Here we prove that this holds true in positive characteristic $p$ as long as
$p$ is sufficiently large compared with the order of the $k$-net. Our approach,
different from that used in [1,2], also provides a new proof in characteristic
zero.
  [1] J. Stipins, Old and new examples of k-nets in P2, math.AG/0701046.
  [2] S. Yuzvinsky, A new bound on the number of special fibers in a pencil of
curves, Proc. Amer. Math. Soc. 137 (2009), 1641-1648.


title:
Observing Extended Sources with the \Herschel SPIRE Fourier Transform
  Spectrometer

abstract:
  The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space
Agency's Herschel Space Observatory utilizes a pioneering design for its
imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The
standard FTS data reduction and calibration schemes are aimed at objects with
either a spatial extent much larger than the beam size or a source that can be
approximated as a point source within the beam. However, when sources are of
intermediate spatial extent, neither of these calibrations schemes is
appropriate and both the spatial response of the instrument and the source's
light profile must be taken into account and the coupling between them
explicitly derived. To that end, we derive the necessary corrections using an
observed spectrum of a fully extended source with the beam profile and the
source's light profile taken into account. We apply the derived correction to
several observations of planets and compare the corrected spectra with their
spectral models to study the beam coupling efficiency of the instrument in the
case of partially extended sources. We find that we can apply these correction
factors for sources with angular sizes up to \theta_{D} ~ 17". We demonstrate
how the angular size of an extended source can be estimated using the
difference between the sub-spectra observed at the overlap bandwidth of the two
frequency channels in the spectrometer, at 959<\nu<989 GHz. Using this
technique on an observation of Saturn, we estimate a size of 17.2", which is 3%
larger than its true size on the day of observation. Finally, we show the
results of the correction applied on observations of a nearby galaxy, M82, and
the compact core of a Galactic molecular cloud, Sgr B2.


title:
Comparison of the Achievable Rates in OFDM and Single Carrier Modulation
  with I.I.D. Inputs

abstract:
  We compare the maximum achievable rates in single-carrier and OFDM modulation
schemes, under the practical assumptions of i.i.d. finite alphabet inputs and
linear ISI with additive Gaussian noise. We show that the Shamai-Laroia
approximation serves as a bridge between the two rates: while it is well known
that this approximation is often a lower bound on the single-carrier achievable
rate, it is revealed to also essentially upper bound the OFDM achievable rate.
We apply Information-Estimation relations in order to rigorously establish this
result for both general input distributions and to sharpen it for commonly used
PAM and QAM constellations. To this end, novel bounds on MMSE estimation of PAM
inputs to a scalar Gaussian channel are derived, which may be of general
interest. Our results show that, under reasonable assumptions, optimal
single-carrier schemes may offer spectral efficiency significantly superior to
that of OFDM, motivating further research of such systems.


title:
A Tool for Programming Embarrassingly Task Parallel Applications on CoW
  and NoW

abstract:
  Embarrassingly parallel problems can be split in parts that are characterized
by a really low (or sometime absent) exchange of information during their
computation in parallel. As a consequence they can be effectively computed in
parallel exploiting commodity hardware, hence without particularly
sophisticated interconnection networks. Basically, this means Clusters,
Networks of Workstations and Desktops as well as Computational Clouds. Despite
the simplicity of this computational model, it can be exploited to compute a
quite large range of problems. This paper describes JJPF, a tool for developing
task parallel applications based on Java and Jini that showed to be an
effective and efficient solution in environment like Clusters and Networks of
Workstations and Desktops.


title:
Orientation of the Angular Momentum in Superfluid 3He-A in a Stretched
  Aerogel

abstract:
  Superfluid 3He-A in a fully characterized stretched aerogel, used in previous
work [1], has been studied for parallel and perpendicular orientations of the
magnetic field relative to the anisotropy axis of the aerogel. Consistently, we
find that an equal spin pairing state (ESP) is stabilized down to the lowest
temperature. From our pulsed NMR frequency shifts as a function of temperature
and tip angle, the orientation of the orbital angular momentum l has been
determined. The aerogel anisotropy introduced by uniaxial stretching tends to
align l in the axial state parallel to the strain axis, confirming the theory
proposed by Sauls [2] and contrary to the prediction of Volovik [3] based on an
impurity calculation of Rainer and Vuorio [4].


title:
The Monopole and the Coulomb field as duals within the unifying
  Reissner-Nordstrom geometry

abstract:
  We are going to prove that the Monopole and the Coulomb fields are duals
within the unifying structure provided by the Reissner-Nordstrom spacetime.
This is accomplished when noticing that in order to produce the tetrad that
locally and covariantly diagonalizes the stress-energy tensor, both the
Monopole and the Coulomb fields are necessary in the construction. Without any
of them it would be impossible to express the tetrad vectors that locally and
covariantly diagonalize the stress-energy tensor. Then, both electromagnetic
fields are an integral part of the same structure, the Reissner-Nordstrom
geometry.


title: BCS-BEC Crossover and the Unitary Fermi Gas

abstract:
  The crossover from weak coupling Bardeen-Cooper-Schrieffer (BCS) pairing to a
Bose-Einstein condensate (BEC) of tightly bound pairs, as a function of the
attractive interaction in Fermi systems, has long been of interest to
theoretical physicists. The past decade has seen a series of remarkable
experimental developments in ultracold Fermi gases that has realized the
BCS-BEC crossover in the laboratory, bringing with it fresh new insights into
the very strongly interacting unitary regime in the middle of this crossover.
In this review, we start with a pedagogical introduction to the crossover and
then focus on recent progress in the strongly interacting regime. While our
focus is on new theoretical developments, we also describe three key
experiments that probe the thermodynamics, transport and spectroscopy of the
unitary Fermi gas. We discuss connections between the unitary regime and other
areas of physics -- quark-gluon plasmas, gauge-gravity duality and high
temperature superconductivity -- and conclude with open questions about
strongly interacting Fermi gases.


title: Testing for nodal dependence in relational data matrices

abstract:
  Relational data are often represented as a square matrix, the entries of
which record the relationships between pairs of objects. Many statistical
methods for the analysis of such data assume some degree of similarity or
dependence between objects in terms of the way they relate to each other.
However, formal tests for such dependence have not been developed. We provide a
test for such dependence using the framework of the matrix normal model, a type
of multivariate normal distribution parameterized in terms of row- and
column-specific covariance matrices. We develop a likelihood ratio test (LRT)
for row and column dependence based on the observation of a single relational
data matrix. We obtain a reference distribution for the LRT statistic, thereby
providing an exact test for the presence of row or column correlations in a
square relational data matrix. Additionally, we provide extensions of the test
to accommodate common features of such data, such as undefined diagonal
entries, a non-zero mean, multiple observations, and deviations from normality.


title: Spread Spectrum Codes for Continuous-Phase Modulated Systems

abstract:
  We study the theoretical performance of a combined approach to demodulation
and decoding of binary continuous-phase modulated signals under repetition-like
codes. This technique is motivated by a need to transmit packetized or framed
data bursts in high noise regimes where many powerful, short-length codes are
ineffective. In channels with strong noise, we mathematically study the
asymptotic bit error rates of this combined approach and quantify the
performance improvement over performing demodulation and decoding separately as
the code rate increases. In this context, we also discuss a simple variant of
repetition coding involving pseudorandom code words, based on direct-sequence
spread spectrum methods, that preserves the spectral density of the encoded
signal in order to maintain resistance to narrowband interference. We describe
numerical simulations that demonstrate the advantages of this approach as an
inner code which can be used underneath modern coding schemes in high noise
environments.


title:
Properties of Diffuse Interstellar Bands at Different Physical
  Conditions of the ISM

abstract:
  Diffuse interstellar bands (DIBs) can trace different conditions of the ISM
along the sightline toward the observed stars. A small survey was made in
optical wavelengths, producing high resolution and high signal to noise
spectra. We present measurements of 19 DIBs' properties in 50 sightlines
towards hot stars, distributed at a variety of galactic coordinates and
interstellar reddening. Equivalent widths were obtained by fitting asymmetric
Gaussian and variable continuum to DIBs. Conditions of the ISM were calculated
from 8 atomic and molecular interstellar lines. Two distinctively different
types of DIBs were identified, by carefully comparing correlation coefficients
between DIBs and reddening and by different behaviour in UV shielded ($\zeta$)
and non-shielded ($\sigma$) sightlines. A ratio of DIBs at 5780 \AA\ and~5797
\AA\ proved to be reliable enough to distinguish between two different
sightline types. Based on linear relations between DIB equivalent width and
reddening for $\sigma$ and $\zeta$ sightlines, we divide DIBs into type {\sc i}
(where both linear relations are similar) and type {\sc ii} (where they are
significantly different). Linear relation for $\zeta$ type sightlines always
show a higher slope and larger x-intercept parameter than the relation for
$\sigma$ sightlines. Scatter around the linear relation is reduced after the
separation, but it does not vanish completely. This means that UV shielding is
the dominant factor of the DIB equivalent width vs.\ reddening relation shape
for $\zeta$ sightlines, but in $\sigma$ sightlines other physical parameters
play a major role. No similar dependency on gas density, electron density or
turbulence was observed. A catalog of all observed interstellar lines is made
public.


title: Three-Dimensional Reconstruction of Erythrocyte in the Capillary

abstract:
  The dynamic analysis of erythrocyte deformability is used as an important
means for early diagnosis of blood diseases and blood rheology. Yet no
effective method is available in terms of three-dimensional reconstruction of
erythrocytes in a capillary. In this study, ultrathin serial sections of
skeletal muscle tissue are obtained from the ultramicrotome, the tomographic
images of an erythrocyte in a capillary are captured by the transmission
electron microscope, and then a method to position and restore is devised to
demonstrate the physiological relationship between two adjacent tomographic
images of an erythrocyte. Both the modeling and the physical verification
reveal that this method is effective, which means that it can be used to make
three-dimensional reconstruction of an erythrocyte in a capillary. An example
of reconstructed deformation of erythrocyte based on the serial ultrathin
sections is shown at the end of this paper.


title:
Coherent quantum transport in disordered systems I: The influence of
  dephasing on the transport properties and absorption spectra on
  one-dimensional systems

abstract:
  Excitonic transport in static disordered one dimensional systems is studied
in the presence of thermal fluctuations that are described by the
Haken-Strobl-Reineker model. For short times, non-diffusive behavior is
observed that can be characterized as the free-particle dynamics in the
Anderson localized system. Over longer time scales, the environment-induced
dephasing is sufficient to overcome the Anderson localization caused by the
disorder and allow for transport to occur which is always seen to be diffusive.
In the limiting regimes of weak and strong dephasing quantum master equations
are developed, and their respective scaling relations imply the existence of a
maximum in the diffusion constant as a function of the dephasing rate that is
confirmed numerically. In the weak dephasing regime, it is demonstrated that
the diffusion constant is proportional to the square of the localization length
which leads to a significant enhancement of the transport rate over the
classical prediction. Finally, the influence of noise and disorder on the
absorption spectrum is presented and its relationship to the transport
properties is discussed.


title: Large data local well-posedness for a class of KdV-type equations II

abstract:
  We consider the Cauchy problem for an equation of the form
\partial_t+\partial_x^3)u=F(u,u_x,u_{xx}) where F is a polynomial with no
constant or linear terms and no quadratic uu_{xx} term. For a polynomial
nonlinearity with no quadratic terms, Kenig-Ponce-Vega proved local
well-posedness in H^s for large s. In this paper we prove local well-posedness
in low regularity Sobolev spaces and extend the result to certain quadratic
nonlinearities. The result is based on spaces and estimates similar to those
used by Marzuola-Metcalfe-Tataru for quasilinear Schrodinger equations.


title: Momentum relaxation in holographic massive gravity

abstract:
  We study the effects of momentum relaxation on observables in a recently
proposed holographic model in which the conservation of momentum in the field
theory is broken by the presence of a bulk graviton mass. In the hydrodynamic
limit, we show that these effects can be incorporated by a simple modification
of the energy-momentum conservation equation to account for the dissipation of
momentum over a single characteristic timescale. We compute this timescale as a
function of the graviton mass terms and identify the previously known "wall of
stability" as the point at which this relaxation timescale becomes negative. We
also calculate analytically the zero temperature AC conductivity at low
frequencies. In the limit of a small graviton mass this reduces to the simple
Drude form, and we compute the corrections to this which are important for
larger masses. Finally, we undertake a preliminary investigation of the
stability of the zero temperature black brane solution of this model, and rule
out spatially modulated instabilities of a certain kind.


title:
A State-Space Approach for Optimal Traffic Monitoring via Network Flow
  Sampling

abstract:
  The robustness and integrity of IP networks require efficient tools for
traffic monitoring and analysis, which scale well with traffic volume and
network size. We address the problem of optimal large-scale flow monitoring of
computer networks under resource constraints. We propose a stochastic
optimization framework where traffic measurements are done by exploiting the
spatial (across network links) and temporal relationship of traffic flows.
Specifically, given the network topology, the state-space characterization of
network flows and sampling constraints at each monitoring station, we seek an
optimal packet sampling strategy that yields the best traffic volume estimation
for all flows of the network. The optimal sampling design is the result of a
concave minimization problem; then, Kalman filtering is employed to yield a
sequence of traffic estimates for each network flow. We evaluate our algorithm
using real-world Internet2 data.


title:
Algorithm independent bounds on community detection problems and
  associated transitions in stochastic block model graphs

abstract:
  We derive rigorous bounds for well-defined community structure in complex
networks for a stochastic block model (SBM) benchmark. In particular, we
analyze the effect of inter-community "noise" (inter-community edges) on any
"community detection" algorithm's ability to correctly group nodes assigned to
a planted partition, a problem which has been proven to be NP complete in a
standard rendition. Our result does not rely on the use of any one particular
algorithm nor on the analysis of the limitations of inference. Rather, we turn
the problem on its head and work backwards to examine when, in the first place,
well defined structure may exist in SBMs.The method that we introduce here
could potentially be applied to other computational problems. The objective of
community detection algorithms is to partition a given network into optimally
disjoint subgraphs (or communities). Similar to k-SAT and other combinatorial
optimization problems, "community detection" exhibits different phases.
Networks that lie in the "unsolvable phase" lack well-defined structure and
thus have no partition that is meaningful. Solvable systems splinter into two
disparate phases: those in the "hard" phase and those in the "easy" phase. As
befits its name, within the easy phase, a partition is easy to achieve by known
algorithms. When a network lies in the hard phase, it still has an underlying
structure yet finding a meaningful partition which can be checked in polynomial
time requires an exhaustive computational effort that rapidly increases with
the size of the graph. When taken together, (i) the rigorous results that we
report here on when graphs have an underlying structure and (ii) recent results
concerning the limits of rather general algorithms, suggest bounds on the hard
phase.


title:
Multi-wavelength Hubble Space Telescope photometry of stellar
  populations in NGC288

abstract:
  We present new UV observations for NGC288, taken with the WFC3 detector on
board the Hubble Space Telescope, and combine them with existing optical data
from the archive to explore the multiple-population phenomenon in this globular
cluster (GC). The WFC3's UV filters have demonstrated an uncanny ability to
distinguish multiple populations along all photometric sequences in GCs, thanks
to their exquisite sensitivity to the atmospheric changes that are tell-tale
signs of second-generation enrichment. Optical filters, on the other hand, are
more sensitive to stellar-structure changes related to helium enhancement. By
combining both UV and optical data we can measure helium variation. We quantify
this enhancement for NGC288 and find that its variation is typical of what we
have come to expect in other clusters.


title:
Algorithms for distance problems in planar complexes of global
  nonpositive curvature

abstract:
  CAT(0) metric spaces and hyperbolic spaces play an important role in
combinatorial and geometric group theory. In this paper, we present efficient
algorithms for distance problems in CAT(0) planar complexes. First of all, we
present an algorithm for answering single-point distance queries in a CAT(0)
planar complex. Namely, we show that for a CAT(0) planar complex K with n
vertices, one can construct in O(n^2 log n) time a data structure D of size
O(n^2) so that, given a point x in K, the shortest path gamma(x,y) between x
and the query point y can be computed in linear time. Our second algorithm
computes the convex hull of a finite set of points in a CAT(0) planar complex.
This algorithm is based on Toussaint's algorithm for computing the convex hull
of a finite set of points in a simple polygon and it constructs the convex hull
of a set of k points in O(n^2 log n + nk log k) time, using a data structure of
size O(n^2 + k).


title:
Optimized Parallel Transmission in Elastic Optical Networks to Support
  High-Speed Ethernet

abstract:
  The need for optical parallelization is driven by the imminent optical
capacity crunch, where the spectral efficiency required in the coming decades
will be beyond the Shannon limit. To this end, the emerging high-speed Ethernet
services at 100 Gbps, have already standardized options to utilize parallel
optics to parallelize interfaces referred to as Multi-lane Distribution (MLD).
OFDM-based optical network is a promising transmission option towards the goal
of Ethernet parallelization. It can allocate optical resource tailored for a
variety of bandwidth requirements and that in a fundamentally parallel fashion
with each sub-carrier utilizing a frequency slot at a lower rate than if serial
transmission was used. In this paper, we propose a novel parallel transmission
framework designed for elastic (OFDM-based) optical networks to support
high-speed Ethernet services, in-line with IEEE and ITU-T standards. We
formulate an ILP optimization model based on integer linear programming, with
consideration of various constraints, including spectrum fragmentation,
differential delay and guard-band constraints. We also propose a heuristic
algorithm which can be applied when the optimization model becomes intractable.
The numerical results show the effectiveness and high suitability of elastic
optical networks to support parallel transmission in high-speed Ethernet. To
the best of our knowledge, this is the first attempt to investigate the
parallel transmission in elastic optical networks to support standardized
high-speed Ethernet.


title: Clues on void evolution I: Large scale galaxy distributions around voids

abstract:
  We perform a statistical study focused on void environments. We examine
galaxy density profiles around voids in the SDSS, finding a correlation between
void--centric distance to the shell of maximum density and void radius when a
maximum in overdensity exists. We analyze voids with and without a surrounding
over-dense shell in the SDSS. We find that small voids are more frequently
surrounded by over-dense shells whereas the radial galaxy density profile of
large voids tends to rise smoothly towards the mean galaxy density. We analyse
the fraction of voids surrounded by overdense shells finding a continuous trend
with void radius. The differences between voids with and without an overdense
shell around them can be understood in terms of whether the voids are, on
average, in the process of collapsing or continuing their expansion,
respectively, in agreement with previous theoretical expectations. We use
numerical simulations coupled to semi-analytic models of galaxy formation in
order to test and interpret our results. The very good agreement between the
mock catalog results and the observations provides additional support to the
viability of a LCDM model to reproduce the large scale structure of the
universe as defined by the void network, in a way which has not been analysed
previously.


title:
Clues on void evolution II: Measuring density and velocity profiles on
  SDSS galaxy redshift space distortions

abstract:
  Using the redshift-space distortions of void-galaxy cross-correlation
function we analyse the dynamics of voids embedded in different environments.
We compute the void-galaxy cross-correlation function in the Sloan Digital Sky
Survey (SDSS) in terms of distances taken along the line of sight and projected
into the sky. We analyse the distortions on the cross-correlation isodensity
levels and we find anisotropic isocontours consistent with expansion for large
voids with smoothly rising density profiles and collapse for small voids with
overdense shells surrounding them. Based on the linear approach of
gravitational collapse theory we developed a parametric model of the
void-galaxy redshift space cross-correlation function. We show that this model
can be used to successfully recover the underlying velocity and density
profiles of voids from redshift space samples. By applying this technique to
real data, we confirm the twofold nature of void dynamics: large voids
typically are in an expansion phase whereas small voids tend to be surrounded
by overdense and collapsing regions. These results are obtained from the SDSS
spectroscopic galaxy catalogue and also from semi-analytic mock galaxy
catalogues, thus supporting the viability of the standard LCDM model to
reproduce large scale structure and dynamics.


title:
Sensitivity of the High Altitude Water Cherenkov Detector to Sources of
  Multi-TeV Gamma Rays

abstract:
  The High Altitude Water Cherenkov (HAWC) observatory is an array of large
water Cherenkov detectors sensitive to gamma rays and hadronic cosmic rays in
the energy band between 100 GeV and 100 TeV. The observatory will be used to
measure high-energy protons and cosmic rays via detection of the energetic
secondary particles reaching the ground when one of these particles interacts
in the atmosphere above the detector. HAWC is under construction at a site 4100
meters above sea level on the northern slope of the volcano Sierra Negra, which
is located in central Mexico at 19 degrees N latitude. It is scheduled for
completion in 2014. In this paper we estimate the sensitivity of the HAWC
instrument to point-like and extended sources of gamma rays. The source fluxes
are modeled using both unbroken power laws and power laws with exponential
cutoffs. HAWC, in one year, is sensitive to point sources with integral
power-law spectra as low as 5x10^-13 cm^-2 sec^-1 above 2 TeV (approximately 50
mCrab) over 5 sr of the sky. This is a conservative estimate based on simple
event parameters and is expected to improve as the data analysis techniques are
refined. We discuss known TeV sources and the scientific contributions that
HAWC can make to our understanding of particle acceleration in these sources.


title: Two-photon interference between disparate sources for quantum networking

abstract:
  Quantum networks involve entanglement sharing between multiple users.
Ideally, any two users would be able to connect regardless of the type of
photon source they employ, provided they fulfill the requirements for
two-photon interference. From a theoretical perspective, photons coming from
different origins can interfere with a perfect visibility, provided they are
made indistinguishable in all degrees of freedom. Previous experimental
demonstrations of such a scenario have been limited to photon wavelengths below
900 nm, unsuitable for long distance communication, and suffered from low
interference visibility. We report two-photon interference using two disparate
heralded single photon sources, which involve different nonlinear effects,
operating in the telecom wavelength range. The measured visibility of the
two-photon interference is 80+/-4%, which paves the way to hybrid universal
quantum networks.


title: The Carnegie Hubble Program: The Infrared Leavitt Law in IC 1613

abstract:
  We have observed the dwarf galaxy IC 1613, at multiple epochs in the
mid--infrared using Spitzer and contemporaneously in the near--infrared using
the new FourStar near-IR camera on Magellan. We have constructed Cepheid
period--luminosity relations in the J, H, K_s, [3.6] and [4.5] bands and have
used the run of their apparent distance moduli as a function of wavelength to
derive the line--of--sight reddening and distance to IC1613. Using a nine--band
fit, we find E(B-V) = 0.05 +- 0.01 mag and an extinction--corrected distance
modulus of mu_{0} = 24.29 +- 0.03_{statistical} +- 0.03_{systematic} mag. By
comparing our multi--band and [3.6] distance moduli to results from the tip of
the red giant branch and red clump distance indicators, we find that
metallicity has no measurable effect on Cepheid distances at 3.6 microns in the
metallicity range -1.0 < [Fe/H] < 0.2, hence derivations of the Hubble constant
at this wavelength require no correction for metallicity.


title:
Feynman's Path Integral to Ostrogradsky's Hamiltonian for Lagrangians
  with second derivatives

abstract:
  A calculation is presented that shows that Feynman's path integral implies
Ostrogradsky's Hamiltonian for nonsingular Lagrangians with second derivatives.
The procedure employs the stationary phase approximation to obtain the limiting
change of the wave function per unit time. By way of introduction, the method
is applied anew to the case of nonsingular Lagrangians with only first
derivatives, but not necessarily quadratic in the velocities. A byproduct of
the calculation is an alternate derivation of the Legendre transformation of
taking general classical Lagrangians into Hamiltonians. In both the first and
second derivative cases, the outcome contains precisely the classical
Hamiltonian, which represents the so-called "symbol" of a (not necessarily
Hermitean) pseudodifferential operator acting on the wave function at an
instant of time. The derivation herein argues for a claim that Feynman's method
starts with a classical Lagrangian and ends with a classical
Hamiltonian---nonclassical operator-ordering prescriptions in the passage from
classical to quantum Hamiltonians require external input, and are generally not
inherent in Feynman's path integral formalism.


title:
Fluctuations and correlations of hot QCD matter in an external magnetic
  field

abstract:
  Effects of an external magnetic field on the fluctuations of quark number,
fluctuations and correlations of conserved charges, including baryon number,
electric charge and strangeness, are studied in the 2+1 flavor
Polyakov--Nambu--Jona-Lasinio model. We find that magnetic field increases
fluctuations and correlations in the regime of chiral crossover. It makes the
transition of quadratic fluctuations more abrupt, and the peak structure of
quartic fluctuations more pronounced. Our calculations indicate that
$\chi_{4}^{B}/\chi_{2}^{B}$, $\chi_{4}^{Q}/\chi_{2}^{Q}$, and $\chi_{11}^{BQ}$
are very sensitive to the external magnetic field and maybe can be used for
probes for the strong magnetic field produced in the early stage of noncentral
collisions.


title: No-go theorem for the composition of quantum systems

abstract:
  Building on the Pusey-Barrett-Rudolph theorem, we derive a no-go theorem for
a vast class of deterministic hidden-variables theories, including those
consistent on their targeted domain. The strength of this result throws doubt
on seemingly natural assumptions (like the "preparation independence" of the
Pusey-Barrett-Rudolph theorem) about how "real states" of subsystems compose
for joint systems in nonentangled states. This points to constraints in
modeling tensor-product states, similar to constraints demonstrated for more
complex states by the Bell and Bell-Kochen-Specker theorems.


title:
Omnibus CLTs for Fr\'echet means and nonparametric inference on
  non-Euclidean spaces

abstract:
  Two central limit theorems for sample Fr\'echet means are derived, both
significant for nonparametric inference on non-Euclidean spaces. The first one,
Theorem 2.2, encompasses and improves upon most earlier CLTs on Fr\'echet means
and broadens the scope of the methodology beyond manifolds to diverse new
non-Euclidean data including those on certain stratified spaces which are
important in the study of phylogenetic trees. It does not require that the
underlying distribution $Q$ have a density, and applies to both intrinsic and
extrinsic analysis. The second theorem, Theorem 3.3, focuses on intrinsic means
on Riemannian manifolds of dimensions $d>2$ and breaks new ground by providing
a broad CLT without any of the earlier restrictive support assumptions. It
makes the statistically reasonable assumption of a somewhat smooth density of
$Q$. The excluded case of dimension $d=2$ proves to be an enigma, although the
first theorem does provide a CLT in this case as well under a support
restriction. Theorem 3.3 immediately applies to spheres $S^d$, $d>2$, which are
also of considerable importance in applications to axial spaces and to
landmarks based image analysis, as these spaces are quotients of spheres under
a Lie group $\mathcal G $ of isometries of $S^d$.


title: Radon-Nikod\'ym property and thick families of geodesics

abstract:
  Banach spaces without the Radon-Nikod\'ym property are characterized as
spaces containing bilipschitz images of thick families of geodesics defined as
follows. A family $T$ of geodesics joining points $u$ and $v$ in a metric space
is called {\it thick} if there is $\alpha>0$ such that for every $g\in T$ and
for any finite collection of points $r_1,...,r_n$ in the image of $g$, there is
another $uv$-geodesic $\widetilde g\in T$ satisfying the conditions:
$\widetilde g$ also passes through $r_1,...,r_n$, and, possibly, has some more
common points with $g$. On the other hand, there is a finite collection of
common points of $g$ and $\widetilde g$ which contains $r_1,...,r_n$ and is
such that the sum of maximal deviations of the geodesics between these common
points is at least $\alpha$.


title:
Search for correlations of the arrival directions of ultra-high energy
  cosmic ray with extragalactic objects as observed by the telescope array
  experiment

abstract:
  We search for correlations between positions of extragalactic objects and
arrival directions of Ultra-High Energy Cosmic Rays (UHECRs) with primary
energy $E \ge 40$ EeV as observed by the surface detector array of the
Telescope Array (TA) experiment during the first 40 months of operation. We
examined several public astronomical object catalogs, including the Veron-Cetty
and Veron catalog of active galactic nuclei. We counted the number of TA events
correlated with objects in each catalog as a function of three parameters: the
maximum angular separation between a TA event and an object, the minimum energy
of the events, and the maximum redshift of the objects. We determine
combinations of these parameters which maximize the correlations, and calculate
the chance probabilities of having the same levels of correlations from an
isotropic distribution of UHECR arrival directions. No statistically
significant correlations are found when penalties for scanning over the above
parameters and for searching in several catalogs are taken into account.


title:
Weight distributions of cyclic codes with respect to pairwise coprime
  order elements

abstract:
  Let $\Bbb F_r$ be an extension of a finite field $\Bbb F_q$ with $r=q^m$. Let
each $g_i$ be of order $n_i$ in $\Bbb F_r^*$ and $\gcd(n_i, n_j)=1$ for $1\leq
i \neq j \leq u$.
  We define a cyclic code over $\Bbb F_q$ by
  $$\mathcal C_{(q, m, n_1,n_2, ..., n_u)}=\{c(a_1, a_2, ..., a_u) : a_1, a_2,
..., a_u \in \Bbb F_r\},$$ where
  $$c(a_1, a_2, ..., a_u)=({Tr}_{r/q}(\sum_{i=1}^ua_ig_i^0), ...,
{Tr}_{r/q}(\sum_{i=1}^ua_ig_i^{n-1}))$$ and $n=n_1n_2... n_u$. In this paper,
we present a method to compute the weights of $\mathcal C_{(q, m, n_1,n_2, ...,
n_u)}$. Further, we determine the weight distributions of the cyclic codes
$\mathcal C_{(q, m, n_1,n_2)}$ and $\mathcal C_{(q, m, n_1,n_2,1)}$.


title: Polar optical phonons in core-shell semiconductor nanowires

abstract:
  We obtain the the long-wavelength polar optical vibrational modes of
semiconductor core-shell nanowires by means of a phenomenological continuum
model. A basis for the space of solutions is derived, and by applying the
appropriate boundary conditions, the transcendental equations for the coupled
and uncoupled modes are attained. Our results are applied to the study of the
GaAs-GaP core-shell nanowire, for which we calculate numerically the polar
optical modes, analyzing the role of strain in the vibrational properties of
this nanosystem.


title:
Dwork's congruences for the constant terms of powers of a Laurent
  polynomial

abstract:
  We prove that the constant terms of powers of a Laurent polynomial satisfy
certain congruences modulo prime powers. As a corollary, the generating series
of these numbers considered as a function of a p-adic variable satisfies a
non-trivial analytic continuation property, similar to what B. Dwork showed for
a class of hypergeometric series.


title: Quantum Cosmology will need to become a Numerical Subject

abstract:
  The inhomogeneous fluctuations that underlie structure formation - galaxies
and CMB hotspots - might have been seeded by quantum cosmological fluctuations,
as magnified by some inflationary mechanism. The Halliwell-Hawking model for
these, as a lower-energy semiclassical limit, is expected to be shared by many
theories. E.g. an O((H/m_pl)^2) suppression of power at large scales results
from this. This model contains/suppresses very many terms; we want a
qualitative understanding of the meaning of these terms and of different
regimes resulting from different combinations of them. I study this with toy
models that have tractable mathematics: minisuperspace and, especially,
relational particle mechanics. In the present Seminar, I consider in particular
averaged terms with some lessons from Hartree-Fock approach to Atomic and
Molecular Physics. One needs to anchor this on variational principles; treating
the subsequent equations is a numerical venture.


title: Mechanical memory for photons with orbital angular momentum

abstract:
  We propose to use an acoustic surface wave as a memory for a photon carrying
orbital angular momentum. We clarify the physical mechanism that enables the
transfer of information, derive the angular momentum selection rule that must
be obeyed in the process, and show how to optimize the optoacoustic coupling.
We theoretically demonstrate that high fidelities can be achieved, using
realistic parameters, for the transfer of a coherent optical Laguerre-Gaussian
state, associated with large angular momentum, to a mechanical shear mode. Our
results add a significant possibility to the ongoing efforts towards the
implementation of quantum information processing using photonic orbital angular
momentum.


title:
Long distance measurement-device-independent quantum key distribution
  with entangled photon sources

abstract:
  We present a practical method that can make quantum key distribution (QKD),
for the first time, both ultra-long-distance and immune to all attacks in the
detection system. This method is an important extension of the
measurement-device-independent QKD (MDI-QKD) - MDI-QKD with entangled photon
sources in the middle. By proposing a general model and simulating an
entanglement based QKD experiment, we find that MDI-QKD with one entangled
photon source in the middle can practically tolerate 77 dB combined loss (367km
standard telecom fiber) in the asymptotic limit, and it can still tolerate 60
dB combined loss (286km standard telecom fiber) in the finite-key case with
state-of-the-art detectors. Our general model can also be applied to other
non-QKD experiments involving entangled photon sources and Bell state
measurements.


title: Some Extensions of the All Pairs Bottleneck Paths Problem

abstract:
  We extend the well known bottleneck paths problem in two directions for
directed unweighted (unit edge cost) graphs with positive real edge capacities.
Firstly we narrow the problem domain and compute the bottleneck of the entire
network in $O(n^{\omega}\log{n})$ time, where $O(n^{\omega})$ is the time taken
to multiply two $n$-by-$n$ matrices over ring. Secondly we enlarge the domain
and compute the shortest paths for all possible flow amounts. We present a
combinatorial algorithm to solve the Single Source Shortest Paths for All Flows
(SSSP-AF) problem in $O(mn)$ worst case time, followed by an algorithm to solve
the All Pairs Shortest Paths for All Flows (APSP-AF) problem in
$O(\sqrt{d}n^{(\omega+9)/4})$ time, where $d$ is the number of distinct edge
capacities. We also discuss real life applications for these new problems.


title: Problem of Time: Facets and Machian Strategy

abstract:
  The Problem of Time is that `time' in each of ordinary quantum theory and
general relativity are mutually incompatible notions. This causes difficulties
in trying to put these two theories together to form a theory of Quantum
Gravity. The Problem of Time has 8 facets in canonical approaches. I clarify
that all but one of these facets already occur at the classical level, and
reconceptualize and re-name some of these facets as follows.The Frozen
Formalism Problem becomes Temporal Relationalism, the Thin Sandwich Problem
becomes Configurational Relationalism, via the notion of Best Matching. The
Problem of Observables becomes the Problem of Beables, and the Functional
Evolution Problem becomes the Constraint Closure Problem. I also outline how
each of the Global and Multiple-Choice Problems of Time have their own
plurality of facets.
  This article additionally contains a local resolution to the Problem of Time
at the conceptual level and which is actually realizable for the relational
triangle and minisuperspace models. This resolution is, moreover, Machian, and
has three levels: classical, semiclassical and a combined
semiclassical-histories-timeless records scheme. I end by delineating the
current frontiers of this program toward resolution of the Problem of Time in
the cases of full GR and of slightly inhomogeneous cosmology.


title:
Orbital-Selective Mottness in KxFe2-ySe2 Superconductors Revealed by
  Pump-Probe Spectroscopy

abstract:
  We report transient optical signatures of the orbital-selective Mottness in
superconducting KxFe2-ySe2 crystals by using dual-color pump-probe
spectroscopy. Besides multi-exponential decay recovery dynamics of
photo-induced quasiparticles, a damped oscillatory component due to coherent
acoustic phonons emerges when the superconducting phase is suppressed by
increasing the temperature or excitation power. The oscillatory component
diminishes with significant enhancement of a slow decay component upon raising
temperature to 150-160 K. These results are in consistence with the picture of
orbital-selective Mott phase transition, indicating a vital role played by
electron correlation in the iron-based superconductors.


title: Extended QCD

abstract:
  I consider a reformulation of QCD which incorporates additional bosonic
fields, and analyze it in the large-N limit. This construction makes a more
direct connection with the nonrelativistic quark and the chiral quark models,
as well as the bag model for baryons. This extension of QCD is neither a model
nor an effective low energy theory, but is exactly equivalent to QCD.


title: Superorbital Phase-Resolved Analysis of SMC X-1

abstract:
  The high-mass X-ray binary SMC X-1 is an eclipsing binary with an orbital
period of 3.89 d. This system exhibits a superorbital modulation with a period
varying between ~40 d and ~65 d. The instantaneous frequency and the
corresponding phase of the superorbital modulation can be obtained by a
recently developed time-frequency analysis technique, the Hilbert-Huang
transform (HHT). We present a phase-resolved analysis of both the spectra and
the orbital profiles with the superorbital phase derived from the HHT. The
X-ray spectra observed by the Proportional Counter Array onboard the Rossi
X-ray Timing Explorer are fitted well by a blackbody plus a Comptonized
component. The plasma optical depth, which is a good indicator of the
distribution of material along the line of sight, is significantly
anti-correlated with the flux detected at 2.5-25 keV. However, the relationship
between the plasma optical depth and the equivalent width of the iron line is
not monotonic: there is no significant correlation for fluxes higher than ~35
mCrab but clear positive correlation when the intensity is lower than ~20
mCrab. This indicates that the iron line production is dominated by different
regions of this binary system in different superorbital phases. To study the
dependence of the orbital profile on the superorbital phase, we obtained the
eclipse profiles by folding the All Sky Monitor light curve with the orbital
period for different superorbital states. A dip feature, similar to the
pre-eclipse dip in Her X-1, lying at orbital phase ~0.6-0.85, was discovered
during the superorbital transition state. This indicates that the accretion
disk has a bulge that absorbs considerable X-ray emission in the stream-disk
interaction region. The dip width is anti-correlated with the flux, and this
relation can be interpreted by the precessing tilted accretion disk scenario.


title:
Effective action and linear response of compact objects in Newtonian
  gravity

abstract:
  We apply an effective field theory method for the gravitational interaction
of compact stars, developed within the context of general relativity, to
Newtonian gravity. In this effective theory a compact object is represented by
a point particle possessing generic gravitational multipole moments. The time
evolution of the multipoles depends on excitations due to external fields. This
can formally be described by a response function of the multipoles to applied
fields. The poles of this response correspond to the normal oscillation modes
of the star. This gives rise to resonances between modes and tidal forces in
binary systems. The connection to the standard formalism for tidal interactions
and resonances in Newtonian gravity is worked out. Our approach can be applied
to more complicated situations. In particular, a generalization to general
relativity is possible.


title:
Spectroscopy, Manipulation and Trapping of Neutral Atoms, Molecules, and
  Other Particles using Optical Nanofibers: A Review

abstract:
  The use of tapered optical fibers, i.e., optical nanofibers, for spectroscopy
and the detection of small numbers of particles, such as neutral atoms or
molecules, has been gaining ground in recent years. In this review, we briefly
introduce the optical nanofiber, its fabrication and optical mode propagation
within. We discuss recent progress on the integration of optical nanofibers
into laser-cooled atom and vapor systems, paying particular attention to
spectroscopy, cold atom cloud characterization and optical trapping schemes.
Next, a natural extension on this work to molecules will be introduced.
Finally, we consider several alternatives to optical nanofibers that display
some advantages for particular applications.


title: Attractors, Equilibrium, Profit, Loss

abstract:
  Various formulations of counterfactual general equilibrium in economies --
systems of actors manipulating economic goods -- are logically and
mathematically analyzed. Evenly-rotating economies are systems whose evolution
is stable, steady, and form-preserving. Several of their qualities are
qualities of homeorhesis but they are not in homeostasis: because their
instantaneous state is not steady, or in other words, they are not stationary.
What is possibly stationary in whole economies is change over time of behavior
of their parts in a way that causes that net of relations of these parts which
results to be preserved over time. Necessary existence of actual disequilibrium
and impossibility of actual or ultimate equilibrium is demonstrated and
different types of equilibrium and disequilibrium are discussed.


title:
Investigation of a $^{85}$Rb Dark Magneto-Optical Trap using an Optical
  Nanofibre

abstract:
  We report here measurements on a dark magneto-optical trap (DMOT) of
$^{85}$Rb atoms using an optical nanofibre (ONF) with a waist of $\sim$~1
$\mu$m. The DMOT is created using a doughnut-shaped repump beam along with a
depump beam for efficient transfer of cold atoms from the bright hyperfine
ground state ($F=3$) into the dark hyperfine ground state ($F=2$). The
fluorescence from the cold $^{85}$Rb atoms of the DMOT is detected by coupling
it into the fibre-guided modes of the ONF. The measured fractional population
of cold atoms in the bright hyperfine ground state ($p$) is as low as
$\sim$0.04. The dependence of loading rate of DMOT on cooling laser intensity
is investigated and also compared with the loading rate of a bright-MOT (BMOT).
This work lays the foundation for the use of an ONF for probing of a small
number of atoms in an optically-dense cold atomic cloud.


title:
Constrained Optimization for a Subset of the Gaussian Parsimonious
  Clustering Models

abstract:
  The expectation-maximization (EM) algorithm is an iterative method for
finding maximum likelihood estimates when data are incomplete or are treated as
being incomplete. The EM algorithm and its variants are commonly used for
parameter estimation in applications of mixture models for clustering and
classification. This despite the fact that even the Gaussian mixture model
likelihood surface contains many local maxima and is singularity riddled.
Previous work has focused on circumventing this problem by constraining the
smallest eigenvalue of the component covariance matrices. In this paper, we
consider constraining the smallest eigenvalue, the largest eigenvalue, and both
the smallest and largest within the family setting. Specifically, a subset of
the GPCM family is considered for model-based clustering, where we use a
re-parameterized version of the famous eigenvalue decomposition of the
component covariance matrices. Our approach is illustrated using various
experiments with simulated and real data.


title: Fourier PCA and Robust Tensor Decomposition

abstract:
  Fourier PCA is Principal Component Analysis of a matrix obtained from higher
order derivatives of the logarithm of the Fourier transform of a
distribution.We make this method algorithmic by developing a tensor
decomposition method for a pair of tensors sharing the same vectors in rank-$1$
decompositions. Our main application is the first provably polynomial-time
algorithm for underdetermined ICA, i.e., learning an $n \times m$ matrix $A$
from observations $y=Ax$ where $x$ is drawn from an unknown product
distribution with arbitrary non-Gaussian components. The number of component
distributions $m$ can be arbitrarily higher than the dimension $n$ and the
columns of $A$ only need to satisfy a natural and efficiently verifiable
nondegeneracy condition. As a second application, we give an alternative
algorithm for learning mixtures of spherical Gaussians with linearly
independent means. These results also hold in the presence of Gaussian noise.


title:
The Curious Case of Glass I: High Ionization and Variability of
  Different Types

abstract:
  Our Spitzer IRS observation of the infrared companion Glass Ib revealed fine
structure emission with high ionization ([NeIII]/[NeII]=2.1 and
[SIV]/[SIII]=0.6) that indicates the gas is likely illuminated by hard
radiation. While models suggest extreme ultraviolet radiation could be present
in T Tauri stars (Hollenbach & Gorti 2009 and references therein), this is the
first detection of [SIV] and such a high [NeIII]/[NeII] ratio in a young star.
We also find that Glass Ib displays the molecules HCN, CO2, and H2O in
emission. Here we investigate the Glass I binary system and consider possible
mechanisms that may have caused the high ionization, whether from an outflow or
disk irradiation. We also model the spectral energy distributions of Glass Ia
and Ib to test if the system is a young member of the Chameleon I star-forming
region, and consider other possible classifications for the system. We find
Glass Ib is highly variable, showing changes in continuum strength and emission
features at optical, near-infrared, and mid-infrared wavelengths. The optical
light curve indicates that a central stellar component in Glass Ib became
entirely visible for 2.5 years beginning in mid-2002, and that possibly
displayed periodic variability with repeated, short-period dimming during that
time. As the fine structure emission was not detected in observations before or
after our Spitzer IRS observation, we explore whether the variable nature of
Glass Ib is related to the gas being highly ionized, possibly due to variable
accretion or an X-ray flare.


title: Nonlocal Edge State Transport in Topological Insulators

abstract:
  We use the N-terminal scheme for studying the edge state transportin in
two-dimensional topological insulators. We find the universal nonlocal response
in the ballistic transport approach. This macroscopic exhibition of the
topological order offers different areas for applications.


title: Entanglement entropy scaling of the XXZ chain

abstract:
  We study the entanglement entropy scaling of the XXZ chain. While in the
critical XY phase of the XXZ chain the entanglement entropy scales
logarithmically with a coefficient that is determined by the associated
conformal field theory, at the ferromagnetic point, however, the system is not
conformally invariant yet the entanglement entropy still scales logarithmically
albeit with a different coefficient. We investigate how such an nontrivial
scaling at the ferromagnetic point influences the estimation of the central
charge $c$ in the critical XY phase. In particular we use the entanglement
scaling of the finite or infinite system, as well as the finite-size scaling of
the ground state energy to estimate the value of $c$. In addition, the
spin-wave velocity and the scaling dimension are also estimated. We show that
in all methods the evaluations are influenced by the nearby ferromagnetic point
and result in crossover behavior. Finally we discuss how to determine whether
the central charge estimation is strongly influenced by the crossover behavior
and how to properly evaluate the central charge.