182 research outputs found
Exactly solvable models of nuclei
In this paper a review is given of a class of sub-models of both approaches,
characterized by the fact that they can be solved exactly, highlighting in the
process a number of generic results related to both the nature of
pair-correlated systems as well as collective modes of motion in the atomic
nucleus.Comment: 34 pages, 8 figures accepted for publication in Scholarpedi
Criticality in the configuration-mixed interacting boson model : (1) mixing
The case of U(5)-- mixing in the
configuration-mixed Interacting Boson Model is studied in its mean-field
approximation. Phase diagrams with analytical and numerical solutions are
constructed and discussed. Indications for first-order and second-order shape
phase transitions can be obtained from binding energies and from critical
exponents, respectively
Pairing and Isospin Symmetry in Proton-Rich Nuclei
Unlike their lighter counterparts, most odd-odd N=Z nuclei with mass A > 40
40 have ground states with isospin T=1, suggesting an increased role for the
isovector pairing interaction. A simple SO(5) seniority-like model of this
interaction reveals a striking and heretofore unnoticed interplay between
like-particle and neutron-proton isovector pairing near N=Z that is reflected
in the number of each kind of pair as a function of A and T. Large scale
shell-model calculations exhibit the same trends, despite the simultaneous
presence of isoscalar pairs, deformation, and other correlations.Comment: 8 pages + 2 postscript figures, in RevTeX. Discussion of isospin
projection in HFB added. This version to appear in Phys. Lett.
Two-neutron separation energies, binding energies and phase transitions in the interacting boson model
In the framework of the interacting boson model the three transitional
regions (rotational-vibrational, rotational--unstable and,
vibrational--unstable transitions) are reanalyzed. A new kind of plot
is presented for studying phase transitions in finite systems such as atomic
nuclei. The importance of analyzing binding energies and not only energy
spectra and electromagnetic transitions, describing transitional regions is
emphasized. We finally discuss a number of realistic examples.Comment: 34 pages, TeX (ReVTeX). 12 ps figures. 3 tables. Submitted to Nucl.
Phys.
O(12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model
It is shown that the proton-neutron interacting boson model (pnIBM) admits
new symmetry limits with O(12) algebra which break F-spin but preserves the
quantum number M_F. The generators of O(12) are derived and the quantum number
`v' of O(12) for a given boson number N is determined by identifying the
corresponding quasi-spin algebra. The O(12) algebra generates two symmetry
schemes and for both of them, complete classification of the basis states and
typical spectra are given. With the O(12) algebra identified, complete
classification of pnIBM symmetry limits with good M_F is established.Comment: 22 pages, 1 figur
Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons
We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in
136Cs by and conversion-electron detection. For the first time the excitation
energy of the isomer and the multipolarity of its decay have been measured. The
half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer
decays via a very slow 518 keV E3 transition to the ground state. In addition
to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV
E2 transition has been found. Thus we have found a new level at 105 keV with
spin 4+ between the isomeric and the ground state. The results are discussed in
comparison to shell model calculations.Comment: Phys. Rev. C accepted for publicatio
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
SU(3) realization of the rigid asymmetric rotor within the IBM
It is shown that the spectrum of the asymmetric rotor can be realized quantum
mechanically in terms of a system of interacting bosons. This is achieved in
the SU(3) limit of the interacting boson model by considering higher-order
interactions between the bosons. The spectrum corresponds to that of a rigid
asymmetric rotor in the limit of infinite boson number.Comment: 9 pages, 2 figures, LaTeX, epsfi
Nuclear masses set bounds on quantum chaos
It has been suggested that chaotic motion inside the nucleus may
significantly limit the accuracy with which nuclear masses can be calculated.
Using a power spectrum analysis we show that the inclusion of additional
physical contributions in mass calculations, through many-body interactions or
local information, removes the chaotic signal in the discrepancies between
calculated and measured masses. Furthermore, a systematic application of global
mass formulas and of a set of relationships among neighboring nuclei to more
than 2000 nuclear masses allows to set an unambiguous upper bound for the
average errors in calculated masses which turn out to be almost an order of
magnitude smaller than estimated chaotic components.Comment: 4 pages, Accepted for publication in Physical Review Letter
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