Cachar College

We investigate the connection between resonant leptogenesis and a primordial stochastic gravitational-wave background in a minimal two-right-handed-neutrino type-I seesaw with a real singlet scalar. The scalar sector admits a ℤ_2-symmetric tree-level potential, while the tiny right-handed-neutrino coupling to the ℤ_2-odd scalar generates a radiative vacuum-energy bias that causes the domain-wall network to annihilate. For quasi-degenerate heavy neutrinos, we describe the heavy-neutrino system with a density-matrix kinetic framework and use the ratio r_q=ΔM/Γ_N_1 as an organizing variable for the separated, resonant and coherent regimes. The heavy-neutrino parameters that control the physical mass splitting also enter the radiatively generated domain-wall bias, providing a model-dependent link between the quantum-kinetic baryon asymmetry and the gravitational-wave peak frequency and amplitude. We emphasize that the gravitational- wave signal is not a direct measurement of an individual low-energy neutrino parameter; rather, it provides a model-dependent consistency relation among neutrino data, resonant leptogenesis, domain-wall annihilation and the stochastic gravitational-wave background.

We present a theoretical model to investigate the nonlinear behavior of gravito-electrostatic fluctuations in an unmagnetized self-gravitating visco-elastic dusty plasma of infinite extension. It is composed of five distinct species: nonthermal lighter (inertialess) components–electrons, positive ions, and negative ions–and thermal heavier (inertial) components–neutral and charged dust grains. Applying nonlinear normal mode analysis, we derive a unique pair of extended Korteweg–de Vries–Burgers (KdV–B) equations that describe the hybridized dynamics of coupled gravito-electrostatic potential fluctuations. A judicious numerical platform is constructed to understand the exact nature of the fluctuation dynamics. It is reviewed that the KdV-B system manifests as electrostatic narrow solitary spectral patterns and the corresponding self-gravitational broad counterparts. The steady-state nature of the fluctuation dynamics is found to be sensitively dependent on diverse plasma parameters. Astronomical applicability of the investigated results in light of current observational missions is finally outlined.

We investigate the phase structure and gravitational-wave (GW) phenomenology of a cosmological first-order phase transition described by the finite-temperature effective potential V(ϕ,T)=D(T^2-T_0^2)ϕ^2-ETϕ^3+λϕ^4/4. We derive the critical temperature and the broken-phase order parameter and identify the dimensionless combination E^2/(Dλ) that controls the critical-temperature shift. We then construct a dense numerical atlas containing 30 000 parameter points and map the resulting transition parameters onto the characteristic GW frequency and peak amplitude. The scan resolves the multidimensional correlations among T_*, α, β/H_*, v_w, f_ peak and Ω_ GW^ peakh^2. The present analysis is phenomenological: T_* is defined by the prescription T_*=0.95T_c, while β/H_* and v_w are treated as scan inputs. Consequently, the resulting GW signals are not interpreted as first-principles predictions. We identify the additional ingredients required for a predictive calculation, including the thermal bounce action, nucleation and percolation temperatures, the transition duration and a microscopic treatment of bubble-wall friction. The resulting framework provides a systematic numerical characterization of the connection between the phase structure of the finite-temperature potential and the corresponding phenomenological GW parameter space.

We investigate neutrino flavor evolution in strong gravitational fields within an open-quantum-system framework in curved spacetime. Starting from the Dirac equation in the vierbein formalism, we construct an effective flavor Hamiltonian incorporating gravitational redshift, spin–curvature couplings, and Kerr frame-dragging effects. Treating spin-connection fluctuations as a stochastic gravitational environment, we derive a Lindblad master equation and introduce a curvature-enhanced decoherence rate governed by local spacetime geometry. We compute oscillation probabilities, coherence loss, flavor-ratio distortions, entanglement entropy generation, and event-rate modifications for neutrinos propagating near Schwarzschild and Kerr compact objects. The resulting signatures are compared with projected sensitivities of IceCube-Gen2, KM3NeT, and P-ONE, and are further quantified through detector-level significance estimates. Our results provide a unified effective framework linking neutrino oscillations, gravitationally induced decoherence, quantum-information observables, and high-energy astrophysical neutrino measurements in strong-curvature environments.

We present a predictive framework for neutrino mass generation based on the spontaneous breaking of a leptonic U(1)_L_μ-L_τ symmetry within a supersymmetric setting. The breaking of the global symmetry gives rise to a Majoron-like axion-like particle and a pseudo-Goldstone right-handed neutrino whose mass is naturally suppressed by supersymmetry-breaking effects. The interplay between the pseudo-Goldstone neutrino and the low-scale seesaw mechanism leads to a structured neutrino mass matrix capable of reproducing the observed neutrino masses, mixing angles, and CP-violating phase without invoking extreme parameter hierarchies. We perform a numerical fit to current neutrino oscillation data and identify representative benchmark solutions consistent with laboratory constraints as well as cosmological and astrophysical bounds. A characteristic outcome of the framework is the emergence of correlated relations linking the symmetry breaking scale, heavy neutrino masses, Majoron couplings, and neutrino lifetimes. Majoron-induced invisible neutrino decay arises generically and can significantly modify cosmological neutrino mass constraints for sufficiently low symmetry breaking scales. We discuss the phenomenological implications across neutrino oscillation experiments, cosmology, and collider searches for long-lived heavy neutrinos. While a detailed experimental simulation is beyond the scope of this work, existing sensitivity projections indicate that portions of the parameter space may become accessible in future facilities. The combined interplay of laboratory probes and cosmological observations provides a consistent and testable picture of neutrino mass generation tied to spontaneous leptonic symmetry breaking and axion-like physics.