/sci/ - Science & Math

>What are you studying this summer?
I've been reading Johnstone's book on topos theory, Atiyah's book on topological K-theory and Brown's book on cohomology of groups.
>Have you come across any interesting problems, theorems, articles or books lately?
Technically it is none of these, but I must shill for the Mitchell-Bénabou language. You can just take an arbitrary topos, and you can use a language almost that of set theory there!

>>9076534
Just a guess but what if you considered elements of the form [math]a\otimes1[/math], and trying restrict the isomorphism to these?

Do you guys know this site btw? http://yutsumura.com/

If we have n objects, each of which are connected to eachother (except themselves), what is the total number of contacts?

For example, with 4 contacts, the f(4) = 6

What is the correct way to define f(n)