Tag Archives: Evento scientifico

General introduction to cosmology of modified gravity is given. It is shown that different forms of modified gravity are possible, many of them being consistent with Solar system tests and cosmological bounds. Special attention is paid to the so-called F(R) modified gravity. It is shown that such a theory may naturally describe the early-time inflation with late-time acceleration (dark energy epoch). Realistic versions of F(R) gravity are proposed and the inflationary indices are shown to be consistent with Planck experiment. New ghost-free versions of modified gravity are introduced and their cosmological evolution is studied. It is shown that it may naturally give the unification of inflation with dark energy, while the scalar field which appears there plays the role of dark matter. 

https://agenda.infn.it/event/21379/overview

We propose a model describing the evolution of free electron current density in graphene giving rise to bidimensional wormhole solutions. Based on analogue concepts of General Relativity, we perform the analysis using the difference between curvatures of parallel and antiparallel spins. In such a framework, effective “gravitons” emerges in the form of gauge fields exchanged between electrons. In a plain grapheme system, the curvatures produced by both kinds of spins neutralize each other giving rise to no conduction. However, in the presence of geometrical defects of the graphene sheets, the inequality between curvatures leads to the emergence of current densities and conductivity in a wormhole solution. Depending on the type of defects, the resulting current density can be negative or positive. Possible applications are discussed.

In order to characterize low absorbing materials, where UV-vis spectrophotometry does not provide enough sensitivity, other more sensitive methods are needed. Photothermal lens technique is a very sensitive method to detect and photothermal characterize of materials. The thermal lens technique measures the amount of heat generated followed by the absorption of light in a sample. The heat produces a temperature gradient in the medium which generates a spatial refractive index gradient called a thermal lens. The performance of this method and applications such as photocatalytical degradation of dyes as well as the photothermal characterization of plasmonic nanostructures, quantum dots and graphene are presented.

Semileptonic decays provide an excellent environment for testing the Standard Model. Tests of lepton flavour universality using b->clnu decays have shown hints of new physics. In this seminar, an overview of the status of these measurements is given, including the impact of radiative corrections on these types of measurement. Also CKM matrix elements, and in particular |Vcb|, can be measured using semileptonic B decays. There is a long-standing disagreement between values of |Vcb| measured inclusively or exclusively. The exclusive determination relies on the parametrisation of the form factors of the decay.  Measurements using Bs mesons instead of B mesons can shed a new light on lepton flavour universality,  |Vcb| and form factors. They suffer from less backgrounds from excited decays and are easier to compute on a lattice. In this seminar I will present a new measurement of |Vcb| using Bs decays, as well  as measurements of Bs->Ds(*)munu form factors, performed by the LHCb experiment. Future prospects for measurements of Vcb, R(Ds) and R(Ds*) are also discussed.

In relativistic heavy-ion collisions a “Little-Bang” is produced, in which the matter for a few fm/c experiences very similar (but not equal) conditions to the one occurred in the early universe, about one millionth of a second after the Big Bang. In particular one expects to produce a fireball of deconfined QCD matter in which the active degrees of freedom are quarks and gluons rather than hadrons. If this fireball lives for such a short amount of time, which are the experimental signatures of the onset of deconfinement and how can one extract information about its properties from the experimental data? In this connection I will show how heavy-flavour particles arising from the hadronization of charm and beauty quarks play a major role.

ALICE (A Large Ion Collider Experiment) is the CERN LHC experiment optimized for the study of the strongly interacting matter produced in heavy-ion collisions and for the characterization of the quark-gluon plasma (QGP). ALICE has collected precision data at different energies for pp, p-Pb, Pb-Pb and Xe-Xe collisions: this unique set of data allows us to investigate bulk particle production for very different systems and compare them at similar multiplicities. In particular, light flavour particles, containing only u, d and s valence quarks, are the most copiusly produced and so they play a central role in the characterization of the bulk properties of the QGP, carrying essential information about the produced medium and reaction dynamics. Part of this information is carried by the inclusive and identified transverse momentum distributions of light charged particles, measured over a wide pT range thanks to the excellent tracking and particle-identification capabilities of the ALICE detector. Such distributions show that at low to intermediate pT charged particle production is governed by the collective expansion of the system. The chemical and kinetic freeze-out parameters of the system are extracted via statistical-thermal and combined blast-wave fits to the data in heavy-ion collisions and are compared to results obtained in pp and p-Pb collisions at similar multiplicities. At high pT, typically above 5 GeV/c, a suppression of hadronic production, due to medium effects such as parton energy loss, can be observed. These effects can be investigated by calculating the nuclear modification factor, defined as the ratio between the pT spectrum measured in nucleus-nucleus collisions and a reference spectrum in pp collisions scaled by the number of binary nucleon-nucleon collisions. In this talk, we review the most recent ALICE results on the production of pions, …

An updated review is presented of the theory of low-energy antikaon and hyperon interactions with nucleons and nuclear systems. Applications include kaonic hydrogen, recent calculations of kaonic deuterium and comparisons with K-p correlation functions from ALICE at LHC. This is followed by a discussion of the possible role played by kaons and hyperons in dense baryonic matter, with special emphasis on constraints provided by the existence of two-solar-mass neutron stars and garvitational wave signals of neutron star mergers.

The international Linear Collider (ILC) is an electron-positron collider whose initial goal is to make precision measurements on the Higgs boson. Such measurements are expected to elucidate the shortcomings of the Standard Model of elementary particles and guide us to the new physics that governs the universe. Being a linear collider, It also has potential to upgrade its collision energy without sacrificing the investment up to that point.  In this talk, we review the scientific case of the ILC and describe its political status.