Continued fractions for (ir)rationals

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In summary, the article discusses the computation of gamma to 30,100 decimal places using an algorithm based on an identity involving Bessel functions. Through the computation of regular continued fractions, the authors show that if gamma or exp(gamma) can be expressed as a fraction of integers P and Q, then |Q| must be larger than 10^15000. This result is based on a theorem from an earlier paper by one of the authors, A. Ya. Khinchin, which states that if x = gamma or exp(gamma) can be expressed as a rational fraction, then |Q| must be larger than 10^10000. This theorem is further discussed in Khinchin's book "Continued Fractions
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From http://web.comlab.ox.ac.uk/oucl/work/richard.brent/pub/pub049.html :

"Using one of the algorithms, which is based on an identity involving Bessel functions, gamma has been computed to 30,100 decimal places. By computing their regular continued fractions, we show that, if gamma or exp(gamma) is of the form P/Q for integers P and Q, then [itex]|Q|>10^{15000}[/itex]."

The method of getting to this result is not mentioned in this paper, but an earlier paper by one of its authors says this:

"Let [itex]x=\gamma\textrm{ or }\exp(\gamma)[/itex]. From Theorem 17 of [15], [itex]|Q_nx-P_n|\le|Qx-P|[/itex] for all integers P and Q with [itex]0<|Q|\le Q_n[/itex]. Using [itex]q_1,\ldots,q_{20000}[/itex], we find [itex]Q_{20000}(\gamma)=5.6\ldots\times10^{10328}[/itex] and [itex]Q_{20000}(\exp(\gamma)=3.3\ldots\times10^{10293}[/itex]. Hence, we have the following result, which makes it highly unlikely that [itex]x=\gamma\textrm{ or }\exp(\gamma)[/itex] is rational.
THEOREM. If [itex]x=\gamma\textrm{ or }\exp(\gamma)[/itex] = P/Q for integers P and Q, then [itex]|Q|>10^{10000}[/itex]."

The paper referenced is "A. Ya. KHINTCHINE (A. Ja. HINČIN), Continued Fractions, 3rd ed., (English transl. by P. Wynn), Noordhoff, Groningen, 1963. MR 28 #5038.". The author's name is now usually spelled Khinchin (of Khinchin's Constant fame).I'm trying to find that result (possibly even with a proof) which I take to be a basic result. Can anyone state it or give a common name for it?
 
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That's not a paper, its a book:

A. Ya. Khinchin, Continued Fractions, Dover reprint, 1997

You can purchase it for a five dollars American or something like that. I recommend that you do just that because its a beautiful book. Make sure to look for the wonderful connections with ergodic theory!
 
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The result stated in the paper is known as Khinchin's theorem, which states that for almost all real numbers, their continued fraction expansion has infinitely many partial quotients that are larger than any given constant. This means that if a real number x is rational, then its continued fraction expansion will eventually terminate, but for irrational numbers, the continued fraction expansion will have infinitely many partial quotients. This is a fundamental result in the theory of continued fractions and has important applications in number theory and dynamical systems.
 

Related to Continued fractions for (ir)rationals

1. What are continued fractions for (ir)rationals?

Continued fractions are a method of representing numbers, specifically irrational numbers, as a sequence of fractions. These fractions are added together, and the result approximates the original number. They are useful for providing a more precise representation of irrational numbers compared to decimal expansions.

2. How do you convert an irrational number into a continued fraction?

The process for converting an irrational number into a continued fraction involves repeatedly taking the reciprocal of the fractional part of the number and adding it to the whole number. This process is continued until the fractional part becomes zero, resulting in a sequence of fractions that approximate the original number.

3. What is the advantage of using continued fractions over decimal expansions?

Continued fractions provide a more accurate representation of irrational numbers compared to decimal expansions. They also have a unique representation for each irrational number, while some irrational numbers can have multiple decimal expansions. Additionally, continued fractions are useful for solving certain types of mathematical problems, such as finding the closest rational approximation to a given number.

4. Are there any special properties of continued fractions for irrational numbers?

Yes, continued fractions for irrational numbers have several interesting properties. For example, the convergents of a continued fraction, which are the partial sums of the fraction, provide increasingly accurate approximations of the original number. Additionally, the continued fraction expansion for an irrational number can be used to identify patterns and relationships between different irrational numbers.

5. Can continued fractions be used to find exact values for irrational numbers?

No, continued fractions provide approximations of irrational numbers, but they cannot give exact values. This is because irrational numbers, by definition, cannot be expressed as a finite sequence of numbers and therefore cannot be represented exactly by any numerical method. However, continued fractions can provide increasingly precise approximations as the number of terms in the sequence increases.

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