10 research outputs found
Heat transfer between nanoparticles: Thermal conductance for near-field interactions
We analyze the heat transfer between two nanoparticles separated by a
distance lying in the near-field domain in which energy interchange is due to
Coulomb interactions. The thermal conductance is computed by assuming that the
particles have charge distributions characterized by fluctuating multipole
moments in equilibrium with heat baths at two different temperatures. This
quantity follows from the fluctuation-dissipation theorem (FDT) for the
fluctuations of the multipolar moments. We compare the behavior of the
conductance as a function of the distance between the particles with the result
obtained by means of molecular dynamics simulations. The formalism proposed
enables us to provide a comprehensive explanation of the marked growth of the
conductance when decreasing the distance between the nanoparticles
Anomalous diffusion : a basic mechanism for the evolution of inhomogeneous systems
In this article we review classical and recent results in anomalous diffusion and provide mechanisms useful for the study of the fundamentals of certain processes, mainly in condensed matter physics, chemistry and biology. Emphasis will be given to some methods applied in the analysis and characterization of diffusive regimes through the memory function, the mixing condition (or irreversibility), and ergodicity. Those methods can be used in the study of small-scale systems, ranging in size from single-molecule to particle clusters and including among others polymers, proteins, ion channels and biological cells, whose diffusive properties have received much attention lately
Entropy, non-ergodicity and non-Gaussian behaviour in ballistic transport
Ballistic transportation introduces new challenges in the thermodynamic
properties of a gas of particles. For example, violation of mixing, ergodicity
and of the fluctuation-dissipation theorem may occur, since all these processes
are connected. In this work, we obtain results for all ranges of diffusion,
i.e., both for subdiffusion and superdiffusion, where the bath is such that it
gives origin to a colored noise. In this way we obtain the skewness and the
non-Gaussian factor for the probability distribution function of the dynamical
variable. We put particular emphasis on ballistic diffusion, and we demonstrate
that in this case, although the second law of thermodynamics is preserved, the
entropy does not reach a maximum and a non-Gaussian behavior occurs. This
implies the non-applicability of the central limit theorem.Comment: 9 pages, 2 figure
Khinchin theorem and anomalous diffusion
A recent paper [M. H. Lee, Phys. Rev. Lett. 98, 190601 (2007)] has called
attention to the fact that irreversibility is a broader concept than
ergodicity, and that therefore the Khinchin theorem [A. I. Khinchin,
Mathematical Foundations of Statistical Mechanics (Dover, New York) 1949] may
fail in some systems. In this Letter we show that for all ranges of normal and
anomalous diffusion described by a Generalized Langevin Equation the Khinchin
theorem holds.Comment: 4 pages, 3 figure
Equilibrium and nonequilibrium thermodynamics of a photon gas in the near field
In this paper, we study the near-field thermodynamics of a photon gas at equilibrium as well as out-of-equilibrium in the presence of dissipative effects. As a consequence of Heisenberg's uncertainty principle, we are able to eliminate the low-frequency modes in both cases, providing an analytical expression for the near-field entropy. In addition, we obtain the entropic-force contributions to the Casimir effect. At zero temperature the well-known 1/l^4 behavior of the pressure is obtained. In the nonequilibrium case, we compute the entropy production, showing that the excess of heat in each bodies must be dissipated into the respective thermal reservoirs
Anomalous diffusion : a basic mechanism for the evolution of inhomogeneous systems
In this article we review classical and recent results in anomalous diffusion and provide mechanisms useful for the study of the fundamentals of certain processes, mainly in condensed matter physics, chemistry and biology. Emphasis will be given to some methods applied in the analysis and characterization of diffusive regimes through the memory function, the mixing condition (or irreversibility), and ergodicity. Those methods can be used in the study of small-scale systems, ranging in size from single-molecule to particle clusters and including among others polymers, proteins, ion channels and biological cells, whose diffusive properties have received much attention lately