3 papers
gr-qc2026
Cosmological long-wavelength solutions in non-adiabatic multi-fluid systems
Hayami Iizuka, Tomohiro Harada
We develop a formulation of nonlinear cosmological perturbations on superhorizon scales in multi-fluid systems. It is based on the Arnowitt-Deser-Misner formalism combined with a s…
gr-qc2025
Singularity resolution and regular black hole formation in gravitational collapse in asymptotically safe gravity
Tomohiro Harada, Chiang-Mei Chen, Rituparna Mandal
We adopt an effective action inspired by asymptotically safe gravity, in which the effective gravitational constant is parametrized as $G(ε) = G_{N} /[1 + \tildeÏ (G_{N}^{2} ε)^…
gr-qc2024
Primordial black holes: formation, spin and type II
Tomohiro Harada
Primordial black holes (PBHs) may have formed through the gravitational collapse of cosmological perturbations that were generated and stretched during the inflationary era, later…