Search results for " Statistical"
showing 10 items of 1649 documents
Application of thermodynamics to driven systems
2007
Application of thermodynamics to driven systems is discussed. As particular examples, simple traffic flow models are considered. On a microscopic level, traffic flow is described by Bando's optimal velocity model in terms of accelerating and decelerating forces. It allows to introduce kinetic, potential, as well as total energy, which is the internal energy of the car system in view of thermodynamics. The latter is not conserved, although it has certain value in any of two possible stationary states corresponding either to fixed point or to limit cycle in the space of headways and velocities. On a mesoscopic level of description, the size n of car cluster is considered as a stochastic varia…
Controlling stability and transport of magnetic microswimmers by an external field
2019
We investigate the hydrodynamic stability and transport of magnetic microswimmers in an external field using a kinetic theory framework. Combining linear stability analysis and nonlinear 3D continuum simulations, we show that for sufficiently large activity and magnetic field strengths, a homogeneous polar steady state is unstable for both puller and pusher swimmers. This instability is caused by the amplification of anisotropic hydrodynamic interactions due to the external alignment and leads to a partial depolarization and a reduction of the average transport speed of the swimmers in the field direction. Notably, at higher field strengths a reentrant hydrodynamic stability emerges where t…
Phase Equilibria of Lattice Polymers from Histogram Reweighting Monte Carlo Simulations
1998
Histogram-reweighting Monte Carlo simulations were used to obtain polymer / solvent phase diagrams for lattice homopolymers of chain lengths up to r=1000 monomers. The simulation technique was based on performing a series of grand canonical Monte Carlo calculations for a small number of state points and combining the results to obtain the phase behavior of a system over a range of temperatures and densities. Critical parameters were determined from mixed-field finite-size scaling concepts by matching the order parameter distribution near the critical point to the distribution for the three-dimensional Ising universality class. Calculations for the simple cubic lattice (coordination number z…
Monte Carlo calculation of dose rate distributions around the Walstam CDC.K-type137Cs sources
2001
Basic dosimetric data for the Walstam CDC.K-type low dose rate 137Cs sources in water have been calculated using Monte Carlo techniques. These sources, CDC.K1 -K3 and CDC.K4, are widely used in a range of applicators and moulds for the treatment of intracavitary and superficial cancers. Our purpose is to improve existing data about these sources using the Monte Carlo simulation code GEANT3. Absolute dose rate distributions in water have been calculated around these sources and are presented as conventional 2D Cartesian look-up tables. Also the AAPM Task Group 43 formalism for dose calculation has been applied. The calculated dose rate constant for the CDC.K1-K3 source is A = 1.106 +/- 0.001…
Noise delayed decay of unstable states: theory versus numerical simulations
2004
We study the noise delayed decay of unstable nonequilibrium states in nonlinear dynamical systems within the framework of the overdamped Brownian motion model. We give the exact expressions for the decay times of unstable states for polynomial potential profiles and obtain nonmonotonic behavior of the decay times as a function of the noise intensity for the unstable nonequilibrium states. The analytical results are compared with numerical simulations.
Quantum Zeno subspaces induced by temperature
2011
We discuss the partitioning of the Hilbert space of a quantum system induced by the interaction with another system at thermal equilibrium, showing that the higher the temperature the more effective is the formation of Zeno subspaces. We show that our analysis keeps its validity even in the case of interaction with a bosonic reservoir, provided appropriate limitations of the relevant bandwidth.
Role of temperature in the occurrence of some Zeno phenomena
2012
Temperature can be responsible for strengthening effective couplings between quantum states, determining a hierarchy of interactions, and making it possible to establish such dynamical regimes known as Zeno dynamics, wherein a strong coupling can hinder the effects of a weak one. The relevant physical mechanisms which connect the structure of a thermal state with the appearance of special dynamical regimes are analyzed in depth.
Genuine multipartite entanglement of symmmetric Gaussian states: Strong monogamy, unitary localization, scaling behavior, and molecular sharing struc…
2008
We investigate the structural aspects of genuine multipartite entanglement in Gaussian states of continuous variable systems. Generalizing the results of [Adesso & Illuminati, Phys. Rev. Lett. 99, 150501 (2007)], we analyze whether the entanglement shared by blocks of modes distributes according to a strong monogamy law. This property, once established, allows to quantify genuine N-partite entanglement in terms of the "residual contangle" not encoded into 2,...,K,...,(N-1)-partite quantum correlations. The explicit expression of this entanglement measure is derived, by a recursive formula, for a subclass of Gaussian states. These are fully symmetric (permutation-invariant) states multi-…
Landauer’s Principle in Multipartite Open Quantum System Dynamics
2015
We investigate the link between information and thermodynamics embodied by Landauer's principle in the open dynamics of a multipartite quantum system. Such irreversible dynamics is described in terms of a collisional model with a finite temperature reservoir. We demonstrate that Landauer's principle holds, for such a configuration, in a form that involves the flow of heat dissipated into the environment and the rate of change of the entropy of the system. Quite remarkably, such a principle for {\it heat and entropy power} can be explicitly linked to the rate of creation of correlations among the elements of the multipartite system and, in turn, the non-Markovian nature of their reduced evol…
Stabilization of quantum metastable states by dissipation
2015
Normally, quantum fluctuations enhance the escape from metastable states in the presence of dissipation. Here we show that dissipation can enhance the stability of a quantum metastable system, consisting of a particle moving in a strongly asymmetric double well potential, interacting with a thermal bath. We find that the escape time from the metastable state has a nonmonotonic behavior versus the system-bath coupling and the temperature, producing a stabilizing effect.