165,185 research outputs found
Quantum phase transition in an atomic Bose gas near a Feshbach resonance
We study the quantum phase transition in an atomic Bose gas near a Feshbach
resonance in terms of the renormalization group. This quantum phase transition
is characterized by an Ising order parameter. We show that in the low
temperature regime where the quantum fluctuations dominate the low-energy
physics this phase transition is of first order because of the coupling between
the Ising order parameter and the Goldstone mode existing in the bosonic
superfluid. However, when the thermal fluctuations become important, the phase
transition turns into the second order one, which belongs to the
three-dimensional Ising universality class. We also calculate the damping rate
of the collective mode in the phase with only a molecular Bose-Einstein
condensate near the second-order transition line, which can serve as an
experimental signature of the second-order transition.Comment: 8 pages, 2 figures, published version in Phys. Rev.
New critical behavior in unconventional ferromagnetic superconductors
New critical behavior in unconventional superconductors and superfluids is
established and described by the Wilson-Fisher renormalization-group method.
For certain ordering symmetries a new type of fluctuation-driven first order
phase transitions at finite and zero temperature are predicted. The results can
be applied to a wide class of ferromagnetic superconducting and superfluid
systems, in particular, to itinerant ferromagnets as UGe2 and URhGe.Comment: 12 pages, 6 fig
Gaussian limits for generalized spacings
Nearest neighbor cells in , are used to define
coefficients of divergence (-divergences) between continuous multivariate
samples. For large sample sizes, such distances are shown to be asymptotically
normal with a variance depending on the underlying point density. In ,
this extends classical central limit theory for sum functions of spacings. The
general results yield central limit theorems for logarithmic -spacings,
information gain, log-likelihood ratios and the number of pairs of sample
points within a fixed distance of each other.Comment: Published in at http://dx.doi.org/10.1214/08-AAP537 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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