International Journal of Modern Physics A

This review is intended for readers who want to have a quick understanding on the theoretical underpinnings of coherent states and squeezed states which are conventionally generated from the prototype harmonic oscillator but not always restricting to it. Noting that the treatments of building up such states have a long history, we collected the important ingredients and reproduced them from a fresh perspective but refrained from delving into detailed derivation of each topic. By no means we claim a comprehensive presentation of the subject but have only tried to recapture some of the essential results and pointed out their interconnectivity.

Using the corresponding Mellin–Barnes representation, we derive holonomic hypergeometric system of linear partial differential equations (PDEs) satisfied by Feynman integral of a three-loop vacuum with five propagators. Through the multidimensional residue theorem in dimensional regularization, the scalar integral can be written as the summation of multiple hypergeometric functions, whose convergent regions can be obtained by the Horn’s convergent theory. The numerical continuation of the scalar integral from convergent regions to whole kinematic regions can be accomplished with the finite element methods, when the system of PDEs can be treated as the stationary conditions of a functional under the restrictions.

Taking de Sitter space–time as a thermodynamic system, we study the effects of quantum gravity on thermodynamic quantities of de Sitter black holes in massive gravity. We enumerate the leading order corrections arising in quantum gravity regime on various thermodynamic quantities like Helmholtz free energy, Gibbs free energy, specific heat and pressure. Our results show that quantum corrections have tendency to induce stability. Moreover we observe that the parameters from the massive gravity have deeper effect on the evolution of de Sitter space–time in quantum gravity regime. Such an analysis could be helpful in understanding inflation and evolution of universe at early times.

It is well known that near horizon black hole space–times show a resemblance to thermodynamic systems, it is easy to associate the thermodynamic parameters like temperature and entropy with them. In this paper, we study the connection between gravitational dynamics of the horizon and thermodynamics for the case of charged radiating rotating axially symmetric black holes. It is shown that Einstein field equation near apparent horizon can be interpreted in the form of thermodynamic law, i.e. $TdS=dM(v)-{\mathrm{\Omega }}_{H}dJ-\mathrm{\Phi }dQ(v)$.

In this paper the decays of $B_c^{+}\to D_s^{\ast +}{\bar{D}}^{\ast 0}$, $B_c^{+}\to D_s^{\ast +}{D}^{\ast 0}$, $B_c^{+}\to D^{\ast +}{\bar{D}}^{\ast 0}$ and $B_c^{+}\to D^{\ast +}{D}^{\ast 0}$ have been investigated. The available experimental results for these decays are (in units of $10^{-5}$):

In this work we continue our previous studies concerning the possibility of the existence of a Bose–Einstein condensate in the interior of a static black hole, a possibility first advocated by Dvali and Gómez. We find that the phenomenon seems to be rather generic and it is associated to the presence of a horizon, acting as a confining potential. We extend the previous considerations to a Reissner–Nordström black hole and to the de Sitter cosmological horizon. In the latter case the use of static coordinates is essential to understand the physical picture. In order to see whether a BEC is preferred, we use the Brown–York quasilocal energy, finding that a condensate is energetically favorable in all cases in the classically forbidden region. The Brown–York quasilocal energy also allows us to derive a quasilocal potential, whose consequences we explore. Assuming the validity of this quasilocal potential allows us to suggest a possible mechanism to generate a graviton condensate in black holes. However, this mechanism appears not to be feasible in order to generate a quantum condensate behind the cosmological de Sitter horizon.

In this paper, one discusses the effects of Tsallis entropy on the radial pressure distribution in the proton. Using a damped confinement potential the pressure distribution is obtained from the Tsallis entropy approach, being the entropic-index $\omega$ connected with the proton temperature concerning some transition temperature. Then, the approach allows the study of the proton thermal evolution up to the Quark–Gluon Plasma regime. The von Laue stability condition, arising from the pressure distribution results in positive and negative energy regions. An analogy between the results for the radial pressure distribution and the proton–proton and the antiproton–proton total cross-section is performed. The negative energy region is identified with the odderon exchange while the positive represents the pomeron exchange dominance above some transition energy $\sqrt{s_c}$. The hollowness effect is also discussed in terms of the results obtained and the proposed analogy.

There is an interesting but not-so-popular quantity called pseudo orbital angular momentum (OAM) in the Landau-level system, besides the well-known canonical and mechanical OAMs. The pseudo OAM can be regarded as a gauge-invariant extension of the canonical OAM, which is formally gauge invariant and reduces to the canonical OAM in a certain gauge. Since both of the pseudo OAM and the mechanical OAM are gauge invariant, it is impossible to judge which of those is superior to the other solely from the gauge principle. However, these two OAMs have totally different physical meanings. The mechanical OAM shows manifest observability and clear correspondence with the classical OAM of the cyclotron motion. On the other hand, we demonstrate that the standard canonical OAM as well as the pseudo OAM in the Landau problem is the concept which crucially depend on the choice of the origin of the coordinate system. We try to reveal the relation between the pseudo OAM and the mechanical OAM as well as their observability by paying special attention to the role of guiding-center operator in the Landau problem.

We propose the pure natural quintessential inflation model which is motivated by Witten’s conjecture, where the axion couples to pure Yang–Mills $SU(N)$ gauge field at large $N$ limit. This modifies the standard cosine potential which is presented in the natural inflation, making it compatible with current CMB data. Our model gives a successful inflation as well as acceleration at the late times by quintessence inflaton field ($\varphi$). Here the inflaton field is responsible for inflation, after that the field enters into peculiar type of reheating and then they act as dynamical dark energy field which follows the same inflation potential and same model parameters. The dynamical field slowly rolls until the Hubble drops to mass of the quintessence field and it reaches the current dark energy field value. Here the dark energy scale is field dependent. Our quintessence model follows thawing frozen approach, therefore the frozen quintessence field evolves with respect to cosmic time from initial field value $({\varphi }_i)$ to present nonzero minimum field value $({\varphi }_0)$. The obtained field value turned into ultralight and it satisfies the present dark energy density which is $V({\varphi }_0)\approx {\mathrm{\Lambda }}_{\text{DE}}^4={(2.3\times 10^{-3}\text{eV})}^4$.

In this paper, the linearized field equations related to the quadratic curvature gravity theory have been obtained in the four-dimensional de Sitter (dS) space–time. The massless spin-2 field equations have been written in terms of the Casimir operators of dS group making use of the ambient space notations. By imposing some simple constraints, arisen from group theoretical interpretation of the field equations, a new four-dimensional Gauss–Bonnet (GB-)like action has been introduced with the related field equations transforming according to the unitary irreducible representations (UIRs) of dS group. Since, the field equations transform according to the UIRs of dS group, the GB-like action, we just obtained, is expected to be a successful model of modified gravity. For more clarity, the gauge invariant field equations have been solved in terms of a gauge-fixing parameter ${𝒞}$. It has been shown that the solution can be written as the multiplication of a symmetric rank-2 polarization tensor and a massless minimally coupled scalar field on dS space. The Krein–Gupta–Bleuler quantization method has been utilized and the covariant two-point function has been calculated in terms of the massless minimally coupled scalar two-point function, using the ambient space notations. It has been written in terms of dS intrinsic coordinates from the ambient space counterpart. The two-point functions are dS invariant and free of any theoretical problems. It means that the proposed model is a successful model of modified gravity and it can produce significant results in the contexts of classical theory of gravity and quantum gravity toy models.