Narrow Results

We investigate an operator ordering problem in two-dimensional N = 1 supersymmetric model which consists of n real superfields. There arises an operator ordering problem when the target space is curved. We have to fix the ordering in quantum operator properly to obtain the correct supersymmetry algebra. We demonstrate that the super-Poincaré algebra fixes the correct operator ordering. We obtain a supercurrent with correct operator ordering and a central extension of supersymmetry algebra.

The extended commutation relations for generalized uncertainty principle (GUP) have been based on the assumption of the minimal length in position. Instead of this assumption, we start with a constrained Hamiltonian system described by the conventional Poisson algebra and then impose appropriate second class constraints to this system. Consequently, we can show that the consistent Dirac brackets for this system are nothing, but the extended commutation relations describing the GUP.

The Jackiw–Rajaraman version of the chiral Schwinger model is studied as a function of the renormalization parameter. The constraints are obtained and they are used to carry out canonical quantization of the model by means of Dirac brackets. By introducing an additional scalar field, it is shown that the model can be made gauge invariant. The gauge invariant model is quantized by establishing a pair of gauge fixing constraints in order that the method of Dirac can be used.

In this paper, we investigate the classical and quantum aspects of five-dimensional Chern–Simons theory. As a constrained Hamiltonian system we compute the Dirac brackets among the canonical variables for the Abelian case. In terms of the Batalin–Vilkovisky formalism, we show that the classical master equation leads to new algebraic constraints on the Lie algebra. Finally, partition function and geometric quantization of the theory have been also discussed.

We develop in a consistent manner the Ostrogradski–Hamilton framework for gonihedric string theory. The local action describing this model, being invariant under reparametrizations, depends on the modulus of the mean extrinsic curvature of the worldsheet swept out by the string, and thus we are confronted with a genuine second-order in derivatives field theory. In our geometric approach, we consider the embedding functions as the field variables and, even though the highly nonlinear dependence of the action on these variables, we are able to complete the classical analysis of the emerging constraints for which, after implementing a Dirac bracket, we are able to identify both the gauge transformations and the proper physical degrees of freedom of the model. The Ostrogradski–Hamilton framework is thus considerable robust as one may recover in a straightforward and consistent manner some existing results reported in the literature. Further, in consequence of our geometrical treatment, we are able to unambiguously recover as a by-product the Hamiltonian approach for a particular relativistic point-particle limit associated with the gonihedric string action, that is, a model linearly depending on the first Frenet–Serret curvature.

We develop an analog model for the Landau problem and its ensuing noncanonical brackets but in a relativistic context. The chosen model is the Minkowski spacetime in a rotating coordinate system where the motion turns out to be quite similar to the motion in a constant magnetic field. For high angular velocity the Hamiltonian analysis reveals a problem with constraints of second class. In this case the Dirac bracket between spatial coordinates is nonvanishing and inversely proportional to the angular velocity. Finally, the issue of apparent causality violation due to spatial noncommutativity is briefly discussed.