2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199211We construct a class of scalar field models coupled to matter that lead to the dependence of masses and coupling constants on the ambient matter density. Such models predict a deviation of couplings measured on the Earth from values determined in low-density astrophysical environments, but do not necessarily require the evolution of coupling constants with the redshift in the recent cosmological past. Additional laboratory and astrophysical tests of Δαand Δ(m_p/m_e) as functions of the ambient matter density are warranted.20 pages, no figures, references added, minor editorial changesHigh Energy Physics - Phenomenologytext