International Journal of Modern Physics A

We emulate Cabibbo by assuming a kind of universality for fermion mass terms in the Standard Model. We show that this is consistent with all current data and with the concept that deviations from what we term Higgs’ universality are due to corrections from currently unknown physics of nonetheless conventional form. The application to quarks is straightforward, while the application to leptons makes use of the recognition that Dark Matter can provide the “sterile” neutrinos needed for the seesaw mechanism. Requiring agreement with neutrino oscillation results leads to the prediction that the mass eigenstates of the sterile neutrinos are separated by quadratically larger ratios than for the charged fermions. Using consistency with the global fit to LSND-like, short-baseline oscillations to determine the scale of the lowest mass sterile neutrino strongly suggests that the recently observed astrophysical 3.55 keV $\gamma$-ray line is also consistent with the mass expected for the second most massive sterile neutrino in our analysis.

In light of the latest neutrino data, we revisit a minimal seesaw model with the Frampton–Glashow–Yanagida ansatz. Renormalization-group running effects on neutrino masses and flavor mixing parameters are discussed and found to essentially have no impact on testing such a minimal scenario in low-energy neutrino experiments. However, since renormalization-group running can modify neutrino mixing parameters at high energies, it does affect the leptogenesis mechanism, which is responsible for the observed matter–antimatter asymmetry in our Universe. Furthermore, to ease the conflict between the naturalness argument and the successful leptogenesis, a special regime for resonant leptogenesis is also emphasized.

Within the Standard Model, using the facility of making Weak Basis transformations, attempt has been made to examine the most general mass matrices within the texture zero approach. For the case of quarks, interestingly, one finds a particular set of texture four zero quark mass matrices emerging out to be a unique viable option for the description of quark mixing data as well as for accommodation of CP violation. Similarly, general lepton mass matrices, essentially considered as texture zero mass matrices, yield interesting bounds on the CP violating Jarlskog’s rephasing invariant parameter in the leptonic sector.

We show how semiclassical black holes can be reinterpreted as an effective geometry, composed of a large ensemble of horizonless naked singularities (eventually smoothed at the Planck scale). We call these new items frizzy-balls, which can be rigorously defined by Euclidean path integral approach. This leads to interesting implications about information paradoxes. We demonstrate that infalling information will chaotically propagate inside this system before going to the full quantum gravity regime (Planck scale).

We study the cascade of Hawking emission spectrum from the event horizon in the presence of one loop backreaction effect in a black hole background. The space–time taken here is the modified Schwarzschild one. The analysis shows that it is possible to decrease the sparsity with the decrease in black hole mass. Moreover, at some particular value of mass, one has a continuous radiation cascade. This result is completely new and quite different from the usual one. An estimation of the mass for continuous one is also found. We see that the value is of the Planck mass order. In this process, it is observed that under a physical background, below a particular value of the mass, the Hawking radiation must stop and we have a remnant. This was absent in the earlier analysis.

A formulation of the linear $\sigma$ model with derivative interactions is studied. The classical theory is on-shell equivalent to the $\sigma$ model with the standard quartic Higgs potential. The mass of the scalar mode only appears in the quadratic part and not in the interaction vertices, unlike in the ordinary formulation of the theory. Renormalization of the model is discussed. A nonpower-counting renormalizable extension, obeying the defining functional identities of the theory, is presented. This extension is physically equivalent to the tree-level inclusion of a dimension-six effective operator ${\partial }_{\mu }({\mathrm{\Phi }}^{†}\mathrm{\Phi }){\partial }^{\mu }({\mathrm{\Phi }}^{†}\mathrm{\Phi })$. The resulting UV divergences are arranged in a perturbation series around the power-counting renormalizable theory. The application of the formalism to the Standard Model in the presence of the dimension-six operator ${\partial }_{\mu }({\mathrm{\Phi }}^{†}\mathrm{\Phi }){\partial }^{\mu }({\mathrm{\Phi }}^{†}\mathrm{\Phi })$ is discussed.

We show that higher-derivative q-theory in the four-form-field-strength realization does not suffer from the Ostrogradsky instability at the classical level.

We study the effects of asymmetry in the entanglement thermodynamics of CFT subsystems. It is found that “boosted” Dp-brane backgrounds give rise to the first law of the entanglement thermodynamics where the CFT pressure asymmetry plays a decisive role in the entanglement. Two different strip like subsystems, one parallel to the boost and the other perpendicular, are studied in the perturbative regime $T_{\mathrm{\text{thermal}}}\ll T_E$. We mainly seek to quantify this entanglement asymmetry as a ratio of the first-order entanglement entropies of the excitations. We discuss the AdS-wave backgrounds at zero temperature having maximum asymmetry from where a bound on entanglement asymmetry is obtained. The entanglement asymmetry reduces as we switch on finite temperature in the CFT while it is maximum at zero temperature.

The theory of free Majorana–Weyl spinors is the prototype of conformal field theory in two dimensions in which the gravitational anomaly and the Weyl anomaly obstruct extending the flat space–time results to curved backgrounds. In this paper, we investigate a quantization scheme in which the short distance singularity in the two-point function of chiral fermions on a two-dimensional curved space–time is given by the Green’s function corresponding to the classical field equation. We compute the singular term in the Green’s function explicitly and observe that the short distance limit is not well-defined in general. We identify constraints on the geometry which are necessary to resolve this problem. On such special backgrounds, the theory has locally $c=\frac{1}{2}$ conformal symmetry.

We build a supersymmetric version with $SU{(3)}_C\otimes SU{(2)}_L\otimes U{(1)}_{Y^{\prime }}\otimes U{(1)}_{B-L}$ gauge symmetry, where $Y^{\prime }$ is a new charge and $B$ and $L$ are the usual baryonic and leptonic numbers. The model has three right-handed neutrinos with identical $B-L$ charges, and can accommodate all fermion masses at the tree level. In particular, the type I seesaw mechanism is implemented for the generation of the active neutrino masses. We obtain the mass spectra of all sectors and for the scalar one we also give the flat directions allowed by the model.

The Galilean covariance, formulated in 5-dimensions space, describes the nonrelativistic physics in a way similar to a Lorentz covariant quantum field theory being considered for relativistic physics. Using a nonrelativistic approach the Stefan–Boltzmann law and the Casimir effect at finite temperature for a particle with spin zero and 1/2 are calculated. The thermo field dynamics is used to include the finite temperature effects.

We perform a comparison of the impact of different intrinsic charm (IC) models, based on the prediction of the differential cross-sections of $Z$-boson and $c$-jet production in $pp$ collision. It is shown that regardless of choosing the model, considering nonperturbative intrinsic charm component increases the magnitude of the cross-section when the $Z$ transverse momentum grows or at large rapidity $(y)$ of the $Z$. Moreover, to evaluate the effect of different parton distribution functions (PDFs), we also compare the results of two PDF sets in prediction of production $Z+c$-jet in $pp$ at a center-of-mass energy of 13 TeV with taking into account the intrinsic charm contribution in the proton. It is shown that the various PDF sets give some difference in the description of the $Z+c$-jet cross-section.