Research interests

Modified gravity from a geometric perspective

My research is in theoretical gravitation, cosmology and relativistic astrophysics. I work on geometric extensions of General Relativity and on their applications to black holes, compact objects, cosmology and gravitational-wave signatures. A central theme of my work is that gravity need not be described only by curvature: depending on the geometric structure, torsion, nonmetricity, or an independent affine connection can become part of the gravitational dynamics.

General Relativity is remarkably successful, but it is not the only possible geometric description of gravity. One can modify the gravitational theory by adding new invariants to the action, changing the geometric structure of spacetime, or introducing additional fields that interact with the metric or the connection. These possibilities are not completely separate: many theories can be written in more than one language, and the same physical idea can sometimes appear as curvature, torsion or nonmetricity depending on the variables used.

My current work focuses mainly on non-Riemannian and gauge-theoretic formulations of gravity. This includes teleparallel gravity, symmetric teleparallel gravity, Poincaré gauge theory and metric-affine gravity. In these frameworks the choice of geometry determines which quantities are dynamical, how matter couples to gravity, and which new physical effects can appear.

Black holes and compact objects

Exact solutions, regular black holes, hairy configurations, spin-charge interactions, superradiance and observational degeneracies.

Cosmology

Background dynamics, perturbations, late-time acceleration and the role of torsion and nonmetricity in homogeneous and isotropic universes.

Gravitational waves

Propagation, polarizations, extra degrees of freedom and possible signatures of non-Riemannian geometry.

Representation of possible ways of modifying General Relativity
A schematic representation of possible ways of modifying General Relativity.

Teleparallel gravity

Teleparallel gravity gives an alternative geometric formulation of gravitation. Instead of describing gravity through curvature, the teleparallel equivalent of General Relativity uses a curvature-free connection and attributes gravity to torsion. The resulting theory is dynamically equivalent to General Relativity, but it opens a different route for building modified gravity models.

$$S_{\rm TEGR}=\frac{1}{16\pi G}\int T e\,d^4x,$$

where $e=\sqrt{-g}=\det(e^a{}_{\mu})$ and $T$ is the torsion scalar. The torsion scalar and the Levi-Civita Ricci scalar differ by a boundary term,

$$\bar{R}=-T+\frac{2}{e}\partial_{\mu}(eT^{\mu})=-T+B.$$

This relation is the starting point for many extensions, including $f(T)$ gravity, $f(T,B)$ gravity, teleparallel analogues of scalar-tensor theories, and teleparallel Gauss-Bonnet models. My work has explored these theories in cosmology, black-hole physics, perturbation theory and gravitational-wave phenomenology.

Metric-affine and gauge formulations of gravity

A broader route is to move from Riemannian geometry to a metric-affine geometry. In this setting the metric and the affine connection are independent objects. The independent connection can carry torsion and nonmetricity,

$$T^{\lambda}{}_{\mu\nu}=2\tilde{\Gamma}^{\lambda}{}_{[\mu\nu]}, \qquad Q_{\lambda\mu\nu}=\tilde{\nabla}_{\lambda}g_{\mu\nu}.$$

The connection can be decomposed into the Levi-Civita part plus post-Riemannian pieces,

$$\tilde{\Gamma}^{\lambda}{}_{\mu\nu}=\Gamma^{\lambda}{}_{\mu\nu}+K^{\lambda}{}_{\mu\nu}+L^{\lambda}{}_{\mu\nu},$$

where $K^{\lambda}{}_{\mu\nu}$ contains torsion and $L^{\lambda}{}_{\mu\nu}$ contains nonmetricity. This makes metric-affine gravity a natural framework for studying gravitational degrees of freedom associated with spin, dilation and shear-type geometric structures.

In recent years I have studied exact black-hole solutions, algebraic classification, cosmological perturbations, stability and gravitational waves in metric-affine and Poincaré gauge theories. A major motivation is to understand when torsion and nonmetricity are merely auxiliary fields and when they become genuinely dynamical, propagating sectors with possible signatures in astrophysics or cosmology.

Black holes, gravitational waves and phenomenology

A large part of my research connects formal gravitational theory with concrete physical systems. Black holes are especially useful because they test the nonlinear regime of gravity and expose whether extra geometric degrees of freedom can be hidden, sourced, screened or observed. My work in this direction includes regular black holes with scalar hair, black holes in Weyl-Cartan and metric-affine geometries, teleparallel scalarization, electromagnetic couplings to torsion, and superradiance in Poincaré gauge theory.

On the cosmology and gravitational-wave side, I am interested in how modified geometric sectors affect perturbations, wave propagation, polarization content and possible observational tests.