
handle: 10447/40088
The group algebra \(FG\) of a group \(G\) over a field \(F\) is naturally endowed with an involution *, i.e., the \(F\)-linear extension of the involution on \(G\) given by \(g\mapsto g^{-1}\). The latter is called the classical involution and has received substantial interest. Of course, there are obvious more general involutions of \(FG\), namely the \(F\)-linear extensions obtained from arbitrary involutions on \(G\). Recently, there has been a surge of activity on the study of these more general involutions, see for example [\textit{O. Broche Cristo, E. Jespers, C. Polcino Milies, M. Ruiz Marín}, J. Algebra Appl. 8, No. 1, 115-127 (2009; Zbl 1192.16023)] and [\textit{E. Jespers, M. Ruiz Marín}, Commun. Algebra 34, No. 2, 727-736 (2006; Zbl 1100.16021)]. A lot of interest is given to the following topic. Let * be an involution on a ring \(R\). Let \(R^+=\{r\in R\mid r^*=r\}\), the symmetric elements of \(R\), and \(R^-=\{r\in R\mid r^*=-r\}\), the skew symmetric elements of \(R\). An important question is: what properties of \(R^+\) or \(R^-\) can be lifted to \(R\)? (see for example [\textit{I. N. Herstein}, Rings with involution. Chicago Lectures in Mathematics. Chicago - London: The University of Chicago Press (1976; Zbl 0343.16011)]). The group of units of \(R\) is denoted by \(U(R)\), the symmetric units by \(U^+(R)\). In this paper, in case \(F\) is an infinite field of \(\text{char}(F)=p\geq 0\), \(p\neq 2\) and * is an involution on a torsion group \(G\), a complete characterization is given when the *-symmetric units of \(FG\) satisfy a group identity. The main result consists of the following two parts. (1) If \(FG\) is semiprime then \(U^+(FG)\) satisfies a group identity if and only if \(G\) is Abelian or \(G\) is an SLC-group, i.e., \(G\) modulo the center is the Klein Four group. (2) If \(FG\) is not semiprime then \(U^+(FG)\) satisfies a group identity if and only if \(P\), the set of \(p\)-elements of \(G\), is a subgroup, \(FG\) satisfies a polynomial identity and one of the following holds: (i) \(G/P\) is Abelian and \(G'\) is of bounded \(p\)-power exponent; (ii) \(G/P\) is SLC and \(G\) contains a normal *-invariant \(p\)-subgroup \(B\) of bounded exponent such that \(P/B\) is central in \(G/B\) and * is trivial on \(P/B\).
Involution, Units, groups of units (associative rings and algebras), Algebra and Number Theory, Group rings, group algebras, group identities, Group rings of infinite groups and their modules (group-theoretic aspects), Other kinds of identities (generalized polynomial, rational, involution), group identity, involution, Symmetric unit, involutions, Rings with involution; Lie, Jordan and other nonassociative structures, Group algebra, Group identity, symmetric units
Involution, Units, groups of units (associative rings and algebras), Algebra and Number Theory, Group rings, group algebras, group identities, Group rings of infinite groups and their modules (group-theoretic aspects), Other kinds of identities (generalized polynomial, rational, involution), group identity, involution, Symmetric unit, involutions, Rings with involution; Lie, Jordan and other nonassociative structures, Group algebra, Group identity, symmetric units
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