41 research outputs found
Condensed vortex ground states of rotating Bose-Einstein condensate in harmonic atomic trap
We study a system of Bose atoms trapped by a symmetric harmonic
potential, interacting via weak central forces. Considering the ground state of
the rotating system as a function of the two conserved quantities, the total
angular momentum and its collective component, we develop an algebraic approach
to derive exact wave functions and energies of these ground states. We describe
a broad class of the interactions for which these results are valid. This
universality class is defined by simple integral condition on the potential.
Most of the potentials of practical interest which have pronounced repulsive
component belong to this universality class.Comment: 34 pages, 10 ps figures, minor revisions, to be publ. in Ann. Phy
Nuclear Schiff moment and soft vibrational modes
The atomic electric dipole moment (EDM) currently searched by a number of
experimental groups requires that both parity and time-reversal invariance be
violated. According to current theoretical understanding, the EDM is induced by
the nuclear Schiff moment. The enhancement of the Schiff moment by the
combination of static quadrupole and octupole deformation was predicted
earlier. Here we study a further idea of the possible enhancement in the
absence of static deformation but in a nuclear system with soft collective
vibrations of two types. Both analytical approximation and numerical solution
of the simplified problem confirm the presence of the enhancement. We discuss
related aspects of nuclear structure which should be studied beyond mean-field
and random phase approximations.Comment: 14 pages, 4 figure
Shape and structure of N=Z 64Ge; Electromagnetic transition rates from the application of the Recoil Distance Method to knock-out reaction
Transition rate measurements are reported for the first and the second 2+
states in N=Z 64Ge. The experimental results are in excellent agreement with
large-scale Shell Model calculations applying the recently developed GXPF1A
interactions. Theoretical analysis suggests that 64Ge is a collective
gamma-soft anharmonic vibrator. The measurement was done using the Recoil
Distance Method (RDM) and a unique combination of state-of-the-art instruments
at the National Superconducting Cyclotron Laboratory (NSCL). States of interest
were populated via an intermediate-energy single-neutron knock-out reaction.
RDM studies of knock-out and fragmentation reaction products hold the promise
of reaching far from stability and providing lifetime information for excited
states in a wide range of nuclei
Rotating ground states of trapped Bose atoms with arbitrary two-body interactions
In a k-dimensional system of weakly interacting Bose atoms trapped by a
spherically symmetric and harmonic external potential, an exact expression is
obtained for the rotating ground states at a fixed angular momentum. The result
is valid for arbitrary interactions obeying minimal physical requirements.
Depending on the sign of a modified scattering length, it reduces to either a
collective rotation or a condensed vortex state, with no alternative. The
ground state can undergo a kind of quantum phase transition when the shape of
the interaction potential is smoothly varied.Comment: Talk given at the International Conference on Theoretical Physics
(TH2002),Paris, UNESCO, 22-27 July; 11 pages, 3 figures, few typos fixe
Simplified approach to the application of the geometric collective model
The predictions of the geometric collective model (GCM) for different sets of
Hamiltonian parameter values are related by analytic scaling relations. For the
quartic truncated form of the GCM -- which describes harmonic oscillator,
rotor, deformed gamma-soft, and intermediate transitional structures -- these
relations are applied to reduce the effective number of model parameters from
four to two. Analytic estimates of the dependence of the model predictions upon
these parameters are derived. Numerical predictions over the entire parameter
space are compactly summarized in two-dimensional contour plots. The results
considerably simplify the application of the GCM, allowing the parameters
relevant to a given nucleus to be deduced essentially by inspection. A
precomputed mesh of calculations covering this parameter space and an
associated computer code for extracting observable values are made available
through the Electronic Physics Auxiliary Publication Service. For illustration,
the nucleus 102Pd is considered.Comment: RevTeX 4, 15 pages, to be published in Phys. Rev.