On the polynomial identities of the algebra M11(E)M_{11}(E)

Verbally prime algebras are important in PI theory. They were described by Kemer over a field $K$ of characteristic zero: 0 and $K$ (the trivial ones), $M_n(K)$, $M_n(E)$, $M_{ab}(E)$. Here $K$ is the free associative algebra of infinite rank, with free generators $T$, $E$ denotes the infinite dimensional Grassmann algebra over $K$, $M_n(K)$ and $M_n(E)$ are the $n\times n$ matrices over $K$ and over $E$, respectively. The algebras $M_{ab}(E)$ are subalgebras of $M_{a+b}(E)$, see their definition below. The generic (also called relatively free) algebras of these algebras have been studied extensively. Procesi described the generic algebra of $M_n(K)$ and lots of its properties. Models for the generic algebras of $M_n(E)$ and $M_{ab}(E)$ are also known but their structure remains quite unclear. In this paper we study the generic algebra of $M_{11}(E)$ in two generators, over a field of characteristic 0. In an earlier paper we proved that its centre is a direct sum of the field and a nilpotent ideal (of the generic algebra), and we gave a detailed description of this centre. Those results were obtained assuming the base field infinite and of characteristic different from 2. In this paper we study the polynomial identities satisfied by this generic algebra. We exhibit a basis of its polynomial identities. It turns out that this algebra is PI equivalent to a 5-dimensional algebra of certain upper triangular matrices. The identities of the latter algebra have been studied; these were described by Gordienko. As an application of our results we describe the subvarieties of the variety of unitary algebras generated by the generic algebra in two generators of $M_{11}(E)$. Also we describe the polynomial identities in two variables of the algebra $M_{11}(E)$.Comment: 21 page

PolynomiaI Identities in T-prime AIgebras

We survey results concerning the polynornial identities satisfied by "important" algebras. We discuss classical and new facts about the polynomial identities satisfied by the matrix algebra of order two, by the Grassmann (or exterior) algebra, and by its tensor square

A Basis for the Graded Identities of the Pair (M2(K), gl2(K))

2010 Mathematics Subject Classification: 16R10, 17B01.Let M2(K) be the algebra of 2×2 matrices over an infinite integral domain K. In this note we describe a basis for the Z2-graded identities of the pair (M2(K),gl2(K)).∗ Partially supported by CNPq (Grant 304003/2011-5) and FAPESP (Grant 2010/50347-9). ∗∗ Partially supported by CNPq, DPP/UnB and by CNPq-FAPDF PRONEX grant 2009/00091-0 (193.000.580/2009)

The centre of generic algebras of small PI algebras

Verbally prime algebras are important in PI theory. They are well known over a field $K$ of characteristic zero: 0 and $K$ (the trivial ones), $M_n(K)$, $M_n(E)$, $M_{ab}(E)$. Here $K$ is the free associative algebra with free generators $T$, $E$ is the infinite dimensional Grassmann algebra over $K$, $M_n(K)$ and $M_n(E)$ are the $n\times n$ matrices over $K$ and over $E$, respectively. Moreover $M_{ab}(E)$ are certain subalgebras of $M_{a+b}(E)$, defined below. The generic algebras of these algebras have been studied extensively. Procesi gave a very tight description of the generic algebra of $M_n(K)$. The situation is rather unclear for the remaining nontrivial verbally prime algebras. In this paper we study the centre of the generic algebra of $M_{11}(E)$ in two generators. We prove that this centre is a direct sum of the field and a nilpotent ideal (of the generic algebra). We describe the centre of this algebra. As a corollary we obtain that this centre contains nonscalar elements thus we answer a question posed by Berele.Comment: 15 pages. Misprints corrected. Provisionally accepted to publication in Journal of Algebr

Gradings and Graded Identities for the Matrix Algebra of Order Two in Characteristic 2

2010 Mathematics Subject Classification: 16R10, 16R99, 16W50.Let K be an infinite field and let M2(K) be the matrix algebra of order two over K. The polynomial identities of M2(K) are known whenever the characteristic of K is different from 2. The algebra M2(K) admits a natural grading by the cyclic group of order 2; the graded identities for this grading are known as well. But M2(K) admits other gradings that depend on the field and on its characteristic. Here we describe the graded identities for all nontrivial gradings by the cyclic group of order 2 when the characteristic of K equals 2. It turns out that there is only one grading to consider. This grading is not elementary. On the other hand the graded identities are the same as for the elementary grading.∗ Partially supported by grants from CNPq (No. 304003/2011-5), and from FAPESP (No. 2010/50347-9)