arXiv subjects

Federico Scali

Publications and source records attributed to Federico Scali.

4 recordsLinked to original sources

arXiv2026

An inductive approach to $f(R)$ gravity and its application to extended sources

In a previous work (Phys. Rev. D 110, 064042), a new family of $f(R)$ gravitational Lagrangians was constructed inductively using only Solar System physics. Specifically, the modified Einstein equations were solved perturbatively on a Schwarzschild background, and the corresponding Lagrangian was reconstructed a posteriori from the solution. Classical Solar System tests were then employed to constrain the fundamental length scale quantifying the deviation from general relativity. In the first part of this work, the construction of the model is critically reviewed, emphasizing the generality of the approach and the applicability to different modified gravity frameworks. In the second part, the modified Newtonian potential produced by an extended source is derived within the new inductive $f(R)$ model, discussing the consistency of the Newtonian limit. In this context, the application to galactic dynamics emerges as an intriguing perspective.

gr-qc↗

arXiv2025

The cosmological constant problem: from Newtonian cosmology to the greatest puzzle of modern theoretical cosmology

The cosmological constant problem is one of the greatest challenges in contemporary physics, since it is deeply rooted in the problematic interplay between quantum fields and gravity. The aim of this work is to review the key conceptual elements needed to formulate the problem and some ideas for a possible solution. I do so by weaving a fil rouge from Newtonian cosmology, through general relativity and the standard model of relativistic cosmology ({\Lambda}-CDM), up to the theory of quantum fields. In the first part, the issues with the application of Newtonian gravity to an infinite and static universe are addressed, observing how a cosmological term in the Poisson equation would stabilize a homogeneous matter distribution. A toy derivation of the Friedman equations using only Newtonian arguments is also shown. In the second part, the conceptual path leading to general relativity and the {\Lambda}-CDM model is laid down, with particular emphasis to the historical introduction of the cosmological constant and its new role after the discovery of the accelerated expansion of the universe. Finally, the problem is formulated within the framework of quantum field theory. Its many facets are discussed together with the criticalities in the formulation and some of the leading ideas for its solution are outlined.

gr-qc↗

arXiv2024

Asymptotically Conically Minkowskian spacetimes from self-gravitating dust

In this work we investigate some non-Newtonian effects in exact solutions of the Einstein equations, which describe stationary and axisymmetric configurations of self-gravitating dust. A distinctive feature of these solutions is the potential presence of conical singularities along the rotation axis, manifesting as angular deficits. While such singularities can be removed by imposing suitable boundary conditions along the axis, asymptotically far away from it the geometry becomes locally flat, in the sense that the Riemann tensor vanishes, but globally, instead of reducing to Minkowski space, it takes the form of a cone. We refer to these spacetimes as Asymptotically Conically Minkowskian (ACM). We show that such conical structure can originate some interesting effects as seen by asymptotic local observers. These include modifications to the gravitational lensing and the misinterpretation of the vacuum state of a scalar field as a distribution of scalar particles.

gr-qc↗

arXiv2024

Asymptotically Schwarzschild solutions in $f(R)$ extension of general relativity

We address the question of how to build a class of $f(R)$ extensions of General Relativity which are compatible with solar system experiments, without making any preliminary assumption on the properties of $f$. The aim is reached by perturbatively solving the modified Einstein equations around a Schwarzschild background and retrieving a posteriori the corresponding $f(R)$. This turns out to be non analytical in $R=0$ and should be intended as the leading correction to the Einstein-Hilbert action in the low curvature limit. The parameters characterizing the $f(R)$ class are then set by constraining the corrections to four different local tests with the observations. The result is a class of $f(R)$ theories built up from a purely bottom-up approach and compatible with the local tests. At a more general level, this result can help constraining exact $f(R)$ models working in Cosmology, since it provides the correct local limit. Further developments and possible extensions of the approach to Cosmology are also discussed.

gr-qc↗