The field theory of free strings is analyzed in gauges in which the two-dimensional metric along the string worldsheet remains as a dynamical variable. Hamiltonian-based BRST methods are used. The cohomology of the complete BRST charge is computed. Equivalence with the usual approach is explicitly established.

A generalization of gauge theory in which the gauge potential1-form is replaced by a p-form is studied. Charged particles are then replaced by elementary extended objects of dimension p−1. It is shown that this extension is compatible with space-time locality only if the gauge group is U(1). A source which is a closed p−1 surface has zero total charge and corresponds to a particle-antiparticle pair. Its quantum rate of production in an external uniform field is evaluated semiclassically. The analog of (...) the Dirac magnetic pole is constructed. It is another extended object, of dimension n−p−3, where n is the dimension of space-time. The “electric” and “magnetic” charges obey the Dirac quantization condition. This condition is derived in two different ways. One method makes use of local gauge patches and the other brings in singular gauge transformations. A topological mass term is introduced and it is shown that it can coexist with a magnetic pole when n=2p+1, provided the topological mass is quantized. (shrink)