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arxiv_dataset-27001106.4365 | Constraints on the Light Pseudoscalar Meson Distribution Amplitudes from
Their Meson-Photon Transition Form Factors
hep-ph
The meson-photon transition form factors $\gamma\gamma^*\to P$ ($P$ stands
for $\pi$, $\eta$ and $\eta'$) provide strong constraints on the distribution
amplitudes of the pseudoscalar mesons. In this paper, these transition form
factors are calculated under the light-cone perturbative QCD approach, in which
both the valence and non-valence quarks' contributions have been taken into
consideration. To be consistent, an unified wavefunction model is adopted to
analyze these form factors. It is shown that with proper charm component
$f^{c}_{\eta'}\sim -30$ MeV and a moderate DA with $B\sim 0.30$, the
experimental data on $Q^{2}F_{\eta\gamma}(Q^2)$ and $Q^{2}F_{\eta'\gamma}(Q^2)$
in whole $Q^2$ region can be explained simultaneously. Further more, a detailed
discussion on the form factors' uncertainties caused by the constituent quark
masses $m_q$ and $m_s$, the parameter $B$, the mixing angle $\phi$ and
$f_{\eta'}^c$ are presented. It is found that by adjusting these parameters
within their reasonable regions, one can improve the form factor to a certain
degree but can not solve the puzzle for $Q^{2}F_{\pi\gamma}(Q^2)$, especially
to explain the behavior of $\pi-\gamma$ form factor within the whole $Q^2$
region consistently. We hope further experimental data on these form factors in
the large $Q^2$ region can clarify the present situation.
| arxiv topic:hep-ph |
arxiv_dataset-27011106.4465 | Spin correlations in the extended kagome system YBaCo3FeO7
cond-mat.mtrl-sci
The transition metal based oxide YBaCo3FeO7 is structurally related to the
mineral Swedenborgite SbNaBe4O7, a polar non-centrosymmetric crystal system.
The magnetic Co3Fe sublattice consists of a tetrahedral network containing
kagome-like layers with trigonal interlayer sites. This geometry causes
frustration effects for magnetic ordering, which were investigated by
magnetization measurements, M\"ossbauer spectroscopy, polarized neutron
diffraction, and neutron spectroscopy. Magnetization measurement and neutron
diffraction do not show long range ordering even at low temperature (1 K)
although a strong antiferromagnetic coupling (~2000 K) is deduced from the
magnetic susceptibility. Below 590 K, we observe two features, a spontaneous
weak anisotropic magnetization hysteresis along the polar crystallographic axis
and a hyperfine field on the Fe kagome sites, whereas the Fe spins on the
interlayer sites remain idle. Below ~50 K, the onset of a hyperfine field shows
the development of moments static on the M\"ossbauer time scale also for the Fe
interlayer sites. Simultaneously, an increase of spin correlations is found by
polarized neutron diffraction. The relaxation part of the dynamic response has
been further investigated by high-resolution neutron spectroscopy, which
reveals that the spin correlations start to freeze in below ~50 K. Monte Carlo
simulations show that the neutron scattering results at lower temperatures are
compatible with a recent proposal that the particular geometric frustration in
the Swedenborgite structure promotes quasi one dimensional partial order.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-27021106.4565 | Mt. Suhora M dwarf survey - Detection of eight short-period variable
stars
astro-ph.SR
The Mt. Suhora M\,dwarf survey searching for pulsations in low mass main
sequence stars has acquired CCD photometry of 46 M\,dwarf stars during the
first year of the project (Baran et al 2011). As a by-product of this search
hundreds field stars have been checked for variability. This paper presents our
initial result of a search for periodic variables in field stars observed in
the course of the survey. On the basis of the periodicity and the shape of the
light curves, eight new variables has been detected, among which five are
$\delta$ Scuti stars and three likely RR Lyrae stars. Although variation in one
of the stars has been previously detected, it was classified incorrectly. To
support our classification, in August 2010, we performed spectroscopic
observations to derive spectral types and luminosity classes for all eight
variable stars.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27031106.4665 | Stone structures in the Syrian Desert
physics.geo-ph
An arid land, known as the Syrian Desert, is covering a large part of the
Middle East. In the past, this harsh environment, characterized by huge lava
fields, the "harraat", was considered as a barrier between Levant and
Mesopotamia. When we observe this desert from space, we discover that it is
crossed by some stone structures, the "desert kites", which were the Neolithic
traps for the game. Several stone circles are visible too, as many Stonehenge
sites dispersed in the desert landscape.
| arxiv topic:physics.geo-ph |
arxiv_dataset-27041106.4765 | Phase Diagram of Hard Tetrahedra
cond-mat.soft cond-mat.mtrl-sci cond-mat.stat-mech physics.chem-ph
Advancements in the synthesis of faceted nanoparticles and colloids have
spurred interest in the phase behavior of polyhedral shapes. Regular tetrahedra
have attracted particular attention because they prefer local symmetries that
are incompatible with periodicity. Two dense phases of regular tetrahedra have
been reported recently. The densest known tetrahedron packing is achieved in a
crystal of triangular bipyramids (dimers) with packing density
4000/4671=85.63%. In simulation a dodecagonal quasicrystal is observed; its
approximant, with periodic tiling (3.4.3^2.4), can be compressed to a packing
fraction of 85.03%. Here, we show that the quasicrystal approximant is more
stable than the dimer crystal for packing densities below 84% using Monte Carlo
computer simulations and free energy calculations. To carry out the free energy
calculations, we use a variation of the Frenkel-Ladd method for anisotropic
shapes and thermodynamic integration. The enhanced stability of the approximant
can be attributed to a network substructure, which maximizes the free volume
(and hence the 'wiggle room') available to the particles and facilitates
correlated motion of particles, which further contributes to entropy and leads
to diffusion for packing densities below 65%. The existence of a solid-solid
transition between structurally distinct phases not related by symmetry
breaking -- the approximant and the dimer crystal-- is unusual for hard
particle systems.
| arxiv topic:cond-mat.soft cond-mat.mtrl-sci cond-mat.stat-mech physics.chem-ph |
arxiv_dataset-27051106.4865 | Bound Propagation
cs.AI
In this article we present an algorithm to compute bounds on the marginals of
a graphical model. For several small clusters of nodes upper and lower bounds
on the marginal values are computed independently of the rest of the network.
The range of allowed probability distributions over the surrounding nodes is
restricted using earlier computed bounds. As we will show, this can be
considered as a set of constraints in a linear programming problem of which the
objective function is the marginal probability of the center nodes. In this way
knowledge about the maginals of neighbouring clusters is passed to other
clusters thereby tightening the bounds on their marginals. We show that sharp
bounds can be obtained for undirected and directed graphs that are used for
practical applications, but for which exact computations are infeasible.
| arxiv topic:cs.AI |
arxiv_dataset-27061106.4965 | Conductance of a photochromic molecular switch with graphene leads
cond-mat.mes-hall cond-mat.mtrl-sci
We report a full self-consistent ab initio calculation of the conductance of
a diarylethene-based molecular switch with two graphene electrodes. Our result
show the contributions of the resonant states of the molecule, of the electrode
density of states, and of graphene unique features such as edge states. The
conductivities are found to be significantly different for the two photochromic
isomers at zero and finite applied bias. Further we point out the possibility
of causing the switching by the application of a large potential difference
between the two electrodes.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-27071106.5065 | Common-Resolution Convolution Kernels for Space- and Ground-Based
Telescopes
astro-ph.IM astro-ph.CO astro-ph.GA
Multi-wavelength study of extended astronomical objects requires combining
images from instruments with differing point spread functions (PSFs). We
describe the construction of convolution kernels that allow one to generate
(multi-wavelength) images with a common PSF, thus preserving the colors of the
astronomical sources. We generate convolution kernels for the cameras of the
Spitzer Space Telescope, Herschel Space Observatory, Galaxy Evolution Explorer
(GALEX), Wide-field Infrared Survey Explorer (WISE), ground-based optical
telescopes (Moffat functions and sum of Gaussians), and Gaussian PSFs. These
kernels allow the study of the Spectral Energy Distribution (SED) of extended
objects, preserving the characteristic SED in each pixel. The convolution
kernels and the IDL packages used to construct and use them are made publicly
available.
| arxiv topic:astro-ph.IM astro-ph.CO astro-ph.GA |
arxiv_dataset-27081106.5165 | Preferential Forest-assembly of Single-Wall Carbon Nanotubes on
Low-energy Electron-beam Patterned Nafion Films
cond-mat.mtrl-sci
With the aid of low-energy (500 eV) electron-beam direct writing, patterns of
perpendicularly-aligned Single-wall carbon nanotube (SWNT) forests were
realized on Nafion modified substrates via Fe3+ assisted self-assembly.
Infrared spectroscopy (IR), atomic force microscopy (AFM) profilometry and
contact angle measurements indicated that low-energy electron-beam cleaved the
hydrophilic side chains (-SO3H and C-O-C) of Nafion to low molecular byproducts
that sublimed in the ultra-high vacuum (UHV) environment exposing the
hydrophobic Nafion backbone. Auger mapping and AFM microscopy affirmed that the
exposed hydrophobic domains absorbed considerably less Fe3+ ions upon exposure
to pH 2.2 aqueous FeCl3 solution, which yield considerably less FeO(OH)/FeOCl
precipitates (FeO(OH) in majority) upon washing with lightly basic DMF solution
containing trace amounts of adsorbed moisture. Such differential deposition of
FeO(OH)/FeOCl precipitates provided the basis for the patterned site-specific
self-assembly of SWNT forests as demonstrated by AFM and resonance Raman
spectroscopy.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-27091106.5265 | Planning Through Stochastic Local Search and Temporal Action Graphs in
LPG
cs.AI
We present some techniques for planning in domains specified with the recent
standard language PDDL2.1, supporting 'durative actions' and numerical
quantities. These techniques are implemented in LPG, a domain-independent
planner that took part in the 3rd International Planning Competition (IPC). LPG
is an incremental, any time system producing multi-criteria quality plans. The
core of the system is based on a stochastic local search method and on a
graph-based representation called 'Temporal Action Graphs' (TA-graphs). This
paper focuses on temporal planning, introducing TA-graphs and proposing some
techniques to guide the search in LPG using this representation. The
experimental results of the 3rd IPC, as well as further results presented in
this paper, show that our techniques can be very effective. Often LPG
outperforms all other fully-automated planners of the 3rd IPC in terms of speed
to derive a solution, or quality of the solutions that can be produced.
| arxiv topic:cs.AI |
arxiv_dataset-27101106.5365 | $\rho$ Meson Decay in 2+1 Flavor Lattice QCD
hep-lat
We perform a lattice QCD study of the $\rho$ meson decay from the $N_f=2+1$
full QCD configurations generated with a renormalization group improved gauge
action and a non-perturbatively $O(a)$-improved Wilson fermion action. The
resonance parameters, the effective $\rho\to\pi\pi$ coupling constant and the
resonance mass, are estimated from the $P$-wave scattering phase shift for the
isospin I=1 two-pion system. The finite size formulas are employed to calculate
the phase shift from the energy on the lattice. Our calculations are carried
out at two quark masses, $m_\pi=410\,{\rm MeV}$ ($m_\pi/m_\rho=0.46$) and
$m_\pi=300\,{\rm MeV}$ ($m_\pi/m_\rho=0.35$), on a $32^3\times 64$
($La=2.9\,{\rm fm}$) lattice at the lattice spacing $a=0.091\,{\rm fm}$. We
compare our results at these two quark masses with those given in the previous
works using $N_f=2$ full QCD configurations and the experiment.
| arxiv topic:hep-lat |
arxiv_dataset-27111106.5465 | SPECI-2: An open-source framework for predictive simulation of
cloud-scale data-centres
cs.DC
We introduce Version 2 of SPECI, a system for predictive simulation modeling
of large-scale data-centres, i.e. warehouse-sized facilities containing
hundreds of thousands of servers, as used to provide cloud services.
| arxiv topic:cs.DC |
arxiv_dataset-27121106.5565 | Oxygen adsorption effect on magnetic properties of graphite
cond-mat.mes-hall cond-mat.mtrl-sci
Both experimental and theoretical studies of the magnetic properties of
micrographite and nanographite indicate a crucial role of the partial oxidation
of graphitic zigzag edges in ferromagnetism. In contrast to total and partial
hydrogenation, the oxidation of half of the carbon atoms on the graphite edges
transforms the antiferromagnetic exchange interaction between graphite planes
and over graphite ribbons to the ferromagnetic interaction. The stability of
the ferromagnetism is discussed.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-27131106.5665 | The Weyl extension algebra of $GL_2(\bar{\mathbb{F}}_p)$
math.RT
We compute the Yoneda extension algebra of the collection of Weyl modules for
$GL_2$ over an algebraically closed field of positive characteristic p by
developing a theory of generalised Koszul duality for certain 2-functors, one
of which controls the rational representation theory of $GL_2$ over such a
field.
| arxiv topic:math.RT |
arxiv_dataset-27141106.5765 | Finite-momentum superfluidity and phase transitions in a p-wave resonant
Bose gas
cond-mat.quant-gas cond-mat.other
We study a degenerate two-species gas of bosonic atoms interacting through a
p-wave Feshbach resonance as for example realized in a Rb85-Rb87 mixture. We
show that in addition to a conventional atomic and a p-wave molecular spinor-1
superfluidity at large positive and negative detunings, respectively, the
system generically exhibits a finite momentum atomic-molecular superfluidity at
intermediate detuning around the unitary point. We analyze the detailed nature
of the corresponding phases and the associated quantum and thermal phase
transitions.
| arxiv topic:cond-mat.quant-gas cond-mat.other |
arxiv_dataset-27151106.5865 | Oscillating instanton solutions in curved space
hep-th
We investigate oscillating instanton solutions of a self-gravitating scalar
field between degenerate vacua. We show that there exist O(4)-symmetric
oscillating solutions in a de Sitter background. The geometry of this solution
is finite and preserves the $Z_{2}$ symmetry. The nontrivial solution
corresponding to tunneling is possible only if the effect of gravity is taken
into account. We present numerical solutions of this instanton, including the
phase diagram of solutions in terms of the parameters of the present work and
the variation of energy densities. Our solutions can be interpreted as
solutions describing an instanton-induced domain wall or braneworld-like object
rather than a kink-induced domain wall or braneworld. The oscillating instanton
solutions have a thick wall and the solutions can be interpreted as a mechanism
providing nucleation of the thick wall for topological inflation. We remark
that $Z_{2}$ invariant solutions also exist in a flat and anti-de Sitter
background, though the physical significance is not clear.
| arxiv topic:hep-th |
arxiv_dataset-27161106.5965 | Schwinger effect in inhomogeneous electric fields
hep-ph hep-th quant-ph
The vacuum of quantum electrodynamics is unstable against the formation of
many-body states in the presence of an external electric field, manifesting
itself as the creation of electron-positron pairs (Schwinger effect). This
effect has been a long-standing but still unobserved prediction as the
generation of the required field strengths has not been feasible so far.
However, due to the advent of a new generation of high-intensity laser systems
such as the European XFEL or the Extreme Light Infrastructure (ELI), this
effect might eventually become observable within the next decades. Based on the
equal-time Wigner formalism, various aspects of the Schwinger effect in
electric fields showing both temporal and spatial variations are investigated.
Regarding the Schwinger effect in time-dependent electric fields, analytic
expressions for the equal-time Wigner function in the presence of a static as
well as a pulsed electric field are derived. Moreover, the pair creation
process in the presence of a pulsed electric field with sub-cycle structure,
which acts as a model for a realistic laser pulse, is examined. Finally, an ab
initio simulation of the Schwinger effect in a simple space- and time-dependent
electric field is performed for the first time, allowing for the calculation of
the time evolution of various observables like the charge density, the particle
number density or the number of created particles.
| arxiv topic:hep-ph hep-th quant-ph |
arxiv_dataset-27171106.6065 | Strong pinning and vortex energy distributions in single crystalline
Ba(Fe1-xCox)2As2
cond-mat.supr-con
The interrelation between heterogeneity and flux pinning is studied in
Ba(Fe1-xCox)2As2 single crystals with widely varying Co-content x. Magnetic
Bitter decoration of the superconducting vortex ensemble in crystals with x =
0:075 and x = 0:1 reveal highly disordered vortex structures. The width of the
Meissner belt observed at the edges of the crystals, and above the surface
steps formed by cleaving, as well as the width of the intervortex distance
distribution, indicate that the observed vortex ensemble is established at a
temperature just below the critical temperature Tc. The vortex interaction
energy and pinning force distributions extracted from the images strongly
suggest that the vortex lattice disorder is attributable to strong pinning due
to spatial fluctuations of Tc and of the superfluid density. Correlating the
results with the critical current density yields a typical length scale of the
relevant disorder of 40 - 60 nm.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-27181106.6165 | The backreaction of anti-D3 branes on the Klebanov-Strassler geometry
hep-th
We present the full numerical solution for the 15-dimensional space of
linearized deformations of the Klebanov-Strassler background which preserve the
SU(2) X SU(2) X Z_2 symmetries. We identify within this space the solution
corresponding to anti-D3 branes, (modulo the presence of a certain subleading
singularity in the infrared). All the 15 integration constants of this solution
are fixed in terms of the number of anti-D3 branes, and the solution differs in
the UV from the supersymmetric solution into which it is supposed to decay by a
mode corresponding to a rescaling of the field theory coordinates. Deciding
whether two solutions that differ in the UV by a rescaling mode are dual to the
same theory is involved even for supersymmetric Klebanov-Strassler solutions,
and we explain in detail some of the subtleties associated to this.
| arxiv topic:hep-th |
arxiv_dataset-27191106.6265 | Disorder-induced Majorana metal in interacting non-Abelian anyon systems
cond-mat.str-el cond-mat.dis-nn
We demonstrate that a thermal metal of Majorana fermions forms in a
two-dimensional system of interacting non-Abelian (Ising) anyons in the
presence of moderate disorder. This bulk metallic phase arises in the $\nu=5/2$
quantum Hall state when disorder pins the anyonic quasiparticles. More
generally, it naturally occurs for various proposed systems supporting Majorana
fermion zero modes when disorder induces the random pinning of a finite density
of vortices. This includes all two-dimensional topological superconductors in
so-called symmetry class D. A distinct experimental signature of the thermal
metal phase is the presence of bulk heat transport down to zero temperature.
| arxiv topic:cond-mat.str-el cond-mat.dis-nn |
arxiv_dataset-27201107.0008 | Double Field Theory of Type II Strings
hep-th
We use double field theory to give a unified description of the low energy
limits of type IIA and type IIB superstrings. The Ramond-Ramond potentials fit
into spinor representations of the duality group O(D,D) and field-strengths are
obtained by acting with the Dirac operator on the potentials. The action,
supplemented by a Spin^+(D,D)-covariant self-duality condition on field
strengths, reduces to the IIA and IIB theories in different frames. As usual,
the NS-NS gravitational variables are described through the generalized metric.
Our work suggests that the fundamental gravitational variable is a hermitian
element of the group Spin(D,D) whose natural projection to O(D,D) gives the
generalized metric.
| arxiv topic:hep-th |
arxiv_dataset-27211107.0108 | Observation of the antimatter helium-4 nucleus at RHIC
nucl-ex
We present the observation of the \Heebar nucleus, the heaviest antinucleus
observed to date. In total, 18 \Heebar counts were detected at the STAR
experiment at RHIC in 10$^{9}$ recorded Au+Au collisions at beam energies of
$\sqrt{s_{NN}}$ = 200 GeV and 62 GeV. The background has been estimated, and
the misidentification probability is found to be lower than 10$^{-11}$.
| arxiv topic:nucl-ex |
arxiv_dataset-27221107.0208 | Large Deviations for Non-Crossing Partitions
math.PR
We prove a large deviations principle for the empirical law of the block
sizes of a uniformly distributed non-crossing partition. As an application we
obtain a variational formula for the maximum of the support of a compactly
supported probability measure in terms of its free cumulants, provided these
are all non-negative. This is useful in free probability theory, where
sometimes the R-transform is known but cannot be inverted explicitly to yield
the density.
| arxiv topic:math.PR |
arxiv_dataset-27231107.0308 | Contact-Density Analysis of Lattice Polymer Adsorption Transitions
cond-mat.stat-mech q-bio.BM
By means of contact-density chain-growth simulations, we investigate a simple
lattice model of a flexible polymer interacting with an attractive substrate.
The contact density is a function of the numbers of monomer-substrate and
monomer-monomer contacts. These contact numbers represent natural order
parameters and allow for a comprising statistical study of the conformational
space accessible to the polymer in dependence of external parameters such as
the attraction strength of the substrate and the temperature. Since the contact
density is independent of the energy scales associated to the interactions, its
logarithm is an unbiased measure for the entropy of the conformational space.
By setting explicit energy scales, the thus defined, highly general
microcontact entropy can easily be related to the microcanonical entropy of the
corresponding hybrid polymer-substrate system.
| arxiv topic:cond-mat.stat-mech q-bio.BM |
arxiv_dataset-27241107.0408 | Harmonic analysis and the Riemann-Roch theorem
math.AG math.NT
This paper is a continuation of papers: arXiv:0707.1766 [math.AG] and
arXiv:0912.1577 [math.AG]. Using the two-dimensional Poisson formulas from
these papers and two-dimensional adelic theory we obtain the Riemann-Roch
formula on a projective smooth algebraic surface over a finite field.
| arxiv topic:math.AG math.NT |
arxiv_dataset-27251107.0508 | A Detailed Study of the Molecular and Atomic Gas Toward the {\gamma}-ray
SNR RX J1713.7-3946: Spatial TeV {\gamma}-ray and ISM Gas Correspondence
astro-ph.GA
RX J1713.7$-$3946 is the most remarkable TeV $\gamma$-ray SNR which emits
$\gamma$-rays in the highest energy range. We made a new combined analysis of
CO and \ion{H}{1} in the SNR and derived the total protons in the interstellar
medium (ISM). We have found that the inclusion of the \ion{H}{1} gas provides a
significantly better spatial match between the TeV $\gamma$-rays and ISM
protons than the H$_2$ gas alone. In particular, the southeastern rim of the
$\gamma$-ray shell has a counterpart only in the \ion{H}{1}. The finding shows
that the ISM proton distribution is consistent with the hadronic scenario that
comic ray (CR) protons react with ISM protons to produce the $\gamma$-rays.
This provides another step forward for the hadronic origin of the $\gamma$-rays
by offering one of the necessary conditions missing in the previous hadronic
interpretations. We argue that the highly inhomogeneous distribution of the ISM
protons is crucial in the origin of the $\gamma$-rays. Most of the neutral gas
was likely swept up by the stellar wind of an OB star prior to the SNe to form
a low-density cavity and a swept-up dense wall. The cavity explains the
low-density site where the diffusive shock acceleration of charged particles
takes place with suppressed thermal X-rays, whereas the CR protons can reach
the target protons in the wall to produce the $\gamma$-rays. The present
finding allows us to estimate the total CR proton energy to be $\sim 10^{48}$
ergs, 0.1% of the total energy of a SNe.
| arxiv topic:astro-ph.GA |
arxiv_dataset-27261107.0608 | Maximum-likelihood reconstruction of photon returns from simultaneous
analog and photon-counting lidar measurements
physics.ao-ph astro-ph.EP astro-ph.IM physics.geo-ph physics.ins-det
We present a novel method for combining the analog and photon-counting
measurements of lidar transient recorders into reconstructed photon returns.
The method takes into account the statistical properties of the two measurement
modes and estimates the most likely number of arriving photons and the most
likely values of acquisition parameters describing the two measurement modes.
It extends and improves the standard combining ("gluing") methods and does not
rely on any ad hoc definitions of the overlap region nor on any ackground
subtraction methods.
| arxiv topic:physics.ao-ph astro-ph.EP astro-ph.IM physics.geo-ph physics.ins-det |
arxiv_dataset-27271107.0708 | Generalized Uncertainty Principle and Self-dual Black Holes
gr-qc hep-th
The Generalized Uncertainty Principle suggests corrections to the Uncertainty
Principle as the energy increases towards the Planck value. It provides a
natural transition between the expressions for the Compton wavelength below the
Planck mass and the black hole event horizon size above this mass. It also
suggests corrections to the the event horizon size as the black hole mass falls
towards the Planck value, leading to the concept of a Generalized Event
Horizon. Extrapolating below the Planck mass suggests the existence of a new
class of black holes, whose size is of order the Compton wavelength for their
mass. Such sub-Planckian black holes have recently been discovered in the
context of loop quantum gravity and it is possible that this applies more
generally. This suggests an intriguing connection between black holes, the
Uncertainty Principle and quantum gravity.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-27281107.0808 | Critical current measurements in superconductor - ferromagnet -
superconductor junctions of $YBa_2Cu_3O_y$-$SrRuO_3$-$YBa_2Cu_3O_y$: No
evidence for a dominant proximity induced triplet superconductivity in the
ferromagnetic barrier
cond-mat.supr-con cond-mat.str-el
Transport measurements in ramp-type junctions of
$YBa_2Cu_3O_y-SrRuO_3-YBa_2Cu_3O_y$ with $T_c$ values of either 80-90 K or
60-70 K are reported. In both type of junctions but without a barrier
("shorts"), the supercurrent densities at 4.2 K reached 7.5 and 3.5 MA/cm$^2$,
respectively, indicating the high quality of the fabrication process. Plots of
the critical current versus thickness of the ferromagnetic barrier at 4.2 K
show exponential decays with decay lengths of 1.1 nm for the 90 K phase and 1.4
nm for the 60 K phase, which are much shorter than the relevant coherence
lengths $\xi_F\sim 5-6$ nm or $\xi_N\sim$16 nm of $SrRuO_3$. We thus conclude
that there is no dominant proximity induced triplet superconductivity in the
ferromagnet in our junctions.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-27291107.0908 | Solar Magnetic Fields
astro-ph.SR
This review provides an introduction to the generation and evolution of the
Sun's magnetic field, summarising both observational evidence and theoretical
models. The eleven year solar cycle, which is well known from a variety of
observed quantities, strongly supports the idea of a large-scale solar dynamo.
Current theoretical ideas on the location and mechanism of this dynamo are
presented.
The solar cycle influences the behaviour of the global coronal magnetic field
and it is the eruptions of this field that can impact on the Earth's
environment. These global coronal variations can be modelled to a surprising
degree of accuracy. Recent high resolution observations of the Sun's magnetic
field in quiet regions, away from sunspots, show that there is a continual
evolution of a small-scale magnetic field, presumably produced by small-scale
dynamo action in the solar interior.
Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and
disperse over a period of several days. Numerical simulations can help to
determine the physical processes governing the emergence of sunspots. We
discuss the interaction of these emerging fields with the pre-existing coronal
field, resulting in a variety of dynamic phenomena.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27301107.1008 | Modified Chaplygin Gas and Solvable F-essence Cosmologies
physics.gen-ph
The Modified Chaplygin Gas (MCG) model belongs to the class of a unified
models of dark energy and dark matter. In this paper, we have modeled MCG in
the framework of f-essence cosmology. By constructing an equation connecting
the MCG and the f-essence, we solve it to obtain explicitly the pressure and
energy density of MCG. As special cases, we obtain both positive and negative
pressure solutions for suitable choices of free parameters. We also calculate
the state parameter which describes the phantom crossing.
| arxiv topic:physics.gen-ph |
arxiv_dataset-27311107.1108 | A scale-invariant probabilistic model based on Leibniz-like pyramids
cond-mat.stat-mech math-ph math.MP
We introduce a family of probabilistic {\it scale-invariant} Leibniz-like
pyramids and $(d+1)$-dimensional hyperpyramids ($d=1,2,3,...$), characterized
by a parameter $\nu>0$, whose value determines the degree of correlation
between $N$ $(d+1)$-valued random variables. There are $(d+1)^N$ different
events, and the limit $\nu\to\infty$ corresponds to independent random
variables, in which case each event has a probability $1/(d+1)^N$ to occur. The
sums of these $N$ $\,(d+1)$-valued random variables correspond to a
$d-$dimensional probabilistic model, and generalizes a recently proposed
one-dimensional ($d=1$) model having $q-$Gaussians (with $q=(\nu-2)/(\nu-1)$
for $\nu \in [1,\infty)$) as $N\to\infty$ limit probability distributions for
the sum of the $N$ binary variables [A. Rodr\'{\i}guez {\em et al}, J. Stat.
Mech. (2008) P09006; R. Hanel {\em et al}, Eur. Phys. J. B {\bf 72}, 263
(2009)]. In the $\nu\to\infty$ limit the $d-$dimensional multinomial
distribution is recovered for the sums, which approach a $d-$dimensional
Gaussian distribution for $N\to\infty$. For any $\nu$, the conditional
distributions of the $d-$dimensional model are shown to yield the corresponding
joint distribution of the $(d-1)$-dimensional model with the same $\nu$. For
the $d=2$ case, we study the joint probability distribution, and identify two
classes of marginal distributions, one of them being asymmetric and
scale-invariant, while the other one is symmetric and only asymptotically
scale-invariant. The present probabilistic model is proposed as a testing
ground for a deeper understanding of the necessary and sufficient conditions
for having $q$-Gaussian attractors in the $N\to\infty$ limit, the ultimate goal
being a neat mathematical view of the causes clarifying the ubiquitous
emergence of $q$-statistics verified in many natural, artificial and social
systems.
| arxiv topic:cond-mat.stat-mech math-ph math.MP |
arxiv_dataset-27321107.1208 | Microscopic Mechanism of Specific Peptide Adhesion to Semiconductor
Substrates
cond-mat.mes-hall cond-mat.soft cond-mat.stat-mech q-bio.BM
The design of hybrid peptide-solid interfaces for nanotechnological
applications such as biomolecular nanoarrays requires a deep understanding of
the basic mechanisms of peptide binding and assembly at solid substrates. Here
we show by means of experimental and computational analyses that the adsorption
properties of mutated synthetic peptides at semiconductors exhibit a clear
sequence-dependent adhesion specificity. Our simulations of a novel hybrid
peptide-substrate model reveal the correspondence between proline mutation and
binding affinity to a clean silicon substrate. After synthesizing theoretically
suggested amino-acid sequences with different binding behavior, we confirm the
relevance of the selective mutations upon adhesion in our subsequent atomic
force microscopy experiments.
| arxiv topic:cond-mat.mes-hall cond-mat.soft cond-mat.stat-mech q-bio.BM |
arxiv_dataset-27331107.1308 | Drift wave turbulence in a dense semiclassical magnetoplasma
physics.plasm-ph
A semiclassical nonlinear collisional drift wave model for dense magnetized
plasmas is developed and solved numerically. The effects of fluid electron
density fluctuations associated with quantum statistical pressure and quantum
Bohm force are included, and their influences on the collisional drift wave
instability and the resulting fully developed nanoscale drift wave turbulence
are discussed. It is found that the quantum effects increase the growth rate of
the collisional drift wave instability, and introduce a finite de Broglie
length screening on the drift wave turbulent density perturbations. The
relevance to nanoscale turbulence in nonuniform dense magnetoplasmas is
discussed.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-27341107.1408 | On resolutions of diagrams of algebras
math.AT math.KT
We prove a restricted version of a conjecture by M. Markl on resolutions of
an operad describing diagrams of algebras. We discuss a particular case related
to the Gerstenhaber-Schack diagram cohomology.
| arxiv topic:math.AT math.KT |
arxiv_dataset-27351107.1508 | A note on ANR's
math.GN
It is shown that if for a complete metric space $(X,d)$ there is a constant
$\epsilon > 0$ such that the intersection $\bigcap_{j=1}^n B_d(x_j,r_j)$ of
open balls is nonempty for every finite system $x_1,...,x_n \in X$ of centers
and a corresponding system of radii $r_1,...,r_n > 0$ such that $d(x_j,x_k)
\leqsl \epsilon$ and $d(x_j,x_k) < r_j + r_k$ ($j,k = 1,...,n$), then $X$ is an
ANR; and if in the above one may put $\epsilon = \infty$, the space $X$ is an
AR. A certain criterion for an incomplete metric space to be an A(N)R is
presented.
| arxiv topic:math.GN |
arxiv_dataset-27361107.1608 | Formation of Common Investment Networks by Project Establishment between
Agents
cs.SI cs.CE
We present an investment model integrated with trust-reputation mechanisms
where agents interact with each other to establish investment projects. We
investigate the establishment of investment projects, the influence of the
interaction between agents in the evolution of the distribution of wealth, as
well as the formation of common investment networks and some of their
properties. Simulation results show that the wealth distribution presents a
power law in its tail. Also, it is shown that the trust and reputation
mechanism presented leads to the establishment of networks among agents, which
present some of the typical characteristics of real-life networks like a high
clustering coefficient and short average path length.
| arxiv topic:cs.SI cs.CE |
arxiv_dataset-27371107.1708 | The spectrum of (136199) Eris between 350 and 2350 nm: Results with
X-Shooter
astro-ph.EP
X-Shooter is the first second-generation instrument for the ESO-VLT. It as a
spectrograph covering the 300 - 2480 nm spectral range at once with a high
resolving power. These properties enticed us to observe (136199) Eris during
the science verification of the instrument. The target has numerous absorption
features in the optical and near-infrared domain which has been observed by
different authors, showing differences in their positions and strengths.
We attempt at constraining the existence of super-volatiles, e.g., CH4, CO
and N2, and in particular try to understand the physical-chemical state of the
ices on Eris' surface.
We observed Eris in the 300-2480 nm range and compared the newly obtained
spectra with those available in the literature. We identified several
absorption features, measuring their positions and depth and compare them with
those of reflectance of pure methane ice obtained from the optical constants of
this ice at 30 K to study shifts in their positions and find a possible
explanation for their origin.
We identify several absorption bands in the spectrum all consistent with the
presence of CH4 ice. We do not identify bands related with N2 or CO. We
measured the central wavelengths of the bands and find variable shifts, with
respect to the spectrum of pure CH4 at 30 K. Conclusions. Based on these
wavelength shifts we confirm the presence of a dilution of CH4 in other ice on
the surface of Eris and the presence of pure CH4 spatially segregated. The
comparison of the centers and shapes of these bands with previous works suggest
that the surface is heterogeneous. The absence of the 2160 nm band of N2 can be
explained if the surface temperature is below 35.6 K, the transition
temperature between the alpha and beta phases of this ice. Our results,
including the reanalysis of data published elsewhere, point to an heterogeneous
surface on Eris.
| arxiv topic:astro-ph.EP |
arxiv_dataset-27381107.1808 | Application of Jet Trimming in Boosted Higgs Search
hep-ph
We present the study of the $WH$ and $ZH$ search with the Higgs Boson decayed
to $b\bar{b}$ at the Large Hadron Collider. The Higgs Boson and the Vector
Boson are required to be boosted, and the Higgs Boson is reconstructed with Jet
Trimming Technique. The statistical significance for 30$fb^{-1}$ data is 4.5
$\sigma$, which is comparable to the previous result.
| arxiv topic:hep-ph |
arxiv_dataset-27391107.1908 | The inefficiency of re-weighted sampling and the curse of system size in
high order path integration
physics.chem-ph cond-mat.stat-mech
Computing averages over a target probability density by statistical
re-weighting of a set of samples with a different distribution is a strategy
which is commonly adopted in fields as diverse as atomistic simulation and
finance. Here we present a very general analysis of the accuracy and efficiency
of this approach, highlighting some of its weaknesses. We then give an example
of how our results can be used, specifically to assess the feasibility of
high-order path integral methods. We demonstrate that the most promising of
these techniques -- which is based on re-weighted sampling -- is bound to fail
as the size of the system is increased, because of the exponential growth of
the statistical uncertainty in the re-weighted average.
| arxiv topic:physics.chem-ph cond-mat.stat-mech |
arxiv_dataset-27401107.2008 | Analytic Models for the Evolution of Semilocal String Networks
hep-ph astro-ph.CO hep-th
We revisit previously developed analytic models for defect evolution and
adapt them appropriately for the study of semilocal string networks. We thus
confirm the expectation (based on numerical simulations) that linear scaling
evolution is the attractor solution for a broad range of model parameters. We
discuss in detail the evolution of individual semilocal segments, focusing on
the phenomenology of segment growth, and also provide a preliminary comparison
with existing numerical simulations.
| arxiv topic:hep-ph astro-ph.CO hep-th |
arxiv_dataset-27411107.2108 | On the numerical evaluation of algebro-geometric solutions to integrable
equations
math-ph math.AG math.MP nlin.SI
Physically meaningful periodic solutions to certain integrable partial
differential equations are given in terms of multi-dimensional theta functions
associated to real Riemann surfaces. Typical analytical problems in the
numerical evaluation of these solutions are studied. In the case of
hyperelliptic surfaces efficient algorithms exist even for almost degenerate
surfaces. This allows the numerical study of solitonic limits. For general real
Riemann surfaces, the choice of a homology basis adapted to the
anti-holomorphic involution is important for a convenient formulation of the
solutions and smoothness conditions. Since existing algorithms for algebraic
curves produce a homology basis not related to automorphisms of the curve, we
study symplectic transformations to an adapted basis and give explicit formulae
for M-curves. As examples we discuss solutions of the Davey-Stewartson and the
multi-component nonlinear Schr\"odinger equations.
| arxiv topic:math-ph math.AG math.MP nlin.SI |
arxiv_dataset-27421107.2208 | Mode conversion of radiatively damped magnetogravity waves in the solar
chromosphere
astro-ph.SR
Modelling of adiabatic gravity wave propagation in the solar atmosphere
showed that mode conversion to field guided acoustic waves or Alfv\'en waves
was possible in the presence of highly inclined magnetic fields. This work aims
to extend the previous adiabatic study, exploring the consequences of radiative
damping on the propagation and mode conversion of gravity waves in the solar
atmosphere. We model gravity waves in a VAL-C atmosphere, subject to a uniform,
and arbitrarily orientated magnetic field, using the Newton cooling
approximation for radiatively damped propagation. The results indicate that the
mode conversion pathways identified in the adiabatic study are maintained in
the presence of damping. The wave energy fluxes are highly sensitive to the
form of the height dependence of the radiative damping time. While simulations
starting from 0.2 Mm result in modest flux attenuation compared to the
adiabatic results, short damping times expected in the low photosphere
effectively suppress gravity waves in simulations starting at the base of the
photosphere. It is difficult to reconcile our results and observations of
propagating gravity waves with significant energy flux at photospheric heights
unless they are generated in situ, and even then, why they are observed to be
propagating as low as 70 km where gravity waves should be radiatively
overdamped.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27431107.2308 | Linearized flavor-stability analysis of dense neutrino streams
hep-ph astro-ph.SR
Neutrino-neutrino interactions in dense neutrino streams, like those emitted
by a core-collapse supernova, can lead to self-induced neutrino flavor
conversions. While this is a nonlinear phenomenon, the onset of these
conversions can be examined through a standard stability analysis of the
linearized equations of motion. The problem is reduced to a linear eigenvalue
equation that involves the neutrino density, energy spectrum, angular
distribution, and matter density. In the single-angle case, we reproduce
previous results and use them to identify two generic instabilities: The system
is stable above a cutoff density ("cutoff mode"), or can approach an asymptotic
instability for increasing density ("saturation mode"). We analyze multi-angle
effects on these generic types of instabilities and find that even the
saturation mode is suppressed at large densities. For both types of modes, a
given multi-angle spectrum typically is unstable when the neutrino and electron
densities are comparable, but stable when the neutrino density is much smaller
or much larger than the electron density. The role of an instability in the SN
context depends on the available growth time and on the range of affected
modes. At large matter density, most modes are off-resonance even when the
system is unstable.
| arxiv topic:hep-ph astro-ph.SR |
arxiv_dataset-27441107.2408 | Constraints on Enhanced Dark Matter Annihilation from IceCube Results
hep-ph astro-ph.HE hep-ex
Excesses on positron and electron fluxes measured by ATIC, and the PAMELA and
Fermi--LAT telescopes can be explained by dark matter annihilation in our
Galaxy. However, this requires large boosts on the dark matter annihilation
rate. There are many possible enhancement mechanisms, such as the Sommerfeld
effect or the existence of dark matter clumps in our halo. If enhancements on
the dark matter annihilation cross section are taking place, the dark matter
annihilation in the core of the Earth should also be enhanced. Here we use
recent results from the IceCube 40-string configuration to probe generic
enhancement scenarios. We present results as a function of the dark
matter-proton interaction cross section, $\sigma_{\chi p}$ weighted by the
branching fraction into neutrinos, $f_{\nu\bar{\nu}}$, as a function of a
generic boost factor, $B_F$, which parametrizes the expected enhancement of the
annihilation rate. We find that dark matter models which require annihilation
enhancements of $\mathcal{O}(100)$ or more and that annihilate significantly
into neutrinos are excluded as the explanation for these excesses. We also
determine the boost range that can be probed by the full IceCube telescope.
| arxiv topic:hep-ph astro-ph.HE hep-ex |
arxiv_dataset-27451107.2508 | Magnetic Impurities in Graphene
cond-mat.str-el
We used a quantum Monte Carlo method to study the magnetic impurity adatoms
on graphene. We found that by tuning the chemical potential we could switch the
values of the impurity's local magnet moment between relatively large and small
values. Our computations of the impurity's spectral density found its behavior
to differ significantly from that of an impurity in a normal metal and our
computations of the charge-charge and spin-spin correlations between the
impurity and the conduction band electrons found them to be strongly
suppressed. In general our results are consistent with those from poor man's
scaling and numerical renormalization group methods.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-27461107.2608 | Size of stripe domains in a superconducting ferromagnet
cond-mat.supr-con cond-mat.str-el
In a superconducting ferromagnet, the superconducting state appears in the
ferromagnetic phase where usually a domain structure has already developed. We
study the influence of the superconducting screening currents on a stripe
structure with out-of-plane magnetization, in a film of arbitrary thickness. We
find that superconductivity always induces a shrinkage of the domains, and
there is a critical value of penetration depth below which a mono-domain
structure is more stable than the periodic one. Furthermore we investigate the
possible different effects of singlet and triplet superconductivity on the
domain width, as well as the conditions for the existence of vortices in the
domains. The obtained results are then discussed in light of the experimental
data of superconducting ferromagnets URhGe, UGe2, and UCoGe.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-27471107.2708 | Generation-recombination processes via acoustic phonons in a disorded
graphene
cond-mat.mtrl-sci
Generation-recombination interband transitions via acoustic phonons are
allowed in a disordered graphene because of violation of the energy-momentum
conservation requirements. The generation-recombination processes are analyzed
for the case of scattering by a short-range disorder and the deformation
interaction of carriers with in-plane acoustic modes. The
generation-recombination rates were calculated for the cases of intrinsic and
heavily-doped graphene at room temperature. The transient evolution of
nonequilibrium carriers is described by the exponential fit dependent on doping
conditions and disorder level. The characteristic relaxation times are
estimated to be about 150 - 400 ns for sample with the maximal sheet resistance
~5 kOhm. This rate is comparable with the generation-recombination processes
induced by the thermal radiation.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-27481107.2808 | Global Distribution of Fe K alpha Lines in the Galactic Center Region
Observed with the Suzaku Satellite
astro-ph.HE
We have surveyed spatial profiles of the Fe K$\alpha$ lines in the Galactic
center diffuse X-rays (GCDX), including the transient region from the GCDX to
the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We
resolved Fe K$\alpha$ line complex into three lines of Fe \emissiontype{I}, Fe
\emissiontype{XXV} and Fe \emissiontype{XXVI} K$\alpha$, and obtained their
spatial intensity profiles with the resolution of $\sim \timeform{0D.1}$. We
compared the Fe \emissiontype{XXV} K$\alpha$ profile with a stellar mass
distribution (SMD) model made from near infrared observations. The intensity
profile of Fe \emissiontype{XXV} K$\alpha$ is nicely fitted with the SMD model
in the GRXE region, while that in the GCDX region shows $3.8\pm0.3$
$(\timeform{0D.2}<|l|<\timeform{1D.5})$ or $19\pm6$ $(|l|<\timeform{0D.2})$
times excess over the best-fit SMD model in the GRXE region. Thus Fe
\emissiontype{XXV} K$\alpha$ in the GCDX is hardly explained by the same origin
of the GRXE. In the case of point source origin, a new population with the
extremely strong Fe \emissiontype{XXV} K$\alpha$ line is required. An
alternative possibility is that the majority of the GCDX is truly diffuse
optically thin thermal plasma.
| arxiv topic:astro-ph.HE |
arxiv_dataset-27491107.2908 | CTC assisted PR box type correlation can lead to signaling
quant-ph
It is known that there exist non-local correlations that respect no-signaling
criterion, but violate Bell-type inequalities more than quantum-mechanical
correlations. Such super quantum correlations were introduced as the
Popescu-Rohrlich (PR) box. We consider such non-local boxes with two/three
inputs and two/three outputs. We show that these super quantum correlations can
lead to signaling when at least one of the input bit has access to a word line
along a closed time-like curve.
| arxiv topic:quant-ph |
arxiv_dataset-27501107.3008 | Macroscopic Quantum Phenomena from the Correlation, Coupling and
Criticality Perspectives
quant-ph
In this sequel paper we explore how macroscopic quantum phenomena can be
measured or understood from the behavior of quantum correlations which exist in
a quantum system of many particles or components and how the interaction
strengths change with energy or scale, under ordinary situations and when the
system is near its critical point. We use the nPI (master) effective action
related to the Boltzmann-BBGKY / Schwinger-Dyson hierarchy of equations as a
tool for systemizing the contributions of higher order correlation functions to
the dynamics of lower order correlation functions. Together with the large N
expansion discussed in our first paper(MQP1) we explore 1) the conditions
whereby an H-theorem is obtained, which can be viewed as a signifier of the
emergence of macroscopic behavior in the system. We give two more examples from
past work: 2) the nonequilibrium dynamics of N atoms in an optical lattice
under the large $\cal N$ (field components), 2PI and second order perturbative
expansions, illustrating how N and $\cal N$ enter in these three aspects of
quantum correlations, coherence and coupling strength. 3) the behavior of an
interacting quantum system near its critical point, the effects of quantum and
thermal fluctuations and the conditions under which the system manifests
infrared dimensional reduction. We also discuss how the effective field theory
concept bears on macroscopic quantum phenomena: the running of the coupling
parameters with energy or scale imparts a dynamical-dependent and an
interaction-sensitive definition of `macroscopia'.
| arxiv topic:quant-ph |
arxiv_dataset-27511107.3108 | Excitations of optically driven atomic condensate in a cavity: theory of
photodetection measurements
quant-ph cond-mat.quant-gas
Recent experiments have demonstrated an open system realization of the Dicke
quantum phase transition in the motional degrees of freedom of an optically
driven Bose-Einstein condensate in a cavity. Relevant collective excitations of
this light-matter system are polaritonic in nature, allowing access to the
quantum critical behavior of the Dicke model through light leaking out of the
cavity. This opens the path to using photodetection based quantum optical
techniques to study the dynamics and excitations of this elementary quantum
critical system. We first discuss the photon flux observed at the cavity face
and find that it displays a different scaling law near criticality than that
obtained from the mean field theory for the equivalent closed system. Next, we
study the second order correlation measurements of photons leaking out of the
cavity. Finally, we discuss a modulation technique that directly captures the
softening of polaritonic excitations. Our analysis takes into account the
effect of the finite size of the system which may result in an effective
symmetry breaking term.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-27521107.3208 | New interpretation of the origin of 2DEG states at the surface of
layered topological insulators
cond-mat.mtrl-sci
On the basis of relativistic ab-initio calculations we show that the driving
mechanism of simultaneous emergence of parabolic and M-shaped 2D electron gas
(2DEG) bands at the surface of layered topological insulators as well as
Rashba-splitting of the former states is an expansion of van der Waals (vdW)
spacings caused by intercalation of metal atoms or residual gases. The
expansion of vdW spacings and emergence of the 2DEG states localized in the
(sub)surface region are also accompanied by a relocation of the topological
surface state to the lower quintuple layers, that can explain the absence of
interband scattering found experimentally.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-27531107.3308 | Hyperbolicity of the complex of free factors
math.GR math.GT
We develop the geometry of folding paths in Outer space and, as an
application, prove that the complex of free factors of a free group of finite
rank is hyperbolic.
| arxiv topic:math.GR math.GT |
arxiv_dataset-27541107.3408 | Super-Yang-Mills and M5-branes
hep-th
We uplift 5-dimensional super-Yang-Mills theory to a 6-dimensional gauge
theory with the help of a space-like constant vector $\eta^M$, whose norm
determines the Yang-Mills coupling constant. After the localization of $\eta^M$
the 6D gauge theory acquires Lorentzian invariance as well as scale invariance.
We discuss KK states, instantons and the flux quantization. The 6D theory
admits extended solutions like 1/2 BPS `strings' and monopoles.
| arxiv topic:hep-th |
arxiv_dataset-27551107.3508 | A multivariate "inv" hook formula for forests
math.CO
Bjoerner and Wachs provided two q-generalizations of Knuth's hook formula
counting linear extensions of forests: one involving the major index statistic,
and one involving the inversion number statistic. We prove a multivariate
generalization of their inversion number result, motivated by specializations
related to the modular invariant theory of finite general linear groups.
| arxiv topic:math.CO |
arxiv_dataset-27561107.3608 | Partially traced categories
math.CT
This paper deals with questions relating to Haghverdi and Scott's notion of
partially traced categories. The main result is a representation theorem for
such categories: we prove that every partially traced category can be
faithfully embedded in a totally traced category. Also conversely, every
symmetric monoidal subcategory of a totally traced category is partially
traced, so this characterizes the partially traced categories completely. The
main technique we use is based on Freyd's paracategories, along with a partial
version of Joyal, Street, and Verity's Int-construction.
| arxiv topic:math.CT |
arxiv_dataset-27571107.3708 | Origin of optical second-harmonic generation in spherical gold
nanoparticles: Local surface and nonlocal bulk contributions
physics.optics
The second-harmonic generation of 150 nm spherical gold nanoparticles is
investigated both experimentally and theoretically. We demonstrate that the
interference effects between dipolar and octupolar plasmons can be used as a
fingerprint to discriminate the local surface and non-local bulk contributions
to the second-harmonic generation. By fitting the experimental data with the
electric fields computed with finite-element method (FEM) simulations, the
Rudnick and Stern parameters weighting the relative nonlinear sources
efficiencies are evaluated and the validity of the hydrodynamic model and the
local density approximation approaches are discussed.
| arxiv topic:physics.optics |
arxiv_dataset-27581107.3808 | Height structure of X-ray, EUV and white-light emission in a solar flare
astro-ph.SR
The bulk of solar flare emission originates from very compact sources located
in the lower solar atmosphere and seen in various wavelength ranges: near
optical, UV, EUV, soft and hard X-rays, and gamma-ray emission, yet very few
spatially resolved imaging observations to determine the structure of these
regions exist. We investigate the above-the-photosphere heights of hard X-ray
(HXR), EUV and white-light continuum sources in the low atmosphere and the
corresponding densities at these heights. Simultaneous EUV/continuum images
from SDO and HXR RHESSI images are compared to study a well observed gamma-ray
limb flare. Using RHESSI X-ray visibilities we determine the height of the HXR
sources as a function of energy above the photosphere. Co-aligning AIA/SDO and
HMI/SDO images with RHESSI we infer, for the first time, the heights and
characteristic densities of HXR, EUV and continuum sources in a flaring
footpoint. 35-100 keV HXR sources are found at heights between 1.7 and 0.8 Mm
above the photosphere, below the white-light continuum emission which appears
at heights 1.5-3 Mm, and the peak of EUV emission originating near 3 Mm. The
EUV emission locations are consistent with energy deposition from low energy
electrons of ~12 keV occurring in the top layers of the fully ionized
chromosphere/low corona and not by >20 keV electrons that produce HXR
footpoints in the lower neutral chromosphere. The maximum of white-light
emission appears between the HXR and EUV emission, presumably in the transition
between ionized and neutral atmospheres suggesting free-bound and free-free
continuum emission. We note that the energy deposited by low energy electrons
is sufficient to explain the energetics of optical and UV emissions.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27591107.3908 | Finiteness of $A_n$-equivalence types of gauge groups
math.AT
Let $B$ be a finite CW complex and $G$ a compact connected Lie group. We show
that the number of gauge groups of principal $G$-bundles over $B$ is finite up
to $A_n$-equivalence for $n<\infty$. As an example, we give a lower bound of
the number of $A_n$-equivalence types of gauge groups of principal
$\SU(2)$-bundles over $S^4$.
| arxiv topic:math.AT |
arxiv_dataset-27601107.4008 | The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps
of the Galactic Bulge Fields
astro-ph.SR
We present OGLE-III Photometric Maps of the Galactic bulge fields observed
during the third phase of the OGLE project. This paper describes the last,
concluding set of maps based on OGLE-III data.
The maps contain precise, calibrated VI photometry of about 340 million stars
from 267 fields in the Galactic bulge observed during entire OGLE-III phase
(2002-2009), covering about 92 square degrees in the sky. Precise astrometry of
these objects is also provided.
We briefly discuss the photometry procedures and the quality of the data. We
also present sample data and color-magnitude diagrams of the observed fields.
All photometric data are available to the astronomical community from the
OGLE Internet archive.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27611107.4108 | Tunable quantum spin Hall effect in double quantum wells
cond-mat.mes-hall cond-mat.mtrl-sci
The field of topological insulators (TIs) is rapidly growing. Concerning
possible applications, the search for materials with an easily controllable TI
phase is a key issue. The quantum spin Hall effect, characterized by a single
pair of helical edge modes protected by time-reversal symmetry, has been
demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We
analyze the topological properties of a generically coupled HgTe-based double
QW (DQW) and show how in such a system a TI phase can be driven by an
inter-layer bias voltage, even when the individual layers are non-inverted. We
argue, that this system allows for similar (layer-)pseudospin based physics as
in bilayer graphene but with the crucial absence of a valley degeneracy.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-27621107.4208 | Collective Spin and Charge Excitations in Planar Aromatic Molecules
cond-mat.str-el
Employing high accuracy fixed node diffusion Monte Carlo (DMC) method we
calculated the lowest triplet collective excitation (spin gap), as well as an
upper bound for the singlet excitations (charge gap) in a series of charge
neutral planar non-ladder aromatic compounds. Both excitation energies lie
below the continuum of particle-hole excitation energies obtained from
Hartree-Fock orbitals. Hence they can be interpreted as genuine bound states in
the particle-hole channel. Assuming a resonating valence bond (RVB) ground
state which has been recently suggested for $sp^2$ bonded systems [ M. Marchi,
{\em et. al.}, Phys. Rev. Lett. {\bf 107}, 086807 (2011)], offers a unified
description of both excited states as two-spinon and doublon-holon bound
states. We corroborate our interpretation, by Exact diagonalization study of a
minimal model on finite honeycomb clusters.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-27631107.4308 | Approaching Quantum Criticality in ferromagnetic Ce_2 (Pd_1-x Rh_x)_2 In
alloys
cond-mat.str-el
Low temperature magnetic and thermal (C_m) properties of the ferromagnetic
(FM) alloys Ce_2.15 (Pd_1-x Rh_x)_1.95 In_0.9 were investigated in order to
explore the possibility for tuning a quantum critical point (QCP) by doping Pd
with Rh. As expected, the magnetic transition observed at T = 4.1K in the
parent alloy decreases with increasing Rh concentration. Nevertheless it splits
into two transitions, the upper being antiferromagnetic (AF) whereas the lower
FM. The AF phase boundary extrapolates to T_N = 0 for x_cr ~ 0.65 whereas the
first order FM transition vanishes at x ~ 0.3. The QC character of the T_N => 0
point arises from the divergent T dependence of the tail of C_m/T observed in
the x = 0.5 and 0.55 alloys, and the tendency to saturation of the maximum of
C_m(T_N)/T as observed in exemplary Ce compounds for T_N => 0. Beyond the
critical concentration the unit cell volume deviates from the Vegard's law in
coincidence with a strong increase of the Kondo temperature.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-27641107.4408 | Vanishing Mean Oscillation Spaces Associated with Operators Satisfying
Davies-Gaffney Estimates
math.CA math.FA
Let $(\mathcal{X}, d, \mu)$ be a metric measure space, $L$ a linear operator
which has a bounded $H_\infty$ functional calculus and satisfies the
Davies-Gaffney estimate, $\Phi$ a concave function on $(0,\infty)$ of critical
lower type $p_\Phi^-\in(0,1]$ and $\rho(t)\equiv t^{-1}/\Phi^{-1}(t^{-1})$ for
all $t\in(0,\infty)$. In this paper, the authors introduce the generalized VMO
space ${\mathrm {VMO}}_{\rho,L}({\mathcal X})$ associated with $L$, and
establish its characterization via the tent space. As applications, the authors
show that $({\mathrm {VMO}}_{\rho,L}({\mathcal X}))^*=B_{\Phi,L^*}({\mathcal
X})$, where $L^*$ denotes the adjoint operator of $L$ in $L^2({\mathcal X})$
and $B_{\Phi,L^*}({\mathcal X})$ the Banach completion of the Orlicz-Hardy
space $H_{\Phi,L^*}({\mathcal X})$.
| arxiv topic:math.CA math.FA |
arxiv_dataset-27651107.4508 | A two-dimensional one component plasma and a test charge : polarization
effects and effective potential
cond-mat.stat-mech
We study the effective interactions between a test charge Q and a
one-component plasma, i.e. a complex made up of mobile point particles with
charge q, and a uniform oppositely charged background. The background has the
form of a flat disk, in which the mobile charges can move. The test particle is
approached perpendicularly to the disk, along its axis of symmetry. All
particles interact by a logarithmic potential. The long and short distance
features of the effective potential --the free energy of the system for a given
distance between Q and the disk-- are worked out analytically in detail. They
crucially depend on the sign of Q/q, and on the global charge borne by the
discotic complex, that can vanish. While most results are obtained at the
intermediate coupling Gamma = beta q^2 = 2 (beta being the inverse
temperature), we have also investigated situations with stronger couplings:
Gamma=4 and 6. We have found that at large distances, the sign of the effective
force reflects subtle details of the charge distribution on the disk, whereas
at short distances, polarization effects invariably lead to effective
attractions.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-27661107.4608 | A Search for High Proper Motion T Dwarfs with Pan-STARRS1 + 2MASS + WISE
astro-ph.SR
We have searched ~8200 sq. degs for high proper motion (~0.5-2.7"/year) T
dwarfs by combining first-epoch data from the Pan-STARRS1 (PS1) 3-Pi Survey,
the 2MASS All-Sky Point Source Catalog, and the WISE Preliminary Data Release.
We identified two high proper motion objects with the very red (W1-W2) colors
characteristic of T dwarfs, one being the known T7.5 dwarf GJ 570D. Near-IR
spectroscopy of the other object (PSO J043.5+02 = WISEP J0254+0223) reveals a
spectral type of T8, leading to a photometric distance of 7.2+/-0.7 pc. The
2.56"/yr proper motion of PSO J043.5+02 is the second highest among field T
dwarfs, corresponding to an tangential velocity of 87+/-8 km/s. According to
the Besancon galaxy model, this velocity indicates its galactic membership is
probably in the thin disk, with the thick disk an unlikely possibility. Such
membership is in accord with the near-IR spectrum, which points to a surface
gravity (age) and metallicity typical of the field population. We combine
2MASS, SDSS, WISE, and PS1 astrometry to derive a preliminary parallax of
171+/-45 mas (5.8{+2.0}{-1.2} pc), the first such measurement using PS1 data.
The proximity and brightness of PSO J043+02 will facilitate future
characterization of its atmosphere, variability, multiplicity, distance, and
kinematics. The modest number of candidates from our search suggests that the
immediate (~10 pc) solar neighborhood does not contain a large reservoir of
undiscovered T dwarfs earlier than about T8.
| arxiv topic:astro-ph.SR |
arxiv_dataset-27671107.4708 | On polyhedral approximations of polytopes for learning Bayes nets
math.ST stat.TH
We review three vector encodings of Bayesian network structures. The first
one has recently been applied by Jaakkola 2010, the other two use special
integral vectors formerly introduced, called imsets [Studeny 2005, Studeny
2010]. The central topic is the comparison of outer polyhedral approximations
of the corresponding polytopes. We show how to transform the inequalities
suggested by Jaakkola et al. to the framework of imsets. The result of our
comparison is the observation that the implicit polyhedral approximation of the
standard imset polytope suggested in [Studeny 2011] gives a closer
approximation than the (transformed) explicit polyhedral approximation from
[Jaakkola 2010]. Finally, we confirm a conjecture from [Studeny 2011] that the
above-mentioned implicit polyhedral approximation of the standard imset
polytope is an LP relaxation of the polytope.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-27681107.4808 | Partial coverage of the Broad Line Region of Q1232+082 by an intervening
H2-bearing cloud
astro-ph.CO
We present a detailed analysis of the partial coverage of the Q1232+082 (z_em
=2.57) broad line region by an intervening H_2-bearing cloud at z_abs=2.3377.
Using curve of growth analysis and line profile fitting, we demonstrate that
the H_2-bearing component of the cloud covers the QSO intrinsic continuum
source completely but only part of the Broad Line Region (BLR). We find that
only 48\pm6 % of the C IV BLR emission is covered by the C I absorbing gas. We
observe residual light (~6 %) as well in the bottom of the O I {\lambda}1302
absorption from the cloud, redshifted on top of the QSO Lyman-{\alpha} emission
line. Therefore the extent of the neutral phase of the absorbing cloud is not
large enough to cover all of the background source. The most likely explanation
for this partial coverage is the small size of the intervening cloud, which is
comparable to the BLR size. We estimate the number densities in the cloud:
n_H2~110 cm^{-3} for the H_2-bearing core and n_H ~30 cm^{-3} for the neutral
envelope. Given the column densities, N(H2)=(3.71\pm0.97)\times10^19 cm^{-2}
and N(H I)=(7.94\pm1.6)\times10^20 cm^{-2}, we derive the linear size of the
H_2-bearing core and the neutral envelope along the line of sight to be
l_H2~0.15^{+0.05}_{-0.05} pc and l_HI~8.2^{+6.5}_{-4.1} pc, respectively. We
estimate the size of the C IV BLR by two ways (i) extrapolating size-luminosity
relations derived from reverberation observations and (ii) assuming that the
H_2-bearing core and the BLR are spherical in shape and the results are ~0.26
and ~0.18 pc, respectively. The large size we derive for the extent of the
neutral phase of the absorbing cloud together with a covering factor of ~0.94
of the Lyman-{\alpha} emission means that the Lyman-{\alpha} BLR is probably
fully covered but that the Lyman-{\alpha} emission extends well beyond the
limits of the BLR.
| arxiv topic:astro-ph.CO |
arxiv_dataset-27691107.4908 | Dissipative Optomechanics in a Michelson--Sagnac Interferometer
physics.optics cond-mat.mes-hall physics.ins-det quant-ph
Dissipative optomechanics studies the coupling of the motion of an optical
element to the decay rate of a cavity. We propose and theoretically explore a
realization of this system in the optical domain, using a combined
Michelson--Sagnac interferometer, which enables a strong and tunable
dissipative coupling. Quantum interference in such a setup results in the
suppression of the lower motional sideband, leading to strongly enhanced
cooling in the non-sideband-resolved regime. With state-of-the-art parameters,
ground-state cooling and low-power quantum-limited position transduction are
both possible. The possibility of a strong and tunable dissipative coupling
opens up a new route towards observation of fundamental optomechanical effects
such as ponderomotive squeezing or nonlinear dynamics. Beyond optomechanics,
the method suggested here can be readily transferred to other setups involving
such systems as nonlinear media, atomic ensembles, or single atoms.
| arxiv topic:physics.optics cond-mat.mes-hall physics.ins-det quant-ph |
arxiv_dataset-27701107.5008 | Conical instabilities on paper
cond-mat.soft
The stability of the fundamental defects of an unstretchable flat sheet is
examined. This involves expanding the bending energy to second order in
deformations about the defect. The modes of deformation occur as eigenstates of
a fourth-order linear differential operator. Unstretchability places a global
linear constraint on these modes. Conical defects with a surplus angle exhibit
an infinite number of states. If this angle is below a critical value, these
states possess an n-fold symmetry labeled by an integer, n \geq 2. A nonlinear
stability analysis shows that the 2-fold ground state is stable, whereas
excited states possess 2(n - 2) unstable modes which come in even and odd
pairs.
| arxiv topic:cond-mat.soft |
arxiv_dataset-27711107.5108 | Cooperative Estimation of 3D Target Motion via Networked Visual Motion
Observer
cs.SY math.OC
This paper investigates cooperative estimation of 3D target object motion for
visual sensor networks. In particular, we consider the situation where multiple
smart vision cameras see a group of target objects. The objective here is to
meet two requirements simultaneously: averaging for static objects and tracking
to moving target objects. For this purpose, we present a cooperative estimation
mechanism called networked visual motion observer. We then derive an upper
bound of the ultimate error between the actual average and the estimates
produced by the present networked estimation mechanism. Moreover, we also
analyze the tracking performance of the estimates to moving target objects.
Finally the effectiveness of the networked visual motion observer is
demonstrated through simulation.
| arxiv topic:cs.SY math.OC |
arxiv_dataset-27721107.5208 | Pseudodifferential operators on periodic graphs
math.FA
The main aim of the paper is Fredholm properties of a class of bounded linear
operators acting on weighted Lebesgue spaces on an infinite metric graph
$\Gamma$ which is periodic with respect to the action of the group ${\mathbb
Z}^n$. The operators under consideration are distinguished by their local
behavior: they act as (Fourier) pseudodifferential operators in the class
$OPS^0$ on every open edge of the graph, and they can be represented as a
matrix Mellin pseudodifferential operator on a neighborhood of every vertex of
$\Gamma$. We apply these results to study the Fredholm property of a class of
singular integral operators and of certain locally compact operators on graphs.
| arxiv topic:math.FA |
arxiv_dataset-27731107.5308 | Fractional and noncommutative spacetimes
hep-th gr-qc math-ph math.MP
We establish a mapping between fractional and noncommutative spacetimes in
configuration space. Depending on the scale at which the relation is
considered, there arise two possibilities. For a fractional spacetime with
log-oscillatory measure, the effective measure near the fundamental scale
determining the log-period coincides with the non-rotation-invariant but
cyclicity-preserving measure of \kappa-Minkowski. At scales larger than the
log-period, the fractional measure is averaged and becomes a power-law with
real exponent. This can be also regarded as the cyclicity-inducing measure in a
noncommutative spacetime defined by a certain nonlinear algebra of the
coordinates, which interpolates between \kappa-Minkowski and canonical
spacetime. These results are based upon a braiding formula valid for any
nonlinear algebra which can be mapped onto the Heisenberg algebra.
| arxiv topic:hep-th gr-qc math-ph math.MP |
arxiv_dataset-27741107.5408 | A structured alternative to Prolog with simple compositional semantics
cs.PL
Prolog's very useful expressive power is not captured by traditional logic
programming semantics, due mainly to the cut and goal and clause order. Several
alternative semantics have been put forward, exposing operational details of
the computation state. We propose instead to redesign Prolog around structured
alternatives to the cut and clauses, keeping the expressive power and
computation model but with a compositional denotational semantics over much
simpler states-just variable bindings. This considerably eases reasoning about
programs, by programmers and tools such as a partial evaluator, with safe
unfolding of calls through predicate definitions. An if-then-else across
clauses replaces most uses of the cut, but the cut's full power is achieved by
an until construct. Disjunction, conjunction and until, along with unification,
are the primitive goal types with a compositional semantics yielding sequences
of variable-binding solutions. This extends to programs via the usual technique
of a least fixpoint construction. A simple interpreter for Prolog in the
alternative language, and a definition of until in Prolog, establish the
identical expressive power of the two languages. Many useful control constructs
are derivable from the primitives, and the semantic framework illuminates the
discussion of alternative ones. The formalisation rests on a term language with
variable abstraction as in the {\lambda}-calculus. A clause is an abstraction
on the call arguments, a continuation, and the local variables. It can be
inclusive or exclusive, expressing a local case bound to a continuation by
either a disjunction or an if-then-else. Clauses are open definitions, composed
(and closed) with simple functional application ({\beta}-reduction). This paves
the way for a simple account of flexible module composition mechanisms. Cube, a
concrete language with the exposed principles, has been implemented.
| arxiv topic:cs.PL |
arxiv_dataset-27751107.5508 | Proximity penalty priors for Bayesian mixture models
stat.ME
When using mixture models it may be the case that the modeller has a-priori
beliefs or desires about what the components of the mixture should represent.
For example, if a mixture of normal densities is to be fitted to some data, it
may be desirable for components to focus on capturing differences in location
rather than scale. We introduce a framework called proximity penalty priors
(PPPs) that allows this preference to be made explicit in the prior
information. The approach is scale-free and imposes minimal restrictions on the
posterior; in particular no arbitrary thresholds need to be set. We show the
theoretical validity of the approach, and demonstrate the effects of using PPPs
on posterior distributions with simulated and real data.
| arxiv topic:stat.ME |
arxiv_dataset-27761107.5608 | A subset of Z^n whose non-computability leads to the existence of a
Diophantine equation whose solvability is logically undecidable
math.LO math.NT
For K \subseteq C, let B_n(K)={(x_1,...,x_n) \in K^n: for each y_1,...,y_n
\in K the conjunction (\forall i \in {1,...,n} (x_i=1 => y_i=1)) AND (\forall
i,j,k \in {1,...,n} (x_i+x_j=x_k => y_i+y_j=y_k)) AND (\forall i,j,k \in
{1,...,n} (x_i*x_j=x_k => y_i*y_j=y_k)) implies that x_1=y_1}. We claim that
there is an algorithm that for every computable function f:N->N returns a
positive integer m(f), for which a second algorithm accepts on the input f and
any integer n>=m(f), and returns a tuple (x_1,...,x_n) \in B_n(Z) with
x_1=f(n). We compute an integer tuple (x_1,...,x_{20}) for which the statement
(x_1,...,x_{20}) \in B_{20}(Z) is equivalent to an open Diophantine problem. We
prove that if the set B_n(Z) (B_n(N), B_n(N \setminus {0})) is not computable
for some n, then there exists a Diophantine equation whose solvability in
integers (non-negative integers, positive integers) is logically undecidable.
| arxiv topic:math.LO math.NT |
arxiv_dataset-27771107.5708 | Perfect Codes for Uniform Chains Poset Metrics
cs.IT math.CO math.IT
The class of poset metrics is very large and contains some interesting
families of metrics. A family of metrics, based on posets which are formed from
disjoint chains which have the same size, is examined. A necessary and
sufficient condition, for the existence of perfect single-error-correcting
codes for such poset metrics, is proved.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-27781107.5808 | The formation of CDM haloes I: Collapse thresholds and the ellipsoidal
collapse model
astro-ph.CO
In the excursion set approach to structure formation initially spherical
regions of the linear density field collapse to form haloes of mass $M$ at
redshift $z_{\rm id}$ if their linearly extrapolated density contrast, averaged
on that scale, exceeds some critical threshold, $\delta_{\rm c}(z_{\rm id})$.
The value of $\delta_{\rm c}(z_{\rm id})$ is often calculated from the
spherical or ellipsoidal collapse model, which provide well-defined predictions
given auxiliary properties of the tidal field at a given location. We use two
cosmological simulations of structure growth in a $\Lambda$ cold dark matter
scenario to quantify $\delta_{\rm c}(z_{\rm id})$, its dependence on the
surrounding tidal field, as well as on the shapes of the Lagrangian regions
that collapse to form haloes at $z_{\rm id}$. Our results indicate that the
ellipsoidal collapse model provides an accurate description of the mean
dependence of $\delta_{\rm c}(z_{\rm id})$ on both the strength of the tidal
field and on halo mass. However, for a given $z_{\rm id}$, $\delta_{\rm
c}(z_{\rm id})$ depends strongly on the halo's characteristic formation
redshift: the earlier a halo forms, the higher its initial density contrast.
Surprisingly, the majority of haloes forming $today$ fall below the ellipsoidal
collapse barrier, contradicting the model predictions. We trace the origin of
this effect to the non-spherical shapes of Lagrangian haloes, which arise
naturally due to the asymmetry of the linear tidal field. We show that a
modified collapse model, that accounts for the triaxial shape of protohaloes,
provides a more accurate description of the measured minimum overdensities of
recently collapsed objects.
| arxiv topic:astro-ph.CO |
arxiv_dataset-27791107.5908 | The Regge-plus-resonance model for kaon production on the proton and the
neutron
nucl-th
The Regge-plus-resonance (RPR) framework for kaon photoproduction on the
proton and the neutron is an economical single-channel model with very few
parameters. Not only does the RPR model allow one to extract resonance
information from the data, it has predictive power. As an example we show that
the RPR model makes fair predictions for the $p(e,e'K^{+})\Lambda$ and the
$n(\gamma,K^{+})\Sigma ^{-}$ observables starting from amplitudes optimized for
the reaction $p(\gamma, K ^{+})\Lambda$ and $p(\gamma,K^{+})\Sigma ^{0}$
respectively.
| arxiv topic:nucl-th |
arxiv_dataset-27801107.6008 | SK_1 and Lie Algebras
math.RA math.NT
We investigate the vanishing of the group SK1(A(G)) for the Iwasawa algebra
A(G) of a pro-p p-adic Lie group G (with p different from 2). We reduce this
vanishing to a linear algebra problem for Lie algebras over arbitrary rings,
which we solve for Chevalley orders in split reductive Lie algebras.
| arxiv topic:math.RA math.NT |
arxiv_dataset-27811108.0062 | Realizing arithmetic invariants of hyperbolic 3-manifolds
math.GT
These are mostly expository notes based on the course of lectures on
arithmetic invariants of hyperbolic manifolds given at the workshop associated
with the final "Volume Conference," held at Columbia University, June 2009.
Some new results are included.
| arxiv topic:math.GT |
arxiv_dataset-27821108.0162 | The least common multiple of a sequence of products of linear
polynomials
math.NT
Let $f(x)$ be the product of several linear polynomials with integer
coefficients. In this paper, we obtain the estimate: $\log {\rm lcm}(f(1), ...,
f(n))\sim An$ as $n\rightarrow\infty $, where $A$ is a constant depending on
$f$.
| arxiv topic:math.NT |
arxiv_dataset-27831108.0262 | Groups of Oscillating Intermediate Growth
math.GR
We construct an uncountable family of finitely generated groups of
intermediate growth, with growth functions of new type. These functions can
have large oscillations between lower and upper bounds, both of which come from
a wide class of functions. In particular, we can have growth oscillating
between $e^{n^a}$ and any prescribed function, growing as rapidly as desired.
Our construction is built on top of any of the Grigorchuk groups of
intermediate growth, and is a variation on the limit of permutational wreath
product.
| arxiv topic:math.GR |
arxiv_dataset-27841108.0362 | Propagation of Ultrahigh Energy Nuclei in the Magnetic Field of our
Galaxy
astro-ph.HE
In this work, we present detailed simulations for propagation of ultra-high
energy (UHE) heavy nuclei, with E > 60 EeV, within recent Galactic Magnetic
Field (GMF) models. We investigate the impacts of the regular and turbulent
components of the GMF. We show that with UHE heavy nuclei, there is no
one-to-one correspondence between the arrival directions of cosmic rays (CR)
measured at Earth and the direction of their extragalactic sources. Sources can
have several distorted images on the sky. We compute images of galaxy clusters
and of the supergalactic plane in recent GMF models and show the challenges,
and possibilities, of "UHECR astronomy" with heavy nuclei. Finally, we present
a quantitative study of the impact of the GMF on the (de-)magnification of
source fluxes, due to magnetic lensing effects. We find that for 60 EeV iron
nuclei, sources located in up to about one fifth of the sky would have their
fluxes so strongly demagnified that they would not be detectable at Earth, even
by the next generation of UHECR experiments.
| arxiv topic:astro-ph.HE |
arxiv_dataset-27851108.0462 | All solutions of the Diophantine equation a^6+b^6=c^6+d^6+e^6+f^6+g^6
for a,b,c,d,e,f,g < 250000 found with a distributed Boinc project
math.NT
The above equation is also called as Euler(6,2,5) system. By computational
aspect these systems are very interesting. And we can also apply these methods
to other Diophantine equations. We give a brief history of these systems and
how we searched for these big solutions on Boinc. Our two Boinc projects ran
from April of 2010 to July of 2011.
| arxiv topic:math.NT |
arxiv_dataset-27861108.0562 | Chaperone-assisted translocation of a polymer through a nanopore
cond-mat.soft cond-mat.stat-mech q-bio.BM
Using Langevin dynamics simulations, we investigate the dynamics of
chaperone-assisted translocation of a flexible polymer through a nanopore. We
find that increasing the binding energy $\epsilon$ between the chaperone and
the chain and the chaperone concentration $N_c$ can greatly improve the
translocation probability. Particularly, with increasing the chaperone
concentration a maximum translocation probability is observed for weak binding.
For a fixed chaperone concentration, the histogram of translocation time $\tau$
has a transition from long-tailed distribution to Gaussian distribution with
increasing $\epsilon$. $\tau$ rapidly decreases and then almost saturates with
increasing binding energy for short chain, however, it has a minimum for longer
chains at lower chaperone concentration. We also show that $\tau$ has a minimum
as a function of the chaperone concentration. For different $\epsilon$, a
nonuniversal dependence of $\tau$ on the chain length $N$ is also observed.
These results can be interpreted by characteristic entropic effects for
flexible polymers induced by either crowding effect from high chaperone
concentration or the intersegmental binding for the high binding energy.
| arxiv topic:cond-mat.soft cond-mat.stat-mech q-bio.BM |
arxiv_dataset-27871108.0662 | The Physics of Mergers: Theoretical and Statistical Techniques Applied
to Stellar Mergers in Dense Star Clusters
astro-ph.SR physics.data-an
(abridged) This thesis presents theoretical and statistical techniques
broadly related to systems of dynamically-interacting particles composed of
several different types of populations. They are applied to observations of
dense star clusters (SCs) in order to study gravitational interactions between
stars. We present a new analytic method of quantifying the frequency of
encounters involving single, binary and triple stars. With this technique, we
have shown that dynamical encounters involving triple stars occur commonly in
at least some SCs, and that they are likely to be an important dynamical
channel for stellar mergers to occur. We have also used our techniques to
analyze observational data for a large sample of SCs taken from the ACS Survey
for Globular Clusters. The results of this analysis are as follows: (1) We have
compiled a homogeneous catalogue of stellar populations for every cluster in
our sample, including main-sequence (MS), red giant branch, horizontal branch
and blue straggler (BS) stars. (2) With this catalogue, we have quantified the
effects of the cluster dynamics in determining the relative sizes and spatial
distributions of these stellar populations. (3) These results are particularly
interesting for BSs since they provide compelling evidence that they are
descended from binary stars. (4) Our analysis of the MS populations is
consistent with a remarkably universal initial stellar mass function in old
massive SCs in the Milky Way. This is a new result with important implications
for our understanding of star formation in the early Universe and, more
generally, the history of our Galaxy. Finally, we describe how our techniques
are ideally suited for application to a number of other outstanding puzzles of
modern astrophysics, including chemical reactions in the interstellar medium
and mergers between galaxies in galaxy clusters.
| arxiv topic:astro-ph.SR physics.data-an |
arxiv_dataset-27881108.0762 | X-ray properties of the Sun and some compact objects of our Galaxy
astro-ph.HE
In the Thesis, I study the X-ray properties of the two major stages of the
life cycle of the stars: one is the normal life of a lighter mass star (Sun)
and another is the collapsed state (black hole) of a star (black hole
candidates GRO J1655-40, GX 339-4 and GRBs). I am lucky to be a team member for
developing X-ray solar space instruments RT-2 (S, G and CZT) which observed
both the Sun and Gamma-Ray Bursts (GRBs) from space. A part of my Thesis
contains development of RT-2 instruments, characterization of CZT & CMOS
imaging detectors (used in RT-2/CZT instrument), some observational results of
solar flares and GRBs. My Thesis also contains the detailed timing & spectral
properties of the 2005 outburst of the well known Galactic black hole candidate
GRO J1655-40 and initial rising phase of 2010 outburst of the transient
Galactic stellar mass black hole candidate GX 339-4.
| arxiv topic:astro-ph.HE |
arxiv_dataset-27891108.0862 | Time domain maximum likelihood parameter estimation in LISA Pathfinder
Data Analysis
physics.data-an astro-ph.IM
LISA is the upcoming space-based Gravitational Wave telescope. LISA
Pathfinder, to be launched in the coming years, will prove and verify the
detection principle of the fundamental Doppler link of LISA on a flight
hardware identical in design to that of LISA. LISA Pathfinder will collect a
picture of all noise disturbances possibly affecting LISA, achieving the
unprecedented pureness of geodesic motion necessary for the detection of
gravitational waves. The first steps of both missions will crucially depend on
a very precise calibration of the key system parameters. Moreover, robust
parameters estimation is of fundamental importance in the correct assessment of
the residual force noise, an essential part of the data processing for LISA. In
this paper we present a maximum likelihood parameter estimation technique in
time domain being devised for this calibration and show its proficiency on
simulated data and validation through Monte Carlo realizations of independent
noise runs. We discuss its robustness to non-standard scenarios possibly
arising during the real-life mission, as well as its independence to the
initial guess and non-gaussianities. Furthermore, we apply the same technique
to data produced in mission-like fashion during operational exercises with a
realistic simulator provided by ESA.
| arxiv topic:physics.data-an astro-ph.IM |
arxiv_dataset-27901108.0962 | On On_p
math.RA
Generalizing John Conway's construction of the Field On_2, we give the
"minimal" definitions of addition and multiplication that turn the ordinals
into a Field of characteristic p, for any prime p. We then analyze the
structure of the resulting Field, which we will call On_p.
| arxiv topic:math.RA |
arxiv_dataset-27911108.1062 | Integrality of Stickelberger elements and the equivariant Tamagawa
number conjecture
math.NT
Let $L/K$ be a finite Galois CM-extension of number fields with Galois group
$G$. In an earlier paper, the author has defined a module $SKu(L/K)$ over the
center of the group ring $\mathbb Z[G]$ which coincides with the
Sinnott-Kurihara ideal if $G$ is abelian and, in particular, contains many
Stickelberger elements. It was shown that a certain conjecture on the
integrality of $SKu(L/K)$ implies the minus part of the equivariant Tamagawa
number conjecture at an odd prime $p$ for an infinite class of (non-abelian)
Galois CM-extensions of number fields which are at most tamely ramified above
$p$, provided that Iwasawa's $\mu$-invariant vanishes. Here, we prove a
relevant part of this integrality conjecture which enables us to deduce the
equivariant Tamagawa number conjecture from the vanishing of $\mu$ for the same
class of extensions. As an application we prove the non-abelian Brumer and
Brumer-Stark conjecture outside the $2$-primary part for any monomial Galois
extension of the rationals provided that certain $\mu$-invariants vanish.
| arxiv topic:math.NT |
arxiv_dataset-27921108.1162 | Symmetries of the Similarity Renormalization Group for Nuclear Forces
nucl-th
We analyze the role played by Long Distance Symmetries within the context of
the Similarity Renormalization Group (SRG) approach, which is based on
phase-shift preserving continuous unitary transformations that evolve
hamiltonians with a cutoff on energy differences. We find that there is a SRG
cutoff for which almost perfect fulfillment of Wigner symmetry is found. We
discuss the possible consequences of such finding.
| arxiv topic:nucl-th |
arxiv_dataset-27931108.1262 | 1st International Workshop on Complex Systems in Sports - Proceedings
cs.SI physics.soc-ph
Online proceedings for the first workshop on complex systems in sports; index
pointing to the papers that will be presented and discussed in that workshop.
The papers deal with sports from a complex systems point of view, and include
papers on a network analysis of the performance of the Spanish team in the 2010
world cup and basketball scoring, study of populations of sports fans, try to
select attributes for sports forecasting and finally try to analyze the
physical condition from the perspective of complexity.
| arxiv topic:cs.SI physics.soc-ph |
arxiv_dataset-27941108.1362 | Analysis of the wave propagation properties of a periodic array of rigid
cylinders perpendicular to a finite impedance surface
cond-mat.mtrl-sci
The effect of the presence of a finite impedance surface on the wave
propagation properties of a two-dimensional periodic array of rigid cylinders
with their axes perpendicular to the surface is both numerically and
experimentally analyzed in this work. In this realistic situation both the
incident and the scattered waves interact with these two elements, the surface
and the array. The interaction between the excess attenuation effect, due to
the destructive interference produced by the superposition of the incident wave
and the reflected one by the surface, and the bandgap, due to the periodicity
of the array, is fundamental for the design of devices to control the
transmission of waves based on periodic arrays. The most obvious application is
perhaps the design of Sonic Crystals Noise Barriers. Two different finite
impedance surfaces have been analyzed in the work in order to observe the
dependence of the wave propagation properties on the impedance of the surface.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-27951108.1462 | On a New Multicomputer Interconnection Topology for Massively Parallel
Systems
cs.DC
This paper introduces a new interconnection network topology called Balanced
Varietal Hypercube (BVH), suitable for massively parallel systems. The proposed
topology being a hybrid structure retains almost all the attractive properties
of Balanced Hypercube and Varietal Hypercube. The topology, various parameters,
routing and broadcasting of Balanced Varietal Hypercube are presented. The
performance of the Balanced Varietal Hypercube is compared with other networks.
In terms of diameter, cost and average distance and reliability the proposed
network is found to be better than the Hypercube, Balanced Hypercube and
Varietal Hypercube. Also it is more reliable and cost-effective than Hypercube
and Balanced Hypercube.
| arxiv topic:cs.DC |
arxiv_dataset-27961108.1562 | Confinement and lattice QED electric flux-tubes simulated with ultracold
atoms
quant-ph cond-mat.quant-gas hep-th
We propose a method for simulating 2+1-d compact lattice
quantum-electrodynamics (QED), using ultracold atoms in optical lattices. In
our model local Bose-Einstein condensates' phases correspond to the
electromagnetic vector-potential, and the fluctuations of the local number
operators represent the conjugate electric field. The gauge invariant
Kogut-Susskind Hamiltonian is obtained as an effective low energy theory. The
field is then coupled to external static charges. We show that in the strong
coupling limit this gives rise to 'electric flux-tubes' and to confinement. The
effect can be observed by measuring the local density fluctuations of the BECs.
| arxiv topic:quant-ph cond-mat.quant-gas hep-th |
arxiv_dataset-27971108.1662 | Plasmonic Beam Shaping in the Mid-infrared
physics.optics
Simulation results, fabrication details and measurements are presented for a
one dimensional aperture and grating array for the purpose of plasmonic beam
shaping of the {\lambda}=3.99{\mu}m output of an optically pumped semiconductor
laser.
| arxiv topic:physics.optics |
arxiv_dataset-27981108.1762 | Randomized Strategyproof Mechanisms for Facility Location and the
Mini-Sum-of-Squares Objective
cs.GT
We consider the problem of locating a public facility on a line, where a set
of $n$ strategic agents report their \emph{locations} and a mechanism
determines, either deterministically or randomly, the location of the facility.
Game theoretic perspectives of the facility location problem advanced in two
main directions. The first direction is concerned with the characterization of
\emph{strategyproof} (SP) mechanisms; i.e., mechanisms that induce truthful
reporting as a dominant strategy; and the second direction quantifies how well
various objective functions can be approximated when restricted to SP
mechanisms. The current paper provides contributions in both directions. First,
we construct a parameterized randomized SP mechanism, and show that all of the
previously proposed deterministic and randomized SP mechanisms for the current
settings can be formalized as special cases of this mechanism. Second, we give
tight results for the approximation ratio of SP mechanisms with respect to the
objective of minimizing the sum of squares of distances to the agents
(\emph{miniSOS}). Holzman \cite{Holzman1990} provided an axiomatic foundation
for this function, showing that it is the unique function that satisfies
unanimity, continuity and invariance. We devise a randomized mechanism that
gives a 1.5-approximation for the miniSOS function, and show that no other
randomized SP mechanism can provide a better approximation. This mechanism
chooses the average location with probability 1/2 and a \emph{random dictator}
with probability 1/2. For deterministic mechanisms, we show that the median
mechanism provides a 2-approximation, and this is tight. Together, our study
provides fundamental understanding of the miniSOS objective function and makes
a step toward the characterization of randomized SP facility location
mechanisms.
| arxiv topic:cs.GT |
arxiv_dataset-27991108.1862 | Input-output Conformance Testing for Channel-based Service Connectors
cs.SE
Service-based systems are software systems composed of autonomous components
or services provided by different vendors, deployed on remote machines and
accessible through the web. One of the challenges of modern software
engineering is to ensure that such a system behaves as intended by its
designer. The Reo coordination language is an extensible notation for formal
modeling and execution of service compositions. Services that have no prior
knowledge about each other communicate through advanced channel connectors
which guarantee that each participant, service or client, receives the right
data at the right time. Each channel is a binary relation that imposes
synchronization and data constraints on input and output messages. Furthermore,
channels are composed together to realize arbitrarily complex behavioral
protocols. During this process, a designer may introduce errors into the
connector model or the code for their execution, and thus affect the behavior
of a composed service. In this paper, we present an approach for model-based
testing of coordination protocols designed in Reo. Our approach is based on the
input-output conformance (ioco) testing theory and exploits the mapping of
automata-based semantic models for Reo to equivalent process algebra
specifications.
| arxiv topic:cs.SE |
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