Seminario di Fisica Teorica

This talk will cover key elements of the Electroweak (EW) sector of the Standard Model (SM). I will firstly review the underlying structure and general features of EW interactions, from the well known Spontaneous Symmetry Breaking (SSB) mechanism to the complex-mass scheme for the decay of weak gauge bosons. An overview of relevant related topics, such as the Goldstone Boson Equivalence Theorem (GBET), will also be discussed. Finally, I will briefly address the behavior of EW corrections at high energy. In this regime, one-loop EW corrections are logarithmically enhanced and in tail of kinematic distributions can yield correction factors of several tens of percent, reaching a similar size to the corresponding QCD ones. Thus, a very good control of these effects, and of remaining theoretical uncertainties, is crucial for the success of many physics endeavours at the LHC.

Seminario di fisica teorica

Since the proposal of the AdS/CFT correspondence, several examples of this conjecture involving branes wrapped on smooth Riemann surfaces $Sigma$ have appeared in the literature. In all these constructions, the $D=10,11$ supergravity solutions exhibit a boundary of the schematic form $AdS_{d+1}times M_{D-(d+1)}$ and a near-horizon geometry of the type $AdS_{d+1-n}times Sigma_ntimes M_{D-(d+1)}$, where $M$ is a compact manifold. After reducing the higher-dimensional theory on $M$, these solutions are interpreted as black branes in $AdS_{d+1}$ wrapped on $Sigma$. In this setup, supersymmetry is preserved via the so-called topological twist, which ensures that the supersymmetry spinor is independent of the coordinates on $Sigma$. A pivotal shift occurred with the work arXiv:2011.10579, which showed that branes could also be wrapped on orbifolds (specifically, the spindle). This breakthrough revealed that supersymmetry can be preserved in a completely novel way through the anti-twist, an orbifold generalization of the no-twist. Following this, significant efforts have been devoted to constructing similar and even more intricate solutions. Of particular interest is the case $d=1$, as the resulting metric is expected to correspond to the near-horizon limit of supersymmetric black holes in string theory. In the first part of this seminar, I will introduce the main characters of this game, with a focus on why black holes play a central role in the study of quantum gravity. I will then discuss my current research on spindles, with reference to arXiv:2210.16128, arXiv:2402.08724 and arXiv:2409.xxxxx.

seminario Colloquium

From the standpoint of physics, life is a mess. Biological phenomena cross spatial and temporal scales in a startling way, involving organisms that are greatly diverse at the structural and functional level. Amid this jumble, though, some connections with the physical and mathematical sciences often emerge, stirring hopes to partially extend to biology the predictive power of theoretical physics. To pursue this idea, though, the great diversity of biology needs to be drastically simplified. Physics is optimally suited for this task, rooted as it is on the idea that not all microscopic details are important, as only a couple of relevant variables are needed to describe a system. The tool physics uses to cut irrelevant details is the renormalization group. In 1972, Kenneth Wilson and Michael Fisher wrote a seminal paper titled “Critical Exponents in 3.99 Dimensions”, where they gave mathematical flesh to the idea that when we coarse-grain short-scale fluctuations the parameters of different models may flow towards the same fixed point ruling their large-scale behaviour, thus organizing into a handful of universality classes both statistical and quantum field theory. Can we use the renormalization group to describe the phenomena of life? Can we employ the same fundamental language to understand both the Higgs boson and a flock of starlings? In the field of collective behaviour the answer to this question seems to be positive. A unifying ingredient of collective biological systems is the presence of strong correlations: experiments in bird flocks, fish schools, mammal herds, insect swarms, and bacterial clusters find that the correlation length is significantly larger than the microscopic scales, a natural stepping stone to an RG analysis. In this talk I will provide a very simplified explanation of the renormalizationgroup (mostly using Google Maps) and then show how it can be applied to the study of natural swarms of insects, which are strongly correlated systems obeying dynamic scaling with an experimental dynamical exponent z=1.37 +/- 0.11. A one-loop RG calculation that takes into account both off-equilibrium activity and inertial dynamics gives z=1.35, a value remarkably close to the experimental exponent. This is the first positive test within biophysics of an RG prediction, hence strengthening our hopes that the renormalization group and its most fruitful consequence – universality – may have an incisive impact also in biology.

seminario di fisica teorica

Abstract:

What is the most general internal symmetry a Quantum Field Theory can have? The answer to this question has significantly changed in the past decade, with the understanding of generalized symmetries such as non-invertible and p-form symmetries. An orthogonal direction, which so far has been unexplored, is that of quantum groups; these are some exotic symmetry algebras which are well known to play a role in lattice systems, some of which are critical, and should therefore play a role in two dimensional Conformal Field Theory. I will discuss this question in the case of the simplest quantum group Uq(sl2), giving both the general picture and studying a specific example arising from the continuum limit of a lattice model. I will discuss the consequences of this symmetry, and how this is related to ordinary theories (e.g. minimal models) where quantum groups are known to appear somehow indirectly.

Abstract:

The interpretation of hadron collider, such as the LHC, data, and the assessment of possible hints of new physics, require the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). In this talk, I present a systematic methodology designed to determine whether and how global PDF fits might inadvertently ‘fit away’ signs of new physics in the high-energy tails of the distributions. I showcase a scenario for the High- Luminosity LHC, in which the PDFs may completely absorb such signs of new physics, thus biasing theoretical predictions and interpretations. I discuss strategies to single out the effects in this scenario and disentangle the inconsistencies that stem from them. A first solution I discuss is the exploration of the synergy between the high luminosity programme at the LHC and present and future low-energy measurements of large-sea quark distributions. A second one, is to fit simultaneously the PDFs and the new physics signals, which can be done using our publicly released open-source tool SIMUnet.

Seminario physics colloquium

Seminario di fisica teorica

Seminario di fisica teorica

Seminario di fisica fenomenologia

Seminario Physics Colloquium