Bulk viscous cosmology in curvature-matter coupled f ( R,L m )gravity

We study late-time cosmic acceleration in curvature-matter coupled gravity described by an arbitrary function Formula: see text. We investigate a spatially flat FLRW universe filled with a bulk viscous cosmic fluid, the only dissipative contribution compatible with homogeneity and isotropy. By assuming a dust-like background and adopting the phenomenological ansatz Formula: see text, we focus on the model Formula: see text. For Formula: see text, the cosmological equations admit an analytic solution for the Hubble parameter Formula: see text (for Formula: see text), allowing the reconstruction of key cosmological observables. The free parameters Formula: see text are constrained using independent Formula: see text, Pantheon+SH0ES, and DESI data. We find that Formula: see text is tightly constrained around Formula: see text and satisfies Formula: see text, ensuring positivity of the energy density, while the viscosity coefficient is consistently positive, indicating physically viable entropy production. The model predicts a transition from decelerated to accelerated expansion, with present-day Formula: see text, a quintessence-like effective equation of state Formula: see text, late-time violation of the strong energy condition, and a negative slope of the Formula: see text diagnostic. These results show that bulk viscous Formula: see text gravity presents a viable phenomenological description at the background level, although current BAO data favor Formula: see textCDM.