|Dia: 21 de Desembre
||Lloc: Sala de Graus de la Facultat
de Fisica (UB)
|Dia: 22 de Desembre del 2005
||Lloc: Sala de Graus de la Facultat
de Fisica (UB)
Dimecres, 21 de desembre:
Dijous, 22 de Desembre:
Títols i Abstracts
- Enrique Fernández (IFAE)
"Neutrino Oscillations: Status and Plans"
In this talk I will review the status of neutrino oscillations. After explaining the basic physics of oscillations I will describe the data obtained with solar, atmospheric, reactor and accelerator neutrinos and what these measurements imply for the oscillation parameters. Some of the many new planned and proposed experiments will then be explained with emphasis on how they can advance in our knowledge of the oscillations phenomenon.
- Bartomeu Fiol (Amsterdam U.)
"The entropic principle"
Given the huge number of vacua in string theory, a natural
question is whether the theory provides a mechanism for vacuum selection.
Building on recent work on the relations between flux vacua, black holes
and topological strings, Vafa and collaborators have proposed such a
mechanism in the context of flux vacua, by weighting each different vacuum
with the entropy of a closely related black hole. In this talk I will
present this principle and present some examples of critical points.
- Enrique Rico (IQQ, Innsbruck)
"Scale perturbation in Matrix Product States"
I will briefly review the notion of matrix product states and real space renormalization group transformations. I will try to show how both tools can be used together. As an example of this set of new ideas I will study the spin-1 Heisenberg model. (work under construction...)
- Albert Roura (University of Maryland, U.S.)
"Black hole horizon fluctuations"
A number of studies have suggested that the event horizon of macroscopic black holes could exhibit significant fluctuations, much larger than the Planck scale. The stochastic gravity formalism provides a suitable framework to analyze these issues within a low-energy effective field theory approach.
Spherically symmetric fluctuations for an evaporating black hole will be considered in detail. Next, after critically examining an assumption implicitly made in earlier studies, I will discuss how to overcome that shortcoming starting with the case of black holes in equilibrium. This requires a better understanding of how to probe metric fluctuations near the horizon, and several proposals along that direction will be made.
- Koji Hashimoto (U. Tokyo)
"ADHM is a Tachyon Condensation"
(based on hep-th/0511297)
We completely realize the ADHM construction of instantons in D-brane language of tachyon condensations. Every step of the construction is given a physical interpretation in string theory, in a boundary state formalism valid all order in \alpha'. Accordingly, equivalence between Yang-Mills configurations on D4-branes and D0-branes inside the D4-branes is proven, which shows that small instanton configurations of the Yang-Mills fields are protected against stringy \alpha' corrections. We provide also D-brane realizations of the inverse ADHM construction, the completeness, and the noncommutative ADHM construction.
- Lluis Masanes (Bristol U.)
"All entangled states are no simulable by classical correlations"
Entangled states are the ones that cannot be generated by
classically correlated local quantum operations. We show that,
equivalently, one can also define entangled
states as the ones that cannot be simulated by classical
correlations. We also show how, useful (free) entanglement can be
extracted from all non-separable states of any number of parties.
We also establish a correspondence between these two results by
showing the equivalence between distillability, and asymptotic
- Siannah Peñaranda Rivas (CERN)
"Decoupling properties of Higgs boson decays"
The supersymmetric (SUSY) radiative corrections, at the one-loop level, to h^0, H^+ decays, in the context of the Minimal Supersymmetric Standard Model (MSSM) are discussed. The decoupling behaviour of the various MSSM sectors is analyzed in some special cases, where some or all of the SUSY mass parameters become large as compared to the electroweak scale.
We show that in the decoupling limit of both large SUSY mass parameters and large CP-odd Higgs mass, the h^0 -> b \bar b decay width approaches its Standard Model value at one loop, with the onset of decoupling being delayed for large tan beta values. However, this decoupling does not occur if just the SUSY mass parameters are taken large.
A similar interesting non-decoupling behaviour, also enhanced by tan beta, is found in the SUSY-QCD corrections to the H^+ -> t \bar b decay width.
- David Mateos (Santa Barbara, USA)
- Guifre Vidal (Queensland U., Australia)
I will discuss recent progress in our theoretical understanding of
entanglement in quantum many-body systems, and how this has originated, in
the last three years, an explosion of work in the field of numerical
renormalization group methods.
- Alex Travesset (AMESLAB, USA)
"Crystalline Particle Packings on a fixed geometry with Long and Short Range Power Law Potentials"
Finding the configuration that minimizes the energy of a large number of particles that are constrained to a particular topography is a surprisingly difficult problem with many important realizations in the traditional sciences. A classical example is the Thomson problem, consisting in minimizing the energy of M particles constrained to move on the sphere interacting with the 3 dimensional Coulomb potential. This problem has usually been solved by numerical methods only for small (less than 200) number of particles. In this talk, I will present a general approach to find the ground state in the opposite limit of large number of particles, which applies to any geometry and wide family of potentials. It will be shown that for many interaction potentials the energy of the ground state is universal with respect to the geometry and consists of defects (vertices that are five or seven coordinated) whose precise distribution can be predicted.
Explicit solutions will be given for the sphere and for particles interacting with a short-ranged potential on a torus.
- Joan Simon (Penn U.)
" D'estats quàntics a espais-temps clàssics
Estudiem el sector que preserva la meitat de la supersimetria
de la teoria N=4 SYM i la correspondencia AdS/CFT per establir un
diccionari entre estats quàntics i descripcions clàssiques emprant
mètriques. Aquest model ens permet posar de manifest la importancia del límit semiclàssic, i dóna una prescripció natural de com
integrar "graus de llibertat" mitjançant la qual emergeix una
geometria clàssica que és singular i que coincideix exactament amb els
forats negres extremals. Aquest sistema dóna evidencia explícita
sobre l'origen de la termodinàmica gravitatòia i l'emergència
d'espais-temps singulars clàssics que considerem tindrà una validesa
molt més general en la física de forats negres, singularitats, i en
la natura quàntica de l'espai-temps.
- Toni Mateos (Imperial College London)
"Families of fixed points of RG flows in 4d from string theory"
It has become clear in the last years that the space of 4d field
theories has large continuous families of RG fixed points (of course,
supersymmetry seems crucial there). This first inspired developments in
string theory, allowing us to build large families of new string
backgrounds. We will discuss how to go the other way around: get data from
string theory to find new continuous families of RG fixed points, both in
4d and 3d, and both with susy and without susy.
- Antonio Dobado (UCM)
"World brane scenarios with low tension"
In this talk we will review the main properties of brane-world models with low tension. Starting from very general principles it is posible to obtain an effective action from which we can derive the cross sections for the relevant high energy processes and from them, to set bounds on the different parameters appearing in these models. In addition we will see how they provide a WIMP candidate for dark matter in a natural way, and finally we will disscuss the constraints comming from the precision test of the SM and the muon anomalous magnetic moment.