20 research outputs found
Fragmented condensation in Bose-Hubbard trimers with tunable tunnelling
We consider a Bose-Hubbard trimer, i.e. an ultracold Bose gas populating
three quantum states. The latter can be either different sites of a triple-well
potential or three internal states of the atoms. The bosons can tunnel between
different states with variable tunnelling strength between two of them. This
will allow us to study; i) different geometrical configurations, i.e. from a
closed triangle to three aligned wells and ii) a triangular configuration with
a -phase, i.e. by setting one of the tunnellings negative. By solving the
corresponding three-site Bose-Hubbard Hamiltonian we obtain the ground state of
the system as a function of the trap topology. We characterise the different
ground states by means of the coherence and entanglement properties. For small
repulsive interactions, fragmented condensates are found for the -phase
case. These are found to be robust against small variations of the tunnelling
in the small interaction regime. A low-energy effective many-body Hamiltonian
restricted to the degenerate manifold provides a compelling description of the
-phase degeneration and explains the low-energy spectrum as excitations of
discrete semifluxon states
Propuesta de un sistema de informatización de la gestión de colecciones paleontológicas
This document was first presented to and distributed through the attendants to a Working Session of the V Jornadas de PaleontologÃa (Valencia, november 1989) and has remained unpublished since then. By the end of 1991 a standard basic inventory card for the informatic management of palaeontological collections in Spain (Gallemà et al., 1993) was established. As this management system employs many of the codes originally stated in the former document, its publication becomes necessary and so we do in a thorough and –consequently– non updated way.
Key words: Palaeontology, Collections, Management, Informatics, Spain.El presente documento fue presentado y distribuido a los participantes en una Sesión de Trabajo de las V Jornadas de PaleontologÃa (Valencia, noviembre 1989), permaneciendo inédito desde entonces. A finales de 1991 se homologó en España una ficha básica de inventario para la gestión informática de colecciones paleontológicas (Gallemà et al., 1993). Al utilizar dicho sistema de gestión buena parte de los códigos postulados originalmente en aquel documento, se ha estimado conveniente la publicación del mismo que se hace de manera Ãntegra y –consecuentemente– no actualizada.
Palabras clave: PaleontologÃa, Colecciones, Gestión, Informática, España
The Gómez-Alba palaeontological collection of the MGB-MCNB
Es presenta el catà leg de la col·lecció paleontològica que havia pertangut al recentment traspassat Dr. Julio Gómez-Alba, antic conservador de Paleontologia del Museu de Geologia de Barcelona, actualment integrat en el Consorci del Museu de Ciències Naturals de Barcelona. La proposta de donació de la col·lecció a la ciutat de Barcelona al novembre de 2010 fou acceptada per l’Institut de Cultura de Barcelona (ICUB) en data 11 de febrer de 2011. Formada per 4.990 exemplars i 25 lots, no és la col·lecció d’un investigador en paleontologia sinó la d’un paleontòleg generalista. Molts exemplars d’aquesta col·lecció foren figurats en una guia de camp elaborada per Gómez-Alba (1988) sobre els fòssils d’Espanya i d’Europa. El catà leg és, a part d’algunes correccions menors, transcripció literal de la base de dades originalment associada a la col·lecció que –des de la seva acceptació– no ha estat actualitzada ni revisada.Se presenta el catálogo de la colección paleontológica que habÃa pertenecido al recientemente fallecido Dr. Julio Gómez-Alba, antiguo conservador de PaleontologÃa del Museo de GeologÃa de Barcelona, actualmente integrado en el Consorcio del Museo de Ciencias Naturales de Barcelona. La propuesta de donación de la colección a la ciudad de Barcelona se realizó en noviembre de 2010 y fue aceptada por el Instituto de Cultura de Barcelona (ICUB) en fecha 11 de febrero de 2011. Formada por 4.990 ejemplares y 25 lotes, no es la colección de un investigador en paleontologÃa sino la de un paleontólogo generalista. Muchos ejemplares de esta colección fueron figurados en una guÃa de campo elaborada por Gómez-Alba (1988) sobre los fósiles de España y de Europa. El catálogo es, aparte de algunas correcciones menores, la
transcripción literal de la base de datos originalmente asociada a la colección que –desde su aceptación– no ha sido actualizada ni revisadaWe present the catalogue of the palaeontological collection belonging to the late Dr. Julio Gómez-Alba, former curator of Palaeontology at Barcelona’s Museum of Geology, now integrated in Barcelona’s Natural History Museum Consortium. He proposed the donation of his collection to the city of Barcelona in November 2010 and the Barcelona’s Institute of Culture (ICUB) accepted it on the 11th February 2011. Formed by 4.990 specimens and 25 batches, it is not the collection of a palaeontological researcher but that of a general palaeontologist. Many items in this collection were figured in a field guide authored by Gómez-Alba (1988) dealing with the fossils of Spain and Europe. The catalogue is, apart from some minor corrections, the literal transcription of the database originally associated to the collection that –since its acceptation– has neither been updated nor revised
Macrofauna de invertebrados del Cretácico superior de la Depresión Central Asturiana
Se reporta y comenta la fauna de inocerámidos, rudistas, ammonites, braquiópodos y equmnidos recogida y localizada en yacimientos o series estratigráficas de detalle, durante los trabajos de campo de la tesis doctoral del primero de los autores (E.B.) sobre los seláceos del Cretácico de Asturias. La distribución, principalmente de inocerámidos y ammonites, permite identificar el Cenomaniense superior y el Turoniense inferior y medio. Se han reconocido rudistas del Turoniense superior y del Coniaciense, braquiópodos del Cenomaniense y del Santoniense inferior y un registro relativamente rico y variado de equÃnidos desde el Cenomaniense hasta el Coniaciense.The fauna collected and located on fossil localities or stratigraphical profiles, during the field work of the first author's doctoral thesis on the Cretaceous selachians from Asturias, is reported and commented. It includes inoceramids, rudists, ammonoids, brachiopods and echinoids. Distribution of, mainly inoceramids and ammonoids, allowed to identify the Upper Cenomanian and the Lower and Middle Turonian. LateTuronian and Coniacian rudists have been recognized, as well as Cenomanian and lower Santonian brachiopods and a quite rich and diversified record of echinoids ranging from Cenomanian to Coniacian
Fragmented condensation in Bose–Hubbard trimers with tunable tunnelling
We consider a Bose–Hubbard (BH) trimer, i.e. an ultracold Bose gas populating three quantum states. The latter can be either different sites of a triple-well potential or three internal states of the atoms. The bosons can tunnel between different states with variable tunnelling strength between two of them. This will allow us to study; (i) different geometrical configurations, i.e. from a closed triangle to three aligned wells and (ii) a triangular configuration with a π-phase, i.e. by setting one of the tunnellings negative. By solving the corresponding three-site BH Hamiltonian we obtain the ground state of the system as a function of the trap topology. We characterize the different ground states by means of the coherence and entanglement properties. For small repulsive interactions, fragmented condensates are found for the π-phase case. These are found to be robust against small variations of the tunnelling in the small interaction regime. A low-energy effective many-body Hamiltonian restricted to the degenerate manifold provides a compelling description of the π-phase degeneration and explains the low-energy spectrum as excitations of discrete semifluxon states.Peer Reviewe