arXiv subjects

Leonardo Torcellini

Publications and source records attributed to Leonardo Torcellini.

11 recordsLinked to original sources

arXiv2026

Numerical polology: towards next-generation model-building for cosmology

The dark sector need not be restricted to simple field content. Indeed, simple bosonic configurations, such as scalar-tensor or dark photon models, contrast with the much richer picture painted by many ultraviolet scenarios. Polology is the study of propagator poles, which correspond to particle states in any given theory. We outline a numerical polology framework for discovering perturbative, ghost-free models with consistent interactions, which produces theoretical model priors by sampling the coupling space. The method is tested on tensor field theories of up to rank three. Subsequent observational constraint pipelines are illustrated for black hole superradiance (M33 X-7), dynamical dark energy (DESI DR2, Pantheon and SH0ES) and gravitational waves (GWTC-3).

astro-ph.CO↗

arXiv2026

The Gravitational Form Factor of the Pion in Perturbative QCD with a Dilaton Interaction

We investigate the pion gravitational form factors (GFFs) at intermediate and large momentum transfer within the framework of QCD factorization. Our analysis centers on the non-Abelian $TJJ$ correlator, which couples the local QCD energy-momentum tensor to two external gluon fields and explicitly encodes the perturbative effects of the trace anomaly. We demonstrate how this quantum anomaly induces a scalar, dilaton-like contribution to the hard-scattering kernel. To ensure field-theoretic consistency, a careful separation of the quark and gluon sectors is performed, accounting for the modifications introduced by gauge-fixing terms and Slavnov-Taylor identities on the off-shell gluonic structure. To obtain realistic phenomenological predictions and regulate soft-gluon endpoint divergences in the hard kernel, we implement the Sudakov resummation framework coupled with a Gaussian model for the pion's transverse-momentum-dependent wave function. We show that the resulting anomaly-induced corrections significantly modify the behavior of the pion GFFs at large momentum transfer, leaving a unique imprint on the trace sector and the $D$-term.

hep-ph↗

arXiv2026

The Case for Astrons

We examine a proposed population of primordial, electrically charged compact objects, which we call astrons, with fiducial parameters $M_A\sim10^{12}M_\odot$, $Q_A\sim4\times10^{32}\,\mathrm{C}$, and megaparsec-scale separations. We analyze charge generation, ordinary accretion saturation, charge persistence in an ionized medium, plasma screening, the Reissner--Nordstr\"om and Kerr--Newman geometric regimes, lensing, and the possible use of Lyman-$\alpha$ absorption as a probe of astron electric fields, and the cosmological interpretation of a sparse charged population. The large-charge branch is not obtained from ordinary accretion saturation; it should be treated as a primordial or early-universe charge-concentration hypothesis. A horizon-mass estimate places a $10^{12}M_\odot$ primordial object at times of order months after the Big Bang, so any relation to the early structures observed by the James Webb Space Telescope would be indirect, through later baryonic assembly around dark seeds. The main constraints are severe: plasma screening and neutralization must be avoided, the fiducial charge drives the exterior into a super-extremal regime without a Reissner--Nordstr\"om photon sphere, and the homogeneous interaction energy of a charged population scales as $a^{-4}$. Thus the simplest FLRW perfect-fluid reduction does not generate asymptotic late-time acceleration. Any viable cosmological role for astrons must instead come from a controlled inhomogeneous Einstein--Maxwell averaging problem beyond the homogeneous approximation.

gr-qc↗

arXiv2026

Astrons: Reissner-Nordstr\"om Primordial Naked Singularities

We summarize a set of constraints on a proposed population of primordial, ultra-massive, electrically charged compact objects, which we call astrons. The analysis combines charge generation, charge saturation, persistence of the charge in an ionized medium, screening by the intergalactic plasma, the Reissner--Nordstr\"om geometry of highly charged compact objects, lensing, and the cosmological implications of a sparse charged population. We also discuss the possible relation to the early structures revealed by the James Webb Space Telescope: if astrons are relevant there, they would be primordial dark seeds rather than luminous objects directly observed at high redshift. The resulting scenario is sharply constrained. Ordinary accretion saturation gives charges far below the large-charge phenomenological benchmark, screening is a serious plasma-physics issue, and a large charge can place the exterior geometry deep in the super-extremal regime. As expected at the level of a homogeneous Friedmann--Lema\^{\i}tre--Robertson--Walker (FLRW) description, the interaction energy of a population of charged objects scales as $a^{-4}$, so the simplest perfect-fluid reduction does not generate asymptotically late-time acceleration; any acceleration era tied to that homogeneous component can only be transitory. The astron scenario should be regarded as a constrained framework whose viability depends on plasma physics and on a cosmological treatment beyond the homogeneous approximation.

astro-ph.HE↗

arXiv2026

Anomaly-mediated Scalar Gravitational Interactions and the Coupling of Conformal Sectors

We investigate the anomaly-induced activation of a gauge-invariant scalar degree of freedom in General Relativity, the conformalon mode, directly at the level of $2\to2$ scattering amplitudes. The analysis couples anomalous three-point functions of conformal sectors, involving gravitons $(TTT)$ and Abelian gauge currents $(TJJ)$, through single-graviton exchange derived from the quadratic expansion of the Einstein--Hilbert action. Unlike related treatments based on the nonlocal anomaly action, these interactions are suppressed by the Planck scale. We show that the conformalon, invariant under linearized diffeomorphisms, admits an interpretation as an effective scalar correction to scattering amplitudes, both in virtual exchange channels and in effective real-emission processes. Around flat space, this behaviour arises from anomaly-induced nonlocal massless insertions on the external graviton and photon legs of the three-point functions, sewn through the scalar component of the graviton propagator in de Donder gauge. The resulting anomaly-mediated $4$-point interaction reduces to contact terms, with the Planck mass setting the suppression scale. The construction consistently matches the spin decomposition of flat-space conformal Ward identities in momentum space, which determine the vertices, with the corresponding spin decomposition of the graviton propagator. In the eikonal limit, these interactions generate contact corrections to the leading logarithmic phase in impact-parameter space. We further show that anomaly-mediated $2\to2$ graviton amplitudes associated with the virtual exchange of such modes exhibit a characteristic double-copy structure.

hep-th↗

arXiv2026

Dilaton Sum Rules of Gravitational Form Factors in QCD at Order $\alpha_s$

We formulate a partonic description of hadronic gravitational form factors within QCD, focusing on the three-point function of the energy-momentum tensor and two gluon currents. Despite the lack of exact conformal symmetry in QCD, the correlator may be organized around the conformal limit through momentum-space CFT methods, suitably adjusted for gauge-fixing effects. This yields a tensor decomposition into spin-2, spin-1, and spin-0 sectors, with the spin-0 contribution governed by the conformal anomaly. The corresponding anomaly form factor satisfies a mass-independent dispersive sum rule and allows a dilaton-like interpretation. In the light-cone limit, this term and an additional traceless structure become dominant, indicating an effective anomaly-mediated description relevant to hadronic gravitational form factors.

hep-ph↗

arXiv2025

Gravitational Form Factors and the QCD Dilaton at Large Momentum Transfer

We investigate the hard scatterings of hadronic matrix elements corresponding to hadronic gravitational form factors (GFFs) of the pion and proton using QCD factorization, applying conformal field theory (CFT) tools. These GFFs are key to understanding quark and gluon angular momentum via their connection to DVCS moments. The core object is the non-Abelian $ TJJ $ 3-point function, which shows an anomaly-induced dilaton exchange in the $ t $-channel. We analyze quark, ghost, and gauge-fixing effects through a CFT-based decomposition and propose a parameterization useful for future DVCS studies at the Electron-Ion Collider. The dilaton interaction is interpolated by a conformal anomaly form factor, defined in the nonconformal case, which is constrained by a (dilaton) sum rule.

hep-ph↗

arXiv2025

A Dilaton Sum Rule for the Conformal Anomaly Form Factor in QCD at Order $\alpha_s$

We present an off-shell dispersive analysis of the graviton-gluon-gluon ($TJJ$) vertex, extending previous investigations carried out in both QED and QCD. Within the framework of a non-Abelian gauge theory, we extract the conformal anomaly form factor from the trace component of the correlator and demonstrate that it satisfies a one-loop sum rule, valid under the most general kinematic conditions. Analogously to the chiral and chiral-gravitational cases, a spectral flow emerges in which the exchanged intermediate state becomes localized at zero invariant mass along the graviton line as the quark mass approaches zero. The total integral of the spectral density precisely reproduces the anomaly. We examine how the behaviour of these spectral densities evolves as the system approaches the conformal limit with on-shell gluons. The perturbative analysis reveals that such sum rules are fundamental dynamical features of anomaly-induced interactions. In particular, the appearance or absence of associated dilaton poles is closely tied to whether the sum rule is saturated by a pole contribution or by a dispersive continuum. In the conformal, on-shell limit, the particle-pole interaction yields a nonlocal S-matrix element entirely supported on the light-cone.

hep-ph↗

arXiv2024

Conformal Backreaction, Chiral and Conformal Anomalies in the Early Universe

The backreaction of a conformal matter sector and its associated conformal anomaly on gravity can be systematically studied using the formalism of the anomaly effective action. This action, defined precisely in flat spacetime within ordinary quantum field theory, can be analyzed perturbatively in terms of external graviton insertions. The expansion coefficients correspond to correlation functions of the stress-energy tensor, which are renormalized through two key counterterms: the square of the Weyl tensor $(C^2)$ and the Gauss-Bonnet term $(E)$. Anomalous conformal Ward identities impose hierarchical constraints on this expansion, revealing that the anomaly's contribution arises from bilinear mixings of the form $R \Box^{-1} E$ and $R \Box^{-1} C^2$, supplemented by local Weyl-invariant terms. These mixings reflect the non-local structure of the anomaly. The precise form of the effective action, however, may vary depending on the regularization scheme used, with potential differences manifesting through additional Weyl-invariant terms. These actions encapsulate the breaking of Weyl invariance in the early universe, with implications that are particularly relevant during the inflationary epoch. For chiral and gravitational anomalies, we demonstrate that the corresponding effective actions exhibit similar structures, influencing the evolution of chiral asymmetries in the early universe plasma.

astro-ph.CO↗

arXiv2024

Semiclassical Lensing and Radiative Lens Equations

We analyze lensing of photons and neutrinos in a gravitational field, proposing a method to include radiative effects in classical lens equations. The study uses Schwarzschild and a Reissner-Nordstrom metrics expanded at second post Newtonian order in the Newtonian potential, employing a semiclassical approach to compare one-loop corrections from the Standard Model with Einstein's deflection formula via an impact parameter representation. We also explore the energy dependence of deflection due to quantum corrections and integrate these with classical lens equations.

gr-qc↗

arXiv2023

Study of the Inflationary Spectrum in the Presence of Quantum Gravity Corrections

After a brief review of the different approaches to predict the possible quantum gravity corrections to quantum field theory, we discuss in some detail the formulation based on a Gaussian reference frame fixing. Then, we implement this scenario to the determination of the inflationary spectrum of primordial perturbations. We consider the quantization of an inhomogeneous free massless scalar field on a quasi-classical isotropic Universe, developing a WKB expansion of the dynamics at the next order in the Planckian parameter, with respect to the one at which standard QFT emerges. The quantum gravity corrections to the scale invariant spectrum are discussed in a specific primordial cosmological setting and then in a general minisuperspace formalism, showing that there is no mode-dependent effect and thus the scale invariant inflationary spectrum is preserved. Such result is discussed in connection to the absence of a matter backreaction on the gravitational background in the considered paradigm.

gr-qc↗