The European Physical Journal C最新文献

We consider a rational scalar field model in (1+1)-dimensions where the long-range character of the kinks is controllable. We show via numerical simulations that kinks with long-range tails on both sides can exhibit resonance windows. The resonant energy exchange mechanism occurs via the excitation of quasinormal modes, which we obtain via a spectral analysis. Additionally, we locate a resonance window in a family of (phi ^{10}) models with long-range tails on both sides. Moreover, we propose a new algorithm for initializing long-range kink collisions, based on convection–diffusion dynamics.

We investigate two-body non-leptonic (Drightarrow SS) weak decays, where S denotes a light scalar meson such as (a_0/a_0(980),) (f_0/f_0(980),) or (sigma _0/f_0(500).) Short-distance topologies from W-boson emission and annihilation (exchange) are found to be negligible, while long-distance final-state interactions provide the dominant contributions. In particular, triangle rescattering processes, (D rightarrow pi eta ^{(prime )} rightarrow sigma _0 a_0) and (D rightarrow a_1(1260)eta rightarrow sigma _0 a_0,) mediated by pion exchange in (pi eta ^{(prime )}) and (a_1(1260)eta ) scatterings, respectively, are identified as the leading mechanisms. Our calculations yield branching fractions ({mathcal {B}}(D_s^+ rightarrow sigma _0 a_0^+) = (1.0 pm 0.2^{+0.1}_{-0.2}) times 10^{-2},) ({mathcal {B}}(D^+ rightarrow sigma _0 a_0^+) = (1.1 pm 0.2^{+0.1}_{-0.2}) times 10^{-3},) and ({mathcal {B}}(D^0 rightarrow sigma _0 a_0^0) = (0.9 pm 0.2^{+0.2}_{-0.3}) times 10^{-5}.) For the Cabibbo-allowed decay mode (D_s^+ rightarrow f_0 a_0^+,) the near-threshold condition (m_{D_s}simeq m_{f_0}+m_{a_0}) limits the phase space, suppressing the branching fraction to ((3.4pm 0.3^{+0.4}_{-0.9})times 10^{-4}.) These results highlight rescattering-induced (Drightarrow SS) decays as promising channels for experimental studies at BESIII, Belle(-II), and LHCb.

Cosmological implications of a class of hybrid metric-Palatini gravity with a non-minimal matter-geometry coupling is considered. The theory contains a metric curvature tensor, together with a curvature tensor constructed from an independent affine connection. We will show that the model could be written as a bi-scalar–tensor gravity with a non-minimal coupling between matter sector and a scalar field. The theory will then be confronted with observational data from Cosmic Chronometers, BAO dataset from DESI and the Pantheon(^+) dataset. We will show that the theory could be a good alternative to the (Lambda )CDM model with the difference that the conservation of the baryonic matter sector holds only at the background level. The statefinder analysis will also be applied to the theory and it is observed that the DE behavior of the theory exhibits a quintessence to phantom transition occurs at redshifts around (zapprox 0.86).

In this paper, the quantum corrections to the kinematics of geometry, specifically geodesics, are presented. This is done by employing the path integral over the geodesics. Interestingly, the geodesics do not see any modifications in this framework. However for the distances, it is demonstrated that these quantum corrections exhibit distinct behaviors for time-like, light-like, and space-like geodesics. For time-like geodesics, the maximum correction is the Planck length, which disappears when the classical separation vanishes. The light-like geodesics do not exhibit quantum corrections, meaning that the causal light cone remains the same in both classical and quantum frameworks under certain conditions. The quantum corrections for space-like geodesics impose a minimum on space-like separation, potentially playing a role in removing singularities by preventing null congruences from being closer than the Planck length. This framework also explores the correspondence between space-like/time-like geodesics and quantum/statistical physics.

The minimal supergravity framework is applied to a construction of new D-type single-field models of inflation in agreement with precision measurements of the cosmic microwave background radiation by Planck Collaboration, BICEP/Keck Collaboration, Atacama Cosmology Telescope and South Pole Telescope. The inflaton potential, the power spectrum of scalar perturbations, the cosmological observables and the reconstruction procedure can be very simple when using the e-folds as the running variable.

Starting from a generic Lagrangian, we discuss the number of propagating degrees of freedom in the framework of generalised non-linear electrodynamics when a photon-background split is applied. We start by stating results obtained in a previous paper, before modifying the action to an equivalent form. Within this new formulation, we highlight the presence of an effective mass and consider the mechanical reduction of the model to ensure the positivity of said mass. We then study the constraint algebra of the model and show that we shift from a model with two first-class to two second-class constraints, which implies the propagation of an additional degree of freedom. We also show that the Hamiltonian is bound from below and thus does not suffer from Ostrogradski-type instabilities. We conclude by deriving the propagator for the model, and discussing the potential link between the nature of this additional polarisation and the mechanism behind the effective mass generation in this class of models.

The Lee–Wick pseudo-quantum electrodynamics in the presence of a Chern–Simons term is studied in this paper. The paper starts with a non-local lagrangian density that sets the pseudo-Lee–Wick electrodynamics defined on a (1+2) space-time added to a non-local Chern–Simons topological term. Thus, we obtain the Lee–Wick–Chern–Simons pseudo-electrodynamics as a most complete gauge invariant model that provides a light mass associated with the Chern–Simons parameter, and also includes a Lee–Wick heavy mass. We investigate classical aspects as the potential energy for the interaction of static charges through the gauge propagator. The causality of theory is discussed through the retarded Green function in the coordinate space. The gauge field of the Lee–Wick–Chern–Simons pseudo-electrodynamics is minimally coupled to the fermions sector that includes new degree of freedoms, as a Lee–Wick heavy fermion partner of the electron. The perturbative approach for the theory is presented via effective action in which we obtain the Ward identities. We study the quantum corrections at one loop, as the electron self-energy, the vacuum polarization, and the 3-vertex. We show that the Lee–Wick mass has a fundamental role in these results, where it works like a natural regulator of the ultraviolet divergences. The (g-2) factor for the electron is obtained as function of the LW mass, and of the CS parameter. Through the optical theorem, the Lee–Wick–Chern–Simons pseudo-electrodynamics is unitary at the tree level.

Using the AMPT model, we study charged hadron elliptic flow ((v_{2})) centrality dependence in Au+Au collisions at (sqrt{s_{NN}}=200~textrm{GeV}). We find distinct centrality-dependent roles for partonic ((sigma _{p})) and hadronic ((sigma _{H})) transport processes. In central collisions, (v_{2}) is dominantly amplified by larger (sigma _{p}) (reducing partonic viscosity) but insensitive to (sigma _{H}). In peripheral collisions, larger (sigma _{H}) (reducing hadronic viscosity) significantly enhances (v_{2}), flattening its centrality dependence and improving agreement with STAR data. Initial pressure gradients (enhanced by Lund parameter (a_{L})) also increase (v_{2}), while (b_{L}) affects spectra but not flow. This centrality-differential sensitivity to (sigma _{p}) and (sigma _{H}) provides a novel strategy for extracting phase-specific shear viscosities.

This study investigates the construction and stability of thin-shell wormholes derived from the modified Bardeen anti-de Sitter (AdS) black hole. The thin-shell wormhole is constructed using Visser’s cut-and-paste method, which involves matching two identical black hole spacetimes at a hypersurface to form a throat that connects the geometries. Wormhole’s stability is examined through the Israel formalism, which provides the surface stress-energy tensor at the throat. The violation of energy conditions, a hallmark of exotic matter, is explored in detail. Linearised stability analysis is performed by perturbing the wormhole throat and analysing the resulting equations of motion. Various equations of state (EoS), including barotropic, generalised phantom-like, and generalised Chaplygin gas models, are considered to study the behaviour of the system under radial perturbations. Our findings demonstrate that a thin-shell wormhole’s stability strongly depends on the throat radius, charge parameters, and cosmological constant. Furthermore, the influence of EoS parameters is crucial in determining the stable and unstable configurations of the wormhole. This study highlights the critical role of modified black hole geometries in constructing physically viable and stable wormhole solutions in the context of AdS spacetimes.

In data-driven determination of Parton Distribution Functions (PDFs) in global QCD analyses, uncovering the true underlying distributions is complicated by a highly convoluted inverse problem. The determination of PDFs can be understood as the inference of a function supported on [0, 1], a problem that admits multiple acceptable solutions. An ensemble of solutions exists that pass all standard goodness-of-fit criteria. In this paper, we propose algorithms for the classification, clustering, and selection of solutions to the determination of PDFs, or any functions on [0, 1], based on the characterization of their shape. We explore information-theoretic based (Rényi entropy and divergence) and optimal-transport based (Wasserstein distance) criteria. In particular, we advocate for the use of the Rényi entropy as an absolute estimator per solution, as opposed to relative estimators that compare solutions pairwise. We show that the Rényi entropy can characterize the space of solutions w.r.t. the PDF shapes. Paired with the identification of the optimal combination of solutions via Pareto fronts, it provides a plausible and minimalist selection algorithm. Moreover, Rényi entropy proves versatile for use in clustering applications.