Abdel Perez-Lorenzana

Neutrino self-interactions (NSI) offer a potential pathway to address anomalies in standard cosmology and explain existing cosmological tensions. In this work, we present a novel framework to obtain the neutrino-neutrino collision term within the Boltzmann hierarchy, incorporating both neutrino and mediator masses as free parameters. Our calculations encompass both Dirac-like and Majorana neutrinos and distinguish between two neutrino mass eigenstates. This work provides a valuable tool for future analyses, should a NSI signal be detected. Remarkably, our results show a smooth transition from the light to the heavy mediator approximation as the Universe cools down for non-resonant cases. Thus, for the widely studied heavy mediator, our new scheme eliminates the need to approximate at high redshifts when the temperature increases above the mediator mass, and it provides the tools to test the threshold of validity of the heavy mediator paradigm. While this work focuses on NSI mediated by a scalar particle, the presented framework could be adapted to a broader range of neutrino NSI and possibly to warm dark matter self-interacting scenarios.

Trace-free Einstein gravity, in the absence of matter fields and using the Friedmann-Robertson-Walker (FRW) metric, is solvable both classically and quantum mechanically. This is achieved by using the conformal time as the time variable and the negative or positive of the inverse of the scale factor as configuration variable to write the classical equation of motion, which turns out to be the one of a free particle ($k=0$), a harmonic oscillator ($k=1$), and a repulsive oscillator ($k=-1$) in the real half-line. In all cases, the observable identified as the cosmological constant is six times the Hamiltonian. In particular, for a closed Universe ($k=1$), spacetime exhibits a cyclic evolution along which the scalar curvature is constant and finite, thereby avoiding singularities. The quantum theory is reached by using canonical quantization. We calculate the spectrum of the observable corresponding to the cosmological constant. Remarkably, for the closed Universe ($k=1$), the spectrum is discrete and positive while for flat ($k=0$) and open ($k=-1$) universes, the spectra are continuous. Heisenberg's uncertainty principle imposes limitations on the simultaneous measurement of the Hubble expansion (momentum variable) and the configuration variable. We also report the observable identified as the cosmological constant for inflaton, phantom and perfect fluids coupled to trace-free Einstein gravity in the FRW metric.

In this letter, after briefly discussing the Hawking radiation (HR) as a quantum tunneling, we emphasize that special care must be taken when computing temperature corrections in the presence of Lorentz invariance violation (LIV), particularly by ensuring consistency between the modified dispersion relation and the gamma matrix structure used to describe fermions that are tunneling. We present a consistent implementation of such corrections in static, spherically symmetric black hole (BH) spacetimes. Our results show that introducing terms that increase/decrease the energy in the dispersion relation--originally determined by Lorentz invariance--leads to a corresponding increase/decrease in the Hawking temperature, when the dispersion relation is uniquely determined. We also determined the changes in Bekenstein-Hawking entropy for the Reissner-Nordström and Schwarzschild BHs, including corrections from LIV scenarios.

Trace-free Einstein gravity, in the absence of matter fields and using the Friedmann–Robertson–Walker (FRW) metric, is solvable both classically and quantum mechanically. This is achieved by using the conformal time as the time variable and the negative or positive of the inverse of the scale factor as configuration variable to write the classical equation of motion, which turns out to be the one of a free particle (k = 0), a harmonic oscillator (k = 1), and a repulsive oscillator ( k = − 1 ) in the real half-line. In all cases, the observable identified as the cosmological constant is six times the Hamiltonian. In particular, for a closed Universe (k = 1), spacetime exhibits a cyclic evolution along which the scalar curvature is constant and finite, thereby avoiding singularities. The quantum theory is reached by using canonical quantization. We calculate the spectrum of the observable corresponding to the cosmological constant. Remarkably, for the closed Universe (k = 1), the spectrum is discrete and positive while for flat (k = 0) and open ( k = − 1 ) universes, the spectra are continuous. Heisenberg’s uncertainty principle imposes limitations on the simultaneous measurement of the Hubble expansion (momentum variable) and the configuration variable. We also report the observable identified as the cosmological constant for inflaton, phantom and perfect fluids coupled to trace-free Einstein gravity in the FRW metric.

In this paper, we review the fundamental aspects of N = 1 supergravity and employ the chiral formalism to describe spin- 3 2 fermions. Armed with this, we analyze the discrete symmetries of the graviton in the context of linearized gravity (LG) and Rarita-Schwinger (RS) fields, which include the description of the gravitino. Additionally, we highlight the advantages of the chiral formalism in classifying Lorentz and C P T -violating terms in RS theories, extending these models by including Lorentz-violating operators, as has been done in LG.