In this note we consider the metric Ramsey problem for the normed
spaces
lp\ell_p. Namely, given some
1 £ p £ ¥1\le p \le \infty and
a ³ 1\alpha \ge 1, and an integer
nn, we ask for the largest
mm
such that every
nn-point metric space contains an
mm-point
subspace which embeds into
lp\ell_p with distortion at most
a
\alpha. In [1] it is shown that in the case of
l2\ell_2,
the dependence of
mm on
a\alpha undergoes a phase transition at
a = 2\alpha =2. Here we consider this problem for other
lp\ell_p, and
specifically the occurrence of a phase transition for
p ¹ 2p\neq 2.
It is shown that a phase transition does occur at
a = 2\alpha=2 for every
p Î [1,2]p\in
[1,2]. For
$p > 2$p > 2 we are unable to determine the answer, but
estimates are provided for the possible location of such a phase
transition. We also study the analogous problem for isometric
embedding and show that for every
$1 < p < \infty$1 < p < \infty there are
arbitrarily large metric spaces, no four points of which embed
isometrically in
lp\ell_p.