Facultat de Física

 Inici Facultat Inici UB
 Agenda/Conferències i seminaris

El límit per poder anunciar en paper seminaris i conferències en els ascensors és el divendres a les 12 hores de la setmana anterior. Amb posterioritat a aquesta data el seminari o conferència quedarà només recollit al web de la Facultat. Aleshores la publicitació en paper serà responsabilitat dels organitzadors.

 Facultat de Física, Divendres 24 de Febrer de 2017, a les 10:30h Seminari de l'Institut de Ciències del Cosmos Títol: Hunting for black holes and dark matter with globular clusters Conferenciant: Mark Gieles (University of Surrey, UK) Abstract: Globular clusters (GCs) contribute to astrophysics on a wide range of scales: from early Universe cosmology to the formation and evolution of galaxies. The historic first detection of gravitational waves (GWs) from merging BHs by LIGO led to the suggestion that dynamical interactions in the cores of GCs may be one of the prime production channels of BH mergers. We do not know, however, whether BHs are ubiquitous in GCs, or not. Establishing this empirically is challenging, because accreting BHs are rare. We have developed a method to dynamically infer the presence of a stellar-mass BH population in GCs. GCs evolve towards a state of equipartition on a timescale that is shorter than their age, and we use this in multicomponent dynamical models to describe the phase-space properties of stars in a GC that contains BHs. Using multimass models, combined with evolutionary N-body models, we find signatures of a population of 100s of stellar-mass BHs in the Galactic GC NGC 6101 and show that the signal previously ascribed to an intermediate-mass black hole (IMBH) in Omega Cen can equally well be explained by stellar-mass BHs. Finally, we discuss how data from the ESA-Gaia mission will break the degeneracy between the signal of BHs and velocity anisotropy and can be used to get independent measures of the Galactic dark matter distribution from the properties of stars in the outskirts of GCs. Lloc: Seminari DAM (724), 7a planta. Facultat de Física, UB Contacte: secretaria@icc.ub.edu Web: http://icc.ub.edu/activity/870

 Facultat de Física, Divendres 24 de Febrer de 2017, a les 12:00h Seminari del Dep. de Física Quàntica i Astrofísica Títol: An antimatter gravity measurement with antihydrogen Conferenciant: Alban Kellerbauer (MPI Heidelberg) Abstract: The imbalance between matter and antimatter in the observable universe is one of the great unsolved questions in physics. Antimatter experiments, which can probe the fundamental CPT symmetry and the weak equivalence principle of general relativity, have the potential to shed light on this puzzle. After the first production of cold antihydrogen by the ATHENA collaboration at CERN\'s Antiproton Decelerator, second-generation experiments are being performed and/or being set up with the aim of measuring its fundamental properties. Storage and even spectroscopy of antihydrogen have recently become feasible. The goal of the AEGIS experiment is to measure the gravitational interaction between matter and antimatter. Antihydrogen will be produced by a novel technique which involves positronium, the hydrogen-like bound state of an electron and a positron. Subsequently, its free-fall acceleration will be measured with a deflectometer. In this talk, after an introduction to antimatter physics, the present status and medium-term plan of the AEGIS experiment at CERN will be discussed. In addition, advances towards the laser cooling of negative ions - such as the antiproton - will be presented. Lloc: Aula 507 Contacte: hofer@fqa.ub.edu Web:

 Facultat de Física, Dimecres 01 de Març de 2017, a les 14:00h Seminari del Dep. de Física Quàntica i Astrofísica Títol: Looking for New Physics with the Higgs boson Conferenciant: Veronica Sanz (University of Sussex) Abstract: This talk is an introduction to the use of the Higgs boson to look for new physics. We will review the motivation for such analyses, the current LHC sensitivity to new phenomena and future prospects to discover new physics via the precise characterization of the Higgs properties. Lloc: Aula 507 Contacte: hofer@fqa.ub.edu Web:

 Facultat de Física, Dijous 02 de Març de 2017, a les 14:00h Seminari del Dep. de Física Quàntica i Astrofísica Títol: (Super)Particles in AdS Conferenciant: Paul Townsend (University of Camebridge) Abstract: The Breitenlohner-Freedman limit to the tachyonic'' mass of a scalar field in D-dimensional Anti-de Sitter space can be derived by an application of the uncertainty principle to a point particle in AdS. This will be explained in the first part of the talk. The second part will introduce the Sp(4;K) bi-twistor formalism for massive particles in AdS for D=4,5,7,11, corresponding to the normed division algebras K=R,C,H,O. For D=4,5,7 this allows a simple demonstration that the quantum superparticle in a maximally supersymmetric AdSxS vacuum of M-theory is a supergraviton. Lloc: Aula 507 Contacte: hofer@fqa.ub.edu Web:

 Facultat de Física, Divendres 03 de Març de 2017, a les 12:00h Seminari del Dep. de Física Quàntica i Astrofísica Títol: Black-hole superradiance and vector fields Conferenciant: Helvi Witek Abstract: It has been established, on the perturbative level, that rotating black holes are prone to the superradiant instability in the presence of low-frequency, light bosonic fields. It is, however, an entirely open question what the endstate of the instability is when non-linear interactions and backreaction onto the spacetime geometry are taken into account, when these effects become important and what their potentially observable signatures are. We have started to investigate these open issues in the context of massive vector fields, and I will give a status report on our latest results. Lloc: Aula 507 Contacte: hofer@fqa.ub.edu Web:

 Facultat de Física, Divendres 03 de Març de 2017, a les 10:00h Workshop de l'Institut de Ciències del Cosmos Títol: Taller de Física de Partícules Conferenciant: Abstract: Cada any milers estudiants de batxillerat de tot el món esdevenen físics de partícules per un dia, en el Taller de Física de Partícules. El Taller es realitza a la UB des de 2005, i semmarca en el programa internacional Hands on Particle Physics. Consta de tres parts: - Xerrades sobre la física de partícules, impartides per investigadors del nostre grup al CERN. - Estudi de dades reals produïdes a lLHC per part dels estudiants assistents. Els resultats es combinen amb els obtinguts per altres grups d'arreu del món a través de videoconferència. - Breu presentació dels ensenyaments de la Facultat de Física, i visita als seus laboratoris. Lloc: Sala de Graus Eduard Fontserè. Facultat de Física Contacte: descobrintlhc@icc.ub.edu Web: http://icc.ub.edu/activity/855

 Facultat de Física, Divendres 03 de Març de 2017, a les 11:45h Seminari del Dep. de Física Quàntica i Astrofísica Títol: Vortex Dynamics in Coherently Coupled Bose-Einstein Condensates Conferenciant: Alexander Fetter (Standford U.) Abstract: In classical hydrodynamics with uniform density, vortices move with the local fluid velocity. This description is rewritten in terms of forces arising from the interactions with other vortices. For example, two positive vortices experience a repulsive interaction and precess in the positive (anti-clockwise) sense. In contrast, coherent rf Rabi coupling between two components of a Bose-Einstein condensate (BEC) acts very differently: for two positive vortices, one in each component, the Rabi coupling induces an attractive interaction. As a result, the positive vortices now precess in the negative (clockwise) sense. In addition, coherent rf Rabi coupling with a single vortex in a two-component trapped BEC induces periodic transfer of vorticity between the two components at the applied Rabi frequency. Lloc: DAM seminar room (724), 7th floor. Physics Faculty, UB Contacte: bruno@fqa.ub.edu Web: http://www.ecm.ub.es/~bruno/semweb/fansem.html

 Facultat de Física, Dilluns 06 de Març de 2017, a les 12:00h Seminari de l'Institut de Ciències del Cosmos Títol: What can we learn from the Cosmic Dawn and Reionization? Conferenciant: Andrei Mesinger (Scuola Normale Superiore, Pisa) Abstract: The birth of the first stars, black holes and galaxies heralded the end of the cosmic Dark Ages and the beginning of the Cosmic Dawn. The light from these objects heated and ionized almost every atom in existence, culminating in the Epoch of Reionization: the final major phase change of the Universe. This final frontier of astrophysical cosmology is undergoing a transition from an observationally-starved epoch to a "Big Data" field. This process is set to culminate with upcoming Square Kilometre Array observations of the redshifted 21-cm line: providing a 3D map of the first billion years of our Universe. I will discuss the recent clues to reionization, obtained from the CMB, high-redshift galaxies, and quasars. I will present the first detection of ongoing reionization, found in the spectrum of a z=7.1 quasar. Finally, I will showcase the physical bounty of the upcoming 21-cm observations. I will discuss the innovative modeling techniques we are developing to tap into this bounty, allowing us to constrain astrophysical parameters in a fully Bayesian framework. Lloc: DAM seminar room (724), 7th floor. Physics Faculty, UB Contacte: secretaria@icc.ub.edu Web: http://icc.ub.edu/activity/879

 Facultat de Física, Dijous 09 de Març de 2017, a les 11:45h Seminari del Dep. de Física Quàntica i Astrofísica Títol: Low-energy antikaon-nuclei interaction studies by AMADEUS: from strangeness QCD to neutron stars Conferenciant: K. Piscicchia (INFN, Frascati & C.Fermi, Roma) Abstract: The AMADEUS collaboration aims to perform a broad range of studies of the low-energy antikaon-nucleons/nuclei interaction, taking advantage of the low momentum (about 127 MeV/c), almost monochromatic, charged kaons provided by the decay of $\phi$ mesons at-rest at the DA$\Phi$NE factory of LNF (INFN). AMADEUS will provide unique quality data on the antikaons behaviour in nuclear matter, absorption and scattering, the antikaon multi-nucleons bound states formation, the $\Lambda(1405)$ properties and the hyperon-nucleon/multinucleons scattering, in order to solve fundamental open issues in the non-perturbative strangeness QCD sector, and to contribute to understand the possible role of strangeness in neutron stars. As a first step of the experiment a graphite target was implemented in the central region of the KLOE detector at DA$\Phi$NE, in order to obtain a pure sample of K$^-$ captures at-rest in Carbon. These data is being used as reference for the investigation of the 2004/2005 KLOE collected data, in which case the detector was considered as an active target, providing high statistic samples of K$^-$ nuclear absorptions on H, ${}^4$He, ${}^{9}$Be and ${}^{12}$C, both at-rest and in-flight. We will also discuss future plans for performing dedicated measurements of AMADEUS. Lloc: Aula 507, Pere Pascual Contacte: bruno@fqa.ub.edu Web:

 Facultat de Física, Divendres 10 de Març de 2017, a les 12:00h Seminari del Dep. de Física de la Matèria Condensada Títol: Versatile tools towards real-time single-molecule biology Conferenciant: Jordi Cabanas-Danés (LUMICKS, Capture Molecular Interactions) Abstract: Biological processes performed by proteins interacting with and processing DNA and RNA are key to cell metabolism and life. Detailed insights into these processes provide essential information for understanding the molecular basis of life and the pathological conditions that develop when such processes go awry.  The next scientific breakthrough consists in the actual, direct, real-time observations and measurements of the individual mechanisms involved, in order to validate and complete the current biological models.  Single-molecule technologies offer an exciting opportunity to meet these challenges and to study protein function and activity in real-time and at the single-molecule level. Here, we present our efforts for further enabling discoveries in the field of biology and biophysics using both the combination of optical tweezers with single-molecule fluorescence microscopy (C-TrapTM) and acoustic force spectroscopy (AFSTM). During this seminar we will discuss the latest applications of this technology that can enhance our understanding not only in the field of DNA/RNA-protein interactions but also in the fields of molecular motors, protein folding/unfolding, cell membranes and genome structure and organization. These experiments show that the technological advances in hybrid single-molecule methods can be turned into an easy-to-use and stable instrument that has the ability to open up new venues in many research areas. Lloc: Aula Seminari 3.20, Dept. Física de la Matèria Condensada, 3rd floor of Physics Building Contacte: fritort@gmail.com Web: http://ffn.ub.es/ritort/news-activities/