We develop and apply new techniques in order to uncover galaxy rotation curves (RC) systematics. Considering that an ideal dark matter (DM) profile should yield RCs that have no bias towards any particular radius, we find that the Burkert DM profile satisfies the test, while the Navarro-Frenk-While (NFW) profile has a tendency of better fitting the region between one and two disc scale lengths than the inner disc scale length region. Our sample indicates that this behaviour happens to more than 75% of the galaxies fitted with an NFW halo. Also, this tendency does not weaken by considering "large" galaxies, for instance those with M * 10 10 M . Besides the tests on the homogeneity of the fits, we also use a sample of 62 galaxies of diverse types to perform tests on the quality of the overall fit of each galaxy, and to search for correlations with stellar mass, gas mass and the disc scale length. In particular, we find that only 13 galaxies are better fitted by the NFW halo; and that even for the galaxies with M * 10 10 M the Burkert profile either fits as good as, or better than, the NFW profile. This result is relevant since different baryonic effects important for the smaller galaxies, like supernova feedback and dynamical friction from baryonic clumps, indicate that at such large stellar masses the NFW profile should be preferred over the Burkert profile. Hence, our results either suggest a new baryonic effect or a change of the dark matter physics.

The differential age data of astrophysical objects that have evolved passivelly during the history of the universe (e.g. red galaxies) allows to test theoretical cosmological models through the predicted Hubble function expressed in terms of the redshift z, H(z). We use the observational data for H(z) to test unified scenarios for dark matter and dark energy. Specifically, we focus our analysis on the Generalized Chaplygin Gas (GCG) and the viscous fluid (VF) models. For the GCG model, it is shown that the unified scenario for dark energy and dark matter requires some priors. For the VF model we obtain estimations for the free parameters that may be compared with further analysis mainly at perturbative level. : 98.80.Cq, 98.80.Bp Pacs

The quantum contributions to the gravitational action are relatively easy to calculate in the higher derivative sector of the theory. However, the applications to the postinflationary cosmology and astrophysics require the corrections to the Einstein-Hilbert action and to the cosmological constant, and those we can not derive yet in a consistent and safe way. At the same time, if we assume that these quantum terms are covariant and that they have relevant magnitude, their functional form can be defined up to a single free parameter, which can be defined on the phenomenological basis. It turns out that the quantum correction may lead, in principle, to surprisingly strong and interesting effects in astrophysics and cosmology a .

Two alternative theories to dark matter are investigated by testing their ability to describe consistently the dynamics of the Milky Way. The first one refers to a modified gravity theory having a running gravitational constant and the second assumes that dark matter halos are constituted by a Bose-Einstein condensation. The parameters of each model as well as those characterizing the stellar subsystems of the Galaxy were estimated by fitting the rotation curve of the Milky Way. Then, using these parameters, the vertical acceleration profile at the solar position was computed and compared with observations. The modified gravity theory overestimates the vertical acceleration derived from stellar kinematics while predictions of the Bose-Einstein condensation halo model are barely consistent with observations. However, a dark matter halo based on a collisionless fluid satisfies our consistency test, being the best model able to describe equally well the rotation curve and the vertical acceleration of the Galaxy.

The paper is about possible effects of infrared quantum contributions to General Relativity on disk and elliptical galaxies. The Renormalization Group corrected General Relativity (RGGR model) is used to parametrize these quantum effects. The new RGGR results presented here concern the elliptical galaxy NGC 4374 and the dwarf disk galaxy DDO 47. Using the effective approach to Quantum Field Theory in curved background, one can argue that the proper RG energy scale, in the weak field limit, should be related to the Newtonian potential. In the context of galaxies, this led to a remarkably small variation of the gravitational coupling G, while also capable of generating galaxy rotation and dispersion curves of similar quality to the the best dark matter profiles (i.e., the profiles that have a core).

The quantum contributions to the gravitational action are relatively easy to calculate in the higher derivative sector of the theory. However, the applications to the postinflationary cosmology and astrophysics require the corrections to the Einstein-Hilbert action and to the cosmological constant, and those we can not derive yet in a consistent and safe way. At the same time, if we assume that these quantum terms are covariant and that they have relevant magnitude, their functional form can be defined up to a single free parameter, which can be defined on the phenomenological basis. It turns out that the quantum correction may lead, in principle, to surprisingly strong and interesting effects in astrophysics and cosmology a .

In this work we explore the Renormalization Group (RG) corrections to General Relativity in the galactic domain. The approach here employed, which we call RGGR, is based on a relation between the RG energy scale µ and the Newtonian potential Φ N : µ ∝ Φ α N , where α is a constant. Here we present the fits to 3 of a larger sample of galaxies (about 50), with which we confirm some results: RGGR without dark matter generates galaxy rotation curves that are usually better than the ones generated by either MOND or NFW (once both the shape and the expected massto-light ratios are evaluated). Generally, galaxies that have clear problems with the NFW halo, due to its cuspy nature, are nicely fit within RGGR.