Given an irrational number x in R∖Q, is it possible to find a map T:N->N strictly increasing such that {T(n)x}->0 as n->oo, where {⋅} is the fractional part?

Kaylynn Cook

Kaylynn Cook

Answered question

2022-11-20

Given an irrational number x R Q , is it possible to find a map T : N N strictly increasing such that { T ( n ) x } 0 as n , where { } is the fractional part?

Answer & Explanation

Cindy Mercer

Cindy Mercer

Beginner2022-11-21Added 13 answers

If x is irrational, by Kronecker's theorem, for all N there exists some 1 q such that { q x } < 1 N .
If x is irrational then n x is irrational.
Let T ( 1 ) = 1 and suppose we have built n terms of the sequence T ( n ), to build the next pick N large enough that 1 N < { T ( n ) x } and apply Kronecker's theorem on the irrational T ( n ) x to get some q > 1 such that { q T ( n ) x } and put T ( n + 1 ) = T ( n ) q.

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?