Idempotent 2x2 matrices over linearly ordered abelian groups

Document Type : Research Paper

Authors

Institute of Mathematics and Statistics, University of Tartu, Tartu, Estonia

Abstract

In this paper we study multiplicative semigroups of $2\times 2$ matrices over a linearly ordered abelian group with an externally added bottom element. The multiplication of such a semigroup is defined by replacing addition and multiplication by join and addition in the usual formula defining matrix multiplication. We show that there are four types of idempotents in this semigroup and we determine which of them are $0$-primitive.
We also prove that the poset of idempotents with respect to the natural order is a lattice. It turns out that this matrix semigroup is inverse or orthodox if and only if the abelian group is trivial.

Keywords

Main Subjects


[1] Clifford, A.H. and Preston, G.B., “The Algebraic Theory of Semigroups”, Vol. I, American Mathematical Society, 1961.
[2] Das, M., Gupta, M.S., and Sardar, S.K., Morita equivalence of semirings with local units, Algebra Discrete Math. 31(1) (2021), 37-60.
[3] Fuchs, L., “Partially Ordered Algebraic Systems”, Pergamon Press, 1963.
[4] Gould, V., Johnson, M., and Naz, M., Matrix semigroups over semirings, Internat. J. Algebra Comput. 30(2) (2020), 267-337.
[5] Il’in, S.N., A regularity criterion for complete matrix semirings, Mat. Zametki 70(3) (2001), 366-374.
[6] Johnson, M. and Kambites, M., Multiplicative structure of 2 × 2 tropical matrices, Linear Algebra Appl. 435(7) (2011), 1612-1625.
[7] Weinert, H.J. and Wiegandt, R., On the structure of semifields and lattice-ordered groups, Period. Math. Hungar. 32(1-2) (1996), 129-147.