International Journal of Modern Physics A

The impacts of the light sterile neutrino hypothesis in particle physics and cosmology are reviewed. The observed short baseline neutrino anomalies challenging the standard explanation of neutrino oscillations within the framework of three active neutrinos are addressed. It is shown that they can be interpreted as the experimental hints pointing towards the existence of sterile neutrino at the eV scale. While the electron neutrino appearance and disappearance data are in favor of such a sterile neutrino, the muon disappearance data disfavor it, which gives rise to a strong appearance–disappearance tension. After a brief review on the cosmological effects of light sterile neutrinos, proposed signatures of light sterile neutrinos in the existing cosmological data are discussed. The keV-scale sterile neutrinos as possible dark matter candidates are also discussed by reviewing different mechanisms of how they can be produced in the early Universe and how their properties can be constrained by several cosmological observations. We give an overview of the possibility that keV-scale sterile neutrino can be a good DM candidate and play a key role in achieving low-scale leptogenesis simultaneously by introducing a model where an extra light sterile neutrino is added on top of type I seesaw model.

Using the concept of conformable fractional derivative, we study the properties of fractional $N$-dimensional Schrödinger equation for the potential $V(r)=-\frac{k}{r}+\frac{g}{r^2}+ar+b{r}^2$. The extended Nikiforov–Uvarov method is generalized to the fractional domain and then employed to obtain the analytic exact energy eigenvalues and eigenfunctions and their dependence on the fractional order $\alpha$ and the dimension $N$. To test its applicability, we apply the method on heavy quarkonia systems, and reproduce their mass spectra and fractional radial probabilities at different values of $\alpha$ and $N$. Comparing the mass spectra with the experimental data, we discuss to what extent fractional models can account for some features in the description of heavy quarkonia at certain dimensional space.

The Universe has a gravitational horizon with a radius $R_{\mathrm{\text{h}}}=c/H$ coincident with that of the Hubble sphere. This surface separates null geodesics approaching us from those receding, and as free-falling observers within the Friedmann–Lemaître–Robertson–Walker space–time, we see it retreating at proper speed $c$, giving rise to the eponymously named cosmological model $R_{\mathrm{\text{h}}}=ct$. As of today, this cosmology has passed over 20 observational tests, often better than $\mathrm{\Lambda }$CDM. The gravitational radius $R_{\mathrm{\text{h}}}$ therefore appears to be highly relevant to cosmological theory, and in this paper we begin to explore its impact on fundamental physics. We calculate the binding energy of a mass $m$ within the horizon and demonstrate that it is equal to $m{c}^2$. This energy is stored when the particle is at rest near the observer, transitioning to a purely kinetic form equal to the particle’s escape energy when it approaches $R_{\mathrm{\text{h}}}$. In other words, a particle’s gravitational coupling to that portion of the Universe with which it is causally connected appears to be the origin of rest-mass energy.

In this paper, a relativistic behavior of spin-zero bosons is studied in a chiral cosmic string space–time. The Duffin–Kemmer–Petiau (DKP) equation and DKP oscillator are written in this curved space–time and are solved by using an appropriate ansatz and the Nikiforov–Uvarov method, respectively. The influences of the topology of this space–time on the DKP spinor and energy levels and current density are also discussed in detail.

In this work, one proposes the use of a damped confinement potential to mimic the proton internal energy. The internal pressure is calculated taking into account the occurrence of a phase transition in the $pp$ and $\bar{p}p$ total cross-section. The model predicts the inversion of the positive and negative pressure regions depending on the squared energy $s_0$, where the total cross-section achieves its minimum value. Considering energies below the phase transition, the expected results are in accordance with the recent proton internal pressure measurement. For energies above $s_0$, the model predicts a negative pressure region near the center of the hadron surrounded by a positive pressure region.

In this paper, we discuss the anomaly cancelation condition for the (0,2) sigma model corresponding to the M-strings. We show that slight modification of the usual bundle F used for M-strings, involving tensoring with a power of the line bundle, leads to a bundle which satisfies the anomaly cancelation condition.

We comment on a recent paper published in Phys. Rev. D 98, 094513 (2018), arXiv:1811.09029, pointing out severe problems in the numerical investigation leading to questionable results and misleading conclusions during their interpretation.