International Journal of Theoretical Physics最新文献

The dynamic properties of the Einstein-Podolsky-Rosen (EPR) steering for a system comprised of two qubits which successively pass through a noisy channel with memory are investigated. We explore the behaviour of the EPR steering under three different channels with memory: amplitude damping channel, dephasing channel and depolarizing channel. Our results reveal that the memory effect of channel can effectively protect the EPR steering from the environmental noises. Especially, if the channel has perfect memory, the initial maximal EPR steering can be maintained all the time, so one can obtain steady and maximal steering which is meaningful for the task of quantum information processing. Besides, we find out that the hierarchy among entanglement, EPR steering and Bell nonlocality can be displayed distinctly under amplitude damping and depolarizing channel with partial memory.

In this article, the main objective is to analytical investigation of the third order Klein-Fock-Gordon eation and the nonlinear Maccari’s system. The Klein-Fock-Gordon equation have vital applications in quantum field theory, article physics, condensed matter physics, astrophysics and cosmology. On the other hand, the nonlinear Maccari’s system significantly explain the neural dynamics, cardiac rhythms, population dynamics and case study for theoretical analysis and the development of mathematical techniques. In order to develop the analytical exact soliton solutions for these considered nonlinear models, the modified Kudryashov’s and extended Kudryashov’s methods are utilized and numerous kinds of soliton wave structures constructed such as dark soliton, bright soliton, dark-bright soliton and exponential solutions which are not discussed before this study along with utilized analytical techniques. The obtained soliton solutions describe the propagation of spin-0 particles like mesons behave according to a relativistic wave equation in quantum field theory. The constructed soliton wave structures of the Klein-Gordon equation represent localized, stable, and particle-like excitations of the scalar field described by the equation and can be interpreted as "quasi-particles" or "wave packets" which propagate through the field while maintaining their shape and energy. The nonlinear Maccari’s system’s soliton profiles offer potential solutions for issues like information processing, signal transmission, and pulse shaping. They also provide a framework for comprehending and modifying wave-like phenomena in complex systems. The graphical demonstration of their propagation in three-dimensional, contour and two dimensional is presented with suitable parametric values.

Here, we explore the temporal dynamics of the quantum memory-assisted entropic uncertainty relation (QMA-EUR) and entanglement for particular states of a two-qubit system in the context of squeezed spin coherent states (SSCSs). For this reason, we examine the effect of spin squeezing, which is implemented by two kinds of one-axis twisting and two-axis counter-twisting nonlinearity Hamiltonians in the presence of an external field. Without loss of generality, we employ three types of maximally entangled states for a two-particle system, study the effect of squeezing, and determine the necessary conditions for the general squeezed two-qubit state that simultaneously provide the maximum amount of entanglement and tightness of the QMA-EUR. Finally, we introduce a new class of entangling operators and investigate the controlling role of the field in optimizing the QMA-EUR and entanglement.

We perform a matched asymptotic expansion to find an analytic formula for the trajectory of a light ray in a Schwarzschild metric, in a power series expansion in the deviation of the impact parameter from its critical value. We present results valid to second sub leading order in this expansion. We use these results to find an analytic expansion for the angular location of the (n^{th}) Einstein Ring (at large n) resulting from a star that lies directly behind a black hole but not necessarily far from it. The small parameter for this expansion is (e^{-pi (2n+1)}): our formulae are accurate to third order in this parameter.

It is known that the ensemble of random pure quantum states, constructed by bipartite maximally entangled states and random unitary matrices generated according to the Haar measure, exhibits an average entanglement entropy that obeys an area law. Our goal is to explore the entanglement entropy between the two subsystems in more detail. By employing techniques from Weingarten calculus and flow problems, we derive inequalities related to permutations. These inequalities lead to the conclusion that entanglement entropy almost surely follows an area law. We assert that these results persist even when replacing the Haar unitary random matrix with the Gaussian unitary ensemble. Finally, we illustrate our main results through two concrete examples.

In this paper, we present some explicit solutions for the 2D and 3D semi-stationary compressible Stokes problem, which is a gross simplification of the isentropic compressible Navier-Stokes equations. For the explicit solutions, the density is a function of time which decreases to zero at an exponential rate and the velocity is a combination of a time function and a quadratic polynomial with respect to the space variables.