The European Physical Journal C最新文献

In this paper, we investigate a series of topologically charged exponential traversable wormhole models described by the standard metric form:

where (0< alpha < 1) is the global monopole chare parameter. We focus on the positivity of the energy density across these models, defined by the following functions: (i) (mathcal {A}(r)=exp left( -frac{M}{r}right) ) and (mathcal {B}(r)=exp left( frac{M}{r}+beta ,rright) ), (ii) (mathcal {A}(r)=exp left( -frac{M}{r}-gamma ,rright) ) and (mathcal {B}(r)=exp left( frac{M}{r}right) ), and (iii) (mathcal {A}(r)=exp left( -frac{M}{r}-gamma ,rright) ) and (mathcal {B}(r)=exp left( frac{M}{r}+beta ,rright) ), where (M, beta ) and (gamma ) are constants. For each model, we evaluate key properties such as the wormhole throat radius, geometric stability, and energy conditions. Additionally, we analyze geodesic motions of test particle around a generalized wormhole, highlighting how the presence of the global monopole parameter affects trajectories of test particles within this topologically charged wormhole. Our results demonstrate that the radius of the wormhole throat is consistent with established characteristics of traversable wormholes and is free from singularities. subsequently, we study the Regge–Wheeler (RW) potential in the context of our chosen wormhole background, providing a detail analysis of its implications for spin zero scalar s-waves with multipole number (ell =0). our analysis shows that the RW potential for spin zero scalar field is influence by the global monopole parameter and the coupling constant, which possesses dimensions inverse to that of length present in the wormhole space-time geometry. This modification has profound implications for the stability and dynamics of scalar perturbations in the vicinity of the wormhole, potentially affecting the stability of the wormhole itself.

The present work analyses Raychaudhuri equation (RE) in Einstein gravity for two interacting fluids. Focusing theorem, a consequence of RE, is directly related to the singularity theorems of Penrose and Hawking. In the present work, the signature of the Raychaudhuri scalar or convergence scalar has been examined for two types of interaction forms namely, (i) (Q=H(alpha rho _1+beta rho _2)) (linear) and (ii) (Q=dfrac{Hxi rho _1rho _2}{alpha rho _1+beta rho _2}) (non-linear). Finally, the phenomena of focusing of a congruence of geodesics and possible avoidance of singularity have been discussed based on the nature of the two fluids and the interaction term operating between them.

A symmetry preserving treatment of a vector (otimes ) vector contact interaction (SCI) is used as the basis for calculations of the two pion transverse momentum dependent parton distribution functions (TMDs); namely, that for unpolarised valence degrees-of-freedom and the analogous Boer–Mulders (BM) function. Amongst other things, the analysis enables the following themes to be addressed: the quark current mass dependence of pion TMDs; the impact of the gauge link model on the positivity constraint that bounds the BM function relative to the unpolarised TMD; the equivalence of direct diagrammatic and light-front wave function TMD calculations; and the size of the BM shift. Interpreted astutely, these SCI results enable one to draw insightful pictures of pion TMDs.

We investigate the effects of the bottom-quark induced processes on the doubly polarized cross sections of (W^+W^-) pair production at the LHC. The method to extract the on-shell single-top contribution is provided. Results for phenomenological and experimental analyses are given at next-to-leading order (NLO) QCD + EW accuracy, with the leading contribution from the gluon–gluon and photon–photon fusion included. We found that the contribution of the bottom-quark induced processes, after the subtraction of the on-shell tW channel, is largest for the doubly longitudinal polarization. At the integrated cross section level, using a fiducial ATLAS cut with a jet veto, the effect is (9%) compared to the NLO value of the light-quark contribution. It increases to (13%) after removing the jet veto. A bound of the tW interference is calculated for various kinematic distributions, showing that this interference effect is, in general, smaller for the no jet veto case. Relevant scale uncertainties are calculated to help us decide on the importance of this interference.

Assuming fundamental fermions possess a new Abelian gauge charge that depends on flavors of both quark and lepton, we obtain a simple extension of the Standard Model, which reveals some new physics insights. The new gauge charge anomaly cancellation not only explains the existence of just three fermion generations as observed but also requires the presence of a unique right-handed neutrino (nu _R) with a non-zero new gauge charge. Further, the new gauge charge breaking supplies a residual matter parity, under which the fundamental fermions and (nu _R) are even, whereas a right-handed neutrino (N_R) without the new charge is odd. Consequently, light neutrino masses in our model are generated from the tree-level type-I seesaw mechanism induced by (nu _R) and from the one-loop scotogenic contribution accommodated by potential dark matter candidates, (N_R) and dark scalars, odd under the matter parity. We examine new physics phenomena related to the additional gauge boson, which could be observed at colliders. We analyze the constraints imposed on our model by current experimental limits on neutrino masses, neutral meson oscillations, B-meson decays, and charged lepton flavor violating processes. We also investigate the potential dark matter candidates by considering relic density and direct detection.

In this work, we investigate the weak decays of ground-state triply heavy baryons. We first obtain the form factors using the light-front quark model in the three-quark picture, and then apply them to arrive at some phenomenological predictions, including the decay widths of semileptonic decays and nonleptonic decays. Our results are expected to be helpful for the experimental search for triply heavy baryons.

Unlike those in the nonmagnetized counterpart, equatorial photon effective potentials outside the horizons allow for the existence of closed pockets or potential wells corresponding to local minimum values in a magnetized Kerr–Newman spacetime of Gibbons et al. There are three bound photon orbits, which neither fall into the black hole nor escape to infinity. They are stable circular orbits, bound quasiperiodic orbits and bound chaotic orbits. The stable circular photon orbits and bound quasiperiodic photon orbits are allowed on and outside the equatorial plane, but the bound chaotic photon orbits are only allowed outside the equatorial plane. On the other hand, the photon effective potentials have potential barriers with local maximum values in the magnetized case, similar to those in the nonmagnetized case. This fact means the existence of three other photon orbits, which include the photons falling to the center, scattering to infinity and unstably circling in the center. They are not necessarily restricted to the equatorial plane, either. The six types of photon orbits are confirmed numerically via an explicit symplectic integrator and the techniques of fast Lyapunov indicators and 0–1 test correlation method. In particular, a number of bound quasiperiodic photon orbits and bound chaotic photon orbits are found. The method for finding these six types of photon orbits in the phase space will also be used as a new ray-tracing method to find the corresponding six regions on the observer’s plane and to obtain black hole shadows.

We analyze the dynamics of Dirac fermions in graphene set within Beltrami spacetime, characterized by a negative curvature. This research investigates how both curvature and external electromagnetic fields influence electron motion, particularly in terms of Landau level quantization and the quantum Hall effect. By utilizing Darboux transformations, we construct novel solvable potentials along with their associated solutions. Furthermore, we assess the role of ({mathcal {CPT}}) symmetry in shaping the Hamiltonian and derive the metric operator (eta ) within the framework of pseudo-Hermitian quantum mechanics. This study sheds light on the intricate relationship between curvature, symmetry, and quantum behavior in graphene-based systems. We have tested our results using numerical calculations.

In this paper we examine the relativistic Einstein rings assuming a nonminimal coupling between gravitation and electromagnetism in a Reissner–Norström background. Starting from a general action of a nonminimal coupled electrodynamics we show that an unstable effective photon sphere may be obtained in the regime of eikonal approximation. Restricting ourselves to the unstable photon sphere domain we examine the expected angular positions of the first and second relativistic Einstein rings. To compare our results with previous studies in the literature we model the lens as a Galactic supermassive black hole. For fixed coupling parameters we show that such angular positions decrease as the charge parameter increases. The angular separation between the first and second rings is also evaluated. We show that such separation increases as the charge parameter increases. These patterns are not followed by nearly extremal configurations. In this case we show that there is an overlap domain so that the angular position and the corresponding coupling parameter do not allow one to differ extremal cases from complementary configurations which satisfy the cosmic censorship hypothesis.

The unique experimental connection to the QCD energy–momentum tensor offered by generalised parton distributions has been strongly highlighted in the past few years with attempts to extract the pressure and shear forces distributions within the nucleon. If, in principle, this can be performed in a model independent way from experimental data, in practice, the current limited precision and kinematic coverage make such an extraction very challenging. Moreover, the limitation to a leading-order description in the strong coupling of the data has provided only an indirect and weakly sensitive access to gluon degrees of freedom, solely through their mixing to quarks via evolution. In this paper we address this issue by providing a next-to-leading order formalism allowing a reanalysis of global fits with genuine gluonic degrees of freedom. In addition, we provide an estimate of the reduction in uncertainty that could stem from the extended kinematic range relevant for the future Electron Ion Collider. Finally, we stress the connection between the analysis of the dispersion relation in terms of generalised parton distributions and the deconvolution problem.