After a 5-year-long stop sadly imposed by COVID, we are happy to give a new fresh start to the famous series of Italian National Meetings on Theoretical Physics known as "Convegni Nazionali di Fisica Teorica” in Cortona, Tuscany. Resting on a very long tradition, this bi-annual Conference has historically been a prestigious meeting point of the Italian community of theoretical physics.
The aim of the Conference is to discuss some of the most recent and exciting advances in many areas of theoretical physics, in the pleasant early-Fall atmosphere of a pretty Tuscan hill. The informal environment and the intimate location will facilitate a fruitful exchange between senior and junior colleagues. Indeed, good attendance of young researchers, including graduate students and postdoctoral fellows, alongside senior researchers, has always been the trading mark of this Conference.
The program will feature plenary sessions with invited talks by Italian experts in the research areas of interest of INFN, and contributed talks by junior participants. The schedule includes free time for spontaneous discussions which the organizers strongly encourage to continue over a good Tuscan-style dinner in the beautiful center of Cortona.
In this talk I will show that the main properties of the fracton quasiparticles can be derived from a generalized covariant Maxwell-like action. Starting from a rank-2 symmetric tensor field, a partially symmetric rank-3 tensor field strength can be built, which obeys a kind of Bianchi identity. The most general action invariant under the covariant “fracton” transformation consists of two independent terms: one describing Linearized Gravity (LG) and the other referable to fractons, a proof of the always suspected relation between fractons and gravitons. I will also discuss that, as claimed in the Literature, the fracton part can be reconduced to a generalized Maxwell theory. In particular, in the covariant generalization of the fracton theory, the equations describing the fracton limited mobility, i.e. the charge and dipole conservationS, are not external constraints, but rather consequences of the field equations of motion, hence of the invariant action and, ultimately, of the fracton covariant symmetry.
Within the cell nucleus of eukaryotic organisms, chromosomes are organized in a complex, non-random three-dimensional (3D) spatial structure, which is intimately linked to vital functional purposes. Indeed, a correct folding allows an efficient communication between genes and their distal regulatory elements while, if altered, can cause severe diseases. Here I will discuss how Polymer Physics, combined with Molecular Dynamics simulations and Machine Learning based inference, represent a powerful tool to quantitatively investigate the complexity of 3D organization of real genomes, as highlighted by recent microscopy and biochemical experiments. I will show that simple physical processes, widely studied in Statistical Mechanics, such as phase-separation of molecular aggregates and coil-globule polymer transitions, allow us to make sense of recent experimental observations including the tissue-specific DNA structure and the variability of chromatin at the single cell level. Finally, polymer models can be used to study the impact of disease-linked genetic mutations or the effect of viral infections as SARS-CoV-2, opening the way to new potential tools in Biomedicine.
Obtaining accurate predictions for quantum theories is of paramount importance. Perturbation series are often divergent and non Borel summable, making the problem challenging.
Here we further explore exact perturbation theory (EPT) in quantum mechanics, first proposed in [Serone '17]. In this context, we can compare EPT with the well established exact wkb (EWKB) method. For bounded systems, there are different ways of implementing EWKB which can lead to different quantization conditions, and we show that a clever choice gives Borel summable perturbative series.
This procedure is the hamiltonian counterpart of EPT, which manipulates path integrals. It underpins EPT and it allows us to prove Borel summability.
Monopoles are a generic prediction of many UV completion of a U(1) gauge theory and, more importantly, might be part of our physical world.
Surprisingly the scattering of an s-wave massless fermion on a massive monopole is a subtle (and puzzling) problem.
In a vector-like theory, the solution is the Callan-Rubakov effect, which saves unitarity and gauge charge conservation, breaking the anomalous U(1) global symmetries.
In a chiral U(1) gauge theory, the problem is worse, as there are no out-going (multi) particle states in the 2d effective theory that describe the scattering that allows conserving all the gauge charges of an in-going particle, scattering on the monopole, leading to a unitarity puzzle.
In this talk, I analyze a
chiral gauge theory that has a UV completion in terms of an asymptotically free chiral SU(N) gauge theory, allowing us to compute concretely the answer to many questions.
For example, a feature of this model is the existence of a long-range condensate around the monopole that breaks part of the U(1) gauge symmetries, along with some of the global symmetries.
We hope that by studying this concrete example, we can guide others to more systematic approaches (e.g. Boundary CFT ones, where one classifies all the consistent boundary conditions of the 2d CFT), or find loopholes with them.
We use general assumptions of the unknown UV theory to constrain the IR physics of photons. Specifically, we can consider causality and unitarity of the S-matrix to set up a bootstrap problem. By solving it with numerical optimisation methods, we obtain the allowed EFT coefficients which are consistent with a unitary and causal UV completion.
I will discuss some theoretical and phenomenological implications of a string theory-inspired, cosmological phase of kination, dominated by the kinetic energy of a rapidly rolling scalar. In the first part of the talk, I will argue how such a kination epoch can naturally arise in string compactifications after inflation, focusing on the case where it is driven by the volume modulus. I will also show how a phase of volume kination for approximately no-scale vacua can be uplifted to a classical Kasner solution in 10d where the non-compact dimensions collapse towards a Big Crunch, in contrast with the standard picture of decompactification limits. This is suggestive of the existence of a "dynamical" Swampland, placing restrictions on the cosmological solutions allowed within String Theory. In the second part of the talk, I will describe how kination, together with other effects such as reheating from moduli decays, paints a very distinctive picture for a string-inspired, early universe cosmology. In particular, such a modified cosmological history leads to a different evolution of density perturbations and may be tested through small-scale structure observations.
In this talk I will discuss recent developments in the study of 3-point functions of chiral single-trace scalar operators in four-dimensional N=2
superconformal gauge theories. Using supersymmetric localization, it is possible to map the computation of these correlators to an interacting matrix model and obtain expressions that are valid for any value of the ’t Hooft coupling in the planar limit of the theory. In particular, I will focus on the strong-coupling regime, where these expressions allow us to compute the leading and subleading orders of the 3-point functions in an analytic way.
I will discuss the classification of 1-form symmetries in N=3
four dimentional SCFTs engineered in Type IIB in presence of an S-fold.
The charge lattice of the theories is obtained by analyzing
(p,q)-strings on the S-fold background. Then the line operators are determined via field-theoretical techniques, that I will explain. The 1-form symmetries and the possible global structures are determined for all N=3
S-fold SCFTs, and checked against recent results in the literature.
We shed light on the ultraviolet (UV) structure of the glueball effective action
to the next-to-leading large-N order in Yang-Mills (YM) theory
by effectively computing the UV asymptotics of a closely related object:
The generating functional of all the correlators of twist-2 operators
with maximal spin components.
We discuss several issues occurring in the above computation
that sets strong constraints on the nonperturbative solution
of large-N YM theory and it may be a pivotal guide for the search
of such a solution.
We perform the complete non-perturbative running of the flavour non-singlet tensor operator from hadronic to electroweak scales in Nf = 3 massless QCD, comparing four different definitions of the renormalisation constant. We use the same configuration ensembles of arXiv:1802.05243, subject to Schrödinger Functional (SF) boundary conditions, whereas we use valence quarks with (𝜒SF) boundary conditions, which results in O(a) improvement for observables after tuning of boundary counterterms. Following the recent ALPHA strategy, we exploit two different running couplings: at high energies (mu > ~ 2GeV) we use a SF-type coupling, while at low energies (mu < ~2GeV) a Gradient Flow (GF)-type coupling.
Radiative leptonic decays of the form P -> l nu gamma, where P
is a charged pseudoscalar meson and l a lepton, are interesting probes of New Physics beyond the SM. When the pseudoscalar P is heavy (e.g. for P=D, Ds, B) and the lepton l is light, the structure-dependent contributions to the decay rate are enhanced w.r.t. the point-like one by a factor (mp/ml)^2, making the corresponding decay rate very sensitive to the internal structure of the decaying meson. As a part of the Soton/RM123 collaboration program to provide an high-precision lattice QCD determination of the
P -> l nu gamma decay amplitude for all heavy mesons, we considered the case P=Ds
and computed the axial (FA) and vector (FV) form factors, which parameterize the
P -> l nu gamma amplitude, over the whole allowed phase space. Our calculation makes use of the gauge-field configurations produced by the ETM collaboration using Nf=2+1+1 flavours of Wilson-clover twisted-mass fermions at maximal twist. Our determination of the Ds=e ne gamma decay rate turns out to be much lower than existing model-dependent calculations, and well within the experimental bound set by the BESIII collaboration.
We propose a novel solution to the strong CP problem based on modular invariance. The latter is inherent to toroidal compactifications in string theory. We show that modular invariance allows for simple effective theories of flavour and CP where (i) the QCD angle vanishes, (ii) the CKM phase is large, (iii) quark and lepton masses and mixings can be reproduced up to order one coefficients. We implement such a general paradigm in supersymmetry or supergravity, with modular forms or functions, with or without heavy coloured states.
Spin observables yield a wealth of tests to our current understanding of
the nucleon internal structure. In particular, novel challenging
experimental data from Jefferson Lab have been published on the so-called
generalized spin polarizabilities, which quantify the spin-dependent
internal rearrangement of the nucleon probed by an external virtual photon.
We compute the resonance contribution to the nucleon spin structure
functions at low energy in the Witten-Sakai-Sugimoto model of holographic
QCD. Our analysis includes both spin 3/2 and spin 1/2 nucleon resonances
with positive and negative parity. We determine, in turn, the helicity
amplitudes for nucleon-resonance transitions and the resonance
contributions to the neutron and proton generalized spin polarizabilities.
Extrapolating the model parameters to realistic QCD data, our analysis
agrees with the observation that the ∆(1232) resonance gives the dominant
contribution to the forward spin polarizabilities at low momentum transfer.
As expected, the contribution of the ∆(1232) to the longitudinal-transverse
polarizabilities is instead negligible. Our analysis shows that different
spin 1/2 resonances give different contributions, in sign and magnitude, to
the generalized longitudinal-transverse spin polarizabilities.
I present an analysis of the inclusive Hb -> Xs gamma decay with Hb a beauty baryon, in particular Lambdab, employing an expansion in the heavy quark mass at
at leading order in alphas. For a polarized baryon I show the results for the distribution d2Gamma/dy/dcos(thetap), with y=2 Egamma/mb, Egamma the photon energy and thetap the angle between the baryon spin vector and the photon momentum in the Hb rest-frame. I discuss the correlation between the baryon spin and the photon polarization, and show how effects of physics beyond the Standard Model can modify the photon polarization asymmetry. I also present a method to treat the singular terms in the photon energy distribution.
In this talk I will present some recent developments in the calculation of the NLO QCD corrections for two gluon-initiated processes that are relevant for Higgs physics at the LHC, namely gg->ZH and gg->ZZ. The two-loop box diagrams with massive internal lines contributing to these amplitudes pose a technical challenge, and I will discuss their analytic calculation using a small-tansverse-momentum expansion, which also allows for a fast numerical evaluation of the QCD corrections.
At present the Large Hadron Collider at CERN is our only tool for direct exploration of physics at the electroweak (EW) scale and above and it proved to be a formidable machine for both searches of new heavy particles as well as precision studies at the EW scale. Nevertheless the next large-scale experiment in high-energy physics is likely to be a lepton collider and among the proposed options a multi-TeV muon collider (MuC) has the advantages of both proton-proton and electron-positron colliders, combining high energy reach with high precision measurements. Understanding the possibilities which such a machine may offer to study several processes and to search for new physics becomes then an important task. In particular processes involving collinear radiation emitted by the initial lepton (the muon or the anti-muon for the MuC, but the same holds for the electron and the positron too) can be factorized from the hard scattering process and a description in terms of parton distribution functions (PDFs) can be introduced, similarly to what is done in case of proton colliders and the parton content of a proton. Contrary to the latter, lepton PDFs (LePDFs) can be derived from first principles solving the corresponding DGLAP equations, with the complications of dealing with the full SM interactions and massive particles.
In this talk I will present our calculation of LePDFs [
]: after a brief review of the parton model for leptons and of our numerical strategy to solve the DGLAP equations, I will describe how the PDF evolution changes above the EW scale, focussing on the differences with the proton case: mixed PDFs, appearance of double logarithms and effects of the polarizations and masses of the particles. Then I will show our results and compare them with the so-called effective W approximation, which has been already used to study processes at MuC and is the only version of LePDFs implemented in computational softwares like MadGraph.
The talk is based on the following paper:
[1] F. Garosi, D. Marzocca and S. Trifinopoulos, LePDF: Standard Model PDFs for High-Energy Lepton Colliders, 2303.16964.
In view of the latest experimental results recently released by the ATOMKI collaboration, we critically re-examine the possible theoretical interpretation of the observed anomalies in terms of a new BSM boson X with mass ∼ 17 MeV. Employing a multipole expansion method, we estimate the range of values of the nucleon couplings to the new light state in order to match the experimental observations. Our conclusions identify the axial vector state as the most promising candidate, while other spin/parity assignments seem disfavored for a combined explanation.
One of the most intriguing signals beyond the Standard Model is the well-known discrepancy between the theoretical prediction of the muon anomalous magnetic moment amu=(g-2)mu/2 and its experimental value. However, the accuracy of the theoretical prediction is limited by the uncertainty on the Hadronic Leading Order (HLO) contribution amu^HLO. In this regard, the recently proposed MUonE experiment aims at providing a novel determination of amu^HLO through the study of elastic muon-electron scattering. The precision measurement of the differential cross section allows the determination of amu^HLO from the running of the electromagnetic coupling alpha(t) in the space-like momentum region.
In this talk, I will present the MUonE project, discussing the theoretical calculations that are required to achieve a competitive measurement. In particular, the precision goal of 10 ppm on the differential cross section requires a next-to-next-leading order computation of the muon-electron scattering, which has to be matched to a QED parton shower. Furthermore, since the initial-state electrons are bound in a low-Z target, the background due to muon-nucleus interactions must also be taken into account. In order to provide a reliable simulation tool, both processes are currently under implementation in MESMER, a new Monte Carlo event generator for the MUonE experiment.
In this talk I will talk about two complementary ways to extend the Standard model and account for a possibly strongly coupled hidden or dark sector. I will highlight the theoretical framework used for both and the phenomenological signals expected and show how the two explore different mass scales – from 100 MeVs to 100 TeVs.
The first half of my talk will envisage the possibility that an SM-neutral dark sector couples to the SM via portals with dimension greater than five. Probing this dark sector directly in the scale-invariant regime allows us to construct a framework we deem model-agnostic. I will mostly focus on how such dark sectors can be probed via decay signals in neutrino detectors which are primarily used for neutrino oscillation measurements.
In the second half of my talk, I will instead focus on a class of strongly coupled vector-like GUT theories. Such theories can improve the gauge coupling unification in the SM and simultaneously give rise to an accidentally stable dark matter candidate – the dark baryon. I will talk about the parameter space in which the two aspects of the theory can be made realistic.
We illustrate a comprehensive study of the 2HDM+a coupled with Dark Matter, including constraints from collider and dedicated Dark Matter searches. We also illustrate the outcome analysis of the cosmic phase transitions and the gravitational wave spectrum that are implied by the model and show the prospects for observing the signal of such gravitational waves in near future experiments such as LISA, BBO or DECIGO.
Minerals are solid state nuclear track detectors - nuclear recoils in a mineral leave latent damage to the crystal structure. Depending on the mineral and its temperature, the damage features are retained in the material from minutes to timescales much larger than the age of the Solar System. The damage features from the fission fragments left by spontaneous fission of heavy unstable isotopes have long been used for fission track dating of geological samples. Laboratory studies have demonstrated the readout of defects caused by nuclear recoils with energies as small as ~1 keV. Using natural minerals, one could use the damage features accumulated over geological timescales to measure astrophysical neutrino fluxes (from the Sun, supernovae, or cosmic rays interacting with the atmosphere) as well as search for Dark Matter. Research groups in Europe, Asia, and America have started developing microscopy techniques to read out the nanoscale damage features in crystals left by keV nuclear recoils. The research program towards the realization of such mineral detectors is highly interdisciplinary, combining geoscience, material science, applied and fundamental physics with techniques from quantum information and Artificial Intelligence. In this talk, I will highlight the scientific potential of Dark Matter searches with mineral detectors and briefly describe status and plans of the Mineral Detection of Neutrinos and Dark Matter (MDvDM) community.
The shear viscosity to entropy density ratio, eta/s, is one of the quantities of central interest in quantum field
theories. Within the AdS/CFT correspondence, it has been conjectured by Kovtun, Son and Starinets that a
universal lower bound 1/4pi exists. We present a new perspective on this matter in the framework of analogue
gravity models, focusing on relativistic fluids with transonic flow. Quantum fluctuations at the acoustic horizon,
the fluid analog of the event horizon of a black hole, result in a thermal radiation of phonons, the sonic analog
of the Hawking radiation. Adopting a covariant relativistic kinetic theory, we describe the Hawking emission as a
dissipative process. Neglecting phonon’s self interactions, we find the saturation of eta/s. We connect the KSS bound
to the absence of a gap in the low energy spectrum of long-wavelength excitations.
The recent data releases by multiple pulsar timing array (PTA) experiments show
evidence for Hellings-Downs angular correlations indicating that the observed
stochastic common spectrum can be interpreted as a stochastic gravitational wave
background. We study whether the signal may originate from gravitational waves
induced by high-amplitude primordial curvature perturbations. Such large
perturbations may be accompanied by the generation of a sizeable primordial black
hole (PBH) abundance. We discuss in which scenarios the inclusion of
non-Gaussianities in the computation of the abundance can lead to a signal
compatible with the PTA experiments without overproducing PBHs.
We investigate the imprints of new long-range forces mediated by a new light scalar acting solely on dark matter. Dark fifth forces in general will modify the background evolution as well as the growth of density fluctuations. At the linear level, constraints are derived from CMB together with a full-shape analysis of the power spectrum as measured by BOSS. At the non-linear level, the presence of fifth forces induces violation of the equivalence principle in cosmological correlators. This is encoded in the breaking of consistency relations at tree level for the bispectrum, which could be directly tested with future galaxy surveys. Combining this information with the full shape power spectrum at one loop leads to an unprecedented sensitivity on dark fifth forces.
In single-flavor QCD, the low energy description of baryons as Skyrmions is not available. In this case, it has been proposed by Komargodski that baryons can be viewed as kinds of quantum Hall droplets, or “sheets”, charged under the baryon symmetry localized on their boundary.
These objects can be studied in the deconfined phase of holographic QCD. Within this setup, the axion can be regarded as the Goldstone boson of the breaking of the axial U(1)A acting on just an extra massless quark flavor condensing at a scale fa>>Lambda, where Lambda is the dynamical scale of the SU(N) Yang-Mills (YM) sector responsible for confinement. In the Post-Inflationary scenario, the abundance of axions depends on the decay pattern of axionic strings and domain walls (DWs). However, in this scenario, some DWs could not decay completely, due to the baryonic charge localized on their boundaries, i.e. on the axionic strings. The charged DWs describe at low energies the baryons composed by the extra quark flavor. Basic properties of these particles, such as spin, mass scale, and size are discussed. The corresponding charged axionic strings are explicitly constructed in the holographic model. I will conclude by discussing potential phenomenological applications to Dark Matter.