It is shown that any singular Lagrangian theory: 1) can be formulated without the use of constraints by introducing a Clairaut-type version of the Hamiltonian formalism; 2) leads to a special kind of nonabelian gauge theory which is similar to the Poisson gauge theory; 3) can be treated as the many-time classical dynamics. A generalization of the Legendre transform to the zero Hessian case is done by using the mixed (envelope/general) solution of the multidimensional Clairaut equation. The corresponding system of motion equations is equivalent to the Lagrange equations and has a linear algebraic subsystem for "unresolved" velocities. Then the equations of motion are written in the Hamilton-like form by introducing new antisymmetric brackets. This is a "shortened" formalism, since it does not contain the "nondynamical" (degenerate) momenta at all, and therefore there is no notion of constraint. It is outlined that any classical degenerate Lagrangian theory (in its Clairaut-type Hamiltonian form) is equivalent to the many-time classical dynamics. Finally, the relation between the presented formalism and the Dirac approach to constrained systems is given.

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A complete list of Uq(sl 2 )-module algebra structures on the quantum plane is produced and the (uncountable family of) isomorphism classes of these structures are described. The composition series of representations in question are computed. The classical limits of the Uq(sl 2 )-module algebra structures are discussed.

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This paper is part of the lecture given at the TH Division of CERN and devoted to the CXXV anniversary of the birthday of Elie Cartan . It is shown how the methods of differential geometry, due to E. Cartan, were applied to the construction of the supersymmetry transformation law and to the actions for Goldstone fermions and supergravity.