1,345 research outputs found
39-K Bose-Einstein condensate with tunable interactions
We produce a Bose-Einstein condensate of 39-K atoms. Condensation of this
species with naturally small and negative scattering length is achieved by a
combination of sympathetic cooling with 87-Rb and direct evaporation,
exploiting the magnetic tuning of both inter- and intra-species interactions at
Feshbach resonances. We explore tunability of the self-interactions by studying
the expansion and the stability of the condensate. We find that a 39-K
condensate is interesting for future experiments requiring a weakly interacting
Bose gas.Comment: 5 page
Tetrad gravity, electroweak geometry and conformal symmetry
A partly original description of gauge fields and electroweak geometry is
proposed. A discussion of the breaking of conformal symmetry and the nature of
the dilaton in the proposed setting indicates that such questions cannot be
definitely answered in the context of electroweak geometry.Comment: 21 pages - accepted by International Journal of Geometric Methods in
Modern Physics - v2: some minor changes, mostly corrections of misprint
Thermodynamics of the Massive Gross-Neveu Model
We study the thermodynamics of massive Gross-Neveu models with explicitly
broken discrete or continuous chiral symmetries for finite temperature and
fermion densities. The large limit is discussed bearing attention to the
no-go theorems for symmetry breaking in two dimensions which apply to the
massless cases. The main purpose of the study is to serve as analytical
orientation for the more complex problem of chiral transition in
dimensional QCD with quarks. For any non-vanishing fermion mass we find, at
finite densities, lines of first order phase transitions. For small mass values
traces of would-be second order transitions and a tricritical point are
recognizable. We study the thermodynamics of these models, and in the model
with broken continuous chiral symmetry we examine the properties of the pion
like state.Comment: 34 pages (+18 figures, available upon request to [email protected]),
LATEX file, uses art12a.sty, macro included, UGVA-DPT 1994/06-85
Feshbach resonances in ultracold K(39)
We discover several magnetic Feshbach resonances in collisions of ultracold
K(39) atoms, by studying atom losses and molecule formation. Accurate
determination of the magnetic-field resonance locations allows us to optimize a
quantum collision model for potassium isotopes. We employ the model to predict
the magnetic-field dependence of scattering lengths and of near-threshold
molecular levels. Our findings will be useful to plan future experiments on
ultracold potassium atoms and molecules.Comment: 7 pages, 6 figure
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