Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session J5: Exploring Symmetries in Nuclear Structure |
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Sponsoring Units: DNP Chair: Richard Casten, Yale University Room: Thurgood Marshall West |
Sunday, February 14, 2010 1:30PM - 2:06PM |
J5.00001: Algebraic methods for the nuclear geometric description Invited Speaker: The geometric description of nuclear collective structure, consisting of the Bohr Hamiltonian and its generalizations, is based on the assumption that the dynamics of nuclear quadrupole excitations can be formulated in terms of collective deformation coordinates. The qualitative ideas arising from the approach ({\it e.g.}, $\beta$ and $\gamma$ vibrations) have been foundational to the interpretation of nuclear collective structure. An efficient and tractable scheme for numerical diagonalization of the geometric Hamiltonian, based on $\mathrm{SU}(1,1)\otimes\mathrm{SO}(5)$ algebraic methods, has recently been developed, allowing quantitative application to the full range of nuclear quadrupole rotational-vibrational structure, from spherical oscillator to axial rotor to triaxial rotor, without the need for approximations. In this talk, the algebraic approach will be described, and results and implications will be explored. Supported by the US DOE under grant DE-FG02-95ER-40934. [Preview Abstract] |
Sunday, February 14, 2010 2:06PM - 2:42PM |
J5.00002: Discovery of a quasi-dynamical symmetry along the arc of regularity Invited Speaker: Exact or approximate (quasi-dynamical) symmetries in the framework of the Interacting Boson Approximation model have been identified over the years only at the vertices or along the sides of its symmetry triangle. The first example of an empirically manifested quasi-dynamical symmetry in the interior of the symmetry triangle of the IBA has been recently identified in the limit of large boson numbers. A line, along which spectra exhibit nearly exact SU(3) degeneracies, is found, extending from the SU(3) vertex to near the critical line of the first order phase transition. The SU(3) degeneracies deteriorate with decreasing boson number, but the location of the line remains almost invariant, lying close the Alhassid--Whelan arc of regularity, the unique interior region of regular behavior connecting the SU(3) and U(5) vertices, thus offering a symmetry- based interpretation of that narrow zone of regularity amidst nearby regions corresponding to more chaotic spectra. [Preview Abstract] |
Sunday, February 14, 2010 2:42PM - 3:18PM |
J5.00003: Indication of Unusual Structure in Very Neutron Rich Nuclei Near $^{62}$Ti Invited Speaker: The first step in the study of the properties of nuclei is the discovery. New techniques are being developed and new accelerators are being built to produce new neutron-rich and proton-rich isotopes. The experiments are performed at the limit of detectability. For example the observation of three events of $^{40}$Mg required a total of $\sim $10$^{17} \quad ^{48}$Ca beam particles. The discovery of light neutron-rich new isotopes upto Z $\sim $ 14 determines the location of the neutron dripline. The discovery of $^{42}$Al as the lightest A = 3Z+3 nucleus came as a surprise. In the heavier mass region the mere observation of new isotopes is not surprising because the location of the neutron dripline is currently out of reach. However, already from the production cross sections of these new isotopes it is possible to extract nuclear structure information. The observation of an enhanced production cross section of isotopes near $^{62}$Ti may be evidence for a new island of inversion. [Preview Abstract] |
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