The paradigmatic geometrical observable is the macroscopic electric polarization P of a crystalline insulator: since the early 1990s it is known that P is a geometric phase of the ground-state wavefunction. The geometrical nature of several other observables has been elucidated over the years: most notably orbital magnetization and anomalous Hall conductivity. In some special cases a geometrical observable is quantized, and becomes therefore topological: extremely robust with respect to perturbations, and measurable in principle with infinite precision.

In this talk I will start explaining what “geometrical” means in quantum mechanics. Then I will outline the main features of P and of a few other observables.

The talk will be addressed to Master/PhD students as well as to researchers.

Leo Esaki was awarded the Nobel prize in physics in 1973 for his pioneering studies on electron tunnelling: he coined the term “do-it-yourself quantum mechanics” a couple of decades after that. Since then, our toolkit for implementing this concept has expanded exponentially, advancing our ability to fabricate physical objects embodying virtually any Hamiltonian. Today we term all this quantum technology. In this conversation I shall discuss some of the trends within the solid-state realm. I aim to highlight that all this has been driven by the continuous development of few basic concepts and how this is still hindered by the lingering classical mindset and language being used.

Titolo

Il problema delle radiazioni nell'esplorazione spaziale

Relatori

Ricardo Ramos e Mario Carante

Diretta youtube

https://www.youtube.com/@physics-unipv

Since its first observation in the early eighties, the W boson has always found a place in the research program of high-energy colliders. Within the Standard Model (SM) of particle physics, the W boson mass can be predicted from a few observables which have been now measured with high precision: comparing the SM prediction to a sufficiently accurate measurement of the W mass thus provides a consistency test of the model. However, the SM prediction could be broken by quantum corrections induced by new unknown fields, which would actually turn the consistency test into indirect evidence of new physics.

Unfortunately, a precise measurement of the W boson mass at colliders is also extremely challenging for a wealth of reasons, as it is also possibly implied by the neat tension between the two most-precise measurements to date. The CMS experiment at the LHC is now in the process of delivering a new measurement of the W mass. This will come as the result of an impressive amount of work done by researchers (and students!) who have been carefully ticking off all the items on a long task list over the past years. In this talk, a concise overview of the state of the art will be given, focusing on the challenges posed by the quest for precision at the LHC and on some of the solutions that have been worked out along the way.

Titolo

Il ruolo del fisico nella radiobiologia applicata

Relatore

Leonardo Lonati

Diretta youtube

https://www.youtube.com/@physics-unipv

The seminar will discuss the application of ideas borrowed from statistical mechanics in addressing two problems in finance.
In the first part, we discuss how it is possible to tackle portfolio optimisation using tools borrowed from the physics of disordered systems, and we show that a phase transition takes place when the ratio between the number of assets in the portfolio and the length of the time series used to estimate risk approaches a critical value: When time series become too short compared to the dimension of the portfolio, the in-sample estimated risk vanishes, while the out-of-sample risk remains finite. This leads to a diverging estimation error and large sample to sample fluctuations. The second part of the talk examines the propagation of shocks between financial institutions, an important aspect of systemic risk. Banks interact in a network of interbank exposures, such as interbank loans. If an institution defaults, its creditors will suffer a loss, which may lead some to default in turn, and cause subsequent losses to their creditors, and so on. We will discuss how the problem of modeling cascades of defaults can be understood in terms of the emergence of a giant component of vulnerable nodes in a network of interbank exposures.

This seminar aims to report on an ongoing project to develop Quantum Field Theory (QFT) in the context of non-smooth spacetimes. The motivation for studying such geometries stems from their appearance in many astrophysical models and generic solutions to Einstein´s Equation. I will introduce the key mathematical modifications required to adapt QFT to these geometries.

In this Colloquium, the state of the art and the new perspectives in the theoretical and experimental work on the quantum simulation of gravitational problems using condensed matter and optical systems, the so-called analog models of gravity, will be discussed.
It will start with a pedagogical presentation of the general concept of analog mode and a review of milestone theoretical and experimental works on Hawking emission of phonons from acoustic horizons in trans-sonic flows of ultracold atoms.
It will then proceed with an outline of a joint theoretical-experimental effort that is on-going at the BEC Center on false vacuum decay processes: I will present experimental evidence of the decay of an extended metastable state via the nucleation of spatially localised bubbles in a two-component atomic superfluid and I will highlight its connection to open questions in quantum field theory and cosmology.
The seminar will conclude with a presentation of on-going theoretical work on analog Hawking emission processes in quantum fluids of light and the promising perspectives for its experimental observation. In particular, an unexpected interplay between Hawking emission and the quasi-normal modes of the black hole will be discussed, as well as its anticipated consequences on the zero-point fluctuations of the gravitational field around astrophysical black holes.