arXiv subjects

Martina Adamo

Publications and source records attributed to Martina Adamo.

5 recordsLinked to original sources

arXiv2025

Noncommutative Lightcones from Quantum SO(2,1) Conformal Groups

Five new families of noncommutative lightcones in 2+1 dimensions are presented as the quantizations of the inequivalent Poisson homogeneous structures that emerge when the lightcone is constructed as a homogeneous space of the SO(2,1) conformal group. Each of these noncommutative lightcones maintains covariance under the action of the respective quantum deformation of the SO(2,1) conformal group. We discuss the role played by SO(2,1) automorphisms in the classification of inequivalent Poisson homogeneous lightcones, as well as the geometric aspects of this construction. The localization properties of the novel quantum lightcones are analyzed and shown to be deeply connected with the geometric features of the Poisson homogeneous spaces.

hep-th↗

arXiv2024

Deterministic evolution of gauge fields through a singularity

The nature of gravitational singularities has been questioned by some recent research, challenging the notion that classical determinism breaks down at these points. By allowing for dynamic changes in the orientation of spatial hypersurfaces, Einstein's equations can be uniquely extended across singularities in certain symmetry-reduced models. A key step in this work was to reformulate the dynamical equations in terms of physical degrees of freedom. The singular behavior, it turns out, is confined to the gauge or unphysical degrees of freedom, and the physical ones evolve smoothly through the singularity. This paper builds on these findings, extending them to a model of gravity coupled with Abelian gauge fields in a homogeneous but anisotropic universe. The study reveals that near the big bang, the dynamics of geometry and gauge fields can be reformulated in a way that preserves determinism, provided there is a change of orientation at the singularity. Intriguingly, the gauge fields are shown to maintain their orientation through the singularity, unlike the spatial hypersurfaces. This suggests that the predicted orientation change of spatial hypersurfaces has physical significance, potentially allowing an observer to determine which side of the big bang they occupy. These results are proved to extend also to non-Abelian gauge fields with only one spatial component.

gr-qc↗

arXiv2023

Astrophysical black holes: theory and observations

These notes cover part of the lectures presented by Andrea Maselli for the 59th Winter School of Theoretical Physics and third COST Action CA18108 Training School 'Gravity -- Classical, Quantum and Phenomenology'. The school took place at Palac Wojanów, Poland, from February 12th to 21st, 2023. The lectures focused on some key aspects of black hole physics, and in particular on the dynamics of particles and on the scattering of waves in the Schwarzschild spacetime. The goal of the course was to introduce the students to the concept of black hole quasi normal modes, to discuss their properties, their connection with the geodesic motion of massless particles, and to provide numerical approaches to compute their actual values.

gr-qc↗

arXiv2023

Introduction to noncommutative field and gauge theory

These are lecture notes for an introductory course on noncommutative field and gauge theory. We begin by reviewing quantum mechanics as the prototypical noncommutative theory, as well as the geometrical language of standard gauge theory. Then, we review a specific approach to noncommutative field and gauge theory, which relies on the introduction of a derivations-based differential calculus. We focus on the cases of constant and linear noncommutativity, e.g., the Moyal spacetime and the so-called $\mathbb{R}^3_λ$, respectively. In particular, we review the $gφ^4$ scalar field theory and the $U(1)$ gauge theory on such noncommutative spaces. Finally, we discuss noncommutative spacetime symmetries from both the observer and particle point of view. In this context, the twist approach is reviewed and the $λ$-Minkowski $gφ^4$ model is discussed.

hep-th↗

arXiv2022

Astrophysical sources and acceleration mechanisms

Multi-messenger astronomy provides for the observation of the same astronomical event with different kind of telescopes at the same time: optical observations, X-rays, gamma-ray bursts, neutrinos and, most recently, gravitational waves are just few examples of the several points of view from which an astronomical event can be observed and analyzed. Cosmic rays play an important role in multi-messenger astronomy and, for this reason, it is important to deepen the study of their sources and to understand the mechanisms behind their acceleration in astronomical environments.

astro-ph.HE↗