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4 votes

Quotient-free monoidal categories

Here are some additional thoughts and examples. 1) The argument presented in the OP applies whenever one has a monoidal category $(\mathsf{C},\otimes,1)$ in which the unit object $1$ is a separator a …
Tobias Fritz's user avatar
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8 votes

Are there noncartesian monoidal categories with $A \otimes B = A \times B$?

Note: As pointed out by Peter LeFanu Lumsdaine in the comments, the example constructed in this answer does not work in its current form, since naturality of the associator fails. (This only affects t …
Tobias Fritz's user avatar
  • 6,406
8 votes

The dual of a dual in a rigid tensor category

TL;DR: $X\cong (X^*)^*$ is not necessarily true, and this seems to be a folklore result, mentioned e.g. in these notes by Müger on p.9 (found by Eduardo Pareja Tobes). However, finding explicit exampl …
Tobias Fritz's user avatar
  • 6,406
6 votes
Accepted

Cartesian monoidal star-autonomous categories

[I'm going to assume $S' \cong S$, which holds in every symmetric monoidal $*$-autonomous category. (See e.g. Lemma 5.6 of this paper.) This applies here since cartesianness implies symmetry. Part of …
Tobias Fritz's user avatar
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