Mimicking dark matter through a non-minimal gravitational coupling with matter

Abstract

In this study one resorts to the phenomenology of models endowed with a non-minimal coupling between matter and geometry, in order to develop a mechanism through which dynamics similar to that due to the presence of dark matter is generated. As a first attempt, one tries to account for the flattening of the galaxy rotation curves as an effect of the non-(covariant) conservation of the energy-momentum tensor of visible matter. Afterwards, one assumes instead that this non-minimal coupling modifies the scalar curvature in a way that can be interpreted as a dark matter component (albeit with negative pressure). It is concluded that it is possible to mimic known dark matter density profiles through an appropriate power-law coupling f 2 = (R/R 0 ) n , with a negative index n -a fact that reflects the dominance of dark matter at large distances. The properties of the model are extensively discussed, and possible cosmological implications are addressed.

Wormhole geometries supported by a nonminimal curvature-matter coupling

“…[23]. Analogous nonlinear gravitational couplings with a matter Lagrangian were also considered in the context of proposals to address the cosmic accelerated expansion [24], dark matter [25], in the analysis of the cosmological constant problem [26], the curvature-matter coupling viability has been analyzed from the point of view of the energy conditions and of their stability under the DolgovKawasaki criterion [27], and matter density perturbations were analyzed to constrain the curvature-matter coupling theory from growth factor and weak lensing observations [28]. In [29], modified gravity with a nonminimal curvature-matter coupling in the Palatini formulation was considered, and in [30], the f (R) type gravity models was generalized by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the matter Lagrangian L m .…”

Mimicking the cosmological constant: Constant curvature spherical solutions in a nonminimally coupled model

“…Taking n = −1, dark matter constraints require that R −1 ∼ (10 Gpc) −2 [20]. Thus, one obtains from Eq.…”

“…This possibility can have deep phenomenological implications: in particular, it would imply that regions with high curvature (which, in GR, are related to regions of high energy density or pressure) could lead to considera ble deviations from the dynamics predicted by Einstein's theory [17]. A wide range of results has arisen from this hypothesis, including the formal equivalence with a multi-scalar-tensor theory [18], the impact on solar observables [19], the possibility to account for dark matter [20], post-inflationary reheating [21] or the current accelerated expansion of the universe [22].…”

Wormholes and Time-Machines in Nonminimally Coupled Matter-Curvature Theories of Gravity

“…Moreover, these models allow for the mimicking of dark matter profiles in galaxies [10] and clusters of galaxies [11], as well as of dark energy at cosmological scales [12]. It was also shown that one can obtain somewhat more natural conditions for preheating in inflationary models [13] and that the coupling between curvature and matter is equivalent, under conditions, to an effective pressure which leads, in the weak field limit, to a generalized Newtonian potential [14].…”