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Jan 4, 2014 at 16:01 comment added Asaf As Gil have asked me to add here, Ratner's proof of the Oppenheim conjecture relies on (the orbit closure theorem which relies on-)the measure-classification theorem for $SO(2,1)$-inv.+ergodic measures on $SL_{3}(\mathbb{R})/SL_{3}(\mathbb{Z})$, a few years ago, Manfred Einsiedler have given a simple proof of the measure classification theorem in such a case (action of a semi-simple group) here - math.ethz.ch/~einsiedl/omgsur.pdf
Dec 21, 2013 at 15:49 comment added Asaf Nevertheless, the argument by Dani and Margulis is a bit more simplified, in the way that enabled Margulis and Lindenstrauss to prove an effective Oppenheim conjecture (the paper got released only in $2013$!, because of building on the famous work of Einsiedler-Margulis-Venkatesh about effective equidistribution of horospheres).
Dec 21, 2013 at 15:47 comment added Asaf with Ratner's theorem, you are almost getting a 3 lines proof (Basically, $SO(2,1)$ is a maximal unipotent subgroup of $SL_{3}$). One might say that it builds on Ratner's MC theorem (where Margulis' proof was by purely topological dynamics in some sense), but still, I think that the people who are doing Homogeneous Dynamics would consider this a simplification, as Ratner's theorems are nowadays standard in that field and in number theory at general.
Dec 20, 2013 at 12:34 history made wiki Post Made Community Wiki by Todd Trimble
Dec 20, 2013 at 12:09 history edited Dietrich Burde CC BY-SA 3.0
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Dec 20, 2013 at 11:48 history edited Dietrich Burde CC BY-SA 3.0
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Dec 20, 2013 at 11:03 history answered Dietrich Burde CC BY-SA 3.0