Ciclo di Conferenze dei corsi di Laurea in Fisica del Dipartimento di Matematica e Fisica
Edizione 2021
Stefano Morisi
Dipartimento di Fisica ”Ettore Pancini” dell’Università degli Studi di Napoli e dell’INFN -Sezione di Napoli
New Physics beyond Standard Model from Astrophysics
Link identifier #identifier__69039-1Locandina – 2 febbraio 2021, ore 15:00 online
The Standard Model (SM) is in amazing agreement with data. For instance, precision test of SM, as well as the so called Cabibbo Kobayashi Maskawa (CKM) quark mixing unitarity triangle tell us that SM is in agreement with data at per mille level! On the other hand, a part of some interesting anomalies in meson physics, the SM lack completely the explanation of some important experimental evidences. The first one is the baryon asymmetry of the Universe, then the dark problem and least but not last neutrino mass origin. Some physics beyond the Standard Model is required. Symmetry principles guided us in building SM and inspired us in looking for new physics. One of the most important and well known example is SuperSymmetry (SUSY) predicting a large number of new fields. Unfortunately colliders (LEP and LHC) have not (yet) discovered new particles other than the Standard Model Higgs. So probably in order to give an answer to the open Standard Model’s questions, some different approach is needed. May be we have to go beyond the idea of symmetry form the theoretical side. From the experimental point of view may be we have to go beyond the use of colliders (waiting for powerful new generation one?) even for particle physics. A timely alternative could be astrophysics. Indeed astrophysical objects could be sources of cosmic rays and therefore of very high energy particles: protons, gamma, neutrino. Astrophysics is a very promising context where it is possible to study new physics in parallel with colliders. I will provide some examples of physics beyond the standard (dark matter, sterile neutrino and violation of equivalence principle) and their multimessinger gamma and neutrino phenomenology related with IceCube neutrino telescope.
Beta Lusso
Dipartimento di Fisica e Astronomia, Università di Firenze
Quasars as standard(izable) candles (and the physics behind)
Link identifier #identifier__165050-2Locandina – 2 marzo 2021, ore 15:00 online
I will present the latest results on our analysis of the non-linear X-ray to ultraviolet luminosity relation in a sample of optically selected quasars from SDSS, cross-matched with the most recent XMM-Newton and Chandra catalogues. I will show that this correlation is very tight, implying that the observed relation is the manifestation of an ubiquitous (but still unknown) physical mechanism, that regulates the energy transfer from the accretion disc to the X-ray emitting corona in quasars. I will also discuss what the perspectives of quasars in the context of observational cosmology are and present new measurements of the expansion rate of the Universe in the redshift range z=0.5-7.5 based on a Hubble diagram of quasars.
Claudio Faccenna
Dipartimento di Scienze, Università Roma Tre
Deep mantle root of high mountain peaks
Link identifier #identifier__173543-3Locandina – 23 marzo 2021, ore 15:00 online
Orogeny result from crustal thickening process at active margins. Fundamental progresses have been done during the last decades on understanding the mechanism of orogeny. However,
the actual causes of mountain building are still debated, especially for the case of extreme crustal thickening. Inspired by seminal work of Holmes (1931), here we explored the connection between the style of orgeny and the mantle dynamics. We first propose to distinguish between orogenies that are directly related to predominantly one-sided subduction, also referred as “slab-pull orogeny”, and the ones that are related to deep large convection referred as “mantle orogeny” or “slab-suction orogeny”. The latter type leads to extreme crustal thickening and is generate by anchoring of subduction on the lower mantle and the onset of large-scale convection. This model is supported by numerical test showing that the presence of lower boundary layer in convection system enhances whole mantle convection and upper plate compression during penetration of slab in the lower mantle. We explore the validity of this model by looking at the present distribution of compressional backarc region, which is more is common for deeper lower mantle slab, and by the history and evolution of the Nazca and Tethyan slab. The reconstruction of the Andean Cordillera and Tiben-Himayan orogeny suggests that extreme crustal thickening below the Bolivia and Tibetan plateau occurred during slab penetration. This Tertiary episode of crustal thickening show similarity with the Late Paleozoic event leading to the Pangea supercontinent, when accretionary Gondwanide orogeny growth during the Variscan-Appalachian and Ural collisional orogen. We propose that this Late Paleozoic large-scale compression is also related to deep lower mantle subduction. If our model is correct, the geological record of orogeny can be used to decipher time-dependent mantle convection, and we can speculate that lower mantle subduction occurred episodically leading to supercontinental cycle.
Gaia Camisasca
Dipartimento di Matematica e Fisica, Università Roma Tre
Biological and confined water in metastable states
Link identifier #identifier__136080-4Locandina – 18 maggio 2021, ore 15:00 online
Water plays relevant roles in many phenomena taking place in biology and nanotechnology. In many situations water is found in thermodynamical metastable regimes, either in the supercooled regime where water is in the liquid phase but at very low temperatures, or in extremely strong confinement.
In this seminar I will focus on two different applications which leverage these metastabilities of water: the first is the case of water in contact with biomolecules important for cryopreservation and the second is the case of water confined in nano-scale porous materials widely employed in technological devices.
In the first part of the talk, we study the cryoprotective mechanism of trehalose-water solutions on proteins. In the cryopreservation of biomaterials like proteins, stem cells, tissues, and foods, the materials are immersed in aqueous solutions and preserved by being cooled down to very low temperatures, well below the melting temperature of water. The addition of excipients to water is essential to prevent ice growth which can damage biomaterials. The sugar trehalose is a very effective bio-compatible excipients but the microscopic mechanism behind its bioprotection is still matter of debate.
In the second part of the talk, I will focus on water confined inside cylindrical nanopores, where water can evaporate at temperatures much lower than in the bulk phase causing the formation of a vapour pocket – a bubble – inside the nanopores. Today many devices used for energy storage and release, shock bumpers, nanopore sensing, and chromatography, rely on the drying-wetting properties of nanopores. In this study we use rare-event methods to characterize the mechanism of the confined bubble formation in presence of diluted hydrophobic gas. Implications for the action of anesthetics on biological channels will be also discussed.
Aires Ferreira
Department of Physics, University of York
Spin-orbit coupling phenomena in van der Waals materials: perspectives from theory and experiment
Link identifier #identifier__177586-5Locandina – 4 maggio 2021, ore 15:00 online
Spin-orbit coupling (SOC)—a relativistic interaction which entangles a particle’s motion with its quantum mechanical spin—is fundamental to a wide range of physics phenomena, spanning from the formation of topological insulators to the spin Hall effect of light. Recent years have seen remarkable progress in probing, enhancing and tailoring SOC effects in atomically thin materials and their interfaces. From the electrical control of spin-valley coupling in bilayer graphene to reversible spin-charge conversion in graphene on transition metal dichalcogenides at room temperature, these discoveries challenge our previous notions of the possible behaviour of spin-orbit coupled electrons at interfaces. In this talk, I will discuss recent results of van der Waals heterostructures and new proposals for probing and exploiting the rich interplay of spin and lattice-pseudospin spin degrees of freedom triggered by SOC.
Fausto Martelli
IBM Research Europe
The (un)familiar properties of water, their effect on sustaining life and their origin
Link identifier #identifier__198381-6Locandina – 6 luglio 2021 ore 15:00 online
Water is arguably a very important material. On the other hand, it shows remarkably puzzling behaviours that make it unique to sustain life as we intend it. We experience some of these behaviours in our everyday life and, therefore, we don’t perceive them as strange —nor important— as they really are. In this talk, I will give an overview of a few of such weird behaviours and I will present the state of the art in our understanding the origin of water anomalous behaviour. Finally, I will give some practical example about how understanding basic science can lead to the development of new technologies.
Gabriele Ponti
INAF – Osservatorio Astronomico di Brera
The X-ray view of the Galactic outflow
Link identifier #identifier__169153-7Locandina – 15 settembre 2021, ore 15:00 online
Outflows from Active Galactic Nuclei and starburst galaxies are known to play a critical role in the formation and evolution of structures in the Universe.
However, the role of such outflows in normal galaxies is still highly debated. Being located at only ~8 kpc from us, the center of our Galaxy provides us with the unique opportunity to study the physics occurring in the core of normal galaxies at very high spatial resolution. Thanks to its penetrating power, the X-ray band is particularly suited for studies of the Galactic center, allowing us to have a direct view of the central heart of the Milky Way. I will review the evidence which probe the presence of an outflow from the center of the Milky Way.
In particular, I will report recent results demonstrating the presence of an outflow of hot plasma, connecting the central parsecs around the central supermassive black hole (Sgr A*) with the base of the Galactic halo. Additionally, I will discuss the discovery of the eROSITA bubbles as well as the potential provided by eROSITA to improve our understanding of the hot phase of the Milky Way.
Giulio Settanta
Institut für Kernphysik, Forschungszentrum Jülich, Germany
First detection of solar neutrinos from the CNO cycle with the Borexino detector
Link identifier #identifier__156911-8Locandina – 5 ottobre 2021, ore 15:00 online
Neutrinos are elementary particles which are known since many years as fundamental messengers from the interior of the Sun. The Standard Solar Model, which gives a theoretical description of all nuclear processes which happen in our star, predicts that roughly 99% of the energy produced is coming from a series of processes known as the “pp-chain”. Such processes have been studied in detail over the last years by means of neutrinos, thanks also to the important measurements provided by the Borexino experiment. The remaining 1% is instead predicted to come from a separate loop-process, known as the “CNO cycle”. This sub-dominant process is theoretically well understood, but has so far escaped any direct observation. Another fundamental aspect is that the CNO cycle is indeed the main nuclear engine in stars more massive than the Sun.
In 2020, thanks to the unprecedented radio-purity and temperature control achieved by the Borexino detector over recent years, the first ever detection of neutrinos from the CNO cycle has been finally announced. The milestone result confirms the existence of this nuclear fusion process in our Universe. Here, the details of the detector stabilization and the analysis techniques adopted are reported. Final results are discussed, together with the implications for solar physics and astrophysics.
Paolo Lipari
INFN Sezione Roma I, Sapienza Università di Roma
High energy sources and multi-messenger astrophysics
Link identifier #identifier__9386-9Locandina – 8 novembre 2021, ore 15:00 online
This talk will review what we know about the sources and mechanisms that generate very high energy particles in the Galaxy and in the Universe. These sources can be studied with a multi-messenger (cosmic rays, gamma rays, neutrinos and gravitational waves) observations. Recent studies have given very important information, but many fundamental question remain open.
Maura Pavan
Università Milano – Bicocca, Dipartimento di Fisica e INFN Sezione MIB
Double beta decay searches: status, experimental challenges and perspectives
Link identifier #identifier__1217-10Locandina – 14 dicembre 2021, ore 15:00 online
Neutrinoless double beta decay (0 ν β β) is the sponatenous decay of a nucleus emitting only two electrons and no neutrinos. The process exists if neutrinos are their own antiparticle or, said in the particle physics language, if lepton number is violated. The relevance is that lepton number violation is exactly what we need to explain one of the still intriguing mysteries of our universe: why there is only (almost) matter and no antimatter. Experimental searches of 0 ν β β are extremely challenging, basically because the process is expected to be extrahordinary rare and its signature is rather weak. Despite this, there is a world wide experimental effort in this field that sees Italy and Laboratori Nazionali del Gran Sasso as one of the most important stakeholders. In the seminar I will discuss status, experimental challenges and perspectives for 0 ν β β experiments.