1,653,120 research outputs found
Pairing and persistent currents - the role of the far levels
We calculate the orbital magnetic response to Aharonov Bohm flux of
disordered metallic rings with attractive pairing interaction. We consider the
reduced BCS model, and obtain the result as an expansion of its exact solution
to first order in the interaction. We emphasize the connection between the
large magnetic response and the finite occupation of high energy levels in the
many-body ground state of the ring.Comment: 10 pages, contribution to MS+S200
Quantum fluctuations and glassy behavior: The case of a quantum particle in a random potential
In this paper we expand our previous investigation of a quantum particle
subject to the action of a random potential plus a fixed harmonic potential at
a finite temperature T. In the classical limit the system reduces to a
well-known ``toy'' model for an interface in a random medium. It also applies
to a single quantum particle like an an electron subject to random
interactions, where the harmonic potential can be tuned to mimic the effect of
a finite box. Using the variational approximation, or alternatively, the limit
of large spatial dimensions, together with the use the replica method, and are
able to solve the model and obtain its phase diagram in the
plane, where is the particle's mass. The phase diagram is similar to that
of a quantum spin-glass in a transverse field, where the variable
plays the role of the transverse field. The glassy phase is characterized by
replica-symmetry-breaking. The quantum transition at zero temperature is also
discussed.Comment: revised version, 23 pages, revtex, 5 postscript figures in a separate
file figures.u
Nonequilibrium chiral dynamics by the time dependent variational approach with squeezed states
We investigate the inhomogeneous chiral dynamics of the O(4) linear sigma
model in 1+1 dimensions using the time dependent variational approach in the
space spanned by the squeezed states. We compare two cases, with and without
the Gaussian approximation for the Green's functions. We show that mode-mode
correlation plays a decisive role in the out-of-equilibrium quantum dynamics of
domain formation and squeezing of states.Comment: 5 pages, 4 figures. RevTex, version to appear in Phys. Rev. C. Rapid
Communicatio
Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions
[Background] Various cluster states of astrophysical interest are expected to
exist in the excited states of . However, they have not been
identified firmly, because of the experimental and theoretical difficulties.
[Purpose] To establish the Mg+, O+C and
Ne+2 cluster bands, we theoretically search for the
negative-parity cluster bands that are paired with the positive-parity bands to
constitute the inversion doublets. We also offer the isoscalar monopole and
dipole transitions as a promising probe for the clustering. We numerically show
that these transition strengths from the ground state to the cluster states are
very enhanced. [Method] The antisymmetrized molecular dynamics with Gogny D1S
effective interaction is employed to calculate the excited states of . The isoscalar monopole and dipole transition strengths are directly
evaluated from wave functions of the ground and excited states. [Results]
Negative-parity bands having Mg+ and O+C cluster
configurations are obtained in addition to the newly calculated
Ne+2 cluster bands. All of them are paired with the
corresponding positive-parity bands to constitute the inversion doublets with
various cluster configurations. The calculation show that the band-head of the
Mg+ and Ne+2 cluster bands are strongly excited
by the isoscalar monopole and dipole transitions. [Conclusions] The present
calculation suggests the existence of the inversion doublets with the
Mg+, O+C and Ne+2
configurations.Because of the enhanced transition strengths, we offer the
isoscalar monopole and dipole transitions as good probe for the
Mg+ and Ne+2 cluster bands.Comment: 28 pages, 8 figure
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