In
category theory
Category theory is a general theory of mathematical structures and their relations that was introduced by Samuel Eilenberg and Saunders Mac Lane in the middle of the 20th century in their foundational work on algebraic topology. Nowadays, cate ...
, a branch of mathematics, the formal criteria for adjoint functors are criteria for the existence of a left or right
adjoint of a given
functor.
One criterion is the following, which first appeared in
Peter J. Freyd
Peter John Freyd (; born February 5, 1936) is an American mathematician, a professor at the University of Pennsylvania, known for work in category theory and for founding the False Memory Syndrome Foundation.
Mathematics
Freyd obtained his Ph ...
's 1964 book ''Abelian Categories,
an Introduction to the Theory of Functors'':
Another criterion is:
See also
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Anafunctor
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Adjoint functors