Prove that spec of root 2 contains infinitely many powers of 2.

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In summary, the conversation discusses proving that the "spec" of root 2 (defined as {⌊k√2⌋ : k≥0}) contains infinitely many powers of 2. The conversation participants are struggling with finding a proof and are discussing different approaches, such as using the irrationality of sqrt(2) and considering the floor function. They also consider different choices for k in order to show that the spec contains infinitely many powers of 2.
  • #1
sachin123
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Spec of root 2 is that set of elements floor(k * (root 2)) ; k >= 0 .

I have no idea of how I can prove the statement in the question.

Prove that spec of root 2 contains infinitely many powers of 2.
I need ideas on how to proceed.

Thank you
 
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  • #2
sachin123 said:
Spec of root 2 is that set of elements floor(k * (root 2)) ; k >= 0 .

I have no idea of how I can prove the statement in the question.

Prove that spec of root 2 contains infinitely many powers of 2.
I need ideas on how to proceed.

Thank you

What is meant by the "spec" of root 2? I have never seen that term.

RGV
 
  • #3
Here, it means Spec√2= {⌊k√2⌋ : k≥0}
 
  • #5
sachin123 said:
Here, it means Spec√2= {⌊k√2⌋ : k≥0}

It's little tricky. Here's big hint. Pick k=floor(2^n*sqrt(2)). Think about what binary representation of sqrt(2) looks like. Play around with that for a while.
 
  • #6
I've been thinking about it but I can't seem to move ahead.
sqrt(2) is irrational. It's binary representation has no pattern.
It would look like 1.0110101000001001111... and multiplying by 2^n would left-shift it n times.
Taking floor of this irrational number loses a portion of the number. And inside the Spec definition, we have floor (k * √2) and this floor would lose some number too.
Finally if √2 * √2 * 2 ^ n = 2 ^(n+1), this attempt leads to an interger smaller than that.
Where should I be heading?
 
  • #7
Yeah, I'm actually running into the same problem. It's pretty easy to show 2^n*sqrt(2)-floor(2^n*sqrt(2)) is less than 1/2 an infinite number of times and I thought that would cover it, but I keep getting an inequality pointing the wrong way.
 
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  • #8
Dick said:
Yeah, I'm actually running into the same problem. It's pretty easy to show 2^n*sqrt(2)-floor(2^n*sqrt(2)) is less than 1/2 an infinite number of times and I thought that would cover it, but I keep getting an inequality pointing the wrong way.

Ok, I think you can do it. You can either pick 2^n*sqrt(2)-floor(2^n*sqrt(2)) to be in (0,1/2) or (1/2,1) (both happen an infinite number of times). Note it would also work fine if you could show the choice of k=floor(2^n*sqrt(2))+1 works. Just draw some careful diagrams of where all the numbers lie relative to each other.
 
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What is the meaning of "spec of root 2" in this statement?

The "spec of root 2" refers to the set of all numbers that can be obtained by taking powers of 2 and multiplying them by the square root of 2.

How can we prove that this set contains infinitely many powers of 2?

We can prove this by showing that for every natural number n, there exists a power of 2 that is a member of the set. This can be done through mathematical induction, where we show that for n=1, there exists a power of 2 in the set, and then assume that for some arbitrary n=k, there exists a power of 2 in the set, then show that for n=k+1, there also exists a power of 2 in the set.

Is there a specific formula or equation that can be used to prove this statement?

Yes, there is a formula that can be used to prove this statement. It is called the geometric series formula, which states that for a geometric series with starting term a and common ratio r, the sum of n terms is given by a(1-r^n)/(1-r). We can use this formula to show that for every natural number n, there exists a power of 2 in the set.

Can we use other mathematical concepts or techniques to prove this statement?

Yes, there are other mathematical concepts and techniques that can be used to prove this statement. For example, we can use the concept of limit to show that as n approaches infinity, the sum of n terms in the geometric series formula becomes infinitely large, indicating that there are infinitely many powers of 2 in the set.

Why is proving this statement important in the field of mathematics?

Proving this statement is important because it helps us understand the behavior of numbers and their relationships to one another. It also allows us to make connections between different mathematical concepts, such as powers and limits, and helps us build a stronger foundation for future mathematical discoveries and advancements.

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