seminari 2024

1 Jan 2024, 00:00 → 30 Dec 2024, 02:00 Europe/Rome

412C (Room)

Stefania Vecchi (Istituto Nazionale di Fisica Nucleare)

Seminari di Fisica del Dipartimento e della sezione INFN

Tuesday, 9 January

11:00 → 12:00 Spider silks are like potatoes: so many possibilities

Spiders are often reviled, but their silks and webs are commonly viewed in awe and have fascinated humankind. From raising the interest of ancient philosophers to the practical outcomes in societies, spider silks have always been part of our culture and, thus, of our scientific development.
The “wow effect” for spiders and their silks initially comes from the good use that the animals make of these protein-based fibers to solve many challenges that were imposed by natural selection. How can a spider lift animals thousands of times heavier? How can spiders fly? How can spiders build structures that can even stop small birds?
Nature has designed silk to be produced at environmentally friendly conditions and to have exceptional mechanical and biological properties, reasons for which spider silks have deeply been investigated in these decades for their possible applications in biomedical technology, the textile industry, and soft electronics. Thus, this diversity in materials and structural applications makes spider silks' scientific outcomes potentially infinite. This seminar aims to delve into the recent discoveries related to spider silk, and the possibility of producing this material artificially at a scale compatible with industrial production using an environmentally friendly green protocol.

Speaker: Gabriele Greco (Uni Trento & Swedish Uni of Agricultural Sciences)

Thursday, 18 January

15:00 → 16:00 Lepton flavour violating decays into axion-like particles

Pseudo Nambu-Goldstone bosons — also known as axion-like particles (ALPs) — with flavour-violating couplings to the Standard Model (SM) leptons are a consequence of spontaneously-broken global U(1) symmetries within a wide class of models. In this seminar, I will present some explicit examples where such lepton-flavour-violating (LFV) ALP scenarios are realised. A general prediction thereof is the occurrence of flavour-violating decays of SM leptons into a light axion-like particle, which would typically escape detection at experiments searching for rare muon and tau decays. I will discuss the bounds set on this exotic signature by past experiments, as well as the prospects at upcoming searches for LFV muon and tau decays. I will focus in particular on a proposal for a modified setup of the MEG II experiment that would be maximally sensitive to an ALP coupling to right-handed leptonic currents. I will also compare the sensitivity of LFV experiments to the leptonic ALP couplings with astrophysical constraints, such as bounds from stellar evolution, and with the regions of the parameter space where the ALP constitutes a dark matter candidate.

Speaker: Lorenzo Calibbi (Nankai University, School of Physics, P. R. China)

Thursday, 8 February

14:00 → 15:00 Optical polarimetry of explosive transients

Polarimetry is a photon-starving technique which allows to extract geometrical information that cannot be obtained with any other method. In my seminar I will briefly review the basic concepts, present the application to explosive events (mainly on supernovae) and discuss the results obtained so far. I will also briefly go through the cases of kilonovae, other exotic transients and a recent application to the problem of the spinning axis tilt of a BH in a binary system.

Speaker: Ferdinando Patat (Observing Programmes Office - Head, European Southern Observatory)

Monday, 19 February

15:00 → 16:00 Geant4 simulations of applications of oriented crystals breaking down the challenges in accelerator physics, particle physics and space science Project TRILLION

Crystalline structure is a unique environment for strong-field QED effects involving both high-energy charged particles and photons. A small piece of crystal material aligned with the particle beam can be used as an intense source of X- and gamma-ray radiation, a positron source for future e+e- colliders, a beam manipulation instrument in accelerators and colliders, a compact crystalline calorimeter for high-energy physics experiments and gamma-ray space telescopes and a compact ultrahigh gradient plasma wake-field accelerator as well.
The Marie Skłodowska-Curie Actions Global Fellowships, Project TRILLION GA n. 101032975 is dedicated to steering and radiation effects in oriented crystals and their applications implementation into Geant4.
In this seminar various applications of the new Geant4 model of electromagnetic effects in oriented crystals mentioned above will be presented.

Speaker: Alex Sytov (Marie Curie Fellow, UniFe)

Tuesday, 5 March

15:00 → 16:00 Decoding solar complexity: small-scale phenomena impacting upper atmospheric processes

Recent advancements in solar instrumentation have revolutionized our ability to study solar phenomena, particularly at small spatial scales and high temporal resolutions. These tiny features play a pivotal role as fundamental building blocks for myriad processes from the photosphere to the upper layers of the solar atmosphere. This presentation delves into observational evidence showcasing the intricate interplay between small-scale magnetic flux emergence, magnetic concentrations, and convective plasma flows in the photosphere. We use multi-wavelength time series data from ground-based and space-borne solar telescopes to elucidate the complex dynamics underlying solar activity and its implications for the broader understanding of solar phenomena.

Speaker: Prof. Santiago Vargas Domínguez (University of Colombia)

Monday, 25 March

11:30 → 12:30 Small scale CMB (and foregrounds) cosmological information.

Analysis of CMB primary temperature and polarisation anisotropies of recent experiments provide the tightest constraints on cosmological parameters. A crucial step of this analysis is the modelling of foreground signals due to the interaction between CMB photons and structures, in their path from the last scattering surface to the observer. Foregrounds are in general modelled with simple templates, obtained e.g. from numerical simulations and at fixed cosmology. These foregrounds though contain cosmological information, as well as information on the astrophysical processes that shape the structure of the recent Universe. A proper modelling of these components can therefore lead to improvement in the general constraining power of cosmological parameters.
In this talk I will focus on the modelling of the Sunyaev-Zeldovich effects (thermal and kinetic, tSZ and kSZ), able to track the hot and ionised gas distribution in the recent Universe.
Adding this full modelling of tSZ and kSZ in the CMB cosmological analysis, combing Planck and SPT observations, I will show the improvement in the cosmological constraining power. I will also describe a Machine Learning approach to provide a fast and accurate evaluation of tSZ and kSZ power spectrum up to very high multipoles.

Speaker: Laura Salvati (Orsay IAS)

Tuesday, 26 March

11:30 → 12:30 Axion thermal production: recent advances and future challenges

After reviewing the experimental landscape for axion searches, I will focus on axion thermal production in the early universe, highlighting the recent progresses in the calculation of the axion thermalization rate in the non-perturbative QCD regime. Additionally, I will address the critical theoretical components that are still missing for a robust prediction of the axion's thermal abundance. This understanding is crucial for evaluating the potential sensitivity of next generation CMB experiments.

Speaker: Luca Di Luzio (Istituto Nazionale di Fisica Nucleare)

Tuesday, 9 April

16:00 → 17:00 Beam Physics Research in IOTA/FAST at Fermilab

The Fermilab Accelerator Science and Technology (FAST) facility at Fermilab is dedicated to research and education in beam physics. It comprises a photoinjector, a superconducting electron linac and a storage ring, the Integrable Optics Test Accelerator (IOTA).
Recent results include the implementation of nonlinear integrable lattices and the suppression of resonances and instabilities; the demonstration of optical stochastic cooling, which uses a particle’s radiation to finely control its dynamics; the observation of the motion of single electrons; and the measurement of the classical and quantum properties of undulator radiation. In the linac, experiments on high-efficiency gamma-ray sources and on noise in intense electron bunches are under way. The IOTA proton injector, currently under construction, will enable the program on space-charge-dominated beams. Some research areas under study are beam dynamics with electron lenses; the interplay between instabilities, space-charge, feedback systems and electron cooling; and crystalline ion beams.
In this presentation, results and plans are highlighted, together with opportunities for collaboration.

Speaker: Giulio Stancari (Fermilab)

Wednesday, 10 April

14:30 → 15:30 Why do we want to go beyond the Standard Model? and how?

From one side gravity suggests that quantum field theories are low energy approximation of a more fundamental theory, on the other side phenomenology tell us that we need to go beyond the standard model. Neutrino physics is one of the most important motivation besides baryon asymmetry and the dark problem. In this talk I focus on the origin of neutrino mass from a model building point of view and I discuss possible way and strategy of extension. As an example I show the case where the electroweak group SU(2) x U(1) is extended to SU(3) x U(1). This model is named 331.

Speaker: Stefano Morisi (Università di Napoli)

Tuesday, 16 April

11:30 → 12:30 Reconciling HST, JWST and Planck

In the era of precision cosmology, recent observations from missions like the Planck satellite and the SH0ES team using the Hubble Space Telescope (HST) have challenged the standard model of cosmology, ΛCDM. Notably, discrepancies in the measurement of the Hubble constant from cosmic microwave background (CMB) and local measurements using Cepheids and supernovae have emerged, suggesting potential shortcomings in our understanding of cosmology.
Additionally, discoveries from the James Webb Space Telescope (JWST) have unveiled a significant density of massive galaxies at high redshifts, posing further challenges to the ΛCDM. Despite conservative assumptions about galaxy formation, these findings may not align with any of the current cosmological models.
I will talk about cosmological tensions utilizing most of the cosmological probes from high, low, intermediate, and local redshifts along with various proposed solutions to these cosmological tensions and highlighting their limitations compared to the ΛCDM.
I will discuss about how important it is now to do critical reassessment of the basic assumptions of inverse distance ladder and standard distance ladder proposing solutions such as allowing possibility of new physics such as negative cosmological constant or G-transition hypothesis/ PLR break in cepheids.
Furthermore, while assuming ΛCDM and no systematics in the current JWST results, we propose that there may be an unknown systematic error in current large angular scale CMB polarization measurements, or new physics is required to explain the discrepancy.

Speaker: Dott.ssa Ruchika (Università di Roma La Sapienza)