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Let K⩾1 be a parameter. A K-approximate group is a finite set A in a (local) group which contains the identity, is symmetric, and such that A⋅A is covered by K left translates of A.
The main result of this paper is a qualitative description of approximate groups as being essentially finite-by-nilpotent, answering a conjecture of H. Helfgott and E. Lindenstrauss. This may be viewed as a generalisation of the Freiman-Ruzsa theorem on sets of small doubling in the integers to arbitrary groups.
We begin by establishing a correspondence principle between approximate groups and locally compact (local) groups that allows us to recover many results recently established in a fundamental paper of Hrushovski. In particular we establish that approximate groups can be approximately modeled by Lie groups.
To prove our main theorem we apply some additional arguments essentially due to Gleason. These arose in the solution of Hilbert’s fifth problem in the 1950s.
Applications of our main theorem include a finitary refinement of Gromov’s theorem, as well as a generalized Margulis lemma conjectured by Gromov and a result on the virtual nilpotence of the fundamental group of Ricci almost nonnegatively curved manifolds.
Breuillard, Emmanuel 1 ; Green, Ben 2 ; Tao, Terence 3
@article{PMIHES_2012__116__115_0,
author = {Breuillard, Emmanuel and Green, Ben and Tao, Terence},
title = {The structure of approximate groups},
journal = {Publications Math\'ematiques de l'IH\'ES},
pages = {115--221},
publisher = {Springer-Verlag},
volume = {116},
year = {2012},
doi = {10.1007/s10240-012-0043-9},
mrnumber = {3090256},
zbl = {1260.20062},
language = {en},
url = {http://geodesic.mathdoc.fr/articles/10.1007/s10240-012-0043-9/}
}
TY - JOUR AU - Breuillard, Emmanuel AU - Green, Ben AU - Tao, Terence TI - The structure of approximate groups JO - Publications Mathématiques de l'IHÉS PY - 2012 SP - 115 EP - 221 VL - 116 PB - Springer-Verlag UR - http://geodesic.mathdoc.fr/articles/10.1007/s10240-012-0043-9/ DO - 10.1007/s10240-012-0043-9 LA - en ID - PMIHES_2012__116__115_0 ER -
%0 Journal Article %A Breuillard, Emmanuel %A Green, Ben %A Tao, Terence %T The structure of approximate groups %J Publications Mathématiques de l'IHÉS %D 2012 %P 115-221 %V 116 %I Springer-Verlag %U http://geodesic.mathdoc.fr/articles/10.1007/s10240-012-0043-9/ %R 10.1007/s10240-012-0043-9 %G en %F PMIHES_2012__116__115_0
Breuillard, Emmanuel; Green, Ben; Tao, Terence. The structure of approximate groups. Publications Mathématiques de l'IHÉS, Tome 116 (2012), pp. 115-221. doi: 10.1007/s10240-012-0043-9
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