User:Prime.mover/Sandbox

This page exists for me to be able to test out features I am developing.

Template pages: stub, tidy, proofread, questionable, explain

Stolen from User:Arthur/Sandbox, as he does not seem to be around any more, and I want to revive this:

User:Prime.mover/Sandbox/Minimal Negation Operator

$\newcommand{\Re}{\operatorname {Re}\,} \newcommand {\pFq} [5] {{}_{#1} \operatorname{F}_{#2} \left({\genfrac{}{}{0pt}{}{#3}{#4} \bigg|{#5} }\right)}$ We consider, for various values of $s$, the $n$-dimensional integral\begin{align} \label{def:Wns}  W_n (s)  &:=   \int_{[0, 1]^n}     \left| \sum_{k = 1}^n \mathrm{e}^{2 \pi \mathrm{i} \, x_k} \right|^s \mathrm{d}\boldsymbol{x}\end{align}which occurs in the theory of uniform random walk integrals in the plane, where at each step a unit-step is taken in a random direction. As such, the integral \eqref{def:Wns} expresses the $s$-th moment of the distance to the origin after $n$ steps.By experimentation and some sketchy arguments we quickly conjectured and strongly believed that, for $k$ a nonnegative integer\begin{align} \label{eq:W3k}  W_3(k) &= \Re \, \pFq32{\frac12, -\frac k2, -\frac k2}{1, 1}{4}.\end{align}Appropriately defined, \eqref{eq:W3k} also holds for negative odd integers. The reason for \eqref{eq:W3k} was long a mystery, but it will be explained at the end of the paper.



False Statement
It is completely false to say:


 * $\exists y \in G: y^2 = x$


 * the order $\order x$ is odd
 * the order $\order x$ is odd

An order $2$ element in $C_4$ refutes the converse.

This mistake can arise by supposing that this:
 * $\exists y \in G: y^2 = x$

implies:
 * $\exists n \in \N: \paren {x^n}^2 = x$

The second step can only be used if every $x$ can be expressed in the terms of $y^2$.