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Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.

7 votes
5 answers
4k views

What is the functor tensor product?

I'm familiar with the tensor product of modules, but I've also come across functor tensor product (in emily riehls paper on homotopy limits), what are they, and how are they (if they are) related to t …
Mozibur Ullah's user avatar
1 vote
2 answers
192 views

Can a classifying space be characterised universally? [closed]

I'm having trouble understanding what classifying spaces are in general. It seems to me, that they are terminal in a category of bundles whose morphisms are pullback squares, is this correct?
Mozibur Ullah's user avatar
5 votes
1 answer
534 views

is there a universal property that characterises the join of two categories?

Let A & B be two categories, the join A*B is created by stipulating its class of object is the disjoint union of the objects of A & B, the morphisms remain the 'same', but we throw in an extra morphi …
Mozibur Ullah's user avatar
2 votes
1 answer
566 views

Are Verma modules universally characterised?

I'm having trouble understanding the definition of Verma Module in wikipedia. It later goes to show that it satisfies what appears to be a universal property (which I'm also having trouble understandi …
Mozibur Ullah's user avatar
5 votes
2 answers
654 views

What is the analogue for the category of presheafs for complement toposes?

Complement Toposes are dual in a sense to (elementary) Toposes and are expected to have typed higher paraconsistent logic as its internal language (as dual intuitionistic logic is paraconsistent). No …
Mozibur Ullah's user avatar
1 vote
1 answer
212 views

gluing bundles as a 2-colimit

Is the gluing of bundles from not-necessarily trivial bundles just some kind of 2-colimit?
Mozibur Ullah's user avatar
1 vote
Accepted

gluing bundles as a 2-colimit

not my answer, but David Carchedi's answer in a comment: 'What you might be thinking is, the category of principal bundles over a fixed base is a 2-colimit over all covers of the base (or some cofina …
Mozibur Ullah's user avatar
6 votes
3 answers
1k views

Is there a category of topological-like spaces that forms a topos?

The category of convergence spaces generalise topological spaces and form a quasi-topos, as topoi are allegedly nicer is there a nicer kind of topological-like space, the category of which forms a top …
Mozibur Ullah's user avatar
3 votes
0 answers
199 views

Is there a useful Galois connection between Languages and Grammars?

I've just beginning to learn logic and proof theory - and the following rather vague and perhaps ill-formed question occurred to me. Given an alphabet it's straightforward to construct the Language, …
Mozibur Ullah's user avatar
11 votes
2 answers
2k views

Are grothendieck universes enough for the foundations of category theory?

Grothendieck universes are equivalent to ZFC+a strongly inaccessible cardinal. This is low on the large cardinal axiom list. Is it enough to place category theory on a firm foundational basis, and how …
Mozibur Ullah's user avatar
2 votes
1 answer
857 views

Where should one go to learn about triangulated categories?

Lurie's book, higher topos theory describes a new notion of a triangulated category, which is apparently much more natural than the usual definition. Obviously by now a great deal of work has been don …
Mozibur Ullah's user avatar
5 votes
2 answers
516 views

are immersions/submersions captured in generalised smooth spaces by some universal property?

Immersions & sumersions are important in differential manifolds. They rely on their definition of the construction of the tangent bundle. I realise that generalised smooth spaces do not have a canoni …
Mozibur Ullah's user avatar
6 votes
2 answers
603 views

What categories correspond to the typed lambda calculus with parametric types?

the unadorned typed lambda calculus correspond to the closed cartesian categories, but if we add in dependent or parametric types how are they then characterised?
Mozibur Ullah's user avatar
9 votes
1 answer
709 views

Is there a nice characterisation of topoi with nice meta-logical properties?

First-order order classical logic with standard semantics has a proof theory: it is complete, sound and effective. In higher order logic with standard semantics one cannot obtain a proof theory - i …
Mozibur Ullah's user avatar
6 votes

Is Mac Lane still the best place to learn category theory?

I found the Catsters on YouTube divinely useful. John Baez, in his not so weekly blog, inspiring. The n-category cafe, to keep you going. Eugenia Cheng's notes on category theory was tremendously u …

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