We investigate the quasinormal modes (QNMs) and greybody factors of dilaton-Euler-Heisenberg (dEH) de Sitter (dS) black holes in string-inspired Euler-Heisenberg gravity. Since the axial gravitational and electromagnetic perturbations decouple, we treat them independently. By applying the asymptotic iteration method (AIM) alongside a sixth-order WKB approximation, we compute the quasinormal frequencies and find excellent agreement between the two approaches. We also find that the QNM spectra depend sensitively on the magnetic charge Q_m, cosmological constant Λ, and nonlinear coupling ε, with a notable topological anomaly appearing in the electromagnetic frequency trajectories. Additionally, larger values of Q_m or the multipole number l generally suppress wave transmission, while the electromagnetic sector with ε=1 exhibits an anomalous response.
Abstract Anisotropic cosmologies in modified gravity are useful only when exact solvability is accompanied by isotropization, viable matter properties, and an acceptable mean expansion history. We examine these requirements for Bianchi type-V cosmology in $f(T)$ gravity with a comoving perfect-fluid source. Within the pure-tetrad formulation, the field equations select a linear torsion sector yielding three exact power-law solution classes. We also derive the covariant tetrad-spin-connection equations, including the off-diagonal constraints. The $n>0$, $n\neq3$ anisotropic family satisfies the covariant compatibility conditions in the linear, GR-equivalent sector, while the $n=0$ ansatz admits an isotropically expanding solution with $K=0$ and unrestricted $l>0$. In the nonlinear isotropic sector, we reconstruct $f(T)$ parametrically for general $n$ and obtain an explicit nonlinear function for $n=1$, without assuming its functional form. For the three pure-tetrad classes, we analyze the directional Hubble rates, mean expansion, shear, normalized anisotropy, deceleration and jerk parameters, reconstructed density, pressure, equation of state, and energy conditions. Interestingly, only the first class approaches an isotropic matter-like regime, with decaying shear and normalized anisotropy and a mean expansion approaching matter-era behavior. Comparison with 33 cosmic-chronometer measurements shows that this class reproduces the qualitative increase of $H(z)$ with redshift, but its law $H(z)=H_0(1+z)^{3/2}$ is too rigid for the late-time expansion history; the fixed-$\Omega_m$ flat $\Lambda$CDM model provides a better fit. Moreover, the reconstructed matter sector admits positive-density regions satisfying the null and dominant energy conditions, while the strong energy condition is violated for the representative positive-coupling choice. The remaining classes expand too slowly and retain finite normalized anisotropy. In the isotropic Bianchi type-V limit, we further obtain an exact parametric reconstruction of nonlinear $f(T)$ models, including an explicit functional form in the $n=1$ branch.
Abstract The Extended Quantum Diffusion Approach (EQDA), incorporating coordinate-dependent friction, is applied to a systematic study of capture cross sections for various projectile-target combinations involving the actinide nuclei ($^{238}$U, $^{244}$Pu, and $^{248}$Cm). For reactions with positive $Q_{2n}$ values, the two-neutron transfer is assumed to occur before capture, leading to an effective post-transfer entrance channel with modified nuclear properties and quadrupole deformations. The calculated excitation functions describe the available experimental data reasonably well down to deep sub-barrier energies, reaching about 15 MeV below the spherical Coulomb barrier. The systematic analysis shows that the sub-barrier slopes of excitation functions are governed by an interplay between nuclear deformation and the dissipative entrance-channel dynamics. The comparison of the initial and effective post-transfer channels illustrates the influence of the adopted effective-channel prescription, including the change in the projectile deformation description, while the comparison with constant friction demonstrates the role of coordinate-dependent dissipation in the deep sub-barrier region.
Abstract We investigate the rare inclusive decay B → X s l + l - within the framework of the μ from ν Supersymmetric Standard Model (μνSSM), focusing on the origin and phenomenological implications of new-physics effects induced by the extended fermion and scalar sectors of the model. We systematically analyze the parameter dependence of the relevant Wilson coefficients and identify the dominant particle sectors responsible for these corrections. Under the experimental constraints from bar{B} → X s γ, B s 0 → μ + μ - , and the SM-like Higgs boson mass around 125 GeV, we explore the resulting modifications to the branching ratios and forward-backward asymmetries in both low- and high-q 2 regions. Furthermore, through a systematic decomposition of the interference contributions governing the forward-backward asymmetry, we demonstrate that the C 7 C 10 and C 9 C 10 interference terms dominate its phenomenological behavior in both kinematic regions. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.
Abstract We investigate the finite-duration generation of hypermagnetic seeds by vortical plasma motion associated with a high-scale first-order phase transition. Starting from a vanishing initial hypermagnetic field, the source is described by an effective parity-odd vortical electromotive response within a reduced battery diffusion framework. Transition localized Gaussian sources are used to quantify how the seed depends on the inverse transition duration parameter (β/H∗), while broad coherent sources provide an upper envelope comparison within the reduced source closure. In the perturbative coherent regime, the generated hypermagnetic energy and helicity depend quadratically on the vortical response amplitude, with the helicity sign determined by the kinetic helicity of the source. For 100≤β/H∗≤1000, the localized-source energy and helicity decrease approximately as (β/H∗)^ -3 and remain several orders of magnitude below the broad coherent reference. An unequal time analysis further shows that temporal coherence controls the seed normalization in addition to the source duration. Subsequent spectral evolution is analyzed separately from seed generation. In the ideal limit, the source-free nonlinear transfer shows only a weak direct transfer tendency, whereas, for the adopted finite conductivity benchmark, the migration toward larger magnetic scales is largely reproduced by Ohmic dissipation alone. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.
