categories - Category Theory list
 help / color / mirror / Atom feed
From: John Baez <baez@math.ucr.edu>
To: categories@mta.ca
Subject: unital weak functor?
Date: Thu, 20 Sep 2007 09:01:21 -0700	[thread overview]
Message-ID: <E1IYT6d-0006up-Ox@mailserv.mta.ca> (raw)

Josh Nichols-Barrer wrote:

> Hi everyone,
>
> Is there a name for a weak functor between bicategories which takes
> identity 1-morphisms to identity 1-morphisms?  "Unital weak functor"
> would
> seem an apt name, but if there is another with more precedent I'll just
> use that instead.

I don't think there's a standard term.

But, I like the term "normalized", since in certain circumstances weak
functors between
bicategories are described by cocycles in group cohomology, and the
cocycle is then
said to be "normalized" when the weak functor preserves identity
1-morphisms. It's an old
fact that every cocycle is equivalent to a normalized one, and this is
related to the fact
that every weak functor is isomorphic to a normalized one.

For more information on this, see:

Andre Joyal and Ross Street, Braided monoidal categories,
Macquarie Mathematics Report No. 860081, November 1986.
Also available at http://rutherglen.ics.mq.edu.au/~street/JS86.pdf

or for a pedagogical treatment, try section 8.3, "Classifying 2-groups
using
group cohomology", of this:

John Baez and Aaron Lauda, Higher-dimensional algebra V: 2-Groups,
Theory and Applications of Categories 12 (2004), 423-491.
Also available at http://arxiv.org/abs/math.QA/0307200

Best,
jb





             reply	other threads:[~2007-09-20 16:01 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-09-20 16:01 John Baez [this message]
  -- strict thread matches above, loose matches on Subject: below --
2007-09-20 23:23 Joachim Kock
2007-09-20 21:20 John Baez
2007-09-19 21:03 Stephen Lack
2007-09-19 19:30 Robin Houston
2007-09-19  0:58 Josh Nichols-Barrer

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=E1IYT6d-0006up-Ox@mailserv.mta.ca \
    --to=baez@math.ucr.edu \
    --cc=categories@mta.ca \
    /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).