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arxiv_dataset-800808.3868 | QED calculation of transition probabilities in two-electron ions
physics.atom-ph
Accurate QED calculation of transition probabilities for the low-lying
two-electron configurations of multicharged ions is presented. The calculation
is performed for the nondegenerate states $(1s2s) 3S1$, $(1s2p_{3/2}) 3P2$ ($M
1$ and $M 2$ transitions, respectively) and for the quasidegenerate states
$(1s2p) 1P1$, $(1s2p) 3P1$ ($E 1$ transitions) decaying to the ground state
$(1s1s) 1S0$. Two-electron ions with nuclear charge numbers $Z=10-92$ are
considered. The line profile approach is employed for the description of the
process in multicharged ions within the framework of QED.
| arxiv topic:physics.atom-ph |
arxiv_dataset-801808.3968 | XAX: a multi-ton, multi-target detection system for dark matter, double
beta decay and pp solar neutrinos
astro-ph
A multi-target detection system XAX, comprising concentric 10 ton targets of
136Xe and 129/131Xe, together with a geometrically similar or larger target of
liquid Ar, is described. Each is configured as a two-phase
scintillation/ionization TPC detector, enhanced by a full 4pi array of
ultra-low radioactivity Quartz Photon Intensifying Detectors (QUPIDs) replacing
the conventional photomultipliers for detection of scintillation light. It is
shown that background levels in XAX can be reduced to the level required for
dark matter particle (WIMP) mass measurement at a 10^-10 pb WIMP-nucleon cross
section, with single-event sensitivity below 10^-11 pb. The use of multiple
target elements allows for confirmation of the A^2 dependence of a coherent
cross section, and the different Xe isotopes provide information on the
spin-dependence of the dark matter interaction. The event rates observed by Xe
and Ar would modulate annually with opposite phases from each other for WIMP
mass >~100 GeV/c^2. The large target mass of 136Xe and high degree of
background reduction allow neutrinoless double beta decay to be observed with
lifetimes of 10^27-10^28 years, corresponding to the Majorana neutrino mass
range 0.01-0.1 eV, the most likely range from observed neutrino mass
differences. The use of a 136Xe-depleted 129/131Xe target will also allow
measurement of the pp solar neutrino spectrum to a precision of 1-2%.
| arxiv topic:astro-ph |
arxiv_dataset-802808.4068 | Method of accelerator search for dark matter
hep-ex physics.ins-det
A method to search for dark matter by studying the interaction of accelerator
beam particles with residual gas in dependence on gas pressure is proposed. The
sensitivity of the method is estimated.
| arxiv topic:hep-ex physics.ins-det |
arxiv_dataset-803809.0008 | On the Theoretical Possibility of Quantum Visual Information Transfer to
the Human Brain
quant-ph q-bio.NC
The feasibility of wave function collapse in the human brain has been the
subject of vigorous scientific debates since the advent of quantum theory.
Scientists like Von Neumann, London, Bauer and Wigner (initially) believed that
wave function collapse occurs in the brain or is caused by the mind of the
observer. It is a legitimate question to ask how human brain can receive subtle
external visual quantum information intact when it must pass through very noisy
and complex pathways from the eye to the brain? There are several approaches to
investigate information processing in the brain, each of which presents a
different set of conclusions. Penrose and Hameroff have hypothesized that there
is quantum information processing inside the human brain whose material
substrate involves microtubules and consciousness is the result of a collective
wavefunction collapse occurring in these structures. Conversely, Tegmark stated
that owing to thermal decoherence there cannot be any quantum processing in
neurons of the brain and processing in the brain must be classical for
cognitive processes. However, Rosa and Faber presented an argument for a middle
way which shows that none of the previous authors are completely right and
despite the presence of decoherence, it is still possible to consider the brain
to be a quantum system. Additionally, Thaheld, has concluded that quantum
states of photons do collapse in the human eye and there is no possibility for
collapse of visual quantum states in the brain and thus there is no possibility
for the quantum state reduction in the brain. In this paper we conclude that if
we accept the main essence of the above approaches taken together, each of them
can provide a different part of a teleportation mechanism.
| arxiv topic:quant-ph q-bio.NC |
arxiv_dataset-804809.0108 | Bodies of zero resistance and bodies invisible in one direction
math.DS
We consider a body in a parallel flow of non-interacting particles. The
interaction of particles with the body is perfectly elastic. We introduce the
notions of a body of zero resistance, a body that leaves no trace, and an
invisible body, and prove that all such bodies do exist.
| arxiv topic:math.DS |
arxiv_dataset-805809.0208 | Subspace Techniques for Radio-Astronomical Data Enhancement
astro-ph
Radio astronomical observations have very poor signal to noise ratios, unlike
in other disciplines. On the other hand, it is possible to observe the object
of interest for long time intervals as well as using a wider bandwidth.
Traditionally, by averaging in time and in frequency, it has been possible to
improve the signal to noise ratio of astronomical observations to improve the
dynamic range. This is possible due to the inherent assumption that the object
of interest in the sky is invariant over time and the frequency range of
observation. However, in reality this assumption does not hold, due to
intrinsic variation of the sky as well as due to errors generated by the
instrument. In this paper, we shall discuss an alternative to averaging of
images, without ignoring subtle changes in the observed data over time and
frequency, using subspace decomposition. By separation of data to signal and
noise subspaces, not only would this improve the quality of the data, but also
enable us to detect faint artifacts due to calibration errors, interference
etc.
| arxiv topic:astro-ph |
arxiv_dataset-806809.0308 | Issues in joint SZ and optical cluster finding
astro-ph
We apply simple optical and SZ cluster finders to mock galaxy catalogues and
SZ flux maps created from dark matter halos in a (1 Gpc/h)^3 dark matter
simulation, at redshifts 0.5 and 0.9. At each redshift, the two catalogues are
then combined to assess how well they can improve each other, and compared to
several variants of catalogues made using SZ flux and galaxy information
simultaneously. We use several different criteria to compare the catalogues,
and illustrate some of the tradeoffs which arise in tuning the galaxy cluster
finders with respect to these criteria. We detail many of the resulting
improvements and issues which arise in comparing and combining these two types
of data sets.
| arxiv topic:astro-ph |
arxiv_dataset-807809.0408 | The charge conjugation quantum number in multiquark systems
hep-ph
We discuss the charge conjugation quantum number for tetraquarks or
meson-meson molecules, seen as possible interpretations of the newly found
$XYZ$ charmonium-like resonances.
| arxiv topic:hep-ph |
arxiv_dataset-808809.0508 | The properties of the host galaxy and the immediate environment of GRB
980425 / SN 1998bw from the multi-wavelength spectral energy distribution
astro-ph
We present an analysis of the spectral energy distribution (SED) of the
galaxy ESO 184-G82, the host of the closest known long gamma-ray burst (GRB)
980425 and its associated supernova (SN) 1998bw. We use our observations
obtained at the Australia Telescope Compact Array (the third >3 sigma radio
detection of a GRB host) as well as archival infrared and ultraviolet (UV)
observations to estimate its star formation state. We find that ESO 184-G82 has
a UV star formation rate (SFR) and stellar mass consistent with the population
of cosmological GRB hosts and of local dwarf galaxies. However, it has a higher
specific SFR (per unit stellar mass) than luminous spiral galaxies. The mass of
ESO 184-G82 is dominated by an older stellar population in contrast to the
majority of GRB hosts. The Wolf-Rayet region ~800 pc from the SN site
experienced a starburst episode during which the majority of its stellar
population was built up. Unlike that of the entire galaxy, its SED is similar
to those of cosmological submillimeter/radio-bright GRB hosts with hot dust
content. These findings add to the picture that in general, the environments of
GRBs on 1-3 kpc scales are associated with high specific SFR and hot dust.
| arxiv topic:astro-ph |
arxiv_dataset-809809.0608 | Theoretical constraints on the rare tau decays in the MSSM
hep-ph
The Minimal Supersymmetric Standard Model contains in general sources of tau
lepton flavour violation which induce the rare decays tau --> mu gamma and tau
--> e gamma. We argue in this paper that the observation of both rare processes
would imply a lower bound on the radiative muon decay of the form BR(mu --> e
gamma) > C BR(tau --> mu gamma) BR(tau --> e gamma). We estimate the size of
the constant C without specifying the origin of the tau flavour violation in
the supersymmetric model and we discuss the implications of our bound for
future searches of rare lepton decays. In particular, we show that, for a wide
class of models, present B-factories could discover either tau --> mu gamma or
tau --> e gamma, but not both. We also derive for completeness the constant C
in the most general setup, pursuing an effective theory approach.
| arxiv topic:hep-ph |
arxiv_dataset-810809.0708 | Relativistisk Rapsodi
physics.gen-ph
The essay presents Special Relativity (SR) from historical and conceptual
points of view. It also touches on some attempts to go beyond SR. However,
still more than 100 years old SR seems as vigorous as ever and no serious
challenger for a better local theory of spacetime is in sight yet. This
preliminary version of the essay is mainly in Scandinavian. Dictionary: rum =
space; tid = time.
| arxiv topic:physics.gen-ph |
arxiv_dataset-811809.0808 | Characteristic Classes on Grassmann Manifolds
math.FA
In this paper, we use characteristic classes of the canonical vector bundles
and the Poincar\' {e} dualality to study the structure of the real homology and
cohomology groups of oriented Grassmann manifold $G(k, n)$. Show that for $k=2$
or $n\leq 8$, the cohomology groups $H^*(G(k,n),{\bf R})$ are generated by the
first Pontrjagin class, the Euler classes of the canonical vector bundles. In
these cases, the Poincar\' {e} dualality: $H^q(G(k,n),{\bf R}) \to
H_{k(n-k)-q}(G(k,n),{\bf R})$ can be given explicitly.
| arxiv topic:math.FA |
arxiv_dataset-812809.0908 | Reduced Complexity Demodulation and Equalization Scheme for Differential
Impulse Radio UWB Systems with ISI
cs.IT math.IT
In this paper, we consider the demodulation and equalization problem of
differential Impulse Radio (IR) Ultra-WideBand (UWB) Systems with
Inter-Symbol-Interference (ISI). The differential IR UWB systems have been
extensively discussed recently. The advantage of differential IR UWB systems
include simple receiver frontend structure. One challenge in the demodulation
and equalization of such systems with ISI is that the systems have a rather
complex model. The input and output signals of the systems follow a
second-order Volterra model. Furthermore, the noise at the output is data
dependent. In this paper, we propose a reduced-complexity joint demodulation
and equalization algorithm. The algorithm is based on reformulating the nearest
neighborhood decoding problem into a mixed quadratic programming and utilizing
a semi-definite relaxation. The numerical results show that the proposed
demodulation and equalization algorithm has low computational complexity, and
at the same time, has almost the same error probability performance compared
with the maximal likelihood decoding algorithm.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-813809.1008 | Dynamics of Bianchi type I solutions of the Einstein equations with
anisotropic matter
gr-qc
We analyze the global dynamics of Bianchi type I solutions of the Einstein
equations with anisotropic matter. The matter model is not specified explicitly
but only through a set of mild and physically motivated assumptions; thereby
our analysis covers matter models as different from each other as, e.g.,
collisionless matter, elastic matter and magnetic fields. The main result we
prove is the existence of an `anisotropy classification' for the asymptotic
behaviour of Bianchi type I cosmologies. The type of asymptotic behaviour of
generic solutions is determined by one single parameter that describes certain
properties of the anisotropic matter model under extreme conditions. The
anisotropy classification comprises the following types. The convergent type
\Aplus: Each solution converges to a Kasner solution as the singularity is
approached and each Kasner solution is a possible past asymptotic state. The
convergent types \Bplus and \Cplus: Each solution converges to a Kasner
solution as the singularity is approached; however, the set of Kasner solutions
that are possible past asymptotic states is restricted. The oscillatory type
\Dplus: Each solution oscillates between different Kasner solutions as the
singularity is approached. Furthermore, we investigate non-generic asymptotic
behaviour and the future asymptotic behaviour of solutions.
| arxiv topic:gr-qc |
arxiv_dataset-814809.1108 | Prevalence of High X-ray Obscuring Columns among AGN that Host H$_2$O
Masers
astro-ph
Of 104 AGN known to exhibit H$_2$O maser emission, X-ray data that enable
estimation of column densities, or lower limits, are available for 42.
Contributing to this, we report analysis of new and archival X-ray data for 8
galaxies and collation of values for three more. Maser emission is indicative
of large columns of cold gas, and in five of the eight new cases, maser spectra
point toward origins in accretion disks viewed close-to edge-on (a.k.a.
"disk-maser" systems). In these, we detect hard continuum and Fe K$\alpha$
emission with equivalent widths on the order of 1 keV, which is consistent with
Compton reflection, fluorescence by cold material, and obscuring columns $\ga
10^{24}$ cm$^{-2}$. Reviewing the full sample of 42, 95% exhibit N$_{\rm H}
>10^{23}$ cm$^{-2}$ and 60% exhibit N$_{\rm H} >10^{24}$ cm$^{-2}$. Half of
these are now recognized to be disk masers (up from 13); in this sub-sample,
which is likely to be more homogeneous vis-\'a-vis the origin of maser
emission, 76% exhibit N$_{\rm H} >10^{24}$ cm$^{-2}$. The probability of a
common parent distribution of columns for disk-masers and other AGN masers is
<3%. Because ground-based surveys of AGN to detect new disk masers are
relatively unbiased with respect to X-ray brightness and comparatively
inexpensive, they may also be efficient guides for the sensitive pointed X-ray
observations required to identify Compton-thick objects outside of shallow
surveys.
| arxiv topic:astro-ph |
arxiv_dataset-815809.1208 | Bounds on the Capacity of the Relay Channel with States at the Source
cs.IT math.IT
This paper has been withdrawn by the authors
| arxiv topic:cs.IT math.IT |
arxiv_dataset-816809.1308 | Graph-theoretic criteria for injectivity and unique equilibria in
general chemical reaction systems
math.DS math.CO
In this paper we discuss the question of how to decide when a general
chemical reaction system is incapable of admitting multiple equilibria,
regardless of parameter values such as reaction rate constants, and regardless
of the type of chemical kinetics, such as mass-action kinetics,
Michaelis-Menten kinetics, etc. Our results relate previously described linear
algebraic and graph-theoretic conditions for injectivity of chemical reaction
systems. After developing a translation between the two formalisms, we show
that a graph-theoretic test developed earlier in the context of systems with
mass action kinetics, can be applied to reaction systems with arbitrary
kinetics. The test, which is easy to implement algorithmically, and can often
be decided without the need for any computation, rules out the possibility of
multiple equilibria for the systems in question.
| arxiv topic:math.DS math.CO |
arxiv_dataset-817809.1408 | Classification of BPS equations in higher dimensions
hep-th
We systematically classify all possible Bogomol'nyi-Prasad-Sommerfield (BPS)
equations in Euclidean dimension $d\leq8$. We discuss symmetries of BPS
equations and their connection with the self-dual Yang-Mills equations. Also,
we present a general method allowing to obtain the BPS equations in any
dimension. In addition, we find all BPS equations in the Minkowski space of
dimension $d\leq6$ and apply the obtained results to the supersymmetric
Yang-Mills theories. In conclusion, we discuss the possibility of using the
classification to construct soliton solutions of the low-energy effective
theory of the heterotic string.
| arxiv topic:hep-th |
arxiv_dataset-818809.1508 | Fermion Tunneling Beyond Semiclassical Approximation
hep-th gr-qc
Applying the Hamilton-Jacobi method beyond the semiclassical approximation
prescribed in \cite{Majhi3} for the scalar particle, Hawking radiation as
tunneling of Dirac particle through an event horizon is analysed. We show that,
as before, all quantum corrections in the single particle action are
proportional to the usual semiclassical contribution. We also compute the
modifications to the Hawking temperature and Bekenstein-Hawking entropy for the
Schwarzschild black hole. Finally, the coefficient of the logarithmic
correction to entropy is shown to be related with the trace anomaly.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-819809.1608 | HST observations of the quasar PKS 0637-752: equipartition
electron-proton jet from the most complete spectral coverage to date
astro-ph
We present new NICMOS and ACS observations of the quasar jet PKS 0637-752,
and we use them, together with existing multiwavelength observations, to
produce the most complete spectral coverage of the source to date. We explore
the implications of these observations in the context of models for the jet
X-ray emission. By relaxing the assumption of equipartition, we undertake an
exhaustive study of the parameter space for external Compton off the CMB
(EC/CMB) model. We find that the multiwavelength observations exclude a
magnetic field dominated jet. Using the method proposed by Georganopoulos et
al. (2005) for probing the jet matter content we show that protons are needed
for practically all jet configurations, extending a previous application of the
method by Uchiyama et al. (2005) that was based on exploring three particular
jet configurations. We also show that equipartition is the only configuration
that can reproduce the observations and have one proton per radiating lepton.
We finally present a rather model - independent argument that the jet has a
spine-sheath flow pattern, with the spine being faster and emitting most of the
IR-optical-X-ray emission.
| arxiv topic:astro-ph |
arxiv_dataset-820809.1708 | Radiation-Dominated Disks Are Thermally Stable
astro-ph
When the accretion rate is more than a small fraction of Eddington, the inner
regions of accretion disks around black holes are expected to be
radiation-dominated. However, in the alpha-model, these regions are also
expected to be thermally unstable. In this paper, we report two 3-d radiation
MHD simulations of a vertically-stratified shearing box in which the ratio of
radiation to gas pressure is ~ 10, and yet no thermal runaway occurs over a
timespan ~ 40 cooling times. Where the time-averaged dissipation rate is
greater than the critical dissipation rate that creates hydrostatic equilibrium
by diffusive radiation flux, the time-averaged radiation flux is held to the
critical value, with the excess dissipated energy transported by radiative
advection. Although the stress and total pressure are well-correlated as
predicted by the alpha-model, we show that stress fluctuations precede pressure
fluctuations, contrary to the usual supposition that the pressure controls the
saturation level of the magnetic energy. This fact explains the thermal
stability. Using a simple toy-model, we show that independently-generated
magnetic fluctuations can drive radiation pressure fluctuations, creating a
correlation between the two while maintaining thermal stability.
| arxiv topic:astro-ph |
arxiv_dataset-821809.1808 | New examples of $c_0$-saturated Banach spaces
math.FA
For every $ 1 < p < \infty $ an isomorphically polyhedral Banach space $E_p$
is constructed having an unconditional basis and admitting a quotient
isomorphic to $\ell_p$. It is also shown that $E_p$ is not isomorphic to a
subspace of a $C(K)$ space for every countable and compact metric space $K$.
| arxiv topic:math.FA |
arxiv_dataset-822809.1908 | First steps toward the geometry of cophylogeny
q-bio.PE
Here we introduce researchers in algebraic biology to the exciting new field
of cophylogenetics. Cophylogenetics is the study of concomitantly evolving
organisms (or genes), such as host and parasite species. Thus the natural
objects of study in cophylogenetics are tuples of related trees, instead of
individual trees. We review various research topics in algebraic statistics for
phylogenetics, and propose analogs for cophylogenetics. In particular we
propose spaces of cophylogenetic trees, cophylogenetic reconstruction, and
cophylogenetic invariants. We conclude with open problems.
| arxiv topic:q-bio.PE |
arxiv_dataset-823809.2008 | Modeling of the evolution of dielectric loss with processing temperature
in ferroelectric and dielectric thin oxide films
cond-mat.mtrl-sci cond-mat.other
It was experimentally found that the evolution of dielectric loss with
processing temperature displays a common trend in ferroelectric and dielectric
thin oxide films: firstly an increase and then a decrease in dielectric loss
when the processing temperature is gradually raised. Such a dielectric response
of ferroelectric/dielectric thin films has been theoretically addressed in this
work. We propose that at the initial stage of the crystallization process in
thin films, the transformation from amorphous to crystalline phase should
increase substantially the dielectric loss; then, with further increase in the
processing temperature, the coalescent growth of small crystalline grains into
big ones could be helpful in reducing the dielectric loss by lowering grain
boundary densities. The obtained experimental data for (Ba,Sr)TiO3 thin films
with 500 nm in thickness were analyzed in terms of the model developed and
shown to be in a reasonable agreement with the theoretical results.
| arxiv topic:cond-mat.mtrl-sci cond-mat.other |
arxiv_dataset-824809.2108 | Singe ferroelectric and chiral magnetic domain of single-crystalline
BiFeO$_3$ in an electric field
cond-mat.mtrl-sci
We report polarized neutron scattering and piezoresponse force microscopy
studies of millimeter-sized single crystals of multiferroic BiFeO$_3$. The
crystals, grown below the Curie temperature, consist of a single ferroelectric
domain. Two unique electric polarization directions, as well as the populations
of equivalent spiral magnetic domains, can be switched reversibly by an
electric field. A ferroelectric monodomain with a single-$q$ single-helicity
spin spiral can be obtained. This level of control, so far unachievable in thin
films, makes single-crystal BiFeO$_3$ a promising object for multiferroics
research.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-825809.2208 | Higher-order-in-spin interaction Hamiltonians for binary black holes
from Poincar\'e invariance
gr-qc
The fulfillment of the space-asymptotic Poincar\'e algebra is used to derive
new higher-order-in-spin interaction Hamiltonians for binary black holes in the
Arnowitt-Deser-Misner canonical formalism almost completing the set of the
formally $1/c^4$ spin-interaction Hamiltonians involving nonlinear spin terms.
To linear order in $G$, the expressions for the $S^3p$- and the
$S^2p^2$-Hamiltonians are completed. It is also shown that there are no quartic
nonlinear $S^4$-Hamiltonians to linear order in $G$.
| arxiv topic:gr-qc |
arxiv_dataset-826809.2308 | Virtual retractions, conjugacy separability and omnipotence
math.GR math.GT
We use wreath products to provide criteria for a group to be conjugacy
separable or omnipotent. These criteria are in terms of virtual retractions
onto cyclic subgroups. We give two applications: a straightforward topological
proof of the theorem of Stebe that infinite-order elements of Fuchsian groups
(of the first type) are conjugacy distinguished, and a proof that surface
groups are omnipotent.
| arxiv topic:math.GR math.GT |
arxiv_dataset-827809.2408 | Normal automorphisms of relatively hyperbolic groups
math.GR math.GT
An automorphism $\alpha$ of a group $G$ is normal if it fixes every normal
subgroup of $G$ setwise. We give an algebraic description of normal
automorphisms of relatively hyperbolic groups. In particular, we prove that for
any relatively hyperbolic group $G$, $Inn(G)$ has finite index in the subgroup
$Aut_n(G)$ of normal automorphisms. If, in addition, $G$ is non-elementary and
has no non-trivial finite normal subgroups, then $Aut_n(G)=Inn(G)$. As an
application, we show that $Out(G)$ is residually finite for every finitely
generated residually finite group $G$ with more than one end.
| arxiv topic:math.GR math.GT |
arxiv_dataset-828809.2508 | A fast approach for overcomplete sparse decomposition based on smoothed
L0 norm
cs.IT math.IT
In this paper, a fast algorithm for overcomplete sparse decomposition, called
SL0, is proposed. The algorithm is essentially a method for obtaining sparse
solutions of underdetermined systems of linear equations, and its applications
include underdetermined Sparse Component Analysis (SCA), atomic decomposition
on overcomplete dictionaries, compressed sensing, and decoding real field
codes. Contrary to previous methods, which usually solve this problem by
minimizing the L1 norm using Linear Programming (LP) techniques, our algorithm
tries to directly minimize the L0 norm. It is experimentally shown that the
proposed algorithm is about two to three orders of magnitude faster than the
state-of-the-art interior-point LP solvers, while providing the same (or
better) accuracy.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-829809.2608 | High-Redshift Starbursting Dwarf Galaxies Revealed by GRB Afterglows
astro-ph
We present a study of 15 long-duration gamma-ray burst (GRB) host galaxies at
z>2. The GRBs are selected with available early-time afterglow spectra in order
to compare interstellar medium (ISM) absorption-line properties with stellar
properties of the host galaxies. In addition to five previously studied hosts,
we consider new detections for the host galaxies of GRB050820 and GRB060206 and
place 2-sigma upper limits to the luminosities of the remaining unidentified
hosts. We examine the nature of the host galaxy population and find that (1)
the UV luminosity distribution of GRB host galaxies is consistent with
expectations from a UV luminosity weighted random galaxy population with a
median luminosity of <L(UV)>=0.1 L*; (2) there exists a moderate correlation
between UV luminosity and SiII 1526 absorption width, which together with the
observed large line widths of W(1526)>1.5 Ang for a large fraction of the
objects suggests a galactic outflow driven velocity field in the host galaxies;
(3) there is tentative evidence for a trend of declining ISM metallicity with
decreasing galaxy luminosity in the star-forming galaxy population at z=2-4;
(4) the interstellar UV radiation field is found ~ 35-350 times higher in GRB
hosts than the Galactic mean value; and (5) additional galaxies are found at <
2" from the GRB host in all fields with known presence of strong MgII
absorbers, but no additional faint galaxies are found at < 2" in fields without
strong MgII absorbers. Our study confirms that the GRB host galaxies (with
known optical afterglows) are representative of unobscured star-forming
galaxies at z>2, and demonstrates that high spatial resolution images are
necessary for an accurate identification of GRB host galaxies in the presence
of strong intervening absorbers.
| arxiv topic:astro-ph |
arxiv_dataset-830809.2708 | Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
hep-ph
HYDJET++ is a Monte-Carlo event generator for simulation of relativistic
heavy ion AA collisions considered as a superposition of the soft, hydro-type
state and the hard state resulting from multi-parton fragmentation. This model
is the development and continuation of HYDJET event generator (Lokhtin &
Snigirev, 2006, EPJC, 45, 211). The main program is written in the
object-oriented C++ language under the ROOT environment. The hard part of
HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is
included in the generator structure as a separate directory. The soft part of
HYDJET++ event is the "thermal" hadronic state generated on the chemical and
thermal freeze-out hypersurfaces obtained from the parameterization of
relativistic hydrodynamics with preset freeze-out conditions. It includes the
longitudinal, radial and elliptic flow effects and the decays of hadronic
resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code
FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is
adapted to HYDJET++. It is designed for studying the multi-particle production
in a wide energy range of heavy ion experimental facilities: from FAIR and NICA
to RHIC and LHC.
| arxiv topic:hep-ph |
arxiv_dataset-831809.2808 | Late stage, non-equilibrium dynamics in the dipolar Ising model
cond-mat.mtrl-sci cond-mat.stat-mech
Magnetic domain structures are a fascinating area of study with interest
deriving both from technological applications and fundamental scientific
questions. The nature of the striped magnetic phases observed in ultra-thin
films is one such intriguing system. The non-equilibrium dynamics of such
systems as they evolve toward equilibrium has only recently become an area of
interest and previous work on model systems showed evidence of complex, slow
dynamics with glass-like properties as the stripes order mesoscopically. To aid
in the characterization of the observed phases and the nature of the
transitions observed in model systems we have developed an efficient method for
identifying clusters or domains in the spin system, where the clusters are
based on the stripe orientation. Thus we are able to track the growth and decay
of such clusters of stripes in a Monte Carlo simulation and observe directly
the nature of the slow dynamics. We have applied this method to consider the
growth and decay of ordered domains after a quench from a saturated magnetic
state to temperatures near and well below the critical temperature in the two
dimensional dipolar Ising model. We discuss our method of identifying stripe
domains or clusters of stripes within this model and present the results of our
investigations.
| arxiv topic:cond-mat.mtrl-sci cond-mat.stat-mech |
arxiv_dataset-832809.2908 | Elastic and Chemical Contributions to the Stability of Magnetic Surface
Alloys on Ru(0001)
cond-mat.mtrl-sci
We have used density functional theory to study the structural stability of
surface alloys. Our systems consist of a single pseudomorphic layer of
$M_xN_{1-x}$ on the Ru(0001) surface, where $M$ = Fe or Co, and $N$ = Pt, Au,
Ag, Cd, or Pb. Several of the combinations studied by us display a preference
for atomically mixed configurations over phase-segregated forms. We have also
performed further {\it ab initio} calculations to obtain the parameters
describing the elastic interactions between atoms in the alloy layer, including
the effective atomic sizes at the surface. We find that while elastic
interactions favor alloying for all the systems considered by us, in some cases
chemical interactions disfavor atomic mixing. We show that a simple criterion
(analogous to the Hume-Rothery first law for bulk alloys) need not necessarily
work for strain-stabilized surface alloys, because of the presence of
additional elastic contributions to the alloy heat of formation, that will tend
to oppose phase segregation.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-833809.3008 | The Brown Dwarf Kinematics Project (BDKP) I. Proper Motions and
Tangential Velocities for a Large Sample of Late-type M, L and T Dwarfs
astro-ph
We report proper motion measurements for 427 late-type M, L and T dwarfs, 332
of which have been measured for the first time. Combining these new proper
motions with previously published measurements yields a sample of 841 M7-T8
dwarfs. We combined parallax measurements or calculated spectrophotometric
distances and computed tangential velocities for the entire sample. We find
that kinematics for the full and volume-limited 20 pc samples are consistent
with those expected for the Galactic thin disk, with no significant differences
between late-type M, L, and T dwarfs. Applying an age-velocity relation we
conclude that the average kinematic age of the 20 pc sample of ultracool dwarfs
is older than recent kinematic estimates and more consistent with age results
calculated with population synthesis models. There is a statistically distinct
population of high tangential velocity sources whose kinematics suggest an even
older population of ultracool dwarfs belonging to either the Galactic thick
disk or halo. We isolate subsets of the entire sample, including low
surface-gravity dwarfs, unusually blue L dwarfs, and photometric outliers in
J-Ks color and investigate their kinematics. We find that the spectroscopically
distinct class of unusually blue L dwarfs has kinematics clearly consistent
with old age, implying that high surface-gravity and/or low metallicity may be
relevant to their spectral properties. The low surface-gravity dwarfs are
kinematically younger than the overall population, and the kinematics of the
red and blue ultracool dwarfs suggest ages that are younger and older than the
full sample, respectively. We also present a reduced proper motion diagram at
2MASS Ks for the entire population and find that a limit of H_Ks > 18 excludes
M dwarfs from the L and T dwarf population regardless of near-infrared color.
| arxiv topic:astro-ph |
arxiv_dataset-834809.3108 | The co-Riemannian Structure of Smooth Loop Spaces
math.DG
We construct a natural co-Riemannian structure on the manifold of smooth
loops in a Riemannian manifold. We show that the smooth loop space of a string
manifold is a per-Hilbert-Schmidt locally equivalent co-spin manifold and thus
admits a Dirac operator.
| arxiv topic:math.DG |
arxiv_dataset-835809.3208 | Evidence for a Photoevaporated Circumbinary Disk in Orion
astro-ph
We have found a photoevaporated disk in the Orion Nebula that includes a wide
binary. HST/ACS observations of the proplyd 124-132 show two point-like sources
separated by 0".15, or about 60 AU at the distance of Orion. The two sources
have nearly identical I and z magnitudes. We analyze the brightest component,
Source N, comparing the observed magnitudes with those predicted using a 1 Myr
Baraffe/NEXTGEN isochrone with different accretion luminosities and
extinctions. We find that a low mass (\simeq 0.04 M_\odot) brown dwarf ~1 Myr
old with mass accretion rate \log\dot{M}\simeq -10.3, typical for objects of
this mass, and about 2 magnitudes of visual extinction provides the best fit to
the data. This is the first observation of a circumbinary disk undergoing
photoevaporation and, if confirmed by spectroscopic observations, the first
direct detection of a wide substellar pair still accreting and enshrouded in
its circumbinary disk.
| arxiv topic:astro-ph |
arxiv_dataset-836809.3308 | Demonstrating Heisenberg-limited unambiguous phase estimation without
adaptive measurements
quant-ph
We derive, and experimentally demonstrate, an interferometric scheme for
unambiguous phase estimation with precision scaling at the Heisenberg limit
that does not require adaptive measurements. That is, with no prior knowledge
of the phase, we can obtain an estimate of the phase with a standard deviation
that is only a small constant factor larger than the minimum physically allowed
value. Our scheme resolves the phase ambiguity that exists when multiple passes
through a phase shift, or NOON states, are used to obtain improved phase
resolution. Like a recently introduced adaptive technique [Higgins et al 2007
Nature 450 393], our experiment uses multiple applications of the phase shift
on single photons. By not requiring adaptive measurements, but rather using a
predetermined measurement sequence, the present scheme is both conceptually
simpler and significantly easier to implement. Additionally, we demonstrate a
simplified adaptive scheme that also surpasses the standard quantum limit for
single passes.
| arxiv topic:quant-ph |
arxiv_dataset-837809.3408 | Controlling an actively-quenched single photon detector with bright
light
quant-ph physics.ins-det
We control using bright light an actively-quenched avalanche single-photon
detector. Actively-quenched detectors are commonly used for quantum key
distribution (QKD) in the visible and near-infrared range. This study shows
that these detectors are controllable by the same attack used to hack
passively-quenched and gated detectors. This demonstrates the generality of our
attack and its possible applicability to eavsdropping the full secret key of
all QKD systems using avalanche photodiodes (APDs). Moreover, the commercial
detector model we tested (PerkinElmer SPCM-AQR) exhibits two new blinding
mechanisms in addition to the previously observed thermal blinding of the APD,
namely: malfunctioning of the bias voltage control circuit, and overload of the
DC/DC converter biasing the APD. These two new technical loopholes found just
in one detector model suggest that this problem must be solved in general, by
incorporating generally imperfect detectors into the security proof for QKD.
| arxiv topic:quant-ph physics.ins-det |
arxiv_dataset-838809.3508 | Exploring the LHC medium with electromagnetic probes
nucl-ex
Heavy-ion collisions will enter a new era with the start of the CERN Large
Hadron Collider (LHC). A first short run with proton-proton collisions at the
injection energy of 0.9 TeV will be followed by a longer one with $pp$
collisions at 10 TeV. First Pb-Pb collisions at $\sqrt{s_{NN}}$=5.5 TeV will
take place in 2009. Three experiments (ALICE, ATLAS, and CMS) will study both
$pp$ and Pb-Pb collisions. A selection of results showing the capabilities of
the three experiments for the study of the LHC medium with electromagnetic
probes is presented.
| arxiv topic:nucl-ex |
arxiv_dataset-839809.3608 | Isothermic hypersurfaces in R^{n+1}
math.DG
A diagonal metric sum_{i=1}^n g_{ii} dx_i^2 is termed Guichard_k if
sum_{i=1}^{n-k}g_{ii}-sum_{i=n-k+1}^n g_{ii}=0. A hypersurface in R^{n+1} is
isothermic_k if it admits line of curvature co-ordinates such that its induced
metric is Guichard_k. Isothermic_1 surfaces in R^3 are the classical isothermic
surfaces in R^3. Both isothermic_k hypersurfaces in R^{n+1} and Guichard_k
orthogonal co-ordinate systems on R^n are invariant under conformal
transformations. A sequence of n isothermic_k hypersurfaces in R^{n+1}
(Guichard_k orthogonal co-ordinate systems on R^n resp.) is called a Combescure
sequence if the consecutive hypersurfaces (orthogonal co-ordinate systems
resp.) are related by Combescure transformations. We give a correspondence
between Combescure sequences of Guichard_k orthogonal co-ordinate systems on
R^n and solutions of the O(2n-k,k)/O(n)xO(n-k,k)-system, and a correspondence
between Combescure sequences of isothermic_k hypersurfaces in R^{n+1} and
solutions of the O(2n+1-k,k)/O(n+1)xO(n-k,k)-system, both being integrable
systems. Methods from soliton theory can therefore be used to construct
Christoffel, Ribaucour, and Lie transforms, and to describe the moduli spaces
of these geometric objects and their loop group symmetries.
| arxiv topic:math.DG |
arxiv_dataset-840809.3708 | Prospects for SUSY searches in CMS and ATLAS
hep-ex
We discuss how the CMS and ATLAS experiments are preparing for the analysis
of first LHC data with emphasis on the search for supersymmetry. We will show
the importance of the understanding of detector, trigger, reconstruction and
backgrounds, and we will present realistic estimates of the reach of CMS and
ATLAS.
| arxiv topic:hep-ex |
arxiv_dataset-841809.3808 | Universality of the hydrodynamic limit in AdS/CFT and the membrane
paradigm
hep-th gr-qc
We show that at the level of linear response the low frequency limit of a
strongly coupled field theory at finite temperature is determined by the
horizon geometry of its gravity dual, i.e. by the "membrane paradigm" fluid of
classical black hole mechanics. Thus generic boundary theory transport
coefficients can be expressed in terms of geometric quantities evaluated at the
horizon. When applied to the stress tensor this gives a simple, general proof
of the universality of the shear viscosity in terms of the universality of
gravitational couplings, and when applied to a conserved current it gives a new
general formula for the conductivity. Away from the low frequency limit the
behavior of the boundary theory fluid is no longer fully captured by the
horizon fluid even within the derivative expansion; instead we find a
nontrivial evolution from the horizon to the boundary. We derive flow equations
governing this evolution and apply them to the simple examples of charge and
momentum diffusion.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-842809.3908 | Optimal Energy Management Policies for Energy Harvesting Sensor Nodes
cs.NI
We study a sensor node with an energy harvesting source. The generated energy
can be stored in a buffer. The sensor node periodically senses a random field
and generates a packet. These packets are stored in a queue and transmitted
using the energy available at that time. We obtain energy management policies
that are throughput optimal, i.e., the data queue stays stable for the largest
possible data rate. Next we obtain energy management policies which minimize
the mean delay in the queue.We also compare performance of several easily
implementable sub-optimal energy management policies. A greedy policy is
identified which, in low SNR regime, is throughput optimal and also minimizes
mean delay.
| arxiv topic:cs.NI |
arxiv_dataset-843809.4008 | Cosmology With Many Light Scalar Fields: Stochastic Inflation and Loop
Corrections
hep-th astro-ph gr-qc
We explore the consequences of the existence of a very large number of light
scalar degrees of freedom in the early universe. We distinguish between
participator and spectator fields. The former have a small mass, and can
contribute to the inflationary dynamics; the latter are either strictly
massless or have a negligible VEV. In N-flation and generic assisted inflation
scenarios, inflation is a co-operative phenomenon driven by N participator
fields, none of which could drive inflation on their own. We review upper
bounds on N, as a function of the inflationary Hubble scale H. We then consider
stochastic and eternal inflation in models with N participator fields showing
that individual fields may evolve stochastically while the whole ensemble
behaves deterministically, and that a wide range of eternal inflationary
scenarios are possible in this regime. We then compute one-loop quantum
corrections to the inflationary power spectrum. These are largest with N
spectator fields and a single participator field, and the resulting bound on N
is always weaker than those obtained in other ways. We find that loop
corrections to the N-flation power spectrum do not scale with N, and thus place
no upper bound on the number of participator fields. This result also implies
that, at least to leading order, the theory behaves like a composite single
scalar field. In order to perform this calculation, we address a number of
issues associated with loop calculations in the Schwinger-Keldysh "in-in"
formalism.
| arxiv topic:hep-th astro-ph gr-qc |
arxiv_dataset-844809.4108 | The ADAPT Tool: From AADL Architectural Models to Stochastic Petri Nets
through Model Transformation
cs.SE
ADAPT is a tool that aims at easing the task of evaluating dependability
measures in the context of modern model driven engineering processes based on
AADL (Architecture Analysis and Design Language). Hence, its input is an AADL
architectural model annotated with dependability-related information. Its
output is a dependability evaluation model in the form of a Generalized
Stochastic Petri Net (GSPN). The latter can be processed by existing
dependability evaluation tools, to compute quantitative measures such as
reliability, availability, etc.. ADAPT interfaces OSATE (the Open Source AADL
Tool Environment) on the AADL side and SURF-2, on the dependability evaluation
side. In addition, ADAPT provides the GSPN in XML/XMI format, which represents
a gateway to other dependability evaluation tools, as the processing techniques
for XML files allow it to be easily converted to a tool-specific GSPN.
| arxiv topic:cs.SE |
arxiv_dataset-845809.4208 | Polarization measurements and their perspectives: PVLAS Phase II
hep-ex physics.ins-det
We sketch the proposal for a "PVLAS-Phase II" experiment. The main physics
goal is to achieve the first direct observation of non-linear effects in
electromagnetism predicted by QED and the measurement of the photon-photon
scattering cross section at low energies (1-2 eV). Physical processes such as
ALP and MCP production in a magnetic field could also be accessible if
sensitive enough operation is reached. The short term experimental strategy is
to compact as much as possible the dimensions of the apparatus in order to
bring noise sources under control and to attain a sufficient sensitivity. We
will also briefly mention future pespectives, such as a scheme to implement the
resonant regeneration principle for the detection of ALPs.
| arxiv topic:hep-ex physics.ins-det |
arxiv_dataset-846809.4308 | New method for extracting neutron structure functions from nuclear data
nucl-th hep-ex hep-ph nucl-ex
We propose a new method for extracting neutron structure functions from
inclusive structure functions of nuclei. Unlike earlier approaches, the new
method is applicable to both spin-averaged and spin-dependent structure
functions. We test the reliability of the method on unpolarized F_2 and
polarized g_1 structure functions of the deuteron in both the nucleon resonance
and deep inelastic regions. The new method is able to reproduce known input
functions of almost arbitrary shape to very good accuracy with only several
iterations.
| arxiv topic:nucl-th hep-ex hep-ph nucl-ex |
arxiv_dataset-847809.4408 | Euclidean Quantum Mechanics and Universal Nonlinear Filtering
math-ph math.MP
An important problem in applied science is the continuous nonlinear filtering
problem, i.e., the estimation of a Langevin state that is observed indirectly.
In this paper, it is shown that Euclidean quantum mechanics is closely related
to the continuous nonlinear filtering problem. The key is the configuration
space Feynman path integral representation of the fundamental solution of a
Fokker-Planck type of equation termed the Yau Equation of continuous-continuous
filtering. A corollary is the equivalence between nonlinear filtering problem
and a time-varying Schr\"odinger equation.
| arxiv topic:math-ph math.MP |
arxiv_dataset-848809.4508 | Dirac constraints in field theory and exterior differential systems
math-ph math.MP
The usual treatment of a (first order) classical field theory such as
electromagnetism has a little drawback: It has a primary constraint submanifold
that arise from the fact that the dynamics is governed by the antisymmetric
part of the jet variables. So it is natural to ask if there exists a
formulation of this kind of field theories which avoids this problem, retaining
the versatility of the known approach. The following paper deals with a family
of variational problems, namely, the so called non standard variational
problems, which intends to capture the data necessary to set up such a
formulation for field theories; moreover, we will formulate a multisymplectic
structure for the family of non standard variational problems, and we will
relate this with the (pre)symplectic structure arising on the space of sections
of the bundle of fields. In this setting the Dirac theory of constraints will
be studied, obtaining among other things a novel characterization of the
constraint manifold which arises in this theory, as generators of an exterior
differential system associated to the equations of motion and the chosen
slicing. Several examples of application of this formalism are discussed: Two
of them motivated from the physical point of view, that is, electromagnetism
and Poisson sigma models, and two examples of mathematical application. In the
case of electromagnetism, it is shown that this formulation avoids the problems
arising in the usual approach.
| arxiv topic:math-ph math.MP |
arxiv_dataset-849809.4608 | Photoabsorption off nuclei with self consistent vertex corrections
nucl-th
We study photoproduction off nuclei based on a self consistent and covariant
many body approach for the pion and isobar propagation in infinite nuclear
matter. For the first time the t-channel exchange of an in-medium pion is
evaluated in the presence of vertex correction effects consistently. In
particular the interference pattern with the s-channel in-medium nucleon and
isobar exchange contribution is considered. Electromagnetic gauge invariance is
kept as a consequence of various Ward identities obeyed by the computation.
Adjusting the set of Migdal parameters to the data set we predict an attractive
mass shift for the isobar of about 50 MeV at nuclear saturation density.
| arxiv topic:nucl-th |
arxiv_dataset-850809.4708 | Solution of the inverse problem in spherical gravitational wave
detectors using a model with independent bars
gr-qc
The direct detection of gravitational waves will provide valuable
astrophysical information about many celestial objects. The SCHENBERG has
already undergone its first test run. It is expected to have its first
scientific run soon. In this work a new data analysis approach is presented,
called method of independent bars, which can be used with SCHENBERG's data . We
test this method through the simulation of the detection of gravitational
waves. With this method we find the source's direction without the need to have
all six transducers operational. Also we show that the method is a
generalization of another one, already described in the literature, known as
the mode channels method.
| arxiv topic:gr-qc |
arxiv_dataset-851809.4808 | The first measurement of the top quark mass at CDF II in the lepton+jets
and dilepton channels simultaneously
hep-ex
We present a measurement of the mass of the top quark using data
corresponding to an integrated luminosity of 1.9fb^-1 of ppbar collisions
collected at sqrt{s}=1.96 TeV with the CDF II detector at Fermilab's Tevatron.
This is the first measurement of the top quark mass using top-antitop pair
candidate events in the lepton + jets and dilepton decay channels
simultaneously. We reconstruct two observables in each channel and use a
non-parametric kernel density estimation technique to derive two-dimensional
probability density functions from simulated signal and background samples. The
observables are the top quark mass and the invariant mass of two jets from the
W decay in the lepton + jets channel, and the top quark mass and the scalar sum
of transverse energy of the event in the dilepton channel. We perform a
simultaneous fit for the top quark mass and the jet energy scale, which is
constrained in situ by the hadronic W boson mass. Using 332 lepton + jets
candidate events and 144 dilepton candidate events, we measure the top quark
mass to be mtop=171.9 +/- 1.7 (stat. + JES) +/- 1.1 (syst.) GeV/c^2 = 171.9 +/-
2.0 GeV/c^2.
| arxiv topic:hep-ex |
arxiv_dataset-852809.4908 | The signature of the Ricci curvature of left invariant Riemannian
metrics on 4-dimensional Lie groups
math.DG
In this paper, we present the classification of all possible signatures of
the Ricci curvature of left-invariant Riemannian metrics on 4-dimensional Lie
groups and discuss some related questions.
| arxiv topic:math.DG |
arxiv_dataset-853809.5008 | Multi-Antenna Communication in Ad Hoc Networks: Achieving MIMO Gains
with SIMO Transmission
cs.IT math.IT
The benefit of multi-antenna receivers is investigated in wireless ad hoc
networks, and the main finding is that network throughput can be made to scale
linearly with the number of receive antennas nR even if each transmitting node
uses only a single antenna. This is in contrast to a large body of prior work
in single-user, multiuser, and ad hoc wireless networks that have shown linear
scaling is achievable when multiple receive and transmit antennas (i.e., MIMO
transmission) are employed, but that throughput increases logarithmically or
sublinearly with nR when only a single transmit antenna (i.e., SIMO
transmission) is used. The linear gain is achieved by using the receive degrees
of freedom to simultaneously suppress interference and increase the power of
the desired signal, and exploiting the subsequent performance benefit to
increase the density of simultaneous transmissions instead of the transmission
rate. This result is proven in the transmission capacity framework, which
presumes single-hop transmissions in the presence of randomly located
interferers, but it is also illustrated that the result holds under several
relaxations of the model, including imperfect channel knowledge, multihop
transmission, and regular networks (i.e., interferers are deterministically
located on grids).
| arxiv topic:cs.IT math.IT |
arxiv_dataset-854809.5108 | The discontinuous nature of the exchange-correlation functional --
critical for strongly correlated systems
cond-mat.str-el cond-mat.mtrl-sci
Standard approximations for the exchange-correlation functional have been
found to give big errors for the linearity condition of fractional charges,
leading to delocalization error, and the constancy condition of fractional
spins, leading to static correlation error. These two conditions are now
unified for states with both fractional charge and fractional spin: the exact
energy functional is a plane, linear along the fractional charge coordinate and
constant along the fractional spin coordinate with a line of discontinuity at
the integer. This sheds light on the nature of the derivative discontinuity and
calls for explicitly discontinuous functionals of the density or orbitals that
go beyond currently used smooth approximations. This is key for the application
of DFT to strongly correlated systems.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-855809.5208 | Nonthermal fixed points and the functional renormalization group
hep-th cond-mat.other hep-ph nucl-th
Nonthermal fixed points represent basic properties of quantum field theories,
in addition to vacuum or thermal equilibrium fixed points. The functional
renormalization group on a closed real-time path provides a common framework
for their description. For the example of an O(N) symmetric scalar theory it
reveals a hierarchy of fixed point solutions, with increasing complexity from
vacuum and thermal equilibrium to nonequilibrium.
| arxiv topic:hep-th cond-mat.other hep-ph nucl-th |
arxiv_dataset-856810.0021 | Detection of a Temperature Inversion in the Broadband Infrared Emission
Spectrum of TrES-4
astro-ph
We estimate the strength of the bandpass-integrated thermal emission from the
extrasolar planet TrES-4 at 3.6, 4.5, 5.8, and 8.0 micron using the Infrared
Array Camera (IRAC) on the Spitzer Space Telescope. We find relative eclipse
depths of 0.137 +/- 0.011%, 0.148 +/- 0.016%, 0.261 +/- 0.059%, and 0.318 +/-
0.044% in these four bandpasses, respectively. We also place a 2 sigma upper
limit of 0.37% on the depth of the secondary eclipse in the 16 micron IRS
peak-up array. These eclipse depths reveal that TrES-4 has an emission spectrum
similar to that of HD 209458b, which requires the presence of water emission
bands created by an thermal inversion layer high in the atmosphere in order to
explain the observed features. TrES-4 receives more radiation from its star
than HD 209458b and has a correspondingly higher effective temperature,
therefore the presence of a temperature inversion in this planet's atmosphere
lends support to the idea that inversions might be correlated with the
irradiance received by the planet. We find no evidence for any offset in the
timing of the secondary eclipse, and place a 3 sigma upper limit of
|ecos(omega)|<0.0058 where e is the planet's orbital eccentricity and omega is
the argument of pericenter. From this we conclude that tidal heating from
ongoing orbital circulatization is unlikely to be the explanation for TrES-4's
inflated radius.
| arxiv topic:astro-ph |
arxiv_dataset-857810.0121 | Modelling tri-bimaximal neutrino mixing
hep-ph
We model tri-bimaximal lepton mixing from first principles in a way that
avoids the problem of the vacuum alignment characteristic of such models. This
is achieved by using a softly broken A4 symmetry realized with an isotriplet
fermion, also triplet under A4. No scalar A4-triplet is introduced. This
represents one possible realization of general schemes characterized by the
minimal set of either three or five physical parameters. In the three parameter
versions mee vanishes, while in the five parameter schemes the absolute scale
of neutrino mass, although not predicted, is related to the two Majorana
phases. The model realization we discuss is potentially testable at the LHC
through the peculiar leptonic decay patterns of the fermionic and scalar
triplets.
| arxiv topic:hep-ph |
arxiv_dataset-858810.0221 | Time dependent modelisation of TeV blazars by a stratified jet model
astro-ph
We present a new time-dependent inhomogeneous jet model of non-thermal blazar
emission. Ultra-relativistic leptons are injected at the base of a jet and
propagate along it. We assume continuous reacceleration and cooling, producing
a relativistic quasi-maxwellian (or "pile-up") particle energy distribution.
The synchrotron and Synchrotron-Self Compton jet emissivity are computed at
each altitude. Klein-Nishina effects as well as intrinsic gamma-gamma
absorption are included in the computation. Due to the pair production optical
depth, considerable particle density enhancement can occur, particularly during
flaring states.Time-dependent jet emission can be computed by varying the
particle injection, but due to the sensitivity of pair production process, only
small variations of the injected density are required during the flares. The
stratification of the jet emission, together with a pile-up distribution,
allows significantly lower bulk Lorentz factors, compared to one-zone models.
Applying this model to the case of PKS 2155-304 and its big TeV flare observed
in 2006, we can reproduce simultaneously the average broad band spectrum of
this source from radio to TeV, as well as TeV light curve of the flare with
bulk Lorentz factor lower than 15.
| arxiv topic:astro-ph |
arxiv_dataset-859810.0321 | A high resolution view of the jet termination shock in a hot spot of the
nearby radio galaxy Pictor A: implications for X-ray models of radio galaxy
hot spots
astro-ph
Images made with the VLBA have resolved the region in a nearby radio galaxy,
Pictor A, where the relativistic jet that originates at the nucleus terminates
in an interaction with the intergalactic medium, a so-called radio galaxy hot
spot. This image provides the highest spatial resolution view of such an object
to date (16 pc), more than three times better than previous VLBI observations
of similar objects. The north-west Pictor A hot spot is resolved into a complex
set of compact components, seen to coincide with the bright part of the hot
spot imaged at arcsecond-scale resolution with the VLA. In addition to a
comparison with VLA data, we compare our VLBA results with data from the HST
and Chandra telescopes, as well as new Spitzer data. The presence of pc-scale
components in the hot spot, identifying regions containing strong shocks in the
fluid flow, leads us to explore the suggestion that they represent sites of
synchrotron X-ray production, contributing to the integrated X-ray flux of the
hot spot, along with X-rays from synchrotron self-Compton scattering. This
scenario provides a natural explanation for the radio morphology of the hot
spot and its integrated X-ray emission, leading to very different predictions
for the higher energy X-ray spectrum compared to previous studies. From the
sizes of the individual pc-scale components and their angular spread, we
estimate that the jet width at the hot spot is in the range 70 - 700 pc, which
is comparable to similar estimates in PKS 2153-69, 3C 205, and 4C 41.17. The
lower limit in this range arises from the suggestion that the jet may dither in
its direction as it passes through hot spot backflow material close to the jet
termination point, creating a "dentist drill" effect on the inside of a cavity
700 pc in diameter.
| arxiv topic:astro-ph |
arxiv_dataset-860810.0421 | Phase States and Phase Portraits of Tunnel Traffic. Empirical Data
Analysis
physics.soc-ph physics.data-an
The 3D fundamental diagrams and phase portraits for tunnel traffic is
constructed based on the empirical data collected during the last years in the
deep long branch of the Lefortovo tunnel located on the 3rd circular highway in
Moscow. This tunnel of length 3 km is equipped with a dense system of
stationary ra-diodetetors distributed uniformly along it chequerwise at spacing
of 60 m. The data were averaged over 30 s. Each detector measures three
characteristics of the vehicle ensemble; the flow rate, the car velocity, and
the occupancy for three lanes individually. The conducted analysis reveals
complexity of phase states of tunnel traffic. In particular, we show the
presence of cooperative traffic dynamics in this tunnel and the variety of
phase states different in properties. Besides, the regions of regular and
stochastic dynamics are found and the presence of dynamical traps is
demonstrated.
| arxiv topic:physics.soc-ph physics.data-an |
arxiv_dataset-861810.0521 | Characterizing Entanglement Entropy Produced by Non-Linear Scalar
Interactions During Inflation
gr-qc
The density fluctuations that we observe in the universe today are thought to
originate from quantum fluctuations produced during a phase of the early
universe called inflation. By evolving a wavefunction describing two coupled
Fourier modes of a scalar field forward through an inflationary epoch, we
demonstrate that non-linear effects can result in a generation of entanglement
entropy between modes with different momenta in a scalar field during the
inflationary period when just one of the modes is observed. Through this
mechanism, the field would experience decoherence and appear more like a
classical distribution today; however the mechanism is not sufficiently
efficient to explain classicality. We find that the amount of entanglement
entropy generated scales roughly as a power law S \propto \lambda^{1.75}, where
\lambda is the coupling coefficient of the non-linear potential term. We also
investigate how the entanglement entropy scales with the duration of inflation
and compare various entanglement measures from the literature with the von
Neumann entropy. This demonstration explicitly follows particle creation and
interactions between modes; consequently, the mechanism contributing to the
generation of the von Neumann entropy can be easily seen.
| arxiv topic:gr-qc |
arxiv_dataset-862810.0621 | Hadronic observables from Au+Au collisions at s(NN)**(1/2)=200 GeV and
Pb+Pb collisions at s(NN)**(1/2)=5.5 TeV from a simple kinematic model
nucl-th
A simple kinematic model based on superposition of p+p collisions,
relativistic geometry and final-state hadronic rescattering is used to
calculate various hadronic observables in s(NN)**(1/2) = 200 GeV Au+Au
collisions and s(NN)**(1/2) = 5.5 TeV Pb+Pb collisions. The model calculations
are compared with experimental results from several s(NN)**(1/2) = 200 GeV
Au+Au collision studies. If a short hadronization time is assumed in the model,
it is found that this model describes the trends of the observables from these
experiments surprisingly well considering the model's simplicity. This also
gives more credibility to the model predictions presented for s(NN)**(1/2) =
5.5 TeV Pb+Pb collisions.
| arxiv topic:nucl-th |
arxiv_dataset-863810.0721 | Towards Exact Quantum Loop Results in the Theory of General Relativity:
Status and Update
gr-qc
We present the status and update of a new approach to quantum general
relativity as formulated by Feynman from the Einstein-Hilbert action wherein
amplitude-based resummation techniques are applied to the theory's loop
corrections to yield results (superficially) free of ultraviolet(UV)
divergences. Recent applications are summarized.
| arxiv topic:gr-qc |
arxiv_dataset-864810.0821 | The Newton stratification on deformations of local G-shtukas
math.AG math.NT
Bounded local G-shtukas are function field analogs for p-divisible groups
with extra structure. We describe their deformations and moduli spaces. The
latter are analogous to Rapoport-Zink spaces for p-divisible groups. The
underlying schemes of these moduli spaces are affine Deligne-Lusztig varieties.
For basic Newton polygons the closed Newton stratum in the universal
deformation of a local G-shtuka is isomorphic to the completion of a
corresponding affine Deligne-Lusztig variety in that point. This yields bounds
on the dimension and proves equidimensionality of the basic affine
Deligne-Lusztig varieties.
| arxiv topic:math.AG math.NT |
arxiv_dataset-865810.0921 | Rare B decays with moving NRQCD and improved staggered quarks
hep-lat
We calculate form factors relevant for rare B decays using moving-NRQCD for
the b quark and the AsqTad action for the light quarks. Moving NRQCD allows us
to work directly with the physical b quark mass and go to higher recoil
momentum compared to standard NRQCD. Here, we show first results for the matrix
elements and the operator matching coefficients. Some difficulties and possible
ways of improvement are discussed.
| arxiv topic:hep-lat |
arxiv_dataset-866810.1021 | Chiral extrapolation of octet-baryon charge radii
hep-ph
The charge radii of octet-baryons obtained in quenched lattice-QCD
calculations are extrapolated within heavy-baryon chiral perturbation theory.
Finite-range regularization (FRR) is applied to improve the convergence of the
chiral expansion and to provide estimates of quenching artifacts. Lattice
values of quark distribution radii and baryon charge radii for $\mpi^2$ in the
range (0.1, 0.7)$\gev^2$ are described very well with FRR. Upon estimating
corrections for both finite-volume and quenching effects, the obtained charge
radii of the proton, neutron and $\Sigma^-$ are in good agreement with
experimental measurements. The predicted charge radii of the remaining
octet-baryons have not yet been measured and present a challenge to future
experiments.
| arxiv topic:hep-ph |
arxiv_dataset-867810.1121 | The synchronization transition in correlated oscillator populations
cond-mat.stat-mech cond-mat.dis-nn nlin.AO
The synchronization transition of correlated ensembles of coupled Kuramoto
oscillators on sparse random networks is investigated. Extensive numerical
simulations show that correlations between the native frequencies of adjacent
oscillators on the network systematically shift the critical point as well as
the critical exponents characterizing the transition. Negative correlations
imply an onset of synchronization for smaller coupling, whereas positive
correlations shift the critical coupling towards larger interaction strengths.
For negatively correlated oscillators the transition still exhibits critical
behaviour similar to the all-to-all coupled Kuramoto system, while positive
correlations change the universality class of the transition depending on the
correlation strength. Crucially, the paper demonstrates that the
synchronization behaviour is not only determined by the coupling architecture,
but is also strongly influenced by the oscillator placement on the coupling
network.
| arxiv topic:cond-mat.stat-mech cond-mat.dis-nn nlin.AO |
arxiv_dataset-868810.1221 | Complexity of links in 3-manifolds
math.GT
We introduce a natural-valued complexity c(X) for pairs X=(M,L), where M is a
closed orientable 3-manifold and L is a link contained in M. The definition
employs simple spines, but for well-behaved X's we show that c(X) equals the
minimal number of tetrahedra in a triangulation of M containing L in its
1-skeleton. Slightly adapting Matveev's recent theory of roots for graphs, we
carefully analyze the behaviour of c under connected sum away from and along
the link. We show in particular that c is almost always additive, describing in
detail the circumstances under which it is not. To do so we introduce a certain
(0,2)-root for a pair X, we show that it is well-defined, and we prove that X
has the same complexity as its (0,2)-root. We then consider, for links in the
3-sphere, the relations of c with the crossing number and with the hyperbolic
volume of the exterior, establishing various upper and lower bounds. We also
specialize our analysis to certain infinite families of links, providing rather
accurate asymptotic estimates.
| arxiv topic:math.GT |
arxiv_dataset-869810.1321 | Induced p-wave superfluidity in two dimensions: Brane world in cold
atoms and nonrelativistic defect CFTs
cond-mat.other hep-th nucl-th
We propose to use a two-species Fermi gas with the interspecies s-wave
Feshbach resonance to realize p-wave superfluidity in two dimensions. By
confining one species of fermions in a two-dimensional plane immersed in the
background three-dimensional Fermi sea of the other species, an attractive
interaction is induced between two-dimensional fermions. We compute the pairing
gap in the weak-coupling regime and show that it has the symmetry of p_x+ip_y.
Because the magnitude of the pairing gap increases toward the unitarity limit,
it is possible that the critical temperature for the p_x+ip_y-wave
superfluidity becomes within experimental reach. The resulting system has a
potential application to topological quantum computation using vortices with
non-Abelian statistics. We also discuss aspects of our system in the unitarity
limit as a "nonrelativistic defect conformal field theory (CFT)". The reduced
Schr\"odinger algebra, operator-state correspondence, scaling dimensions of
composite operators, and operator product expansions are investigated.
| arxiv topic:cond-mat.other hep-th nucl-th |
arxiv_dataset-870810.1421 | Theoretical Overview of Neutrino Properties
hep-ph astro-ph hep-ex
I give an overview of some basic properties of massive neutrinos. The first
part of this talk is devoted to three fundamental questions about three known
neutrinos and to their flavor issues -- the mass spectrum, mixing pattern and
CP violation. The second part of this talk is to highlight a few hot topics at
the frontiers of neutrino physics and neutrino astrophysics, including the
naturalness and testability of TeV seesaw mechanisms at the LHC, effects of
non-standard interactions on neutrino oscillations, flavor distributions of
ultrahigh-energy cosmic neutrinos at neutrino telescopes, collective flavor
oscillations of supernova neutrinos, flavor effects in thermal leptogenesis,
the GSI anomaly and Moessbauer neutrino oscillations, and so on. I finally make
some concluding remarks for the road ahead.
| arxiv topic:hep-ph astro-ph hep-ex |
arxiv_dataset-871810.1521 | The Mass and Radius of the Neutron Star in EXO 1745-248
astro-ph
Bursting X-ray binaries in globular clusters are ideal sources for measuring
neutron star masses and radii, and hence, for determining the equation of state
of cold, ultradense matter. We use time-resolved spectroscopic data from EXO
1745-248 during thermonuclear bursts that show strong evidence for photospheric
radius expansion to measure the Eddington flux and the apparent surface area of
the neutron star. We combine this with the recent measurement of the distance
to the globular cluster Terzan 5, where this source resides, to measure the
neutron star mass and radius. We find tightly constrained pairs of values for
the mass and radius, which are centered around M=1.4 M_sun and R=11 km or
around M=1.7 M_sun and R=9 km. These values favor nucleonic equations of state
with symmetry energy that is relatively low and has a weak dependence on
density.
| arxiv topic:astro-ph |
arxiv_dataset-872810.1621 | Drinfel'd doubles and Shapovalov determinants
math.QA math.RT
The Shapovalov determinant for a class of pointed Hopf algebras is
calculated, including quantized enveloping algebras, Lusztig's small quantum
groups, and quantized Lie superalgebras. Our main tools are root systems, Weyl
groupoids, and Lusztig type isomorphisms. We elaborate powerful novel
techniques for the algebras at roots of unity, and pass to the general case
using a density argument.
Key words: Hopf algebra, Nichols algebra, quantum group, representation
| arxiv topic:math.QA math.RT |
arxiv_dataset-873810.1721 | Simulation Monte-Carlo du Mod\`ele de Hubbard \`a deux dimensions
cond-mat.str-el
The Quantum Monte-Carlo simulations of the two-dimensional Hubbard model are
presented for the half filling. The method based on the direct-space proposed
by Suzuki and al., and Hirsch and al. was used. The states generated by this
method are basis states in occupation number representation built with Wannier
states localised on each site of the square array. The configurations of
fermions can be observed on the real 2D array. An antiferromagnetic factor is
defined and calculated for each temperature. The curves of energy, specific
heat, conducivity and antiferromagnetic factor are presented for different
values of the repulsive coulombian on site interaction U. There is a
metal-insulator transition at low temperature for small values of U. This
transition corresponds with a paramagnetic-ferromagnetic first order
transition. Indeed, for these interaction values, the energy curves show a gap
which is a characteristic of a first order transition. An hysteresis phenomenon
appears on the conductivity curves. There is a behaviour change for U/t=3.5.
For the values U>3.5 there is ferromagnetic-paramagnetic change without
observable effect on the energy and the specific heat. The metal-insulator
transition does not exist any more, the conductivity stays very small.
Isotherms of the physical quantities versus U/t show a transition which seems
to be the metal-insulator Mott transition. These results allow to draw a phase
diagram with two first order transition lines.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-874810.1821 | Dynamics of a Completely Integrable $N$-Coupled Li\'enard Type Nonlinear
Oscillator
nlin.SI
We present a system of $N$-coupled Li\'enard type nonlinear oscillators which
is completely integrable and possesses explicit $N$ time-independent and $N$
time-dependent integrals. In a special case, it becomes maximally
superintegrable and admits $(2N-1)$ time-independent integrals. The results are
illustrated for the N=2 and arbitrary number cases. General explicit periodic
(with frequency independent of amplitude) and quasiperiodic solutions as well
as decaying type/frontlike solutions are presented, depending on the signs and
magnitudes of the system parameters. Though the system is of a nonlinear damped
type, our investigations show that it possesses a Hamiltonian structure and
that under a contact transformation it is transformable to a system of
uncoupled harmonic oscillators.
| arxiv topic:nlin.SI |
arxiv_dataset-875810.1921 | Operator extensions of Hua's inequality
math.OA math.FA
We give an extension of Hua's inequality in pre-Hilbert $C^*$-modules without
using convexity or the classical Hua's inequality. As a consequence, some known
and new generalizations of this inequality are deduced. Providing a Jensen
inequality in the content of Hilbert $C^*$-modules, another extension of Hua's
inequality is obtained. We also present an operator Hua's inequality, which is
equivalent to operator convexity of given continuous real function.
| arxiv topic:math.OA math.FA |
arxiv_dataset-876810.2021 | Visualization Optimization : Application to the RoboCup Rescue Domain
cs.GR cs.AI
In this paper we demonstrate the use of intelligent optimization
methodologies on the visualization optimization of virtual / simulated
environments. The problem of automatic selection of an optimized set of views,
which better describes an on-going simulation over a virtual environment is
addressed in the context of the RoboCup Rescue Simulation domain. A generic
architecture for optimization is proposed and described. We outline the
possible extensions of this architecture and argue on how several problems
within the fields of Interactive Rendering and Visualization can benefit from
it.
| arxiv topic:cs.GR cs.AI |
arxiv_dataset-877810.2121 | Symmetries of the relativistic two-boson system in external field
hep-th
We investigate the survival of symmetries in a relativistic system of two
mutually interacting bosons coupled with an external field, when this field is
"strongly" translation invariant in some directions and additionally remains
unchanged by other isometries of spacetime. Since the relativistic interactions
cannot be composed additively, it is not a priori garanteed that the two-body
system inherits all the symmetries of the external potential. However, using an
ansatz which permits to preserve the compatibility of the mass-shell
constraints in the presence of the field, we show how "surviving isometries"
can actually be implemented in the two-body wave equations.
| arxiv topic:hep-th |
arxiv_dataset-878810.2221 | Cancellation of nonlinear Zeeman shifts with light shifts
physics.atom-ph
Nonlinear Zeeman (NLZ) shifts arising from magnetic-field mixing of the two
hyperfine ground-states in alkali atoms lead to splitting of magnetic-resonance
lines. This is a major source of sensitivity degradation and the so-called
"heading errors" of alkali-vapor atomic magnetometers operating in the
geophysical field range (B approx. 0.2-0.7 G). Here, it is shown theoretically
and experimentally that NLZ shifts can be effectively canceled by light shifts
caused by a laser field of appropriate intensity, polarization and frequency, a
technique that can be readily applied in practical situations.
| arxiv topic:physics.atom-ph |
arxiv_dataset-879810.2321 | Thickness-tuned Superconductor-to-Insulator Transitions under magnetic
field in a-NbSi
cond-mat.supr-con cond-mat.dis-nn
We have studied the thickness-induced superconductor-to-insulator transition
in the presence of a magnetic field for a-NbSi thin films. Analyzing the
critical behavior of this system within the "dirty boson model", we have found
a critical exponents product of $\nu_d z$ > 0.4. The corresponding phase
diagram in the (H,d) plane is inferred. This small exponent product as well as
the non-universal value of the critical resistance found at the transition call
for further investigations in order to thoroughly understand these transitions.
| arxiv topic:cond-mat.supr-con cond-mat.dis-nn |
arxiv_dataset-880810.2421 | Theoretical study of the magnetization dynamics of non-dilute
ferrofluids
cond-mat.soft cond-mat.mes-hall
The paper is devoted to the theoretical investigation of the magnetodipolar
interparticle interaction effect on remagnetization dynamics in moderately
concentrated ferrofluids. We consider a homogeneous (without particle
aggregates) ferrofluid consisting of identical spherical particles and employ a
rigid dipole model, where magnetic moment of a particle is fixed with respect
to the particle itself. In particular, for the magnetization relaxation after
the external field is instantly switched off, we show that the magnetodipolar
interaction leads to the increase of the initial magnetization relaxation time.
For the complex ac-susceptibility we find that the this interaction leads to an
overall increase of the imaginary susceptibility part and shifts the peak on
its frequency dependence towards lower frequencies. Comparing results obtained
with our analytical approach (second order virial expansion) to numerical
simulation data (Langevin dynamics method), we demonstrate that the employed
virial expansion approximation gives a good qualitative description of the
ferrofluid magnetization dynamics and provides a satisfactory quantitative
agreement with numerical simulations for the dc magnetization relaxation - up
to the particle volume fraction c ~ 10% and for the ac-susceptibility - up to c
~ 5 %.
| arxiv topic:cond-mat.soft cond-mat.mes-hall |
arxiv_dataset-881810.2521 | Asymptotic behavior of a nonlocal parabolic problem in Ohmic heating
process
math.AP
In this paper, we consider the asymptotic behavior of the nonlocal parabolic
problem \[ u_{t}=\Delta u+\displaystyle\frac{\lambda
f(u)}{\big(\int_{\Omega}f(u)dx\big)^{p}}, x\in \Omega, t>0, \] with homogeneous
Dirichlet boundary condition, where $\lambda>0, p>0$, $f$ is nonincreasing. It
is found that: (a) For $0<p\leq1$, $u(x,t)$ is globally bounded and the unique
stationary solution is globally asymptotically stable for any $\lambda>0$; (b)
For $1<p<2$, $u(x,t)$ is globally bounded for any $\lambda>0$; (c) For $p=2$,
if $0<\lambda<2|\partial\Omega|^2$, then $u(x,t)$ is globally bounded, if
$\lambda=2|\partial\Omega|^2$, there is no stationary solution and $u(x,t)$ is
a global solution and $u(x,t)\to\infty$ as $t\to\infty$ for all $x\in\Omega$,
if $\lambda>2|\partial\Omega|^2$, there is no stationary solution and $u(x,t)$
blows up in finite time for all $x\in\Omega$; (d) For $p>2$, there exists a
$\lambda^*>0$ such that for $\lambda>\lambda^*$, or for
$0<\lambda\leq\lambda^*$ and $u_0(x)$ sufficiently large, $u(x,t)$ blows up in
finite time. Moreover, some formal asymptotic estimates for the behavior of
$u(x,t)$ as it blows up are obtained for $p\geq2$.
| arxiv topic:math.AP |
arxiv_dataset-882810.2621 | Odd- and even-order dispersion cancellation in quantum interferometry
quant-ph physics.optics
We describe a novel effect involving odd-order dispersion cancellation. We
demonstrate that odd- and even-order dispersion cancellation may be obtained in
different regions of a single quantum interferogram using
frequency-anticorrelated entangled photons and a new type of quantum
interferometer. This offers new opportunities for quantum communication and
metrology in dispersive media.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-883810.2721 | Contact projective structures and chains
math.DG
Contact projective structures have been profoundly studied by D.J.F. Fox. He
associated to a contact projective structure a canonical projective structure
on the same manifold. We interpret Fox' construction in terms of the equivalent
parabolic (Cartan) geometries, showing that it is an analog of Fefferman's
construction of a conformal structure associated to a CR structure. We show
that, on the level of Cartan connections, this Fefferman--type construction is
compatible with normality if and only if the initial structure has vanishing
contact torsion. This leads to a geometric description of the paths that have
to be added to the contact geodesics of a contact projective structure in order
to obtain the subordinate projective structure. They are exactly the chains
associated to the contact projective structure, which are analogs of the
Chern-Moser chains in CR geometry. Finally, we analyze the consequences for the
geometry of chains and prove that a chain-preserving contactomorphism must be a
morphism of contact projective structures.
| arxiv topic:math.DG |
arxiv_dataset-884810.2821 | Concentration Inequalities and Laws of Large Numbers under Epistemic
Irrelevance
math.PR math.ST stat.TH
This paper presents concentration inequalities and laws of large numbers
under weak assumptions of irrelevance, expressed through lower and upper
expectations. The results are variants and extensions of De Cooman and
Miranda's recent inequalities and laws of large numbers. The proofs indicate
connections between concepts of irrelevance for lower/upper expectations and
the standard theory of martingales.
| arxiv topic:math.PR math.ST stat.TH |
arxiv_dataset-885810.2921 | NNLO corrections to B --> X_u l nu and the determination of |V_ub|
hep-ph
The calculation of partial decay rates in B --> X_u l nu decays at
next-to-next-to-leading order (NNLO) in alpha_s and to leading order in 1/m_b
is described. New results for the hard function are combined with known results
for the jet function and shape-function moments in a numerical analysis which
explores the impact of the NNLO corrections on partial decay rates and the
determination of |V_{ub}|.
| arxiv topic:hep-ph |
arxiv_dataset-886810.3021 | $k^*$-Metrizable Spaces and their Applications
math.GN
In this paper we introduce and study so-called $k^*$-metrizable spaces
forming a new class of generalized metric spaces, and display various
applications of such spaces in topological algebra, functional analysis, and
measure theory.
By definition, a Hausdorff topological space $X$ is $k^*$-metrizable if $X$
is the image of a metrizable space $M$ under a continuous map $f:M\to X$ having
a section $s:X\to M$ that preserves precompact sets in the sense that the image
$s(K)$ of any compact set $K\subset X$ has compact closure in $X$.
| arxiv topic:math.GN |
arxiv_dataset-887810.3121 | Asymptotic normality for deconvolution kernel density estimators from
random fields
math.ST stat.TH
The paper discusses the estimation of a continuous density function of the
target random field $X_{\bf{i}}$, $\bf{i}\in \mathbb {Z}^N$ which is
contaminated by measurement errors. In particular, the observed random field
$Y_{\bf{i}}$, $\bf{i}\in \mathbb {Z}^N$ is such that
$Y_{\bf{i}}=X_{\bf{i}}+\epsilon_{\bf{i}}$, where the random error
$\epsilon_{\bf{i}}$ is from a known distribution and independent of the target
random field. Compared to the existing results, the paper is improved in two
directions. First, the random vectors in contrast to univariate random
variables are investigated. Second, a random field with a certain spatial
interactions instead of i. i. d. random variables is studied. Asymptotic
normality of the proposed estimator is established under appropriate
conditions.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-888810.3221 | Recent developments in the techniques of controlling and measuring
suction in unsaturated soils
physics.class-ph
The difficulty of measuring and controlling suction in unsaturated soils is
one of the reasons why the development of the mechanics of unsaturated soils
has not been as advanced as that of saturated soils. However, significant
developments have been carried out in the last decade in this regard. In this
paper, a re-view of some developments carried out in the techniques of
controlling suction by using the axis translation, the osmotic method and the
vapour control technique is presented. The paper also deals with some recent
de-velopments in the direct measurement of suction by using high capacity
tensiometers and in the measurement of high suction by using high range
psychrometers. The recent progresses made in these techniques have been
significant and will certainly help further experimental investigation of the
hydromechanical behaviour of un-saturated soils.
| arxiv topic:physics.class-ph |
arxiv_dataset-889810.3321 | The evolution of a pre-heated Intergalactic Medium
astro-ph
We analyse the evolution of the Intergalactic Medium (IGM) by means of an
extended set of large box size hydrodynamical simulations which include
pre-heating. We focus on the properties of the z~2 Lyman-alpha forest and on
the population of clusters and groups of galaxies at z=0. We investigate the
distribution of voids in the Lyman-alpha flux and the entropy-temperature
relation of galaxy groups, comparing the simulation results to recent data from
high-resolution quasar spectra and from X-ray observations. Pre-heating is
included through a simple phenomenological prescription, in which at z=4 the
entropy of all gas particles, whose overdensity exceeds a threshold value
delta_h is increased to a minimum value K_fl. While the entropy level observed
in the central regions of galaxy groups requires a fairly strong pre-heating,
with K_fl>100 keV cm^2, the void statistics of the Lyman-alpha forest impose
that this pre-heating should take place only in relatively high-density
regions, in order not to destroy the cold filaments that give rise to the
forest. We conclude that any injection of non-gravitational energy in the
diffuse baryons should avoid low-density regions at high redshift and/or take
place at relatively low redshift.
| arxiv topic:astro-ph |
arxiv_dataset-890810.3421 | Macrospin model of incubation delay due to the field-like spin transfer
torque
cond-mat.mes-hall
We show that the absence of pre-switching oscillations ("incubation delay")
in magnetic tunnel junctions can be explained within the macrospin model by a
sizable field-like component of the spin-transfer torque. It is further
suggested that measurements of the voltage dependence of tunnel junction
switching time in the presence of external easy axis magnetic fields can be
used to determine the magnitude and voltage dependence of the field-like
torque.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-891810.3521 | Avoided crossing resonances: structural and dynamical aspects
quant-ph
We examine structural and dynamical properties of quantum resonances
associated with an avoided crossing and identify the parameter shifts where
these properties attain maximal or extreme values, first at a general level,
and then for a two-level system coupled to a harmonic oscillator, of the type
commonly found in quantum optics. Finally the results obtained are exemplified
and applied to optimize the fidelity and speed of quantum gates in trapped
ions.
| arxiv topic:quant-ph |
arxiv_dataset-892810.3621 | Tristability in the pendula chain
nlin.PS cond-mat.stat-mech nlin.SI physics.class-ph
Experiments on a chain of coupled pendula driven periodically at one end
demonstrate the existence of a novel regime which produces an output frequency
at an odd fraction of the driving frequency. The new stationary state is then
obtained on numerical simulations and modeled with an analytical solution of
the continuous sine-Gordon equation that resembles a kink-like motion back and
forth in the restricted geometry of the chain. This solution differs from the
expressions used to understand nonlinear bistability where the synchronization
constraint was the basic assumption. As a result the short pendula chain is
shown to possess tristable stationary states and to act as a frequency divider.
| arxiv topic:nlin.PS cond-mat.stat-mech nlin.SI physics.class-ph |
arxiv_dataset-893810.3721 | Second maximal subgroups of the finite alternating and symmetric groups
math.GR
A subgroup of a finite group G is said to be second maximal if it is maximal
in every maximal subgroup of G that contains it. A question which has received
considerable attention asks: can every positive integer occur as the number of
the maximal subgroups that contain a given second maximal subgroup in some
finite group G? Various reduction arguments are available except when G is
almost simple. Following the classification of the finite simple groups, finite
almost simple groups fall into three categories: alternating and symmetric
groups, almost simple groups of Lie type, sporadic groups and automorphism
groups of sporadic groups. This thesis investigates the finite alternating and
symmetric groups, and finds that in such groups, except three well known
examples, no second maximal subgroup can be contained in more than 3 maximal
subgroups.
| arxiv topic:math.GR |
arxiv_dataset-894810.3821 | Probing Non Standard Neutrino Physics at T2KK and Neutrino Factory
hep-ph
We discuss the possibility of constraining or discovering the non-standard
neutrino physics beyond the standard model with future long baseline neutrino
oscillation experiments. Among very many possible experimental set up we
discuss neutrino factory and T2KK, in which two detector setting may be useful
to achieve the goal. In particular, neutrino factory with two detectors at
baselines of 3000 km and 7000 km have a great sensitivity to non-standard
interaction (NSI) and solve the $\theta_{13}$-NSI confusion problem.
| arxiv topic:hep-ph |
arxiv_dataset-895810.3921 | Simplified Models for a First Characterization of New Physics at the LHC
hep-ph
Low-energy SUSY and several other theories that address the hierarchy problem
predict pair-production at the LHC of particles with Standard Model quantum
numbers that decay to jets, missing energy, and possibly leptons. If an excess
of such events is seen in LHC data, a theoretical framework in which to
describe it will be essential to constraining the structure of the new physics.
We propose a basis of four deliberately simplified models, each specified by
only 2-3 masses and 4-5 branching ratios, for use in a first characterization
of data. Fits of these simplified models to the data furnish a quantitative
presentation of the jet structure, electroweak decays, and heavy-flavor content
of the data, independent of detector effects. These fits, together with plots
comparing their predictions to distributions in data, can be used as targets
for describing the data within any full theoretical model.
| arxiv topic:hep-ph |
arxiv_dataset-896810.4021 | Osmotically driven pipe flows and their relation to sugar transport in
plants
physics.flu-dyn
In plants, osmotically driven flows are believed to be responsible for
translocation of sugar in the pipe-like phloem cell network, spanning the
entire length of the plant. In this paper, we present an experimental and
theoretical study of transient osmotically driven flows through pipes with
semipermeable walls. We extend the experimental work of Eschrich, Evert and
Young \cite[]{Eschrich:1972} by providing a more accurate version of their
experiment allowing for better comparison with theory. In the experiments we
measure the dynamics and structure of a "sugar front", i.e. the transport and
decay of a sudden loading of sugar in a pipe which is closed in both ends. We
include measurements of pressure inside the membrane tube allowing us to
compare the experiments directly with theory and, in particular, to confirm
quantitatively the exponential decay of the front in a closed tube.In a novel
setup we are able to measure the entire concentration profile as the sugar
front moves. In contrast to previous studies we find very good agreement
between experiment and theory.
In the limit of low axial resistance (valid in our experiments as well as in
many cases in plants) we show that the equations can be solved exactly by the
method of characteristics yielding, in general, an implicit solution. Further
we show that under more general conditions the equations of motion can be
rewritten as a single integro-differential equation, which can be readily
solved numerically. The applicability of our results to plants is discussed and
it is shown that it is probable that the pressure-flow hypothesis can account
for short distance transport of sugar in plants.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-897810.4121 | Checking formalism for central exclusive production in the first LHC
runs
hep-ph
We discuss how the early LHC data runs can provide crucial tests of the
formalism used to predict the cross sections of central exclusive production.
| arxiv topic:hep-ph |
arxiv_dataset-898810.4221 | Chaos, concentration, and multiple valleys
math.PR math-ph math.MP
Disordered systems are an important class of models in statistical mechanics,
having the defining characteristic that the energy landscape is a fixed
realization of a random field. Examples include various models of glasses and
polymers. They also arise in other areas, like fitness models in evolutionary
biology. The ground state of a disordered system is the state with minimum
energy. The system is said to be chaotic if a small perturbation of the energy
landscape causes a drastic shift of the ground state. We present a rigorous
theory of chaos in disordered systems that confirms long-standing physics
intuition about connections between chaos, anomalous fluctuations of the ground
state energy, and the existence of multiple valleys in the energy landscape.
Combining these results with mathematical tools like hypercontractivity, we
establish the existence of the above phenomena in eigenvectors of GUE matrices,
the Kauffman-Levin model of evolutionary biology, directed polymers in random
environment, a subclass of the generalized Sherrington-Kirkpatrick model of
spin glasses, the discrete Gaussian free field, and continuous Gaussian fields
on Euclidean spaces. We also list several open questions.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-899810.4321 | Z (+jets) At The Tevatron
hep-ex
We report on recent Z (+jets) measurements from the Fermilab Tevatron proton
anti-proton collider. A new D0 measurement of the transverse momentum of Z
bosons yields the best measurement to date of the non-perturbative form factor,
g2. The production of Z+jets is an major background to many rare signals, and
is a vital testing ground for theoretical predictions. Measurements from CDF
and D0 of differential cross sections in Z+jet production test NLO pQCD, and in
the case of D0, the latest tree-level matrix element with matched parton shower
calculations. Improving modelling of this signal will impact results from the
Fermilab Tevatron and CERN LHC.
| arxiv topic:hep-ex |
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