Modern Physics Letters A

The present work attempts to provide an overview of texture specific lepton mass matrices. In particular, we summarize the findings of some recent analyses carried out within non-flavor basis, wherein a parallel texture structure for the lepton and neutrino mass matrices is considered.

In this paper, we have tried to explore the twin paradox in the ellipsoidal coordinate system. We have investigated that the traveling twin travels away from the gravitational source in the first case while in the other it moves towards the source. We then tried to compare it with the special relativistic case where the static twin ages faster as compared to his traveling counterpart.

The direct coupling between the Higgs field and the spacetime curvature, if finely tuned, is known to stabilize the Higgs boson mass. The fine-tuning is soft because the Standard Model (SM) parameters are subject to no fine-tuning thanks to their independence from the Higgs-curvature coupling. This soft fine-tuning leaves behind a large vacuum energy $\propto {\Lambda }_{\mathrm{\text{UV}}}^4$ which inflates the Universe with a Hubble rate $\propto {\Lambda }_{\mathrm{\text{UV}}}$, ${\Lambda }_{\mathrm{\text{UV}}}$ being the SM ultraviolet (UV) boundary. This means that the tensor-to-scalar ratio inferred from cosmic microwave background polarization measurements by BICEP2, Planck and others lead to the determination of ${\Lambda }_{\mathrm{\text{UV}}}$. The exit from the inflationary phase, as usual, is accomplished via decays of the vacuum energy. Here, we show that, identification of ${\Lambda }_{\mathrm{\text{UV}}}$ with the inflaton, as a sliding UV scale upon the SM, respects the soft fine-tuning constraint and does not disrupt the stability of the SM Higgs boson.

In this paper, we study a general holographic conductor/superconductor model with Stückelberg mechanism in the four-dimensional AdS back hole background without backreaction. We try to disclose properties of the phase transitions through condensations of the scalar operators. We find that the model parameters can determine the order of phase transitions and the new model provide richer physics in the phase transition diagram.

Solutions are found to field equations constructed from the Pauli, Bach and Gauss–Bonnet quadratic tensors to the Kasner and Kasner brane spacetimes in up to five dimensions. A double Kasner space is shown to have a vacuum solution. Brane solutions in which the bulk components of the Einstein tensor vanish are also looked at and for four-branes a solution similar to radiation Robertson–Walker spacetime is found. Matter trapping of a test scalar field and a test perfect fluid are investigated using energy conditions.

We give a simple example of spacetime metric, illustrating that homogeneity and isotropy of space slices at all moments of time is not obligatory lifted to a full system of six Killing vector fields in spacetime, thus it cannot be interpreted as a symmetry of a four-dimensional metric. The metric depends on two arbitrary and independent functions of time. One of these functions is the usual scale factor. The second function cannot be removed by coordinate transformations. We prove that it must be equal to zero, if the metric satisfies Einstein’s equations and the matter energy–momentum tensor is homogeneous and isotropic. A new, equivalent, definition of homogeneous and isotropic spacetime is given.

We compute the quantum gravitational contributions to the Standard Model (SM) effective potential and analyze their effects on the Higgs vacuum stability in the framework of effective field theory. Einstein gravity necessarily implies the existence of higher dimension ${\varphi }^6$ and ${\varphi }^8$ operators with novel couplings ${\eta }_{1/2}$ in the Higgs sector. The beta functions of these couplings are established and the impact of the gravity induced contributions on electroweak vacuum stability is studied. We find that the true minimum of the SM effective potential now lies below the Planck scale for almost the entire parameter space $({\eta }_{1/2}(m_{\mathrm{\text{t}}})>0.01)$. In addition quantum gravity is shown to contribute to the minimal value of the SM next-to-leading order (NLO) effective potential at the percent level. The quantum gravity induced contributions yield a metastable vacuum for a large fraction of the parameter space in the flowing couplings ${\eta }_{1/2}$.