Ordering statistics of 4 random walkers on the line.

We study the ordering statistics of 4 random walkers on the line, obtaining a much improved estimate for the long-time decay exponent of the probability that a particle leads to time $t$; $P_{\rm lead}(t)\sim t^{-0.91287850}$, and that a particle lags to time $t$ (never assumes the lead); $P_{\rm lag}(t)\sim t^{-0.30763604}$. Exponents of several other ordering statistics for $N=4$ walkers are obtained to 8 digits accuracy as well. The subtle correlations between $n$ walkers that lag {\em jointly}, out of a field of $N$, are discussed: For $N=3$ there are no correlations and $P_{\rm lead}(t)\sim P_{\rm lag}(t)^2$. In contrast, our results rule out the possibility that $P_{\rm lead}(t)\sim P_{\rm lag}(t)^3$ for $N=4$, though the correlations in this borderline case are tiny.