Dynamical stability and observational constraints on a late-time dark-matter particle-creation model

Abstract

We investigate the cosmological dynamics of gravitational particle creation in a spatially flat FLRW Universe comprising radiation, baryons, dark matter (DM), and a separately conserved dark-energy component. The DM sector is described as an effective open thermodynamic fluid incorporating intrinsic pressure and particle-creation-induced negative pressure. Introducing the compact variable $u=H_0/(H_0+H)$, we construct a four-dimensional autonomous system and systematically investigate its critical points, dynamical stability, and physical admissibility. The model is constrained using three observational combinations: PPS+BAO+OHD, Union3+BAO+OHD, and DES-DOV+BAO+OHD. The observationally preferred parameter regions exclude the nontrivial DM-dominated de Sitter-like branches from the physical phase space, while identifying a stable, physically admissible, dark-energy-dominated accelerating attractor. The reconstructed cosmological evolution consistently reproduces the radiation--matter--acceleration sequence, with a transition redshift $z_{\rm tr}\simeq0.71$--$0.73$. Posterior-level analysis reveals that approximately $92\%$--$97\%$ of the samples support this accelerating attractor. The asymptotic evolution approaches a quintessence-like power-law expansion with $H\rightarrow0$, rather than a de Sitter state. These findings establish a connection between observational constraints, gravitational particle creation, and the global dynamical structure governing the distant cosmic future.