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Algebras, dialgebras, and polynomial identities
This is a survey of some recent developments in the theory of associative and
nonassociative dialgebras, with an emphasis on polynomial identities and
multilinear operations. We discuss associative, Lie, Jordan, and alternative
algebras, and the corresponding dialgebras; the KP algorithm for converting
identities for algebras into identities for dialgebras; the BSO algorithm for
converting operations in algebras into operations in dialgebras; Lie and Jordan
triple systems, and the corresponding disystems; and a noncommutative version
of Lie triple systems based on the trilinear operation abc-bca. The paper
concludes with a conjecture relating the KP and BSO algorithms, and some
suggestions for further research. Most of the original results are joint work
with Raul Felipe, Luiz A. Peresi, and Juana Sanchez-Ortega.Comment: 32 page
An inner automorphism is only an inner automorphism, but an inner endomorphism can be something strange
The inner automorphisms of a group G can be characterized within the category
of groups without reference to group elements: they are precisely those
automorphisms of G that can be extended, in a functorial manner, to all groups
H given with homomorphisms G --> H. Unlike the group of inner automorphisms of
G itself, the group of such extended systems of automorphisms is always
isomorphic to G. A similar characterization holds for inner automorphisms of an
associative algebra R over a field K; here the group of functorial systems of
automorphisms is isomorphic to the group of units of R modulo units of K.
If one substitutes "endomorphism" for "automorphism" in these considerations,
then in the group case, the only additional example is the trivial
endomorphism; but in the K-algebra case, a construction unfamiliar to ring
theorists, but known to functional analysts, also arises.
Systems of endomorphisms with the same functoriality property are examined in
some other categories; other uses of the phrase "inner endomorphism" in the
literature, some overlapping the one introduced here, are noted; the concept of
an inner {\em derivation} of an associative or Lie algebra is looked at from
the same point of view, and the dual concept of a "co-inner" endomorphism is
briefly examined. Several questions are posed.Comment: 20 pages. To appear, Publicacions Mathem\`{a}tiques. The 1-1-ness
result in the appendix has been greatly strengthened, an "Overview" has been
added at the beginning, and numerous small rewordings have been made
throughou
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