The European Physical Journal C最新文献

In this article, we discuss several compact objects (GW 190814, PSR J0952-0607, PSR J0030+0451, PSR J0740+6620,   GW 170817,   PSR J1614-2230,   PSR J2215+5135, and 4U 1608-52) to predict their masses and radii. A generalized polytropic stellar model within the framework of general relativity is derived by employing the Buchdahl-I metric. All the physical quantities such as energy density, radial, and tangential pressure are well behaved, continuous and no singularity is observed. The obtained results are compatible with observational data for compact objects under consideration. The physical stability of this model is determined by using generalized hydrostatic equilibrium condition, energy conditions, causality conditions and Herrera’s cracking technique. We observe that our model fulfills all of the requirements for being a physically realistic model.

For neutron stars, there exist universal relations insensitive to the equation of states, the so called I-Love-Q relations, which show the connections among the moment of inertia, tidal Love number and quadrupole moment. In this paper, we show that these relations also apply to dark stars, bosonic or fermionic. The relations can be extended to higher ranges of the variables, clarifying the deviations for dark stars in the literature, as those curves all approximate the ones generated by a polytropic equation of state, when taking the low density (pressure) limit. Besides, we find that for equation of states with scaling symmetries, the I-Love-Q curves do not change when adjusting the scaling parameters.

In this work, we construct novel asymptotically locally AdS(_5) black hole solutions of Einstein–Gauss–Bonnet theory at the Chern–Simons point, supported by a scalar field that generates a primary hair. The strength of the scalar field is governed by an independent integration constant; when this constant vanishes, the spacetime reduces to a black hole geometry devoid of hair. The existence of these solutions is intrinsically tied to the horizon metric, which is modeled by three non-trivial Thurston geometries: Nil, Solv, and (SL(2,{mathbb {R}}).) The quadratic part of the scalar field action corresponds to a conformally coupled scalar in five dimensions -an invariance of the matter sector that is explicitly broken by the introduction of a quartic self-interaction. These black holes are characterized by two distinct parameters: the horizon radius and the temperature. Notably, there exists a straight line in this parameter space along which the horizon geometry exhibits enhanced isometries, corresponding to solutions previously reported in JHEP 02, 014 (2014). Away from this line, for a fixed horizon radius and temperatures above or below a critical value, the metric’s isometries undergo spontaneous breaking. Employing the Regge–Teitelboim approach, we compute the mass and entropy of these solutions, both of which vanish. Despite this, only one of the integration constants can be interpreted as hair, as the other modifies the local geometry at the conformal boundary. Finally, for Solv horizon geometries, we extend these hairy solutions to six dimensions.

We investigate an interacting quintessence dark energy – dark matter scenario and its impact on structure formation by analyzing the evolution of scalar perturbations. The interaction is introduced by incorporating a non-zero source term into the continuity equations of the two sectors (with opposite signs), modeled as (bar{Q}_0 equiv alpha bar{rho }_textrm{m}(H + kappa dot{phi })). The coupling parameter (alpha ) and the parameter (lambda ) involved in quintessence potential (V(phi ) = V_0e^{-lambda kappa phi }), play crucial roles in governing the dynamics of evolution examined within the present framework. The cosmic evolution, within this context, is depicted as a first-order autonomous system of equations involving appropriately chosen dynamical variables. We analyzed the associated stability characteristics and growth rate of perturbations, and obtained domains in the ((alpha -lambda )) parameter space for which fixed points can exhibit stable and non-phantom accelerating solutions. Depending on its magnitude, the coupling parameter (alpha ) has the potential to change the characteristics of certain critical points, altering them from attractors to repellers. This model effectively captures the evolutionary features of the universe across its various phases at both the background and perturbation levels. The issue of cosmic coincidence can also be addressed within the framework of this model. We also observed that for a moderate strength of coupling, the growth rate of matter perturbation extends into the distant future.

In this study, we investigate the Weak Gravity Conjecture (WGC) in the context of quantum-corrected Reissner–Nordstrom–AdS (RN-AdS) black holes within Kiselev spacetime. Our focus is on photon spheres, which serve as markers for stable and unstable photon spheres. We confirm the validity of the WGC by demonstrating that quantum corrections do not alter the essential charge-to-mass ratio, thereby supporting the conjecture’s universality. Our analysis reveals that black holes with a charge greater than their mass ((Q > M)) possess photon spheres or exhibit a total topological charge of the photon sphere ((text {PS} = -1),) which upholds the WGC. This finding is significant as it reinforces the conjecture’s applicability even in the presence of quantum corrections. Furthermore, we examine various parameter configurations to understand their impact on the WGC. Specifically, we find that configurations with (omega = -frac{1}{3}) and (omega = -1) maintain the conjecture, indicating that these values do not disrupt the charge-to-mass ratio required by the WGC. However, for (omega = -frac{4}{3},) the conjecture does not hold, suggesting that this particular parameter value leads to deviations from the expected behavior. These results open new directions for research in quantum gravity, as they highlight the importance of specific parameter values in maintaining the WGC. The findings suggest that while the WGC is robust under certain conditions, there are scenarios where it may be challenged, prompting further investigation into the underlying principles of quantum gravity.

Self-gravitating horizonless ultra-compact objects that possess light rings have attracted the attention of physicists and mathematicians in recent years. In the present compact paper we raise the following physically interesting question: Is there a lower bound on the global compactness parameters (mathcal{C}equiv text {max}_r{2m(r)/r}) of spherically symmetric ultra-compact objects? Using the non-linearly coupled Einstein-matter field equations we explicitly prove that spatially regular ultra-compact objects with monotonically decreasing density functions (or monotonically decreasing radial pressure functions) are characterized by the lower bound (mathcal{C}ge 1/3) on their dimensionless compactness parameters.

We compute the invariant mass of dijets produced in (e^+ e^-) annihilation processes up to four loops in perturbation theory for both anti-(k_t) and (k_t) jet algorithms. The calculations, performed within the eikonal approximation and employing strong-energy ordering, capture the full analytic structure of the leading Abelian and non-Abelian non-global logarithms, including full colour and jet-radius dependence. We evaluate the significance of these logarithms and the convergence of the four loop perturbative expansion by comparing with all-orders numerical results.

We present an analysis of the exclusive semileptonic decay (Brightarrow D^*ell bar{nu }_ell ) based on the Belle and Belle II data made public in 2023, combined with recent lattice-QCD calculations of the hadronic transition form factors by FNAL/MILC, HPQCD and JLQCD. We also consider a new combination of the Belle and Belle II data sets by HFLAV. The analysis is based on the form-factor parameterisation by Boyd–Grinstein–Lebed (BGL), using Bayesian and frequentist statistics, for which we discuss novel strategies. We compare the results of an analysis where the BGL parameterisation is fit only to the lattice data with those from a simultaneous fit to lattice and experiment, and discuss the resulting predictions for the CKM-matrix element ({|V_{cb}|}), as well as other phenomenological observables, such as (R^{tau /mu }(D^*)). We find tensions when comparing analyses based on different combinations of experimental or theoretical input, requiring the introduction of a systematic error for some of our results.

The static spherically symmetric thin shell of proper mass m and electric charge q around a central star or black hole of mass M is in general unstable. Although with fine-tuned m, q,  and M it can be considered quasi-stable. These facts have been recently proved by Hod (Eur Phys J C 84:1148, https://doi.org/10.1140/epjc/s10052-024-13546-3, 2024) from which we are inspired to investigate the stability status of the throat of a spherically symmetric thin-shell wormhole (TSW) with the same proper mass and charge. Precisely, in this compact paper, we introduce the radius of stability for the throat of a static spherically symmetric charged TSW, by optimizing its energy measured by an asymptotic observer. Furthermore, we prove that at the stable equilibrium radius, the tension on the throat is zero, and a perturbation in the form of an initial kinetic energy results in an effective attractive potential such that the throat oscillates around the equilibrium point.

Experimental searches for supersymmetry (SUSY) are entering a new era. The failure to observe signals of sparticle production at the large hadron collider (LHC) has eroded the central motivation for SUSY breaking at the weak scale. However, String Theory requires SUSY at the fundamental scale (M_s) and hence SUSY could be broken at some high scale below (M_s). Actually, if this were the case, the lack of experimental evidence for low-energy SUSY could have been anticipated, because most stringy models with high-scale SUSY breaking predict that sparticles would start popping up above about 10 TeV, well beyond the reach of current LHC experiments. We show that using next generation LHC experiments currently envisioned for the Forward Physics Facility (FPF) we could search for signals of neutrino-modulino oscillations to probe models with string scale in the grand unification region and SUSY breaking driven by sequestered gravity in gauge mediation. This is possible because of the unprecedented flux of neutrinos to be produced as secondary products in LHC collisions during the high-luminosity era and the capability of FPF experiments to detect and identify their flavors.