International Journal of Modern Physics A

By expanding in powers of the inverse multipole number, we derive compact analytic expressions for the quasinormal modes of scalar and electromagnetic perturbations around regular Simpson–Visser black holes. These analytic formulas offer sufficient accuracy for the first and higher multipoles, except when the black hole is in a near-extremal state. The correspondence between null geodesics and high-frequency quasinormal modes is confirmed for the case under consideration. As an application, we show that Simpson–Visser black holes respect the Hod’s bound on the damping rate of the fundamental quasinormal mode.

The recently reported astrophysical neutrinos events in the TeV-PeV energy range open a winder to explore new physics at energy frontiers. In this paper, we examine effects of nonstandard interactions (NSIs) on the PeV neutrinos events. We consider NSIs with and without a gauge symmetry $L_{\alpha }-L_{\beta }$. We find that, for typical ${\mu }^{\pm }$ damping and ${\pi }^{\pm }$ decay sources, the NSI with an extra gauge symmetry has more noticeable effects on the PeV events. Therefore, the detection of the events in the upcoming experiments could set stringent constraints on the NSI parameters in the $L_{\alpha }-L_{\beta }$ symmetric case.

In this paper, we show that the dynamics encoded in the nonlinear realization of the semi-direct product of the very extended algebra $K_{27}$ with its vector representation contains the low-energy effective action of the closed bosonic string.

The Lagrangian formalism is used to derive covariant equations that are suitable for use in continuously distributed matter in curved spacetime. Special attention is given to theoretical representation, in which the Lagrangian and its derivatives are directly involved. The obtained results, including equations for metric, equations of motion, and equations for fields, are applied to purely vector fields. As a consequence, formulas are determined for calculating the basic quantities necessary to describe physical systems. In this case, not only the pressure field and acceleration field are taken into account, but also the electromagnetic and gravitational fields outside the matter, which contribute to the four-momentum and to the four-dimensional angular momentum pseudotensor of each system. Each of the presented fields, including the gravitational field, has its own four-potential and its own tensor, which allows all calculations to be performed in a covariant way. In particular, when applying the principle of least action, the optimal approach is one in which the four-currents, field four-potentials and metric tensor depend on the observation point and vary independently from each other. In addition to the Euler–Lagrange equation, another equation of motion is derived containing the density of generalized four-force and the time derivative of the volume density of the generalized four-momentum. In order to uniquely calibrate the energy, which is a scalar quantity, the cosmological constant included in the Lagrangian is used. This leads to the fact that both the scalar curvature and the cosmological constant disappear in expression for the four-momentum of the system. In addition, the equation for the metric is simplified. The peculiarity of the equation for the metric is that the total stress-energy tensor of the physical system, presented in the right part of the equation for the metric, is associated only with field tensors and does not depend on particle four-velocities. Moreover, the trace of stress-energy tensor is zero. To calculate the stress-energy tensor, the functional derivative of Lagrangian density with respect to the metric tensor is used. The covariant derivative of stress-energy tensor leads to the equation of particle motion under the action of fields, and to the generalized Poynting theorem. The contractions of the field tensors with the Ricci tensor are equal to zero, so that each field makes its own contribution to the curvature of spacetime in the system. The inertial mass of a system is defined as the value connecting the four-momentum and four-velocity of the center of momentum of the system, and can be calculated using the square of the four-momentum. It is shown that the canonical representation of the angular momentum pseudotensor is its representation with covariant indices. The radius-vector of the center of momentum of a physical system is determined in covariant form.

We give a Hamiltonian formulation of the new model of $\mathcal{𝒩}=8$ supersymmetric mechanics recently proposed by S. Fedoruk and E. Ivanov and show that it possesses the dynamical $\mathcal{𝒩}=8$ superconformal symmetry $\mathrm{\text{osp}}(8|2)$. The bosonic part of the Hamiltonian is just a free particle on eight-dimensional cone embedded in nine-dimensional pseudo-Euclidean space, while the fermionic part can be interpreted as a spin–orbit interaction term.

A Ramond open superstring quantization is studied in a flat D-dimensional Minkowski spacetime in a static gauge. This gauge degenerates the boost generators. A deformation in the structure of the boosts is proposed at the classical level with some energy-dependent coefficients. We quantize the theory and propose the quantum version of the deformation of the boost operators. The energy-dependent coefficients are determined in the first and second excited levels in order to keep the physical Hilbert space Lorentz invariant. The critical space–time dimension $D=10$ and ordering ambiguity constant $a=0$ are recovered. We give the connection between the covariant and static gauge quantizations.

In this paper, we study (0,2) two-dimensional theories in type IIB configurations with D5 branes wrapping blow-up $P^1$ cycles of deformed resolutions for $A_n$ singularities or in T-dual IIA configurations with suspended D4 branes. We consider deformations of four-dimensional $\mathcal{𝒩}=2$, ${\prod }_{i=1}^{n}U(N_i)$ theories with general superpotentials for the adjoint and bifundamental fields together with fundamental flavors and reduce to two dimensions on a two-torus in the presence of magnetic fluxes and FI terms.

This study investigates Beam Line Absorbers (BLAs) for the Hefei Advanced Light Facility (HALF). A ferrite-based BLA prototype was developed, demonstrating high-power handling capacity up to 10kW, ultra-high vacuum performance better than $6.5\times 10^{-10}$ mbar, and high absorption efficiency in critical frequency ranges. Subsequently, more compact designs with reduced longitudinal length were explored, investigating ferrite-only, silicon carbide (SiC)-only, and hybrid configurations through RF simulations. Based on preferred absorption efficiency, ferrite-only and hybrid BLA structures were further analyzed under high-power conditions. Referencing test results, multiphysics simulations were conducted under 3kW absorbed power. The hybrid design, comprising two rings of ferrite tiles and one ring of SiC tiles, improved the temperature distribution of the absorbing materials. Extrapolating to 11kW absorbed power, this design reduced the maximum temperatures on absorbing tiles by up to 40$°$C compared to the ferrite-only design. The hybrid design offers a balanced solution that combines effective HOM damping with enhanced thermal performance, improving the long-term operational stability of BLAs.