International Journal of Modern Physics A

Production of exotic states at LHC is considered in the large radius compactification (LRC) scenario. We envisage a five-dimensional theory for a scalar field in five-dimensional flat space–time. It is compactified on a circle, $S^1$, with radius, $R$. The radius is assumed to be in TeV scale appealing to LRC hypothesis. The production of Kaluza–Klein states whose masses lie in the vicinity of TeV range is considered. Instead of appealing to any specific model, bounds on inelastic cross-sections and near forward differential cross-section are derived from the Lehmann–Symanzik–Zimmermann (LSZ) formulation. We consider decompactified theory if the compactification radius is large enough to unravel the fifth spatial dimension in LHC energy scale. Bounds on cross-sections are also derived for this scenario. We present bounds on inclusive cross-sections for reactions like $a+b\to c+X$, $X$ being unobserved states. We plot the bounds as a function of energy and propose that these bounds might be useful for search of exotic states in LHC experiments like ATLAS and CMS.

Making use of a model of nonlinear electrodynamics (NED), whose action remains invariant under conformal transformations, a new class of charged higher-dimensional black holes (BHs) has been introduced in the massive gravity theory. Our exact solutions, with A(dS) asymptotic behavior, in addition to the BHs with one, two and three horizons, show the extreme and horizon-less ones. The conserved and thermodynamic quantities have been calculated in the presence of massive gravitons and NED. By use of a Smarr mass formula, it has been found that the standard form of the first law of BH thermodynamics (FLT) remains valid for our new massive BHs. Thermal stability of the BHs has been studied comparatively, by use of the geometrical and thermodynamical methods. The size of those BHs which undergo first- or second-order phase transition, as well as those of which are locally stable has been determined. The results of geometrical and thermodynamical approaches have been compared, for bout of dS and AdS cases, by use of the plots. It has been shown that both of the aforementioned methods produce the same results provided that HPEM or Quevedo type-two (QII) metrics are used. Critical behavior of the BHs has been studied by taking thermodynamic pressure proportional to the cosmological constant. It has been found that in addition to the Van der Waals (VdW) like phase transition, the so-called reentrant phase transition (RPT) can occur as well.

This work deals with Einstein–æther scalar–tensor gravity in the background of homogeneous and isotropic flat FLRW space–time model. The Noether symmetry vector identifies a transformation in the augmented space so that the field equations become solvable. The cosmological solutions are analyzed from the observational point of view. Finally, for quantum cosmology, the Wheeler–DeWitt (WD) equation has been formulated and solutions have been determined by identifying the periodic nature of the wave function using conserved (Noether) charge.

Using the ambitwistor string theory, we study graviton scattering amplitudes in a light-like linear dilaton background of 10-dimensional supergravity. At the tree level, we find that the three-graviton amplitude coincides with the type-II superstring theory, and the four-graviton or more amplitudes differ from the superstring theory but satisfy the scattering equations. Due to a modified momentum conservation law different at each order in genus expansion, a nonzero amplitude is determined solely from the particular order in perturbation theory without further corrections.

We investigate the impact of the incorporation of minimum measurable length on accretion onto Schwarzschild black hole within the asymptotically safe ambiance. The Schwarzschild black hole is modified by the minimum measurable length associated with the generalized uncertainty principle (GUP), enabling it to accept the quantum gravity correction. We look at potential critical point locations and calculate the critical speed of the matter accreting. We determine the temperature and total integrated flux correction at the event horizon for the polytropic matter using the least measurable length conjecture offered by the GUP. We note that the incorporation of minimum measurable length has a significant impact on the accretion process. Furthermore, the quantum gravity regime associated with modification maintains an asymptotically safe ambiance.

In this paper, tunneling of fermions from rotating BTZ black hole is investigated using modified dispersion relation (MDR) and Rarita–Schwinger equation. The effect of MDR on the tunneling of fermions raises the Hawking temperature of rotating BTZ black hole. It is observed that the modified Hawking temperature of the black hole depends not only on the radial parameters of the black hole but also on the angular parameters of the black hole and the coupling constant $\sigma$. Further, the entropy and the heat capacity of the black hole are also studied.

We consider one-dimensional Dirac equation with rationally extended scalar potentials corresponding to the radial oscillator, the trigonometric Scarf and the hyperbolic Pöschl–Teller potentials and obtain their solution in terms of exceptional orthogonal polynomials. Further, in the case of the trigonometric Scarf and the hyperbolic Pöschl–Teller cases, a new family of Dirac scalar potentials is generated using the idea of parametric symmetry and their solutions are obtained in terms of conventional as well as exceptional orthogonal polynomials.

We review the Noether symmetry analysis for the Chameleon cosmology presented in R. Bhaumik, S. Dutta and S. Chakraborty, Int. J. Mod. Phys. A 37, 2250018 (2022). We show that the classification problem for the field equations in Chameleon cosmology is still open.