49,973 research outputs found
Finite-size scaling of out-of-time-ordered correlators at late times
Chaotic dynamics in quantum many-body systems scrambles local information so
that at late times it can no longer be accessed locally. This is reflected
quantitatively in the out-of-time-ordered correlator of local operators, which
is expected to decay to zero with time. However, for systems of finite size,
out-of-time-ordered correlators do not decay exactly to zero and in this paper
we show that the residual value can provide useful insights into the chaotic
dynamics. When energy is conserved, the late-time saturation value of the
out-of-time-ordered correlator of generic traceless local operators scales as
an inverse polynomial in the system size. This is in contrast to the inverse
exponential scaling expected for chaotic dynamics without energy conservation.
We provide both analytical arguments and numerical simulations to support this
conclusion.Comment: improved presentatio
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An agent-based DDM for high level architecture
The Data Distribution Management (DDM) service is one of the six services provided in the Runtime Infrastructure (RTI) of High Level Architecture (HLA). Its purpose is to perform data filtering and reduce irrelevant data communicated between federates. The two DDM schemes proposed for RTI, region based and grid based DDM, are oriented to send as little irrelevant data to subscribers as possible, but only manage to filter part of this information and some irrelevant data is still being communicated. Previously (G. Tan et al., 2000), we employed intelligent agents to perform data filtering in HLA, implemented an agent based DDM in RTI (ARTI) and compared it with the other two filtering mechanisms. The paper reports on additional experiments, results and analysis using two scenarios: the AWACS sensing aircraft simulation and the air traffic control simulation scenario. Experimental results show that compared with other mechanisms, the agent based approach communicates only relevant data and minimizes network communication, and is also comparable in terms of time efficiency. Some guidelines on when the agent based scheme can be used are also give
Density-dependent deformed relativistic Hartree-Bogoliubov theory in continuum
The deformed relativistic Hartree-Bogoliubov theory in continuum with the
density-dependent meson-nucleon couplings is developed. The formulism is
briefly presented with the emphasis on handling the density-dependent
couplings, meson fields, and potentials in axially deformed system with partial
wave method. Taking the neutron-rich nucleus Mg as an example, the newly
developed code is verified by the spherical relativistic continuum
Hartree-Bogoliubov calculations, where only the spherical components of the
densities are considered. When the deformation is included self-consistently,
it is shown that the spherical components of density-dependent coupling
strengths are dominant, while the contributions from low-order deformed
components are not negligible.Comment: 5 pages, 3 figures, and 1 tabl
The Luminosity - E_p Relation within Gamma--Ray Bursts and Implications for Fireball Models
Using a sample of 2408 time-resolved spectra for 91 BATSE gamma-ray bursts
(GRBs) presented by Preece et al., we show that the relation between the
isotropic-equivalent luminosity (L_iso) and the spectral peak energy (E_p) in
the cosmological rest frame, L_iso \propto E_p^2, not only holds within these
bursts, but also holds among these GRBs, assuming that the burst rate as a
function of redshift is proportional to the star formation rate. The possible
implications of this relation for the emission models of GRBs are discussed. We
suggest that both the kinetic-energy-dominated internal shock model and the
magnetic-dissipation-dominated external shock model can well interpret this
relation. We constrain the parameters for these two models, and find that they
are in a good agreement with the parameters from the fittings to the afterglow
data (abridged).Comment: 3 pages plus 5 figures, emulateapj style, accepted for publication in
ApJ Letter
High magnetoresistance at room temperature in p-i-n graphene nanoribbons due to band-to-band tunneling effects
A large magnetoresistance effect is obtained at room-temperature by using
p-i-n armchair-graphene-nanoribbon (GNR) heterostructures. The key advantage is
the virtual elimination of thermal currents due to the presence of band gaps in
the contacts. The current at B=0T is greatly decreased while the current at
B>0T is relatively large due to the band-to-band tunneling effects, resulting
in a high magnetoresistance ratio, even at room-temperature. Moreover, we
explore the effects of edge-roughness, length, and width of GNR channels on
device performance. An increase in edge-roughness and channel length enhances
the magnetoresistance ratio while increased channel width can reduce the
operating bias.Comment: http://dx.doi.org/10.1063/1.362445
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Experimental and Numerical Investigation on Progressive Collapse Resistance of Post-tensioned Precast Concrete Beam-Column Sub-assemblages
In this paper, four 1/2 scaled precast concrete (PC) beam-column sub-assemblages with high performance connection were tested under push-down loading procedure to study the load resisting mechanism of PC frames subjected to different column removal scenarios. The parameters investigated include the location of column removal and effective prestress in tendons. The test results indicated that the failure modes of unbonded post-tensioned precast concrete (PTPC) frames were different from that of reinforced concrete (RC) frames: no cracks formed in the beams and wide opening formed near the beam to column interfaces. For specimens without overhanging beams, the failure of side column was eccentric compression failure. Moreover, the load resisting mechanisms in PC frames were significantly different from that of RC frames: the compressive arch action (CAA) developed in concrete during column removal was mainly due to actively applied pre-compressive stress in the concrete; CAA will not vanish when severe crush in concrete occurred. Thus, it may provide negative contribution for load resistance when the displacement exceeds one-beam depth; the tensile force developed in the tendons could provide catenary action from the beginning of the test. Moreover, to deeper understand the behavior of tested specimens, numerical analyses were carried out. The effects of concrete strength, axial compression ratio at side columns, and loading approaches on the behavior of the sub-assemblages were also investigated based on validated numerical analysis
De Novo Genome Sequence of "Candidatus Liberibacter solanacearum" from a Single Potato Psyllid in California.
The draft genome sequence of "Candidatus Liberibacter solanacearum" strain RSTM from a potato psyllid (Bactericera cockerelli) in California is reported here. The RSTM strain has a genome size of 1,286,787 bp, a G+C content of 35.1%, 1,211 predicted open reading frames (ORFs), and 43 RNA genes
Comptonization signatures in the rapid aperiodic variability of Galactic black-hole candidates
We investigate the effect of inverse-Compton scattering of flares of soft
radiation in different geometries of a hot, Comptonizing region and a colder
accretion disk around a solar-mass black hole. The photon-energy dependent
light curves, their Fourier transforms, power spectra and Fourier-period
dependent time lags of hard photons with respect to softer photons are
discussed. On the basis of a comparison with existing data we find arguments
against Comptonization of external soft radiation as well as Comptonization in
a homogeneous medium as dominant mechanisms for the rapid aperiodic variability
in Galactic black-hole candidates. Possible further observational tests for the
influence of Comptonization on the rapid aperiodic variability of Galactic
black-hole candidates are suggested.Comment: 32 pages, including 10 figures and 2 tables; uses epsf.sty,
rotate.sty; submitted to Ap
On particle acceleration and trapping by Poynting flux dominated flows
Using particle-in-cell (PIC) simulations, we study the evolution of a
strongly magnetized plasma slab propagating into a finite density ambient
medium. Like previous work, we find that the slab breaks into discrete magnetic
pulses. The subsequent evolution is consistent with diamagnetic relativistic
pulse acceleration of \cite{liangetal2003}. Unlike previous work, we use the
actual electron to proton mass ratio and focus on understanding trapping vs.
transmission of the ambient plasma by the pulses and on the particle
acceleration spectra. We find that the accelerated electron distribution
internal to the slab develops a double-power law. We predict that emission from
reflected/trapped external electrons will peak after that of the internal
electrons. We also find that the thin discrete pulses trap ambient electrons
but allow protons to pass through, resulting in less drag on the pulse than in
the case of trapping of both species. Poynting flux dominated scenarios have
been proposed as the driver of relativistic outflows and particle acceleration
in the most powerful astrophysical jets.Comment: 25 pages, Accepted by Plasma Physics and Controlled Fusio
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