2,622 research outputs found
Proof of the generalized Lieb-Wehrl conjecture for integer indices larger than one
Gnutzmann and Zyczkowski have proposed the Renyi-Wehrl entropy as a
generalization of the Wehrl entropy, and conjectured that its minimum is
obtained for coherent states. We prove this conjecture for the Renyi index
q=2,3,... in the cases of compact semisimple Lie groups. A general formula for
the minimum value is given.Comment: 8 pages, typos fixed, published versio
Finite-Size Scaling Analysis of the Eigenstate Thermalization Hypothesis in a One-Dimensional Interacting Bose gas
By calculating correlation functions for the Lieb-Liniger model based on the
algebraic Bethe ansatz method, we conduct a finite-size scaling analysis of the
eigenstate thermalization hypothesis (ETH) which is considered to be a possible
mechanism of thermalization in isolated quantum systems. We find that the ETH
in the weak sense holds in the thermodynamic limit even for an integrable
system although it does not hold in the strong sense. Based on the result of
the finite-size scaling analysis, we compare the contribution of the weak ETH
to thermalization with that of yet another thermalization mechanism, the
typicality, and show that the former gives only a logarithmic correction to the
latter.Comment: 5 pages, 3 figure
Using Pilot Systems to Execute Many Task Workloads on Supercomputers
High performance computing systems have historically been designed to support
applications comprised of mostly monolithic, single-job workloads. Pilot
systems decouple workload specification, resource selection, and task execution
via job placeholders and late-binding. Pilot systems help to satisfy the
resource requirements of workloads comprised of multiple tasks. RADICAL-Pilot
(RP) is a modular and extensible Python-based pilot system. In this paper we
describe RP's design, architecture and implementation, and characterize its
performance. RP is capable of spawning more than 100 tasks/second and supports
the steady-state execution of up to 16K concurrent tasks. RP can be used
stand-alone, as well as integrated with other application-level tools as a
runtime system
Moments of generalized Husimi distributions and complexity of many-body quantum states
We consider generalized Husimi distributions for many-body systems, and show
that their moments are good measures of complexity of many-body quantum states.
Our construction of the Husimi distribution is based on the coherent state of
the single-particle transformation group. Then the coherent states are
independent-particle states, and, at the same time, the most localized states
in the Husimi representation. Therefore delocalization of the Husimi
distribution, which can be measured by the moments, is a sign of many-body
correlation (entanglement). Since the delocalization of the Husimi distribution
is also related to chaoticity of the dynamics, it suggests a relation between
entanglement and chaos. Our definition of the Husimi distribution can be
applied not only to the systems of distinguishable particles, but also to those
of identical particles, i.e., fermions and bosons. We derive an algebraic
formula to evaluate the moments of the Husimi distribution.Comment: published version, 33 pages, 7 figre
Second moment of the Husimi distribution as a measure of complexity of quantum states
We propose the second moment of the Husimi distribution as a measure of
complexity of quantum states. The inverse of this quantity represents the
effective volume in phase space occupied by the Husimi distribution, and has a
good correspondence with chaoticity of classical system. Its properties are
similar to the classical entropy proposed by Wehrl, but it is much easier to
calculate numerically. We calculate this quantity in the quartic oscillator
model, and show that it works well as a measure of chaoticity of quantum
states.Comment: 25 pages, 10 figures. to appear in PR
Foundation of Statistical Mechanics under experimentally realistic conditions
We demonstrate the equilibration of isolated macroscopic quantum systems,
prepared in non-equilibrium mixed states with significant population of many
energy levels, and observed by instruments with a reasonably bound working
range compared to the resolution limit. Both properties are fulfilled under
many, if not all, experimentally realistic conditions. At equilibrium, the
predictions and limitations of Statistical Mechanics are recovered.Comment: Accepted in Phys. Rev. Let
Prediction of melt depth in selected architectural materials during high power diode laser treatment
The development of an accurate analysis procedure for many laser applications, including the surface treatment of architectural materials, is extremely complicated due to the multitude of process parameters and materials characteristics involved. A one-dimensional analytical model based on Fourier’s law, with quasi-stationary situations in an isotropic and inhomogeneous workpiece with a parabolic meltpool geometry being assumed, was successfully developed. This model, with the inclusion of an empirically determined correction factor, predicted high power diode laser (HPDL) induced melt depths in clay quarry tiles, ceramic tiles and ordinary Portland cement (OPC) that were in close agreement with those obtained experimentally. It was observed, however, that as the incident laser line energy increased (>15 W mm-1 s-1/2), the calculated and the experimental melt depths began to diverge at an increasing rate. It is believed that this observed increasing discrepancy can be attributed to the fact the model developed neglects sideways conduction which, although it can be reasonably neglected at low energy densities, becomes significant at higher energy densities since one-dimensional heat transfer no longer holds true
Simulated Tempering and Magnetizing: An Application of Two-Dimensional Simulated Tempering to Two-Dimensional Ising Model and Its Crossover
We performed two-dimensional simulated tempering (ST) simulations of the
two-dimensional Ising model with different lattice sizes in order to
investigate the two-dimensional ST's applicability to dealing with phase
transitions and to study the crossover of critical scaling behavior. The
external field, as well as the temperature, was treated as a dynamical variable
updated during the simulations. Thus, this simulation can be referred to as
"Simulated Tempering and Magnetizing (STM)." We also performed the "Simulated
Magnetizing" (SM) simulations, in which the external field was considered as a
dynamical variable and temperature was not. As has been discussed by previous
studies, the ST method is not always compatible with first-order phase
transitions. This is also true in the magnetizing process. Flipping of the
entire magnetization did not occur in the SM simulations under
in large lattice-size simulations. However, the phase changed through the high
temperature region in the STM simulations. Thus, the dimensional extension let
us eliminate the difficulty of the first-order phase transitions and study wide
area of the phase space. We then discuss how frequently parameter-updating
attempts should be made for optimal convergence. The results favor frequent
attempts. We finally study the crossover behavior of the phase transitions with
respect to the temperature and external field. The crossover behavior was
clearly observed in the simulations in agreement with the theoretical
implications.Comment: 15 pages, (Revtex4-1), 23 figures, 1 video (link
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