Statistical Mechanics
Hubbard pair cluster with elastic interactions. Studies of thermal expansion, magnetostriction and electrostriction (1905.04379v2)
T. Balcerzak, K. Szałowski
2019-05-10
The pair cluster (dimer) is studied within the framework of the extended Hubbard model and the grand canonical ensemble. The elastic interatomic interactions and thermal vibrational energy of the atoms are taken into account. The total grand potential is constructed, from which the equation of state is derived. In equilibrium state, the deformation of cluster size, as well as its derivatives, are studied as a function of the temperature and the external magnetic and electric fields. In particular, the thermal expansion, magnetostriction and electrostriction effects are examined for arbitrary temperature, in a wide range of Hamiltonian parameters.
Thermodynamic cost and benefit of memory (1705.00612v2)
Susanne Still
2017-04-29
This letter exposes a tight connection between thermodynamic efficiency and predictive inference. A lower bound on dissipation is derived for partially observable information engines. It is shown that efficiency is limited by the retention of irrelevant information. A data representation strategy is derived from minimizing a lower bound on the dissipation of generalized information engines which use temperature differences. Predictive inference emerges as the best strategy.
Formulating the Kramers problem in field theory (1906.08684v1)
Arjun Berera, Joel Mabillard, Bruno W. Mintz, Rudnei O. Ramos
2019-06-20
The escape problem is defined in the context of quantum field theory. The escape rate is explicitly derived for a scalar field governed by fluctuation-dissipation dynamics, through generalizing the standard Kramers problem. In the presence of thermal fluctuations, there is a non-vanishing probability for a classical background field, initially located at a minimum of its potential in a homogeneous configuration, to escape from the well. The simple and well-known related problem of the escape of a classical point particle due to random forces is first reviewed. We then discuss the difficulties associated with a well-defined formulation of an escape rate for a scalar field and how these can be overcome. A definition of the Kramers problem for a scalar field and a method to obtain the rate are provided. Finally, we discuss some of the potential applications of our results, which can range from condensed matter systems, i.e., nonrelativistic fields, to applications in high energy physics, like for cosmological phase transitions.
Violation of the mean path length invariance property (1905.06840v2)
Federico Tommasi, Fabrizio Martelli, Lorenzo Fini, Stefano Cavalieri
2019-05-15
The invariance property of the mean path length is an astonishing law of Nature governing the motion of particles inside a disordered material. Whatever the strength of the disorder, the property states that the mean path length is exclusively determined by the ratio between the volume and the surface. Till now, the property has been reported as universal and valid in any kind of disordered medium and also beyond diffusion conditions. Nevertheless, we found out that the property fails in anomalous transport and in other kinds of random walk. By means of Monte Carlo simulations of light transport, we show that, in these cases, the invariance property loses its validity and the mean path length becomes dependent on the diffusive characteristics of the medium. The critical issue of such a violation lies in the breaking of isotropy and homogeneity of the radiance in the whole volume. These results are valid for all natural or artificial phenomena where random walkers, whatever their nature, are able to experiment anomalous transport.
Effective dynamics in an asymmetric death-branching process (1906.08630v1)
Pegah Torkaman, Farhad H. Jafarpour
2019-06-20
In this paper we study activity fluctuations in an asymmetric death-branching process in one-dimension. The model, which is a variant of the asymmetric Glauber model, has already been studied in [12]. It is known that in the low-activity region i.e. below the typical activity in the steady-state, the dynamical free energy of the system can be calculated exactly. However, the behavior of the system in the high-activity region is different and more interesting. The system undergoes a series of dynamical phase transitions. In present work we justify the hierarchy of dynamical phase transitions in terms of effective interactions in the system. It turns out that the effective interactions are long-range and that they can be described in terms of interactions between repelling shock fronts.
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