Searcharxiv⌕ Search

arXiv subjects

Stefano Nicotri

Publications and source records attributed to Stefano Nicotri.

At least 19 recordsLinked to original sources
arXiv2026

Vector-meson properties in a data-driven AdS/QCD model

We investigate the properties of $ρ$, $ψ$, and $Υ$ mesons within a holographic AdS/QCD framework, capturing both their vacuum phenomenology and in-medium dynamics. By reconstructing flavor-specific gauge kinetic functions within a model originally developed to study thermodynamic functions, we compute the vector-meson mass spectrum, the decay constants and the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon at zero temperature. Furthermore, we evaluate the thermal spectral functions to analyze mass shifts, resonance broadening, and the melting of vector bound states in a hot and dense medium. Finally, using the Kubo formula, we extract the electrical conductivity of the plasma as a function of temperature and chemical potential.

hep-ph↗
arXiv2025

Data-Driven Refinement of an Analytical Holographic Model for the QCD Phase Transition

Using (2+1)-flavor lattice QCD data, we refine the parameters of an analytical holographic model via gradient descent optimization to precisely locate the critical endpoint in the $T-μ$ plane. Specifically, we calibrate the model using input data for the speed of sound at $μ_B = 0$, the second-order baryon number susceptibility $χ^B_2$, and the baryon number density at $μ_B/T = 1$. With these parameters fixed, we calculate pressure and energy density versus temperature at small chemical potentials and compare the results with lattice QCD data using Taylor expansion techniques. This comparison validates the robustness of our model upon extension to finite chemical potentials, as the results show broad consistency with lattice QCD data in this regime. Finally, we employ the calibrated model to determine the coordinates of the critical endpoint in the $T-μ_B$ plane, finding it located at $(μ_B = 0.678 \, \rm{GeV}, T = 0.110 \, \rm{GeV})$

hep-ph↗
arXiv2025

Out-of-equilibrium chiral condensate in AdS/QCD

We study the chiral condensate at finite temperature in AdS/QCD in a time-dependent background, in which the position of the black-hole horizon $z_h$ changes with time, producing an increasing or decreasing temperature. Conformal invariance is broken, as in the soft-wall model, by a static quadratic dilaton. Two different scenarios are analysed: in the first a general power-law time dependence is assumed for $z_h$, while in the second the energy-momentum tensor at late times reproduces the one found in viscous hydrodynamics. Depending on the rate at which the system evolves, the transition shifts toward lower temperatures. If the chiral condensate is far from equilibrium at low temperatures, oscillations around its equilibrium value are observed before thermalization. A prethermalization stage is found in the chiral limit if the initial condition is set at a temperature close to the critical one. In the hydrodynamic setup the evolution of the medium is slow enough, and the chiral condensate soon matches the equilibrium curve.

hep-ph↗
arXiv2024

Hadronic light-by-light scattering contributions to $(g-2)_μ$ from axial-vector and tensor mesons in the holographic soft-wall model

We compute the light axial-vector and tensor meson two-photon transition form factors in the soft-wall holographic model of QCD in the flavor-symmetric case. They are used to evaluate the axial-vector and tensor meson contributions to the anomalous magnetic moment of the muon via the hadronic light-by-light scattering process. As expected, these contributions are smaller than the one from pseudoscalar mesons. The result for axial-vector mesons is higher than the value found in other approaches.

hep-ph↗
arXiv2023

$π^0, η, η^\prime$ two-photon transition form factors in the holographic soft-wall model and contributions to $(g-2)_μ$

We compute the two-photon transition form factors of the light pseudoscalar $π^0$, $η$ and $η^\prime$ mesons in a soft-wall holographic model of QCD with a solution of the $U(1)_A$ problem. We compare the results with the experimental data in different ranges of photon virtualities. The obtained transition form factors are used to determine the $π^0$, $η$ and $η^\prime$ pole terms in the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon.

hep-ph↗
arXiv2021

$U(1)_A$ axial anomaly, $η^\prime$, and topological susceptibility in the holographic soft-wall model

The singlet pseudoscalar sector of light mesons is investigated in the soft-wall model, a bottom-up approach to the AdS/QCD correspondence. The $η^\prime$ mass results from the mixing among the fields dual to the axial current, pseudoscalar current and the $G\tilde G$ operator. The topological susceptibility is computed for any quark mass, and the Witten-Veneziano relation is obtained in the large $N_c$ limit.

hep-ph↗
arXiv2016

Role of nonlocal probes of thermalization for a strongly interacting non-Abelian plasma

We use a holographic method to investigate thermalization of a boost-invariant strongly interacting non-Abelian plasma. Boundary sourcing, a distorsion of the boundary metric, is employed to drive the system far from equilibrium. Thermalization is analyzed through nonlocal probes: the equal-time two-point correlation function of large conformal dimension operators in the boundary theory, and Wilson loops of different shapes. We study the dependence of the thermalization time on the size of the probes, and compare the results to the ones obtained using local observables: the onset of thermalization is first observed at short distances.

hep-ph↗
arXiv2015

Complex networks and public funding: the case of the 2007-2013 Italian program

In this paper we apply techniques of complex network analysis to data sources representing public funding programs and discuss the importance of the considered indicators for program evaluation. Starting from the Open Data repository of the 2007-2013 Italian Program Programma Operativo Nazionale 'Ricerca e Competitività' (PON R&C), we build a set of data models and perform network analysis over them. We discuss the obtained experimental results outlining interesting new perspectives that emerge from the application of the proposed methods to the socio-economical evaluation of funded programs.

physics.soc-ph↗
arXiv2014

Temperature and chemical potential dependence of the gluon condensate: a holographic study

The lowest dimensional gluon condensate $G_2$ is analyzed at finite temperature and chemical potential using a holographic model of QCD with conformal invariance broken by a background dilaton. Starting from the free energy of the model, the thermodynamical quantities needed to determine the $T$ and $μ$ dependence of the gluon condensate are evaluated. At high temperature the gluon condensate is independent of chemical potential. Moreover, at $μ=0$ and in the string frame, the temporal and spatial Wilson loops at low temperature are computed; they are related to the (chromo) electric and magnetic components of $G_2$, respectively. The $T$-dependence of the two components is separately determined.

hep-ph↗
arXiv2012

Anomalous $AV^*V$ vertex in the soft-wall holographic model of QCD

We discuss the vertex function of two vector and one axial-vector operators in the soft-wall holographic model of QCD. When one of the two vector currents represents an on-shell soft photon, such a vertex is described by two structure functions $w_L$ and $w_T$, which are usually calculated through triangular loop diagrams. We evaluate these functions in the soft-wall model of holographic QCD (HQCD) and compare the outcome to the QCD findings.

hep-ph↗
arXiv2012

On the Son-Yamamoto relation in the soft-wall holographic model of QCD

We study the vertex function of two vector and one axial-vector operators in the soft-wall holographic model of QCD. In particular, we discuss the possible relation, introduced by Son and Yamamoto, between the structure function $w_T$ describing such a vertex when one of the two vector currents represents an on-shell soft photon and the the two-point $Π_\perp^{VV}-Π_\perp^{AA}$ correlation function.

hep-ph↗
arXiv2012

Temperature and quark density effects on the chiral condensate: an AdS/QCD study

We investigate the dependence of the chiral condensate $<\bar qq>$ on the temperature and quark density using the soft-wall holographic model of QCD, adopting geometries with black holes at finite temperature and quark chemical potential $μ$. We find that, for $μ$ below a critical value, increasing the temperature the condensate decreases and vanishes at a temperature $\tilde T\simeq 210$ MeV (at $μ=0$). An analogous behaviour is observed increasing the chemical potential at fixed temperature. These results agree with the findings obtained by other methods. We also comment on the robustness of the results if geometries not involving black holes are adopted at low temperature, and an Hawking-Page transition is implemented.

hep-ph↗
arXiv2012

In-medium hadronic spectral functions through the soft-wall holographic model of QCD

We study the scalar glueball and vector meson spectral functions in a hot and dense medium by means of the soft-wall holographic model of QCD. Finite temperature and density effects are implemented through the AdS/RN metric. We analyse the behaviour of the hadron masses and widths in the $(T,μ)$ plane, and compare our results with the experimental ones and with other theoretical determinations.

hep-ph↗
arXiv2011

Holography, Heavy-Quark Free Energy, and the QCD Phase Diagram

We use gauge/string duality to investigate the free energy of two static color sources (a heavy quark-antiquark pair) in a Yang-Mills theory in strongly interacting matter, varying temperature and chemical potential. The dual space geometry is Anti-de Sitter with a charged black-hole to describe finite temperature and density in the boundary theory, and we also include a background dilaton field to generate confinement. The resulting phase diagram in the chemical potential-temperature $μ-T$ plane is in a quite good agreement with lattice results and effective models of QCD.

hep-ph↗
arXiv2010

Phenomenology Of The Holographic Soft-Wall Model Of QCD With "Reversed" Dilaton

We study the phenomenology of the recently proposed modified version of the Soft-Wall model of holographic QCD with a negative dilaton profile. We investigate vector and scalar mesons, evaluating mass spectra, decay constants and two-point correlation functions. We then study chiral symmetry breaking and compute the coupling of a scalar meson with two pseudoscalars. Finally, we compare the results with the ones found in the literature in the positive-dilaton case.

hep-ph↗
arXiv2009

Holographic scalar mesons

A holographic description of scalar mesons is presented, in which two- and three-point functions are holographically reconstructed. Mass spectrum, decay constants, eigenfunctions and the coupling of the scalar states with two pseu- doscalars are found. A comparison of the results with current phenomenology is discussed.

hep-ph↗