[JC] Primordial Neutron Stars

by Sougata Ganguly

Thursday 25 Jun 2026, 15:00 → 16:00 Asia/Seoul

CTPU seminar room (IBS)

In this talk, I will discuss the recent paper arXiv: 2604.08651, where the authors investigate a plausible mechanism for the formation of primordial neutron stars in the early universe, prior to big bang nucleosynthesis.

 

Authors: Gordan Krnjaic, Duncan Rocha, and Huangyu Xiao

 

Abstract of the paper: We propose a novel cosmological scenario in which baryonic neutron stars could plausibly form in the early universe. If baryogenesis initially produces an excessively large baryon asymmetry, Y_B \gg 1E-10 , the baryonic mass inside the horizon can exceed the minimum neutron star mass before big bang nucleosynthesis (BBN). While this large asymmetry is present, non-relativistic baryons can dominate the universe, and enhanced density perturbations on small scales can gravitationally collapse Hubble patches shortly after horizon re-entry. For some initial perturbations, just below the threshold for black hole formation, this collapse will be arrested only by nuclear pressure, possibly resulting in neutron star formation. Afterwards, there must be a large entropy injection to restore the observed baryon asymmetry, Y_B ∼ 1E-10, and preserve the successful predictions of standard BBN. Unlike neutron stars that form from stellar collapse, primordial neutron stars can, in principle, be as light as ∼ 0.1 M_\odot, limited only by the nuclear equation of state.