[en] The example of spl (2,1) illustrates some important properties of the representations of basic superalgebras. Typical representations are most similar to the representations of semisimple Lie algebras. We argue that nontypical representations are a degenerate type of representation. The structure of not fully reducible nontypical representations is discussed in detail. As opposed to semisimple Lie algebras, spl (2,1) also admits representations with nondiagonal Cartan subalgebra. There is a one-to-one correspondence between the representations of spl (2,1) and those of the generalized superalgebra osp(2,0,1,1). The osp(2,0,1,1) counterparts of nontypical irreducible representations of spl(2,1) are unfaithful. (orig.)

[en] The Clebsch-Gordan series and the unmoralized Clebsch-Gordan coefficients for the tensor product of two irreducible representations of spl (2,1) are given. Special emphasis is laid on the discussion of the structure of the series when it contains several nontypical representations. Thereby a better understanding of the 'degenerate' properties of nontypical representations is gained. (orig.)

No abstract available

[en] The ideas around an order parameter that tests the existenceof charged states in gauge theories with matter fields are reviewed. The order parameter is used to show that the phase diagram of the Z₂ Higgs-gauge model in 4 dimensions has a line of second order phase transitions with mean field critical exponents

No abstract available

No abstract available

[en] Charged translation covariant states with finite energy are constructed in the Higgs phase of the Z₂ gauge theory coupled to a Z₂ matter field. (orig.)

[en] Short communication

No abstract available

No abstract available