Modern Physics Letters A

The similarities in the SU(3) transformation properties of tetraquarks, pentaquarks and sextaquarks are pointed out. Their decays into hadrons with first-order ${\lambda }_8$ SU(3) breaking are considered and corresponding sum rules for decay coupling constants are given.

A simple pocket formula is proposed for mass excess of medium and heavy nuclei ($57<Z<103$). The good agreement of present formula with the experiment and other theoretical values suggests that the present formula could be used to evaluate the mass excess values of medium and heavy nuclei in the region $57<Z<103$. This formula produces mass excess values with the only simple inputs of only $Z$ and $A$.

In this paper, we present new physically viable interior solutions of the Einstein field equations for static and spherically symmetric anisotropic compact stars satisfying the Karmarkar condition. For presenting the exact solutions, we provide a new suitable form of one of the metric potential functions. Obtained solutions satisfy all the physically acceptable properties of realistic fluid spheres and hence solutions are well-behaved and representing matter distributions are in equilibrium state and potentially stable by satisfying the TOV equation and the condition on stability factor, adiabatic indices. We analyze the solutions for two well-known compact stars Vela X-1 (Mass = 1.77 M${}_{\odot }$, R = 9.56 km) and Cen X-3 (Mass = 1.49 M${}_{\odot }$, R = 9.17 km).

The end of inflation is connected to the standard cosmological scenario through reheating. During reheating, the inflaton oscillates around the minimum of the potential and thus decays into the daughter particles that populate the Universe at later times. Using cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time, we translate the constraint on the spectral index $n_s$ from Planck data to the constraint on the reheating scenario in the context of Kähler moduli inflation. We find that the equation of state parameter plays a crucial role in the reheating analysis, however the details of the one parameter potential are irrelevant if the analysis is done strictly within the slow-roll formalism. In addition, we extend the de facto analysis generally done only for the pivot scale to all the observable scales which crossed the Hubble radius during inflation, where we study how the maximum number of e-folds varies for different scales, and the effect of the equation of state and potential parameters.

We present an exact regular solution of Einstein equations for a static and spherically symmetric spacetime with a matter distribution of isotropic perfect fluid. The construction of the solution is realized assigning a regular potential $g_{tt}$ and integrating the isotropic perfect fluid condition for the pressure. The resulting solution is physically acceptable, i.e. the geometry is regular and the hydrostatic variable pressure and density are positive regular monotonic decreasing functions, the speed of the sound is positive and smaller than the speed of the light. An important element of this solution is that its compactness value $u=GM/c^{2}R$ is in the characteristic range of compact stars, which makes a remarkable difference with other models with isotropic perfect fluid, this is $u\in (0,0.3581350065]$ so that we could represent compact stellar objects as neutron stars. In particular, for the maximum compactness of a star with a mass of $1M_{\odot }$ the radius is $R=4122.662003\mathrm{\text{m}}$ and their central density ${\rho }_c=1.799320999\times 10^{19}\frac{\mathrm{\text{Kg}}}{{\mathrm{\text{m}}}^3}$ is characteristic of compact stars.

In this paper, we generalize core–envelope model of superdense star to a noncommutative spacetime and study the modifications due to the existence of a minimal length, predicted by various approaches to quantum gravity. We first derive Einstein’s field equation in $\kappa$-deformed spacetime and use this to set up noncommutative version of core–envelope model describing superdense stars. We derive $\kappa$-deformed law of density variation, valid up to first-order approximation in deformation parameter and obtain radial and tangential pressures in $\kappa$-deformed spacetime. We also derive $\kappa$-deformed strong energy conditions and obtain a bound on the deformation parameter.

Einstein–Hilbert action with a determinantal invariant has been considered. The obtained field equation contains the inverse Ricci tensor, ${\Re }_{\alpha \beta }$. The linearized solution of invariant has been examined, and it is concluded that the constant curvature spacetime metric solution of the field equation gives different curvature constant for each values of $\sigma$. The $\sigma =0$ gives a trivial solution for constant curvature, $R_0$.

In this paper, we consider classical electrodynamic theories with maximal acceleration and some of their phenomenological consequences for laser–plasma acceleration. It is shown that in a recently proposed higher-order jet theory of electrodynamics, the maximal effective acceleration reachable by a consistent bunch of point-charged particles being accelerated by the wakefield is damped for bunches containing large number of charged particles. We argue that such a prediction of the theory is falsifiable. In the case of Born–Infeld kinematics, laser–plasma acceleration phenomenology provides an upper bound for the Born–Infeld parameter b. Improvements in the beam qualities will imply stronger constraints on b.

A left-right symmetric mirror model restoring parity at a high scale in a way such that the mirror fermions and mirror gauge sector simultaneously could exist at TeV scale is discussed. We also provide an ultraviolet completion of the model with vector-like fermions, and discuss some theoretical and phenomenological implications of this model.