Research Interests

I am a theoretical cosmologist who tries to identify ways to infer the fundamental properties of the universe by probing the Large-Scale Structure of the universe. I am particularly interested in discerning the naturate of the accelerated expansion of the universe and gravity at large scales.

You may find my full publication record in the ArXiv and inspire-HEP databases.

Ever since the initial discovery of the accelerated expansion of the Universe over two decades ago, tremendous observational efforts have uncovered a unique physical model, that can successfully account for all observations. Within this novel paradigm, the cosmic energy budget needs to be augmented by two additional components, "dark matter" and "dark energy'", or a modification to gravity at cosmic scales. Despite this remarkable achievement, crucial theoretical challenges have been posed, since the fundamental nature of this mysterious dark sector still remains elusive. 

In an exciting time for cosmology, my research has been focused on bridging the gap between the underlying physical theories and the upcoming, precise, cosmological observations. In my doctoral research, I focused on discerning the nature of cosmic acceleration. Within the minimal picture dictated by the Λ Cold Dark Matter (ΛCDM) scenario, acceleration is attributed to vacuum energy, by means of a positive cosmological constant Λ. Another possibility, however, could be that this behavior hints a breakdown of General Relativity (GR) at cosmic scales, as hypothesized by the Modified Gravity (MG) theories. Changes to gravity would alter, however, the growth of the primordial density perturbations, leaving distinct imprints on the observed late-time pattern of galaxies, that can be tightly constrained by the current and future LSS observations. 

Efficient simulations in Modified Gravity scenarios

In order to evade the tight Solar System constraints placed on gravity, MG candidates typically invoke a restoring, ``screening'' mechanism in the high-density environments. This mechanism, however, relies upon the non-linear MG scalar field interactions, that significantly slow down N-body simulations for structure formation, rendering them intractable. In this work I employed the hybrid CO-moving Lagrangian Acceleration (COLA) scheme and produced efficient N-body simulations for such MG theories, achieving an accuracy of 1%, compared to the full N-body implementation, at only 1% of the standard computational time. 

Tailoring marked statistics to reveal modified gravity

Viable screening mechanisms heavily penalize potential deviations in the high-density regions of the universe. As a consequence of this distinct phenomenology, potential signals could remain undetected, if analyses purely focus on clustering in dense regions, despite the unprecedented improvement on the observational front. By re-weighting cosmic density fields, however, emphasizing on the significance of cosmic voids, degeneracies between modifications to gravity and ΛCDM can be manifestly broken, and previously hidden signals exposed, as I demonstrated in this paper.

Analytical models of galaxy clustering in modified gravity

The galaxies observed by cosmological surveys represent an ideal window into the fundamental processes that shaped the LSS of the universe, which however, do not perfectly trace the underlying dark matter density field, but are biased tracers of it. Employing a new analytical model I developed for the halo bias, taking into account the novel phenomenology introduced by MG, in this paper I produced predictions for the clustering statistics of galaxies, which were shown to match full N-body simulations down to scales of r~20 Mpc/h, in a variety of MG screening scenarios. The code to predict the correlation function for biased tracers in these MG models can be found in this repository.

Modeling Redshift Space Distortions in modified gravity

Spectroscopic surveys, such as NASA's Euclid or DESI, identify galaxies in redshift space, introducing anisotropic Redshift Space Distortions (RSD) to the observed clustering pattern. By complimenting my clustering model with a redshift space prescription, I was able to accurately capture the simulated anisotropic redshift space correlation function for halos across a wide spectrum of MG models, as I found here. This work represents the first analytical model that simultaneously captured the effects of both large-scale halo bias and redshift space distortions in the complicated phenomenology of MG. A code to predict the anisotropic correlation function for biased tracers in such MG models is available in this repository.