The European Physical Journal C最新文献

We investigate the fermion system excited by a free Dirac spinor field near the throat of a global monopole wormhole, characterized by the equation-of-state parameter (xi ) of the exotic fluid supporting the wormhole and the symmetry-breaking scale (eta ) of the monopole. From the perspective of the spacetime metric alone, there have no significant distinction for different values of (xi ) and (eta ). However, when the spinor field is introduced as a probe and macroscopic physical quantities, such as fermion condensation, energy density, radial pressure, and angular stress, are calculated, we find that these quantities are able to uncover distinct physical behaviors corresponding to different combinations of (xi ) and (eta ). Meanwhile, we find that the fermion condensation is closely related to the strong energy condition and undergoes a notable phase transition as (eta ) increases. Furthermore, the free energy density is analyzed to investigate the stability of the fermion system under varying parameter combinations of (xi ) and (eta ). Besides, both scenarios of normal fermions and exotic fermions are considered in this analysis, highlighting the contrasting physical properties between these two cases.

We construct the Hamiltonian formulation of the isotropic Universe in a generic metric f(R)-theory in the Jordan frame. We canonically quantize the Universe volume via a polymer formulation, and we adopt the scalar field naturally arising from this scenario as a physical clock. Being within the limit of cut-off values of the space volume, we are legitimized to neglect, at first approximation level, the self-interacting potential term associated with the scalar field. We first study the semi-classical polymer dynamics, outlining the emergence of a bouncing cosmology, both in the internal as well as in the synchronous time. In this latter time variable, we are also able to compare the obtained picture with that of a standard polymer Big-Bounce. We see that in the studied case, the collapsing and expanding branches are no longer symmetric with respect to the minimum volume configuration. Then, we fully quantize the system dynamics in the momentum representation, constructing a suitable dynamical Hilbert space and setting up the dynamics of localized wave packets. The mean value dynamics, both for the momentum and volume spaces, is characterized by a bouncing dynamics as described via the internal time, which closely resembles that one obtained in Loop Quantum Cosmology and Polymerization, respectively.

In this paper, a new Monte Carlo Glauber model is developed for pA collisions. It uses the hadronic cross sections calculated within the KMR model as implemented in the SHRiMPS minimum bias module of the SHERPA event generator. These cross sections are obtained as functions of impact parameter and, therefore, are ready for use in a Glauber model without additional assumptions regarding their impact parameter dependence. We compare the results obtained with those from a Black Disk model and from another model with colour fluctuations. It is shown that the KMR/SHRiMPS cross sections may present very good descriptions of the multiplicity distributions in pA collisions given that they show a long tail in the distribution of wounded nucleons. Moreover, it is shown that they also increase the anisotropy in the spatial distribution of wounded nucleons, which can be important in the description of the initial states of pA collisions. The generalization to A+A collisions is straightforward.

We investigate tripartite quantum-memory-assisted entropic uncertain and quantum coherence for GHZ and W states of a fermionic field in the background of a spherically symmetric black hole of Einstein–Gauss–Bonnet (EGB) gravity. Two distinct scenarios are analyzed: (i) the quantum memories (held by Bob and Charlie) are near the horizon while the measured particle (Alice) remains in the flat region, and (ii) the reverse configuration. Dimensional dependence is observed: in (d>5) dimensions, the measurement uncertainty decreases monotonically with increasing horizon radius, while coherence increases; in (d=5), both quantities exhibit non-monotonic behavior due to distinctive thermodynamic properties. Furthermore, comparative analysis reveals that the W state exhibits higher robustness in preserving coherence, whereas the GHZ state shows greater resistance to measurement uncertainty increase induced by Hawking radiation. Notably, the two scenarios yield qualitatively distinct behaviors: quantum coherence is consistently lower in Scenario 1 (quantum memory near horizon) than in Scenario 2 (measured particle near horizon), irrespective of the quantum state. For measurement uncertainty, the W state displays lower uncertainty in Scenario 1, while the GHZ state exhibits the opposite trend, with higher measurement uncertainty in Scenario 1. These results indicate that the characteristics of different quantum resources provide important insights into the selection and optimization of quantum states for information processing in curved spacetime.

In this work, we demonstrate that the hyperboloidal foliation technique, applied to the study of black hole quasinormal modes, where the spatial boundary is shifted from spacelike infinity to the future event horizon and null infinity, is effectively equivalent to the continued fraction approach, in which the asymptotic wave function typically diverges at both ends of spatial infinity. Specifically, a given hyperboloidal slicing, corresponding to a particular choice of coordinates, always uniquely determines a scheme for extracting the asymptotic form of the wave function at the spatial boundary. Owing to the mathematical equivalence, it follows that the efficiency and precision observed using the hyperboloidal approach should be attributed, not to avoiding the pathological behavior at the spatial boundaries, but primarily to other factors, such as the use of Chebyshev grids.

We study the energy loss of the heavy quark and the heavy quark jet propagating through linear expanding quark–gluon plasma (QGP). We show that the concept of scaling is valid for heavy quarks, with the quenching parameter of the equivalent static media being independent from the mass of the quark.

We investigate the spacetime geometry and astrophysical properties of a static, spherically symmetric black hole in the context of Einstein–Gauss–Bonnet gravity, characterized by a Gauss–Bonnet coupling constant (kappa ) and a non-electromagnetic geometric charge Q. The black hole solution reduces to the Reissner–Nordstrom or Schwarzschild spacetime in the appropriate limits. We analyze the influence of the parameters (kappa ) and Q on the event horizon properties, the innermost stable circular orbit, and the spacetime metric behavior. In the framework of the Novikov–Thorne thin disk model, we compute the flux, temperature, and spectrum of the accretion disk surrounding the black hole. Our results show that the parameters (kappa ) and Q significantly affect the disk’s thermal properties and radiation efficiency. Additionally, we demonstrate that the combined effect of these parameters can mimic the role of spin in Kerr black holes, allowing for degeneracy between rotation and geometric corrections. These findings offer potential observational signatures of modified gravity effects in high-energy astrophysical environments.

In this paper we propose a resolution to the problem of (beta )-deforming the non-Gaussian monomial matrix models. The naive guess of substituting Schur polynomials with Jack polynomials does not work in that case, therefore we are forced to look for another basis for superintegrability. We find that the relevant symmetric functions are given by Uglov polynomials, and that the integration measure should also be deformed. The measure appears to be related to the Uglov limit as well, when the quantum parameters (q, t) go to a root of unity. The degree of the root must be equal to the degree of the potential. One cannot derive these results directly, for example, by studying Virasoro constraints. Instead, we use the recently developed techniques of W-operators to arrive at the root of unity limit. From the perspective of matrix models this new example demonstrates that even with a rather nontrivial integration measure one can find a superintegrability basis by studying the hidden symmetry of the moduli space of deformations.

We compute the photon polarization tensor at one-loop order in the presence of a constant and uniform electric field. Our calculation is carried out for arbitrary field strength using the Schwinger proper-time formalism, and we explicitly derive an expression for the polarization tensor without approximations. We also present a complementary derivation within the strong field approximation. Our main contribution lies in expressing the polarization tensor in terms of a physically motivated tensor basis that ensures transversality and thus preserves gauge invariance. This basis, constructed from the preferred direction defined by the external electric field, makes explicit the breaking of Lorentz symmetry. We verify the consistency of our results by recovering the well-known vacuum polarization tensor in the zero-field limit and by demonstrating agreement between the strong field limit of the general expression and the result obtained directly in the strong field approximation. Interestingly, in the latter case, only one tensor structure survives, corresponding to the transverse dynamics with respect to the field direction, which highlights the dominance of perpendicular modes.

A straightforward and fully analytic approach is introduced to examine how polytropic fluids influence arbitrary gravitational sources in static, spherically symmetric spacetimes. As a concrete application, we explore the internal mechanism of energy transfer between gravitational sources embedded within a self-gravitating system.