arXiv subjects

Indrajit Ghose

Publications and source records attributed to Indrajit Ghose.

8 recordsLinked to original sources

arXiv2026

Torsional four-fermion interaction for Majorana neutrinos

Fermions generate spacetime torsion, which can be eliminated, leaving behind an effective four-fermion interaction. This term will contribute an effective mass for neutrinos propagating through matter, similar to the Wolfenstein term coming from electroweak interactions. When the neutrinos are Majorana fermions and become massive via the Type I SeeSaw mechanism, there can be additional effects due to sterile neutrinos interacting with all fermions via the torsion-induced term, as well as due to the presence of new mixing parameters. We consider different scenarios with one sterile and one or two active neutrinos -- when the torsional interaction is diagonal in the mass basis and when it is not -- and analytically find these modifications. The T violation in the 2+1 scenario is discussed for some specific mixing between the torsion fields and the mass fields.

hep-ph↗

arXiv2025

Probing Geometrical NSI at the DUNE experiment

In this work, we investigate the implications of a novel non-standard interaction (NSI) of neutrinos. This interaction is geometric in origin -- it arises because the propagation of fermions in curved spacetime induces torsion. This torsion is non-propagating and can be eliminated from the action, resulting in a four-fermion interaction in a torsion-free background. The new interaction modifies the behaviour of the neutrinos passing through matter by introducing additional coupling terms, resulting in a new component in the effective potential. As a result, the neutrino oscillation probabilities in matter are altered. The relevant probabilities are computed using the Cayley-Hamilton formalism. We then numerically explore the potential to probe these torsion-induced NSI in the DUNE experiment. We obtain the bounds on the parameters characterizing the torsional effects. By selecting representative values of torsion parameters to which the DUNE experiment is sensitive, we analyse how these geometric interactions affect the experiment's sensitivity to determine neutrino mass hierarchy, the octant of the 2-3 leptonic mixing angle, and the CP phase. We also examine the new parameter degeneracies introduced by torsion effects and assess their impact on the overall sensitivities of DUNE. We find that the additional parameter degeneracies in the presence of torsion significantly affect the octant sensitivity.

hep-ph↗

arXiv2025

Effects of spacetime geometry on neutrino oscillation inside a Core-Collapse Supernova

Neutrinos are excellent probes of the inner structures of supernovas. However, an understanding of their dynamics remains incomplete, which is crucial for properly interpreting the detector data. The huge matter density inside a core collapse supernova affects the self-coupling of the neutrinos through a geometrical four-fermion interaction induced by spacetime torsion generated by the fermions themselves. For normal mass hierarchy, the effect is negligible; for inverted mass hierarchy however, we find that the gravitational coupling can significantly alter the flavor dynamics. The possibility of constraining the said interactions through the relative abundance of different flavors of the neutrinos is discussed.

astro-ph.HE↗

arXiv2025

Neutrino Oscillation in Core Collapse Supernova: The Impact of Spacetime Geometry

Neutrino flavor evolution inside a core-collapse supernova is a topic of active research. The core of a supernova is an intense source of neutrinos and antineutrinos. Self-interaction among neutrinos (as well as antineutrinos) gives rise to a rich phenomenology not seen in terrestrial situations. In studies of the dynamics of flavor evolution in such environments, the gravitational effects are generally ignored. Although the curvature outside a dense core does not deviate much from a flat space, the spin of the neutrinos can still couple to the torsion of the spacetime. These extra degrees of freedom of curved spacetime have interaction strengths that are proportional to the density of the neutrinos and the other fermions \cite{Chakrabarty:2019cau} \cite{Barick:2023qjq} as well as the coupling constants of the spin-torsion interaction. We have studied the effects of such interactions in flavor evolution inside a core-collapse supernova \cite{Ghose:Manuscript}. The self-interaction gets modified by the spin-torsion interaction and the oscillation dynamics is modified. We have seen that there are noticeable changes in the flavor dynamics when the neutrino density is uniform. We have also studied the effects of such interaction in a realistic core-collapse supernova (CCSN). As neutrino astronomy enters the precision era, this study will shed light on the potential of neutrino fluxes from CCSN to probe the neutrino-neutrino interaction.

astro-ph.HE↗

arXiv2023

Neutrino oscillations induced by chiral torsion

Neutrino mixing is caused by the fact that neutrino flavors are not eigenstates of the free Hamiltonian. This causes oscillations among different neutrino flavors. When neutrinos pass through a medium, weak interactions produce different effective masses for neutrinos of different flavors, leading to a modification of the mixing parameters. In curved spacetime there is an additional contribution to neutrino Hamiltonian from a torsion-induced four-fermion interaction, which also causes neutrino mixing while propagating through fermionic matter. We provide an outline of the calculation of this effect on neutrino oscillation.

hep-ph↗

arXiv2023

Effect of spacetime geometry on neutrino oscillations

Propagation of fermions in spacetime requires a spin connection, which can be split into a universal gravitational part and a non-universal ``contorsion'' part. The latter is non-dynamical and can be eliminated from the theory, leaving an effective four-fermion interaction with unknown coupling constants. The generic form of the contorsion-fermion coupling, and thus the four-fermion interaction, breaks chiral symmetry. This interaction affects all fermions -- in particular neutrinos passing through matter will notice a contribution to their effective Hamiltonian, just like the MSW effect coming from weak interactions, but diagonal in the mass basis rather than the flavor basis. Then there is a possibility that this geometrical contribution is not negligible for neutrinos passing through normal matter, provided the coupling constants are not too small. We calculate the matter potential due to this interaction and thus write the conversion and survival probabilities including its effect. We plot conversion probabilities of $\nu_\mu$ to $\nu_e$ and $\nu_\tau$ for a baseline of 1300 km, as well as their dependence on the CP phase, with and without the geometrical interaction. We also plot the survival probability of reactor $\bar{\nu}_e$ for different baselines.

hep-ph↗

arXiv2023

Neutrino oscillation caused by spacetime geometry

Effects of gravitational interaction are generally neglected in particle physics. A first order formulation of gravity is presented to include gravity in Quantum Mechanical Lagrangian of fermions. It is seen that fermions minimally coupled to gravity gives rise to a torsionless effective theory with a quartic interaction. After passing through a thermal background the most generic form of contortion contributes to neutrino effective mass. This effective mass can change the current oscillation parameters.

hep-ph↗

arXiv2021

The variational method applied to the harmonic oscillator in presence of a delta function potential

The problem of the harmonic oscillator with a centrally located delta function potential can be exactly solved in one dimension where the eigenfunctions are expressed as superpositions of the Hermite polynomials or as confluent hypergeometric functions in general. The eigenfunctions obtained exactly are difficult to visualise and hence to gain more insight, one can attempt using model wave functions which are explicitly and simply expressed. Here we apply the variational method to verify how close one can approach the exact ground state eigenvalues using such trial wave functions. We obtain the estimates of the ground state energies which are closer to the exact values in comparison to earlier approximate results for both the repulsive and attractive delta potentials.

quant-ph↗