arXiv subjects

Francesco Sannino

Publications and source records attributed to Francesco Sannino.

At least 37 records · Page 2Linked to original sources

arXiv2025

Regular Spacetimes in the Effective Metric Description

Over the past few decades, significant effort has been directed towards developing various regularized models for compact objects. Recently, a new observable-based parametrization was introduced to account for black hole deformations in a model-independent fashion, referred to as the Effective Metric Description (EMD) \cite{Binetti:2022xdi, DelPiano:2023fiw, DelPiano:2024gvw, DelPiano:2024nrl}. In this paper, we carry out a systematic investigation of the regularity of static and spherically symmetric spacetimes by extending the EMD. We derive the conditions under which curvature scalars remain finite everywhere and the associated spacetime is geodesically complete. Our results are then used to classify the cores of regular spacetimes based on their asymptotic behavior near the origin. To illustrate our findings, we apply our regularity conditions to known black hole examples.

gr-qc↗

arXiv2025

Effective Metric Description of Charged Black Holes

Charged black holes arise as solutions of General Relativity (GR) coupled to Maxwell theory. As functions of the mass and charge, they can exhibit extremal behavior, in which case they are stable against thermal decay. (Quantum) corrections to GR are expected to alter the classical features of these objects, especially near extremality. To capture such effects in a model-independent way, we extend the Effective Metric Description (EMD) previously introduced in [Phys.Rev.D 109 (2024) 2, 024045, Eur.Phys.J.C 84 (2024) 12, 1273] for spherically symmetric and static black holes. The EMD parametrizes deformations of the metric in terms of physical quantities, such as the radial spatial distance to the event horizon. While the latter is still viable for non-extremal charged black holes, we argue that the proper time of a free-falling observer is better suited in the extremal case: we derive the necessary conditions for the parameters of such an EMD for constructing a consistent space-time in the vicinity of the (extremal) horizon. Finally, we illustrate our framework through a concrete example, and mention implications of the Weak Gravity Conjecture on the effective metric parameters.

gr-qc↗

arXiv2025

Four-Fermion Deformations on Line Defects in QED$_4$ with Yukawas

We elucidate the dynamics induced by a Wilson Line of charge $q$ and electron charge $e$ in $QED_4$ coupled to a real scalar via Yukawa interactions. We observe that there is a range of the fixed product $e^2 q$ with $e\rightarrow 0$ and $q\rightarrow \infty$ for which four-fermion operators play a dominant role for the dynamics of the theory. We uncover the fixed-point dynamics of the theory and analyze their critical behavior.

hep-th↗

arXiv2025

Consistency Relation for Fixed Point Dynamics

We gain insight on the fixed point dynamics of $d$ dimensional quantum field theories by exploiting the critical behavior of the $d-ε$ sister theories. To this end we first derive a self-consistent relation between the $d-ε$ scaling exponents and the associated $d$ dimensional beta functions. We then demonstrate that to account for an interacting fixed point in the original theory the related $d-ε$ scaling exponent must be multi-valued in $ε$. We elucidate our findings by discussing several examples such as the QCD Banks-Zaks infrared fixed point, QCD at large number of flavors, as well as the O(N) model in four dimensions. For the latter, we show that although the $1/N$ corrections prevent the reconstruction of the renormalization group flow, this is possible when adding the $1/N^2$ contributions.

hep-ph↗

arXiv2025

On the $θ$-angle physics of QCD under pressure: The strange and isospin phase diagram

We unveil the impact of the $θ$-angle on the QCD phase diagram at nonzero isospin and strangeness chemical potentials for three light flavors and different quark mass ratios. We establish the phase boundaries as well as the nature of the associated phase transitions. The order parameters and the physical spectrum in the different phases are determined. We further elucidate the physics around $θ=π$ where we discover a novel parity-preserving superfluid phase. Finally, we comment on Dashen's phenomenon in the superfluid phases when varying the number of light flavors.

hep-ph↗

arXiv2024

Effective Metric Description of 2+1 Dimensional Quantum Black Holes

We develop an effective metric description of 2+1 dimensional black holes describing deviations from the classical Bañados-Teitelboim-Zanelli (BTZ) black hole. The latter is a classical 2+1 dimensional rotating black hole with constant negative curvature. The effective metric is constrained by imposing the black hole symmetries and asymptotic classical behavior. The deformed metric is parametrized in terms of a physical quantity that we choose to be a physical distance. The latter can be solved for in three main regions of interest, the one around the horizon, origin, and spatial infinity. The finiteness of physical quantities at the horizon, such as the Ricci and Kretschmann scalars, leads to universal constraints on the physical parameters of the metric around the horizon. This allows us to further derive the general form of the corrected Hawking temperature in terms of the physical parameters of the effective metric. Assuming that the approach can be generalized to the interior of the black hole, we further develop an effective metric description near the origin. To illustrate the approach, we show how to recast the information encoded in a specific model of quantum BTZ known as quBTZ black hole in terms of the effective metric coefficients.

gr-qc↗

arXiv2024

Black Hole Shadow and other Observables away from the Horizon: Extending the Effective Metric Descriptions

In previous work we have developed a model-independent, effective description of quantum deformed, spherically symmetric and static black holes in four dimensions. The deformations of the metric are captured by two functions of the physical distance to the horizon, which are provided in the form of self-consistent Taylor series expansions. While this approach efficiently captures physical observables in the immediate vicinity of the horizon, it is expected to encounter problems of convergence at further distances. Therefore, we demonstrate in this paper how to use Padé approximants to extend the range of applicability of this framework. We provide explicit approximations of physical observables that depend on finitely many effective parameters of the deformed black hole geometry, depending on the order of the Padé approximant. By taking the asymptotic limit of this order, we in particular provide a closed-form expression for the black hole shadow of the (fully) deformed geometry, which captures the leading quantum corrections. We illustrate our results for a number of quantum black holes previously proposed in the literature and find that our effective approach provides excellent approximations in all cases.

gr-qc↗

arXiv2024

A Temporal Playbook for Multiple Wave Dengue Pandemic from Latin America and Asia to Italy

We show that the epidemiological Renormalization Group (eRG) framework is a useful and minimal tool to effectively describe the temporal evolution of the Dengue multi-wave pandemics. We test the framework on the Dengue history of several countries located in both Latin America and Asia. We also observe a strong correlation between the total number of infected individuals and the changes in the local temperature. Our results further support the expectation that global warming is bound to increase the cases of Dengue worldwide. We then move to investigate, via the eRG, the recent outbreak in Fano, Italy and offer our projections.

q-bio.PE↗

arXiv2024

Exact Results for Scaling Dimensions of Neutral Operators in scalar CFTs

We determine the scaling dimension $Δ_n$ for the class of composite operators $ϕ^n$ in the $λϕ^4$ theory in $d=4-ε$ taking the double scaling limit $n\rightarrow \infty$ and $λ\rightarrow 0$ with fixed $λn$ via a semiclassical approach. Our results resum the leading power of $n$ at any loop order. In the small $λn$ regime we reproduce the known diagrammatic results and predict the infinite series of higher-order terms. For intermediate values of $λn$ we find that $Δ_n/n$ increases monotonically approaching a $(λn)^{1/3}$ behavior in the $λn \to \infty$ limit. We further generalize our results to neutral operators in the $ϕ^4$ in $d=4-ε$, $ϕ^3$ in $d=6-ε$, and $ϕ^6$ in $d=3-ε$ theories with $O(N)$ symmetry.

hep-th↗

arXiv2024

Information index augmented eRG to model vaccination behaviour: A case study of COVID-19 in the US

Recent pandemics triggered the development of a number of mathematical models and computational tools apt at curbing the socio-economic impact of these and future pandemics. The need to acquire solid estimates from the data led to the introduction of effective approaches such as the \emph{epidemiological Renormalization Group} (eRG). A recognized relevant factor impacting the evolution of pandemics is the feedback stemming from individuals' choices. The latter can be taken into account via the \textit{information index} which accommodates the information--induced perception regarding the status of the disease and the memory of past spread. We, therefore, show how to augment the eRG by means of the information index. We first develop the {\it behavioural} version of the eRG and then test it against the US vaccination campaign for COVID-19. We find that the behavioural augmented eRG improves the description of the pandemic dynamics of the US divisions for which the epidemic peak occurs after the start of the vaccination campaign. Our results strengthen the relevance of taking into account the human behaviour component when modelling pandemic evolution. To inform public health policies, the model can be readily employed to investigate the socio-epidemiological dynamics, including vaccination campaigns, for other regions of the world.

q-bio.PE↗

arXiv2024

Charting Standard Model Duality and its Signatures

We investigate high and low energy implications of a gauge dual description of the Standard Model. The high energy electric theory features gauge dynamics involving only fermionic matter fields, while the low energy magnetic description features a quasi-supersymmetric spectrum testable at colliders. The flavour theory is constructed via operators generated at the Planck scale. We further show that duality opens novel avenues for theories of grand unification.

hep-ph↗

arXiv2024

Defect Induced Heavy Meson Dynamics in the QCD Conformal Window

Upon introducing an heavy quark in the perturbative regime of the QCD conformal window we precisely determine the associated heavy meson spectrum and wave functions in terms of the number of light flavours and mass. We then compute the conformal Isgur-Wise function which is a central quantity in heavy quark physics. We further determine the impact of the residual low energy confining dynamics on the heavy meson spectrum. As a working framework, we adapt the heavy quark effective theory to the perturbative conformal window dynamics. Our work lays the foundations to systematically go beyond the infinite mass defect approximation in conformal field theories.

hep-ph↗

arXiv2024

Two-index SU(N) theories: QCD, Orientifolds, Super Yang-Mills, Lattice and Steven Weinberg's $ππ$ scattering legacy

I review and improve on how two-index SU(N) gauge-fermion theories help access salient information about the large $N$ vacuum and spectrum of QCD, super Yang Mills and meson-meson scattering. The interplay with recent lattice simulations will be employed to deduce the size of $1/N^2$ corrections. Through the meson-meson scattering analysis I will honor Steven Weinberg's memory by showing how two-index extrapolations naturally accommodate the appearance of tetraquarks states crucial to unitarize meson-meson scattering at low energies.

hep-ph↗

arXiv2024

$Λ_b \rightarrow Λ_c^{\ast}$ at $1\,/\,m_c^2$ heavy quark order

We systematically compute the $Λ_b(p, s_b) \to Λ_c(2595)^+$ and $Λ_b(p, s_b) \to Λ_c(2625)^+$ form factors within the Heavy Quark Effective Theory (HQET) framework including $\mathcal{O}(1/m_c^2)$. Besides taking into account the Standard Model-like vector and axial contributions, we further determine tensor and pseudo-tensor form factors. Our work constitutes a step forward with respect to previous analyses allowing for a comprehensive study of the matrix element parametrisation stemming from the HQET formalism. Finally, we demonstrate that the resulting form factors agree well with lattice Quantum Chromodynamics (LQCD) determinations stressing the need and relevance of the newly derived $1/m_c^2$ corrections.

hep-ph↗

arXiv2024

New Physics Pathways from B Processes

We re-consider recent measures of $R_{K}$ and $R_{K^*}$, now compatible with the Standard Model expectations, as well as the results for the process $\text{BR}(B_s \rightarrow μ^+ μ^-)$ alongside earlier determinations of $R_{D^{(\ast)}}$ and $\text{BR}(B_c \rightarrow τν)$. We provide analytic constraints on the associated Wilson coefficients in both the $b \to s$ and the $b \to c$ sectors. These allow us to estimate the scale of potential New Physics for generic extensions of the Standard Model. We then use the results to constrain the leptoquark landscape.

hep-ph↗

arXiv2024

Effective Metric Descriptions of Quantum Black Holes

In a recent work [arXiv:2307.13489 [gr-qc]], we have described spherically symmetric and static quantum black holes as deformations of the classical Schwarzschild metric that depend on the physical distance to the horizon. We have developed a framework that allows to compute the latter in a self-consistent fashion from the deformed geometry, in the vicinity of the horizon. However, in this formalism, the distance can be replaced by other physical quantities, e.g. curvature invariants such as the Ricci- or Kretschmann scalar. Here, we therefore define a more general framework, which we call an "effective metric description" (EMD), that captures the deformed geometry based on a generic physical quantity. We develop in detail the Ricci- and Kretschmann scalar EMD, in particular demonstrating how to compute the geometry in a self-consistent manner. Moreover, we provide explicit relations that allow to express one EMD in terms of the others, thus demonstrating their equivalence.

gr-qc↗

arXiv2024

Information Theory Unification of Epidemiological and Population Dynamics

We reformulate models in epidemiology and population dynamics in terms of probability distributions. This allows us to construct the Fisher information, which we interpret as the metric of a one-dimensional differentiable manifold. For systems that can be effectively described by a single degree of freedom, we show that their time evolution is fully captured by this metric. In this way, we discover universal features across seemingly very different models. This further motivates a reorganisation of the dynamics around zeroes of the Fisher metric, corresponding to extrema of the probability distribution. Concretely, we propose a simple form of the metric for which we can analytically solve the dynamics of the system that well approximates the time evolution of various established models in epidemiology and population dynamics, thus providing a unifying framework.

q-bio.PE↗

arXiv2024

Renormalisation Group Methods for Effective Epidemiological Models

Epidemiological models describe the spread of an infectious disease within a population. They capture microscopic details on how the disease is passed on among individuals in various different ways, while making predictions about the state of the entirety of the population. However, the type and structure of the specific model considered typically depend on the size of the population under consideration. To analyse this effect, we study a family of effective epidemiological models in space and time that are related to each other through scaling transformations. Inspired by a similar treatment of diffusion processes, we interpret the latter as renormalisation group transformations, both at the level of the underlying differential equations and their solutions. We show that in the large scale limit, the microscopic details of the infection process become irrelevant, safe for a simple real number, which plays the role of the infection rate in a basic compartmental model.

q-bio.PE↗