22 research outputs found
Probing additional dimensions in the universe with neutron experiments
We carry out a simple analysis of (n+3)-dimensional gravity in the context of
recent work on 'large' supplementary dimensions and deduce a formula for the
expected compactification radius for the n additional dimensions in the
universe, as a function of the Planck and the electro-weak scales. We argue
that the correspondingly modified gravitational force gives rise to effects
that might be within the detection range of dedicated neutron experiments. A
scattering analysis of the corresponding modified gravitational forces suggests
that slow neutron scattering off atomic nuclei with null spin may provide an
experimental test for these ideas.Comment: A revised version suggesting a specific neutron-scattering
experiment. Physics Letters B, accepted for publicatio
Isovector multiphonon excitations in near spherical nuclei
The lowest isoscalar and isovector quadrupole and octupole excitations in
near spherical nuclei are studied within the the proton-neutron version of the
interacting boson model including quadrupole and octupole bosons (sdf-IBM-2).
The main decay modes of these states in near spherical nuclei are discussed.Comment: 4 pages, 1 figure, LaTeX, sprocl, epsfig. Proc. Int. Conf. on
Structure of the Nucleus at the Dawn of the Century (Bologna, 29 May - 3 June
2000); in pres
Anharmonic double-γ vibrations in nuclei and their description in the interacting boson model
Double-γ vibrations in deformed nuclei are studied in the context of the interacting boson model with special reference to their anharmonic character. It is shown that large anharmonicities can be obtained with interactions that are (at least) of three-body nature between the bosons. As an example the γ vibrations of the nucleus 16668Er98 are studied in detail.DGICYT PB98-111
A Hartree-Bose mean-field approximation for IBM-3
A Hartree-Bose mean-field approximation for the IBM-3 is presented. A Hartree-Bose transformation from the spherical to the deformed bosons with charge-dependent parameters is proposed which allows bosonic pair correlations and includes higher angular momentum bosons. The formalism contains previously proposed IBM-2 and IBM-3 intrinsic states as particular limits.Dirección General de Investigación Científica y Técnica PB 95/0123, PB95-0533European Commission CI1*-CT94-007
Hartree-Bose mean-field approximation for the interacting boson model (IBM-3)
A Hartree-Bose mean-field approximation for the IBM-3 is presented. A Hartree-Bose transformation from spherical to deformed bosons with charge-dependent parameters is proposed which allows bosonic pair correlations and includes higher angular momentum bosons. The formalism contains previously proposed IBM-2 and IBM-3 intrinsic states as particular limits.DGICYT PB95/0123 PB95–0533Comisión Europea CI1*-CT94-007
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
Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near spherical nuclei
The interrelation between the octupole phonon and the low-lying
proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei is
investigated. The one-phonon states decay by collective E3 and E2 transitions
to the ground state and by relatively strong E1 and M1 transitions to the
isoscalar 2+ state. We apply the proton-neutron version of the Interacting
Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin
symmetric dynamical symmetry limits of the model, namely the vibrational and
the \gamma-unstable ones, are considered. We derive analytical formulae for
excitation energies as well as B(E1), B(M1), B(E2) and B(E3) values for a
number of transitions between low-lying states.Comment: 25 pages, 3 figures, LaTeX, epsfig. Nucl. Phys. A (in press
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
First observation of scissors mode states in an odd-mass nucleus
Nuclear resonance fluorescence experiments are reported to search for enhanced M1 scissors mode states in the deformed odd-mass nucleus Dy163. A concentration of dipole strengths near 3 MeV excitation energy is found, which fits nicely into the systematics observed for M1 excitations in the neighboring even-even Dy isotopes. The observed strength distribution and the decay branching ratios are discussed in the context of the interacting boson-fermion model.Dirección General de Investigación Científica y Técnica PB89-063
James Philip Elliott. 27 July 1929—21 October 2008
International audience James Philip Elliott made important contributions to improve our understanding of the structure of atomic nuclei in the second half of the twentieth century. In 1958 he proposed the SU(3) model, explaining rotational behaviour of nuclei in the context of the shell model. His idea, based on elegant and seminal group-theoretical concepts, reconciled the independent-particle with the liquid-drop model, which until then existed as disconnected views of the nucleus. In the 1960s and 1970s he developed methods to extract properties of the nuclear interaction from the phase shifts of nucleon–nucleon scattering. From 1980 until his death he contributed to the development of the interacting boson model of Arima and Iachello, and its microscopic understanding in terms of symmetries of the shell model. For his outstanding achievements in theoretical physics, in 2002 he and Francesco Iachello were awarded the Lise Meitner prize of the European Physical Society for ‘their innovative applications of group-theoretical methods to the understanding of atomic nuclei’. His achievements were also recognized by the award of the Rutherford Medal and Prize of the Institute of Physics in 1994.</jats:p