Abstract:
A sequence of integers is called a T-sequence if there exists a Hausdorff group topology on the integers such that the sequence converges to 0. Given a finite set $S$ of primes, we construct some Hausdorff group topology on the integers such that every increasing sequence with terms divisible only by primes from $S$ converges to 0. Also we answer in the affirmative the question on T-sequences which was posed by Protasov and Zelenuk. Our results rely on a nontrivial number-theoretic fact about $S$-unit equations.