Abstract of a paper by Assaf Naor and Yuval Peres
This is an announcement for the paper "Embeddings of discrete groups and the speed of random walks" by Assaf Naor and Yuval Peres. Abstract: For a finitely generated group G and a banach space X let \alpha^*_X(G) (respectively \alpha^#_X(G)) be the supremum over all \alpha\ge 0 such that there exists a Lipschitz mapping (respectively an equivariant mapping) f:G\to X and c>0 such that for all x,y\in G we have \|f(x)-f(y)\|\ge c\cdot d_G(x,y)^\alpha. In particular, the Hilbert compression exponent (respectively the equivariant Hilbert compression exponent) of G is \alpha^*(G)=\alpha^*_{L_2}(G) (respectively \alpha^#(G)= \alpha_{L_2}^#(G)). We show that if X has modulus of smoothness of power type p, then \alpha^#_X(G)\le \frac{1}{p\beta^*(G)}. Here \beta^*(G) is the largest \beta\ge 0 for which there exists a set of generators S of G and c>0 such that for all t\in \N we have \E\big[d_G(W_t,e)\big]\ge ct^\beta, where \{W_t\}_{t=0}^\infty is the canonical simple random walk on the Cayley graph of G determined by S, starting at the identity element. This result is sharp when X=L_p, generalizes a theorem of Guentner and Kaminker and answers a question posed by Tessera. We also show that if \alpha^*(G)\ge 1/2 then \alpha^*(G\bwr \Z)\ge \frac{2\alpha^*(G)}{2\alpha^*(G)+1}. This improves the previous bound due to Stalder and ValetteWe deduce that if we write \Z_{(1)}= \Z and \Z_{(k+1)}\coloneqq \Z_{(k)}\bwr \Z then \alpha^*(\Z_{(k)})=\frac{1}{2-2^{1-k}}, and use this result to answer a question posed by Tessera in on the relation between the Hilbert compression exponent and the isoperimetric profile of the balls in G. We also show that the cyclic lamplighter groups C_2\bwr C_n embed into L_1 with uniformly bounded distortion, answering a question posed by Lee, Naor and Peres. Finally, we use these results to show that edge Markov type need not imply Enflo type. Archive classification: math.MG math.FA math.GR Remarks: 23 pages The source file(s), , is(are) stored in gzipped form as with size . The corresponding postcript file has gzipped size . Submitted from: naor@cims.nyu.edu The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/0708.0853 or http://arXiv.org/abs/0708.0853 or by email in unzipped form by transmitting an empty message with subject line uget 0708.0853 or in gzipped form by using subject line get 0708.0853 to: math@arXiv.org.
participants (1)
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Dale Alspach