Boson model, interacting

Iachello, F., and Arima, A. (1987), The Interacting Boson Model, Cambridge University Press. 

Kirson, M. W., and Leviatan, A. (1985), Resolution of Any Interacting-Boson-Model Hamiltonian into Intrinsic and Collective Parts, Phys. Rev. Lett. 55, 2846. 

Schaaser, H., and Brink, D. (1984), Calculations away from SU(3) Symmetry by Cranking the Interacting Boson Model, Phys. Lett. B 143, 269. 

In the interacting boson model-2, low lying collective states of nuclei are described in terms of 12 dynamical bosons [ARI77,0TS78], six proton and six neutron bosons. The six proton and neutron bosons have angular momentum J=0 (s-boson) and J=2 (d-boson). It is convenient to introduce creation (d, s ) (u = 2, 1, 0) and annihilation (du,s) operators. When proton ( tt ) and neutron (v) degrees of freedom are added, the creation and annihilation operators assume an extra label ( tt, v), d s, ... 

One of the most interesting aspects of the Interacting Boson Model concerns its connections with the underlying fermion space. The understanding of the mechanism through which bosonlike features arise from effective nuclear hamiltonians provides, in fact, a way to relate collective spectra to the fermion motion. 

SAMBATARO Microscopic Theory of the Interacting Boson Model... 

The effect of neutron-proton symmetry breaking on the distribution of M1 strength in the SU(3) limit of the Interacting Boson Model (IBA-2) is studied. A possible alternative choice for the Majorana force is investigated, with a structure that resembles more closely that which is calculated in microscopic theories. It is found that the specific choice for the Majorana interaction has important consequences for the magnetic strength distribution function. In addition it allows for an alternative interpretation of the second excited K7T=0+ band in rare earth nuclei, as a mixed-symmetry state. 

Interacting Boson Model-2 for High-Spin States... 

The N-P Interacting Boson Model is extended to include bosons of spins 4, 6, 8,.. in addition to the usual S and D bosons, in order to treat nuclear states of high spin within the IBM formalism. 

The Importance of an Accurate Determination of Interacting Boson Model-2 Parameters... 

First, a brief description of the neutron-proton Interacting Boson Model (IBM-2) is given. Next, this model is applied to experimental data in order to determine its empirical parameters. Finally, we discuss why an accurate determination of these parameters is so important. 

In terms of the three limiting group symmetries used in the interacting boson model (IBM), the shape transition of Ru or Pd nuclei can be explained as a SU(5) to 0(6) transition [STA82]. The transition of Sr or Zr nuclei is characterized instead as SU(5) to SU(3). 

Recent Experimental Investigations and Interacting Boson Model Calculations of Even Te Isotopes... 

Level schemes of Sm-138, Sm-136, Sm-134 and Nd- 132 are given in fig. 4 and the lifetimes of some excited states are summarized in table 1. The excitation energies in these nuclei have been computed on the basis of the interacting boson model, IBM-2 0TS78J. The computations are in good agreement with the experimental results of Sm-136, Sm-134 and Nd-132 but not of Sm-138. The extended IBM-2 which includes the interaction between the bosons and a two-quasiparticle 10+ state can reproduce the experimental situation ... 

In addition to the shell model and geometric collective model, there exists a third basic approach to nuclear structure, the interacting boson model (IBM). A boson is a particle of integer spin. Bosons obey Bose-Einstein statistics, and the wave function of two identical bosons is symmetric under particle exchange. 

The interacting boson model applies group theoretical (or algebraic) methods and describes nuclear states of various collectivity and symmetry in a uniform framework (see reviews by lachello and Arima (1987), lachello and Van Isacker (1991), and Fenyes (2002)). 

The starting point of the interacting boson model is the shell model, but IBM drastically truncates the available configuration space, in order to hold the calculations within reasonable limits. At the same time, the IBM keeps the most important elements substantial for the description of the properties of nuclei. 

The first, simplest version of the interacting boson model, the IBM-1 intends to give a description of positive parity levels of medium-heavy even-even nuclei. The model was later considerably extended and now there are versions which are able to treat also negative parity states, both light and heavy, odd-A and odd-odd nuclei, low-lying states and giant resonances, etc. 

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