The European Physical Journal C最新文献

In this paper we study the shadow and quasi-normal modes (QNMs) of a black hole (BH) surrounded by a dark matter halo with Hernquist-type density distribution, which was reported in Cardoso et al. (Phys. Rev. D 105(6):L061501, 2022). In astrophysical scenarios, we find that the shadow radius enlarges as the compactness of halo increases. Therefore, we obtain an upper bound for the compactness (mathcal{C}le 0.092) with the Event Horizon Telescope (EHT) observations. We calculate axial gravitational QNMs of the galactic BH up to (mathcal{C}sim mathcal{O}(1)), and fit the redshift relative to Schwarzschild QNMs up to second order in the compactness (for (mathcal{C}le 0.3)). These highly redshifted QNMs, resulting from large compactness, are key to modeling the dark matter halo.

Vacuum Cherenkov radiation is investigated in the Lorentz-violating Standard-Model Extension for isotropic dim-5 operators (hat{m}) and (hat{a}^{mu }) in the fermion sector. Both the kinematics and dynamics of this process are studied by analytical and numerical means, leading to its decay and radiated-energy rates as functions of the initial-fermion momentum. We adopt the point of view that vacuum Cherenkov radiation is actually a physical phenomenon expected to occur for a charged, massive fermion in the presence of Lorentz violation, when some additional requirements are satisfied. The absence of this effect in ultrahigh-energy cosmic rays detected on Earth allows us to infer stringent bounds on isotropic dim-5 Lorentz violation in protons, quarks, and electrons.

We present an exact analytical study of null trajectories and scalar wave propagation in a ((2+1))-dimensional spacetime containing a spiral dislocation, a topological defect characterized by torsion in the absence of curvature. For null rays, the torsion parameter (beta ) modifies the affine structure, enforcing a finite turning radius (r_{min } = sqrt{b^2 - beta ^2}), and inducing a torsion-mediated angular deflection that decreases monotonically with increasing (beta ). The photon trajectory departs from the curvature-induced lensing paradigm, exhibiting instead a purely topological exclusion zone around the defect core. Moreover, the results can, in principle, be mapped onto laboratory frames and conditions. In the wave regime, we recast the Helmholtz equation into a Schrödinger-like form and extract a spatially and spectrally dependent refractive index (n^2(r,k)). This index approaches unity asymptotically at large distances but diverges strongly and negatively near the dislocation core due to torsion-induced geometric contributions. The resulting refractive index profile governs the transition from propagating to evanescent wave behavior, with low-frequency modes undergoing pronounced localization and suppression. Our findings demonstrate that torsion alone, even in the absence of curvature, can act as a geometric regulator of both classical and quantum propagation, inducing effective anisotropy, frequency filtering, and confinement. This framework provides a rare exact realization of light-matter interaction in a torsion-dominated background, with potential applications in analog gravity systems and photonic metamaterials designed to emulate non-Riemannian geometries.

NUCLEUS is a cryogenic detection experiment which aims to measure Coherent Elastic Neutrino–Nucleus Scattering (CE(nu )NS) and to search for new physics at the Chooz nuclear power plant in France. This article reports on the prediction of particle-induced backgrounds, especially focusing on the sub-keV energy range, which is a poorly known region where most of the CE(nu )NS signal from reactor antineutrinos is expected. Together with measurements of the environmental background radiations at the experimental site, extensive Monte Carlo simulations based on the Geant4 package were run both to optimize the experimental setup for background reduction and to estimate the residual rates arising from different contributions such as cosmic ray-induced radiations, environmental gammas and material radioactivity. The NUCLEUS experimental setup is predicted to achieve a total rejection power of more than two orders of magnitude, leaving a residual background component which is strongly dominated by cosmic ray-induced neutrons. In the CE(nu )NS signal region of interest between 10 and 100 eV, a total particle background rate of (sim ) 250 d⁻¹ kg⁻¹ keV⁻¹ is expected in the CaWO₄ target detectors. This corresponds to a signal-to-background ratio (gtrsim ) 1, and therefore meets the required specifications in terms of particle background rejection for the detection of reactor antineutrinos through CE(nu )NS.

SPARKX is an open-source Python package developed to analyze simulation data from heavy-ion collision experiments. By offering a comprehensive suite of tools, SPARKX simplifies data analysis workflows, supports multiple formats such as OSCAR2013, and integrates seamlessly with SMASH and JETSCAPE/X-SCAPE. This paper describes SPARKX’s architecture, features, and applications and demonstrates its effectiveness through detailed examples and performance benchmarks. SPARKX enhances productivity and precision in relativistic kinematics studies.

The Blandford–Znajek (BZ) process is a pivotal mechanism to efficiently extract the energy from a rotating black hole (BH) via its plasma-filled magnetosphere in relativistic astrophysics. Within the framework of extended BZ monopole expansion, we have studied BZ process in the Randall–Sundrum braneworld BH spacetime and analyzed effects of the tidal charge on the energy and angular momentum extraction rates. It is found that the positive tidal charge reduces the BZ power of a braneworld BH, while the negative tidal charge enhances the power. Compared with a Kerr BH of the same mass and angular velocity, the BZ power exhibits a maximum reduction of approximately (15.2%) in positive cases, whereas in negative cases, it achieves a maximum enhancement of (66.5%) in power output. A similar qualitative trend is also observed for the relative angular momentum extraction rate, albeit with different magnitudes.

Gravitational wave signals emitted during the binary neutron star inspiral phase offer a promising avenue for probing stellar internal composition. Isovector–scalar mesons and kaon condensation are thought to play pivotal roles in characterizing asymmetric nuclear matter and constraining the dense nuclear equation of state. This study explores whether their potential effects in neutron stars can be identified from inspiral gravitational wave frequencies, retarded times and orbital phases. Our analysis reveals the isovector–scalar meson accelerates the inspiral process, leading to shorter retarded times and lower maximum gravitational wave frequencies compared to standard binary neutron star systems, while binary systems influenced by kaon condensation exhibit even shorter inspiral retarded times and lower gravitational wave frequencies than those influenced solely by isovector–scalar mesons. Quantitatively, the incorporation of kaon condensation leads to a reduction of approximately 200 Hz in the maximum inspiral gravitational wave frequency, and the variations in retarded times across different kaon potentials reach approximately five milliseconds, whereas the corresponding variations induced by isovector–scalar mesons are around one millisecond. Combined with observable mass–radius relationships and tidal deformabilities, our findings strongly suggest that inspiral gravitational wave signals could serve as a strategic probe for identifying potential isovector–scalar and kaon mesons.

In this work, we test the cosmic distance duality relation (CDDR) using the arbitrary redshift pivot Padé-(2,1) expansion methodology developed in Ref Fazzari et al. http://arxiv.org/abs/2509.16196. This approach allows us to constrain the cosmography parameters and test the CDDR at any redshift. Further, it does not rely on data reconstructions or extrapolations of the cosmography parameters to higher redshifts. We employ observational data from the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation dataset, cosmic chronometers (CC), and Type Ia supernovae from the Pantheon Plus (PP) and Dark Energy Survey Year 5 (DESY5) compilations. We find no significant deviations from the standard CDDR relation in the range (0lesssim z lesssim 1) when considering DESI(+r_d) dataset in combination with PP+CC and DESY5+CC datasets. However, on imposing a Gaussian prior on (M_B in mathcal {N}(-19.253, 0.027)) (instead of treating it as a free parameter) in the dataset combination PP+CC, we find CDDR violation at a level of ((3-5)sigma .)

Though investigated extensively in the past, we take a detailed relook at the study of quasinormal modes (QNM) in a known family of wormholes (ultrastatic ((g_{00}=-1)), as well as spacetimes with different, non-constant (g_{00})), which includes the familiar Bronnikov–Ellis spacetime as a special case. Our focus here is to go beyond the fundamental mode and obtain some of the QNM overtones using a suitable numerical scheme. Scalar and axial gravitational QNMs including two or three overtones are obtained for the family of ultrastatic geometries and their parameter dependencies are shown explicitly. Further, we comment on how (a) the overtones may influence the time-domain profile in a perturbation and (b) in what sense, the use of overtones may help in distinguishing between different geometries within the family. Finally, we show how an effect somewhat similar to the so-called ‘environment induced redshift’ of QNMs, introduced recently (Pezzella et al. in Phys Rev D 111:064026, 2025), may be obtained for spacetimes with non-constant (g_{00}), via an appropriate tuning of available metric parameters which systematically modify the shapes of the effective potentials arising in the perturbation equations.