Randomly interacting bosons, mean-fields and L=0 ground states

Random interactions are used to investigate to what extent the low-lying behavior of even-even nuclei depend on particular nucleon-nucleon interactions. The surprising results that were obtained for the interacting boson model, i.e. the dominance of ground states with L=0 and the occurrence of both vibrational and rotational structure, are interpreted and explained in terms of a mean-field analysis.Comment: 6 pages, 2 figures, Invited talk at NP2001, Goettingen, March 2001, World Scientific (2001), in pres

Collective states from random interactions

The anharmonic vibrator and rotor regions in nuclei are investigated in the framework of the interacting boson model using an ensemble of random one- and two-body interactions. Despite the randomness of the interactions (in sign and size) we find a predominance of L(P)=0(+) ground states and strong evidence for the occurrence of both vibrational and rotational band structure.Comment: 4 pages, 2 figures, 1 tables, to be published in the proceedings of Bologna 200

How random are random nuclei? Shapes, triangles and kites

We study the origin of the regular features obtained in numerical studies of the IBM with random interactions, in particular the dominance of L=0 ground states and the occurrence of vibrational and rotational band structures. It is shown that the geometric shapes associated with IBM Hamiltonians play a crucial role in understanding these regular properties. Different regions of the parameter space are associated with definite geometric shapes, such as spherical and deformed shapes and a condensate of quadrupole bosons.Comment: 5 pages, 3 figures, invited talk at `International Conference on Nuclear Structure, May 22-25, Wyoming, US

Scalar Wave Propagation in Random, Amplifying Media: Influence of Localization Effects on Length and Time Scales and Threshold Behavior

We present a detailed discussion of scalar wave propagation and light intensity transport in three dimensional random dielectric media with optical gain. The intrinsic length and time scales of such amplifying systems are studied and comprehensively discussed as well as the threshold characteristics of single- and two-particle propagators. Our semi-analytical theory is based on a self-consistent Cooperon resummation, representing the repeated self-interference, and incorporates as well optical gain and absorption, modeled in a semi-analytical way by a finite imaginary part of the dielectric function. Energy conservation in terms of a generalized Ward identity is taken into account

New correlations induced by nuclear supersymmetry

We show that the nuclear supersymmetry model (n-susy) in its extended version, predicts correlations in the nuclear structure matrix elements which characterize transfer reactions between nuclei that belong to the same supermultiplet. These correlations are related to the fermionic generators of the superalgebra and if verified experimentally can provide a direct test of the model.Comment: Invited talk at "Nuclear Physics: Large and Small", April 19-22, 2004, Hacienda Cocoyoc, Mexic