Masroor C. Pookkillath 교수

In this letter we propose a reduction of the H0 tension puzzle by means of a theory of minimally modified gravity which is dubbed VCDM. After confronting the theory with the data, a transition in the expansion history of the universe in the low-redshift z≃0.3 is found. From the bestfit values the total fitness parameter is improved by Δχ2=33.41, for the data set considered. We then infer the local Hubble expansion rate today within this theory by means of low redshift Pantheon data. The resultin

We study a metric cubic gravity theory considering odd-parity modes of linear inhomogeneous perturbations on a spatially homogeneous Bianchi type I manifold close to the isotropic de Sitter spacetime. We show that in the regime of small anisotropy, the theory possesses new degrees of freedom compared to General Relativity, whose kinetic energy vanishes in the limit of exact isotropy. From the mass dispersion relation we show that such theory always possesses at least one ghost mode as well as a

Abstract The Minimal theory of Massive Gravity (MTMG) is endowed non-linearly with only two tensor modes in the gravity sector which acquire a non-zero mass. On a homogeneous and isotropic background the theory is known to possess two branches: the self-accelerating branch with a phenomenology in cosmology which, except for the mass of the tensor modes, exactly matches the one of ΛCDM; and the normal branch which instead shows deviation from General Relativity in terms of both background and lin

Here we present cosmology of a class of Minimally Modified Gravity theory dubbed as $$f(\mathcal{H})$$ theory. After introducing a concrete model for the free function, we find that this cosmological model fits Planck data better than $$\Lambda $$ CDM.

Abstract We study the spherically symmetric collapse of a cloud of dust in VCDM, a class of gravitational theories with two local physical degrees of freedom. We find that the collapse corresponds to a particular foliation of the Oppenheimer-Snyder solution in general relativity (GR) which is endowed with a constant trace for the extrinsic curvature relative to the time t constant foliation. For this solution, we find that the final state of the collapse leads to a static configuration with the

Abstract In this work, we study interaction between dark energy and dark matter, where dark energy is described by a massive vector field, and dark matter is modelled as a fluid. We present a new interaction term, which affects only perturbations and can give interesting phenomenology. Then we present a general Lagrangian for the interacting vector dark energy with dark matter. For the dark energy, we choose Proca theory with G 3 term to study its phenomenological consequence. For this model, we

In this work, we study interaction between dark energy and dark matter, where dark energy is described by a massive vector field, and dark matter is modelled as a fluid. We present a new interaction term, which affects only perturbations and can give interesting phenomenology. Then we present a general Lagrangian for the interacting vector dark energy with dark matter. For the dark energy, we choose Proca theory with $G_{3}$ term to study its phenomenological consequence. For this model, we expl

We study the effect of adding an interaction in the ${G}_{3}$ term of Horndeski theory, where the propagation of gravitational waves is not modified. We derive the background and perturbation equations of motion from the action. We also derive the no-ghost and Laplacian instability conditions for tensor modes and scalar mode propagation. Then we study the evolution of the matter perturbation in the quasistatic approximation. We find that the gravitational couplings to the baryonic and cold dark

Disformal transformation provides a map relating different scalar-tensor and vector-tensor theories and gives access to a powerful solution-generating method in modified gravity. In view of the vast family of new solutions one can achieve, it is crucial to design suitable tools to guide their construction. In this work, we address this question by revisiting the Petrov classification of disformally constructed solutions in modified gravity theories. We provide close formulas which relate the pri