From: jim stasheff <jds@math.upenn.edu>
To: Peter May <may@math.uchicago.edu>
Cc: categories@mta.ca
Subject: Re: Isomorphisms of categories
Date: Sun, 30 May 2010 13:50:56 -0400 [thread overview]
Message-ID: <E1OJEHa-0006z9-NT@mailserv.mta.ca> (raw)
In-Reply-To: <E1OIjQ0-0006Gq-0G@mailserv.mta.ca>
Peter May wrote:
> DeTeXing an exercise I routinely assign, here is
> an example of an isomorphism of categories that is
> not `accidental' in Peter Johnstone's sense and is
> always used in practice as an isomorphism and not
> merely an equivalence.
>
>
> The fundamental theorem of Galois theory:
>
> Let G = Gal(E/F) be the Galois group of a finite
> Galois extension E/F. Define an isomorphism of
> categories between the category of intermediate
> fields F\subset K\subset E and field maps
> K >--> L that fix F pointwise and the category
> of orbits G/H and G-maps between them.
>
>
>
and an isomorphic category of coverings spaces such that...
jim
[For admin and other information see: http://www.mta.ca/~cat-dist/ ]
next prev parent reply other threads:[~2010-05-30 17:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-29 17:31 Peter May
2010-05-30 15:52 ` Toby Bartels
2010-05-30 17:50 ` jim stasheff [this message]
[not found] ` <4C02A580.2000606@math.upenn.edu>
2010-05-30 17:55 ` Peter May
2010-06-01 0:27 ` David Roberts
2010-06-01 8:56 ` covering spaces and groupoids Ronnie Brown
2010-06-01 19:44 ` Eduardo J. Dubuc
[not found] ` <4C04CB41.9080705@btinternet.com>
2010-06-01 12:53 ` Peter May
[not found] ` <4C0502DB.5030603@math.uchicago.edu>
2010-06-02 7:03 ` Ronnie Brown
2010-06-02 13:41 ` Peter May
[not found] ` <BAY127-W27B937A70F21FD2BD806D2C6D10@phx.gbl>
2010-06-08 21:18 ` Ronnie Brown
2010-06-03 18:14 ` F. William Lawvere
2010-06-04 4:12 ` Joyal, André
[not found] ` <B3C24EA955FF0C4EA14658997CD3E25E370F586B@CAHIER.gst.uqam.ca>
2010-06-04 9:37 ` Ronnie Brown
[not found] ` <4C08C956.5080808@btinternet.com>
2010-06-04 11:53 ` jim stasheff
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E1OJEHa-0006z9-NT@mailserv.mta.ca \
--to=jds@math.upenn.edu \
--cc=categories@mta.ca \
--cc=may@math.uchicago.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).