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Mathematica - Fachgruppe Computeralgebra

Mathematica - Fachgruppe Computeralgebra

Mathematica - Fachgruppe Computeralgebra

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Since 1996, numerous formulas of this same type<br />

have been found for various constants [1, 8]. For example,<br />

a similar formula was found that permits arbitrary-<br />

position binary digits of π 2 to be calculated; here is a<br />

formula for π 2 that permits arbitrary ternary (base-3)<br />

digits of π 2 to be calculated:<br />

π2 = 2 ∞ 1<br />

27 k=0 729k <br />

243 405 81 27<br />

−<br />

−<br />

−<br />

(12k + 1) 2 (12k + 2) 2 (12k + 4) 2 (12k + 5) 2<br />

72<br />

9<br />

9<br />

5<br />

1<br />

−<br />

−<br />

−<br />

−<br />

+<br />

(12k + 6) 2 (12k + 7) 2 (12k + 8) 2 (12k + 10) 2 (12k + 11) 2<br />

<br />

.<br />

Sadly, it has recently been proven that there is no formula<br />

of this type for π itself in other than a binary base [8,<br />

Ch. 3].<br />

Identification of Multiple ζ Constants<br />

A large number of results has been found over the last<br />

15 years using PSLQ in the course of research on multiple<br />

zeta sums, such as those shown in Table 1. After<br />

computing the numerical values of these constants, a<br />

PSLQ program was used to determine if a given constant<br />

satisfied an identity of a conjectured form. These<br />

efforts produced numerous empirical evaluations and<br />

suggested general results [2, 9]. Eventually, elegant<br />

∞ k=1<br />

∞ k=1<br />

proofs were found for many of these specific and general<br />

results. Three examples of PSLQ results that were<br />

subsequently proven are given in Table 1. In the table,<br />

ζ(t) =<br />

∞<br />

j −t<br />

j=1<br />

is the Riemann zeta function, and<br />

Lin(x) =<br />

∞<br />

j=1<br />

x j j −n<br />

denotes the polylogarithm function.<br />

<br />

1<br />

1 2 −4 37<br />

1 + 2 + · · · + k (k + 1) = 22680π6 − ζ2 (3)<br />

<br />

1<br />

1 3 −6 3 197 1<br />

1 + 2 + · · · + k (k + 1) = ζ (3) + 24 ζ(9) + 2π2ζ(7) ∞ <br />

1<br />

k=1 1 − 2<br />

+ · · · + (−1)k+1 1<br />

k<br />

Ising integrals<br />

One particularly fruitful application of these methods is<br />

the evaluation of definite integrals, such as those that<br />

arise in mathematical physics. For example, recently the<br />

present authors, together with Richard Crandall, investigated<br />

three classes of n-fold integrals, which arise in<br />

Ising theory and also (in some cases) in quantum field<br />

theory:<br />

Cn := 4<br />

∞<br />

n! 0 · · · ∞<br />

0<br />

− 11<br />

120π4ζ(5) − 37<br />

7560π6ζ(3) 2 −3 (k + 1) = 4 Li5( 1 1<br />

2 ) − 30 ln5 (2) − 17<br />

32ζ(5) − 11<br />

720 π4 ln(2) + 7<br />

4 ζ(3) ln2 (2) + 1<br />

18 π2 ln 3 (2) − 1<br />

8 π2 ζ(3)<br />

Table 1: Some multiple ζ identities found by PSLQ<br />

1<br />

( du1<br />

n<br />

2 u1<br />

j=1 (uj+1/uj))<br />

· · · dun<br />

un ,<br />

10<br />

Dn := 4<br />

∞<br />

n! 0 · · · ∞<br />

0<br />

En = 2 1<br />

0 · · · 1<br />

0<br />

<br />

2 ui−uj i

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