Seminario di Fisica Teorica

Active matter encompasses systems that are not in equilibrium, consisting of elements that either consume energy or exert work. Consequently, their macroscopic characteristics diverge significantly from those predicted by continuum field theories based on equilibrium statistical mechanics. Recent advancements in active matter research have prompted a reevaluation of the fundamental principles of materials science. This has led to the development of a novel theoretical framework known as odd(visco)elasticity. Traditional elasticity treats solids as continuous media that change shape in response to external forces. On a microscopic scale, applying force to a crystalline structure displaces its atoms, which then exert a counterforce to regain the crystal’s original configuration. However, this dynamics is fundamentally altered in active odd materials, where the response to applied forces includes not only compression or deformation but also deflection. In this presentation, I will provide an overview of the recent advancements in this field.

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Seminario Fisica Teorica

The axion is a hypothetical particle that could explain the absence of CP violation in QCD and has a very rich cosmological phenomenology.

In particular a population of thermally produced axions is expected to exist, in addition to a cold dark matter population. I discuss a new conservative bound on the axion mass, from production in the early universe from scattering with pions. In addition I will show that to exploit the reach of upcoming cosmological surveys, non-perturbative calculations above the QCD crossover are needed. Moreover I will also review production from other Standard Model particles (quarks, leptons).

Then, I will discuss the axion cold dark matter population, showing that its abundance depends on non-trivial evolution during primordial inflation.

Finally I will discuss the non-standard case of a heavy QCD axion, which could give rise to a detectable gravitational wave signal at Pulsar Timing Arrays or at interferometers.

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Seminario Fisica Teorica

Several simple criteria were proposed to assess if vacua emerging from an effective scalar field theory are part of the string “landscape” or “swampland”. However, there has been little attempt to examine the swampland criterion against explicit context of kinetic terms made up of scalar fields. In this presentation, we discuss the universal behavior that in the region wherein the moduli are expected to be stable, the theory of gravity may be part of the landscape. By contrast, in the region where they may be faithful runaway potential, in the sense they possess a finite kinetic term for scalar field, the theory should thus be part of the swampland. We also consider the inflationary scenario interpolating between the cosmological landscape and the swampland and establish the part of the domain of existence where the swampland criteria are violated.

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Seminario di Fisica Teorica

The Bekenstein-Hawking entropy of supersymmetric AdS5 black holes is matched holographically via the Legendre transform of the superconformal index on the second sheet. In this talk I shall show how this approach can be extended to account for subleading corrections to the Bekenstein-Hawking entropy, which are computed in the gravity side by adding suitable higher-derivative corrections. After reviewing the universal case studied in 2208.01007 (and 2304.06101), I will focus on ongoing work aimed to understand the case in which the black hole is charged under additional flavor symmetries.

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Seminario Fisica Teorica

The holographic duality provides an explicit reduction of quantum field theory (QFT) calculations in the semiclassical large-N limit to sets of “gravitational” differential equations whose analysis can reveal all details of the spectra of thermal QFT correlators. In the first part of my talk, I will discuss the state of affairs in our understanding of thermal spectra from the point of view of hydrodynamics, kinetic theory as well as perturbative QFTs and, finally, holographic QFTs. Then, I will discuss how, in spectra with analytic properties that appear in holography, a complete reconstruction of the spectrum and of the corresponding correlator is possible from only the knowledge of an infinite, discrete set of pole-skipping points (a “0/0” in the associated correlation function) traversed by a single (hydrodynamic) mode. The main step that will enable a unique reconstruction will be a series expansion of the problem in an inverse number of spacetime dimensions, expanded around infinity. Conceptually, this reduces the computation of a QFT correlator spectrum to performing a set of purely algebraic manipulations.

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Semina di Fenomenologia delle Particelle Elementari

Over a decade after the Higgs discovery, the hunt for physics beyond the Standard Model is incorporating more and more searches for small, non-resonant traces of new physics, that can be described by an Effective Field Theory (EFT).

The so-called Standard Model EFT (SMEFT) is now the standard framework used for these searches. The Higgs EFT (HEFT) is an alternative extension of the SM, which differs from SMEFT in the representation chosen for the scalar fields, a feature that results in a higher complexity and that, so far, has made HEFT less attractive for phenomenological studies.

Nevertheless, it is well-established that HEFT is more general than SMEFT, implying the existence of BSM scenarios which would be captured by the former but not by the latter. HEFT could also represent a useful candle to test the validity of the dimension-6 SMEFT approximation, an issue that has been raising significant concerns for LHC measurements.

After an introduction to the two frameworks, the first half of the talk will give an overview of the phenomenological characterization of HEFT and SMEFT. The second part will explore more formal aspects of the HEFT-SMEFT interplay, that build on a geometric description of the scalar sector.

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Seminario di Fenomenologia delle Particelle Elementari

The production of a top quark pair in association with a heavy boson is a class of processes of high importance at LHC, both for precision Standard Model studies and new physics searches: top-pair production in association with a Higgs boson allows for a direct measurement of the top-quark Yukawa coupling, while the cross section of top-pair production in association with a W boson has been observed consistently higher than the Standard Model value by different experimental collaborations.

In this talk we present our recent computation of the NNLO QCD corrections to both these processes, with an emphasis on their phenomenological applications.

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Physics Colloquia

I will review constraints on dark matter nature like, i.e. the dark matter free streaming, in the context of structure formation by using hydrodynamical simulations and observational data sets. In particular, I will focus on ordinary matter that does not shine in between galaxies: the intergalactic medium.

I will show that the most competitive constraints on warm dark matter (with a non-negligible free streaming) can be obtained from the main manifestation of the intergalactic medium, the so-called Lyman-alpha forest produced by neutral hydrogen in the filamentary cosmic web.

Moreover, I will show quantitative constraints on neutrino masses, comment on other dark matter scenarios (scalar dark matter, dark matter interacting with baryons or radiation) and assess the prospects of 21cm intensity mapping in addressing dark matter nature.

Seminario Fenomenologia delle Particelle

Investigating neutrino physics through observations of the Universe is crucial for addressing open questions in both cosmology and particle physics.

After reviewing current cosmological constraints on neutrino properties, I will show the potential of forthcoming large-scale structure data from the ESA Euclid mission to detect the neutrino mass sum and provide insights into the existence of light particles beyond the Standard Model.

I will also discuss how non-standard neutrino interactions, which may help to resolve the Hubble constant tension, can be constrained with future cosmological data.

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Seminario di Fenomenologia delle particelle

Abstract:

Exotic hadron spectroscopy is a hot field since it has experienced a very productive period in the past 20 years, especially in the last years, in which new discoveries and/or new evidences of exotic states are published every three-four months. The outlook for the coming decades is that it will continuously grow thanks to the increasing interest from both the theoretical and the experimental sides of the scientific community, as witnessed by the large amount of literature on this field.

In the first part of the talk, some of the main experimental findings and theoretical predictions given before the experimental discoveries, regarding fully charm tetraquarks and pentaquarks, will be presented and discussed.

In the sector of fully charm pentaquark states, I will provide an outline of both the compact pentaquark description [1] and the description based on the coupling between the meson-baryon channels and the 5-quark core channels for the nonstrange [2,3] and the strange sector [4], and I will compare the predictions of these models with the experimental data.

In the sector of fully charm and fully bottom tetraquarks, I will present the calculation of $0^++$ and $2^++$ fully heavy tetraquark decay widths and branching ratios within the vector meson dominance model in the fully bottom [5] and fully charm sector [6] and compare the results with the recent experimental data.

In the second part of the talk, I will show a new method to compute the virtual contributions in KT-factorization [7,8]. As I will explain, this new formalism is a fundamental step to bridge the gap between the lowest order calculations and the NLO corrections in hybrid kT-factorization, thus being relevant for a more precise description of the experimental data in the rich field of forward physics.

[1] E. Santopinto and A. Giachino, Phys. Rev. D 96, 014014 (2017).

[2] Y. Yamaguchi, A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi and M. Takizawa, Phys. Rev. D 96, 114031 (2017)

[3] Y. Yamaguchi, H. Garcìa-Tecocoatzi, A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi and M. Takizawa, Phys. Rev. D 101, 091502 (2020).

[4] A. Giachino, A. Hosaka, E. Santopinto, S. Takeuchi, M. Takizawa, Y. Yamaguchi, Phys. Rev. D 108, 074012 (2023).

[5] C. Becchi, A. Giachino, L. Maiani and E. Santopinto, Phys. Lett. B 806, 135495 (2020)

[6] C. Becchi, J. Ferretti, A. Giachino, L. Maiani and E. Santopinto, Phys. Lett. B 811, 135952 (2020).

[7] E. Blanco, A. Giachino, A. van Hameren, P. Kotko, Nucl. Phys. B 995 (2023).

[8] A new subtraction scheme at NLO exploiting the privilege of kT-factorization, A. Giachino, A. van Hameren and G. Ziarko, e-Print: 2312.02808, submitted to JHEP.

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