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Jul
31
answered Why is arc length not a differential form?
Jul
31
comment Why is arc length not a differential form?
A differential form is not merely a thing to be integrated!
Jul
30
asked Acyclic Hurewicz fibrations
Jul
30
answered Gluing sheaves - can we realize $\mathcal{F}(W)$ as some kind of limit?
Jul
30
answered Under what choice assumptions is there a monoid structure on every set?
Jul
29
answered Does “cheap nonstandard analysis” take place in a topos?
Jul
29
comment Does “cheap nonstandard analysis” take place in a topos?
@QiaochuYuan It smells like the filter-quotient construction (which is covered in Sheaves in geometry and logic), but I don't immediately see the precise details. I'll come back to this later today...
Jul
29
answered A category where maps are factorizations - what is this called?
Jul
27
comment Definition of sheaf using equalizer
There are textual descriptions above and below the indicated diagram at the cited Wikipedia article. Have you read those?
Jul
26
answered domain of initial $f : X \rightarrow Y$ in Haus equipped with coarsest topology?
Jul
24
revised Facts about the tensor product
deleted 128 characters in body
Jul
24
answered Facts about the tensor product
Jul
24
revised Are lax kernel pairs stable under change of base?
edited tags
Jul
23
comment Is there a suitable definition in categories for a closed continuous function in topology?
The closed subsets are precisely the regular monomorphisms... in the category of Hausdorff spaces. $\mathbf{Top}$ is too large to have any convenient properties as an abstract category.
Jul
22
comment Question about Algebraic Spaces
possible duplicate of Confused with local effectiveness of etale equivalence relations
Jul
20
awarded  Enlightened
Jul
20
awarded  Nice Answer
Jul
19
answered Definition of ordinals in Grothendieck toposes
Jul
17
comment Is it possible to pass functions into other functions in maths?
I would say that this idea was considered in mathematics long before the first digital computers were ever built...
Jul
17
awarded  Deputy