5,175 research outputs found
Condition for the Existence of Complex Modes in a Trapped Bose--Einstein Condensate with a Highly Quantized Vortex
We consider a trapped Bose--Einstein condensate (BEC) with a highly quantized
vortex. For the BEC with a doubly, triply or quadruply quantized vortex, the
numerical calculations have shown that the Bogoliubov--de Gennes equations,
which describe the fluctuation of the condensate, have complex eigenvalues. In
this paper, we obtain the analytic expression of the condition for the
existence of complex modes, using the method developed by Rossignoli and
Kowalski [R. Rossignoli and A. M. Kowalski, Phys. Rev. A 72, 032101 (2005)] for
the small coupling constant. To derive it, we make the two-mode approximation.
With the derived analytic formula, we can identify the quantum number of the
complex modes for each winding number of the vortex. Our result is consistent
with those obtained by the numerical calculation in the case that the winding
number is two, three or four. We prove that the complex modes always exist when
the condensate has a highly quantized vortex
Condition for emergence of complex eigenvalues in the Bogoliubov-de Gennes equations
The condition for the appearance of dynamical instability of the
Bose-condensed system, characterized by the emergence of complex eigenvalues in
the Bogoliubov-de Gennes equations, is studied analytically. We perturbatively
expand both the Gross-Pitaevskii and Bogoliubov-de Gennes equations with
respect to the coupling constant. It is concluded that the degeneracy between a
positive-norm eigenmode and a negative-norm one is essential for the emergence
of complex modes. Based on the conclusion, we justify the two-mode
approximation applied in our previous work [E. Fukuyama \textit{et al}., Phys.
Rev. A {\bf 76}, 043608 (2007)], in which we analytically studied the condition
for the existence of complex modes when the condensate has a highly quantized
vortex.Comment: 7page
Phase Diagram of Lattice-Spin System RbCoBr
We study the lattice-spin model of RbCoBr which is proposed by Shirahata
and Nakamura, by mean field approximation. This model is an Ising spin system
on a distorted triangular lattice. There are two kinds of frustrated variables,
that is, the lattice and spin. We obtain a phase diagram of which phase
boundary is drawn continuously in a whole region. Intermediate phases that
include a partial disordered state appear. The model has the first-order phase
transitions in addition to the second-order phase transitions. We find a
three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice
ferrimagnetic state does not appear when the lattice is not distorted.Comment: 5 pages, 4 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn.
Vol.75 (2006) No.
Search for long-lived states in antiprotonic lithium
The spectrum of the (L_i^3 + p-bar + 2e) four-body system was calculated in
an adiabatic approach. The two-electron energies were approximated by a sum of
two single-electron effective charge two-center energies as suggested in [6].
While the structure of the spectrum does not exclude the existence of
long-lived states, their experimental observability is still to be clarified
Possible solution to the Li problem by the long lived stau
Modification of standard big-bang nucleosynthesis is considered in the
minimal supersymmetric standard model to resolve the excessive theoretical
prediction of the abundance of primordial lithium 7. We focus on the stau as a
next-lightest superparticle, which is long lived due to its small mass
difference with the lightest superparticle. It provides a number of additional
decay processes of and . A particularly
important process is the internal conversion in the stau-nucleus bound state,
which destroys the and effectively. We show
that the modification can lead to a prediction consistent with the observed
abundance of .Comment: 6 pages, 5 figure
Synergetic effect of gene-pyramiding on disease progress and uredinial production of asian soybean rust in the field.
Título em português: Efeito sinérgico da piramidização de genes no progresso da doença e na produção uredinial da ferrugem-asiática da soja no campo
Schizophrenic Neutrinos and -less Double Beta Decay
We point out a novel possibility for neutrinos where all neutrino flavors can
be part Dirac and part Majorana. Our primary motivation for this model comes
from an attempt to use supersymmetric see-saw models to tie inflation, baryon
asymmetry of the Universe and dark matter to the neutrino sector. The idea
however could stand on its own, with or without supersymmetry. We present a
realization of this possibility within an family symmetry for neutrino
masses, where we obtain tri-bi-maximal mixing for neutrinos to the leading
order. The model predicts that for the case of inverted hierarchy, the lower
limit on the neutrino mass measured in neutrinoless double beta decay
experiments is about a factor of two larger than the usual case.Comment: 6 pages, 1 figure. Extended discussion on the pseudo-Dirac mass
splitting due to loop correction
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