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DATE PLACE TITLE SPEAKER  HOST 
2013
11 Jul 2013 (507)
TBA Abstract TBA
Dr. Jennifer Nebreda
U. Complutense Madrid
Prof. A. Ramos
27 Jun 2013 (507)
Discrete symmetry, topological charges and the angular momentum of the photon Abstract TBA
Dr. Albert Ferrando
U. Valencia
Dr. M. A. Garcia-March
20 Jun 2013 (507)
Confronting the quantum many-body problem: an overview of the coupled cluster method and its applications in physics Abstract Examples of quantum many-body systems abound in Nature. Thus, it is clear that in fields like molecular, solid-state, and nuclear physics most of the fundamental objects of discourse are interacting many-body systems. But even in elementary particle physics one is usually dealing with more than one particle. For example, at some level of reality a nucleon comprises three quarks interacting via gluons and surrounded by a cloud of mesons, which are themselves made of quark-antiquark pairs. Even more fundamentally, even the “physical vacuum” of any quantum field theory is endowed with an enormously complex infinite many-body structure due to virtual excitations. A key central role in modern physics is thus occupied by quantum many-body theory, where we are especially interested in the possible existence of any universal techniques that are powerful enough to treat the full range of many-body and field-theoretic systems. One such method is the coupled cluster method [1-4]. This has become one of the most pervasive (possibly the most pervasive), most powerful, and most successful of all fully microscopic formulations of quantum many-body theory. It has been applied to more systems in quantum field theory, quantum chemistry, nuclear, subnuclear, condensed matter and other areas of physics than any other competing method. It has yielded numerical results which are among the most accurate available for an incredibly wide range of both finite and extended systems on either a spatial continuum or a regular discrete lattice. In this seminar I aim to give an overview of the method itself and some illustrative examples of its power and range of applicability. Specific examples will include finite atomic nuclei and nuclear matter, the electron gas, pion-nucleon pseudoscalar field theory, U(1) lattice gauge field theory, and spin-lattice models of quantum magnetism.
References [1] R.F. Bishop and H.G. Kümmel, Physics Today 40(3), 52 (1987). [2] R.F. Bishop, Theor. Chim. Acta 80, 95 (1991). [3] R.F. Bishop, in "Microscopic Quantum Many-Body Theories and Their Applications," edited by J. Navarro and A. Polls, Lecture Notes in Physics 510, Springer-Verlag, Berlin, p.1 (1998). [4] D.J.J. Farnell and R.F. Bishop, in “Quantum Magnetism,” edited by U. Schollwöck, J. Richter, D.J.J. Farnell and R.F. Bishop, Lecture Notes in Physics 645, Springer-Verlag, Berlin, p. 307 (2004).
Dr. R. Bishop (Feenberg Medal)
U. Manchester
Prof. A. Polls
6 Jun 2013 (507)
Heavy flavor diffusion in a hot hadronic gas Abstract Current abstract: I will review the recent results concerning the diffusion and relaxation of heavy mesons in a hadronic gas at finite temperature. I will describe the dynamics of D and B mesons interacting with light mesons and show how the drag force and diffusion coefficients can be extracted using the Fokker-Planck equation. Results including baryons will also be presented.
Dr. J.M. Torres-Rincon
IEEC-UAB
Prof. J. Soto
27 May 2013 (507)
Illuminating the neutron skin Abstract Current abstract: An accurate determination of the distribution of neutrons in the atomic nucleus has proven elusive despite decades of study. This gap in our knowlege is an impediment to obtaining a detailed understanding of nuclear structure, neutron rich matter and neutron stars. This talk will present a new measurement of the matter distribution of 208Pb using coherent neutral pion photoproduction near the reaction threshold. The measurement utilised the large acceptance Crystal Ball detector at the MAMI tagged photon beam facility in Mainz, Germany. Preliminary measurement of the size and diffuseness of the neutron skin forming on the surface of 208Pb will be presented. Future plans will also be discussed.
Prof. Daniel Watts
U. Edinburgh
Prof. M. Centelles
24 May 2013 (507)
Nucleon Resonance Structure from Exclusive Meson Electroproduction Abstract Current abstract: The CLAS detector at Jefferson Lab is a unique instrument, which has provided the lion's share of the world's data on meson photo- and electroproduction in the resonance excitation region. The electroexcitation amplitudes for the low-lying resonances $P_{33}(1232)$, $P_{11}(1440)$, $D_{13}(1520)$, and $S_{11}(1535)$ were determined over a wide range of Q^2 < 5.0 GeV^ in a comprehensive analysis of exclusive single-meson ( $\pi^+n$, $\pi^0p$) reactions in the electroproduction off protons. Further, CLAS was able to precisely measure $\pi^+\pi^-p$ electroproduction differential cross sections provided by the nearly full kinematic coverage of the detector. The electrocouplings of the $P_{11}(1440)$ and $D_{13}(1520)$ excited states are determined from the exclusive-$\pi^+\pi^-p$ reaction. Consistent results on the electrocouplings from two-independent analyses (single- and double-pion electroproduction) have provided compelling evidence for the reliable extraction of the $N^*$ electrocouplings. Preliminary results on the electrocouplings of the $S_{31}(1620)$, $S_{11}(1650)$, $D_{33}(1700)$, and $P_{13}(1720)$ states have recently become available. Theoretical analyses of these results have revealed that there are two major contributions to the resonance structure: a) an internal quark core and b) an external meson-baryon cloud. These CLAS results have had considerable impact on QCD-based studies on $N^*$ structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 $N^*$ structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons.
Dr. Phil Cole
U. Idaho (USA)
Dr. B. Julia-Diaz
30 Apr 2013 (507)
A study of coherently coupled two-component condensates Abstract We present a self-consistent study of coherently coupled two-component Bose-Einstein condensates. The presence of the Rabi coupling prevents phase separation, but introduces a (second-order) phase transition between an unpolarized to a polarized ground state. We analyze the excitation spectrum and the structure factor along the transition for a homogeneous system, pointing out the main differences between a coherently coupled gas and a two-component mixture. Lastly, we discuss how the situation changes in the inhomogeneous case, when the trapping potentials for the two components are the same or different, and especially when one of them is an optical lattice.
Dr. M. Abad
BEC/U. Trento
Prof. M. Guilleumas
25 Apr 2013 (507) (RESCHEDULED)
Heavy flavor diffusion in a hot hadronic gas Abstract Current abstract: I will review the recent results concerning the diffusion and relaxation of heavy mesons in a hadronic gas at finite temperature. I will describe the dynamics of D and B mesons interacting with light mesons and show how the drag force and diffusion coefficients can be extracted using the Fokker-Planck equation. Results including baryons will also be presented.
Dr. J.M. Torres-Rincon
IEEC-UAB
Prof. J. Soto
18 Apr 2013 (507)
Tunneling, self trapping and manipulation of higher modes of a BEC in a double well Abstract Current abstract: We study the dynamical behavior of four modes of atomic Bose-Einstein condensates (BEC) trapped in a one dimensional double well trap. A general Hamiltonian is given in terms of the creation and annihilation operators as well as in the macroscopic limit. Three regimes of interaction are studied, each showing different degree of tunneling and self trapping in the two energy levels. Influence of initial conditions in the ground modes on the excited modes is also studied. The presence of chaos in the system is also noted.
Dr. J. Gillet
U. Okinawa
Dr. M. A. Garcia-March
9 Apr 2013 (507)
Nucleon-Nucleon scattering from the dispersive N/D method: Next-to-leading study Abstract Current abstract: We consider nucleon-nucleon interactions from Chiral Effective Field Theory applying the N/D method. We calculate the discontinuity of the NN partial-wave amplitudes across the left-hand cut (LHC) by including one-pion exchange, once-iterated OPE and leading irreducible two-pion exchange calculated in Chiral Perturbation Theory. We discuss both uncoupled and coupled partial-waves. Phase shifts and mixing angles are typically quite well reproduced, and a clear improvement of the results obtained previously with only OPE is manifest. We are also able to predict the S-wave effective ranges, once the scattering length are fixed without any other experimental input. In this way, we justify the correlation between scattering length and effective range in S-waves making use of the analytical properties of NN partial waves without any further assumption. We also show that the contributions to the discontinuity across the LHC are amenable to a chiral expansion.
Prof. J. A. Oller
U. Murcia
Prof. A. Ramos
13 Mar 2013 (507)
Half-day meeting on ultracold atoms @ BCN Abstract Current abstract:
V. Ahufinger, G. Astrakharchik, J. Douglas
B. Julia-Diaz, P. Massignan, A. Sanpera
UAB/UPC/UB/ICFO
Dr. B. Julia-Diaz
7 Mar 2013 (507)
Integrated Mach-Zehnder interferometer with Bose-Einstein condensates Abstract Quantum mechanical particle-wave duality allows the construction of interferometers for matter waves, which may complement lasers in precision measurement devices such as gravimeters or gyroscopes. This requires the development of new atom-optics analogs to beam splitters, phase shifters, and recombiners. Realizing and integrating these elements into a transportable device has been a long-standing goal. I will present our recent realization of a full Mach-Zehnder sequence with trapped atomic Bose-Einstein condensates (BEC) confined on an atom chip. Particle interactions in our BEC matter waves lead to an intrinsic non-linearity, absent in photon optics. We exploit these interactions to generate a non-classical state with reduced number fluctuations, which is injected into the interferometer. Making use of spatially separated wave packets, a controlled phase shift is applied and read out by a diabatic matter wave recombiner. We demonstrate coherence times a factor three beyond what is expected for a classical coherent state, highlighting the potential of entanglement as a resource for metrology.
Dr. Jean-Francois Schaff
TU Wien
Dr. B. Julia-Diaz
26 Feb 2013 (507)
Why is lead so kinky? Abstract The charge radius of even lead isotopes changes abruptly across the N=126 shell gap. A full theoretical explanation for this kink in charge radii is still missing. Recent experimental data on polonium isotopes suggests that "kinkiness" is a rather general feature in this mass region. We will argue that the mechanism underlying this phenomenon is the occupation of the neutron 1i11/2 orbital. I will review a few mechanisms that could provide such an occupation and suggest further experimental evidence that can validate this picture.
Reference: P. M. Goddard, P. D. Stevenson, and A. Rios, Phys. Rev. Lett. 110, 032503
Dr. Arnau Rios
U. Surrey
Prof. A. Polls
22 Jan 2013 (507)
Weak response of cold symmetric nuclear matter at three-body cluster level Abstract I will present our study of the Fermi and Gamow-Teller responses of cold symmetric nuclear matter within a unified dynamical model, suitable to account for both short-and long-range correlation effects. The formalism of correlated basis functions has been used to construct two-body effective interactions and one-body effective weak operators. The inclusion of the three-body cluster term allowed for the incorporation in our scheme of a realistic model of three- nucleon interactions, referred to as Urbana IX. Moreover, our results show that the sizable dependence of the effective weak operator on the details of the correlation functions is in fact unphysical, an disappears once the three-body cluster term is taken into account. Dr. Alessandro Lovato
Argonne National Laboratory
Prof. A. Polls
09 Jan 2013 (507)
Condensate fraction in ultracold Fermi atoms and in neutron matter Abstract We analyze theoretically the condensate fraction of fermionic pairs for a uniform two-component atomic Fermi gas in the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of weakly-interacting Cooper pairs to the Bose-Einstein Condensate (BEC) of molecular dimers. We derive explicit formulas for condensate density and condensate fraction as a function of the chemical potential and the energy gap both in three [1] and two dimensions [2]. We also consider the case of three-component atomic Fermi superfluid with U(3) invariant attractive interaction [3]. Finally, we investigate the condensate fraction of fermionic pairs in the uniform neutron matter [4] and in the crust of neutron stars.

[1] L. Salasnich, N. Manini, A. Parola, Phys. Rev. A 72, 023621 (2005).
[2] L. Salasnich, Phys. Rev. A 76, 015601 (2007).
[3] L. Salasnich, Phys. Rev. A 83, 033630 (2011).
[4] L. Salasnich, Phys. Rev. C 84, 067301 (2011).
Prof. Luca Salasnich
U. Padova
Dr. B. Julia-Diaz
2012
15 Nov 2012 (507)
Desorption dynamics of photoexcited atoms in helium nanodroplets Abstract Superfluidity is a widely known and accepted phenomenon displayed by quantum liquids such as helium at low temperatures. However, it is not completely clear how superfluidity appears at the microscopic scale and whether a helium cluster made of a few thousand atoms presents all the features characteristic from superfluid behavior. The motion of a silver atom inside a helium nanodroplet upon photoexcitation presents a unique opportunity to probe superfluidity in finite clusters, both experimental and theoretically. Because the silver atom resides in the bulk of the drop, the velocity at which it is expelled depends critically on the interaction with the surrounding helium and the damping it introduces. In this talk I will present results for the dynamical desorption of silver computed by means of a time-dependent density functional approach. This allow us to examine the behavior of He excitations during the process and compare the limiting velocity of the impurity with the experimental data. David Mateo
ECM
08 Nov 2012 (507)
High momentum components in the nuclear symmetry energy Abstract The short-range and tensor correlations associated to realistic nucleon-nucleon interactions induce a population of high-momentum components in the many-body nuclear wave function.We study the impact of such high-momentum components on bulk observables associated to isospin asymmetric matter. The kinetic part of the symmetry energy is strongly reduced by correlations when compared to the non-interacting case. The origin of this behaviour is elucidated using realistic interactions with different short-range and tensor structures. Arianna Carbone
ECM
24 Oct 2012 (507)
Strongly correlated ultracold bosons as impurities immersed in a Bose-Einstein condensate Abstract Impurities, such as fermions or ions, immersed in a cloud of weakly interacting bosons forming a condensate have attracted recent interest because they conform versatile, highly controllable, and experimentally feasible systems for studying quantum correlations. In this talk I will discuss an exact many body description of a mixture of ultracold bosons in which a few strongly interacting atoms play the role of impurities immersed in a second species of a much bigger cloud of weakly interacting atoms. The latter species acts as a tunable environment, whose effect over the impurities can be controlled through the interspecies interactions. What is the behaviour of the quantum correlations within or between both species through the process of phase separation? How do they behave along with the dynamics of the impurities within the environment? Can we mimic the tools of quantum optics to analyse these quantum correlations? Within the introduced theoretical framework I will offer answers to these questions. I will also derive a simple semiclassical description of the system and henceforth discuss the experimental feasibility and technological applications of such a system. Dr. Miguel Angel Garcia March
ECM
8 Oct 2012 (507)
Gaussian Expansion Method and application to 4He tetramer system Abstract Many important problems in physics can be addressed by solving with high precision, Schroedinger equation for few-body systems. For the study of such problems with accurate calculations required, the Gaussian Expansion method (GEM), an ab initio variational method for few-body systems, was proposed by Kamimura [1]. When one proceeds to four-body systems, calculation of the Hamiltonian matrix elements become much laborious. In order to make the four-body calculation tractable even for complicated interactions, I proposed the infinitesimally-shifted Gaussian lobe basis function [2]. The GEM with the techinique of the infinitesimally-shifted Gaussian lobe basis function have been applied to various three-, four- and five-body calculations in hypernuclei, the four-nucleon system, ultra cold atom systems, etc. In this seminar, I will give a talk about our method, GEM, and application to ultra cold atom physics, especially, tetramer of 4He atoms using realistic 4He-4He atomic potential. [1] M. Kamimura, Phys. Rev. A38 (1988) 621. [2] E. Hiyama, Y. Kino and M. Kamimura, Prog. Part. Nucl. Phys. 51 223 (2003). Dr. Emiko Hiyama
RIKEN (Japan)
Prof. A. Parreño
26 Jun 2012 (505)
Nuclear physics from first principles: a status report Abstract I will discuss recent progress in calculating nuclear physics interactions and properties using lattice QCD. I will focus on an area in which lattice QCD will soon be competitive with experiment; specifically, I will consider simple hypernuclear processes which are essential input into the nuclear equation of state relevant for a description of dense astrophysical objects, and very recent calculations of the spectrum of light nuclei and hypernuclei at the flavor SU(3) symmetric point. Dr. Silas Beane
U. New Hampshire
Prof. A. Parreño
20 Jun 2012 (507)
Momentum and density dependence of nuclear mean field and equation of state of nuclear matter. Abstract Nuclear mean field is the fundamental quantity in the study of nuclear matter. Momentum dependent mean field that reproduces the flow data corresponds to a value of incompressibility of the nuclear matter which is in agreement with the giant monopole resonance studies.The behaviour of the mean field at Fermi momentum is directly connected with the equation of state of nuclear matter. The existing deficiencies in our present understanding on these two important aspects,namely, momentum and density dependence of nuclear mean field shall be discussed in the present talk. Dr. T.R.Routray
U. Sambalpur
Prof. X. Vinyas
21 May 2012 (507)
How to speed up quantum adiabatic processes Abstract Quantum adiabatic processes are slow and ideally robust versus parameter variations, but often they take too long or get spoiled by noise and decoherence. I'll review different "shortcuts to adiabaticity" that speed them up for atomic transport, expansions, or internal state preparation, emphasizing our most recent results Dr. Juan Gonzalo Muga
U. Pais Vasco
Prof. Joan Martorell
25 Aprl 2012 (507)
Heavy meson phenomenology in a constituent quark model Abstract An investigation of heavy meson properties within the framework of a nonrelativistic constituent quark model is presented. We study possible assignments of the new particles as q q states. Besides meson spectra, we calculate other properties that can provide valuable information on the meson structure as electromagnetic decays and strong and weak reactions. The description of theoretical approaches used and the discussion of some relevant results, comparing them with the experimental data and also with the results coming from different theoretical approaches, can be followed along the talk. D. Jorge Segovia
U. Salamanca
Dr. B. Julia-Diaz
16-19 Aprl 2012 (507)
Curs: Emergent Phenomena on quantum many-body physics Abstract Everyone is familiar with single particle quantum mechanics from course work: we all learn about quantum tunneling through a barrier, probability waves, and the Hydrogen atom as undergraduates,and move on as graduate students to path integrals, the Dyson series, and density matrix formalism. But what are the quantum properties of many particles? Is it enough to write down the symmetrization postulate and decide that the Universe is divided into bosons and fermions, and derive a quantum version of statistical mechanics? Or, is there more to the story? In this course, we will explore the new, emergent properties that appear in quantum many body systems, from quantum phase transitions to vortices in quantum hydrodynamics. Prof. Lincoln D. Carr
Colorado School of Mines & U. Heidelberg
Dr. B. Julia-Diaz
1 Feb 2012 (507)
A new interpretation for the Ds2(2573), the prediction of novel exotic charmed mesons and narrow N*, Lambda* resonances around 4.3 GeV Abstract In this talk we review the vector-vector interaction within the hidden gauge formalism in a coupled channel unitary approach. We study the vector-vector interaction for all the sectors not studied before: /C/= 0; /S/ = 1 (hidden-charm), /C/= 1, /S/= 1, and the flavor exotic sectors /C/= 1; /S/= -1,2 and /C/=2; /S/= 0,1,2. By looking for poles in the complex plane, we find nine states, four of them in the /C/= 1; /S/= 1 sector, where one can be identified with the /D//s/2*(2573) and it is interpreted as a /D/*/K/* molecular state. The other five resonances are found in the flavor exotic sectors /C/ = 1; /S/ = -1, /C/ = 2; /S/ = 0,1 and can be considered as /D/*/K?/*, /D/*/D/* and /D//s/*/D/* molecular states. Nevertheless, there is not experimental evidence of such states yet. In addition, a series of meson-baryon dynamically generated relatively narrow N^* and Lambda^? resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted resonances in ppbar collisions for PANDA at the forthcoming FAIR facilities. Dr. Raquel Molina
IFIC (Valencia)
Prof. A. Ramos
18 Jan 2012 (507)
Nuclear Forces in Chiral EFT Abstract In recent years, there has been substantial progress in the derivation of nuclear forces from Chiral Effective Field Theory (EFT). Accurate two-nucleon forces has been constructed at next-to-next-to-next-to-leading order (N3LO) and applied to nuclear few and many body systems. I will make a short introduction to Chiral EFT and show how nuclear forces emerges in this framework showing some results. I will also give some remarks about multi-nucleon forces and problems still open. Dr. David R. Entem
U. Salamanca
Dr. B. Julia-Diaz
2011
21 Dec, 2011, 11:45 (507)
Seeing topological order with ultracold atoms Abstract Topological phases of matter are a field of increasing interest because of their potential technological applications ranging from sensitive detectors to quantum computation. Their observation has been up to now, however, limited to indirect measurements due to the non-local character of the corresponding order parameters. We have developed a general method to directly observe a topological phase with cold-atom systems on optical lattices. I will first introduce the idea of topological order and then discuss our proposal to realize a characteristic topological model introduced by Haldane and how to detect it in setups of ultracold atoms confined in optical lattices. E. Alba et al., Phys. Rev. Lett 107, 235301 (2011). Dr. J. Mur-Petit
CSIC

Dr. B. Julia-Diaz
14 Dec, 2011, 11:45 (507)
Elementary excitations in homogeneous Neutron Star matter. Abstract The elementary excitations of superfluid matter below the crust of Neutron Stars are relevan for many phenomena and properties, like neutrino mean free path, heath capacity, thermal conductivity and others. I will present a study of the spectral functions of these elementary excitations. The theory is based on the conserving approximation scheme, generalized to the superfluid case. We apply the method to the proton and electron components, where both pairing and Coulomb interactions are introduced. The interplay of these two interactions in determining the overall structure of the spectrum and of the corresponding strength functions is discussed in detail. I will discuss the apearence of a pseudo-Goldstone mode, characterized by a sharp peak in the strength function, and whose velocity is determined by both Coulomb and pairing interaction. This mode merges into the usual Goldstone mode when the Coulomb interaction is switched off, i.e. in pure superfluid, where it is a consequence of the breaking of gauge invariance. Also the branch corresponding to the pair-breaking mode is clearly identified. The pseudo-Goldstone and the pair-breaking mode undergo a quasi-crossing close to twice the pairing gap Delta, above which, at increasing value of the momentum, the upper pseudo-Goldstone branch merges into the sound mode of the normal fluid, while the lower pair-breaking mode corresponds to the over-damped mode also present in the normal fluid. At increasing value of the pairing gap the spectrum above 2*Delta shrinks and finally disappears at large enough value of the gap. Besides these branches, the electron plasmon appears at higher energy. Even at moderately values of the gap, such as 100-200 KeV, the electron plasmon mode actually disappears. The nuclear particle-hole interaction for the proton component is briefly discussed and it is argued that its role is marginal. Prof. M. Baldo
INFN, Catania

Prof. X. Vinyas
30 Nov, 2011, 11:45 (507)
Adsorption of classical and quantum fluids on nanostructured substrates from atomistic simulations Abstract I will illustrate some recent applications of computational methods (based on semi-empirical and "ab initio" Density Functional theory, and Grand Canonical Monte Carlo techniques) to the adsorption of classical and quantum fluids on substrates that are structured at the nanoscale. An essential ingredient of such calculations is the adatom-substrate potential: the importance of "ab initio" electronic structure calculations in computing the van der Waals contribution to the adatom-surface interactions will be discussed, which allow to obtain more accurate and reliable physisorption potentials. Dr. F. Ancilotto
U. Padova

Dr. M. Pi
23 Nov, 2011, 11:45 (507)
Supersolidity in 4He: a Path Integral Monte Carlo study Abstract The existence of a supersolid state of matter, that is a phase characterized at the same time by crystalline order and superfluidity, has been speculated for many decades. In the last years, the observation of non classical rotati onal inertia effects in samples of solid $^4$He [1] has notably increased the interest in the topic of supersolidit y. However, the interpretation of the experimental data is rather difficult and a model able to give an exhaustive description of the supersolidity phenomenon is still lacking. From the theoretical point of view, Quantum Monte Car lo techniques have been widely used in the microscopic study of quantum crystals. In particular, Path Integral Mont e Carlo turns out to be one of the most powerful method in the study of solid $^4$He, providing an easy picture for superfluidity in many-bosons systems and giving exact results for the averages of the physical observables. In this talk, I will discuss the quantum properties of solid $^4$He as obtained in Path Integral Monte Carlo simula tions. After a short introduction of the physical system and of the computational technique, I will show results of the Bose-Einstein condensation and superfluidity properties of the solid sample, considering different microscopic configurations of the $^4$He atoms: the perfect crystal, the crystal with vacancies and the amorphous solid. The m ain objective of this study is to investigate which of these models provides results in better agreement with the e xperimental measurements [2]. [1] Kim and Chan, Nature 425, 227 (2004). [2] Rota and Boronat, arXiv:1110.3988 (2011). Mr. R. Rota
UPC

Dr. A. Polls
16 Nov, 2011, 11:45 (507)
Semiclassical approach to pairing in finite Fermi systems: nuclei, neutron stars and cold atoms Abstract Two issues are treated in this talk: (i) the generic fact that if a fermionic superfluid in the BCS regime overflows from a narrow container into a much wider one, pairing is much suppressed at the overflow point. Physical examples in cold atoms, neutron stars and nuclei where this feature may play an important role are discussed. (ii) A Thomas-Fermi (TF) approach to inhomogeneous superfluid Fermi-systems is presented and shown that it works well in cases where the Local Density Approximation (LDA) breaks down. Prof. X. Viñas
ECM

9 Nov, 2011, 11:45 (507)
Ansatz for the many-body function in a harmonic trap: from few to many... Abstract Is it possible to reproduce and understand the properties of a many-body system by a generalization of the exact function of a single pair? How 'different' is 'more'? I develop an analytical many-body wave function to accurately describe the crossover of a one-dimensional bosonic system from weak to strong interactions in a harmonic trap. The explicit wave function, which is based on the exact two-body states, consists of symmetric multiple products of the corresponding parabolic cylinder functions, and respects the analytically known limits of zero and infinite repulsion for arbitrary number of particles. For intermediate interaction strengths we demonstrate, that the energies, as well as the reduced densities of first and second order, are in excellent agreement with large scale numerical calculations. Mr. I. Brouzos
ILP, Hamburg

Dr. B. Julia-Diaz
14 Oct, 2011, 11:45 (507)
Nuclear Physics from Lattice QCD TALK Abstract Recent Lattice QCD techniques and results applied to Nuclear Physics will be reviewed, including the extraction of two-body bound states. Prof. Martin Savage
U. Washington

Prof. A. Parreño
5 Oct, 2011, 11:45 (507)
Comparative study of three-nucleon potentials in nuclear matter Abstract A new generation of local three-body potentials providing an excellent description of the properties of light nuclei, as well as of the neutron-deuteron doublet scattering length, has been recently derived. We have performed a comparative analysis of the equations of state of both pure neutron matter and symmetric nuclear matter obtained using these models of three-nucleon forces. None of the considered potentials simultaneously explains the empirical equilibrium density and binding energy of symmetric nuclear matter. However, two of them provide reasonable values of the saturation density. The ambiguity concerning the treatment of the contact term of the chiral inspired potentials is discussed. Mr. Alessandro Lovato
SISSA, Italy

Dr. A. Polls
21 Sep, 2011, 11:45 (507)
Hyperons in massive neutron stars: test of hadronic physics at high densities Abstract The constituents of dense matter in neutron stars are still far from being understood. As strangeness is not conserved in weak interactions, and timescales associated with neutron stars are much greater than those associated with weak interactions, the conversion of nucleons to hyperons in the neutron star core is energetically favoured. The highest neutron star mass that can be supported depends crucially on its constituents; presence of additional degrees of freedom such as hyperons above nuclear saturation density results in a softer EoS and a smaller maximum mass neutron star. A neutron star containing hyperons in its interior cannot be more massive than about 1.8 M⊙ according to existing models. Recently, Shapiro delay measurements from radio timing observations of a binary millisecond pulsar indicated a mass of 1.97 ± 0.04 M⊙ of the neutron star. Such measurements of large neutron star masses provide strong constraints on the presence of hyperons. It is to be investigated whether the non-existence of hyperons in massive neutron stars is an artifact of our limited understanding of the behaviour of hadrons at high densities. Dr. Debarati Chatterjee
University of Heidelberg, Germany

Dr. L. Tolos
05 Jul, 2011, 11:45 (507)
Injection of atoms and molecules into a free-standing superfluid helium fountain Abstract Copper atoms and Cu2 molecules are produced by laser ablation in a cold helium gas at 1.7 K and their spatial and frequency domain visualization was carried out by using the laser induced fluorescence technique. Due to collisions in the cold buffer gas, Cu/Cu2 thermalize effectively within 1 ms of their creation, after which their spatial distribution expands slowly due to thermal diffusion. A 200 micrometer diameter superfluid helium fountain is operated within 1 mm distance from the ablation target and the interaction of Cu/Cu2 with the fountain is characterized. The spatial images show that Cu atoms pileup in front of the fountain and a deficit of Cu atoms develops behind the fountain. Cu2 on the other hand accumulates in the fountain. The deficit exceeds the pileup in the front indicating an additional loss channel for Cu atoms. Ab initio electronic structure calculations were carried out to characterize the Cu-He interaction giving an estimate for the binding energy, 6.6 K. Cu2 interaction is about twice as deep. Time-independent bosonic density functional theory (DFT) predicts that Cu is heliophobic and Cu2 heliophilic. By using the time-dependent formalism, it was established that the thermal kinetic energy of classical Cu atoms is not sufficiently high for penetrating the fountain whereas Cu2 penetrate the fountain. The calculations demonstrate that the atoms accelerate significantly near the fountain surface due to the Cu/Cu_2 H en attraction. The atom/molecule looses all of its kinetic energy at the fountain surface through a multi-phonon process and finally localizes at the fountain surface. Dr. Jussi Eloranta
Department of Chemistry and Biochemistry, California State University

Dr. M. Pi
29 Jun, 2011, 11:45 (507)
Symmetry energy effects in finite nuclei and nuclear matter Abstract The symmetry energy and its density dependence play an important role to understand the structure of systems as diverse as atomic nucleus and the neutron star. In this talk, the effect of symmetry energy constrained from the measured neutron skin thickness of finite nuclei on neutron star properties and liquid gas phase transition in hot asymmetric nuclear matter, using relativistic mean field (RMF) model will be discussed. Dr. Bharat Sharma
ECM

Dr. X. Viñas
31 May, 2011 (507)
Warm alpha-nucleon matter Abstract Properties of warm dilute alpha-nucleon matter are studied in a variational approach in the Thomas-Fermi approximation, starting from an effective nucleon-nucleon interaction. The equation of state of such a matter, its symmetry energy and incompressibility are calculated and compared to those obtained from the model-independent S-matrix approach. Prof. J. N. De
Saha Institute of Nuclear Physics, Kolkata, India

Dr. X. Viñas
30 May, 2011 (507)
A multiscale computational method to simulate flow of fluids with a memory effect Abstract We present a multiscale computational method to simulate flow of fluid systems with a large spatial extent. We simulate small parts of the system using molecular dynamics, and only occasionally pass information among these parts based on a continuum fluid mechanics framework. This method does not rely on any constitutive equation, and hence is well-suited for a fluid the flow of which suffers from memory-effects. In addition, the simulation scheme can be parallelized in the sense that the molecular dynamics simulations of the different parts of the system can be performed on several individual computers. Prof. S. De
Indiana University Southeast

Dr. X. Viñas
25 May, 2011 (507)
A century of nuclear physics ... and beyond! TALK Abstract In May 1911, Rutherford postulated his atomic model based on the Geiger-Mardsen experiment. At the center of the atom, a new physical system was born: the atomic nucleus. This marked the birth of a new discipline, nuclear physics, that bloomed shortly after its inception and had a major historical impact. In this talk, I will briefly comment on the history of nuclear physics, discuss some of its applications, and, most of all, emphasize the future perspectives of nuclear theory and experiments in the XXIst Century. Dr. Arnau Rios
U. Surrey

Dr. B. Julia-Diaz
18 May, 2011 (507)
The nuclear Yukawa model on a lattice Abstract We present the results of the quantum field theory approach to the nuclear Yukawa model obtained by standard lattice techniques. We have considered the simplest case of two identical fermions interacting via a scalar meson exchange. Calculations have been performed using Wilson fermions in the quenched approximation. We found the existence of a critical coupling constant above which the model cannot be numerically solved. The range of the accessible coupling constants is below the threshold value for producing two-body bound states. Two-body scattering lengths have been obtained and compared to the non-relativistic results. Prof. Jaume Carbonell
LPSC, Grenoble

Dr. J. Soto
6 Abril 2011 (507)
Bound states in Lattice QCD. The H-dibaryon Abstract I will discuss recent results of baryon-baryon interactions at low energies obtained by the NPLQCD Collaboration, at a pion mass of ~ 390 MeV, with a lattice volume of L ~ 2.5 fm and a lattice spacing of ~ 0.123 fm. Studying the volume dependence of our simulations performed at four different volumes, L ~ 2.0, 2.5, 3.0 and 3.9 fm, I will present evidence for a bound I=0, J=0, s=-2 state (the H-dibaryon) , as well as, present constraints for its existence at the physical pion mass. Dr. Assumpta Parreño
ECM

29 Mar 2011 (507)
Dynamical symmetry breaking in dual-core nonlinear systems Abstract Fundamental models of various physical media based on configurations with two parallel cores (waveguides) amount to systems of linearly coupled equations. A known example is the model of dual-core optical fibers or planar waveguides, which amounts a system of coupled nonlinear Schroedinger (NLS) equations. In such systems, obvious symmetric soliton solutions lose their stability through symmetry-breaking bifurcations, when the energy exceeds a certain critical value. The bifurcations simultaneously gives rise to stable asymmetric solitons. The talk aims to present an overview of basic models, results, and physical applications of the symmetry-breaking phenomena in conservative and dissipative nonlinear media. Prof. Boris Malomed
Tel Aviv University

Dr. B. Julia-Diaz
23 Mar 2011, 11:45 (507)
Quantum simulations of thermodynamic and kinetic properties of strongly coupled electromagnetic and quark-gluon plasmas. Abstract Determining the properties of strongly coupled hydrogen, electron – hole or quark – gluon plasmas is one of the main challenges of strong-interaction physics.  We propose a stochastic simulations of thermodynamic and kinetic properties   of the strongly correlated Coulomb systems in a wide range of temperature, density and quasi-particle masses. We use the direct quantum path integral Monte Carlo method (PIMC) developed for finite temperature within Feynman formulation of quantum mechanics to do calculations of internal energy, pressure and pair correlation functions. Dr. Vladimir Filinov
JIHT

2 Feb 2011, 11:45 (507)
Muonic hydrogen at finite temperature with of non-relativistic effective field theories Abstract At high temperatures QCD undergoes a phase transition into the so called quark-gluon plasma (QGP). At temperatures above this phase transition heavy quarkonium (HQ) states melt, and it has been proposed that the disappearance of different HQ states can be used as a thermometer for heavy-ion collisions at accelerators that try to create the QGP experimentally. However, our current understanding of HQ at finite temperature still does not allow to do this in a reliable way. Muonic hydrogen shares a number of properties with HQ that make the study of muonic hydrogen at finite temperature a very good toy model for understanding HQ. In addition it is nowadays produced in large samples and hence the finite temperature effects on it may also be measured experimentally. In this talk I will review non-relativistic effective field theories and the way how they are able to easily conect QCD with potentials models. Next I will use these techniques to study muonic hydrogen at finite temperature and I will also comment their application to HQ. Mr. Miguel Angel Escobedo
ECM
Dr. J. Soto
19 Jan 2011, 11:45 (507)
Anomalous isentropic effects in ultra-cold attractively interacting fermions loaded into an optical lattice Abstract Dilute atomic gases cooled down to quantum degeneracy constitute an exceptional toolbox to investigate quantum many-body phenomena. In this sense, the high control and tunability achieved in ultra-cold gases loaded into an optical lattice ---a standing wave created by interfering two counter-propagating laser beams acting on the atoms as a spatially periodic potential--- turn them into promising candidates to simulate many-body systems in the strongly correlated regime.\\ In this regime the correlations existing between particles are revealed not only in the ground state and low-lying excitations but also they can be manifested as counterintuitive thermodynamic effects. We have studied theoretically an ultra-cold mixture of attractively interacting fermionic atoms loaded into an optical lattice at finite entropy. In this system a redistribution of the entropy leads to an anomalous expansion of the cloud when adiabatically increasing the attractive interaction, as a consequence of the enhancement of pairing between particles. This effect has been observed experimentally in qualitative agreement with the theoretical analysis [1].\\ In this talk, I will briefly introduce how optical lattices are experimentally realized and the model used to describe these systems (the celebrated Hubbard model). Next I will focus on the different approaches we have performed to analyze theoretically the thermodynamics of the fermionic mixture in the presence of the lattice.\\ [1] L. Hackermüller, U. Schneider, M. Moreno-Cardoner, T. Kitagawa, Th. Best, S. Will, E. Demler, E. Altman, I. Bloch, and B. Paredes, Science \bf 327 \rm, 1621 (2010) Ms. Maria Moreno-Cardoner
U. Munich
Dr. B. Julia-Diaz
2010
21 Dec 2010, 11:45 (507)
Boltzmann equation for the collective modes of cold trapped Fermi gases Abstract In this seminar I will talk about three methods to solve the Boltzmann equation: the method of averages, the moments method and the test-particle method. The first two are widely used semi-analytical methods, whereas the latter is a numerical one that has been traditionally used in nuclear physics to simulate heavy-ion collisions, but is rarely used for cold trapped atoms. I will discuss some results obtained with these methods for the collective modes in trapped Fermi gases at finite temperature and in the normal fluid phase. In particular, I will present two studies: the dipole oscillations in multi-component fermionic mixtures via the averages method and the comparison between moments and numerical method for the quadrupole mode in a two-component mixture. This comparison shows that the moments method at lowest order (that is the commonly used one) gives qualitatively good results. However, it is necessary to go beyond the lowest order approach to obtain quantitatively reliable predictions for modes, as the quadrupole mode, that are sensitive to spatial non-homogeneities. Dr. Silvia Chiacchiera
Centro de Fisica Computacional, U. Coimbra
Dr. B. Julia-Diaz
15 Dec 2010, 11:45 (507)
DN interaction from meson exchange Abstract A model of the DN interaction is developed in close analogy to the meson-exchange $\bar KN$ potential of the Juelich group utilizing SU(4) symmetry constraints. The main ingredients of the interaction are provided by vector meson exchange and higher-order box diagrams. The coupling of $DN$ to the $\pi\Lambda_c$ and $\pi\Sigma_c$ channels is taken into account. The interaction model generates the $\Lambda_c$(2595) resonance dynamically as a $DN$ quasi-bound state. Results for $DN$ total and differential cross sections are presented and compared with predictions of two interaction models that are based on the leading-order Weinberg-Tomozawa term. Some features of the $\Lambda_c$(2595)$ resonance are discussed and the role of the near-by $\pi\Sigma_c$ threshold is emphasized. Selected predictions of the original $\bar KN$ model are reported too. Specifically, it is pointed out that the model generates two poles in the partial wave corresponding to the $\Lambda$(1405) resonance. Dr. Laura Tolós
Institut de Ciències de l'Espai
Dr. B. Julia-Diaz
24 Nov 2010, 11:45 (507)
Dressing many-body lattice systems of ultracold atoms by shaking Abstract Strong time-periodic potential modulations (beyond the regime of linear response) can be a robust and powerful tool for the manipulation of many-body systems as they are realized experimentally with ultracold atoms. Such novel control schemes are reminiscent of manipulating internal atomic or molecular degrees of freedom by means of coherent radiation. We describe them theoretically by an approach similar to the dressed atom picture, taking into account the possibly strong interaction between the particles [1-3]. A striking example is given by a recent experiment (proposed in [1]): In a system of bosonic atoms in an optical lattice the transition from a superfluid to a Mott-insulator (and back) has been induced by smoothly switching on (and off again) the amplitude of a time-periodic acceleration of the whole lattice potential [4]. This phenomenon relies on a complex dynamics being a combination of both diabatic and adiabatic following of many-body Floquet states [1,3]. In a recent proposal, we suggest to induce a sign change of the hopping matrix elements in a system of repulsively interacting bosons in a triangular lattice. The sign change can be achieved by dressing the system with a fast elliptical lattice acceleration [5]. The system then behaves as a frustrated antiferromagnet --- a classical one in the limit of weak interaction and a quantum antiferromagnet (with large coupling matrix elements on the order of the boson hopping) in the limit of hard-core bosons. For the latter, N\'eel-ordered (spiral or staggered) superfuid phases and gapped spin-liquid phases are predicted [5-6]. [1] A. Eckardt, C. Weiss, and M. Holthaus, "Superfluid-Insulator Transition in a Periodically Driven Optical Lattice", Phys. Rev. Lett. 95, 260404 (2005) [2] A. Eckardt and M. Holthaus, "AC-induced superfluidity", EPL 80, 50004 (2007) [3] A. Eckardt and M. Holthaus, "Avoided level crossing spectroscopy with dressed matter waves", Phys. Rev. Lett. 101, 245302 (2008) [4] A. Zenesini, H. Lignier, D. Ciampini, O. Morsch, and E. Arimondo, "Coherent Control of Dressed Matter Waves", Phys. Rev. Lett. 102, 100403 (2009) [5] A. Eckardt, P. Hauke, P. Soltan-Panahi, C. Becker, K. Sengstock, and M. Lewenstein, "Frustrated quantum antiferromagnetism with ultracold bosons in a triangular lattice", EPL 89, 10010 (2010). [6] R. Schmied, T. Roscilde, V. Murg, D. Porras, and J. I. Cirac, "Quantum phases of trapped ions in an optical lattice", New J. Phys. 10, 045017 (2008) Dr. Andre Eckardt
ICFO
Dr. B. Julia-Diaz
17 Nov 2010, 11:45 (507)
Dipolar condensates in a toroidal trap Abstract In contrast to usual alkali Bose-Einstein condensates, where the s-wave contact interaction is dominant, dipolar condensates show a new kind of interaction: the dipolar interaction, which is anisotropic, non-local and long-range. We will show that when such a condensate is confined in a toroidal trap, the anisotropic character of the interaction is enhanced and the condensate shows an azimuthal density distribution depending on the relative strength of the two interactions. For small scattering lengths, this density distribution resembles that of a condensate in a ring-shaped double-well potential, but now the potential barrier separating the two wells is self-induced by the dipolar interaction. Although the density is not uniform along the torus, the system admits vortex states and persistent currents. In addition, the self-induced double well is capable of sustaining Josephson oscillations, as well as a self-trapping regime. Ms. Marta Abad Garcia
ECM

27 Oct 2010, 11:45 (507)
Evolution of the excited electron bubble in liquid-helium and the appearance of fission-like processes Abstract When an electron is injected into liquid-helium, it forces open a cavity from which the helium atoms are excluded. The electron can then be photoexcited to a 1P state, triggering a dynamical process in which the surrounding helium atoms adapt to the excited electron wavefunction. We have studied the evolution of an excited electron bubble in superfluid helium and found that the relaxation path it follows strongly depends on pressure. While for pressures below 1 bar the electron bubble can radiatively decay to a deformed metastable state and then relax to the spherical ground state, we have found that above 1 bar the bubble splits in two distinct baby bubbles in the course of the dynamical evolution, pointing to a different relaxation path in which the electron may be localized in one of the baby bubbles while the other collapses, allowing for a pure radiationless de-excitation. The dynamics of the electron bubble has been computed within a density functional approach for liquid-helium and an adiabatic aproximation for the electron evolution. Results for the evolution of the excitated 2P electron, in which the adiabatic approximaion breaks at an early stage of the evolution,will be also shown. Mr. David Mateo
ECM

20 Oct 2010, 11:45 (507)
Superconducting quantum circuits: Quantum information and circuit quantum electrodynamics Abstract Quantum effects in superconducting circuits have been a focus of intense study in the past years. Progress has been made to couple several qubits to each other and to perform quantum gates between them. Coupling to on-chip superconducting resonators has also been achieved. This has opened the possibility to couple remote qubits using the resonator, and it has allowed studying the qubit-photon interaction to regimes of parameters unattainable in experiments in the field of cavity quantum electrodynamics (QED) in quantum optics. In this talk I will present the superconducting flux qubit in the context of circuit QED. First the coherent coupling of a flux qubit and an LC resonator will be described. In the second part of the talk a system consisting in another flux qubit very strongly coupled to a resonator will be presented, and the observation of effects beyond the rotating wave approximation in the Jaynes Cummings model in this system will be shown. Dr. Pol Forn Diaz
Delft University of Technology
Mr. J.M. Escartin
13 Oct 2010, 11:45 (507)
Ultra-intense laser opportunities Abstract "Laser light" and "ionizing radiation" are traditionally completely unconnected concepts. However, in the early 80’s Tajima and Dawson predicted theoretically that electrons can be accelerated in plasmas generated by ultra-intense laser pulses. The later development of the Chirped Pulse Amplification (CPA) technique allowed Tajima's prediction becoming a reality. In our days, electrons, as well other particles like protons, can be accelerated using lasers. Monochromatic electron beams of 100 MeV [and 1pC charge] have been already produced. Moreover, reaching 1 GeV electron energies is now also possible. These facts open the door to the design of a new class of laser-based accelerators, which represent major prospect of improvement in accelerators technologies (much shorter accelerations distances, more compact equipments, high charge beams, etc.). In this talk, we will introduce the Centro de Láseres Pulsados (CLPU), at Salamanca, where shortly these ultra-intense lasers will be installed, allowing the Spanish scientific community having access to nuclear laser physics, laser-matter interactions physics, and laser-based accelerator technology. Dr. David Bote Paz
University of Salamanca
Dr. B. Julia-Diaz
5 Oct 2010, 10:00 (507)
An efficient real-space density functional algorithm TALK Abstract Prof. Eckhard Krotscheck
Linz University
Dr. M. Barranco
15 Sep 2010, 11:45 (505)
Microscopic Approach to Nucleon Spectra in Hypernuclear Non-Mesonic Weak Decay Abstract A consistent microscopic diagrammatic approach is applied for the first time to the calculation of the nucleon emission spectra in the non--mesonic weak decay of $\Lambda$--hypernuclei. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a one--meson exchange weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons and a Bonn nucleon--nucleon strong potential. Ground state correlations and final state interactions, at second order in the nucleon--nucleon interaction, are introduced on the same footing for all the isospin channels of one-- and two nucleon induced decays. Single and double--coincidence nucleon spectra are predicted for $^{12}_{\Lambda}$C and compared with recent KEK and FINUDA data. The key role layed by quantum interference terms allows us to improve Discrepancies with data remain for proton emission. Dr. Eduardo Bauer
Universidad Nacional de La Plata and IFLP CONICET
Dr. A. Parreño
30 Jun 2010, 15:00 (507)
Electromagnetic polarisabilities in lattice QCD Abstract Electromagnetic and spin polarisabilities are important in describing the quasi-static response of hadrons to the presence of of external electromagnetic fields. I will report on recent progress in determining electric polarisabilities and magnetic moments of both charged and neutral hadrons using lattice techniques. Dr. William Detmold
College of William & Mary / Jefferson Lab
Dr. A. Parreño
28/29 Jun 2010, 11:30 (507)
Bosonic Josephson Junctions Abstract Bosonic Josephson Junctions:
In the two lecture I will give an overview of the experimental work on bosonic Josephson junctions in Heidelberg and put it in context with related work. After the detailed introduction of the experimental tools allowing the realization of internal and external bosonic Josephson junctions, I will discuss in the first part of the lecture series in detail the meanfield dynamics. In the second part the quantum description in the framework of two mode Bose Hubbard model will be presented and corresponding experimental results discussed.

1) The steps towards experiments with ultracold gases
a) Generation of ultracold gases in two mode situations
b) How to look at the atoms at atom shot noise level


2) Meanfield limit of N Particles - external and internal bosonic Josephson junction
a) Meanfield description
a) Dynamics - from Rabi to Josephson physics
b) Thermal Equilibrium properties - Phase noise thermometry


3) Beyond meanfield
a) Quantum Dimer, Two mode Bose Hubbard, Lipkin-Meshkov-Glick Hamiltonian
b) Squeezing - adiabatic, diabatic
c) Quantum Metrology - atom interferometry beyond classical precision limit
-----------------------------------------------------------
Prof. Markus Oberthaler
U. Heidelberg
Dr. M. Guilleumas
16 Jun 2010, 11:45 (507)
Symmetry energy, neutron star crust and neutron star thickness Abstract We perform a systematic analysis of the density dependence of nuclear symmetry energy within the microscopic Brueckner-Hartree-Fock (BHF) approach using the realistic Argonne V18 nucleon-nucleon potential plus a phenomenological three-body force of Urbana type. Our results are compared thoroughly with those arising from several Skyrme and relativistic effective models. The values of the parameters characterizing the BHF equation of state of isospin asymmetric nuclear matter fall within the trends predicted by those models and are compatible with recent constraints coming from heavy ion collisions, giant monopole resonances, or isobaric analog states. In particular we find a value of the slope parameter L=66.5 MeV, compatible with recent experimental constraints from isospin diffusion, L=88±25 MeV. The correlation between the neutron skin thickness of neutron-rich isotopes and the slope L and curvature Ksym parameters of the symmetry energy is studied. Our BHF results are in very good agreement with the correlations already predicted by other authors using nonrelativistic and relativistic effective models. The correlations of these two parameters and the neutron skin thickness with the transition density from nonuniform to ?-stable matter in neutron stars are also analyzed. Our results confirm that there is an inverse correlation between the neutron skin thickness and the transition density. Dr. Isaac Vidaña
U. Coimbra
Dr. A. Polls
15 Jun 2010, 11:45 (507)
Nuclear symmetry energy deduced from dipole excitations: a comparision with other constraints TALK Abstract In this seminar, we briefly review the amount of general information concerning the nucleon-nucleon interaction and the nuclear equation of state (EOS) that has been extracted from giant resonances. We then focus on one of the most debated questions at present, namely the density dependence of the nuclear symmetry energy. We have investigated correlations between the parameters governing the symmetry energy, the neutron skins, and the percentage of energy-weighted sum rule (EWSR) exhausted by the Pygmy Dipole Resonance (PDR) in $^{68}$Ni and $^{132}$Sn. These correlations are found within different Random Phase Approximation (RPA) models for the dipole response, based on both a representative set of Skyrme effective forces and also meson-exchange effective Lagrangians. We show that the comparison with the experimental data has allowed to constrain the value of the derivative of the symmetry energy at saturation. We finally compare this constrain with the findings of quite different methods. Prof. Gianluca Colo
INFN Milano
Dr. X. Vinyas
7-11 Jun 2010, 11:-13: (505)
(CURSO) Chiral Effective Theory for Electromagnetic Interactions with Light Nuclei TALK Abstract Day 1: Introduction to Effective Field Theory (EFT) Discussion of EFT as a general principle. Examples from Classical Electrodynamics (Multipole expansion, Thomson scattering). Examples from Quantum Field Theory (Fermi electroweak theory, phi4 theory in six dimesions). Day 2: Chiral Symmetry and hadron-hadron interactions Chiral symmetry of QCD and the hidden nature of chiral symmetry in low-energy hadron-hadron interactions. Goldstone bosons. Chiral perturbation theory (ChiPT) as the low-energy EFT of QCD. ChiPT with baryons. ChiPT predictions for nucleon-nucleon (NN) interactions. Day 3: Why and how we iterate The problem with perturbative calculations of the NN amplitude. The Lippmann-Schwinger equation and how to solve it. ChiPT calculation of the leading-order NN potential. Renormalization of the leading-order potential. Sub-leading potentials. Predictions for NN and NNN scattering. Issues regarding renormalization. Day 4: Electron scattering from light nuclei ChiPT predictions for nucleon electromagnetic form factors. Introduction to electron-deuteron scattering. Predictions for deuteron electromagnetic form factors in chiral effective theory. Form factors for the trinucleons and electron-induced breakup of the deuterium nucleus. Day 5: Compton scattering from light nuclei Introduction to Compton scattering on the proton and neutron; overview of proton Compton experiments. ChiPT predictions for Compton scattering from the proton. ChiPT predictions for Compton scattering from the deuteron. Comparison with data. Issue associated with the nuclear bound state. ChiPT predictions for Compton scattering from Helium-3. Compton scattering outlook. Dr. Daniel Phillips
Ohio University
Dr. A. Parreño
19-22 Apr 2010 (507)
(CURSO, MASTER PHOTONICS) Light induced control of cold atoms Abstract COURSE CONTENTS: 1. Maxwell’s demon 2. The atom diode 3. The magic mirror: stopping and cooling particles by moving barriers 4. Shortcut to adiabaticity 5. Time and clocks 6. Atomic clocks, interferometers and cold atoms 7. Arrival times and atomic fluorescence 8. Trapped ions in metrology and quantum information 9. Einstein beyond E=mc2 10. Zeno effect Prof. J. G. Muga
U. Pais Vasco
Dr. J. Martorell
7 Apr 2010, 11:45 (507)
Nucleon-Nucleon Interactions from the Quark Model TALK Abstract We report on investigations of the applicability of non-relativistic constituent quark models to the low-energy nucleon-nucleon (NN) interaction. The major innovations of the resulting NN potential are the use of the $^3$P$_0$ decay model and quark model wave functions to derive nucleon-nucleon-meson form-factors, and the use of a colored spin-spin contact hyperfine repulsive core rather than the heavy meson exchange mechanism used in the meson exchange theory of nuclear forces. We assess the ability and limitations of the model to reproduce experimental free NN scattering phase shifts and $^1$S$_0$ scattering lengths and effective ranges. We also present the nuclear matter Equation of State in the Brueckner-Hartree-Fock approximation for the potential. Theoretical implications and plans for future study are discussed. Dr. Clark Downum
ECM
Dr. J. Soto
17 Mar 2010, 11:45 (507)
The magic of getting peaks with cuts in experiments: An explanation for the "Theta+ pentaquark" peak. Abstract We present a calculation of the $\gamma d \to K^+ K^- n p $ reaction with the aim of seeing if the experimental peak observed in the $K^+ n$ invariant mass around 1526 MeV, from where evidence for the existence of the $\Theta^+$ has been claimed, can be obtained without this resonance as a consequence of the particular dynamics of the process and the cuts applied in the experimental set up. We find that a combination of facts leads indeed to a peak around 1530 MeV for the invariant mass of $K^+ n$ without the need to invoke any new resonance around this energy. This, together with statistical fluctuations that we prove to be large with the statistics of the experiment, is likely to produce the narrower peak observed there. Prof. Eulogio Oset
Universidad de Valencia
Dr. A. Ramos
11 Mar 2010, 11:45 (505)
Neutron Star Structure with Hyperons and Quarks TALK Abstract The high-density nuclear equation of state within the Brueckner-Hartree-Fock approach is discussed. Particular attention is paid to the effects of nucleonic three-body forces, the presence of hyperons, and the joining with an eventual quark matter phase. The resulting properties of neutron stars, in particular the mass-radius relation, are determined. It turns out that in our approach the maximum mass is about 1.7 solar masses and that stars heavier than about 1.4 solar masses contain necessarily quark matter. Dr. Hans-Josef Schulze
INFN Catania Italia
Dr. A. Polls
27 Jan 2010, 11:45 (507)
Radial distributions in heavy-light mesons and $B^0$-$\bar B^0$ mixing amplitude in the static limit. Abstract Phenomenology of the heavy-light mesons is investigated by using QCD simulations on the lattice --- in particular, the light quark dynamics when the heavy quark is infinitely heavy. We present a new method which allows for the first lattice determination of the pion emission in the transition between the first excited and the lowest lying heavy-light meson. High accuracy results for coupling to pions also obtained through improvements over previous lattice calculations. These couplings are necessary ingredients for the description of heavy-light mesons by an effective theory known as the Heavy Meson Chiral Perturbation Theory. They are also essential in the chiral extrapolations of the lattice results for the quantities relevant to the $B$-physics phenomenology. We then make a detailed study of the matrix elements of all parity conserving four-quark $\Delta B=2$ operators which enter the theoretical description of the $B^0$-$\bar B^0$ mixing amplitude in the Standard Model, and in its supersymmetric extensions. This is the first such study in fully unquenched lattice QCD. With an improved static quark propagator, the spurious mixing of operators computed on the lattice is much smaller with respect to what has been done in the past. We close with a short discussion of impact of the results on the $B$-physics phenomenology. Dr. Emmanuel Chang
U. Barcelona

2009
22 Dec 2009, 11:45 (507)
Mixtures of Bose gases confined in concentrically coupled toroidal traps Abstract A two-component Bose-Einstein condensate confined in an axially-symmetric potential with two local minima, resembling two concentric toroidal traps, is investigated. The system shows a number of quantum phase transitions that result from the competition between phase coexistence, and radial/azimuthal phase separation. The ground-state phase diagram, as well as the rotational properties, including the (meta)stability of currents in this system, are analyzed. Dr. Francesc Malet
U. Lund
Dr. M. Barranco
21 Dec 2009, 11:45 (507)
A guided tour in Non Equilibrium Green functions and an application to strongly correlated Hubbard systems Abstract In this talk I will give an introduction of the time-dependent Kadanoff-Baym equations (KBE), which are a cornerstone in microscopic theory of non-equilibrium quantum processes. We have recently solved the KBE for a Hubbard chain within different many-body approximations (Hartree-Fock, 2$^{nd}$ Born, GW and T-matrix approximations) and the results are compared to those of the exact solution. Benchmarking approximate results against exact ones allows us to address two rather fundamental issues in the non equilibrium dynamics of strongly correlated systems. I) A characterization of the performance of several standard MBAs in the non-equilibrium regime. Having a definite notion of how good a specific MBA can be is highly relevant to its application to cases (typically, infinite systems) where exact solutions are not available. Our results show that the T-matrix approximation is overall superior to the other MBAs, at all electron densities. II) A scrutiny of the whole idea of Many Body Perturbation Theory in the Kadanoff-Baym sense, when applied to finite systems. The surprising outcome of our study is that during the time evolution, the KBE develop an unphysical steady state solution. This is a genuinely novel feature of the time-dependent KBE, i.e. is not inherited from possible limitations/approximations in the calculation of the initial state. Our extensive numerical characterization gives robust evidence that the problem occurs in general, whenever MBPT is applied to finite systems, and approximate self energies based upon infinite partial summations are used. In the end I will briefly discuss the work in progress and some future directions. Marc Puig von Friesen
U. Lund
Dr. A. Polls
16 Dec 2009, 11:45 (507)
Isospin breaking effects in the dynamically generated X(3872) resonance. Abstract We have studied isospin breaking effects in the X(3872) resonance and found a natural explanation for the branching fraction of the X decaying to Jpsi with two and three pions being close to unit. Within our framework the X(3872) is a dynamically generated resonance in coupled channels. The simultaneous investigation of the X decay to D^0 Dbar^*0 and Jpsi pi pi shows that the preferred structure for the X is a slightly unbound, virtual state of D\bar D^* and D^* \bar D. We also comment on the relationship between wave functions and couplings for bound states, and apply it for the X(3872). Mr. Daniel Gamermann,
IFIC-U. Valencia
Dr. A. Ramos
4 Nov 2009, 11:45 (507)
Heaviest nuclei Abstract The production of new superheavy nuclei (Z>108) through heavy ion reactions of actinides with 48Ca is explained. The decays of these new elements are analyzed and their stability properties are discussed. Predictions of new magic numbers beyond N=126 and Z=82 are also given. Prof. Yu. Oganesyan (JINR, DUBNA)
JINR-DUBNA
Dr. X. Vinyes
28 Oct 2009, 11:45 (507)
Excitation spectra of small para-Hydrogen clusters Abstract Small (pH2)N clusters have been produced in a cryogenic free jet expansion and studied by Raman spectroscopy. Clusters with N=2-8 molecules have been unambiguously identified, and broad maxima were observed at N#13, 33, and perhaps 55, indicating the existence of magic sizes related to geometric shells. Quantum Monte Carlo methods have been used in recent years as a theoretical tool to study (pH2)N clusters. Both diffusion Monte Carlo (DMC) and path integral Monte Carlo (PIMC) calculations show that these clusters exhibit a clear structural order, with the molecules occupying concentric spherical shells, which could be related to some polyhedral arrangement. Whereas up to N#22 these calculations are substantially in agreement, for heavier clusters there are noticeable differences between DMC and PIMC magic sizes. We present here DMC simulations for clusters with N=3-40. The energies of all stabilized excitations with angular momentum from L=1 to 13 have been calculated, as well as those of the first L=0 vibrational excited state. Para-hydrogen clusters exhibit very rich spectra and no regular pattern can been guessed in terms of the angular momenta and the size of the cluster, at variance with the situation found for helium droplets. The partition function has been calculated from the excitation spectra, thus allowing for an estimate of finite temperature effects. An enhanced production is predicted for cluster sizes N=13, 26, 31 and 36, at any temperature, and also for N=19, 29 and 34 at some specific temperatures. The DMC and PIMC differences in the predicted magic sizes are thus explained as being mostly due to thermal effects. Prof. J. Navarro
CSIC-U. Valencia
Dr. M. Pi
23 Sep 2009, 11:45 (507)
Spin and charge excitations in multi-electron QDs: the strongly correlated regime Abstract Correlation among particles in finite quantum systems leads to complex behaviour and novel states of matter. Semiconductor quantum dots containing a few excess electrons (electron molecule) are a protoype system in this respect, whereby few-body correlations beyond mean-field effects can be obtained by detailed spectroscopy of their charge and spin excitations. In this seminar I will discuss our recent theoretical studies of charge and spin excitations in strongly correlated quantum dots, in connection with recent experiments, with focus on two specific aspects: 1) the development of molecular excitations of the Wigner type in low-density quantum dots; 2) the magnetic field dependence of the spin excitation relaxation time. Prof. Guido Goldoni
University of Modena and Reggio Emilia
Dr. M. Pi
16 Jul 2009, 11:45 (507) Through a phase transition in ion chains Abstract We propose an experiment to test the production of topological defects following the Kibble-Zurek mechanism on trapped ions. Ions in a harmonic trap undergo a structural second-order phase t ransition when a threshold ratio between the axial and transverse frequency of the trap is crossed. Under weakening of the transverse confinement, the system evolves from a high symmetry phase (linear chain) to a doubly-degenerated ground-state manifold (zig-zag chains), with the possible formation of topological defects (kinks, an ti-kinks, breathers). The density of defects is shown to obey the scaling predicted by the Kibble- Zurek mechanism in different configurations amenable to experimental realization Dr. A. del Campo
Imperial College (London)
Dr. N. Barberan
02 Sep 2009, 11:45 (507) Time-dependent Green's functions description of nuclear mean-field dynamics TALK Abstract The time-dependent Green's functions formalism allows for a consistent description of the time evolution of quantum many-body systems within the mean-field approximation or within more sophisticated correlated approaches. An attempt to apply this formalism to the mean-field dynamics of symmetric reactions for one-dimensional nuclear slabs will be discussed. Particular attention will be paid to the off-diagonal elements of the Green's functions and their effect on the time evolution. The importance of these will be quantified via a super-operator cut-off field technique and their relevance for the global time evolution as well as for time reversibility will be assessed. The impact of off-diagonal elements in the associated Wigner distributions will be briefly discussed. Dr. A. Rios
University of Surrey
Dr. A. Polls
20 Jul 2009, 11:45 (507) Entanglement production with trapped Bose atoms. Abstract Bose-Einstein condensate in a deep insulating optical lattice is considered. Each lattice site contains many Bose-condensed atoms. By resonance modulation of the trapping lattice field, it is possible to create in each lattice site coherent topological modes corresponding to nonground-state condensates. These modes demonstrate a rich variety of properties: dynamic phase transitions, squeezing, and entanglement. The dynamics of the modes can be regulated by means of external fields. Prof. V.I. Yukalov Dr. M Guilleumas




Generalities about the seminars:

  • By default, the seminars will be held : Wednesdays at 11:45 in "Aula Pere Pascual" (507), located in the 5th floor of the Facultat de Fisica. 
  • The speakers are expected to give 50 minutes presentations + 5 to 10 minutes for questions.
  • The audience is encouraged to raise questions which may clarify the talk at any time.
  • The speakers will preferably be either doctors or PhD students close to graduation.
  • The calendar on the right contains all the information about past, future and temptative seminars as listed above, please check it for available dates
                                                   
PREVIOUS FAN SEMINARS 2006-2007 2007-2008 2008-2009

To send any comment or question or to propose a seminar please
feel free to email the proposed title, abstract and date to Bruno Julia-Diaz, bruno@ecm.ub.es

Departament Estructura i Constituents de la Materia
Facultat de Física
Universitat de Barcelona
Diagonal, 647
08028 BARCELONA

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