Sharp cl1cl_1 distortion conjecture for Heisenberg balls

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Let H\mathbb H be the discrete Heisenberg group, let BnB_n be its radius-nn ball with the word metric dWd_W, and let c1(Bn,dW)c_1(B_n,d_W) denote the least distortion of an embedding of this metric space into ℓ1\ell_1. Sharp ℓ1\ell_1 distortion conjecture for Heisenberg balls. For every integer n⩾2n\geqslant2,

c1(Bn,dW)≍log⁡n.c_1(B_n,d_W)\asymp\sqrt{\log n}.

The conjectural functional and discrete inequalities preceding this statement would imply the lower bound c1(Bn,dW)≳log⁡nc_1(B_n,d_W)\gtrsim\sqrt{\log n}; the matching upper bound is already provided by known embeddings. Thus the conjecture predicts the asymptotically sharp distortion.

References

Primary source

Vincent Lafforgue and Assaf Naor, “Vertical versus horizontal Poincaré inequalities on the Heisenberg group”, arXiv:1212.2107 (2012).

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