The European Physical Journal B最新文献

We employ a procedure that enables us to calculate the excess free energies for a finite Ising cylinder with domain walls analytically. This procedure transparently covers all possible configurations of the domain walls under given boundary conditions and allows for a physical interpretation in terms of coarse-grained quantities such as surface and point tensions. The resulting integrals contain all the information about finite-size effects; we extract them by careful asymptotic analysis using the steepest descent method. To this end, we exactly determine the steepest descent path and analyse its features. For the general class of integrals, which are usually found in the study of systems with inclined domain walls, knowledge of the steepest descent path is necessary to detect possible intersections with poles of the integrand in the complex plane.

We systematically investigate the mechanical, electronic, and thermoelectric properties of the half-Heusler compound KBaBi using first-principles methods, including self-consistent phonon theory and the Boltzmann transport equation. Our results demonstrate that KBaBi maintains good thermal and mechanical stability at elevated temperatures. Importantly, this study incorporates higher-order anharmonic effects, especially four-phonon scattering, which are manifestations of nonlinear lattice dynamics. These nonlinear interactions drastically suppress the lattice thermal conductivity, reducing it to as low as 0.49 Wm(^{-1})K(^{-1}) at 800K. For electronic transport, we account for multiple scattering mechanisms to determine carrier relaxation times with improved accuracy. High band degeneracy near the valence band maximum leads to a large Seebeck coefficient under p-type doping. A peak dimensionless figure of merit zT of 3.22 is achieved at 800 K, highlighting KBaBi as a promising thermoelectric material with strong nonlinear phonon-limited thermal transport behavior.

Recently, a formal analogy between the fluctuating diffusivity and thermodynamics has been proposed based on phenomena of heterogeneous diffusion observed in living cells. This not only offers the analogs of the quantity of heat and work as well as the internal energy but also achieves that of the Clausius inequality for the entropy concerning diffusivity fluctuations. Here, a discussion is developed about constructing a heat-like engine in terms of the fluctuating diffusivity. The engine constitutes two kinds of processes with the average diffusivity or the average local temperature being kept fixed, along which the fluctuation distribution obeys an exponential law. The efficiency of the engine in a cycle, which quantifies how much the diffusivity change as the analog of work can be extracted, is found to formally coincide with that of Carnot’s. During the cycle, the total change of the entropy is also shown to vanish.

In collective local interaction systems with agents assigned to different profiles (categories, traits), the distribution of such profiles in the neighbourhood of any agent affects the exchange of ideas, a basic element in Collective Intelligence experiments. It is important to control this distribution experimentally, asking for criteria that should range from maximum homogeneity to maximum difference. We suggest a method where we obtain these criteria by adding an extra interaction term to the Q-state Potts model, producing a rich vacuum structure. By controlling the two parameters of the model, we can obtain different patterns for the geometrical distribution of the agents. We study the transitions and phase diagram of this model, considering the physics at constant magnetization, and show that the states correspond to a large diversity of mixing patterns, directly applicable to agent distribution in CI experiments.

This review focuses on the force-induced unzipping transition of double-stranded DNA. It begins with a brief history of DNA melting, which emerged alongside the growth of the field of molecular biology, juxtaposed with the advancements in physics during the same post-World War II period. The earlier theories of melting of DNA were based on the Ising model and its modifications, but gradually moved toward polymer-based models. The idea of force-induced unzipping was first introduced in 1999 as a cooperative mechanism for breaking base pairs without the need for temperature changes. The paper discusses several subsequent developments addressing different aspects of the unzipping transition.

We study coarsening in the nonconserved Ising model in (d=2) dimensions with long-range interactions decaying as (sim r^{-(d+sigma )}), employing Metropolis Monte Carlo computer simulations based on our recently conceived very efficient predecision scheme. By comparing numerical results between different quench temperatures we confirm the temperature independence of growth laws and show that a sensible choice of temperature may yield longer observation periods in coarsening studies.