Speaker
Description
Suggestions of a late-time phantom crossing from DESI baryon acoustic oscillation measurements combined with cosmic microwave background and Type-Ia supernova observations have renewed interest in dynamical dark energy. We present a realization of low-redshift phantom crossing based on fermion condensation and general relativity. The mechanism arises from the interplay between a curvature-triggered fermion-condensate transition and geometric backreaction from nonlinear structure formation. The resulting cosmological evolution remains close to $\Lambda$CDM until low redshift, subsequently undergoing a smooth phantom crossing without fundamental ghost fields or modified gravity. Projecting the predicted evolution onto the CPL parametrization yields values compatible with DESI+CMB+SNIa reconstructions. For the benchmark backreaction density parameter $\Omega_{\rm BR0}= 0.0572$, we obtain $z_*\simeq0.35$, $w_0\simeq-0.76$, and $w_a\simeq-0.93$.