Nonstandard GLh(n) quantum groups and contraction of covariant q-bosonic algebras

GL_h(n) × GL_h(m)-covariant h-bosonic algebras are built by contracting the GL_q(n) × GL_q(m)-covariant q-bosonic algebras considered by the present author some years ago. Their defining relations are written in terms of the corresponding R _h-matrices. Whenever n = 2, and m = 1 or 2, it is proved by using U_h(sl(2)) Clebsch-Gordan coefficients that they can also be expressed in terms of coupled commutators in a way entirely similar to the classical case. Some U_h(sl(2)) rank-(1/2) irreducible tensor operators, recently constructed by Aizawa in terms of standard bosonic operators, are shown to provide a realization of the h-bosonic algebra corresponding to n = 2 and m = 1.     

Cyclisation reactions of bis-protected guanidines

The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I₂/K₂CO₂ leading to novel heterocycles is reported.     

Partial widths of fixed generalized seniority spectral distributions

Analytic expressions are derived for the partial widths of the fixed generalized seniority spectral distributions, using an expansion of the hamiltonian in terms of irreducible tensors with respect to both symplectic and quasi-spin groups.     

FixedJ spectral distributions in large shell model spaces

A method is developed to exactly calculate the fixedJ quasiparticle centroid energies and partial widths. Some results obtained in the even-mass lead isotopes with various interactions are analysed. FixedJ quasiparticle distributions are used to predict an upper limit for the deviations between the quasiparticle approximation and the shell model results for the low-energy levels. The influence of the states with a high quasiparticle number in the low-energy region is seen to strongly depend upon the interaction. The importance of the dimensionalities and the internal widths in explaining the admixtures is stressed.