We study the quadratic quasi-normal modes of a Schwarzschild black hole, which are perturbations originating from the coupling of two linear quasi-normal modes. As recent studies suggest, nonlinear effects in black hole perturbation theory may be crucial for accurately describing a black hole ringdown. We present a new class of "quadratic" quasi-normal modes at second order in perturbation...
The direct current (DC) memory is a non-oscillatory, hereditary component of the gravitational wave (GW) signal that represents one of the most peculiar manifestations of the nonlinear nature of GW emission and propagation. In this work, by transforming the results provided in Ebersold et al.[Phys.Rev.D 100 (2019) 8, 084043] in harmonic coordinates and quasi-Keplerian parametrization, we...
In the presence of a finite modular flavour symmetry, fermion mass hierarchies may be generated by a slight deviation of the modulus from a symmetric point. This small parameter governing charged-lepton mass hierarchies may also be responsible for the breaking of lepton number in a symmetry-protected low-scale seesaw. In this talk, I will illustrate the implementation and the phenomenological...
We critically reassess the Minimal Dark Matter model and propose new indirect detection signatures. Specifically, for the originally proposed accidentally stable SU(2) 5-plet, we compute the photon flux arising from Dark Matter Bound State Formation and Sommerfeld Enhancement, highlighting the appearance of several spectral lines. After analyzing the key features of this flux, we explore the...
If reheating occurs at sufficiently low temperatures (below $20 \,\mathrm{MeV}$), neutrinos—assuming they are populated only through weak interactions—do not have enough time to reach thermal equilibrium before decoupling. We present an updated analysis of cosmological models with very low reheating scenarios, including a more precise computation of neutrino distribution functions,...
In trace-free Einstein gravity, the energy-momentum tensor of matter is not necessarily conserved and so the theory offers a natural framework for interacting dark energy models with a constant equation of state w=−1. From the point of view of quantum gravity phenomenology, it has been argued that such violations of energy-momentum conservation might originate from discreteness at the Planck...
Axion-like particles (ALPS), radiated from a network of cosmic strings, may be a large part of Dark Matter (DM). In the era of precision Cosmology, it is possible to characterize the effect of such particles - which almost scale invariant distribution function spans many orders of magnitudes in momentum - on the observables. In this work, we employ the CLASS code and Planck 2018 data to place...
We show that nickel oxide, which is already a very promising target to look for sub-MeV dark matter scattering, can be employed to hunt axion dark matter, with masses in the meV range and couplings to electrons allowing them to potentially be QCD axions. We describe the interactions between axions and the collective excitations of nickel oxide in terms of a universal effective field theory,...
The Cosmic Microwave Background (CMB) provides a powerful tool for testing the existence of light particle species beyond the Standard Model (BSM). In particular, light relics produced via freeze-in are a common feature of models where new light degrees of freedom interact too weakly with the Standard Model (SM) plasma to achieve full thermalization in the early Universe. This talk focuses on...
In chaotic quantum systems the spectral form factor exhibits a universal linear ramp and plateau structure with superimposed erratic oscillations. The mean signal and the statistics of the noise can be probed by the moments of the spectral form factor, also known as higher-point spectral form factors. We identify saddle points in the SYK model that describe the moments during the ramp region....
I will explore some foundational aspects of supersymmetric field theories under the perspective of the Dressing Field Method (DFM), a new systematic tool to exhibit the gauge-invariant content of general-relativistic gauge field theories.
First, I will show that the gauge-fixing conditions typically used to extract the degrees of freedom of the Rarita-Schwinger spinor-vector and gravitino...
The Double Copy relations are a set of correspondences between (super) gravitational and (super) Yang-Mills theories which allow one to compute tree-level n-graviton scattering amplitudes from tree-level n-gluon ones. We try to extend this paradigm to the off-shell case by attempting the construction of the Lagrangian of N=1 Supergravity using an N=1 Yang-Mills theory and a non-supersymmetric...
We study the EFT of a Majorana massive spin-$\frac{3}{2}$ particle through consistency conditions derived from unitarity, causality and Lorentz invariance. We show that its mass cannot be parametrically lighter than the UV cutoff, unless all the interactions, both in the transverse and longitudinal sector, are tuned to gravity. Then we focus on the decoupling limit, which effectively projects...
In the last decades, the holographic principle has been a powerful ally in high-energy physics, both as a tool and as an insight.
I will present how holography can be used in the context of nonperturbative analysis of QCD-like theories, providing examples of confinement and phase structure. I will focus on instances that do not require strong analytical control and can thus be tackled...
The scattering of charged massless fermions on magnetic monopoles at low-energy in the s-wave presents a long-standing final state puzzle: it seems to be generally impossible to construct an outgoing state conserving all charges. Indeed, bosonizing the low-energy EFT, one is seemingly led to particles of fractional charge.
In this talk I describe this problem starting from a UV complete...
The rates of flavor-changing weak processes are crucial in determining the conditions of beta equilibrium in neutron stars and mergers, influencing the damping of oscillations, the stability of rotating pulsars, and the emission of gravitational waves. We derive a formula for these rates at nonzero temperature, to leading order in the Fermi coupling and exact in the QCD coupling. Utilizing a...
Higher-spin conserved currents and charges feature prominently in integrable 2d QFTs in flat space. Motivated by the question of integrable field theories in Anti de-Sitter space, we consider the consequences of higher-spin currents for QFTs in AdS2, and find that their effect is much more constraining than in flat space. Specifically, it is impossible to preserve: (a) any higher-spin charges...
In this talk, we extend the Variational Quantum Eigensolver (VQE) approach to improve the estimate of the ground state of a quantum system by minimizing the expectation value of a target Hamiltonian on a k-frame—a set of k linearly independent orthonormal states—that define a k-dimensional subspace within the full Hilbert space. This search is then supplemented by an exact diagonalization in...
Hydrodynamics is the effective field theory description of many-body systems close to thermal equilibrium at large distances and late times. The dynamics of these systems are governed by the conservation of energy, momentum and charge. However, in certain cases, e.g., when spatial translation invariance is broken, these hydrodynamic currents decay slowly rather than remain conserved,...
Fracton phases of matter constitute an interesting point of contact between condensed matter and high-energy physics. The limited mobility of subdimensional quasiparticles finds applications in different areas of theoretical physics, including quantum information, quantum field theory, elasticity, hydrodynamics and gravity. In our works we adopt a field theoretical approach to investigate...
Active Particles are physical entities able to transform energy from the environment or internal reservoirs into directed self-propelled motion. From a theoretical standpoint, in recent years this class of systems generated great interest in statistical mechanics due to the display of intriguing new properties as motility-induced phase separation [1], an inherent out of equilibrium character...
Active Brownian Particles (ABPs) are known to exhibit rich non-equilibrium behaviors.
The phase diagram shows two phase transitions: from a liquid state to a hexatic state, characterized by quasi-long-range orientational order and short-range translational order, and, at decreasing density, from a hexatic state to a solid state, where both orientational and translational order are...
We elaborate on the method of parametric annihilators for deriving relations among integrals. Annihilators are differential operators that annihilate multi-valued integration kernels appearing in suitable integral representations of special functions and Feynman integrals. We describe a method for computing parametric annihilators based on efficient linear solvers and show how to use them to...
The associated production of a top-antitop quark pair with a $W$ boson is one of the heaviest signatures probed at the LHC. The corresponding rates have been found to be consistently higher than the Standard Model predictions, calling for improved theoretical predictions.
In this talk I will discuss one of the main bottlenecks for the exact computation of the two-loop QCD amplitude, namely...
In order to match the increasing precision of modern particle colliders, it is essential to have accurate theoretical predictions for the cross sections of physical processes and their associated distributions. These predictions are often obtained via Monte Carlo event generators which combine the fixed-order calculation, computed as a perturbative expansion in the coupling constants, with a...
Recent experimental results from the Atomki collaboration have reported the observation of anomalous effects in Beryllium, Helium and Carbon nuclear transitions that could hint at physics beyond the Standard Model. However, the MEG-II experiment has recently found no significant anomalous signal in the Beryllium transition $^8$Be$^⋆$ → $^8$Be + $e^+e^-$. In view of this result, we critically...
It is well known that the Standard Model (SM) is not a complete theory, but rather an effective one, describing particle phenomenology in some energy range. Different ways of extending the SM have been formulated, among these there is the class of the so-called 331 extensions. These depend ona free parameter $\beta$.It is well known that 331 models with $\beta =\sqrt{3}$ predict the existence...
We consider models in which the Standard Model is extended with dark quarks that belong to fragments of vector-like representations of the grand-unifying group SU(5), and are charged under a new confining non-Abelian interaction. We consider both strongly-coupled and weakly-coupled régimes, corresponding to the dark quarks being lighter or heavier than the confinement scale, respectively. We...
The decay of a charmonium vector meson $c\bar c$ into the $\Lambda\bar\Sigma^0 + \mathrm{c.c.}$ state can be considered purely electromagnetic under the assumption of isospin conservation. The first-order interaction is therefore mediated by a virtual photon, similar to the non-resonant process $e^+e^- \to \Lambda\bar\Sigma^0 + \mathrm{c.c.}$ in the Born approximation. Given the nature of...
We study the renormalization and mixing of the $\Delta F=2$ Four-Fermion Operators (FFO), starting from the problem of the computation of the perturbative running for $N_\mathrm{f}=3$ and showing how this problem is solved through the use of the Poincaré-Dulac theorem. We then illustrate the procedure to evaluate the non-perturbative running from the hadronic scale ($O(\Lambda_{QCD})$) to the...
The inclusive hadronic decays of the $\tau$ lepton offer an alternative method for extracting the CKM matrix elements $V_{\mathrm{ud}}$ and $V_{\mathrm{us}}$. In this talk, I will discuss recent results from the ETM Collaboration on the inclusive hadronic decay rate of the $\tau$, obtained in $N_f=2+1+1$ QCD using the novel HLT method. This approach circumvents the well-known inverse Laplace...
We present our preliminary determinations of the $\Lambda$--parameter of $\mathrm{SU}(N=3,5,8)$ Yang--Mills theories and of its large--$N$ limit in the Twisted Gradient Flow renormalization scheme on the lattice. First, we determine $\Lambda$ in units of a low-energy renormalization scale $\mu_{\mathrm{had}}$ using the step-scaling method. Then, to express $\Lambda$ in units of the...
The fundamental theory of strong interactions, known as Quantum ChromoDynamics (QCD), exhibits rich symmetry properties that underlie the behavior of hadronic matter. In the limit of $N_f$ light quark masses, QCD possesses an approximate chiral symmetry $U(1)_V\otimes U(1)_A\otimes SU(N_f)_V\otimes SU(N_f)_A$. The special unitary part of this symmetry group is spontaneously broken to its...
The (in)famous $X(3872)$ was the first exotic particle discovered in 2003, compatible with a tetraquark interpretation. More than twenty years have passed since then, yet its internal dynamic remain an open question. Currently, the most established models describe the $X(3872)$ either as a compact tetraquark, where quarks interact via color forces, or as a $\bar{D}^0D^{0}$ mesonic molecule,...
We provide a new construction of superfield collinear twist-$2$ operators as infinite-dimensional, irreducible representations of the collinear superconformal algebra in the zero-coupling limit of $\mathcal{N}=1$ supersymmetric Yang-Mills (SYM) theory in a manifestly gauge-invariant and supersymmetric-covariant fashion.This construction makes manifest their mixing and renormalization...
