Modern Physics Letters A

In this paper, chiral chemical potential ${\mu }_5$ is introduced to investigate the QCD susceptibilities and chiral phase transition within the Polyakov-loop-extended Nambu–Jona-Lasinio models in the mean-field approximation. We concentrate on the effect of chiral chemical potential on the phase diagram and the QCD susceptibilities. Moreover, it is worth noting that chiral chemical potential has more and more prominent impact on the susceptibilities and the phase diagram with the decrease of temperature based on our results, which coincides with the prediction that the chiral symmetry is dynamically broken in the first-order phase transition region and gets partly restored in the crossover region.

The renormalization group flow of the chiral Nambu–Jona-Lasinio (NJL) model with one fermion flavor is mapped out in the symmetric phase with help of the Functional Renormalization Group (FRG) method using a physically motivated nonlocal trial effective action. The non-interacting infrared end-point of the flow of the four-fermion couplings is now accompanied by nonzero limiting composite couplings characteristic for interacting two-particle states with finite energy and physical size. The interaction energy of the constituents is extracted as a function of the physical size of the composite object. The propagation of a two-particle state minimizing the interaction energy has a natural bound state interpretation.

A correspondence between the equivalence principle and the homogeneity of the universe is discussed. In Newtonian gravity, translation of co-moving coordinates in a uniformly expanding universe defines an accelerated frame. A consistency condition for the invariance of this transformation which requires a well-defined transformation for the Newtonian potential, yields the Friedmann equations. All these symmetries are lost when we modify Newton’s Second Law (NSL) or the Poisson equation. For example, by replacing NSL with nonlinear function of the acceleration, the concept of relative acceleration is lost and the homogeneity of the universe breaks.

In this work, we investigate the thermodynamic and the stability of the regular Hayward black hole surrounded by quintessence. Using the metric of the black hole surrounded by quintessence and the new approach of the holographic principle, we derive the expression of the Unruh–Verlinde temperature. Hawking temperature and specific heat are derived using the first law of black holes thermodynamics. Gibbs free energy is also evaluated. The behaviors of these quantities show that, the parameter of the regular Hayward black hole $\beta$ induces a decreasing of the Hawking temperature of the black hole, and that decrease is accentuated when increasing the magnitude of $\beta$ and the normalization factor related to the density of quintessence. For the lower entropies, the black hole passes from the unstable phase to the stable one by a first-order thermodynamics phase transition. When increasing the entropy, a second phase transition occurs. This new phase transition is a second-order thermodynamics phase transition and brings the black hole to unstable state. It results that, when increasing of magnitude of $\beta$, the phase transition points are shifted to the higher entropies. Moreover, the phenomena of phase transitions are preserved by adding the quintessence. Furthermore, when increasing the normalization factor of quintessence, the first-order transition point is shifted to higher entropies, while the second-order thermodynamics phase transition point is shifted to lower entropies.

We are engaged in studying thermodynamics of black holes from quantum mechanical perspective and already have published a series of papers. We first showed, based on certain assumptions for quantum mechanical nature of black holes, that they can be thought to be immersed in a thermal bath, i.e. rest of the universe. Of course, this consideration is required to study the thermodynamics of the black holes. We were able to find out the conditions of thermal stability for a black hole with arbitrary number of hairs in arbitrary dimensional spacetime. They came in form of a series of inequalities, connecting second-order derivatives of black hole mass with respect to its area and all the hairs. We then introduced the concept of “Quasi stability”, based on partial fulfillment of stability criteria, for thermally decaying black holes. We had also calculated the fluctuations for different hairs of a stable black hole. In this paper, we extend this calculation for charged rotating quasi-stable black holes. These fluctuations are interestingly found to be similar to that of stable black holes in certain aspects.

Non-commutative space-time is discussed for discrete case. An exact discretization of the non-commutative space-time is proposed. New discrete operators, which satisfy the same algebraic relations as standard derivatives of integer orders, are used. Exact discretization of the non-commutative space-time is suggested by using generalization of the star-product (the Moyal–Weyl product) based on the recently proposed exact finite differences. The suggested discrete non-commutative space-time corresponds to the standard “continuous” non-commutative space-time without any approximations. The suggested discrete non-commutative space-time can be interpreted as a special physical (crystal) lattice with long-range interaction.

The main features of obtaining the asymptotic behavior of the electric structure function $A(p)$ at large values of the transmitted momentum are analyzed. The asymptotic behavior of the structure function $A(p)$ was determined to take into account the asymptotic behavior of the deuteron form factors and the original dipole approximation for the nucleon form factors. Asymptotic values of $A(p)$ were obtained for the nucleon–nucleon potential Reid93 and compared with the calculations for different nucleon form factor models and their approximations. In the broad momentum range up to 12.5 fm${}^{-1}$, the basic forms of the asymptotic behavior of the electric structure function are demonstrated and compared with the experimental data of the modern collaborations. As the analysis shows in most cases considered, the asymptotic for $A(p)$ is represented in the form of the power function $p^{-n}$.

A stellar model with anisotropic pressure is constructed and analyzed, the metric components that describe the geometry and the source of matter satisfy Einstein’s equations and both are finite inside the star. In addition, density and pressure are decreasing monotone functions of the radial distance. The speed of sound is positive and less than the speed of light, furthermore the model is potentially stable. The model allows describing compact objects with compactness of $u\le 0.3160174032$ and as a result of the anisotropic value there is a range of values of the central density, in particular for the maximum value of compactness a star with $1M_{\odot }$ and a value of anisotropic parameter $\alpha =-3.0168$ we get a stellar radius of $4.6721\mathrm{\text{km}}$ and a central density ${\rho }_c=9.4070{\mathrm{\text{Kg/m}}}^3$. The above makes the solution a physically realistic model that can be used to describe dense objects such as neutron stars whose characteristic density is of the order of nuclear density.

Starting from a perfect fluid solution we constructed a generalization with anisotropic pressures and regular geometry as well as the pressures, the density and the speed of sound, these are also positive and monotonic decreasing functions. The speed of sound is lower than the speed of light, that is to say, the condition of causality is not broken. The model satisfies all the energy conditions and the radial $v_r$ and tangential $v_t$ speeds and complies with $-1<v_t^2-v_r^2<0$ because of this the solution is stable according to the stability criteria related with the concept of cracking. The maximum value of the compactness factor $u=GM/c^{2}R\le 0.2950$ which is lower than the Buchdahl limit and associated to neutron stars. In a complementary manner, we realize an analysis of the behavior of a star with a mass of $1.3M_{\odot }$, with a fixed value of the anisotropy parameter and different compactness values, giving as a result that their central density ${\rho }_c\in [0.1421,3.0670]\times 10^{18}{\mathrm{\text{kg/m}}}^3$ and the superficial density ${\rho }_b\in [0.1237,1.6785]\times 10^{18}{\mathrm{\text{kg/m}}}^3$, the maximum values match the value of greater compactness of the model with a stellar radius of 6506.921 m.

In the course of study of the evolution of the universe, it is seen that perhaps the extra energy generated and particles created due to the accelerated expansion of the universe might be absorbed by the dark energy and dark matter which are already existing in this universe. It is found that the energy density of dark energy can be expressed as a function of the energy density of the remaining matter portion of the universe which shows that the different components of the universe are correlated. According to the forms of the different types of interaction occurring between dark energy and the other different contents of the universe it may be possible to utilize the dark energy in different ways as it may take different forms of energy. As an interesting phenomenon, it is also observed that the concept of negative time may exist in this universe, and it may revolutionize some of the original concepts of nature and the physical world.

High-dimensional quantum system plays an important role in quantum information tasks. However, the interaction between quantum system and environment would give rise to decoherence. In this paper, we examine the quantum-memory-assisted entropic uncertainty relation under amplitude damping (AD) decoherence. It is found that entropic uncertainty first inflates and then reduces to a nonzero value with the growing decoherence strength. In addition, it is revealed that the mixedness is not closely associated with entropic uncertainty which is different from the previous result. Furthermore, we construct a remarkably effective filtering operator to steer and reduce the entropic uncertainty. Our exploration might offer fresh insights into the dynamics and manipulation of the entropic uncertainty in high-dimensional quantum system.