Latest Papers in Condensed Matter Physics

Statistical Mechanics

---

Seeking Fixed Points in Multiple Coupling Scalar Theories in the Expansion (1707.06165v7)

Hugh Osborn, Andreas Stergiou

2017-07-19

Fixed points for scalar theories in , and dimensions are discussed. It is shown how a large range of known fixed points for the four dimensional case can be obtained by using a general framework with two couplings. The original maximal symmetry, , is broken to various subgroups, both discrete and continuous. A similar discussion is applied to the six dimensional case. Perturbative applications of the -theorem are used to help classify potential fixed points. At lowest order in the -expansion it is shown that at fixed points there is a lower bound for which is saturated at bifurcation points.

Maxwell's Demon, Szilard Engine and Landauer Principle (1904.05256v1)

P. S. Pal, A. M. Jayannavar

2019-04-10

The second law of thermodynamics is probabilistic in nature. Its formulation requires that the state of a system be described by a probability distribution. A natural question, thereby, arises as to whether a prior knowledge about the state of the system affects the second law. This question has now been nurtured over a century and its inception was done by C. Maxwell through his famous thought experiment wherein comes the idea of Maxwell's demon. The next important step in this direction was provided by L. Szilard who demonstrated a theoretical model for an information engine incorporating Maxwell's demon. The final step that lead to the inter-linkage between information theory and thermodynamics was through Landauer's principle of information erasure that established the fact that information is physical. Here we will present an overview of these three major works that laid the foundations of information thermodynamics.

Rate dependence of current and fluctuations in jump models with negative differential mobility (1904.05241v1)

Gianluca Teza, Stefano Iubini, Marco Baiesi, Attilio L. Stella, Carlo Vanderzande

2019-04-10

Negative differential mobility is the phenomenon in which the velocity of a particle decreases when the force driving it increases. We study this phenomenon in Markov jump models where a particle moves in the presence of walls that act as traps. We consider transition rates that obey local detailed balance but differ in normalisation, the inclusion of a rate to cross a wall and a load factor. We illustrate the full counting statistics for different choices of the jumping rates. We also show examples of thermodynamic uncertainty relations. The variety of behaviours we encounter highlights that negative differential mobility depends crucially on the chosen rates and points out the necessity that such choices should be based on proper coarse-graining studies of a more microscopic description.

Models of infiltration into homogeneous and fractal porous media with localized sources (1904.05231v1)

Fabio D. A. Aarao Reis, Vaughan R. Voller

2019-04-10

We study a random walk infiltration (RWI) model, in homogeneous and in fractal media, with localized sources at their boundaries. The particles released at a source, which is maintained at a constant density, execute unbiased random walks over a lattice; it represents solute infiltration by diffusion into a medium in contact with a reservoir. A scaling approach shows that the infiltrated length, area, or volume evolves in time as the number of distinct sites visited by a single random walker in the same medium. This is consistent with simulations of the lattice model and exact and numerical solutions of the corresponding diffusion equation. In a Sierpinski carpet, the infiltrated area is expected to evolve as t^{D_F/D_W} (Alexander-Orbach relation), where D_F is the fractal dimension of the medium and D_W is the random walk dimension; the numerical integration of the diffusion equation supports this relation and improves results of lattice random walk simulations. In a Menger sponge in which D_F>D_W (a fractal with a dimension close to 3), a linear time increase of the infiltrated volume is predicted and confirmed numerically. Thus, no evidence of fractality can be observed in infiltrated volumes or masses in media where random walks are not recurrent, although the tracer diffusion is anomalous. We compare our results with a fluid infiltration model in which the pressure head is constant at the source and the front displacement is driven by the local gradient of that head. Exact or numerical solutions in two and three dimensions and in a carpet show that this type of fluid infiltration is in the same universality class of RWI, with an equivalence between the head and the particle concentration. These results set a relation between different infiltration processes with localized sources and the recurrence properties of random walks in the same media.

Long-distance entanglement in Motzkin and Fredkin spin chains (1904.05205v1)

Luca Dell'Anna

2019-04-10

We derive some entanglement properties of the ground states of two classes of quantum spin chains described by the Fredkin model for half-integer spins and the Motzkin model for integer ones. Since the ground states of the two models are known analytically, we can calculate the entanglement entropy, the negativity and the quantum mutual information exactly. We show, in particular, that these systems exhibit long-distance entanglement, namely two disjoint regions of the chains remain entangled even when the separation is sent to infinity, i.e. these systems are not affected by decoherence. This strongly entangled behavior is consistent with the violation of the cluster decomposition property occurring in the case of colorful versions of the models (with spin larger than 1/2 or 1, respectively), but is also verified for colorless cases (spin 1/2 and 1). Moreover we show that this behavior involves disjoint segments located both at the edges and in the bulk of the chains.

---

Thank you for reading!

Don't forget to Follow and Resteem. @arxivsanity
Keeping everyone inform.