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Theory Seminars

Pizza Seminars

Theory Seminar: Can cosmological magnetic fields explain the Baryon Asymmetry of the Universe?

Friday, 8 July 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Kohei Kamada (Arizona State University)

Magnetic fields are ubiquitous in the Universe. In particular, recently observational indications of the existence of intergalactic magnetic fields, which may have a cosmological origin, are reported. If they are helical, chiral anomaly in the Standard Model can affect the chiral and baryon asymmetry of the Universe. Here I discuss the cosmological consequence of such magnetic fields. If they originated from a mechanism before the electroweak phase transition, it can generate baryon asymmetry without new physics for baryogenesis. Baryon asymmetry generated in this mechanism can survive the sphaleron washout effect. In order to explain the present baryon asymmetry of the Universe, we need another trick or fine-tuning, though.

Theory Seminar: Managing astrophysical uncertainties in direct dark matter detection

Tuesday, 21 June 2016 from 14:30 to 15:30 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Francesc Ferrer (Washington U, St. Louis)

Save for its gravitational effects, very little is known about the composition of the dark matter in the universe. An attractive candidate for making up the dark matter is a weakly interacting massive particle (WIMP), that could be unveiled through its weak-scale interactions using two complementary approaches: direct and indirect detection. Although these programs have attained the sensitivity to probe the particle physics properties in a vast range of WIMP scenarios, they are hampered by uncertainties in the required astrophysical input. In this talk I will review our present understanding of the density and velocity distribution of the dark matter halo, and describe several efforts to constrain the WIMP scattering cross section using observables that are largely halo-independent. Finally, I will show that, by combining null results from direct detection experiments and neutrino telescopes, it is possible to set an upper limit on the scattering cross section independently of the velocity distribut

Theory Seminar: Low-energy effective action for pions and a dilatonic meson

Friday, 10 June 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Maarten Golterman (San Francisco State University)

Numerical simulations of QCD-like theories in which the number of flavors is adjusted so that the beta function is very small, but confinement and chiral symmetry breaking nevertheless take place, appear to reveal the presence of a flavor-singlet scalar meson which can be as light as the pions. Because the breaking of dilatation symmetry, quantified by the beta function, is small relative to QCD, a possible explanation is that the scalar meson is a pseudo Nambu-Goldstone boson associated with the approximate dilatation symmetry. We use this observation to systematically develop a low-energy effective action that accounts for both the pions and the “dilatonic” scalar meson. In order to justify the power counting that controls the couplings of the dilatonic meson we invoke the Veneziano limit, in which the number of fundamental- representation flavors Nf grows in proportion with the number of colors Nc, while the ratio Nf/Nc is kept close to, but below, the critical value where the conformal window is entered.

Theory Seminar: Electronvolt sterile neutrinos: a critical appraisal

Friday, 29 April 2016 from 14:30 to 15:30 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Pedro A. N. Machado (IFT Madrid)

In this talk I review the situation of the short baseline neutrino oscillation anomalies that are still unexplained. The LSND, MiniBooNE, reactor and gallium anomalies will be described and discussed. A critical view of the anomalies in terms of neutrino oscillations will be given. The problem with cosmology will be considered, together with terrestrial oscillation and non-oscillation experiments that can help elucidate this puzzle.

Theory Seminar: Some new ideas on dark matter decay

Friday, 8 April 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker:Òscar Catà (LMU Universitaat Munich)

I will explore two different scenarios to account for the long lifetime of dark matter. In the first one, I will assume that dark matter is stable when coupled to the SM but can proceed through (non-minimal) interactions to gravity. Based on current observations, I will show that even this ‘gravitational portal’ to dark matter decay is rather constrained. In the second scenario, I will present an extension of the SM where the dark matter candidate can be absolutely stable without the aid of ad hoc additional symmetries.

Theory Seminar: Disambiguating the Cosmological Dark Sector

Friday, 18 March 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Iggy Sawicki (Geneva U)

Our observations of dark matter and dark energy are, at least so far, based purely on their effect on their combined effect on the geometry of the universe and therefore ambiguous in a fundamental way. As we progress toward building ever more precise maps of the universe, it will become increasingly important to understand what we can measure definitely, in a model-independent manner and what we can only say on the assumption of a model. I will discuss how to construct such model-independent observables, and the fundamental limits to our knowledge that can only be broken by employing parameterisations resulting from particular models. I will discuss how to approach parametrising our ignorance in a minimal yet consistent and physical manner and ask to what extent such modelling can actually account for anomalies we are beginning to see in cosmological data.

Theory Seminar: Probing Gravitational Waves from First-Order Phase Transitions at eLISA

Monday, 29 February 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Germano Nardini (Institute for Theoretical Physics, University of Bern)

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Theory Seminar: A study of the gamma-ray Galactic center excess with the Fermi LAT Pass 8 data and limits on dark matter annihilation

Friday, 26 February 2016 from 12:00 to 13:00 (Europe/Madrid) at IFAE ( IFAE Seminar room )

Speaker: Dmitry Malyshev (University of Erlangen-Nuremberg)

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Theory Seminar: The DarkSide Program for Direct Dark Matter Searches at LNGS

Friday, 19 February 2016 at 14:30 at IFAE Seminar room

Speaker: Cristian Galbiati (Princeton University)

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Instrumentation Seminar: e-ASTROGAM, a wide-field observatory for the MeV / sub-GeV energy band

Thursday, 18 February 2016 at 10:30 at IFAE ( Seminar Room )

Speaker: Margarita Hernanz ICE (CSIC-IEEC)

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