International Journal of Modern Physics A

In this study, we have examined the evolving wormhole solution within Einstein-massive gravity, considering traceless, barotropic and anisotropic pressure fluids. We have conducted a comprehensive analysis of the constraints imposed by the constants derived from the wormhole solution. It is found that the wormhole throat, situated between two asymptotic universes, undergoes simultaneous expansion with acceleration. A detailed investigation of the energy conditions for traceless, barotropic, and anisotropic fluids suggests a wide range of possibilities for evolving wormhole configurations with nonexotic matter at the throat. The dependency of this feature on the various parameters arising from the study has also been examined.

In this paper, we propose a quaternion form of equations describing electromagnetic field in a homogeneous isotropic medium without dispersion. It is shown that by renormalizing the values of field inductions and sources, one can transform the asymmetrical Maxwell equations to a highly symmetric form. This provides a possibility to introduce the scalar and vector field potentials and represent the generalized equation for electromagnetic field in the form of a single second-order quaternionic wave equation. We demonstrate that this equation reduces to the system of ordinary hyperbolic wave equations for the field potentials and on the other hand, the same equation is equivalent to the system of Maxwell equations for renormalized field intensities. The symmetry of the renormalized Maxwell equations allows one to obtain the second-order relations for energy and momentum, as well as for Lorentz invariants of the renormalized fields, which formally have the same form as for the fields in a vacuum. In addition, the generalization of renormalized equations to the case of magnetic sources corresponding to the models of Dirac magnetic monopoles and Schwinger dyons is discussed.

A new exact time-dependent Kerr-like black hole solution is found on a Randall–Sundrum brane world spacetime. The solution is also valid on the Wick-rotated Euclidean counterpart space, so represents equally well a gravitational instanton, i.e. a bump in spacetime. Since the r-dependent part is determined by a first-order differential equation, one conjectures that the solution is a self-dual solution comparable with the Eguchi–Hanson solution. The zeroes and poles of the spacetime are determined by a quintic polynomial. To describe the Hawking particles, one uses the antipodal boundary condition on a complex Klein-bottle hypersurface ${ℂ}^1\times {ℂ}^1$. We used the Hopf fibration to get $S^2$ as the black hole horizon, where the centrix is not in a torus but in the Klein bottle. The twist fits very well with the antipodal identification of the point on the horizon. No “cut-and-paste” is necessary, so the Hawing particles remain pure without instantaneous information transport. A local observer passing the horizon will not notice a central singularity in suitable coordinates. The black hole paradoxes are also revisited in our new black hole model. A connection is made with the geometric quantization of ${ℂ}^1\times {ℂ}^1\sim S^3$, by considering the symplectic 2-form. The model can be easily extended to the non-vacuum situation by including a scalar field. Both the dilaton and the scalar field can be treated as quantum fields when approaching the Planck area.

There are two sets of orbits of the Virasoro group which admit a Kähler structure. We consider the construction of coherent states for the orbit $\widehat{\mathrm{\text{diff}}{S}^1}/U(1)$ which furnishes unitary representations of the group. The procedure is analogous to geometric quantization using a holomorphic polarization. We also give an explicit formula for the Kähler potential for this orbit and comment on normalization of the coherent states. We further explore some of the properties of these states, including the definition of symbols corresponding to operators and their star products. Some comments which touch upon the possibility of applying this to gravity in $(2+1)$ dimensions are also given.

We investigate a cosmological model using the covariant formalism proposed by Canuto et al., considering bosonic and fermionic fields as sources, including both self-interacting potentials. Following that path, it is possible to determine, first, a family of symmetries using the Noether procedure. That permits to obtain the conformal function $\beta (t)$, part of the covariant formalism, that maps the physics between descriptions. In gravitational units (old universe) it is verified that the bosonic/fermionic combination behaves as a dark constituent. In atomic units what emerges is an initially accelerated universe, followed a decelerated period, that would correspond to a primordial era considered as an analog of inflation.

The concept of a quantum structure underlying space has been proposed for quite some time, yet it has largely eluded direct observation. There is a prevailing notion that the minuscule effects stemming from quantum space could, under certain astronomical conditions, accumulate to an observable magnitude. Typically, these effects are perturbative, limited to the first one or two orders. This study presents a full dispersion law derived from a three-dimensional quantum space model. Our primary focus is to investigate the in-vacuo dispersion phenomenon and the threshold anomaly. Furthermore, we briefly explore the implications of additional spatial dimensions within this framework and suggest a way of distinguishing between various theories that agree in the leading-order approximation.

The $D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime }$ decay has been observed nonresonant as well as through ${\rho }_i$ resonances. The experimental values of its branching ratio are $<5.1\%$ for nonresonant process and $(5.6\pm 0.8)\%$ for nonresonant and resonance phases together, which are tabulated by Particle Data Group (PDG) collaboration. Recently, the BESIII collaboration has reported a measurement of the branching fraction for $D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime }$ decay with the value of $(6.15\pm 0.25\pm 0.18)\%$. In this work, we have presented an analysis of the branching fraction for this decay that has been calculated under the factorization approach. We have obtained the resonance and nonresonant amplitudes with annihilation corrections in our computation. Our result for the nonresonant branching ratio is $(5.02\pm 0.80)\%$, which is comparable to the experimental result of PDG collaboration. Considering the nonresonant and resonance contributions, the theoretical value of the branching ratio is $\mathcal{ℬ}(D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime })=(5.89\pm 0.95)\%$, which is in agreement with the reported experimental value.

In this paper, we extend a holographic construction for the entanglement negativity of two disjoint subsystems in the literature to ${\mathrm{\text{CFT}}}_d$s with a conserved charge dual to bulk ${\mathrm{\text{AdS}}}_{d+1}$ geometries. This involves an algebraic sum of the areas of bulk RT surfaces for certain appropriate combinations of subsystems. In this context, we compute the holographic entanglement negativity for two disjoint subsystems with long rectangular strip geometries in ${\mathrm{\text{CFT}}}_d$s dual to bulk RN-${\mathrm{\text{AdS}}}_{d+1}$ black holes in a perturbative framework. Our results at the leading order reproduce significant features observed earlier in the literature and conform to quantum information theory, which constitute strong substantiation of our construction.

High-fidelity beamline models typically involve particle-tracking and particle–matter interaction, which are intensive computationally demanding and time-consuming. This has led researchers to adopt data-driven surrogate models as an alternative to complex physics simulations. Training a data-driven model requires many labeled data, prompting researchers to simulate diverse beamline settings and obtain corresponding labels. However, the required dataset grows increasingly large as the number of adjustable parameters increases. Therefore, this study proposes a data-efficient surrogate modeling method that employs a student–teacher framework combined with active learning (AL) query strategies to minimize labeled samples while ensuring model accuracy. The proposed method is evaluated on the energy selection system (ESS) design of the Huazhong University of Science and Technology proton therapy facility (HUST-PTF). The results show that: (i) Training the surrogate model using 684 labeled samples selected via query strategy achieves a relative error below 5% for 90% of the samples in the test set. (ii) Compared to the beamline model built by Beam Delivery Simulation (BDSIM), the computational efficiency of the surrogate model is enhanced by a factor of $\mathcal{𝒪}(10^7)$.

Baryonic decays induced by $b\to s{l}^{+}{l}^{-}$ quark transition is an important area of interest nowadays to probe the sensitivities of new physics (NP). The exploration of the baryonic channels was prompted by the observation of ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\mu }^{+}{\mu }^{-}$ decays at the accelerators. Motivated by the recent experimental studies of baryonic decays, we have studied various polarization asymmetries for ${\mathrm{\Sigma }}_b$ baryon in the model beyond the standard model (SM). From the theoretical inspections of branching ratios for ${\mathrm{\Sigma }}_b\to \mathrm{\Sigma }{l}^{+}{l}^{-}$ channels in the SM indicate that these decays can be observed at the colliders. In this paper, we have studied the various $\mathrm{\Sigma }$ lepton polarization asymmetries within the whole allowed kinematic region for all three leptonic channels considering the effect of nonuniversal $Z^{\prime }$ boson. We expect that the obtained results for ${\mathrm{\Sigma }}_b$ decays will help the experimental groups investigate these decays at colliders and will probe NP with heavy baryons.