International Journal of Modern Physics A

Analyzing the phenomenon of deconfinement from a holographic point of view, it appears that the brane configuration in the bulk, corresponding to the confinement phase imposes a restriction on the strength of the holographic quantum error correction procedure. This restriction is partially removed when the transition to a deconfined phase occurs. The brane configurations corresponding to the bulk instantons are analyzed and it is shown that they cannot reach the region of the bulk that would ensure maximal error protection in the confinement phase, while keeping non-zero instanton size. In the deconfinement phase on the other side, we have a configuration that allows a higher degree of quantum error protection, still preventing the maximal protection allowed by the holographic principle. This suggests that the strength of quantum error correction codes in QCD systems is fundamentally limited both in confinement and deconfinement phases.

Spontaneous positron emission, caused by the supercritical Coulomb source with charge $Z$ and size $R$, is explored in essentially nonperturbative approach with emphasis on the VP-energy ${{ℰ}}_{\mathrm{\text{VP}}}$, considered as a function of the Coulomb source parameters $Z$ and $R$. The specific contribution to ${{ℰ}}_{\mathrm{\text{VP}}}$, which appears in the supercritical case due to direct Coulomb interaction between VP-charge densities ${\varrho }_{\mathrm{\text{VP}}}(r)$, is outlined and studied in detail. It is shown that after first levels diving into the lower continuum, this contribution to ${{ℰ}}_{\mathrm{\text{VP}}}$, being properly renormalized, turns out to be negative in contrast to the classical electrostatics and so could play an important role in spontaneous emission, especially for $Z$ just above the first $Z_{\mathrm{\text{cr}},1}$. The additional problems of spontaneous emission, caused by the lepton number conservation, are also discussed.

There is a formulation of unimodular gravity (UG) in which the unimodular metric is obtained out of an unrestricted one as ${\gamma }_{\mu \nu }=|g{|}^{-\frac{1}{n}}{g}_{\mu \nu }$. This unrestricted metric is only defined up to a Weyl rescaling. Physical charges like ADM energy or horizon entropy, however, are not Weyl invariant in general. In this paper a Weyl invariant definition of some physical charges is given.

In this work, we use the approach recently introduced by Barros to study hadron spectra and some quark confinement properties in a Schwarzchild-like space–time generated by a nongravitational field. As a starting point, for the nongravitational field, we make the choice of a strong Yukawa-like field whose associated potential is a generalized Yukawa-like potential, typical of strong interactions. Then, from the latter field, the energy momentum tensor is constructed, the Einstein field equations are solved and the curvature function of the Schwarzchild metric is obtained. The correspondence principle applied to the Schwarzchild metric has enable us to construct the Dirac equation in the latter space. The resolution of the coupled differential equations of Dirac made it possible to obtain the energy spectrum of the strong interaction. The latter is obtained in a more general form than in the previous investigations. Then, the energy spectrum, masses and confinement radius of few hadrons are estimated and compared with experimental data and other theoretical studies. In most considered cases, our predictions are found to be in good agreement with experimental data. The good agreement observed between our outcomes and the experiment can be attributed to the choice of our potential, which has more free parameters than in past studies with the same approach.

This paper is in the spirit of our work on the consequences of the Regge calculus, where some edge length scale arises as an optimal initial point of the perturbative expansion after functional integration over connection. Now consider the perturbative expansion itself. To obtain an algorithmizable diagram technique, we consider the simplest periodic simplicial structure with a frozen part of the variables (“hypercubic”). After functional integration over connection, the system is described by the metric $g_{\lambda \mu }$ at the sites. We parameterize $g_{\lambda \mu }$ so that the functional measure becomes Lebesgue. The discrete diagrams are free from ultraviolet divergences and reproduce (for ordinary, non-Planck external momenta) those continuum counterparts that are finite. We give the parametrization of $g_{\lambda \mu }$ up to terms, providing, in particular, additional three-graviton and two-graviton-two-matter vertices, which can give additional one-loop corrections to the Newtonian potential. The edge length scale is $\sim \sqrt{\eta }$, where $\eta$ defines the free factor ${(-det\parallel g_{\lambda \mu }\parallel )}^{\eta ∕2}$ in the measure and should be a large parameter to ensure the true action after integration over connection. We verify the important fact that the perturbative expansion does not contain increasing powers of $\eta$ if its initial point is chosen close enough to the maximum point of the measure, thus justifying this choice. Discrete propagators depend on the Barbero–Immirzi parameter $\gamma$, which determines the ratio of timelike and spacelike elementary length scales. The existing estimates of $\gamma$ allow the propagator poles to have real energy for any (real) spatial momenta.

In direct dark matter (DM) detection via scattering off the electrons, the momentum transfer plays a crucial role. Previous work showed that for self-interacting DM, if the DM particle has a size (the so-called puffy DM), the radius effect could dominate the momentum transfer and become another source of velocity dependence for self-scattering cross-section. In this work, we investigate the direct detection of puffy DM particles with different radii through electron recoil. We find that comparing with the available experimental exclusion limits dominated by the mediator effect for XENON10, XENON100 and XENON1T, the constraints on the puffy DM-electron scattering cross-section become much weaker for large radius DM particles. For small-radius DM particles, the constraints remain similar to the point-like DM case.

Accelerator engineering could benefit from faster and higher-quality physics simulations. Machine learning has emerged as a promising tool for developing accelerator simulation programs that are both fast and accurate. In this study, we propose a surrogate model based on encoder–decoder neural networks. We incorporate physical regularization into the loss function, which allows us to integrate prior physical knowledge into the deep learning network. The advantage of this regularization is that it ensures the results are more consistent with the underlying physical laws. The method was applied to beam dynamics modeling of the medium energy beam transport (MEBT) section in the China Accelerator Facility for Superheavy Elements (CAFe II). The final results indicate that after training, the network maintains a mismatch, emittance difference, and transmission efficiency of approximately 0.01. Our scheme has been demonstrated to be effective in the simulation of the accelerator’s beam dynamics.

In this paper, we report on generalized half-dyon solutions in SU(2) Yang–Mills–Higgs theory, namely Type I and Type II solutions. These solutions are constructed by considering $\varphi$-winding number $1\le n\le 4$, electric charge parameter $0\le \eta <{\eta }_{\mathrm{\text{max}}}$ and Higgs self-coupling constant $0\le \beta \le 1$. They represent system of magnetic charge $+2n\pi /g$ ($-2n\pi /g$) and electric charge $Q$ that lies along the negative (positive) $z$-axis. Fundamental properties, such as total energy, electric charge, dipole moment, are explored and discussed.

Studies of scattering amplitudes for electric and magnetic charges have identified previously overlooked multiparticle representations of the Poincaré group in four dimensions. Such representations associate nontrivial quantum numbers (known as pairwise helicities) with asymptotically separated pairs of particles, and thus cannot be described as tensor products of one-particle states. We extend this construction to sources and spacetimes of higher dimension. We first establish the dynamical origin of pairwise helicity in $p$-form electrodynamics coupled to mutually nonlocal branes. We then interpret this pairwise helicity as a quantum number under an SO(2) pairwise little group associated with pairs of distinct branes. We further characterize the “higher” little groups that could in principle be used to induce multiparticle or multi-brane representations of the Lorentz group.