Types of quantum field thories
FQFT and cohomology
In a sigma-model quantum field theory a field configuration is a morphism for an -dimensional manifold or similar. One is to think of this as being the trajectory of an -brane propagating in the target space .
For the case (for instance the relativistic particle, a 0-brane) the term worldline for has a long tradition. Accordingly one calls the worldvolume of the given -brane when . For the case (the case of relevance in string theory) one also says worldsheet.