Some Remarks on Regular Words

Some Remarks on Regular Words

some remarks on regular subgroups of the affine group

‎let $v$ be a vector space over a field $f$ of characteristic $pgeq 0$ and let‎ ‎$t$ be a regular subgroup of the affine group $agl(v)$‎. ‎in the finite dimensional case we show that‎, ‎if $t$ is abelian or $p>0$‎, ‎then $t$ is unipotent‎. ‎for $t$ abelian‎, ‎pushing forward some ideas used in [a‎. ‎caranti‎, ‎f‎. ‎dalla volta and m‎. ‎sala‎, ‎abelian regular subgroups of the affine group and r...

Remarks on Privileged Words

We discuss the notion of privileged word, recently introduced by Peltomäki. A word w is privileged if it is of length ≤ 1, or has a privileged border that occurs exactly twice in w. We prove the following results: (1) if wk is privileged for some k ≥ 1, then wj is privileged for all j ≥ 0; (2) the language of privileged words is neither regular nor context-free; (3) there is a linear-time algor...

Remarks on Separating Words

The separating words problem asks for the size of the smallest DFA needed to distinguish between two words of length ≤ n (by accepting one and rejecting the other). In this paper we survey what is known and unknown about the problem, consider some variations, and prove several new results.

Remarks on Regular Sequences

In this note we exhibit a condition under which a sequence of elements a19 , an in a commutative noetherian local ring A form an Asequence, and derive a number of corollaries. Recall that if M is an A-module, then a19 , an is an M-sequence if 1) ai+1 is a nonzerodivisor on M/(a19 9a1)M for i = 0, 9n — 1,. and 2) M Φ (al9 . . . , α n ) M . If a19 , an is an A-sequence and / is the ideal generate...