Antilattices $(S;lor, land)$ for which the Greens equivalences $mathcal L_{(lor)}$, $mathcal R_{(lor)}$, $mathcal L_{(land)}$ and $mathcal R_{(land)}$ are all congruences of the entire antilattice are studied and enumerated.
Let A be an associative algebra over an algebraically closed field F of characteristic zero and let G be a finite abelian group. Regev and Seeman introduced the notion of a regular G-grading on A, namely a grading A= {Sigma}_{g in G} A_g that satisfi
es the following two conditions: (1) for every integer n>=1 and every n-tuple (g_1,g_2,...,g_n) in G^n, there are elements, a_i in A_{g_i}, i=1,...,n, such that a_1*a_2*...*a_n != 0. (2) for every g,h in G and for every a_g in A_g,b_h in A_h, we have a_{g}b_{h}=theta(g,h)b_{h}a_{g}. Then later, Bahturin and Regev conjectured that if the grading on A is regular and minimal, then the order of the group G is an invariant of the algebra. In this article we prove the conjecture by showing that ord(G) coincides with an invariant of A which appears in PI theory, namely exp(A) (the exponent of A). Moreover, we extend the whole theory to (finite) nonabelian groups and show that the above result holds also in that case.
Given a subdirectly irreducible *-regular ring R, we show that R is a homomorphic image of a regular *-subring of an ultraproduct of the (simple) eRe, e in the minimal ideal of R; moreover, R (with unit) is directly finite if all eRe are unit-regular
. Finally, unit-regularity is shown for every member of the variety generated by artinian *-regular rings (endowed with unit and pseudo-inversion).
The goal of this paper is to study the structure of split regular BiHom-Leiniz superalgebras, which is a natural generalization of split regular Hom-Leiniz algebras and split regular BiHom-Lie superalgebras. By developing techniques of connections of
roots for this kind of algebras, we show that such a split regular BiHom-Leiniz superalgebras $mathfrak{L}$ is of the form $mathfrak{L}=U+sum_{a}I_a$ with $U$ a subspace of a maximal abelian subalgebra $H$ and any $I_{a}$, a well described ideal of $mathfrak{L}$, satisfying $[I_a, I_b]= 0$ if $[a] eq [b]$. In the case of $mathfrak{L}$ being of maximal length, the simplicity of $mathfrak{L}$ is also characterized in terms of connections of roots.
The minus partial order is already known for sets of matrices over a field and bounded linear operators on arbitrary Hilbert spaces. Recently, this partial order has been studied on Rickart rings. In this paper, we extend the concept of the minus rel
ation to the module theoretic setting and prove that this relation is a partial order when the module is regular. Moreover, various characterizations of the minus partial order in regular modules are presented and some well-known results are also generalized.