Difference between revisions of "Pi is transcendental"

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(moved the calculations to the references to make it more readable)
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<math>\int_0^{\infty}\left(\omega+\beta_i\right)^{\rho}\left[f\left(\omega+\beta_i\right)b^M\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\int_0^{\infty}\sum_{k=0}^{\rho}\left(ρk\right)\omega^k\beta_i^{\rho-k}\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\omega^k\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega</math>
<math>\int_0^{\infty}\left(\omega+\beta_i\right)^{\rho}\left[f\left(\omega+\beta_i\right)b^M\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\int_0^{\infty}\sum_{k=0}^{\rho}\left(ρk\right)\omega^k\beta_i^{\rho-k}\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\omega^k\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega</math>


The expression <math>f(\omega+\beta_i)</math> will again be some kind of <math>M</math>-th degree polynomial. But because the polynomial is zero for <math>\omega = 0</math> we know that the last coefficient is also equal to zero.
:The expression <math>f(\omega+\beta_i)</math> will again be some kind of <math>M</math>-th degree polynomial. But because the polynomial is zero for <math>\omega = 0</math> we know that the last coefficient is also equal to zero.


<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\omega^k\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[b(\omega+\beta_i)^M + \text{ . . . }+b_M\right]^{\rho + 1}\omega^k e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[l\omega^M + \text{ . . . }+\omega l_{M-1}\right]^{\rho + 1}\omega^k e^{-\omega}d\omega </math>
<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\omega^k\left[f\left(\omega+\beta_i\right)\right]^{\rho + 1}e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[b(\omega+\beta_i)^M + \text{ . . . }+b_M\right]^{\rho + 1}\omega^k e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[l\omega^M + \text{ . . . }+\omega l_{M-1}\right]^{\rho + 1}\omega^k e^{-\omega}d\omega </math>


So, raised to the <math>\rho+1</math>-th power we get a polynomial again, but with the last <math>\rho</math> coefficients equal to zero.
:So, raised to the <math>\rho+1</math>-th power we get a polynomial again, but with the last <math>\rho</math> coefficients equal to zero.


<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[l\omega^M + \text{ . . . }+\omega l_{M-1}\right]^{\rho + 1}\omega^k e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left(l'\omega^{M\rho+M} + \text{ . . . }+\omega^{\rho+1} l'_{M(\rho+1)-\rho -1}\right)\omega^k e^{-\omega}d\omega </math>
<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left[l\omega^M + \text{ . . . }+\omega l_{M-1}\right]^{\rho + 1}\omega^k e^{-\omega}d\omega = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left(l'\omega^{M\rho+M} + \text{ . . . }+\omega^{\rho+1} l'_{M(\rho+1)-\rho -1}\right)\omega^k e^{-\omega}d\omega </math>


We can "distribute" the integral into the sum
:We can "distribute" the integral into the sum


<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left(l'\omega^{M\rho+M} + \text{ . . . }+\omega^{\rho+1} l'_{M(\rho+1)-\rho -1}\right)\omega^k e^{-\omega}d\omega  = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\int_0^{\infty}\omega^{M\rho+M}\omega^k e^{-\omega}d\omega + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\int_0^{\infty}\omega^{\rho+1}\omega^k e^{-\omega}d\omega\right)</math>
<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\int_0^{\infty}\left(l'\omega^{M\rho+M} + \text{ . . . }+\omega^{\rho+1} l'_{M(\rho+1)-\rho -1}\right)\omega^k e^{-\omega}d\omega  = b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\int_0^{\infty}\omega^{M\rho+M}\omega^k e^{-\omega}d\omega + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\int_0^{\infty}\omega^{\rho+1}\omega^k e^{-\omega}d\omega\right)</math>


As above we can now use the fact that <math>\int_0^{\infty}\omega^{\rho}e^{-\omega}d\omega = \rho!</math> to get rid of the integrals; the expression becomes
:As above we can now use the fact that <math>\int_0^{\infty}\omega^{\rho}e^{-\omega}d\omega = \rho!</math> to get rid of the integrals; the expression becomes


<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\left(M\rho+M+k\right)! + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\left(\rho+1+k\right)!\right) = b^{M\rho+M}\left(\rho+1\right)!\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\frac{\left(M\rho+M+k\right)!}{\left(\rho+1\right)!} + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\frac{\left(\rho+1+k\right)!}{\left(\rho+1\right)!}\right) = \left(\rho+1\right)!\cdot G\left(\beta_i\right)</math>
<math>b^{M\rho+M}\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\left(M\rho+M+k\right)! + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\left(\rho+1+k\right)!\right) = b^{M\rho+M}\left(\rho+1\right)!\sum_{k=0}^{\rho}\left(ρk\right)\beta_i^{\rho-k}\left(l'\frac{\left(M\rho+M+k\right)!}{\left(\rho+1\right)!} + \text{ . . . }+l'_{M(\rho+1)-\rho -1}\frac{\left(\rho+1+k\right)!}{\left(\rho+1\right)!}\right) = \left(\rho+1\right)!\cdot G\left(\beta_i\right)</math>


where <math>G(\beta_i)</math> is a polynomial in <math>\beta_i</math> with integer coefficients.
:where <math>G(\beta_i)</math> is a polynomial in <math>\beta_i</math> with integer coefficients.
</ref>
</ref>
which tells us that the integral is equal to  
which tells us that the integral is equal to  

Revision as of 20:32, 24 January 2022

Pi is transcendental is a famous claim regarding the nature of the number π. It was first proven by Ferdinand von Lindemann in 1882, buildung on methods developed by Charles Hermite, who was able to prove that the number e is transcendental roughly 10 years earlier in 1873. With the help of Karl Weierstrass their findings could be generalized to the Lindemann-Weierstrass theorem in 1885.

Proof

The proof shown here is not the original proof by Lindemann but a later proof by David Hilbert which is a bit more accessible.

Suppose π is algebraic. Set α1=iπ where i is the imaginary unit (i2=1). Then α1 is also algebraic, so it is the root of an n-th degree polynomial with integer coefficients. Let α2, . . . , αn be the other roots of this polynomial.

Since 1+eiπ=0 (Euler's identity) we have (1+eα1)(1+eα2) . . . (1+eαn)=1+eβ1+eβ2+ . . . +eβN=0 for some β1, . . . , βN. These βi are also algebraic, since they are the sums of other algebraic numbers (the αi). Disregarding the βi that are equal to 0, we end up with a+eβ1+eβ2+ . . . +eβM=0 for some positive integer a (since e0=1). Because the β1, . . . , βM are algebraic, they are the roots of a polynomial f(z)=bzM+b1zM1+ . . . +bM1z+bM with integer coefficients bb1, . . . , bM, and because no βi is equal to zero bM0 also.

First Part

First we will multiply our equation with the integral 0zρ[f(z)bM]ρ+1ezdz, where ρ is some positive integer. We will write 0 as a shorthand. This allows us to split the sum into two Parts:

P1=a0+ eβ1β1+ . . . +eβMβM
P2=0+eβ10β1+ . . . +eβM0βM

where 0βi is a line integral along the line segment from 0 to βi in the complex plane, and βi is also a line integral obtained by integrating over the line from βi to parallel to the real axis in the complex plane. [1]

Second Part

The reason to do this is that, surprisingly, this turns most of the equation into integers.

First, one can show that 0=0zρ[f(z)bM]ρ+1ezdz is an integer that is divisible by ρ! by expanding [f(z)bM]ρ+1 to an integer polynomial and then using the fact that 0zσezdz=σ! for positive integers σ. [2]

More specifically, if divided by (ρ+1), one get's the remainder b(Mρ+M)bM(ρ+1)ρ!. [3]

Third Part

Something slightly weaker can be shown for the terms eβiβi=eβiβizρ[f(z)bM]ρ+1ezdz. Using the substitution ω=z+βi we can set the bounds of integration to 0 and , [4] and then perform some similar algebraic manipulations so that we can use 0zσezdz=σ! again, [5] which tells us that the integral is equal to (ρ+1)!G(βi), where G(βi) is a polynomial in βi with integer coefficients.

Fourth Part

...

Claim
Statement of the claim Pi is transcendental
Level of certainty Proven
Nature Theoretical
Counterclaim Pi is algebraic
Dependent on


Dependency of


References

  1. If βi is a real number these integrals are just normal Riemann integrals over the real numbers, and it's easy to see that it's valid to split them up in this way. So let βi be a complex number with imaginary part Im(βi)0. As above, 0βi is the integral along the line segment from 0 to βi, βiR along the line segment parallel to the real axis from βi to a number R with real part Re(R)=R, RR along the line segment parallel to the imaginary axis from R to the real number R, and R0 along the real axis from R to 0. So 0βi+βiR+RR+R0 is an integral along a closed path in the complex plane, which is not self-intersecting if we choose R large enough (R>Re(βi)). Since the function which is being integrated is analytical on the whole complex plane this integral evaluates to zero according to the Cauchy integral theorem. Note that if we let R the lenght of the line segment from R to R stays the same while the function zρ[f(z)bM]ρ+1ez tends towards zero on that line segment. Using the estimation lemma for contour integrals it follows that |RR||RR|max[R;R]zρ[f(z)bM]ρ+1ez0.
    limR(0βi+βiR+RR+R0)=00βi+βi+ 0+0=00βi+βi=0
  2. 0zρ[f(z)bM]ρ+1ezdz=bM(ρ+1)0(bzM+ . . . +bM)ρ+1zρezdz=bM(ρ+1)0(czMρ+M+ . . . +cMρ+M)zρezdz
    =bM(ρ+1)(c0zMρ+M+ρezdz+ . . . +cMρ+M0zρezdz)=bM(ρ+1)(c(Mρ+M+ρ)!+ . . . +cMρ+Mρ!)
    =bMρ+Mρ!(c(Mρ+M+ρ)!ρ!+ . . . +cMρ+M)
    where the ci are integers; if f is a polynomial with integer coefficients so is fρ+1. The fractions are also integers because (ρ+k)!ρ!=(ρ+k)(ρ+k1) . . . 21ρ(ρ1) . . . 21=(ρ+k) . . . (ρ+2)(ρ+1).
  3. Note that in the parentheses above every term is divisible by (ρ+1) except the last one cMρ+M. Hence, modulo (ρ+1) we have the congruence 0bMρ+Mρ!cMρ+M, and since (bzM+ . . . +bM)ρ+1=(czMρ+M+ . . . +cMρ+M)cMρ+M=bMρ+10bMρ+Mρ!bMρ+1 (mod ρ+1).
  4. eβiβizρ[f(z)bM]ρ+1ezdz=eβi0(ω+βi)ρ[f(ω+βi)bM]ρ+1eωβidω=0(ω+βi)ρ[f(ω+βi)bM]ρ+1eωdω
  5. We can expand the first factor using the binomial theorem 0(ω+βi)ρ[f(ω+βi)bM]ρ+1eωdω=bMρ+M0k=0ρ(ρk)ωkβiρk[f(ω+βi)]ρ+1eωdω=bMρ+Mk=0ρ(ρk)βiρk0ωk[f(ω+βi)]ρ+1eωdω
    The expression f(ω+βi) will again be some kind of M-th degree polynomial. But because the polynomial is zero for ω=0 we know that the last coefficient is also equal to zero.
    bMρ+Mk=0ρ(ρk)βiρk0ωk[f(ω+βi)]ρ+1eωdω=bMρ+Mk=0ρ(ρk)βiρk0[b(ω+βi)M+ . . . +bM]ρ+1ωkeωdω=bMρ+Mk=0ρ(ρk)βiρk0[lωM+ . . . +ωlM1]ρ+1ωkeωdω
    So, raised to the ρ+1-th power we get a polynomial again, but with the last ρ coefficients equal to zero.
    bMρ+Mk=0ρ(ρk)βiρk0[lωM+ . . . +ωlM1]ρ+1ωkeωdω=bMρ+Mk=0ρ(ρk)βiρk0(lωMρ+M+ . . . +ωρ+1lM(ρ+1)ρ1)ωkeωdω
    We can "distribute" the integral into the sum
    bMρ+Mk=0ρ(ρk)βiρk0(lωMρ+M+ . . . +ωρ+1lM(ρ+1)ρ1)ωkeωdω=bMρ+Mk=0ρ(ρk)βiρk(l0ωMρ+Mωkeωdω+ . . . +lM(ρ+1)ρ10ωρ+1ωkeωdω)
    As above we can now use the fact that 0ωρeωdω=ρ! to get rid of the integrals; the expression becomes
    bMρ+Mk=0ρ(ρk)βiρk(l(Mρ+M+k)!+ . . . +lM(ρ+1)ρ1(ρ+1+k)!)=bMρ+M(ρ+1)!k=0ρ(ρk)βiρk(l(Mρ+M+k)!(ρ+1)!+ . . . +lM(ρ+1)ρ1(ρ+1+k)!(ρ+1)!)=(ρ+1)!G(βi)
    where G(βi) is a polynomial in βi with integer coefficients.