31. If one varies this with respect to one gets the Adjoint Dirac equation. 32. These equations are useful in reducing proofs about adjoint functors to algebraic manipulations. 33. The idea of an adjoint functor was formulated by Daniel Kan in 1958. 34. This functor is left adjoint to the forgetful functor from groups to sets. 35. Thus, we would like a classification of its self-adjoint extensions. 36. This functor has a left adjoint which is the integral group ring construction. 37. Then the adjoint of is the continuous linear operator satisfying 38. Namely, the adjoint of is defined as an operator with the property: 39. The two variants are related by an adjoint functor. 40. To make the operator self-adjoint a suitable domain must be specified.
