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arxiv_dataset-29001109.5632 | Semi-algebraic horizontal subvarieties of Calabi-Yau type
math.AG
We study horizontal subvarieties $Z$ of a Griffiths period domain $\mathbb
D$. If $Z$ is defined by algebraic equations, and if $Z$ is also invariant
under a large discrete subgroup in an appropriate sense, we prove that $Z$ is a
Hermitian symmetric domain $\mathcal D$, embedded via a totally geodesic
embedding in $\mathbb D$. Next we discuss the case when $Z$ is in addition of
Calabi-Yau type. We classify the possible VHS of Calabi-Yau type parametrized
by Hermitian symmetric domains $\mathcal D$ and show that they are essentially
those found by Gross and Sheng-Zuo, up to taking factors of symmetric powers
and certain shift operations. In the weight three case, we explicitly describe
the embedding $Z\hookrightarrow \mathbb D$ from the perspective of Griffiths
transversality and relate this description to the Harish-Chandra realization of
$\mathcal D$ and to the Kor\'anyi-Wolf tube domain description. There are
further connections to homogeneous Legendrian varieties and the four Severi
varieties of Zak.
| arxiv topic:math.AG |
arxiv_dataset-29011109.5732 | Representing Conversations for Scalable Overhearing
cs.AI
Open distributed multi-agent systems are gaining interest in the academic
community and in industry. In such open settings, agents are often coordinated
using standardized agent conversation protocols. The representation of such
protocols (for analysis, validation, monitoring, etc) is an important aspect of
multi-agent applications. Recently, Petri nets have been shown to be an
interesting approach to such representation, and radically different approaches
using Petri nets have been proposed. However, their relative strengths and
weaknesses have not been examined. Moreover, their scalability and suitability
for different tasks have not been addressed. This paper addresses both these
challenges. First, we analyze existing Petri net representations in terms of
their scalability and appropriateness for overhearing, an important task in
monitoring open multi-agent systems. Then, building on the insights gained, we
introduce a novel representation using Colored Petri nets that explicitly
represent legal joint conversation states and messages. This representation
approach offers significant improvements in scalability and is particularly
suitable for overhearing. Furthermore, we show that this new representation
offers a comprehensive coverage of all conversation features of FIPA
conversation standards. We also present a procedure for transforming AUML
conversation protocol diagrams (a standard human-readable representation), to
our Colored Petri net representation.
| arxiv topic:cs.AI |
arxiv_dataset-29021109.5832 | Symmetry-Breaking Phase Transition without Peierls Mechanism in
Conducting Monoatomic Chains
cond-mat.str-el
The one-dimensional (1D) model system Au/Ge(001), consisting of linear chains
of single atoms on a surface, is scrutinized for lattice instabilities
predicted in the Peierls paradigm. By scanning tunneling microscopy and
electron diffraction we reveal a second-order phase transition at 585 K. It
leads to charge ordering with transversal and vertical displacements and
complex interchain correlations. However, the structural phase transition is
not accompanied by the electronic signatures of a charge density wave, thus
precluding a Peierls instability as origin. Instead, this symmetry-breaking
transition exhibits three-dimensional critical behavior. This reflects a
dichotomy between the decoupled 1D electron system and the structural elements
that interact via the substrate. Such substrate-mediated coupling between the
wires thus appears to have been underestimated also in related chain systems.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-29031109.5932 | An Observational Overview of Solar Flares
astro-ph.SR
We present an overview of solar flares and associated phenomena, drawing upon
a wide range of observational data primarily from the RHESSI era. Following an
introductory discussion and overview of the status of observational
capabilities, the article is split into topical sections which deal with
different areas of flare phenomena (footpoints and ribbons, coronal sources,
relationship to coronal mass ejections) and their interconnections. We also
discuss flare soft X-ray spectroscopy and the energetics of the process. The
emphasis is to describe the observations from multiple points of view, while
bearing in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is far from
complete, so we conclude with a brief discussion of models, and a list of
missing but important observations.
| arxiv topic:astro-ph.SR |
arxiv_dataset-29041109.6032 | Pulsed Radio Emission from the Fermi-LAT Pulsar J1732-3131: Search and A
Possible Detection at 34.5 MHz
astro-ph.GA astro-ph.HE
We report our search for and a possible detection of periodic radio pulses at
34.5 MHz from the Fermi-LAT pulsar J1732-3131. The candidate detection has been
possible in only one of the many sessions of observations made with the
low-frequency array at Gauribidanur, India, when the otherwise radio weak
pulsar may have apparently brightened many folds. The candidate dispersion
measure along the sight-line, based on the broad periodic profiles from about
20 minutes of data, is estimated to be 15.44 +/-0.32 pc/cc. We present the
details of our periodic & single-pulse search, and discuss the results and
their implications relevant to both, the pulsar and the intervening medium.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-29051109.6132 | Long Period Variables in the Large Magellanic Cloud from the EROS-2
survey
astro-ph.SR
Context. The EROS-2 survey has produced a database of millions of time series
from stars monitored for more than six years, allowing to classify some of
their sources into different variable star types. Among these, Long Period
Variables (LPVs), known to follow sequences in the period-luminosity diagram,
include long secondary period variables whose variability origin is still a
matter of debate.
Aims.We use the 856 864 variable stars available from the Large Magellanic
Cloud (LMC) in the EROS-2 database to detect, classify and characterize LPVs.
Methods. Our method to extract LPVs is based on the statistical Abbe test. It
investigates the regularity of the light curve with respect to the survey
duration in order to extract candidates with long-term variability. The period
search is done by Deeming, Lomb-Scargle and generalized Lomb-Scargle methods,
combined with Fourier series fit. Color-magnitude, period-magnitude and
period-amplitude diagrams are used to characterize our candidates.
Results. We present a catalog of 43 551 LPV candidates for the Large
Magellanic Cloud. For each of them, we provide up to five periods, mean
magnitude in EROS-2, 2MASS and Spitzer bands, BE-RE color, RE amplitude and
spectral type.We use infrared data to make the distinction between RGB, O-rich,
C-rich and extreme AGB stars. Properties of our LPV candidates are investigated
by analyzing period-luminosity and period-amplitude diagrams.
| arxiv topic:astro-ph.SR |
arxiv_dataset-29061109.6232 | Higgs Boson masses and B-Physics Constraints in Non-Minimal Flavor
Violating SUSY scenarios
hep-ph
We present one-loop corrections to the Higgs boson masses in the MSSM with
Non-Minimal Flavor Violation. The flavor violation is generated from the
hypothesis of general flavor mixing in the squark mass matrices, and these are
parameterized by a complete set of delta^XY_ij (X, Y = L,R; i; j = t, c, u or
b, s, d). We calculate the corrections to the Higgs masses in terms of these
delta^XY_ij taking into account all relevant restrictions from B-physics data.
This includes constraints from BR(B -> Xs gamma), BR(Bs -> mu+ mu-) and delta
M_B_s . After taking into account these constraints we find sizable corrections
to the Higgs boson masses, in the case of the lightest MSSM Higgs boson mass
exceeding tens of GeV. These corrections are found mainly for the low tan beta
case. In the case of a Higgs boson mass measurement these corrections might be
used to set further constraints on delta^XY_ij.
| arxiv topic:hep-ph |
arxiv_dataset-29071109.6332 | The Nuclear Spin Environment in Lateral GaAs Spin Valves
cond-mat.mes-hall
The spin degree of freedom in solids offers opportunities beyond charge-based
electronics and is actively investigated for both spintronics and quantum
computation. However, the interplay of these spins with their native
environment can give rise to detrimental effects such as spin relaxation and
decoherence. Here, we use an all-electrical, lateral GaAs spin valve to
manipulate and investigate the inherent nuclear spin system. Hanle satellites
are used to determine the nuclear spin relaxation rates for the previously
unexplored temperature range down to 100 mK, giving T1 times as long as 3
hours. Despite metallic temperature dependence of resistivity, the observed
relaxation rates show a sub-linear temperature dependence. This contrasts the
Korringa relaxation mechanism observed in metals but is not inconsistent with
hyperfine-mediated relaxation in a disordered, interacting conductor not far
from the metal-insulator transition. We discuss possible relaxation mechanisms
and further investigate inhomogeneities in the nuclear spin polarization.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-29081109.6432 | Affine Sieve
math.NT math.GR
We establish the main saturation conjecture in [BGS10] connected with
executing a Brun sieve in the setting of an orbit of a group of affine linear
transformations. This is carried out under the condition that the Zariski
closure of the group is Levi-semisimple. It is likely that this condition is
also necessary for such saturation to hold.
| arxiv topic:math.NT math.GR |
arxiv_dataset-29091109.6532 | Computing Early-time Dynamics in Heavy Ion Collisions: Status, Problems
and Prospects
hep-ph hep-th nucl-th
We discuss some recent developments towards a quantitative understanding of
the production and early-time evolution of bulk quark-gluon matter in
ultrarelativistic heavy ion collisions.
| arxiv topic:hep-ph hep-th nucl-th |
arxiv_dataset-29101109.6632 | Simulation of Reactors for Antineutrino Experiments Using DRAGON
nucl-ex hep-ex
From the discovery of the neutrino to the precision neutrino oscillation
measurements in KamLAND, nuclear reactors have proven to be an important source
of antineutrinos. As their power and our knowledge of neutrino physics has
increased, more sensitive measurements have become possible. The next
generation of reactor antineutrino experiments require more detailed
simulations of the reactor core. Many of the reactor simulation codes are
proprietary which makes detailed studies difficult. Here we present the results
of the open source DRAGON code and compare it to other industry standards for
reactor modeling. We use published data from the Takahama reactor to determine
the quality of the simulations. The propagation of the uncertainty to the
antineutrino flux is also discussed.
| arxiv topic:nucl-ex hep-ex |
arxiv_dataset-29111109.6732 | Dynamical locality of the free scalar field
math-ph gr-qc math.MP
Dynamical locality is a condition on a locally covariant physical theory,
asserting that kinematic and dynamical notions of local physics agree. This
condition was introduced in [arXiv:1106.4785], where it was shown to be closely
related to the question of what it means for a theory to describe the same
physics on different spacetimes. In this paper, we consider in detail the
example of the free minimally coupled Klein--Gordon field, both as a classical
and quantum theory (using both the Weyl algebra and a smeared field approach).
It is shown that the massive theory obeys dynamical locality, both classically
and in quantum field theory, in all spacetime dimensions $n\ge 2$ and allowing
for spacetimes with finitely many connected components. In contrast, the
massless theory is shown to violate dynamical locality in any spacetime
dimension, in both classical and quantum theory, owing to a rigid gauge
symmetry. Taking this into account (equivalently, working with the massless
current) dynamical locality is restored in all dimensions $n\ge 2$ on connected
spacetimes, and in all dimensions $n\ge 3$ if disconnected spacetimes are
permitted. The results on the quantized theories are obtained using general
results giving conditions under which dynamically local classical symplectic
theories have dynamically local quantizations.
| arxiv topic:math-ph gr-qc math.MP |
arxiv_dataset-29121109.6832 | Visser's Massive Gravity Bimetric Theory Revisited
gr-qc astro-ph.CO
A massive gravity theory was proposed by Visser in the late nineties. This
theory, based on a backgroung metric $b_{\alpha \beta}$ and on an usual
dynamical metric $g_{\alpha \beta}$ has the advantage of being free of ghosts
as well as discontinuities present in other massive theories proposed in the
past. In the present investigation, the equations of Visser's theory are
revisited with a particular care on the related conservation laws.\ It will be
shown that a multiplicative factor is missing in the graviton tensor originally
derived by Visser, which has no incidence on the weak field approach but
becomes important in the strong field regime when, for instance, cosmological
applications are considered. In this case, contrary to some previous claims
found in the literature, we conclude that a non-static background metric is
required in order to obtain a solution able to mimic the $\Lambda$CDM
cosmology.
| arxiv topic:gr-qc astro-ph.CO |
arxiv_dataset-29131109.6932 | An ultrafast image recovery and recognition system implemented with
nanomagnets possessing biaxial magnetocrystalline anisotropy
cond-mat.mes-hall
A circular magnetic disk with biaxial magnetocrystalline anisotropy has four
stable magnetization states which can be used to encode a pixel's shade in a
black/gray/white image. By solving the Landau-Lifshitz- Gilbert equation, we
show that if moderate noise deflects the magnetization slightly from a stable
state, it always returns to the original state, thereby automatically
de-noising the corrupted image. The same system can compare a noisy input image
with a stored image and make a matching decision using magneto-tunneling
junctions. These tasks are executed at ultrahigh speeds (~2 ns for a
512\times512 pixel image).
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-29141110.0094 | Colliding plane wave solution in F(R)=R^{N} gravity
gr-qc
We identify a region of F(R)=R^{N} gravity without external sources which is
isometric to the spacetime of colliding plane waves (CPW). From the derived
curvature sources, N (N>1) measures the strength (i.e. the charge) of the
source. The analogy renders construction and collision of plane waves in
F(R)=R^{N} gravity possible, as in the Einstein-Maxwell (EM) theory, simply
because R=0. A plane wave in this type of gravity is equivalent to a Weyl
curvature plus an electromagnetic energy-momentum-like term (i.e. 'source
without source'). For N=1 we recover naturally the plane waves (and their
collision) in Einstein's theory. Our aim is to find the effect of an expanding
universe by virtue of F(R)=R^{N} on the colliding gravitational plane waves of
Einstein.
| arxiv topic:gr-qc |
arxiv_dataset-29151110.0194 | Rate-Dependent Analysis of the Asymptotic Behavior of Channel
Polarization
cs.IT math.IT
For a binary-input memoryless symmetric channel $W$, we consider the
asymptotic behavior of the polarization process in the large block-length
regime when transmission takes place over $W$. In particular, we study the
asymptotics of the cumulative distribution $\mathbb{P}(Z_n \leq z)$, where
$\{Z_n\}$ is the Bhattacharyya process defined from $W$, and its dependence on
the rate of transmission. On the basis of this result, we characterize the
asymptotic behavior, as well as its dependence on the rate, of the block error
probability of polar codes using the successive cancellation decoder. This
refines the original bounds by Ar{\i}kan and Telatar. Our results apply to
general polar codes based on $\ell \times \ell$ kernel matrices.
We also provide lower bounds on the block error probability of polar codes
using the MAP decoder. The MAP lower bound and the successive cancellation
upper bound coincide when $\ell=2$, but there is a gap for $\ell>2$.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-29161110.0294 | Effects of equation of state on nuclear suppression and the initial
entropy density of quark gluon plasma
nucl-th hep-ph nucl-ex
We study the effects of the equation of state on the nuclear suppression of
heavy flavours in quark gluon plasma and estimate the initial entropy density
of the system produced at the highest RHIC energy. For this purpose we have
used the experimental data on the charged particle multiplicity and the nuclear
suppression of single electron spectra originating from the semi-leptonic
decays of open charm and beauty mesons. We have used inputs from lattice QCD to
minimize the model dependence of the results. We obtain the value of the
initial entropy density which varies from 20 to 59 /fm$^3$ depending on the
value of the velocity of sound that one uses for the analysis. Our
investigation leads to a conservative value of the initial entropy density
$\sim 20/$fm$^3$ with corresponding initial temperature $\sim 210$ MeV well
above the value of the transition temperature predicted by lattice QCD.
| arxiv topic:nucl-th hep-ph nucl-ex |
arxiv_dataset-29171110.0394 | Interplay of Aharonov-Bohm, chirality, and aspect ratio effects in the
axial conductance of a nanotube
cond-mat.mes-hall quant-ph
A magnetic flux applied along the axis of a nanotube can counteract the
effect of the tube chirality and dramatically affect its conductance, leading
to a way to determine the chirality of a nanotube. The effect of the applied
flux is strongest in the long tube limit where the conductance is (i) either a
sequence of sharp $4e^{2}/h$ height peaks located at integer (in units of the
flux quantum) values of the flux (for an armchair tube) or (ii) a periodic
sequence of pairs of $2e^{2}/h$ height peaks for a chiral tube, with the
spacing determined by the chirality. In the short tube limit the conductance
takes on the value that gives the universal conductivity of an undoped graphene
sheet, with a small amplitude modulation periodic in the flux.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-29181110.0494 | Pairing instabilities in quasi-two-dimensional Fermi gases
cond-mat.quant-gas
We study non-equilibrium dynamics of ultracold two-component Fermi gases in
low-dimensional geometries after the interactions are quenched from weakly
interacting to strongly interacting regime. We develop a T-matrix formalism
that takes into account the interplay between Pauli blocking and tight
confinement in low-dimensional geometries. We employ our formalism to study the
formation of molecules in quasi-two-dimensional Fermi gases near Feshbach
resonance and show that the rate at which molecules form depends strongly on
the transverse confinement. Furthermore, Pauli blocking gives rise to a sizable
correction to the binding energy of molecules.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-29191110.0594 | Practical Wireless Network Coding and Decoding Methods for Multiple
Unicast Transmissions
cs.IT math.IT
We propose a simple yet effective wireless network coding and decoding
technique. It utilizes spatial diversity through cooperation between nodes
which carry out distributed encoding operations dictated by generator matrices
of linear block codes. For this purpose, we make use of greedy codes over the
binary field and show that desired diversity orders can be flexibly assigned to
nodes in a multiple unicast network, contrary to the previous findings in the
literature. Furthermore, we present the optimal detection rule for the given
model that accounts for intermediate node errors and suggest a network decoder
using the sum-product algorithm. The proposed sum-product detector exhibits
near optimal performance.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-29201110.0694 | Search for CP Violation in D Meson Decays to phi pi+
hep-ex
We search for CP violation in Cabibbo-suppressed charged D meson decays by
measuring the difference between the CP violating asymmetries for the
Cabibbo-suppressed decays D+ -> K+K-pi+ and the Cabibbo-favored decays Ds ->
K+K-pi+ in the K+K- mass region of the phi resonance. Using 955/fb of data
collected with the Belle detector we obtain A_CP(D+ -> phi pi+) = (+0.51 +-
0.28 +- 0.05)%. The measurement improves the sensitivity of previous searches
by more than a factor of five. We find no evidence for direct CP violation.
| arxiv topic:hep-ex |
arxiv_dataset-29211110.0794 | Penalty Methods for the Hyperbolic System Modelling the Wall-Plasma
Interaction in a Tokamak
math.NA
The penalization method is used to take account of obstacles in a tokamak,
such as the limiter. We study a non linear hyperbolic system modelling the
plasma transport in the area close to the wall. A penalization which cuts the
transport term of the momentum is studied. We show numerically that this
penalization creates a Dirac measure at the plasma-limiter interface which
prevents us from defining the transport term in the usual sense. Hence, a new
penalty method is proposed for this hyperbolic system and numerical tests
reveal an optimal convergence rate without any spurious boundary layer.
| arxiv topic:math.NA |
arxiv_dataset-29221110.0894 | Effect of cation size variance on spin and orbital order in
Eu$_{1-x}$(La$_{0.254}$Y$_{0.746}$)$_{x}$VO$_3$
cond-mat.str-el
We have investigated the $R$-ion ($R$ = rare earth or Y) size variance effect
on spin/orbital order in Eu$_{1-x}$(La$_{0.254}$Y$_{0.746}$)$_{x}$VO$_3$. The
size variance disturbs one-dimensional orbital correlation in $C$-type
spin/$G$-type orbital ordered states and suppresses this spin/orbital order. In
contrast, it stabilizes the other spin/orbital order. The results of neutron
and resonant X-ray scattering denote that in the other ordered phase, the
spin/orbital patterns are $G$-type/$C$-type, respectively.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-29231110.0994 | A Spectral Sequence Connecting Continuous With Locally Continuous Group
Cohomology
math.GN
We present a spectral sequence connecting the continuous and 'locally
continuous' group cohomologies for topological groups. As an application it is
shown that for contractible topological groups these cohomology concepts
coincide. Similar results for k-groups and smooth cochains on Lie groups are
also obtained.
| arxiv topic:math.GN |
arxiv_dataset-29241110.1094 | Jet substructure in ATLAS
hep-ex
Measurements are presented of the jet invariant mass and substructure in
proton-proton collisions at sqrt{s} = 7 TeV with the ATLAS detector using an
integrated luminosity of 37 pb-1. These results exercise the tools for
distinguishing the signatures of new boosted massive particles in the hadronic
final state. Two "fat" jet algorithms are used, along with the filtering jet
grooming technique that was pioneered in ATLAS. New jet substructure
observables are compared for the first time to data at the LHC. Finally, a
sample of candidate boosted top quark events collected in the 2010 data is
analyzed in detail for the jet substructure properties of hadronic "top-jets"
in the final state. These measurements demonstrate not only our excellent
understanding of QCD in a new energy regime but open the path to using complex
jet substructure observables in the search for new physics.
| arxiv topic:hep-ex |
arxiv_dataset-29251110.1194 | Efficient Encoding of Watermark Numbers as Reducible Permutation Graphs
cs.DS
In a software watermarking environment, several graph theoretic watermark
methods use numbers as watermark values, where some of these methods encode the
watermark numbers as graph structures. In this paper we extended the class of
error correcting graphs by proposing an efficient and easily implemented codec
system for encoding watermark numbers as reducible permutation flow-graphs.
More precisely, we first present an efficient algorithm which encodes a
watermark number $w$ as self-inverting permutation $\pi^*$ and, then, an
algorithm which encodes the self-inverting permutation $\pi^*$ as a reducible
permutation flow-graph $F[\pi^*]$ by exploiting domination relations on the
elements of $\pi^*$ and using an efficient DAG representation of $\pi^*$. The
whole encoding process takes O(n) time and space, where $n$ is the binary size
of the number $w$ or, equivalently, the number of elements of the permutation
$\pi^*$. We also propose efficient decoding algorithms which extract the number
$w$ from the reducible permutation flow-graph $F[\pi^*]$ within the same time
and space complexity. The two main components of our proposed codec system,
i.e., the self-inverting permutation $\pi^*$ and the reducible permutation
graph $F[\pi^*]$, incorporate important structural properties which make our
system resilient to attacks.
| arxiv topic:cs.DS |
arxiv_dataset-29261110.1294 | Steady streaming in a channel with permeable walls
physics.flu-dyn math-ph math.MP
We study steady streaming in a channel between two parallel permeable walls
induced by oscillating (in time) blowing/suction at the walls. We obtain an
asymptotic expansion of the solution of the Navier-Stokes equations in the
limit when the amplitude of the normal displacements of fluid particles near
the walls is much smaller that both the width of the channel and the thickness
of the Stokes layer. It is demonstrated that the magnitude of the steady
streaming is much bigger than the corresponding quantity in the case of the
steady streaming produced by vibrations of impermeable boundaries.
| arxiv topic:physics.flu-dyn math-ph math.MP |
arxiv_dataset-29271110.1394 | Learning Sentence-internal Temporal Relations
cs.CL cs.AI
In this paper we propose a data intensive approach for inferring
sentence-internal temporal relations. Temporal inference is relevant for
practical NLP applications which either extract or synthesize temporal
information (e.g., summarisation, question answering). Our method bypasses the
need for manual coding by exploiting the presence of markers like after", which
overtly signal a temporal relation. We first show that models trained on main
and subordinate clauses connected with a temporal marker achieve good
performance on a pseudo-disambiguation task simulating temporal inference
(during testing the temporal marker is treated as unseen and the models must
select the right marker from a set of possible candidates). Secondly, we assess
whether the proposed approach holds promise for the semi-automatic creation of
temporal annotations. Specifically, we use a model trained on noisy and
approximate data (i.e., main and subordinate clauses) to predict
intra-sentential relations present in TimeBank, a corpus annotated rich
temporal information. Our experiments compare and contrast several
probabilistic models differing in their feature space, linguistic assumptions
and data requirements. We evaluate performance against gold standard corpora
and also against human subjects.
| arxiv topic:cs.CL cs.AI |
arxiv_dataset-29281110.1494 | Counterflow in Evacuations
physics.soc-ph cs.MA
It is shown in this work that the average individual egress time and other
performance indicators for egress of people from a building can be improved
under certain circumstances if counterflow occurs. The circumstances include
widely varying walking speeds and two differently far located exits with
different capacity. The result is achieved both with a paper and pencil
calculation as well as with a micro simulation of an example scenario. As the
difficulty of exit signage with counterflow remains one cannot conclude from
the result that an emergency evacuation procedure with counterflow would really
be the better variant.
| arxiv topic:physics.soc-ph cs.MA |
arxiv_dataset-29291110.1594 | Testing Inflation with Dark Matter Halos
astro-ph.CO
Cosmic inflation provides a mechanism for generating the early density
perturbations that seeded the large-scale structures we see today. Primordial
non-Gaussianity is among the most promising of few observational tests of
physics at this epoch. At present non-Gaussianity is best constrained by the
cosmic microwave background, but in the near term large-scale structure data
may be competitive so long as the effects of primordial non-Gaussianity can be
modeled through the non-linear process of structure formation. We discuss
recent work modeling effects of a few types of primordial non-Gaussianity on
the large-scale halo clustering and the halo mass function. More specifically,
we compare analytic and N-body results for two variants of the curvaton model
of inflation: (i) a "tauNL" scenario in which the curvaton and inflaton
contribute equally to the primordial curvature perturbation and (ii) a "gNL"
model where the usual quadratic fNL term in the potential cancels, but a large
cubic term remains.
| arxiv topic:astro-ph.CO |
arxiv_dataset-29301110.1694 | Shrinking the Quadratic Estimator
astro-ph.IM astro-ph.CO stat.AP
We study a regression characterization for the quadratic estimator of weak
lensing, developed by Hu and Okamoto (2001,2002), for cosmic microwave
background observations. This characterization motivates a modification of the
quadratic estimator by an adaptive Wiener filter which uses the robust Bayesian
techniques described in Strawderman (1971) and Berger (1980). This technique
requires the user to propose a fiducial model for the spectral density of the
unknown lensing potential but the resulting estimator is developed to be robust
to misspecification of this model. The role of the fiducial spectral density is
to give the estimator superior statistical performance in a "neighborhood of
the fiducial model" while controlling the statistical errors when the fiducial
spectral density is drastically wrong. Our estimate also highlights some
advantages provided by a Bayesian analysis of the quadratic estimator.
| arxiv topic:astro-ph.IM astro-ph.CO stat.AP |
arxiv_dataset-29311110.1794 | Radio observations of the first three-month Fermi-AGN at 4.8 GHz
astro-ph.CO hep-ph
Using the Urumqi 25m radio telescope, sources from the first three-month
Fermi-LAT detected AGN catalog with declination >0 were observed in 2009 at 4.8
GHz. The radio flux density appears to correlate with the gamma-ray intensity.
Intra-day variability (IDV) observations were performed in March, April and May
in 2009 for selected 42 gamma-ray bright blazars, and 60% of them show evident
flux variability at 4.8 GHz during the IDV observations, the IDV detection rate
is higher than that in previous flat-spectrum AGN samples. The IDV appears more
often in the VLBI-core dominant blazars, and the non-IDV blazars show
relatively `steeper' spectral indices than the IDV blazars. Pronounced
inter-month variability has been found in two BL Lac objects: J0112+2244 and
J0238+1636.
| arxiv topic:astro-ph.CO hep-ph |
arxiv_dataset-29321110.1894 | On the Efficiency of Influence-and-Exploit Strategies for Revenue
Maximization under Positive Externalities
cs.DS cs.CC cs.SI
We study the problem of revenue maximization in the marketing model for
social networks introduced by (Hartline, Mirrokni, Sundararajan, WWW '08). We
restrict our attention to the Uniform Additive Model and mostly focus on
Influence-and-Exploit (IE) marketing strategies. We obtain a comprehensive
collection of results on the efficiency and the approximability of IE
strategies, which also imply a significant improvement on the best known
approximation ratios for revenue maximization. Specifically, we show that in
the Uniform Additive Model, both computing the optimal marketing strategy and
computing the best IE strategy are $\NP$-hard for undirected social networks.
We observe that allowing IE strategies to offer prices smaller than the myopic
price in the exploit step leads to a measurable improvement on their
performance. Thus, we show that the best IE strategy approximates the maximum
revenue within a factor of 0.911 for undirected and of roughly 0.553 for
directed networks. Moreover, we present a natural generalization of IE
strategies, with more than two pricing classes, and show that they approximate
the maximum revenue within a factor of roughly 0.7 for undirected and of
roughly 0.35 for directed networks. Utilizing a connection between good IE
strategies and large cuts in the underlying social network, we obtain
polynomial-time algorithms that approximate the revenue of the best IE strategy
within a factor of roughly 0.9. Hence, we significantly improve on the best
known approximation ratio for revenue maximization to 0.8229 for undirected and
to 0.5011 for directed networks (from 2/3 and 1/3, respectively, by Hartline et
al.).
| arxiv topic:cs.DS cs.CC cs.SI |
arxiv_dataset-29331110.1994 | Measuring the pulse of GRB 090618: A Simultaneous Spectral and Timing
Analysis of the Prompt Emission
astro-ph.HE
We develop a new method for simultaneous timing and spectral studies of Gamma
Ray Burst (GRB) prompt emission and apply it to make a pulse-wise description
of the prompt emission of GRB 090618, the brightest GRB detected in the Fermi
era. We exploit the large area (and sensitivity) of Swift/BAT and the wide band
width of Fermi/GBM to derive the parameters for a complete spectral and timing
description of the individual pulses of this GRB, based on the various
empirical relations suggested in the literature. We demonstrate that this
empirical model correctly describes the other observed properties of the burst
like the variation of the lag with energy and the pulse width with energy. The
measurements also show an indication of an increase in pulse width as a
function of energy at low energies for some of the pulses, which is naturally
explained as an off-shoot of some particular combination of the model
parameters. We argue that these model parameters, particularly the peak energy
at the beginning of the pulse, are the natural choices to be used for
correlation with luminosity. The implications of these results for the use of
GRBs as standard candles are briefly described.
| arxiv topic:astro-ph.HE |
arxiv_dataset-29341110.2094 | Elimination of the spin supplementary condition in the effective field
theory approach to the post-Newtonian approximation
gr-qc
The present paper addresses open questions regarding the handling of the spin
supplementary condition within the effective field theory approach to the
post-Newtonian approximation. In particular it is shown how the covariant spin
supplementary condition can be eliminated at the level of the potential (which
is subtle in various respects) and how the dynamics can be cast into a fully
reduced Hamiltonian form. Two different methods are used and compared, one
based on the well-known Dirac bracket and the other based on an action
principle. It is discussed how the latter approach can be used to improve the
Feynman rules by formulating them in terms of reduced canonical spin variables.
| arxiv topic:gr-qc |
arxiv_dataset-29351110.2194 | Testing the accuracy of radiative cooling approximations in SPH
simulations
astro-ph.GA
Hydrodynamical simulations of star formation have stimulated a need to
develop fast and robust algorithms for evaluating radiative cooling. Here we
undertake a critical evaluation of what is currently a popular method for
prescribing cooling in SPH simulations, i.e. the polytropic cooling due
originally to Stamatellos et al. This method uses the local density and
potential to estimate the column density and optical depth to each particle and
then uses these quantities to evaluate an approximate expression for the net
radiative cooling. We evaluate the algorithm by considering both spherical and
disc-like systems with analytic density and temperature structures. In
spherical systems, the total cooling rate computed by the method is within
around 20 for the astrophysically relevant case of opacity dominated by ice
grains and is correct to within a factor of order unity for a range of opacity
laws. In disc geometry, however, the method systematically under-estimates the
cooling by a large factor at all heights in the disc. For the self-gravitating
disc studied, we find that the method under-estimates the total cooling rate by
a factor of 200. This discrepancy may be readily traced to the method's
systematic over-estimate of the disc column density and optical depth, since
(being based only on the local density and potential) it does not take into
account the low column density route for photon escape normal to the disc
plane. These results raise an obvious caution about the method's use in disc
geometry whenever an accurate cooling rate is required, although we note that
there are situations where the discrepancies highlighted above may not
significantly affect the global outcome of simulations. Finally, we draw
attention to our introduction of an analytic self-gravitating disc structure
that may be of use in the calibration of future cooling algorithms.
| arxiv topic:astro-ph.GA |
arxiv_dataset-29361110.2294 | Query Driven Visualization of Astronomical Catalogs
astro-ph.IM cs.DB
Interactive visualization of astronomical catalogs requires novel techniques
due to the huge volumes and complex structure of the data produced by existing
and upcoming astronomical surveys. The creation as well as the disclosure of
the catalogs can be handled by data pulling mechanisms. These prevent
unnecessary processing and facilitate data sharing by having users request the
desired end products.
In this work we present query driven visualization as a logical continuation
of data pulling. Scientists can request catalogs in a declarative way and set
process parameters directly from within the visualization. This results in
profound interoperation between software with a high level of abstraction.
New messages for the Simple Application Messaging Protocol are proposed to
achieve this abstraction. Support for these messages are implemented in the
Astro-WISE information system and in a set of demonstrational applications.
| arxiv topic:astro-ph.IM cs.DB |
arxiv_dataset-29371110.2394 | Testing microscopic discretization
quant-ph math.PR
What can we say about the spectra of a collection of microscopic variables
when only their coarse-grained sums are experimentally accessible? In this
paper, using the tools and methodology from the study of quantum nonlocality,
we develop a mathematical theory of the macroscopic fluctuations generated by
ensembles of independent microscopic discrete systems. We provide algorithms to
decide which multivariate gaussian distributions can be approximated by sums of
finitely-valued random vectors. We study non-trivial cases where the
microscopic variables have an unbounded range, as well as asymptotic scenarios
with infinitely many macroscopic variables. From a foundational point of view,
our results imply that bipartite gaussian states of light cannot be understood
as beams of independent d-dimensional particle pairs. It is also shown that the
classical description of certain macroscopic optical experiments, as opposed to
the quantum one, requires variables with infinite cardinality spectra.
| arxiv topic:quant-ph math.PR |
arxiv_dataset-29381110.2494 | Spectral Gap Amplification
quant-ph
A large number of problems in science can be solved by preparing a specific
eigenstate of some Hamiltonian H. The generic cost of quantum algorithms for
these problems is determined by the inverse spectral gap of H for that
eigenstate and the cost of evolving with H for some fixed time. The goal of
spectral gap amplification is to construct a Hamiltonian H' with the same
eigenstate as H but a bigger spectral gap, requiring that constant-time
evolutions with H' and H are implemented with nearly the same cost. We show
that a quadratic spectral gap amplification is possible when H satisfies a
frustration-free property and give H' for these cases. This results in quantum
speedups for optimization problems. It also yields improved constructions for
adiabatic simulations of quantum circuits and for the preparation of projected
entangled pair states (PEPS), which play an important role in quantum many-body
physics. Defining a suitable black-box model, we establish that the quadratic
amplification is optimal for frustration-free Hamiltonians and that no spectral
gap amplification is possible, in general, if the frustration-free property is
removed. A corollary is that finding a similarity transformation between a
stoquastic Hamiltonian and the corresponding stochastic matrix is hard in the
black-box model, setting limits to the power of some classical methods that
simulate quantum adiabatic evolutions.
| arxiv topic:quant-ph |
arxiv_dataset-29391110.2594 | Schemes of transmission of classical information via quantum channels
with many senders: discrete and continuous variables cases
quant-ph
Superadditivity effects in the classical capacity of discrete multi-access
channels (MACs) and continuous variable (CV) Gaussian MACs are analysed. New
examples of the manifestation of superadditivity in the discrete case are
provided including, in particular, a channel which is fully symmetric with
respect to all senders. Furthermore, we consider a class of channels for which
{\it input entanglement across more than two copies of the channels is
necessary} to saturate the asymptotic rate of transmission from one of the
senders to the receiver. The 5-input entanglement of Shor error correction
codewords surpass the capacity attainable by using arbitrary two-input
entanglement for these channels. In the CV case, we consider the properties of
the two channels (a beam-splitter channel and a "non-demolition" XP gate
channel) analyzed in [Czekaj {\it et al.}, Phys. Rev. A {\bf 82}, 020302 (R)
(2010)] in greater detail and also consider the sensitivity of capacity
superadditivity effects to thermal noise. We observe that the estimates of
amount of two-mode squeezing required to achieve capacity superadditivity are
more optimistic than previously reported.
| arxiv topic:quant-ph |
arxiv_dataset-29401110.2694 | Metallicity of M dwarfs II. A comparative study of photometric
metallicity scales
astro-ph.SR astro-ph.EP
Stellar parameters are not easily derived from M dwarf spectra, which are
dominated by complex bands of diatomic and triatomic molecules and not well
described at the line by line level by atmospheric models. M dwarf
metallicities are therefore most commonly derived through less direct
techniques. Several recent publications propose calibrations that provide the
metallicity of an M dwarf from its Ks band absolute magnitude and its V-Ks
color, but disagree at the \pm0.1 dex level. We compare these calibrations on a
sample of 23 M dwarfs, which we select as wide (> 5 arcsec) companions of F-,
G- or K- dwarfs with metallicities measured on a homogeneous scale, and which
we require to have V band photometry measured to better than \sim0.03
magnitude. We find that the Schlaufman & Laughlin (2010) calibration has lowest
offsets and residuals against our sample, and use our improved statistics to
marginally refine that calibration. With more strictly selected photometry than
in previous studies, the dispersion around the calibration is well in excess of
the [Fe/H] and photometric uncertainties. This suggests that the origin of the
remaining dispersion is astrophysical rather than observational.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-29411110.2794 | Adhesive contact delaminating at mixed mode, its thermodynamics and
analysis
math.AP
An adhesive unilateral contact between visco-elastic heat-conductive bodies
in linear Kelvin-Voigt rheology is scrutinised. The flow-rule for debonding the
adhesive is considered rate independent, unidirectional, and non-associative
due to dependence on the mixity of modes of delamination, namely of Mode I
(opening) and of Mode II (shearing). Such mode-mixity dependence of
delamination is a very pronounced (and experimentally confirmed) phenomenon
typically considered in engineering models. An anisothermal, thermodynamically
consistent model is derived, considering a heat-conductive viscoelastic
material and the coupling via thermal expansion and adhesion-depending heat
transition through the contact surface. We prove the existence of weak
solutions by passing to the limit in a carefully designed semi-implicit
time-discretization scheme.
| arxiv topic:math.AP |
arxiv_dataset-29421110.2894 | Two algorithms for fitting constrained marginal models
stat.CO stat.ME
We study in detail the two main algorithms which have been considered for
fitting constrained marginal models to discrete data, one based on Lagrange
multipliers and the other on a regression model. We show that the updates
produced by the two methods are identical, but that the Lagrangian method is
more efficient in the case of identically distributed observations. We provide
a generalization of the regression algorithm for modelling the effect of
exogenous individual-level covariates, a context in which the use of the
Lagrangian algorithm would be infeasible for even moderate sample sizes. An
extension of the method to likelihood-based estimation under $L_1$-penalties is
also considered.
| arxiv topic:stat.CO stat.ME |
arxiv_dataset-29431110.2994 | Large-time evolution of electron in photon bath
quant-ph
The problem of infrared divergence of the effective electromagnetic field
produced by elementary charges is revisited using the model of an electron
freely evolving in a photon bath. It is shown that for any finite travel time,
the effective field of the electron is infrared-finite, and that in each order
of perturbation theory the radiative contributions grow without bound in the
large-time limit. Using the Schwinger-Keldysh formalism, factorization of
divergent contributions in multi-loop diagrams is proved, and summation of the
resulting infinite series is performed. It is demonstrated that the effective
electromagnetic field of the electron vanishes in the large-time limit, and
that this vanishing respects the total charge conservation and the Gauss law.
It is concluded that the physical meaning of infrared singularity in the
effective field is the existence of a peculiar irreversible spreading of
electric charges, caused by their interaction with the photon field. This
spreading exists in vacuum as well as at finite temperature, and shows itself
in a damping of the off-diagonal elements of the momentum-space density matrix
of electron, but does not affect its momentum probability distribution. It
precludes preparation of spatially localized particle states at finite times by
operating with free particle states in the remote past. Relationship of the
obtained results to the Bloch-Nordsieck theorem is established, and discussed
from the standpoint of measurability of the electromagnetic field. The effect
of irreversible spreading on the electron diffraction in the classic two-slit
experiment is determined, and is shown to be detectable in principle by modern
devices already at room temperature.
| arxiv topic:quant-ph |
arxiv_dataset-29441110.3094 | Syndromic classification of Twitter messages
cs.CL cs.IR cs.SI
Recent studies have shown strong correlation between social networking data
and national influenza rates. We expanded upon this success to develop an
automated text mining system that classifies Twitter messages in real time into
six syndromic categories based on key terms from a public health ontology.
10-fold cross validation tests were used to compare Naive Bayes (NB) and
Support Vector Machine (SVM) models on a corpus of 7431 Twitter messages. SVM
performed better than NB on 4 out of 6 syndromes. The best performing
classifiers showed moderately strong F1 scores: respiratory = 86.2 (NB);
gastrointestinal = 85.4 (SVM polynomial kernel degree 2); neurological = 88.6
(SVM polynomial kernel degree 1); rash = 86.0 (SVM polynomial kernel degree 1);
constitutional = 89.3 (SVM polynomial kernel degree 1); hemorrhagic = 89.9
(NB). The resulting classifiers were deployed together with an EARS C2
aberration detection algorithm in an experimental online system.
| arxiv topic:cs.CL cs.IR cs.SI |
arxiv_dataset-29451110.3194 | Controlled Total Variation regularization for inverse problems
cs.CV
This paper provides a new algorithm for solving inverse problems, based on
the minimization of the $L^2$ norm and on the control of the Total Variation.
It consists in relaxing the role of the Total Variation in the classical Total
Variation minimization approach, which permits us to get better approximation
to the inverse problems. The numerical results on the deconvolution problem
show that our method outperforms some previous ones.
| arxiv topic:cs.CV |
arxiv_dataset-29461110.3294 | Algebraic theories, monads, and arities
math.CT cs.LO
Monads are of interest both in semantics and in higher dimensional algebra.
It turns out that the idea behind usual notion finitary monads (whose values on
all sets can be computed from their values on finite sets) extends to a more
general class of monads called monads with arities, so that not only algebraic
theories can be computed from a proper set of arities, but also more general
structures like n-categories, the computing process being realized using Kan
extensions. This Master thesis compiles the required material in order to
understand this question of arities and reconstruction of monads, and tries to
give some examples of relevant interest from both semantics and higher category
theory. A discussion on the promising field of operads is then provided as
appendix.
| arxiv topic:math.CT cs.LO |
arxiv_dataset-29471110.3394 | Antiferromagnetic spin-S chains with exactly dimerized ground states
cond-mat.str-el
We show that spin S Heisenberg spin chains with an additional three-body
interaction of the form (S_{i-1}S_{i})(S_{i}S_{i+1})+h.c. possess fully
dimerized ground states if the ratio of the three-body interaction to the
bilinear one is equal to 1/(4S(S+1)-2). This result generalizes the
Majumdar-Ghosh point of the J_1-J_2 chain, to which the present model reduces
for S=1/2. For S=1, we use the density matrix renormalization group method
(DMRG) to show that the transition between the Haldane and the dimerized phases
is continuous with central charge c=3/2. Finally, we show that such a
three-body interaction appears naturally in a strong-coupling expansion of the
Hubbard model, and we discuss the consequences for the dimerization of actual
antiferromagnetic chains.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-29481110.3494 | Droplet-shaped waves: Causal finite-support analogs of X-shaped waves
physics.optics math-ph math.MP physics.class-ph
A model of steady-state X-shaped wave generation by a superluminal
(supersonic) pointlike source infinitely moving along a straight line is
extended to a more realistic causal scenario of a source pulse launched at time
zero and propagating rectilinearly at constant superluminal speed. In the case
of infinitely short (delta) pulse, the new model yields an analytical solution,
corresponding to the propagation-invariant X-shaped wave clipped by a
droplet-shaped support, which perpetually expands along the propagation and
transversal directions, thus tending the droplet-shaped wave to the X-shaped
one.
| arxiv topic:physics.optics math-ph math.MP physics.class-ph |
arxiv_dataset-29491110.3594 | Charge symmetry violation: a NNLO study of partonic observables
hep-ph nucl-th
Charge and isospin symmetry violations to valence and sea distribution
functions in the nucleon are evaluated (at low resolution scale) by means of a
meson cloud model and light-cone quark wave functions. Their perturbative
evolution are implemented at Next-to-next-to-leading order (NNLO) using an
original evolution code in order to include the perturbatively generated
strange - anti-strange asymmetry typical of the three loop evolution expansion.
Charge symmetry violating QED effects are also added and the distributions,
evolved at the experimental scale, are compared with available information. The
role of non-perturbative effects is emphasized in the interpretation of the, so
called, NuTeV anomaly and new experiments at very-high energy.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-29501110.3694 | Charmonium and meson-molecule hybrid tetraquarks - Vector meson width
and the isospin breaking in the X(3872) decay
hep-ph
In the X(3872) decay, both of the J/\psi\pi\pi\ and J/\psi\pi\pi\pi\
branching fractions are observed experimentally, and their sizes are comparable
to each other. In order to clarify the mechanism to cause such a large isospin
violation, we investigate X(3872) employing a model of coupled-channel
two-meson scattering with a ccbar core. The two-meson states consist of
D0Dbar*0, D+Dbar*-, J/\psi\rho, and J/\psi\omega. The effects of the \rho\ and
\omega\ meson width are also taken into account.
We calculate the transfer strength from the ccbar core to the final two-meson
states. It is found that very narrow J/\psi\rho\ and J/\psi\omega\ peaks appear
very close to the D0Dbar*0 threshold for a wide range of variation in the
parameter sets. The size of the J/\psi\rho\ peak is almost the same as that of
J/\psi\omega, which is consistent with the experiments. The large width of the
\rho\ meson makes the originally small isospin violation by about five times
larger.
| arxiv topic:hep-ph |
arxiv_dataset-29511110.3794 | CANDELS Observations of the Structural Properties and Evolution of
Galaxies in a Cluster at z=1.62
astro-ph.CO
We discuss the structural and morphological properties of galaxies in a
z=1.62 proto-cluster using near-IR imaging data from Hubble Space Telescope
Wide Field Camera 3 data of the Cosmic Assembly Near-IR Deep Extragalactic
Legacy Survey (CANDELS). The cluster galaxies exhibit a clear color-morphology
relation: galaxies with colors of quiescent stellar populations generally have
morphologies consistent with spheroids, and galaxies with colors consistent
with ongoing star formation have disk-like and irregular morphologies. The size
distribution of the quiescent cluster galaxies shows a deficit of compact (<
1kpc), massive galaxies compared to CANDELS field galaxies at z=1.6. As a
result the cluster quiescent galaxies have larger average effective sizes
compared to field galaxies at fixed mass at greater than 90% significance.
Combined with data from the literature, the size evolution of quiescent cluster
galaxies is relatively slow from z~1.6 to the present, growing as
(1+z)^(-0.6+/-0.1). If this result is generalizable, then it implies that
physical processes associated with the denser cluster region seems to have
caused accelerated size growth in quiescent galaxies prior to z=1.6 and slower
subsequent growth at z<1.6 compared to galaxies in the lower density field. The
quiescent cluster galaxies at z=1.6 have higher ellipticities compared to lower
redshift samples at fixed mass, and their surface-brightness profiles suggest
that they contain extended stellar disks. We argue the cluster galaxies require
dissipationless (i.e., gas-poor or "dry") mergers to reorganize the disk
material and to match the relations for ellipticity, stellar mass, size, and
color of early-type galaxies in z<1 clusters.
| arxiv topic:astro-ph.CO |
arxiv_dataset-29521110.3894 | Determination of the chromospheric quiet network element area index and
its variation during 2008-2011
astro-ph.SR
Generally it has been considered that the plages and sunspots are the main
contributors to the solar irradiance. There are small scale structures on the
sun with intermediate magnetic fields that could also contribute to the solar
irradiance. It has not yet been quantified how much of these small scale
structures contribute to the solar irradiance and how much it varies over the
solar cycle.
In this paper, we used Ca II K images obtained from the telescope installed
at Kodaikanal observatory. We report a method to separate the network elements
from the background structure and plage regions. We compute the changes in the
network element area index during the minimum phase of solar cycle and part of
the ascending phase of cycle 24. The measured area occupied by the network
elements is about 30% and plages less than 1% of the solar disk during the
observation period from February 2008-2011. During the extended period of
minimum activity it is observed that the network element area index decreases
by about 7% compared to the area occupied by the network elements in 2008. A
long term study of network element area index is required to understand the
variations over the solar cycle.
| arxiv topic:astro-ph.SR |
arxiv_dataset-29531110.3994 | Voronoi Cell Patterns: theoretical model and applications
cond-mat.stat-mech physics.soc-ph
We use a simple fragmentation model to describe the statistical behavior of
the Voronoi cell patterns generated by a set of points in 1D and in 2D. In
particular, we are interested in the distribution of sizes of these Voronoi
cells. Our model is completely defined by two probability distributions in 1D
and again in 2D, the probability to add a new point inside an existing cell and
the probability that this new point is at a particular position relative to the
preexisting point inside this cell. In 1D the first distribution depends on a
single parameter while the second distribution is defined through a
fragmentation kernel; in 2D both distributions depend on a single parameter.
The fragmentation kernel and the control parameters are closely related to the
physical properties of the specific system under study. We use our model to
describe the Voronoi cell patterns of several systems. Specifically, we study
the island nucleation with irreversible attachment, the 1D car parking problem,
the formation of second-level administrative divisions, and the pattern formed
by the Paris M\'etro stations.
| arxiv topic:cond-mat.stat-mech physics.soc-ph |
arxiv_dataset-29541110.4094 | A Logic for True Concurrency
cs.LO
We propose a logic for true concurrency whose formulae predicate about events
in computations and their causal dependencies. The induced logical equivalence
is hereditary history preserving bisimilarity, and fragments of the logic can
be identified which correspond to other true concurrent behavioural
equivalences in the literature: step, pomset and history preserving
bisimilarity. Standard Hennessy-Milner logic, and thus (interleaving)
bisimilarity, is also recovered as a fragment. We also propose an extension of
the logic with fixpoint operators, thus allowing to describe causal and
concurrency properties of infinite computations. We believe that this work
contributes to a rational presentation of the true concurrent spectrum and to a
deeper understanding of the relations between the involved behavioural
equivalences.
| arxiv topic:cs.LO |
arxiv_dataset-29551110.4194 | Evidence for spin correlation in ttbar production
hep-ex
We present a measurement of the ratio of events with correlated t and tbar
spins to the total number of ttbar events. This ratio f is evaluated using a
matrix-element-based approach in events with a single lepton (electron or muon)
and at least four jets. We analyze ppbar collisions data corresponding to an
integrated luminosity of 5.3 fb^-1 collected with the D0 detector at the
Fermilab Tevatron collider operating at a center of mass energy $\sqrt{s}=1.96$
TeV. Combining this result with a recent measurement of f in dilepton final
states, we find f in agreement with the standard model. In addition, the
combination provides evidence for the presence of spin correlation in ttbar
events with a significance of more than three standard deviations.
| arxiv topic:hep-ex |
arxiv_dataset-29561110.4294 | Mean Field description of and propagation of chaos in recurrent
multipopulation networks of Hodgkin-Huxley and Fitzhugh-Nagumo neurons
q-bio.NC math.PR
We derive the mean-field equations arising as the limit of a network of
interacting spiking neurons, as the number of neurons goes to infinity. The
neurons belong to a fixed number of populations and are represented either by
the Hodgkin-Huxley model or by one of its simplified version, the
Fitzhugh-Nagumo model. The synapses between neurons are either electrical or
chemical. The network is assumed to be fully connected. The maximum
conductances vary randomly. Under the condition that all neurons initial
conditions are drawn independently from the same law that depends only on the
population they belong to, we prove that a propagation of chaos phenomenon
takes places, namely that in the mean-field limit, any finite number of neurons
become independent and, within each population, have the same probability
distribution. This probability distribution is solution of a set of implicit
equations, either nonlinear stochastic differential equations resembling the
McKean-Vlasov equations, or non-local partial differential equations resembling
the McKean-Vlasov-Fokker- Planck equations. We prove the well-posedness of
these equations, i.e. the existence and uniqueness of a solution. We also show
the results of some preliminary numerical experiments that indicate that the
mean-field equations are a good representation of the mean activity of a finite
size network, even for modest sizes. These experiment also indicate that the
McKean-Vlasov-Fokker- Planck equations may be a good way to understand the
mean-field dynamics through, e.g., a bifurcation analysis.
| arxiv topic:q-bio.NC math.PR |
arxiv_dataset-29571110.4394 | Continuous-wave Cascaded-Harmonic Generation and Multi-Photon Raman
Lasing in Lithium Niobate Whispering-Gallery Resonators
physics.optics
We report experimental demonstration of continuous-wave cascaded-harmonic
generation and Raman lasing in a millimeter-scale lithium niobate
whispering-gallery resonator pumped at a telecommunication-compatible infrared
wavelength. Intensity enhancement through multiple recirculations in the
whispering-gallery resonator and quasi phase-matching through a nonuniform
crystal poling enable simultaneous cascaded-harmonic generation up to the
fourth-harmonic accompanied by stimulated Raman, two-photon, three-photon, and
four-photon Raman scattering corresponding the molecular vibrational
wavenumbers 632 cm-1 and 255 cm-1 in z-cut lithium niobate at pump power levels
as low as 200mW. We demonstrate simultaneous cascaded-harmonic generation and
Raman lasing by observing the spectrum of the scattered light from the
resonator and by capturing the image of the decoupled light from the resonator
on a color CCD camera.
| arxiv topic:physics.optics |
arxiv_dataset-29581110.4494 | Massive vector fields on the Schwarzschild spacetime: quasinormal modes
and bound states
hep-th gr-qc
We study the propagation of a massive vector or Proca field on the
Schwarzschild spacetime. The field equations are reduced to a one-dimensional
wave equation for the odd-parity part of the field and two coupled equations
for the even-parity part of the field. We use numerical techniques based on
solving (scalar or matrix-valued) three-term recurrence relations to compute
the spectra of both quasi-normal modes and quasi-bound states, which have no
massless analogue, complemented in the latter case by a forward-integration
method. We study the radial equations analytically in both the near-horizon and
far-field regions and use a matching procedure to compute the associated
spectra in the small-mass limit. Finally, we comment on extending our results
to the Kerr geometry and its phenomenological relevance for hidden photons
arising e.g. in string theory compactifications.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-29591110.4594 | G2-structure deformations and warped products
math.DG
We overview the properties of non-infinitesimal deformations of G2-structures
on seven-manifolds, and in particular, focus on deformations that lie in the
seven-dimensional representation of G2 and are thus defined by a vector. We
then consider deformations from G2-structures with the torsion class having
one-dimensional and seven-dimensional components (so-called conformally nearly
parallel G2-manifolds) to G2-structures with just a one-dimensional torsion
component (nearly parallel G2-manifolds). We find that deformations between
such structures exist if and only if the metric is a particular warped product
metric.
| arxiv topic:math.DG |
arxiv_dataset-29601110.4694 | Poincare 2-group and quantum gravity
gr-qc hep-th math-ph math.MP
We show that General Relativity can be formulated as a constrained
topological theory for flat 2-connections associated to the Poincar\'e 2-group.
Matter can be consistently coupled to gravity in this formulation. We also show
that the edge lengths of the spacetime manifold triangulation arise as the
basic variables in the path-integral quantization, while the state-sum
amplitude is an evaluation of a colored 3-complex, in agreement with the
category theory results. A 3-complex amplitude for Euclidean quantum gravity is
proposed.
| arxiv topic:gr-qc hep-th math-ph math.MP |
arxiv_dataset-29611110.4794 | Bilinear dispersive estimates via space-time resonances. Part I : the
one dimensional case
math.AP math.CA
We prove new bilinear dispersive estimates. They are obtained and described
via a bilinear time-frequency analysis following the space-time resonances
method, introduced by Masmoudi, Shatah, and the second author. They allow us to
understand the large time behavior of solutions of quadratic dispersive
equations.
| arxiv topic:math.AP math.CA |
arxiv_dataset-29621110.4894 | Gravitational Lensing with Three-Dimensional Ray Tracing
astro-ph.CO
High redshift sources suffer from magnification or demagnification due to
weak gravitational lensing by large scale structure. One consequence of this is
that the distance-redshift relation, in wide use for cosmological tests,
suffers lensing-induced scatter which can be quantified by the magnification
probability distribution. Predicting this distribution generally requires a
method for ray-tracing through cosmological N-body simulations. However,
standard methods tend to apply the multiple thin-lens approximation. In an
effort to quantify the accuracy of these methods, we develop an innovative code
that performs ray-tracing without the use of this approximation. The efficiency
and accuracy of this computationally challenging approach can be improved by
careful choices of numerical parameters; therefore, the results are analysed
for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and
Navarro-Frenk-White lenses. Preliminary comparisons are drawn with the multiple
lens-plane ray-bundle method in the context of cosmological mass distributions
for a source redshift of $z_{s}=0.5$.
| arxiv topic:astro-ph.CO |
arxiv_dataset-29631110.4994 | A hierarchy of energy- and flux-budget (EFB) turbulence closure models
for stably stratified geophysical flows
physics.ao-ph astro-ph.SR physics.flu-dyn
In this paper we advance physical background of the energy- and flux-budget
turbulence closure based on the budget equations for the turbulent kinetic and
potential energies and turbulent fluxes of momentum and buoyancy, and a new
relaxation equation for the turbulent dissipation time-scale. The closure is
designed for stratified geophysical flows from neutral to very stable and
accounts for the Earth rotation. In accordance to modern experimental evidence,
the closure implies maintaining of turbulence by the velocity shear at any
gradient Richardson number Ri, and distinguishes between the two principally
different regimes: "strong turbulence" at Ri << 1 typical of boundary-layer
flows and characterised by the practically constant turbulent Prandtl number;
and "weak turbulence" at Ri > 1 typical of the free atmosphere or deep ocean,
where the turbulent Prandtl number asymptotically linearly increases with
increasing Ri (which implies very strong suppression of the heat transfer
compared to the momentum transfer). For use in different applications, the
closure is formulated at different levels of complexity, from the local
algebraic model relevant to the steady-state regime of turbulence to a
hierarchy of non-local closures including simpler down-gradient models,
presented in terms of the eddy-viscosity and eddy-conductivity, and general
non-gradient model based on prognostic equations for all basic parameters of
turbulence including turbulent fluxes.
| arxiv topic:physics.ao-ph astro-ph.SR physics.flu-dyn |
arxiv_dataset-29641110.5094 | Electric vector rotations of \pi/2 in polarized circumstellar SiO maser
emission
astro-ph.SR
This paper examines the detailed sub-milliarcsecond polarization properties
of an individual SiO maser feature displaying a rotation in polarization
electric vector position angle of approximately \pi/2 across the feature. Such
rotations are a characteristic observational signature of circumstellar SiO
masers detected toward a number of late-type, evolved stars. We employ a new
calibration method for accurate circular VLBI polarimetry at millimeter
wavelengths, to present the detailed Stokes {I,Q,U,V} properties for this
feature. We analyze the fractional linear and circular polarization as a
function of projected angular distance across the extent of the feature, and
compare these measurements against several theoretical models proposed for
sharp rotations of electric vector position angle in polarized SiO maser
emission. We find that the rotation is most likely caused by the angle \theta
between the line of sight and a projected magnetic field crossing the critical
Van Vleck angle for maser propagation. The fractional linear polarization
profile m_l(\theta) is well-fit by standard models for polarized maser
transport, but we find less agreement for the fractional circular polarization
profile m_c(\theta).
| arxiv topic:astro-ph.SR |
arxiv_dataset-29651110.5194 | Determining CP violation angle $\gamma$ with B decays into a
scalar/tensor meson
hep-ph
We propose a new way for determining the CP violation angle $\gamma$ without
any hadronic uncertainty. The suggested method is to use the two triangles
formed by the decay amplitudes of $B^\pm\to (D^0,\bar D^0,D_{CP}^0)
K^{*\pm}_{0(2)}(1430)$. The advantages are that large CP asymmetries are
expected in these processes and only singly Cabibbo-suppressed $D$ decay modes
are involved. Measurements of the branching fractions of the neutral $B_d$
decays into $DK^{*}_{0(2)}(1430)$ and the time-dependent CP asymmetries in
$B_s\to (D^0, \bar D^0) M$ ($M=f_0(980),f_0(1370), f_2'(1525), f_1(1285),
f_1(1420), h_1(1180))$ provide an alternative way to extract the angle
$\gamma$, which will increase the statistical significance.
| arxiv topic:hep-ph |
arxiv_dataset-29661110.5294 | Production and Spectroscopy of Heavy Hadrons at the LHC
hep-ex
Measurements of heavy flavor production and decay have featured prominently
in the early results from the four large LHC experiments: ALICE, ATLAS, CMS,
and LHCb. These results provide tests of QCD models in a new energy region and
point the way toward future measurements of CP violation and searches for new
physics. An overview of open heavy flavor studies is presented here, focusing
on how the new measurements extend our knowledge of this area of physics. Heavy
quarkonia states at the LHC are summarized in other proceedings of this
conference. I also discuss briefly how heavy flavor measurements are likely to
evolve as LHC luminosities increase.
| arxiv topic:hep-ex |
arxiv_dataset-29671110.5394 | Mixing time upper bound for the uniformized Rosenthal walk on the
special orthogonal groups
math.PR math.CO math.RT
We prove that a uniformized variant of both the Rosenthal walk
\cite{Rosenthal} and the Kac random walk \cite{Kac} on SO(n) mixes in
$\cO(n^3)$ steps in total variation distance. The proof also extends easily to
Rosenthal walk with fixed angle $\theta \neq \pi$. To the best of our
knowledge, this is the first polynomial time bound for both walks. The
techniques employed are mainly from representation theory of SO(n). But a
crucial new ingredient is the interpretation of the Fourier coefficients of the
character ratio as counting the number of particle cascade paths arising from
the classical branching rules.
| arxiv topic:math.PR math.CO math.RT |
arxiv_dataset-29681110.5494 | Non-perturbative renormalization for general improved staggered
bilinears
hep-lat
We present results for non-perturbative renormalization (NPR) factors for
staggered fermion bilinears of arbitrary spin and taste. We use "covariant"
bilinears which transform irreducibly under the lattice translation and
rotation group, and thus do not mix. We form ~ 30 ratios which have no
anomalous dimensions, and compare the NPR results to those from 1-loop
perturbation theory. We also compare the absolute renormalization factors
(which, in general, do have anomalous dimensions) to 1-loop perturbation
theory. We use asqtad and HYP-smeared staggered valence fermions on the coarse
MILC asqtad lattices.
| arxiv topic:hep-lat |
arxiv_dataset-29691110.5594 | Boundary-degenerate elliptic operators and Holder continuity for
solutions to variational equations and inequalities
math.AP math.PR q-fin.CP q-fin.PR
The Heston stochastic volatility process, which is widely used as an asset
price model in mathematical finance, is a paradigm for a degenerate diffusion
process where the degeneracy in the diffusion coefficient is proportional to
the square root of the distance to the boundary of the half-plane. The
generator of this process with killing, called the elliptic Heston operator, is
a second-order, degenerate-elliptic partial differential operator whose
coefficients have linear growth in the spatial variables and where the
degeneracy in the operator symbol is proportional to the distance to the
boundary of the half-plane. With the aid of weighted Sobolev spaces, we prove
supremum bounds, a Harnack inequality, and H\"older continuity near the
boundary for solutions to variational equations defined by the elliptic Heston
operator, as well as H\"older continuity up to the boundary for solutions to
variational inequalities defined by the elliptic Heston operator. In
mathematical finance, solutions to obstacle problems for the elliptic Heston
operator correspond to value functions for perpetual American-style options on
the underlying asset.
| arxiv topic:math.AP math.PR q-fin.CP q-fin.PR |
arxiv_dataset-29701110.5694 | Realizability of the Lorentzian (n,1)-Simplex
gr-qc math-ph math.MP
In a previous article [JHEP 1111 (2011) 072; arXiv:1108.4965] we have
developed a Lorentzian version of the Quantum Regge Calculus in which the
significant differences between simplices in Lorentzian signature and Euclidean
signature are crucial. In this article we extend a central result used in the
previous article, regarding the realizability of Lorentzian triangles, to
arbitrary dimension. This technical step will be crucial for developing the
Lorentzian model in the case of most physical interest: 3+1 dimensions.
We first state (and derive in an appendix) the realizability conditions on
the edge-lengths of a Lorentzian n-simplex in total dimension n=d+1, where d is
the number of space-like dimensions. We then show that in any dimension there
is a certain type of simplex which has all of its time-like edge lengths
completely unconstrained by any sort of triangle inequality. This result is the
d+1 dimensional analogue of the 1+1 dimensional case of the Lorentzian
triangle.
| arxiv topic:gr-qc math-ph math.MP |
arxiv_dataset-29711110.5794 | STor: Social Network based Anonymous Communication in Tor
cs.CR
Anonymity networks hide user identities with the help of relayed anonymity
routers. However, the state-of-the-art anonymity networks do not provide an
effective trust model. As a result, users cannot circumvent malicious or
vulnerable routers, thus making them susceptible to malicious router based
attacks (e.g., correlation attacks). In this paper, we propose a novel social
network based trust model to help anonymity networks circumvent malicious
routers and obtain secure anonymity. In particular, we design an input
independent fuzzy model to determine trust relationships between friends based
on qualitative and quantitative social attributes, both of which can be readily
obtained from existing social networks. Moreover, we design an algorithm for
propagating trust over an anonymity network. We integrate these two elements in
STor, a novel social network based Tor. We have implemented STor by modifying
the Tor's source code and conducted experiments on PlanetLab to evaluate the
effectiveness of STor. Both simulation and PlanetLab experiment results have
demonstrated that STor can achieve secure anonymity by establishing trust-based
circuits in a distributed way. Although the design of STor is based on Tor
network, the social network based trust model can be adopted by other anonymity
networks.
| arxiv topic:cs.CR |
arxiv_dataset-29721110.5894 | Spectral theory for one-dimensional symmetric Levy processes killed upon
hitting the origin
math.PR math.SP
Spectral theory for the transition semigroup of one-dimensional symmetric
Levy process killed upon hitting the origin is studied. Under very mild
assumptions, an integral-type formula for eigenfunctions is obtained, and
eigenfunction expansion of transition operators and the generator is given. As
an application, integral fomulae for the transition density and the
distribution of the hitting time of the origin are proved.
| arxiv topic:math.PR math.SP |
arxiv_dataset-29731110.5994 | On seven dimensional quaternionic contact solvable Lie groups
math.DG
We answer in the affirmative a question posed by Ivanov and Vassilev on the
existence of a seven dimensional quaternionic contact manifold with closed
fundamental 4-form and non-vanishing torsion endomorphism. Moreover, we show an
approach to the classification of seven dimensional solvable Lie groups having
an integrable left invariant quaternionic contact structure. In particular, we
prove that the unique seven dimensional nilpotent Lie group admitting such a
structure is the quaternionic Heisenberg group.
| arxiv topic:math.DG |
arxiv_dataset-29741110.6094 | INTEGRAL - status of the mission
astro-ph.HE
The ESA gamma-ray observatory INTEGRAL, launched on 17 October 2002,
continues to produce a wealth of discoveries and new results on compact high
energy Galactic objects, nuclear gamma-ray line emission, diffuse line and
continuum emission, cosmic background radiation, AGN, high energy transients
and sky surveys. The mission's technical status is healthy and INTEGRAL is
continuing its scientific operations well beyond its 5-year technical design
lifetime until, at least, 31 December 2014. This paper describes the current
status of INTEGRAL including the spacecraft technical state-of-health and the
scientific observing programme including its on-going and future multi-year
"legacy" programmes.
| arxiv topic:astro-ph.HE |
arxiv_dataset-29751110.6194 | Invariant Based Quartet Puzzling
q-bio.PE
Traditional Quartet Puzzling algorithms use maximum likelihood methods to
reconstruct quartet trees, and a puzzling algorithm to combine these quartets
into a tree for the full collection of $n$ taxa. We propose a variation of
Quartet Puzzling in which the quartet trees are reconstructed using
biologically symmetric invariants. We find that under certain conditions,
invariant based quartet puzzling outperforms Quartet Puzzling using maximum
likelihood.
| arxiv topic:q-bio.PE |
arxiv_dataset-29761110.6294 | Isospin breaking effects due to the up-down mass difference in Lattice
QCD
hep-lat hep-ph
We present a new method to evaluate with high precision isospin breaking
effects due to the small mass difference between the up and down quarks using
lattice QCD. Our proposal is applicable in principle to any hadronic observable
which can be computed on the lattice. It is based on the expansion of the
path-integral in powers of the small parameter md-mu. In this paper, we apply
this method to compute the leading isospin breaking effects for several
physical quantities of interest: the kaon meson masses, the kaon decay
constant, the form factors of semileptonic Kl3 decays and the neutron-proton
mass splitting.
| arxiv topic:hep-lat hep-ph |
arxiv_dataset-29771110.6394 | Bistable defect structures in blue phase devices
cond-mat.soft
Blue phases (BPs) are liquid crystals made up by networks of defects, or
disclination lines. While existing phase diagrams show a striking variety of
competing metastable topologies for these networks, very little is known as to
how to kinetically reach a target structure, or how to switch from one to the
other, which is of paramount importance for devices. We theoretically identify
two confined blue phase I systems in which by applying an appropriate series of
electric field it is possible to select one of two bistable defect patterns.
Our results may be used to realise new generation and fast switching
energy-saving bistable devices in ultrathin surface treated BPI wafers.
| arxiv topic:cond-mat.soft |
arxiv_dataset-29781110.6494 | Coleman de Luccia geometry reconsidered and ADS/CFT
hep-th gr-qc
We reconsidered the Coleman de Luccia solution building an AdS4 bubble
expanding into a false flat vacuum. In this construction when junction
conditions are imposed we find an upper bound to the radius of the AdS4 and a
domain wall whose tension is a function of the minimum of the scalar potential.
We prove that this solution is exactly the solution found by Coleman and de
Luccia, but in addition there is a new condition that restricts the AdS4 radius
and a precise relation between the tension and the minimum of the scalar
potential. The applicability of the ADS/CFT correspondence is discussed.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-29791110.6594 | Around Operator Monotone Functions
math.FA
We show that the symmetrized product $AB+BA$ of two positive operators $A$
and $B$ is positive if and only if $f(A+B)\leq f(A)+f(B)$ for all non-negative
operator monotone functions $f$ on $[0,\infty)$ and deduce an operator
inequality. We also give a necessary and sufficient condition for that the
composition $f\circ g$ of an operator convex function $f$ on $[0,\infty)$ and a
non-negative operator monotone function $g$ on an interval $(a,b)$ is operator
monotone and give some applications.
| arxiv topic:math.FA |
arxiv_dataset-29801110.6694 | Approximate nonlinear self-adjointness and approximate conservation laws
math-ph math.MP
In this paper, approximate nonlinear self-adjointness for perturbed PDEs is
introduced and its properties are studied. Consequently, approximate
conservation laws which cannot be obtained by the approximate Noether theorem
are constructed by means of the method. As an application, a class of perturbed
nonlinear wave equations is considered to illustrate the effectiveness.
| arxiv topic:math-ph math.MP |
arxiv_dataset-29811110.6794 | Decay properties of Klein-Gordon fields on Kerr-AdS spacetimes
gr-qc hep-th math.AP
This paper investigates the decay properties of solutions to the massive
linear wave equation $\Box_g \psi + \frac{{\alpha}}{l^2} \psi =0$ for $g$ the
metric of a Kerr-AdS spacetime satisfying $|a|l<r_+^2$ and $\alpha<9/4$
satisfying the Breitenlohner Freedman bound. We prove that the non-degenerate
energy of $\psi$ with respect to an appropriate foliation of spacelike slices
decays like $(\log t^\star)^{-2}$. Our estimates are expected to be sharp from
heuristic and numerical arguments in the physics literature suggesting that
general solutions will only decay logarithmically. The underlying reason for
the slow decay rate can be traced back to a stable trapping phenomenon for
asymptotically anti de Sitter black holes which is in turn a consequence of the
reflecting boundary conditions for $\psi$ at null-infinity.
| arxiv topic:gr-qc hep-th math.AP |
arxiv_dataset-29821110.6894 | On the spectrum of 1D quantum Ising quasicrystal
math-ph cond-mat.stat-mech math.DS math.MP math.SP
We consider one dimensional quantum Ising spin-1/2 chains with two-valued
nearest neighbor couplings arranged in a quasi-periodic sequence, with uniform,
transverse magnetic field. By employing the Jordan-Wigner transformation of the
spin operators to spinless fermions, the energy spectrum can be computed
exactly on a finite lattice. By employing the transfer matrix technique and
investigating the dynamics of the corresponding trace map, we show that in the
thermodynamic limit the energy spectrum is a Cantor set of zero Lebesgue
measure. Moreover, we show that local Hausdorff dimension is continuous and
nonconstant over the spectrum. This forms a rigorous counterpart of numerous
numerical studies.
| arxiv topic:math-ph cond-mat.stat-mech math.DS math.MP math.SP |
arxiv_dataset-29831111.0064 | Proceedings 10th International Workshop on Parallel and Distributed
Methods in verifiCation
cs.DC cs.LO cs.SE
This volume contains the proceedings of the 10th International Workshop on
Parallel and Distributed Methods in verifiCation (PDMC 2011) that took place in
Snowbird, Utah, on July 14, 2011. The workshop was co-located with 23rd
International Conference on Computer Aided Verification (CAV 2011). The PDMC
workshop series covers all aspects related to the verification and analysis of
very large and complex systems using, in particular, methods and techniques
that exploit contemporary, hence parallel, hardware architectures. To celebrate
the 10th anniversary of PDMC, the workshop consisted of a half day invited
session together and a half day session of regular contributed presentations.
| arxiv topic:cs.DC cs.LO cs.SE |
arxiv_dataset-29841111.0164 | Soliton equations and the Riemann-Schottky problem
math.AG hep-th
Novikov's conjecture on the Riemann-Schottky problem: {\it the Jacobians of
smooth algebraic curves are precisely those indecomposable principally
polarized abelian varieties (ppavs) whose theta-functions provide solutions to
the Kadomtsev-Petviashvili (KP) equation}, was the first evidence of nowadays
well-established fact: connections between the algebraic geometry and the
modern theory of integrable systems is beneficial for both sides.
The purpose of this paper is twofold. Our first goal is to present a proof of
the strongest known characterization of a Jacobian variety in this direction:
{\it an indecomposable ppav $X$ is the Jacobian of a curve if and only if its
Kummer variety $K(X)$ has a trisecant line} and the solution of the
characterization problem of principally polarized Prym varieties. The latter
problem is almost as old and famous as the Riemann-Schottky problem but is much
harder. In some sense the Prym varieties may be geometrically the
easiest-to-understand ppavs beyond Jacobians, and studying them may be a first
step towards understanding the geometry of more general abelian varieties as
well.
Our second and primary objective is to take this opportunity to elaborate on
motivations underlining the proposed solution of the Riemann-Schottky problem,
to introduce a certain circle of ideas and methods, developed in the theory of
soliton equations, and to convince the reader that they are algebro-geometric
in nature, simple and universal enough to be included in the Handbook of
moduli.
| arxiv topic:math.AG hep-th |
arxiv_dataset-29851111.0264 | Isoparametric hypersurfaces in Damek-Ricci spaces
math.DG
We construct uncountably many isoparametric families of hypersurfaces in
Damek-Ricci spaces. We characterize those of them that have constant principal
curvatures by means of the new concept of generalized Kahler angle. It follows
that, in general, these examples are inhomogeneous and have nonconstant
principal curvatures. We also find new cohomogeneity one actions on
quaternionic hyperbolic spaces, and an isoparametric family of inhomogeneous
hypersurfaces with constant principal curvatures in the Cayley hyperbolic
plane.
| arxiv topic:math.DG |
arxiv_dataset-29861111.0364 | Relativistic ideal Bose gas in Harmonic traps
cond-mat.stat-mech physics.atm-clus
Using semiclassical approximation method, Bose-Einstein condensation (BEC) of
a relativistic ideal boson gas (RIBG) with and without antibosons in
three-dimensional (3-D) harmonic traps is investigated. The BEC transition
temperature T_{c} and the Helmholtz free energy at T_{c} are calculated. The
effect of the rest mass of the boson on the properties of the system is also
studied. We find that T_{c} of RIBG is higher than that of the nonrelativistic
approximation. The RIBG with antibosons is also investigated and it is found
that the Helmholtz free energy of the system with antibosons at T_{c} is lower
than that of the system without antibosons. It implies that the system with
antibosons is more stable.
| arxiv topic:cond-mat.stat-mech physics.atm-clus |
arxiv_dataset-29871111.0464 | Higher derivative type II string effective actions, automorphic forms
and E11
hep-th
By dimensionally reducing the ten-dimensional higher derivative type IIA
string theory effective action we place constraints on the automorphic forms
that appear in the effective action in lower dimensions. We propose a number of
properties of such automorphic forms and consider the prospects that E11 can
play a role in the formulation of the higher derivative string theory effective
action.
| arxiv topic:hep-th |
arxiv_dataset-29881111.0564 | Bound States in the Mirror TBA
hep-th
The spectrum of the light-cone AdS_5 \times S^5 superstring contains states
composed of particles with complex momenta including in particular those which
turn into bound states in the decompactification limit. We propose the mirror
TBA description for these states. We focus on a three-particle state which is a
finite-size representative of a scattering state of a fundamental particle and
a two-particle bound state and dual to an operator from the su(2) sector of N=4
SYM. We find that the analytic behavior of Y-functions differs drastically from
the case of states with real momenta. Most importantly, Y_Q-functions exhibit
poles in the analyticity strip which leads to the appearance of new terms in
the formula for the energy of this state. In addition, the TBA equations are
supplied by quantization conditions which involve Y_2. Considering yet another
example of a three-particle state, we find that the corresponding quantization
conditions do not even involve Y_1. Our treatment can be generalized to a wide
class of states with complex momenta.
| arxiv topic:hep-th |
arxiv_dataset-29891111.0664 | Massive black hole binaries: dynamical evolution and observational
signatures
astro-ph.CO
The study of the dynamical evolution of massive black hole pairs in mergers
is crucial in the context of a hierarchical galaxy formation scenario. The
timescales for the formation and the coalescence of black hole binaries are
still poorly constrained, resulting in large uncertainties in the expected rate
of massive black hole binaries detectable in the electromagnetic and
gravitational wave spectra. Here we review the current theoretical
understanding of the black hole pairing in galaxy mergers, with a particular
attention to recent developments and open issues. We conclude with a review of
the expected observational signatures of massive binaries, and of the
candidates discussed in literature to date.
| arxiv topic:astro-ph.CO |
arxiv_dataset-29901111.0764 | Nonequilibrium transport properties of a double quantum dot in the Kondo
regime
cond-mat.mes-hall cond-mat.str-el
We analyze the nonequilibrium transport properties of a parallel double
quantum dot in terms of its full counting statistics (FCS). The parameters of
the setup are assumed to be such that both subsystems are driven into the Kondo
regime. After a series of transformations the Hamiltonian is then mapped onto a
Majorana resonant level model, which effectively describes the Toulouse point
of the respective double impurity two-terminal Kondo model. Its FCS is then
obtained at arbitrary constellation of voltage, temperature, and local magnetic
fields. We identify two different transport processes corresponding to single
electron tunneling as well as an electron pair process and give the respective
effective transport coefficients. In the most universal linear response regime
the FCS turns out to be of a binomial shape with an effective transmission
coefficient. Furthermore, we find a complete transport suppression
(antiresonance) at a certain parameter constellation, which is similar to the
one found in the noninteracting quantum dots. By an explicit expansion around
the Toulouse point we show that the antiresonance is universal and should be
observable in the generic Kondo dot setup. We discuss experimental implications
of our predictions as well as possible routes for generalizations of our
approach.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-29911111.0864 | Soft gluon resummation for slepton pair-production
hep-ph
We report on recent results on the differential cross section for slepton
pair-production at hadron colliders. We use an approach to threshold
resummation, based on soft-collinear effective theory, to quantify the
dynamical enhancement of the partonic threshold region. We evaluate the
resummed invariant mass distribution and total cross section at
next-to-next-to-next-to-leading logarithmic order, and match the result onto
next-to-leading order calculation.
| arxiv topic:hep-ph |
arxiv_dataset-29921111.0964 | Recruitment dynamics in adaptive social networks
q-bio.PE
We model recruitment in adaptive social networks in the presence of birth and
death processes. Recruitment is characterized by nodes changing their status to
that of the recruiting class as a result of contact with recruiting nodes. Only
a susceptible subset of nodes can be recruited. The recruiting individuals may
adapt their connections in order to improve recruitment capabilities, thus
changing the network structure adaptively. We derive a mean field theory to
predict the dependence of the growth threshold of the recruiting class on the
adaptation parameter. Furthermore, we investigate the effect of adaptation on
the recruitment level, as well as on network topology. The theoretical
predictions are compared with direct simulations of the full system. We
identify two parameter regimes with qualitatively different bifurcation
diagrams depending on whether nodes become susceptible frequently (multiple
times in their lifetime) or rarely (much less than once per lifetime).
| arxiv topic:q-bio.PE |
arxiv_dataset-29931111.1064 | The typical Turing degree
math.LO
The Turing degree of a real measures the computational difficulty of
producing its binary expansion. Since Turing degrees are tailsets, it follows
from Kolmogorov's 0-1 law that for any property which may or may not be
satisfied by any given Turing degree, the satisfying class will either be of
Lebesgue measure 0 or 1, so long as it is measurable. So either the
\emph{typical} degree satisfies the property, or else the typical degree
satisfies its negation. Further, there is then some level of randomness
sufficient to ensure typicality in this regard. A similar analysis can be made
in terms of Baire category, where a standard form of genericity now plays the
role that randomness plays in the context of measure.
We describe and prove a number of results in a programme of research which
aims to establish the properties of the typical Turing degree, where typicality
is gauged either in terms of Lebesgue measure or Baire category.
| arxiv topic:math.LO |
arxiv_dataset-29941111.1164 | Thermal Conductance of Ballistic Point Contacts
cond-mat.mes-hall
We study the thermal conductance of ballistic point contacts. These contacts
are realized as few nanometer long pillars in so called air-gap
heterostructures (AGHs). The pillar length being much smaller that the mean
free path of the phonons up to room temperature. Due to the small dimension and
the low density of the pillars the thermal conductance of the AGHs is several
orders of magnitude reduced in comparison to bulk structures. The measurement
results are in quantitative agreement with a simple model that based on the
Boltzmann transport equation.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-29951111.1264 | Unabridged table of reflective lattices of rank 3
math.GR math.NT
This is the unabridged table of all 8595 rank three reflective Lorentzian
lattices, intended as a supplement to the author's paper classifying them. The
abridged table in that paper is complete too, but less explicit, so the main
purpose of this document is archival. The TeX sourcecode is simultaneously a
Perl script, which when run prints out all the lattices in computer-readable
format.
| arxiv topic:math.GR math.NT |
arxiv_dataset-29961111.1364 | Quantal effects and MaxEnt
quant-ph
Convex operational models (COMs) are considered as great extrapolations to
larger settings of any statistical theory. In this article we generalize the
maximum entropy principle (MaxEnt) of Jaynes' to any COM. After expressing
Max-Ent in a geometrical and latttice theoretical setting, we are able to cast
it for any COM. This scope-amplification opens the door to a new
systematization of the principle and sheds light into its geometrical
structure.
| arxiv topic:quant-ph |
arxiv_dataset-29971111.1464 | Generalised k-Steiner Tree Problems in Normed Planes
math.CO cs.DS
The 1-Steiner tree problem, the problem of constructing a Steiner minimum
tree containing at most one Steiner point, has been solved in the Euclidean
plane by Georgakopoulos and Papadimitriou using plane subdivisions called
oriented Dirichlet cell partitions. Their algorithm produces an optimal
solution within $O(n^2)$ time. In this paper we generalise their approach in
order to solve the $k$-Steiner tree problem, in which the Steiner minimum tree
may contain up to $k$ Steiner points for a given constant $k$. We also extend
their approach further to encompass other normed planes, and to solve a much
wider class of problems, including the $k$-bottleneck Steiner tree problem and
other generalised $k$-Steiner tree problems. We show that, for any fixed $k$,
such problems can be solved in $O(n^{2k})$ time.
| arxiv topic:math.CO cs.DS |
arxiv_dataset-29981111.1564 | Particle Swarm Optimization Framework for Low Power Testing of VLSI
Circuits
cs.NE
Power dissipation in sequential circuits is due to increased toggling count
of Circuit under Test, which depends upon test vectors applied. If successive
test vectors sequences have more toggling nature then it is sure that toggling
rate of flip flops is higher. Higher toggling for flip flops results more power
dissipation. To overcome this problem, one method is to use GA to have test
vectors of high fault coverage in short interval, followed by Hamming distance
management on test patterns. This approach is time consuming and needs more
efforts. Another method which is purposed in this paper is a PSO based Frame
Work to optimize power dissipation. Here target is to set the entire test
vector in a frame for time period 'T', so that the frame consists of all those
vectors strings which not only provide high fault coverage but also arrange
vectors in frame to produce minimum toggling.
| arxiv topic:cs.NE |
arxiv_dataset-29991111.1664 | Unconditionality, Fourier multipliers and Schur multipliers
math.FA math.OA
Let $G$ be an infinite locally compact abelian group. If $X$ is Banach space,
we show that if every bounded Fourier multiplier $T$ on $L^2(G)$ has the
property that $T\ot Id_X$ is bounded on $L^2(G,X)$ then the Banach space $X$ is
isomorphic to a Hilbert space. Moreover, if $1<p<\infty$, $p\not=2$, we prove
that there exists a bounded Fourier multiplier on $L^p(G)$ which is not
completely bounded. Finally, we examine unconditionality from the point of view
of Schur multipliers. More precisely, we give several necessary and sufficient
conditions to determine if an operator space is completely isomorphic to an
operator Hilbert space.
| arxiv topic:math.FA math.OA |
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