Modern Physics Letters A

Quantum computing as emerging technology raises high expectations to accelerate complicated calculations, superseding capabilities of presently available supercomputers and to provide a solution to the ever-increasing challenge of processing big amount of data. Besides theoretical promises, quantum computers have successfully been realized in experimental settings during the past few years, and can now also be accessed commercially. Given this availability of quantum computers, their application potential can be scrutinized. Promised to lead to disruptive changes in addressing and solving problems from the domains of simulation, optimization and machine learning, quantum computers have been researched in context of many application scenarios in industrial and academic setting in the recent years. However, it turns out that currently available quantum computers are still to small in size and limited in quality to fulfill the high hopes set in them at the moment. This review reflects on the current state of the technology coming from the perspective of the application, and indicates the developments required on hardware, software and algorithmic side to eventually make quantum computing beneficial for applications.

This paper studies the motion of charged test particle, moving in the outermost layer of a heterogeneous body (taken as first primary) filled with incompressible homogeneous viscous fluid and second primary is taken as point mass, whereas both the primaries are assumed to be charged. We compute the equations of motion of test particle (the third body) and stationary points (circular, axial and out-of-plane stationary points). And also, the stability of stationary points is examined utilizing characteristics equations and Routh–Hurwitz criterion. In addition to this, the numerical analysis of stationary points and their stability are worked out for different values of parameters.

In this paper, we investigate hypergeometric stringy corrections in the swampland program for rescaled gravity. Precisely, we study inflationary models from Gauss–Bonnet hypergeometric scalar couplings via the falsification scenario. We first derive generalized exponential potentials from such hypergeometric behaviors. Then, we examine certain selected scalar potentials by computing the relevant cosmological quantities using the slow-roll mechanism. Choosing specific points in the corresponding moduli space, we provide viable findings corroborated by Planck observational data and checked by the swampland criteria.

The common opinion that the Lorentz transformation distorts the Minkowski spacetime arises from a mathematically incorrect neglect of its non-diagonal terms. When the non-diagonal Lorentz transformation is properly treated, the time dilation and the space distortion disappear. Consequently, the Lorentz metric produced by the Lorentz transformation is identical to the Minkowski metric. The spacetime distortion in moving inertial frames is properly described by the so-called Doppler metric produced by the Doppler transformation. This transformation assumes the existence of a preferred frame and depicts the Doppler shift of light for a moving light source and/or observer. The Doppler metric is Lorentz invariant and leaves the Maxwell’s equations unchanged from their form in the Minkowski spacetime. Moreover, the Doppler metric is experimentally confirmed because it yields the null result in the Michelson–Morley experiment and other interferometric experiments. The suitability of the Doppler metric for describing light properties in Special and General Relativity is supported by recent cosmological observations of the cosmic microwave background.

Inspired by high-energy physics and by considering standard gravity theory as the low-energy limit of quantum theory, the modification of general relativity as $R+f(G)$ has been proposed. This paper is dedicated to investigating the cosmological model of modified Gauss–Bonnet gravity in four dimensions. General field equations for the four-dimensional Friedmann– Robertson–Walker metric are given in detail. Also, it is well known that Hubble parameter $H(z)$ measurements are helpful for the inference of cosmological model parameters. We try to explain the MCMC statistical approach used to calculate Hubble’s parameter. The resulting form of $H(z)$ was limited using Cosmic Chronometric data, Standard Candles SN Ia from Pantheon, and Baryon Acoustic Oscillations to obtain the best match values by using the regression equation. Finally, to examine the late-time dynamics of our Universe, the behavior of physical and kinematic variables like the deceleration parameter $(q)$, State-finder parameters $\{r,s\}$, diagnostic parameter ($O_m(z)$), equation of state parameter as well as the behavior of energy conditions versus redshift with the parameter values are presented.

In [Phys. Rev. D 107, 104008 (2023)], we reported a novel exact closed-form solution which describes asymptotically flat spacetimes in pure ${{ℛ}}^2$ gravity. The solution is Ricci scalar flat, viz. ${ℛ}\equiv 0$ everywhere. Whereas any metric with a null Ricci scalar would trivially satisfy the ${{ℛ}}^2$ vacuo field equation, ${ℛ}({{ℛ}}_{\mu \nu }-\frac{1}{4}{g}_{\mu \nu }{ℛ})+g_{\mu \nu }\square {ℛ}-{\nabla }_{\mu }{\nabla }_{\nu }{ℛ}=0$, in this paper, we shall show that our solution satisfies a “stronger” version of the ${{ℛ}}^2$ vacuo field equation, viz. ${{ℛ}}_{\mu \nu }-\frac{1}{4}{g}_{\mu \nu }{ℛ}+{{ℛ}}^{-1}(g_{\mu \nu }\square {ℛ}-{\nabla }_{\mu }{\nabla }_{\nu }{ℛ})=0$, despite the term ${{ℛ}}^{-1}$ being singular. Even though ${ℛ}$ identically vanishes, for our solution, the combinations ${{ℛ}}^{-1}{\nabla }_{\mu }{\nabla }_{\nu }{ℛ}$ and ${{ℛ}}^{-1}\square {ℛ}$ are free of singularity. This exceptional property sets our solution apart from the set of null-Ricci-scalar metrics and makes it a genuinely nontrivial solution. We further demonstrate that, as a member of a larger class of asymptotically de Sitter metrics, our solution is resilient against perturbations in the scalar curvature at largest distances, making it relevant for physical situations where the background deviates from asymptotic flatness.

In this paper, we utilize the effective Lagrangian method within the tree-level Born approximation to explore $\varphi$-meson photoproduction, i.e. $\gamma p\to \varphi p$. Our analysis encompasses contributions from various sources, including the Pomeron, $f_1$-Regge, pseudoscalar particles ($\pi$, $\eta$), scalar particles ($a_0$, $f_0$), protons, and three-nucleon resonance states. In addition, we consider a possible pentaquark-like $K^{\ast }\mathrm{\Sigma }$-bound state $P_s$. The findings indicate that, apart from the region near the threshold, contributions other than the Pomeron generally have a limited impact on the total cross-section. However, alternative contributions become crucial at specific angles, particularly at smaller values of $cos\theta$. The incorporation of $P_s$ and other nucleon resonances proves essential to elucidate the bump observed near $W\sim 2.15$GeV at very forward angles and behaviors within the range of $W=(2.0-2.3)$GeV. Furthermore, in the region with $W\ge 2.5$GeV, where nucleon resonances become negligible, contributions from the t-channel mesons become pivotal. Our calculations for spin density matrix components, examined in various frames, exhibit improvement when considering all contributions. This comprehensive approach successfully reproduces the observed bump by including $P_s$. We also briefly estimate the $P_s$ production via $\varphi$-meson photoproduction in the future Electron-Ion Collider (EIC), resulting in the luminosity of 10 fb${}^{-1}$ per month.

In this paper, we examine certain aspects of magnetized spacetime solutions within the Einstein–Maxwell–dilaton theory. Specifically, we discuss the Melvin-like universe and compare it to the equivalent solution in the Einstein–Maxwell case. Additionally, we analyze the equatorial circular motions and corresponding electromagnetic fields within this spacetime. Some distinguished properties compared to the magnetized black hole in Einstein–Maxwell case are found.

In this paper, we reconsider the concept of bulk viscosity in Brans–Dicke theory to study accelerated expansion of the universe in a flat Friedmann–Robertson–Walker metric. In recent works on bulk viscosity in Brans–Dicke theory, the power-law form of Brans–Dicke scalar field has been taken to explain recent phase transition of the universe, however, power-law form confronts constant deceleration parameter problem. Therefore, we consider recently proposed well-motivated logarithmic form of Brans–Dicke scalar field to discuss bulk viscous model in Brans–Dicke theory. We obtain the values of deceleration parameter and equation of state parameter for the model, and plot their graphs against the redshift parameter z. The plots show that the model is able to explain the recent phase transition of the universe and equation of state parameter shows the behavior of dark energy. Further, we apply two important analysis, namely, $w-w^{\prime }$ analysis and thermodynamic analysis to examine our model. The $w-w^{\prime }$ analysis shows that our model belong to thawing region and shows similarities with quintessence model. All the trajectories start from the point $w^{\prime }=0$ with different negative values of w having quintessence behavior. The thermodynamic analysis shows that the model satisfies generalized second law of thermodynamics.

We show that the first several overtones could be calculated by the time-domain integration method for asymptotically de Sitter black holes already at the lowest multipole numbers of gravitational and electromagnetic perturbations. This is not possible for asymptotically flat black holes, for which extraction of frequencies with the Prony method is usually possible with reasonable accuracy only for the fundamental mode. The reason for much better efficiency in the de Sitter case is the absence of power-law tails: the quasinormal modes dominate the signal not only at the intermediate stage, but also at asymptotically late times.