The European Physical Journal B最新文献

We consider a free-fermion chain undergoing dephasing, described by two different random-measurement protocols (unravelings): a quantum-state-diffusion and a quantum-jump one. Both protocols keep the state in a Slater-determinant form, allowing to address quite large system sizes. We find a bifurcation in the distribution of the measurement operators along the quantum trajectories, that’s to say, there is a point where the shape of this distribution changes from unimodal to bimodal. The value of the measurement strength where this phenomenon occurs is similar for the two unravelings, but the distributions and the transition have different properties reflecting the symmetries of the two measurement protocols. We also consider the scaling with the system size of the inverse participation ratio of the Slater-determinant components and find a power-law scaling that marks a multifractal behaviour, in both unravelings and for any nonvanishing measurement strength.

Position of the maxima of P n vs (gamma ) for the QSD protocol. The two maxima stem continuously and symmetrically at the bifurcation point (gamma ) QSD (sim 0.2), with a discontinuity of the derivative.

We use entanglement witnesses related to the entanglement negativity of the state to detect entanglement in the XY chain in the postquench states in the thermodynamic limit after a quench when the parameters of the Hamiltonian are changed suddenly. The entanglement negativity is related to correlations, which in the postquench stationary state are described by a generalized Gibbs ensemble, in the ideal case. If, however, integrability breaking perturbations are present, the system is expected to thermalize. Here, we compare the nearest-neighbor entanglement in the two circumstances.

Postquench states after a sudden quench protocol ((h_0, gamma ) rightarrow (h, gamma )) in the XY chain.

In the paper, we study the non-Hermitian system under dissipation and give the effective (2times 2) Hamiltonian in the k-space by reducing the (Ntimes N) Hamiltonian in the real space for them. It is discovered that the energy band shows an imaginary line gap. To describe these phenomena, we propose the theory of “non-Hermitian tearing” , in which the tearability we define reveals a continuous phase transition at the exceptional point. The non-Hermitian tearing manifests in two forms — separation of bulk state and decoupling of boundary state. In addition, we also explore the one-dimensional Su–Schrieffer–Heeger model and the Qi–Wu–Zhang model under dissipation using the theory of non-Hermitian tearing. Our results provide a theoretical approach for exploring the controlling of non-Hermitian physics on topological quantum states.

Effects of ballistic transport on the temperature profiles and thermal resistance in nanowires are studied. Computer simulations of nanowires between a heat source and a heat sink have shown that in the middle of such wires the temperature gradient is reduced compared to Fourier’s law with steep gradients close to the heat source and sink. In this work, results from molecular dynamics and phonon Monte Carlo simulations of the heat transport in nanowires are compared to a radiator model which predicts a reduced gradient with discrete jumps at the wire ends. The comparison shows that for wires longer than the typical mean free path of phonons the radiator model is able to account for ballistic transport effects. The steep gradients at the wire ends are then continuous manifestations of the discrete jumps in the model.

The second-order differential equation for the Uehling potential is derived explicitly. The right side of this differential equation is a linear combination of the two Macdonald’s functions (K_{0}(b r)) and (K_{1}(b r)). This central potential is of great interest in many QED problems, since it describes the lowest order correction for vacuum polarization in few- and many-electron atoms, ions, muonic and bi-muonic atoms/ions as well as in other similar systems.

We proposed a formally exact, probabilistic method to assess the validity of the Thomas–Fermi potential for three-dimensional condensed matter systems where electron dynamics is constrained to the Fermi surface. Our method, which relies on accurate solutions of the radial Schrödinger equation, yields the probability density function for momentum transfer. This allows for the computation of its expectation values, which can be compared with unity to confirm the validity of the Thomas–Fermi approximation. We applied this method to three n-type direct-gap III–V model semiconductors (GaAs, InAs, InSb) and found that the Thomas–Fermi approximation is certainly valid at high electron densities. In these cases, the probability density function exhibits the same profile, irrespective of the material under scrutiny. Furthermore, we show that this approximation can lead to serious errors in the computation of observables when applied to GaAs at zero temperature for most electron densities under scrutiny.

The Thomas-Fermi potential (V_textrm{ei}^textrm{TF}left( rright) ) and the the exponential cosine screened Coulomb potential (V_textrm{ei}^textrm{EC}left( rright) ) in coordinate space r, from the full interaction potential (V_textrm{ei}^textrm{RPA}left( qright) ) in the momentum space q at Random Phase approximation, through suitable Fourier transforms

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.