ENTER: a new frontier in physics

Black hole (BH) formation via extreme star (ES, mean density comparable to or larger than neutron mean density) instability, due to increasing mass, is conceived as a phase transition from ordinary (energy + matter) to ENTER, an indivisible ideal fluid. BHs and ESs are re-lated to classical, heterogeneous disks of equal mass, equatorial radius, moment of inertia, where surface density distribution obeys a power law, by use of a principle of corresponding states [5]. With regard to static (TOV) and equatorial breackup (EQB) configurations, ES reduced (di-mensionless) parameters are inferred [19] and revised [5] from earlier results, and compared to the following BH relations: (reduced moment of inertia)-(reduced angular momentum); (swivelness, / Ω = β Ω R/c )- (reduced angular momentum); (angular momentum)-mass in logarithmic plane for sequences of configurations where reduced angular momentum remains unchanged. ES (reduced moment of inertia)-compactness relation, inferred in earlier investigations for a large number of equations of state (EOSs) [3][23] and sequences of constant reduced angular momentum [3], is extrapolated across the instability region, 38 < β < 12 , and results are consistent with related BH counterparts, β = 12 . Similarly to BHs, classical heterogeneous disks associated via a principle of corresponding states exhibit surface density distribution increasing with radial distance, contrary to TOV and EQB configurations with assigned EOS, which allows the formulation of an empirical criterion for ES stability.