Extensions of equivalent representations of gravity are discussed in the metric-affine framework. First, we focus on: (i) General Relativity, based upon the metric tensor whose dynamics is given by the Ricci curvature scalar R; (ii) the Teleparallel Equivalent of General Relativity, based on tetrads and spin connection whose dynamics is given by the torsion scalar T; (iii) the Symmetric...
We explore violations of the equivalence principle within the framework of metric-affine gravity and establish their connection to finite-temperature effects. Thermal corrections to particle dynamics—originally derived in quantum field theory—can be reformulated in a Riemannian setting, leading to a temperature-dependent shift in the gravitational-to-inertial mass ratio. We show that the...
Throughout the years, various theoretical and experimental findings have challenged the validity of General Relativity at both ultraviolet and infrared scales. In an effort to address some of these shortcomings, extendend gravity models considering modifications of the gravitational action have been proposed. One possible extension involves including the so-called Gauss-Bonnet term in the...
In this talk, I will report on a new covariant reformulation of the Dirac field in General Relativity, based on its polar decomposition allowing a fluid-like spinorial description without the explicit use of tetrads or Clifford matrices. Working in the “spinorial” signature (+,−,−,−), a fully covariant (1+1+2) framework is presented, in which the velocity and spin fields are the generators of...
The gravitational interaction, in the form of the Einstein–Cartan theory, can emerge from a pre-geometric gauge theory via a mechanism of spontaneous symmetry breaking. In this context, pre-geometry refers to the lack of a metric structure for spacetime, which can be recovered only in the spontaneously broken phase, below a critical energy near the Planck scale. The fundamental field of this...
For this presentation, we analyze a 1-loop corrected extension of the classical CGHS model of two-dimensional dilaton gravity. The 1-loop effective action consists of three key components, the first being the standard non-local Polyakov action, accounting for quantum fluctuations of matter fields, while the second is a Polyakov-type term constructed using an auxiliary flat metric, which...
I will explore extended theories of gravity that include topological terms, focusing on how symmetry principles can be used to identify physically viable models. Symmetries provide a natural criterion for selecting and constraining the allowed gravitational actions and they also play a central role in shaping the underlying geometric and topological structure of spacetime. By employing these...
We investigate the stochastic gravitational wave background (SGWB) generated by primordial black hole (PBH) encounters in the framework of large extra dimensions (ADD model).
In this scenario, gravity propagates in D=4+n dimensions, modifying the short-distance gravitational potential.
We derive the spectral energy distribution dE/df for PBH–PBH interactions, where a localized burst of...
The Weak Gravity Conjecture (WGC) was originally formulated for U(1) gauge theories in asymptotically flat spacetime, ensuring the decay of extremal Reissner-Nordström black holes and preventing the existence of stable remnants. This principle implies that gravity must be the weakest force for at least one particle, a condition consistent with observations. Since its proposal, several...
Light bosons such as the QCD axion are leading dark matter candidates, with photon couplings enabling both laboratory and astrophysical searches. I will highlight new cavity-based experiments, in particular FLASH, which makes use of high-$Q$ resonators and quantum sensors to open previously inaccessible parameter space and even probe high-frequency gravitational waves. Complementing these...
In this work, we compute the next-to-leading-order radiation-reaction modification to the harmonic coordinate quasi-Keplerian parametrization of the binary dynamics, the two bodies undergoing a scattering process. The solution for the radiation-reaction corrections to the orbital parameters is examined both in the time domain and in the frequency domain. The knowledge of the radiation-reaction...
Usual calculations of the (Euclidean) effective action in quantum gravity, performed within the heat-kernel formalism, give rise to quartic and quadratic UV-sensitive contributions (Planck scale) to the vacuum energy. The comparison of this result to the observed value of the vacuum energy unveils a severe naturalness problem, the strongest facet of the long-standing “cosmological constant...
Considering the Einstein-Hilbert truncation for the (Euclidean) quantum gravity action, I will mainly focus on the derivation of the Wisonian renormalization group (RG) equations for the Newton and cosmological constant. I will show that particular attention has to be paid to the path integral measure and to a proper introduction of the physical running scale. It will turn out that,...
According to usual calculations in quantum field theory, both in flat and curved spacetime, the mass of a scalar particle is quadratically sensitive to the ultimate scale of the theory, the UV physical cutoff. Elaborating on previous work in quantum gravity, I will show that (when due attention is paid to the path integral measure and to the way the physical cutoff is introduced) the mass of...
Within the framework of quantum field theory, we investigate neutrino oscillations in the presence of a torsion background. Adopting the Einstein–Cartan theory, we analyze two distinct scenarios: a constant torsion field and a torsion field linearly dependent on time. In both cases, we derive modified neutrino oscillation formulas that explicitly depend on the spin orientation of the...
I will discuss recent progress in string cosmology. Including all-order α′ corrections leads to a richer and consistent picture of the pre-Big Bang universe. In this framework, the early universe can evolve smoothly through a non-singular bounce, connecting two dual phases without encountering a singularity. When a suitable potential is added for the dilaton, this setup can also stabilize the...
I introduce quasars as new cosmological probes, leveraging the UV–X-ray luminosity relation and the Lusso & Risaliti catalog to build an extended Hubble diagram up to z∼7. I present joint analyses with several crucial probes as SNe Ia, BAO, DES, and CMB to test ΛCDM and dark energy models. The results show that simple model extensions fail to resolve current tensions, while interacting dark...
Neutrons can play a crucial role in exploring possible extensions of the Standard Model involving hidden sectors. Among the proposed scenarios, the mirror matter model predicts the existence of mirror neutrons as viable dark matter candidates. In this work, we investigate how neutron–mirror neutron mixing could manifest through two complementary interferometric signatures. The first is a...
The incoming Roman Galactic Exoplanet Survey promises to detect more than 1500 bound planets by the microlensing technique. These planets are particularly precious as they cover a corner of the parameter space barely touched by other methods (1-10 au orbits down to Mars mass planets). In addition, hundreds of free-floating planet detections will shed light on these mysterious wanderers. The...
In this talk, I will present the experimental results that have motivated the introduction of a possible fifth fundamental force, mediated by a massive vector boson. I will also discuss how the inclusion of such a massive vector mediator could help address certain discrepancies between the theoretical predictions of the Standard Model and recent experimental observations.
The effect of dark scalar- and vector-mediated interactions on the stellar structure of dark matter admixed neutron stars are investigated employing the two-fluid formalism of the TOV equations. Three different nuclear equations of state (BSk22, MPA1 and APR4) are used to describe the baryonic sector, while the dark component consists of fermionic particles treated within a relativistic mean...
The Maldacena-Shenker-Stanford (MSS) conjecture establishes the existence of an upper bound to the Lyapunov exponent of a thermal quantum system with a large number of degrees of freedom. Holographic calculations of out-of-time order correlation functions (OTOCs), which are conveniently employed as indicators of the magnitude of quantum chaos, motivate such a statement, leading to the...
