International Journal of Modern Physics a最新文献

In chiral Einstein–Cartan gravity, a new gauge fixing procedure is implemented recently, leading to a very economical perturbation expansion of the action. Using this formulation and the relevant gauge fixing, we develop the ghost Lagrangian on an arbitrary Einstein background using the Becchi-Rouet-Stora-Tyutin (BRST) formalism. The novelty is the appearance of a new term quadratic in the tetrad field. We next compute the heat kernel coefficients and understand the divergences arising in the gravitational one-loop effective action. In our computation, the arising heat kernel coefficients depend only on the self-dual part of the Weyl curvature. We make a comparison between our results and what has been obtained for metric general relativity.

This study focuses on the cosmological evolution of Barrow holographic dark energy (BHDE) in a flat FLRW-universe. We take into account a time-dependent scale factor $a(t)={[sinh(kt)]}^{\frac{1}{n}}$, where k and n are positive values, to find the solutions to field equations. This scale factor results in a smooth transition of the universe from its previous decelerating stage to its most recent accelerating stage. Using the Granda–Oliveros cut-off, we examine the chronology of the deceleration parameter, equation of state parameter, and density parameter, and we analyze the positive aspects of the BHDE model. Negative pressure values in this model suggest dark energy dominance, resulting in the universe’s acceleration. We use the statefinder parameters ($r,s$) to improve the accuracy of the results of the dark energy model that is similar to the $\mathrm{\Lambda }$-CDM model.

In this paper, we study the dominant nonuniversal contributions to muon decay for the five scalar leptoquarks (LQs) allowed by the Standard Model gauge symmetries. By using a common computational framework, we isolate the New-Physics (NP) one-loop corrections over the observable $\mathrm{\Delta }r$ and explore the connection with the W boson mass. We highlight the role of nonuniversal terms considering, for the $\mathrm{\text{SU}}(2)$ doublet and triplet LQs, a completely degenerate scenario, thus cancelling/moderating the effects of the oblique parameters S, T and U. We determine simple formulas that exhibit the leading nonuniversal behavior generated by the introduction of extra Yukawa terms and confront them against a present tension in $M_W$ and the projected FCC-ee accuracy.

In Quantum Field Theory (QFT), scattering amplitudes are computed from propagators which, for internal lines, are built upon spin/polarization-sum relationships. In turn, these are normally constructed upon plane-wave solutions of the free field equations. A question that may now arise is whether such spin/polarization-sums can be generalized. In the past, there has been a first attempt at generalizing spin sums for fermionic fields in terms of the Michel–Wightman identities. In this paper, we aim to find the most general spin sums for fermionic fields within the range of QFT.

We extend our recent works [Int. J. Mod. Phys. A 38, 2350069 (2023)] and obtain one-parameter $(\lambda )$ family of rationally extended Dirac–Lorentz scalar potentials with their explicit solutions in terms of $X_m$ exceptional orthogonal polynomials. We further show that as the parameter $\lambda \to 0$ or $-1$, we get the corresponding rationally extended Pursey and the rationally extended Abraham–Moses-type of scalar potentials, respectively, which have one bound state less than the starting scalar potentials.

In this work, we consider two modified Chevallier–Polarski–Linder (CPL) models in the background of homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) space–time, namely, (i) the generalized CPL model (Model I) and (ii) the logarithmic form of the equation of state for the dark energy. From the observational data sets $((\text{Pantheon}+)+\text{BAO}+\text{HST})$, we find that at the present epoch (redshift $z=0$), the equation of state for the dark energy converges almost at the same value ${\omega }_{\mathrm{\text{fld}}}\approx -0.86$ and the variation of ${\omega }_{\mathrm{\text{fld}}}(z)$ with respect to the redshift parameter is very small for both models. We also find that the present value of the Hubble parameter $H_0$ is almost same for both the models. Finally, we compare the models in the light of Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Bayesian evidence. However, we find that Model II is better compared to Model I from the estimated value of the deceleration parameter.

Axion Dark Matter (DM) is studied on the formation of SuperMassive Black Holes (SMBH) at high red shift z. It is shown that the attractive self-interaction of this DM may resolve the tension between the large mass with high angular momentum of SMBH and its early time formation. We consider the ultra-light axion DM around $O(10^{-21})$ eV as its origin, which may also cause nano-Hz stochastic gravitational wave background recently observed.

We find the nonextremal charged rotating charged black holes in quadratic $f(T)$ gravity are holographically dual to two different hidden conformal field theories. The two conformal field theories can be merged to find a very general hidden conformal field theory, which is generated by the $SL(2,\mathbb{Z})$ modular group. We also carry out the calculation to the extremal limit of the black holes, and find the corresponding dual quantities. Contrary to the existence of two different dual conformal field theories for the extremal charged rotating black holes in Einstein gravity, we find only one dual theory exists for the extremal charged rotating black holes in quadratic $f(T)$ gravity.

Orbital abscesses are primarily seen in children as complication of ethmoid bacterial sinusitis. We report a case of invasive aspergillosis causing orbital abscess in an immunocompetent child which resolved with surgery followed by antifungal therapy. This case highlights need for histopathological, and microbiological examination, including fungal culture in such cases.