| DATE |
PLACE |
TITLE |
SPEAKER |
HOST |
| 2012
|
| 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
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
|
Dr. 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!
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
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
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
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
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
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
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 |
