Difference between revisions of "Essai Latex"

 
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We consider, for various values of $s$, the $n$-dimensional integral
+
We consider, for various values of <math>s</math>, the <math>n</math>-dimensional integral
 +
 
 
\begin{align}
 
\begin{align}
  \label{def:Wns}
 
 
   W_n (s)
 
   W_n (s)
 
   &:=  
 
   &:=  
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     \left| \sum_{k = 1}^n \mathrm{e}^{2 \pi \mathrm{i} \, x_k} \right|^s \mathrm{d}\boldsymbol{x}
 
     \left| \sum_{k = 1}^n \mathrm{e}^{2 \pi \mathrm{i} \, x_k} \right|^s \mathrm{d}\boldsymbol{x}
 
\end{align}
 
\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.
 
  
  

Latest revision as of 14:42, 3 April 2016

\(E=mc^2\)


We consider, for various values of \(s\), the \(n\)-dimensional integral

\begin{align} 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}


\(\begin{align} \nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\ \nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\ \nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\ \nabla \cdot \vec{\mathbf{B}} & = 0 \end{align}\)