International Journal of Theoretical Physics最新文献

The decay widths of (V rightarrow K(pi ) l bar{nu }_l ) are calculated within the Nambu–Jona-Lasinio model, where (V=K^*, rho , omega , phi ) and (l=mu , e). The results are obtained using the previously fixed model parameters without introducing any arbitrary parameters. The obtained results are considered as predictions due to the absence of experimental data.

This study employs the Blume–Emery–Griffiths model and Monte Carlo simulations to analyze the magnetization plateaus and hysteresis cycles in a C₆₀ fullerene-like system. The behavior of these hysteresis cycles and magnetization plateaus is significantly influenced by key factors such as temperature (T), crystal field (D), bilinear exchange coupling (J), and biquadratic exchange coupling (K). Our results enhance the understanding of the magnetic properties of the C₆₀ fullerene-like system and provide new insights into the complex interactions governing hysteresis cycles and magnetization plateaus. These findings have important implications for future advancements in nanotechnology and spintronics.

The electron tunneling in the ZnO/ZnCdO resonant tunnel barrier is theoretically investigated to study the role of the in-plane magnetic field. The transfer matrix method is applied to understand the effect of spin–orbit interaction for various magnetic fields. The Dresselhaus spin–orbit interaction and the spin-dependent Zeeman splitting result in the spin-separation in this heterostructure. The externally applied in-plane magnetic field enhances the energy separation between the spin components. The observed dwell time is in the order of microseconds. As the magnetic field increases, the degree of spin polarization enhances and one can obtain a high degree of spin –polarization at a high magnetic field. The energy of resonance shifts to a high value as the height of the delta potential increases. The degree of spin-polarization also depends on the delta potential.

We introduce a specific deformed Bose gas model, whose underlying quasiparticle algebra is related to the κ-deformed bosonic oscillator algebra. We then develop the statistical distribution function of a gas model of the κ-deformed bosons containing finite and infinite dimensional cases. We investigate interpolating statistics behavior of this deformed model and apply it to lattice oscillations via the Debye crystal model. The effect of the deformation parameter κ onto the low-temperature behavior of the model specific heat is discussed and is compared with the results of both the standard phonon gas and the ones with the Tsallis non-extensive statistics. Another application is carried out onto the Bose-like condensation of this deformed model and the conditions under which the κ-deformed boson condensation would occur in such a system are discussed. It is shown that the critical temperature of the κ-deformed boson gas with the infinite dimensional case is higher than that of the ideal Bose gas, while it has lower values than those of the ideal Bose gas for the finite dimensional case. We consider that the results obtained in this work may provide much physical insight into further studies on strongly correlated quantum materials as well as interacting theories of bosons including collective excitations, where unconventional quantum statistics might have an important role.

We study the emergence of canonically typical states in the group field theory approach to quantum gravity. Based on the Page-Wootters formalism for emergent relational time/dynamics in a closed quantum system that has been recently generalized to group field theory, we can derive the emergent canonically typical states by choosing a complex relational time parameter. When the time parameter can be related to the spacetime diffeomorphism of the to be emerged spacetime, the canonically typical states can be interpreted as the thermal states of group field theory, which then greatly simplifies the previous constructions of thermal states for group field theory found in the literature.

In this study, we use the Legendre spectral collocation method to analyze the stability of a system of fractional diffusion-reaction equations, due to its capacity to simulate a variety of biological and physical processes with irregular diffusion properties. It causes that understanding such systems’ long-term behavior requires a study of stability analysis. The stability criteria are rigorously analyzed through mathematical techniques. This is done after discretizing the equations using the Legendre spectral collocation method. With the intention of predicting system dynamics and creating numerical algorithms, our findings offer discernment into the behavior of stability analysis for fractional diffusion-reaction systems.

The theoretical security of continuous variable quantum key distribution (CV-QKD ) has been proved. However the gap between the theoretical model and the practical model can lead to the threat of the actual security of CV-QKD system in practice. An eavesdropper can use the imperfection of the homodyne detector to perform the saturation attacks. She can successfully obtain information without being detected by legitimate communication parties. In this paper, we analyze saturation attacks through atmospheric channels in CV-QKD system, and use mean-limited least square method to fit straight lines to defend against saturation attacks. Simulation results show that legal participants evaluate the information that has been eavesdropped because the secret key rate is negative.

The idea of a quantum heat engine (QHE) is an interesting problem in physics and engineering. The Stirling QHE is widely used in the field of quantum machines due to the simplicity of the Stirling cycle. In the present work, the performance of the Stirling QHE is examined by treating its working substance as a two-qubit Heisenberg model taking into account the Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) interaction, and a magnetic field within the framework of the Tsallis formalism. The novelty of the work is to use the non-extensive formalism to investigate the quantum Stirling engine. We study the influence of the non-extensive Tsallis parameter ((q)), KSEA parameter, and magnetic field on various aspects of the Stirling heat engine, including absorbed heat, released heat, work done, and efficiency. The best value for the efficiency of this QHE can be obtained by setting sufficient values for the system parameters such as the non-extensive parameter, KSEA parameter, and magnetic field. Here, we obtained a maximum value of 0.12 for the efficiency of the QHE at (q)= 0.95.

Using the symmetry-preserving vector-vector contact interaction model within the Schwinger-Dyson equation framework, we investigate the QCD phase diagram under the influence of an external magnetic field eB, at finite temperature T and quark chemical potential (mu ). At finite temperature, when the magnetic field effect is not included in the effective coupling of the contact interaction, we observe the magnetic catalysis (MC) effect. However, when we account for the magnetic field eB in the effective coupling, we observe the magnetic inhibition effect, or inverse magnetic catalysis (IMC). At finite temperature T and chemical potential (mu ), we construct the QCD phase diagram in the presence of a magnetic field, considering both cases with and without eB-dependent contact interaction coupling. Our findings indicate that the entire critical line separating the chiral symmetry breaking-confinement phase from the chiral symmetry restoration-deconfinement phase is enhanced without eB-dependent interactions, while it is suppressed with such interactions. Additionally, we identify the effects of the magnetic catalysis (MC) and inverse magnetic catalysis (IMC) on the positioning of the critical endpoint.

Munero et al. developed one parameter family of mixed states (varvec{rho ^{l}}), which are more entangled than bipartite Werner states. The similar family of mixed states (varvec{rho ^{n}}) are developed by Ł. Derkacz et al. with different approach. Further the authors extended (varvec{rho ^{n}}) to two parameter family of quantum states (varvec{rho ^{m}}) and characterized these states in terms of Bell inequality violation against their mixedness. In the present article, we investigate the comparative dynamics of all mixed states (varvec{(rho ^{l},rho ^{n},rho ^{m})}) under the bipartite Ising Hamiltonian exposed by the external magnetic field and investigate the dynamics of quantum correlations against the mixedness quantified by linear entropy.