most recent 30 from http://mathoverflow.net 2013-06-19T14:08:24Z http://mathoverflow.net/feeds/user/11438 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/59115/a-set-for-which-it-is-hard-to-determine-whether-or-not-it-is-countable/59344#59344 P C 2011-03-23T19:21:29Z 2011-03-23T19:21:29Z

<p>Maximal set of mutually disjoint $Y$'s in the plane (a $Y$ is the image by a continuous injection of the usual $Y$ made of $3$ segments).</p>

http://mathoverflow.net/questions/48771/proofs-that-require-fundamentally-new-ways-of-thinking/48801#48801 P C 2010-12-09T18:39:30Z 2010-12-09T18:45:47Z

<p>Use of Lagrange theorem (group theory) to prove Fermat's small theorem?</p> <p>Use of fixed point methods (and completeness) to prove existence of solutions to differential equations?</p> <p>Use of Fields theory to prove the impossibility of the trisection of the angle?</p> <p>Use of group theory to prove insolvability of 5th degree equation?</p>