Modern Physics Letters A

The axion, originally postulated by Peccei and Quinn to solve the strong CP problem, has become of great interest in particle and astroparticle phenomenology. Yet it has a problem. It is widely assumed that the axion leaves the nonperturbative features of QCD unscathed. This is, however, not the case. On the contrary, the axion extension is found to be in conflict with seminal results on the low-energy properties of QCD. The key is that the anomalous coupling of the axion to the gauge bosons can be integrated out, leaving behind a path integral over topologically trivial gauge potentials.

In the framework of $f(R,T)=R+2\beta T$ gravity, wherein R denotes the Ricci scalar and T represents the trace of the energy–momentum tensor, the equilibrium structure of charged anisotropic white dwarfs is investigated. The stellar equations for the general scenario are derived, and numerical solutions are obtained for the Chandrasekhar equation of state alongside the charge density distribution proportional to the energy density, ${\rho }_{\mathrm{\text{ch}}}=\alpha \rho$. By scrutinizing the properties of the solutions under various parameter combinations, we conducted an exhaustive analysis of the influences of electric charge, modified gravity, and anisotropy on the structural characteristics of white dwarfs. Crucially, white dwarfs can transcend the trivial instances of General Relativity in various ways, thereby demonstrating super-Chandrasekhar phenomena. As an inquiry into the structure of white dwarfs, the findings of this research may contribute to elucidating astronomical observations such as superluminous type Ia supernovae.

The present work investigates the implications of incorporating noncommutativity into $f(R)$ gravity. In particular, we explore the proposed framework in a flat Friedmann–Robertson–Lamaître–Walker background. We introduced the noncommutativity between the coordinates and the momenta, in a $2n$-dimensional phase space. Applying the machinery of canonical quantization we obtain the noncommutative version of the Wheeler–DeWitt equation, and using a WKB-type approximation we can get analytical solutions for the model examining two cases for the leading noncommutative coefficient. In the first, solutions for the scale factor present a structure similar to previous solutions reported in the literature. The second one, in contrast to its commutative counterpart, the solutions obtained for the scale factor show that its evolution has the behavior of a non-singular cyclic universe. Also, we present the demeanor of the Hubble parameter and the effective equation of state parameter, where the latter crosses the “$-1$” divide line.

In this paper, we determine the radial and orbital states mass spectra of the triply heavy baryon ${\mathrm{\Omega }}_{bbc}$ with total spin $S=1∕2$ and 3/2 using the hypercentral constituent quark model (hCOM). The mass spectra are obtained by incorporating the color Coulomb plus linear confining term and the harmonic oscillator potential with first-order correction. Additionally, we considered spin–spin, spin-orbit and tensor interactions for hyperfine splitting calculation. Our computed mass spectra of the ${\mathrm{\Omega }}_{bbc}$ baryon is compared with existing literature. Further, we establish Regge trajectories of this baryon in ($n,M^2$) and ($J,M^2$) planes which are helpful in determining the unknown quantum number and $J^P$ values.

This research studies primarily centers around a specific vacuum solution of the Einstein’s field equations with a negative cosmological constant, known as a type-D vacuum solution in Anti-de Sitter (AdS) background. The key finding of this study is that the determinant of the Ricci tensor ($R_{\mu \nu }$) possesses a nonzero value. This observation ensures that this vacuum spacetime can be investigated within the framework of Ricci-inverse gravity as well. In fact, it has demonstrated that this type-D vacuum solution serves as an exact solution in Ricci inverse gravity in the background of AdS space. Notably, the negative cosmological constant undergoes modification by the coupling constant within this context. Moreover, we show that this gravity theory permits the formation of closed time-like curves at a specific moment in time analogue to the general relativity case. Consequently, this theory introduces an intriguing time-machine model within the domain of Ricci-inverse gravity theory.

In this paper, we propose a new analytical solution of the $\alpha$-decay process for the Killingbeck potential with the spherical Coulomb potential and determine the half-lives of some $\alpha$-emitters with atomic number $(Z)$ located in the region $60\le Z\le 92$ using the Wentzel–Kramers–Brillouin (WKB) approximation. The Killingbeck potential, with its complex form including harmonic and linear confinement terms, offers a greater richness of interaction and nuclear shape. We provide a solution to the problem of multiple turning points by showing that they can be reduced to two nonsymmetric points. Results obtained show relationships between the paramater of the nuclear potential and experimental data. Those results are compared with experimental data and other theoretical results from the literature. We find that our results are in very good agreement with the experimental data.

Electrohydrodynamic fluids possess extensive applications, spanning from the formation of magnetic fields in planets and stars to oil recovery. In this paper, a variational principle for an electrohydrodynamic fluid is presented, and formulated through the semi-inverse method. The Ritz method is utilized to derive an approximate solution. Furthermore, the potential application of this principle to optimal control problems constrained by an electrohydrodynamic fluid is explored.

We explore the application of fundamental solutions, constructed as irreducible linear combinations with variable coefficients of two Kummer confluent hypergeometric functions, to solve the one-dimensional stationary Schrödinger equation. This approach offers a new technique for tackling this equation, particularly well-suited for singular potentials exhibiting non-monotonic behavior, a challenge for traditional methods. We focus on a specific family of four-parameter potential wells defined on the positive semi-axis using the Lambert-W function. For these wells, the potential energy increases toward the origin but tends to zero at infinity. We present solutions in the form of linear combinations of Kummer functions and their derivatives, along with power functions and exponents. We then explore two specific well types within this family, analyzing the energy spectrum of the quantum system for each case.