The European Physical Journal C最新文献

We numerically study the complexity of a strip-shaped subregion by the subregion CV conjecture in backreacting holographic p-wave superconductors in low-dimensional Einstein–Maxwell-complex vector field theory. Based on our results with different mass and charge of the vector field, holographic complexity serves as a good probe to the superconductor phase transitions and exhibits characteristic qualitative behaviors across different types of transition. At the second order phase transition point, the complexity is continuous but non-differentiable, while at the first order and the zeroth order transition points, the complexity has a discontinuous change. The distinction between the first order and zeroth order phase transitions lies in the fact that in the former, the complexity for the normal phase and the superconducting phase can be connected by a metastable condensed phase, whereas in the latter such a metastable phase does not exist. A thermodynamically sub-dominant condensed phase known as “retrograde condensation” is also imprinted on the complexity. For this phase, the complexity only appears in the high temperature regime. Furthermore, the holographic complexity has many different behaviors from the holographic entanglement entropy. Particularly, we find that the complexity for the normal phase shows inconsistent temperature dependence in the case of (d=2) and (d=3), while such a discrepancy between different dimensions is not observed in the entanglement entropy.

True muonium, the bound state of a muon and an antimuon ((mu ^+mu ^-)), has long been theoretically predicted but remains experimentally elusive. We investigate the production of true para-muonium in the radiative decay of (J/psi ) meson, and analyze the prospects for detecting true muonium in current and future high-energy (e^+e^-) experiments, particularly focusing on the BESIII experiment and the proposed Super Tau-Charm Facility. Although the events are rare at the super tau-charm facility, the detection of true para-muonium via (J/psi ) radiative decays could become feasible at its future updates.

We construct a class of wormhole geometries supported by the non-local gravitational self-energy that regularizes the particle and black-hole sectors of spacetime. Using this framework, inspired by T-duality, we show that two entangled particles (or particle–black-hole pairs) naturally source an Einstein-Rosen–type geometry in which the required violation of the strong energy condition arises from intrinsic quantum-gravity effects rather than from ad hoc exotic matter, which is matter that violates the null energy condition. We classify the resulting wormholes, analyze their horizons, throat structure and embedding properties, and we identify the exotic energy needed at the minimal surface. Imposing the (textrm{ER}=textrm{EPR}) requirement of non-traversability and the absence of a macroscopic throat, we find that only the zero-throat geometry is compatible with an entanglement-induced Einstein–Rosen bridge, providing a concrete realization of (textrm{ER}=textrm{EPR}) within a fully regular spacetime. Finally, we briefly discuss possible implications for microscopic ER networks from vacuum fluctuations, replica-wormhole interpretations of Hawking radiation, and possible links to entanglement-driven dark-energy scenarios.

In this work, a charged fluid system is studied by employing the complexity factor formalism for a static spherical spacetime. We proceed by calculating two distinct mass functions and obtaining the Einstein field equations for the anisotropic fluid. Following Herrera’s methodology, we designate ({Y}_{TF}) as the complexity factor as it integrates the two fundamental dynamic components like the density inhomogeneity and pressure anisotropy. Additionally, the field equations are addressed by applying a few constraints, with the first being the condition of zero complexity. By implementing two distinct forms for the radial metric potential, we derive two independent solutions. The unknowns involved in these models are then found using the junction conditions by taking into account the Reissner–Nordström exterior metric. Subsequently, observed data from multiple stars is used to generate a visual depiction of the obtained solutions. Our analysis demonstrates that both proposed models maintain physically stable and viable profiles, highlighting the critical role of the vanishing complexity condition in constructing anisotropic fluid solutions under the presence of an electric charge.

We probe potential variations of the proton-to-electron mass ratio ((mu )) using high-resolution H(_2) Lyman transitions in the white dwarf GD 133, observed with the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS). White dwarf atmospheres provide a powerful laboratory for testing fundamental physics in strong gravitational fields. Applying a self-consistent spectral analysis, we obtain a tight constraint of (Delta mu /mu = (0.02 pm 0.09)) in a gravitational potential approximately (10^{4}) times stronger than that of Earth. The measured uncertainty implies that any variation of (mu ) is tightly bounded in this strong-field fields, placing meaningful limits on models predicting couplings between fundamental constants and gravity.

In this work, we construct novel traversable wormhole solutions supported by gravitational particle creation mechanism and study their physical viability through energy conditions, throat dynamics and asymptotic behavior. We further study their geometry through the lens of embedding diagrams. Subsequently, we explore their observational signatures, focusing on the shadow structure, quasinormal spectra, and greybody factors obtained via the WKB approximation. In doing so, we aim to provide a comprehensive framework where particle creation naturally sustains traversable wormholes and simultaneously enriches their phenomenology in a testable manner.

A model-agnostic search for Beyond the Standard Model physics is presented, targeting final states with at least four light leptons (electrons or muons). The search regions are separated by event topology and unsupervised machine learning is used to identify anomalous events in the full 140 fb(^{-1}) of proton–proton collision data collected with the ATLAS detector during Run 2. No significant excess above the Standard Model background expectation is observed. Model-agnostic limits are presented in each topology, along with limits on several benchmark models including vector-like leptons, wino-like charginos and neutralinos, or smuons. Limits are set on the flavourful vector-like lepton model for the first time.

Open quantum systems are powerful effective descriptions of quantum systems interacting with their environments. Studying changes of Fock state probabilities can be intricate in this context since the prevailing description of open quantum dynamics is by master equations of the systems’ reduced density matrices, which usually requires finding solutions for a set of complicated coupled differential equations. In this article, we show that such problems can be circumvented by employing a recently developed path integral-based method for directly computing reduced density matrices in scalar quantum field theory. For this purpose, we consider a real scalar field (phi ) as an open system interacting via a (lambda chi ^2phi ^2)-term with an environment comprising another real scalar field (chi ) that has a finite temperature. In particular, we investigate how the probabilities for observing the vacuum or two-particle states change over time if there were initial correlations of these Fock states. Subsequently, we apply our resulting expressions to a neutrino toy model. We show that, within our model, lighter neutrino masses would lead to a stronger distortion of the observable number of particles due to the interaction with the environment after the initial production process.

In this work, we revisit several thin-crust approximations presented in the literature and compare them with the exact solutions of the Tolman–Oppenheimer–Volkoff (TOV) equations. In addition, we employ three different equations of state (EoSs) and one with pasta phase, each based on a distinct framework: the variational method, relativistic Brueckner–Hartree–Fock, and relativistic mean-field theory. We emphasize that these approximations require only the TOV solutions for the core and the EoS properties at the core–crust interface, in our approach only the energy density. Finally, the relativistic approximation, as well as the Newtonian approximation with corrections, show good agreement with the exact solutions. This means that a simple treatment of the crust would suffice for structural purposes, independently of the possible uncertainties in the sub-nuclear equation of state which are not very large. The unified EOS SINPA (relativistic mean-field theory) including the pasta phase was used to study the thin-crust approximation, while degeneracy in the (M)-(R) relation is demonstrated through: (i) anisotropic pressure in the modified TOV equation, (ii) (f(R,L_m,T)) gravity model, and (iii) dark matter admixture. As demonstrated, modifications to the description of gravitation introduce degeneracies in the mass–radius relation that are challenging to disentangle or quantify precisely.