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.

A semi-analytical model theory is proposed to investigate the nonlinear pulsational mode dynamics in self-gravitating, turbo-viscous tridust plasmas composed of nonthermal electrons and ions. The approach employs multiple scaling techniques on the governing fluid equations, based on a well-defined hydrostatic, homogeneous equilibrium configuration, to derive a unique pair of extended Korteweg–de Vries (e-KdV) equations. This pair features two distinct sets of multi-parametric coefficients that govern the behavior of gravito-electrostatic (pulsational) fluctuations. A broad spectrum of solitary wave structures is obtained through numerical simulation and systematically analyzed. The study further elucidates the stabilization and destabilization characteristics of these pulsational modes under varying parametric conditions. Finally, the noticeable implications and potential applications of the outcomes in astrostructure formation mechanisms, are briefly highlighted.

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.