Abstract. Let K be any field and L be any lattice. In this note we show that L is a sublattice of annihilators in an associative and commutative K-algebra. If L is finite, then our algebra will be finite dimensional over K.
IntroductionThe problem of representing lattices as lattices of subalgebras or congruences in various abstract algebras is quite often investigated. In some cases it is natural to restrict considerations to finite lattices. We refer the reader to [11,13,12] for some results on this problem. Some papers are devoted to representing lattices as lattices of annihilators in associative rings, for example [8,6], or annihilators in semigroups with zero (see [14,9]).In this paper K is any field. In [5] it is shown that every lattice L is embeddable in a lattice of left annihilators of a K-algebra, denoted there by KxLy. If L is finite then this algebra is finite dimensional over K. If L has at most 3 elements then the algebra KxLy is commutative, but for greater number of elements it is noncommutative. Thus there is a natural question, whether every (finite) lattice is isomorphic to a sublattice of the lattice of annihilators in a commutative (finite dimensional) algebra over K. This question was asked by some participants of conferences, where the results of [5] were presented. We solve this problem here by constructing suitable algebras over K.To make the paper more readable and self-contained, in Section 2 we recall some definitions and facts on algebras and some results from [5]. We use this opportunity to add a new consequence of Theorem 3.2 from that paper.In Section 3, using ideas from [5], we show that for every lattice L there exists a local, commutative K-algebra KxxLyy and a lattice embedding of L into the lattice of annihilators in KxxLyy.The cardinality of any set X we denote by |X|. All lattices considered here have the smallest element ω and the largest element Ω ‰ ω. If P is any partially ordered set (poset), then by P op we denote the set P , with the reverse order.
Lattices of annihilatorsHere, by an algebra over K we mean a vector space A over K together with a bilinear associative multiplication. In other words, for arbitrary elements a, b, c P A and for arbitrary λ P K the following equalities are satisfied:1. apb`cq " ab`ac; 2. pb`cqa " ba`ca; 3. pabqc " apbcq; 4. pλaqb " apλbq " λpabq.All algebras over K considered here, named simply algebras, are with 1 ‰ 0. An algeba A is called commutative if ab " ba for any a, b P A and is finite dimensional if the space A is finite dimensional over K. If A is an algebra, then by JpAq we denote the Jacobson radical of A. All other information about algebras used here one can find for example in [7,3].If X Ď A is a subset of an algebra A then let L A pXq " LpXq be the left annihilator of X in A and let R A pXq " RpXq be the right annihilator of X in A :LpXq " ta P A : aX " 0u and RpXq " ta P A : Xa " 0u.Thus, by associativity of A, every left annihilator is a left ideal, and every right annihilator is a right ideal in A.Let A l pAq be the se...