Spectrum and Dynamics of the BCS-BEC crossover from a few-body perspective

The spectrum of two spin-up and two spin-down fermions in a trap is calculated using a correlated gaussian basis throughout the range of the BCS-BEC crossover. These accurate calculations provide a few-body solution to the crossover problem. This solution is used to study the time-evolution of the system as the scattering length is changed, mimicking experiments with Fermi gases near Fano-Feshbach resonances. The structure of avoiding crossings in the spectrum allow us to understand the dynamics of the system as a sequence of Landau-Zener transitions. Finally, we propose a ramping scheme to study atom-molecule coherence.Comment: 4 pages, final version to appear in PR

Ciencia y elocuencia: La palabra de Bernardo Houssay en el discurso médico argentino (1920-1935)

Desde distintos géneros discursivos académicos (conferencias, artículos, lecciones inaugurales de cátedra) Bernardo Houssay (1887-1971), célebre fisiólogo argentino, se ha interesado por la reflexión sobre ciertos tópicos: la ciencia, la medicina, la Universidad, el estudiante y el médico-investigador. En estos enunciados puede vislumbrarse una representación discursiva particular de los médicos-investigadores latinoamericanos (sobre todo, argentinos), caracterizados por un verbalismo excesivo y una oratoria brillante aunque carente de rigurosidad científica. Con inquietud, Houssay advierte cómo estos rasgos son percibidos con aceptación y admiración. Este trabajo se propone confrontar esta imagen de médico con el ethos de Houssay, tal como se construye en su discursividad médico-académica del período 1920-1935. Estos discursos exponen ciertos tipos de enunciados que los estructuran de manera consistente y recurrente: 1) definiciones, 2) enumeraciones, y 3) prescripciones. Su reiteración a lo largo de la serie da cuenta de una imagen de orden, precisión y mesura que se opone a la representación del científico argentino que Houssay critica. El trabajo se inscribe en el marco teórico del Análisis del Discurso desde sus tendencias francesas (Amossy 2000, 2007; Maingueneau 2002, 2008, 2009).In different discursive academic genres (conferences, papers, lessons), Bernardo Houssay (1887-1971), the noted Argentinean physiologist, has shown his interest in reflecting on topics such as science, medicine, Universities, students, and research medical doctors. In these reflections a particular discursive representation about Latin American research doctors (specially, Argentine ones) is displayed, which is characterized by excessive verbalism and a brilliant oratory, but a lack of scientific accuracy. With certain unrest, Houssay warns his audience about how these characteristics are perceived with approval and admiration. This paper intends to confront that image of a doctor with Houssay’s ethos as constructed in his medical-academic speeches produced between 1920 and 1935. These discourses expose certain types of statements that consistently and recurrently work as discourse organizers: 1) definitions, 2) enumerations and 3) prescriptions. Their repetition throughout the series creates an image of order, precision and balance, which is the exact opposite of the representation of the Argentine scientist that Houssay criticizes. The paper draws from the theoretical framework of Discourse Analysis, particularly from its French tendencies (Amossy 2000, 2007; Maingueneau 2002, 2008, 2009).Fil: Von Stecher, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Lingüística; Argentin

Lattice Induced Resonances in One Dimensional Bosonic Systems

We study the resonant effects produced when a Feshbach dimer crosses a scattering continuum band of atoms in an optical lattice. We numerically obtain the exact spectrum of two particles in a one-dimensional lattice and develop an effective atom-dimer Hamiltonian that accurately captures resonant effects. The lattice-induced resonances lead to the formation of bound states simultaneously above and below the scattering continuum and significantly modify the curvature of the dimer dispersion relation. The nature of the atom-dimer coupling depends strongly on the parity of the dimer state leading to a novel coupling in the case of negative parity dimers. From the exact solutions we extract the dimer Wannier function from which we quantitatively determine the effective Hamiltonian parameters for a many-body description.Comment: 4 pages, 3 figures, published versio