Modern Physics Letters A

We consider backreacted $Ad{S}_5\times S^5$ coupled with $N_f$ massive flavors introduced by D7 branes. The backreacted geometry is in the Veneziano limit with fixed $N_f/N_c$. By dividing one of the directions into a line segment with length l, we get two subspaces. Then we calculate the entanglement entropy between them. With the method of [I. R. Klebanov, D. Kutasov and A. Murugan, Nucl. Phys. B 796, 274 (2008)], we are able to find the cut-off independent part of the entanglement entropy and finally find that this geometry shows no confinement/deconfinement phase transition at zero temperature from the holographic entanglement entropy point of view similar to the case in pure $Ad{S}_5\times S^5$.

Recently, electron vortices have attracted attention both experimentally and theoretically. A study on the Landau–Dirac problem is made to understand the nature of electron vortices. This line of investigation is motivated by the recent literature on the Landau problem that throws new insights on the nature of orbital angular momentum, i.e. canonical versus kinetic in the context of QCD. The significance of pure gauge vector potential, nontrivial topology and exchange of modular orbital angular momentum to understand the physical origin of electron vortices in the Landau–Dirac problem are new contributions of this paper.

In this paper, we study the influence of the noncommutativity on the pairs creation of neutral particle–antiparticle in (1 + 2)d. Using the Seiberg–Witten maps, the modified Euler–Lagrange field equations up to first-order in the noncommutativity, parameter $𝜃$ is obtained and the Nikishov method based on Bogoliubov transformation is applied to calculate the density number of created neutral fermions. It is shown that the noncommutativity amplifies the density number N. In addition, when $𝜃=0$, we obtain the known results corresponding to the undeformed quantum fields.

There are many inflationary models compatible with observational data. One can investigate inflationary models by looking at their general features, which are common in most of the models. Here we have investigated some of the single-field models without considering their origin in order to find the phenomenology of them. We have shown how to adjust the simple harmonic oscillator model in order to be in good agreement with observational data.

The contributions of the vector leptoquarks of Pati–Salam type to the branching ratios of $K_L^0,B^0,B_s\to l{l}^{\prime }$ decays are calculated with account of the fermion mixing in the leptoquark currents of the general type. Using the general parametrizations of the mixing matrices the lower vector leptoquark mass limit $m_V$ $>$ 86 TeV is found from the current experimental data on these decays. The branching ratios of the decays $B^0,B_s\to l{l}^{\prime }$ predicted at $m_V$ = 86 TeV are calculated. These branching ratios for the decays $B^0,B_s\to {\mu }^{+}{\mu }^{-},e\mu$ are close to the experimental data whereas those for the decays $B^0\to e^{+}{e}^{-},e\tau ,\mu \tau$ and $B_s\to e^{+}{e}^{-}$ are by order of 2–4 less than their current experimental limits. For the decays $B_s\to e\tau ,\mu \tau$ these branching ratios are of orders $10^{-10}$ and $10^{-9}$, respectively. The predicted branching ratios will be useful in the current and future experimental searches for these decays.

A fully gauge-invariant topological coupling of torsion to the electromagnetic field is examined. It is shown, while the gravitational fields are unaltered, torsion may serve as a source for electromagnetism and electromagnetism may serve as a source for torsion. Unlike most couplings, this gives rise to conservation of charge, no magnetic monopoles, and is in agreement with the principle of equivalence.

The well-known leptonic U(1) symmetry of the Standard Model (SM) of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter (DM), as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider.