### Conference

#### Cortona Young 2021

###### Online Event

**Jun 09, 2021 - Jun 11, 2021**

**Abstract**

This is the second edition of the Cortona Young e-conference, hosted by GGI and meant to replace, during the Covid-19 pandemic, the Italian National Meeting New Frontiers in Theoretical Physics - Convegno di Fisica Teorica di Cortona.

This meeting is primarily addressed to young researchers (graduate students and postdocs) connected to the Italian community, and is meant to give visibility to their most recent exciting advances in all areas of theoretical physics.

The program consists of 14 selected plenary Zoom talks of 20'+5' spanned over three afternoon sessions, each with a 30' virtual-coffee break. A special committee will select the best seminar. In addition, we give the opportunity to present a 10' video-poster and to discuss with interested participants in virtual rooms during a dedicated session on Thursday morning (10:00 AM - 12:00 AM) and during the breaks. The video-posters will be evaluated by the organizing committee for publication on this web page and a certificate for the best video-poster will be awarded by the GGI (here you can find the list of video-posters).

Please use the apply link above to register or to submit a request for a seminar/video-poster.

The deadline for web-seminar applications is May, 7. The dead-line for uploading video-posters is May, 25.

**Selection Committee for the best web-seminar**

A.Bissi (Uppsala), A.Cappelli (Firenze), E.Lisi (Bari), F.Maltoni (Bologna), S.Matarrese (Padova), B.Mele (Roma), F.Sannino (Napoli and Odense), F.Zwirner (Padova) (chair)

**Speakers**

Claudio Bonanno (GGI Firenze)

Andrea Dei (Harvard Univ., Cambridge)

Nicola Andrea Dondi (Univ. of Bern)

Marco Fazzi (INFN Milano Bicocca)

Carlo Heissenberg (Nordita, Stockholm)

Giacomo Landini (Pisa Univ.)

Stefano Lanza (ITF, Utrecht Univ.)

Pavel Novichkov (SISSA, Trieste)

Chiara Paletta (Trinity College, Dublin)

Elena Pinetti (Torino & Sorbonne Univ.)

Rocco Rollo (GGI, Firenze)

Paola Ruggiero (Geneva Univ.)

Chiara Signorile-Signorile (Karlsruhe Inst. of Technology)

Christoph Andreas Ternes (INFN Torino)

**Organizers**

Anna Ceresole, Marialuisa Frau, Ezio Maina, Domenico Orlando, Marco Taoso, Roberto Tateo, Paolo Torrielli (UniTO, INFN-TO), Stefania De Curtis (INFN-FI & GGI).

**Local organizer**

Stefania De Curtis

**Contact**

decurtis@fi.infn.it

**Talks**

Date | Speaker | Title | Type | Useful Links | ||||
---|---|---|---|---|---|---|---|---|

Jun 09, 2021 - 14:15-14:30 | Welcome | Introduction | ||||||

Jun 09, 2021 - 14:30-14:55 | Elena Pinetti (University of Turin & Sorbonne University) |
Integral X-ray constraints on sub-GeV dark matter | Seminar |
Abstract
Dark matter (DM) in cosmic structures is expected to produce signals originating from its particle physics nature, among which the electromagnetic emission represents a relevant opportunity. In our work we proposed to study sub-GeV DM particles by looking at energies much lower than the mass of the sub-GeV DM particles. We included the contribution from Inverse-Compton scattering in the total flux. In particular, the electrons and positrons produced by DM particles give rise to X-rays by upscattering the low-energy photons of the radiation fields in the Galaxy (CMB, infrared from dust, optical starlight). These X-rays fall in the energy range covered by the INTEGRAL data, which we used to determine conservative bounds on the DM annihilation cross-section. We considered three annihilation channels: electron, muon and pion. As a result, we derived competitive constraints for DM particles with a mass between 150 MeV and 1.5 GeV. |
Slides | Video | ||

Jun 09, 2021 - 14:55-15:20 | Paola Ruggiero (University of Geneva) |
Quantum Generalized Hydrodynamics | Seminar |
Abstract
Physical systems made of many interacting quantum particles can often be described by Euler hydrodynamic equations in the limit of long wavelengths and low frequencies. Recently such a classical hydrodynamic framework, now dubbed Generalized Hydrodynamics (GHD), was found for quantum integrable models in one spatial dimension. Despite its great predictive power, GHD, like any Euler hydrodynamic equation, misses important quantum effects, such as quantum fluctuations leading to non-zero equal-time correlations between fluid cells at different positions. Focusing on the one-dimensional gas of bosons with delta repulsion, we reconstruct such quantum effects by quantizing GHD. The resulting theory of quantum GHD can be viewed as a multi-component Luttinger liquid theory. It describes quantum fluctuations of truly nonequilibrium systems where conventional Luttinger liquid theory fails. |
Slides | Video | ||

Jun 09, 2021 - 15:20-15:45 | Giacomo Landini (Università di Pisa) |
Accidental Dark Matter in gauge theories | Seminar |
Abstract
The 25% of our Universe is composed by non-baryonic matter generically known as Dark Matter (DM). The evidence of DM requires the existence of physics Beyond the Standard Model. We here extend the Standard Model (SM) with a new dark gauge group and eventually new scalar and fermionic fields minimally coupled to the SM sector. We show that gauge invariance can lead to interesting dynamics (such as confinement and spontaneous symmetry breaking) and possibly multiple phases. Furthermore, it leads to accidental symmetries, such as dark baryon numbers or discrete group parities, which provide accidentally stable DM candidates. We study the DM phenomenology in different models: we analyze the DM production mechanisms and provide predictions for direct and indirect searches. We show how this framework can also be applied to the solution of the Peccei-Quinn quality problem. |
Slides | Video | ||

Jun 09, 2021 - 15:45-16:15 | Coffee break and video-posters | Discussion | More Info | |||||

Jun 09, 2021 - 16:15-16:40 | Andrea Dei (Harvard University, Cambridge) |
AdS3 correlators from the worldsheet | Seminar |
Abstract
We revisit the computation of string worldhseet correlators on AdS3 with pure NSNS background flux. We solve all known symmetry constraints in multiple examples and for the first time provide a closed formula for 3 and 4-point functions with arbitrary winding. A non-trivial singularity structure emerges. In some cases, the full integral over the string moduli space can be performed analytically, leading to a direct contact with the dual CFT2. |
Slides | Video | ||

Jun 09, 2021 - 17:00-19:00 | Fabio Maltoni & Andrea Wulzer |
Focus Meeting "The Precision Potencial of the (HL-)LHC" | Seminar | |||||

Jun 10, 2021 - 10:00-12:00 | Video-poster session | Discussion | More Info | |||||

Jun 10, 2021 - 14:30-14:55 | Nicola Andrea Dondi (University of Bern) |
Resurgence of the large-charge expansion | Seminar |
Abstract
Observables in generic CFTs carrying a large global charge Q can be studied systematically in an expansion in 1/Q. In this talk, I will discuss the d=3 Wilson-Fisher O(N) CFT in a large-charge sector, where also N is taken to be large. The large-charge expansion of critical exponents of this model turns out to be an asymptotic series with double factorial growth. Resurgent methods can be applied to obtain an unambiguous semi-classical reconstruction of this expansion, containing non-perturbative contributions and allowing extrapolation to small charge values. The precise non-perturbative structure of the expansion is captured by a worldline path integral on the 2-sphere. In this purely geometrical picture, the large-charge result is reproduced via saddle-point expansion around (unstable) sphere geodesics, while Borel ambiguities are related to Morse indexes introduced by their negative modes deformations. |
Slides | Video | ||

Jun 10, 2021 - 14:55-15:20 | Christoph Andreas Ternes (INFN, Sezione di Torino) |
Short baseline oscillation anomalies and reactor experiments | Seminar |
Abstract
"Most observations in neutrino oscillation physics are well described within the three-neutrino paradigm. There are, however, some anomalies which might hint towards the existence of a fourth (and sterile) neutrino with eV-scale mass. I discuss the current status of searches for this type of neutrino at reactor experiments. I discuss the status of the rate anomaly and show that the preference for a sterile neutrino depends importantly on assumptions made on the reactor flux. Using the latest flux calculations measurements and predictions agree very well and the reactor anomaly disappears. Experiments which analyze the ratio of spectra measured at different positions of the detector do not suffer from the important dependence on the flux. I also discuss the current status of searches for sterile neutrinos at ratio experiments, setting particular focus on the recent results from the Neutrino-4 experiment." |
Slides | Video | ||

Jun 10, 2021 - 15:20-15:45 | Pavel Novichkov (SISSA, Trieste) |
Lepton Masses and Mixing from Residual Modular Symmetries | Seminar |
Abstract
A new bottom-up approach to the flavor problem based on modular invariance has been recently proposed and has gained considerable attention in the literature. In this talk, I will describe the construction of modular-invariant theories, introducing the relevant notions such as the modular group, the modulus field and the modular forms. I will then show that in modular-invariant models of flavor hierarchical fermion mass matrices may arise naturally due to the proximity of the modulus to a residual symmetry point. As a viable example, I will present a modular-invariant lepton model which is free from fine-tuning and consistent with both the observed hierarchy of charged lepton masses and large neutrino mixing. |
Slides | Video | ||

Jun 10, 2021 - 15:45-16:15 | Coffee break and video-posters | Discussion | More Info | |||||

Jun 10, 2021 - 16:15-16:40 | Carlo Heissenberg (Nordita, Stockholm) |
Gravitational waves from scattering amplitudes | Seminar |
Abstract
The classical limit of quantum scattering amplitudes offers a useful strategy to probe the interaction between colliding black-holes and to produce precision gravitational wave-forms, of relevance to Virgo and Ligo experiments. Amplitudes naturally probe the post-Minkowskian regime, where gravitational interactions are weak but velocities are not necessarily small, thus extending the more conventional post-Newtonian approximation scheme to all orders in the velocity. In this context, I will illustrate how the inclusion of radiation-reaction effects to the gravitational deflection angle obtained from two-loop amplitudes recently led to the resolution of a puzzle associated to the high-energy limit of massive scattering, whose behavior appeared to contradict previous results for massless scattering. |
Slides | Video | ||

Jun 10, 2021 - 16:40-17:05 | Stefano Lanza (ITF - Utrecht University) |
Strings at the End of the Swampland | Seminar |
Abstract
In any consistent effective field theory (EFT) of quantum gravity, limits of infinite field distance lead to the breaking of the effective description due to the appearance of an infinite tower of massless states. In this talk, I will show how this mechanism, which goes by the name of Swampland distance conjecture, is realized from a bottom-up approach, within 4D EFTs. The key objects to introduce are strings that are magnetically coupled to axions. I will first illustrate how the solitonic solutions induced by the strings can be employed to explore the field space of the theory. Then, infinite field distance limits are distinguished by the emergence of a tensionless string, signalling the breaking of the EFT. I will further show how the physical properties of such tensionless strings can be used to recover crucial information of the EFT. In particular, they constrain the maximal cut-off allowed by the EFT and fix the rate at which the tower of states that become massless. |
Slides | Video | ||

Jun 10, 2021 - 17:05-17:30 | Claudio Bonanno (GGI, Firenze) |
Large-N limit and theta-dependence from the lattice: 2d CP(N-1) models vs 4d SU(N) gauge theories | Seminar |
Abstract
"In this talk we will present new lattice results about theta-dependence in the large-N limit. The investigation of this topic with standard algorithms is plagued by topological freezing, thus we adopt the Hasenbusch algorithm, originally proposed for CP(N-1) models and here applied to SU(N) gauge theories for the first time, to dramatically improve large-N simulations. We observe large corrections to the large-N predicted behavior of CP(N-1) models, while SU(N) gauge theories are in good agreement with the large-N predicted scaling already for N>2. We argue that such difference could be related to the critical behavior of CP(N-1) models in the small-N limit N->2." |
Slides | Video | ||

Jun 11, 2021 - 14:30-14:55 | Chiara Paletta (Trinity College, Dublin) |
Integrable open quantum systems | Seminar |
Abstract
"The theory of open quantum system takes into account that in nature nothing can be isolated: a physical system interacts with the environment. If the response of the environment is Markovian, the time evolution of the density matrix of the system can be described by the Lindblad Master equation: dependent on the Hamiltonian H of the system and a jump operator L describing the coupling to the environment. By using the boost automorphism mechanism, I will show how to construct one-dimensional integrable Lindblad systems. In particular, I will show one model found by this method. This has very interesting physical features: the non-equilibrium steady state is a current carrying mixed state, it is an integrable example of the pumping effect and at a special point of the coupling constant the evolution of the diagonal of the density matrix is given by a linear operator equivalent to the TASEP generator (Markovian classical process)." |
Slides | Video | ||

Jun 11, 2021 - 14:55-15:20 | Chiara Signorile-Signorile (Karlsruhe Institute of Technology) |
Local Subtraction of Infrared Singularities in QCD | Seminar |
Abstract
In the era of high precision data from the LHC, new theoretical challenges define the frontiers of cutting-edge research in Particle Phenomenology. At an energy scale of 13TeV, an impressive agreement with the Standard Model (SM) predictions is observed. To test the potential presence of new physics, it is urgent to improve the calculation of well-known processes. One tool that moves in this direction is the development of QCD perturbation theory. In this context, the next-to-next-to-leading perturbative order is the unavoidable standard for fixed-order predictions. To achieve this level of accuracy, it is necessary to deal with infrared singularities, by introducing, for instance, a subtraction scheme. In this talk I will introduce the Torino scheme, discussing, in particular, its core structure and some technical aspects. |
Slides | Video | ||

Jun 11, 2021 - 15:20-15:45 | Marco Fazzi (INFN Milano-Bicocca) |
The Cardy-like limit of the | Seminar |
Abstract
We study the Cardy-like limit of the superconformal index of generic N=1 SCFTs with ABCD gauge algebra, providing strong evidence for a universal formula that captures the behavior of the index at finite order in the rank and in the fugacities associated to angular momenta. The formula extends previous results valid at lowest order, and generalizes them to generic SCFTs. We corroborate the validity of our proposal by studying several examples, beyond the well-understood toric class. We compute the index also for models without a weakly-coupled gravity dual, whose gravitational anomaly is not of order one. |
Slides | Video | ||

Jun 11, 2021 - 15:45-16:15 | Coffee break and video-posters | Discussion | More Info | |||||

Jun 11, 2021 - 16:15-16:40 | Rocco Rollo (GGI, Firenze) |
The fate of long modes in Cosmology | Seminar |
Abstract
By a careful implementation of gauge transformations involving long-wavelength modes, we show that a variety of effects involving squeezed bispectrum configurations, for which one Fourier mode is much shorter than the other two, cannot be gauged away, except for the unphysical exactly infinite-wavelength (k=0) limit. Our result applies, in particular, to the Maldacena consistency relation for single-field inflation, yielding a local non-Gaussianity strength fNLlocal = − (5/12)(nS−1) (with nS the primordial spectral index of scalar perturbations), and to the fNLGR = −5/3 term, appearing in the dark matter bispectrum and in the halo bias, as a consequence of the general relativistic non-linear evolution of matter perturbations. Such effects are therefore physical and observable in principle by future high-sensitivity experiments. |
Slides | |||

Jun 11, 2021 - 16:40-17:10 | Break (Panel Meeting) | Discussion | ||||||

Jun 11, 2021 - 17:10-17:30 | Cortona Young 2021 Award Ceremony | Discussion |