Modern Physics Letters A

In this paper, we consider topological gauge theories in three dimensions which are defined by metric independent lagrangians. It has been claimed that the functional integration necessarily depends nontrivially on the gauge-fixing metric. We demonstrate that the partition function and the mean values of the gauge invariant observables do not really depend on the gauge-fixing metric.

The pion and kaon properties in a nuclear medium at nonvanishing temperature as well as the quantum chromodynamics (QCD) chiral condensate in the presence of a magnetic field for various baryon densities are studied in the Nambu–Jona–Lasinio (NJL) model with the help of the proper-time regularization (PTR) scheme, simulating a QCD confinement. The density dependence of the quark mass in symmetric nuclear matter is obtained from the quark-meson coupling (QMC) model, which shares the same covariant feature with the NJL model, at quark level. We then analyze the QCD chiral condensates and dynamical masses for various baryon densities at finite temperature and magnetic field as well as the pion and kaon masses, pion and kaon weak-decay constants, pion- and kaon-quark coupling constants, and wave function renormalization factors for various baryon densities at finite temperature. We find that the QCD chiral condensates suppress with increasing temperature and baryon density and enhance under the presence of a magnetic field, which are consistent with other model predictions. Interestingly, the wave function renormalization factors for the pion and kaon increase with respect to temperature and reduce as the baryon density increases are found.

In this paper, we discuss diagonalization of propagator for system of mixing fermions on the base of the eigenvalue problem. The similarity transformation converting matrix propagator into the diagonal form is obtained, which is a necessary element at renormalization of fermion mixing matrix. The suggested diagonalization has simple algebraic properties for on-mass-shell fermions.

We apply the Batalin–Fradkin–Fradkina–Tyutin formalism to a prototypical second-class system, aiming to convert its constraints from second class to first class. The proposed system admits a consistent initial set of second-class constraints and an open potential function providing room for feasible applications to field theory and mechanical models. The constraints can be arbitrarily nonlinear, broadly generalizing previously known cases. We obtain a sufficient condition for which a simple closed expression for the Abelian converted constraints and modified involutive Hamiltonian can be achieved. As an explicit example, we discuss a spontaneous Lorentz symmetry breaking vectorial model, obtaining the full first-class Abelianized constraints in closed form and the corresponding involutive Hamiltonian.

In this paper, we construct a new charged AdS black hole with modified cosmic Chaplygin gas (MCCG). In comparison to the previous model (modified Chaplygin AdS black hole) that existed in the literature, we now have two new parameters: the cosmic parameter and the black hole’s electric charge. We examine the asymptotically charged AdS black hole thermodynamics with MCCG under the assumption of a negative cosmological constant as a thermodynamics pressure. Using MCCG, we developed a new solution to Einstein’s AdS black hole field equations. The mass parameter, volume, electric potential, entropy, and temperature of the charged AdS black hole have all been computed. We also study the various energy conditions for the MCCG as a source fluid of AdS black hole. For some restrictions on the involved parameters, we show that these conditions are met. Then, we study the thermodynamical stability, critical points, and Joule-Thompson expansion for the back hole obtained. We reveal that while the existence of cosmic parameter yields to a complete stable mode, its absence gives rise to some unstable regions. Then, using MCCG, we treat the obtained black hole’s thermodynamics as a heat engine and calculate the work done as well as the heat engine’s maximum efficiency in the Carnot cycle. The work done, the efficiency, and the Rankine cycle’s efficiency are also investigated. All of the findings are graphically depicted and discussed.

This paper explores a new embedding anisotropic charged version of a solution to Einstein–Maxwell field equations in four-dimensional spacetime through the Karmarkar conditions and the gravitational decoupling via minimal geometric decoupling (MGD) technique by choosing Pant’s interior solution [Astrophys. Space Sci. 331, 633 (2011)] as a seed solution to coupled system. Later, we integrate the coupled system within the MGD and explore a family of solutions to represent the realistic structure of nonrotating compact objects. Through the matching of the interior solutions so obtained to the exterior Reissner–Nordström metric, we tune the arbitrary constants for feasible models. After that, we subject our model to a rigorous test for a chosen parameter space to verify the physical viability of the solution for the neutron stars in EXO 1785-248 for a range of values of the decoupling constant $\sigma$. Further, we prove that the constant $\sigma$ is inherently connected to critical physical properties such as the gravitational and surface redshifts, compactification factor, mass/radius relation, etc., of the same compact star candidate EXO 1785-248. The solutions thus obtained exhibit physically viable features which are thoroughly demonstrated through graphical plots.

In this paper, we present some wormhole configurations using analytic and numerical solutions of the Euclidean field equations considering Einstein–Gauss–Bonnet dilaton coupled interaction in the Robertson–Walker metric. Analytic solutions invoking slow-roll type approximation for some potentials yield identical wormholes in the early era. Eventually, in later era, the universe enters to an expanding era much faster than usual inflation accompanied by oscillations with analytic continuation $\tau =it$. The numerical solutions of wormholes in terms of the scale factor $a(\tau )$ are almost identical for some standard potentials of the dilaton field, except for the evolution of potentials. The Hubble parameter and deceleration parameter obtained by curve fit of $a(\tau )$ of the numerical solution of wormhole yield an inflationary era away from the throat of the wormhole using $\tau =it$. A sharp decay of the potential is also observed.