I think the reason must be that a pseudomanifold $V$ has singular locus $\Sigma V$ of codimension 2 or greater. (Stratifications of varieties are obtained by letting $X_{k-1}$ be the singular locus of $X_k$, or some refinement of that to get the Whitney conditions.) This codimension condition is ...

Is there a model category $C$ on an additive category such that its homotopy category $Ho(C)$ is the stable homotopy category of spectra and the additive structure on $Ho(C)$ is induced from that on $C$. Basically I want to add and subtract maps in $C$ without going to its homotopy category. ...

Here is a closely related pair of examples from operator theory, von Neumann's inequality and the theory of unitary dilations of contractions on Hilbert space, where things work for 1 or 2 variables but not for 3 or more. In one variable, von Neumann's inequality says that if $T$ is an operator o...

When entering a link via the dialog, we now make sure to encode "nasty" characters, so the resulting link definition is actually usable.