We generalize the Chern-Simons modified gravity to metric-affine case and impose projective invariance by supplementing Pontryagin density with homothetic curvature terms which do not spoil topologicity. The latter is then broken promoting coupling of term a (pseudo)-scalar field. solutions for torsion nonmetricity are derived perturbatively, showing that they can be iteratively obtained from background fields. This allows us describe dynamics metric scalar field perturbations in...

In the context of metric-affine Chern-Simons gravity endowed with projective invariance, we derive analytical solutions for torsion and nonmetricity in homogeneous isotropic cosmological case, described by a flat Friedmann-Robertson-Walker metric. We discuss some details general properties presence perfect fluid, such as dynamical stability emergence big bounce points, examine structure specific reproducing de Sitter power law behaviours scale factor. Then, focus on first-order perturbations...

Abstract We discuss how tensor polarizations of gravitational waves can suffer Landau damping in the presence velocity birefringence, when parity symmetry is explicitly broken. In particular, we analyze role Nieh-Yan and Chern-Simons terms modified theories gravity, showing perturbation collisionless media be characterized by a subluminal phase velocity, circumventing well-known results General Relativity allowing for appearance kinematic damping. investigate detail connection between...

We extend the notion of Nieh-Yan invariant to generic metric-affine geometries, where both torsion and nonmetricity are taken into account. Notably, we show that properties projective invariance topologicity can be independently accommodated by a suitable choice parameters featuring this new term. then consider special class modified theories gravity able promote Immirzi parameter dynamical scalar field coupled form, discuss in more detail dynamics effective tensor theory stemming from such...

In the context of $f(R)$ generalizations to Holst action, endowed with a dynamical Immirzi field, we derive an analytic solution describing asymptotically anti--de Sitter black holes hyperbolic horizon. These exhibit scalar hair second kind, which ultimately depends on field radial behavior. particular, show how modifies usual entropy law associated hole. We also verify that boils down constant value in asymptotic region, thus restoring standard loop quantum gravity picture. finally prove...

Quadratic scale-invariant gravity non minimally coupled to a scalar field provides competitive model for inflation, characterized by the transition from an unstable stable fixed point, both constant configurations. We provide complementary analysis of same in static, spherically symmetric setting, obtaining two Schwarzschild-de Sitter solutions, which corresponds points existing cosmological scenario. The stability such solutions is thoroughly investigated different perspectives. First, we...

We consider special classes of Palatini f(R) theories, featured by additional Loop Quantum Gravity inspired terms, with the aim identifying a set modified Ashtekar canonical variables, which still preserve SU(2) gauge structure standard theory. In particular, we allow for affine connection to be endowed torsion, turns out depend on scalar degree affecting gravity, and in this respect successfully construct novel Gauss constraint. analyze role field, outlining as it acquires dynamical...

In the context of f(R) generalizations to Holst action, endowed with a dynamical Immirzi field, we derive an analytic solution describing asymptotically anti-de Sitter black holes hyperbolic horizon. These exhibit scalar hair second kind which ultimately depends on field radial behaviour. particular, show how modifies usual entropy law associated hole. We also verify that boils down constant value in asymptotic region, thus restoring standard loop quantum gravity picture. finally prove...

In the context of metric-affine Chern-Simons gravity endowed with projective invariance, we derive analytical solutions for torsion and nonmetricity in homogeneous isotropic cosmological case, described by a flat Friedmann-Robertson-Walker metric. We discuss some details general properties presence perfect fluid, such as dynamical stability emergence big bounce points, examine structure specific reproducing de Sitter power law behaviours scale factor. Then, focus on first-order perturbations...

We discuss how tensor polarizations of gravitational waves can suffer Landau damping in the presence velocity birefringence, when parity symmetry is explicitly broken. In particular, we analyze role Nieh-Yan and Chern-Simons terms modified theories gravity, showing perturbation collisionless media be characterized by a subluminal phase velocity, circumventing well-known results General Relativity allowing for appearance kinematic damping. investigate detail connection between thermodynamic...

Quadratic scale-invariant gravity non minimally coupled to a scalar field provides competitive model for inflation, characterized by the transition from an unstable stable fixed point, both constant configurations. We provide complementary analysis of same in static, spherically symmetric setting, obtaining two Schwarzschild-de Sitter solutions, which corresponds points existing cosmological scenario. The stability such solutions is thoroughly investigated different perspectives. First, we...

We show that the Nieh-Yan topological invariant breaks projective symmetry and loses its character in presence of non vanishing nonmetricity. The notion is then extended to generic metric-affine case, defining a generalized term, which allows recover topologicity invariance, independently. As concrete example class modified theories gravity considered dynamical properties are investigated cosmological setting. In particular, bouncing solutions Bianchi I models derived. Finite time...