It has long been suspected that strings play a role in understanding the low energy limit of non-abelian gauge theories and in particular in describing hadrons as bound states of quarks and gluons. This idea has recently been made precise by the AdS/CFT correspondence which provides a concrete example of the relation between gauge and string theories.
After reviewing these ideas I am going to concentrate in two aspects of the correspondence:
– First, in the way in which, for certain theories, quarks can be incorporated and their bound states can be computed.
– Second, in a procedure that allows to derive an effective action for a string directly from the field theory. Here, the ferromagnetic (spin 1/2) Heisenberg chain plays a central role: on one hand it arises naturally in the field theory and on the other, it can be seen that its low energy excitations (spin waves) can be interpreted as strings. It therefore provides a bridge between both descriptions.

Brandeis University