29 Answers votes newest views recent 2Why does the group act on the right on the principal bundle? 1What is the definition of “canonical” ? 1De Rham theorem for differentiable spaces 5Nice application of generalized smooth spaces 1Advice on Giving a Talk 3A Book You Would Like to Write 4Does this formula have a rigorous meaning, or is it merely formal. 1Dimensions of orbit spaces 3Why do we teach calculus students the derivative as a limit? 1What does the word “symplectic” mean? 12Mathematical “urban legends” 6What is Symplectic Area? 2Why should one still teach Riemann integration? 20A soft introduction to physics for mathematicians who don’t know the first thing about physics 3Which mathematicians have influenced you the most? 1Topology of maps between fibers of vector bundles 4The straightest possible path embeddable in a path of polygons 3How do you keep your research notes organized? 3Theorems that are ‘obvious’ but hard to prove 1Why the name ‘separable’ space? 2need a reference (topological manifolds) 2Is there a good (co)homology theory for manifolds with corners? 5How much of differential geometry can be developed entirely without atlases? 5On referee-author communications 1Orbifold fundamental group in terms of loops? 5What would you want to see at the Museum of Mathematics? 3Formalising the principle of general covariance in differential geometry 4What is meant by smooth orbifold? 2When are two symplectic forms “isotopic”?