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From: Ross Street <ross.street@mq.edu.au>
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Subject: Re: Formally adding morphisms
Date: Sat, 16 Nov 2019 01:44:47 +0000
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To: Joseph Collins <joseph.collins@strath.ac.uk>
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Dear Joseph

In 2-categorical terminology, your A_f is the coinserter of the two functor=
s X, Y : 1 --> A.

Ross

On 13 Nov 2019, at 5:04 AM, Joseph Collins <joseph.collins@strath.ac.uk<mai=
lto:joseph.collins@strath.ac.uk>> wrote:

Suppose that we have a category A. If we want to formally add a single morp=
hism, say f:X -> Y, where X,Y are in A, but f is not in A, we can do the fo=
llowing: we look at the discrete category containing only X and Y - let us =
denote that as (X Y) - and the category with two objects and only a single =
morphism between them. Let's call this one (X -> Y).


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