arXiv subjects

Rajrupa Mondal

Publications and source records attributed to Rajrupa Mondal.

3 recordsLinked to original sources

arXiv2026

Putting the Brakes on Axion Strings: Friction and Its Impact on the QCD Axion Abundance

A compelling production mechanism for QCD axion dark matter is from the scaling dynamics of early universe axion strings. We show that in DFSZ-like models containing tree-level interactions between fermions and the axion, friction between the thermal bath and the axion string drastically changes the behavior of the axion string network for lower $f_a$ values. Friction delays the onset of scaling and increases the energy density of axions. Once the effects of friction are included, we argue that in addition to the standard value of $m_a \sim$ meV, $m_a \sim 0.1$ eV also reproduces the dark matter energy density.

hep-ph↗

arXiv2026

Hierarchical constraints on gravitational waves from horizonless compact objects

We use the data of several promising gravitational wave observations to obtain increasingly stringent bounds on near-horizon deviations of their sources from the Kerr geometry. A range of horizonless compact objects proposed as alternatives to black holes of general relativity would possess a modified gravitational wave emission after the merger. Modelling these objects by introducing reflection of gravitational waves near the horizon, we can measure deviations from Kerr in terms of a single additional parameter, the location of the reflection. We quote bounds on deviations for 5 events in addition to previous results obtained for GW150914. Additionally, we improve upon previous results by hierarchically combining information from all analysed events, yielding a bound on deviations of less than $2.5 \times 10^{-26}$ meters above the horizon.

gr-qc↗

arXiv2022

Majorana Neutrinos, Exceptional Jordan Algebra, and Mass Ratios for Charged Fermions

We provide theoretical evidence that the neutrino is a Majorana fermion. This evidence comes from assuming that the standard model and beyond-standard-model physics can be described through division algebras, coupled to a quantum dynamics. We use the division algebras scheme to derive mass ratios for the standard model charged fermions of three generations. The predicted ratios agree well with the observed values if the neutrino is assumed to be Majorana. However, the theoretically calculated ratios completely disagree with known values if the neutrino is taken to be a Dirac particle. Towards the end of the article we discuss prospects for unification of the standard model with gravitation if the assumed symmetry group of the theory is $E_6$, and if it is assumed that space-time is an 8D octonionic space-time, with 4D Minkowski space-time being an emergent approximation. Remarkably, we find evidence that the precursor of classical gravitation, described by the symmetry $SU(3)_{grav} \times SU(2)_R \times U(1)_{grav}$ is the right-handed counterpart of the standard model $SU(3)_{color} \times SU(2)_L \times U(1)_Y$.

hep-ph↗