The European Physical Journal B最新文献

Kaniadakis ((kappa )-deformed) statistics is being widely used for describing relativistic systems with non-extensive behavior and/or interactions. It is built upon a one-parameter generalization of the classical Boltzmann–Gibbs–Shannon entropy, possessing the latter as a particular sub-case. Recently, Kaniadakis model has been adapted to accommodate the complexities of systems under the influence of gravity. The ensuing framework exhibits a rich phenomenology that allows for a deeper understanding of the most extreme conditions of the Universe. Here we present the state-of-the-art of (kappa )-statistics, discussing its virtues and drawbacks at different energy scales. Special focus is dedicated to gravitational and cosmological implications, including effects on the expanding Universe in dark energy scenarios. This review highlights the versatility of Kaniadakis paradigm, demonstrating its broad application across various fields and setting the stage for further advancements in statistical modeling and theoretical physics.

Complex networks offer a powerful framework for modeling linguistic phenomena. This study compares five distinct methods for representing sentences as networks, each with unique edge definitions: (1) a lines approach, where edges represent token (e.g., word) adjacency; (2) a close-range co-occurrence approach, where edges are based on the probability of tokens co-occurring at distance one or two; (3) a cliques approach, where edges connect tokens co-occurring within the same sentence; (4) a dependency-based approach, where edges are defined by syntactic dependencies extracted by a parser; (5) an IF-trimmed-subgraphs approach, where edges are determined by the Incidence-Fidelity (IF) Index. While the first four approaches are well established in the literature, the last one is a novel proposal. We also examined the effects of limiting the vertices to lemmas (i.e., words with inflections removed) and to lexical lemmas (i.e., nouns, adjectives, verbs, and adverbs) as opposed to the unaltered words. Our results reveal that these approaches yield networks with varying average minimal path lengths and degrees, influencing the interpretation of results. While small-world behavior remains consistent across networks, scale-free behavior analysis is affected. Notably, excluding functional words significantly alters degree distributions. We suggest, in order of relevance and according to the resources available, the dependency-based, the close-range co-occurrence, and the lines approaches for cases in which syntactic relations are central, and the IF-trimmed-subgraphs and the cliques approaches for cases in which semantic relations are central.

Representation of the sentence “we calculated two sets of adjusted values as follows” using five approaches - (1) the lines approach, (2) the close-range cooccurrence approach, (3) the cliques approach, (4) the dependency-based approach, and (5) the IF-trimmed-subgraphs approach - and three vertex definitions - (1) vertices representing unaltered words, (2) vertices representing lemmas, and (3) vertices representing lexical lemmas

This study rigorously investigates the phenomenon of a pseudo-transition in a minimal spin-pseudospin model, serving as a simplified model of one-dimensional cuprate chains [CuO](_infty ), by making use of the transfer-matrix method. The studied spin-pseudospin model of one-dimensional cuprate chains [CuO](_infty ) reveals a peculiar pseudo-transition between a charged-ordered phase and an antiferromagnetic phase, which is accompanied with anomalous behavior of magnetic and thermodynamic quantities. While the entropy and short-range correlations undergo near the pseudo-transition steep continuous changes reminiscent of a discontinuous phase transition, the specific heat displays a sizable sharp peak akin to a continuous phase transition.

A density plot of the specific heat of one-dimensional spin-pseudospin model of cuprate chain in the inter-site interaction versus temperature plane, which serves as a pseudo-phase diagram involving charged-ordered (CO) and antiferromagnetic (AF) phases

In this paper, we consider the phonons in monolayer graphene and we show the possibility for the spin-triplet superconducting excitations states by discretizing the single-particle excitations near Fermi wave vector. The monolayer graphene was supposed to be exposed under the influence of the external gate-potential and the local Coulomb interaction effects have been taken into account at each lattice site position in the monolayer. A sufficiently large temperature domain was found, where the superconducting order parameter is not vanishing. Corresponding to this, at the surprisingly high temperature limit, we obtain a narrow domain of the electron–phonon coupling parameter (lambda _textrm{eff}), emphasizing the superconducting state. We discuss the localizing role of Hubbard-U interaction and the effects external gate potential on the calculated physical parameters in the system. We explain the importance of the chemical potential in the formation of the superconducting state. We show the existence of a large superconducting band-gap in the system even in the case of the absence of the applied electric field potential.

We construct a quantum critical Otto engine that is powered by finite temperature baths. We show that the work output of the engine shows universal power law behavior that depends on the critical exponents of the working medium, as well as on the temperature of the cold bath. Furthermore, higher temperatures of the cold bath allows the engine to approach the limit of adiabatic operation for smaller values of the time period, while the corresponding power shows a maximum at an intermediate value of the cold bath temperature. These counterintuitive results stems from thermal excitations dominating the dynamics at higher temperatures.

In this work, we study and evaluate the impact of a periodic spin–lattice coupling in an Ising-like system on a 2D triangular lattice. Our proposed simple Hamiltonian considers this additional interaction as an effect of preferential phonon propagation direction augmented by the symmetry of the underline lattice. The simplified analytical description of this new model brought us consistent information about its ground state and thermal behavior, and allowed us to highlight a singularity where the model behaves as several decoupled one-dimensional Ising systems. A thorough analysis was obtained via entropic simulations based on the Wang–Landau method that estimates the density of states g(E) to explore the phase diagram and other thermodynamic properties of interest. Also, we used the finite-size scaling technique to characterize the critical exponents and the nature of the phase transitions that, despite the strong influence of the spin–lattice coupling, turned out to be within the same universality class as the original 2D Ising model.

Matrix product state methods are known to be efficient for computing ground states of local, gapped Hamiltonians, particularly in one dimension. We introduce the multi-targeted density matrix renormalization group method that acts on a bundled matrix product state, holding many excitations. The use of a block or banded Lanczos algorithm allows for the simultaneous, variational optimization of the bundle of excitations. The method is demonstrated on a Heisenberg model and other cases of interest. A large of number of excitations can be obtained at a small bond dimension with highly reliable local observables throughout the chain.