International Journal of Modern Physics A

Whenever one has witnessed some event and then sees it reported in the media, one’s reaction is the same: it was not quite like that. It is in this spirit of a frequent first-hand witness that I write this article. I discuss a few selected points which — to my judgement — illustrate well the QCD evolution (in time) from the theoretical, phenomenological and experimental points of view.

We determine and classify the electric-magnetic duality orbits of fluxes supporting asymptotically flat, extremal black branes in $D=4,5,6$ space–time dimensions in the so-called nonsupersymmetric magic Maxwell–Einstein theories, which are consistent truncations of maximal supergravity and which can be related to Jordan algebras (and related Freudenthal triple systems) over the split complex numbers ${ℂ}_s$ and the split quaternions ${ℍ}_s$. By studying the stabilizing subalgebras of suitable representatives, realized as bound states of specific weight vectors of the corresponding representation of the electric-magnetic duality symmetry group, we obtain that, as for the case of maximal supergravity, in magic nonsupersymmetric Maxwell–Einstein theories there is no splitting of orbits, namely there is only one orbit for each nonmaximal rank element of the relevant Jordan algebra (in $D=5$ and 6) or of the relevant Freudenthal triple system (in $D=4$).

This work deals with the Duffin–Kemmer–Petiau (DKP) field theory. The structure of the wave functions is analyzed for the scalar and vector sectors for particles with spin 0 and spin 1. The finite temperature is introduced using Thermo Fields Dynamics (TFD). It is a mathematical approach which involves doubling of the Hilbert space to introduce finite temperature. Results for Stefan–Boltzmann law and Casimir effect in DKP field are calculated at finite temperature.

In this paper, we have explored the behavior of dynamics of neutral test particles near the brane-world black hole (BH). We have discussed the stability/instability near the circular orbits with the help of extremal and nonextremal BH. In this consideration, we investigate the last stable circular orbit $(r_{\mathrm{\text{LSCO}}})$ that decreases with the increase of black hole parameters and concluded that the circular orbits are stable at $r>r_{\mathrm{\text{LSCO}}}$. The effective potential vanishes at horizon in extremal BH. In case of nonextremal BH, the angular momentum decreases, whereas energy increases with the increase in dark parameter $\beta$. Moreover, we find the conditions for the naked singularity and also express the effective potential that increases with the increase of angular momentum. Finally, the center-of-mass energy (CME) is constructed by the collision of particles in the vicinity of brane-world black hole and observed that the CME decreases with the increase of black hole parameters.

We show that Supersymmetric effects driven by penguin contributions to the $b\to c\tau {\nu }_{\tau }$ transition are able to account simultaneously for a sizeable increase of both branching ratios of $\bar{B}\to D\tau {\bar{\nu }}_{\tau }$ and $\bar{B}\to D^{\ast }\tau {\bar{\nu }}_{\tau }$ with respect to the Standard Model predictions, thereby approaching their experimentally measured values. We emphasize that a light chargino and neutralino, with masses less than 300 GeV, in addition to a large stau/sneutrino mass and a large $tan\beta$, are essential for enhancing the effect of the lepton penguin $\tau {\nu }_{\tau }{W}^{\pm }$, which is responsible for the improved theoretical predictions with respect to current data.

In this paper, we develop a complexity factor for static sphere in modified Gauss–Bonnet gravity with anisotropic and nonhomogeneous configuration. We use the field equations as well as equation of continuity to derive expressions for mass function in $f({𝒢})$ gravity. The Riemann tensor is split using Bel’s approach to formulate structure scalars that exhibit fundamental properties of the system. A complexity factor is developed on the basis of these scalars and the condition of vanishing complexity is used to obtain solutions of two different models. It is observed that modified terms increase complexity of the matter distribution.

We study thermodynamics and quantum tunneling of the Reissner–Nordström black hole with deficit solid angle and quintessence. We employ black hole thermodynamical laws and Parikh–Wilczek’s semiclassical tunneling process to obtain expressions of some thermodynamics quantities, Boltzmann factor, and entropy variation of the black hole. Regarding black hole background as dynamical and using conservation laws for energy and charge, we detect the existence of unthermal radiation spectrum and dependence of Boltzmann factor on the background geometry, and on energy and charge of the radiant particle. We explicitly plot variations of temperature, heat capacity, Boltzmann factor, and entropy change for various values of deficit solid angle $𝜖$ and quintessence density ${\rho }_0$. When varying the black hole entropy, there exists a phase transition, which shifts to lower entropy for increasing ${\rho }_0$ and decreasing ${𝜖}^2$. We show that temperature, heat capacity, and quantum tunneling rate are decreased in presence of quintessence and deficit angle parameters.

We study the production of gravitational waves from primordial scalar perturbations in a string axion inflationary model with subleading nonperturbative corrections. In such a model, the subleading nonperturbative effects can superimpose steep cliffs and gentle plateaus onto the leading axion potential. Such an inflationary potential both matches the Planck observations at CMB scales and gives rise to an enhancement in the scalar power spectrum at small scales. We calculate the second-order gravitational wave signatures induced by the scalar density perturbations, and find that the signal can be detected by the space-based laser interferometers in the future.

We investigate the influence of the different vertices of two-point correlation functions in the infrared regime of Yang–Mills theory using a phenomenological description. This regime is studied in Landau-gauge and using perturbation theory within a phenomenological massive model. We perform a one-loop calculation for two-point correlation functions taking into account the different roles of the various interactions in the infrared. Our results show a good agreement with the lattice data.

We consider the grand canonical ensemble of the static and extremal black holes, when the equivalence of the electric charge and mass of individual black hole is postulated. Assuming uniform distribution of black holes in space, we are finding the effective mass of test particle and mean time dilation at the admissible points of space, taking into account the gravitational action of surrounding black holes. Having specified the statistics that governs extremal black holes, we study its effect on those quantities. Here, the role of statistics is to assign a statistical weight to the configurations of certain fixed number of black holes. We borrow these weights from Bose–Einstein, Fermi–Dirac, classical and infinite statistics. Using mean field approximation, the aforementioned characteristics are calculated and visualized, which permits us to draw the conclusions on visible effect of each statistics.

It has been found recently that the entropy relations of horizons have the universality of black hole mass-independence for many black holes. These universal entropy relations have some geometric and CFT understanding, which may provide further insight into the quantum physics of black holes. In this paper, we present the leading order of black hole entropy sum relations under the quantum corrections. It is found that the modified entropy sum becomes mass-dependent for some black holes in asymptotical (A)dS and flat space–times. We also give an example that the modified entropy sum of regular Bardeen AdS black holes is mass-independent, which may be quantized in the form of the electric charge and the cosmological constant.

In this paper, for the sake of providing a concrete comparison between the usual Abbott–Deser–Tekin (ADT) formalism and its off-shell extension, as well as comparing the latter with the Barnich–Brandt–Compere (BBC) approach, we carry out these methods to compute the mass and angular momentum of the rotating charged Gödel black holes in five-dimensional minimal supergravity. We first present the off-shell ADT potential of the supergravity theories in arbitrary odd dimensions, which is consistent with the superpotential via the BBC approach. Then the off-shell generalized ADT method is applied to evaluate the mass and angular momentum of the Gödel-type black holes by including the contribution from the gauge field. Finally, we strictly obey the rules of the original ADT formalism to incorporate the contribution from the gauge field within the potential. With the help of the modified potential, we try to seek for appropriate reference backgrounds to produce the mass and angular momentum. It is observed that the ADT formalism has to incorporate the contribution from the matter fields to yield physical charges for the Gödel-type black holes.

We present the exact solutions of one-dimensional Klein–Gordon and Dirac oscillators subject to the uniform electric field in the context of the new type of the extended uncertainty principle using the displacement operator method. The energy eigenvalues and eigenfunctions are determined for both cases. For the Klein–Gordon oscillator case, the wave functions are expressed in terms of the associated Laguerre polynomials and for the Dirac oscillator case, the wave functions are obtained in terms of the confluent Heun functions. The limiting cases are also studied using the special values of the physical parameters.