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Jun 13, 2017 at 23:31 vote accept Jonathan Beardsley
Jun 13, 2017 at 23:19 answer added Omar Antolín-Camarena timeline score: 5
Apr 23, 2015 at 14:50 comment added Lennart Meier @JonBeardsley I would bet indeed my money on $U$ being lax monoidal. $M\otimes_B N$ should be the coequalizer of the two arrows $M\otimes B \otimes N \to M\otimes N$ and likewise for $M\otimes_A N$. The map $A\to B$ should induce then a map $M\otimes_A N \to M\otimes_B N$. (If you want you can work with bimodules and strictly associative symmetric spectra to check that; then one does not have to say $\infty$ so often).
Apr 23, 2015 at 12:53 comment added Sean Tilson There is Fausk-Hu-May which addresses this type of situation. It may be worth looking at to see what you could expect.
Apr 22, 2015 at 21:50 comment added Jonathan Beardsley Fair point. So perhaps we should only ask $U$ to be lax monoidal?
Apr 22, 2015 at 21:14 history edited Jonathan Beardsley CC BY-SA 3.0
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Apr 22, 2015 at 21:05 comment added Qiaochu Yuan I'm confused. Suppose we work with just rings instead of ring spectra, so let $A, B$ be two commutative rings and let $f : A \to B$ be a morphism between them. Then $F$ is monoidal, but $U$ isn't. It's easiest to see this when $f$ is a field extension; $F$ preserves dimensions but $U$ multiplies them by the dimension of the extension.
Apr 22, 2015 at 20:46 history edited Jonathan Beardsley CC BY-SA 3.0
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Apr 22, 2015 at 19:38 history asked Jonathan Beardsley CC BY-SA 3.0