6
$\begingroup$

It's well-known that complex cobordism $MU^\ast$ is universal among complex-oriented associative, graded-commutative cohomology theories $E$. This means that if $E$ is a multiplicative cohomology cohomolgoy theory whose coefficients from an associative (unital) graded-commutative ring, then $E$ receives a map of multiplicative cohomology theories from $MU$, uniquely if we ask for compatibility with the complex orientation.

I'm curious what happens if we relax the commutativity assumption on the multiplication on $E$. I'm willing to strengthen the other hypotheses:

Question: Let $E$ be an $E_1$ ring spectrum which is complex oriented (i.e. the unit map $S^0 \to E$ extends to $\Sigma^{\infty-2} \mathbb C \mathbb P^\infty \to E$). Then does $E$ receive a map of some kind from $MU$? Can we at least deduce that $E \otimes MU \neq 0$ if $E \neq 0$?

(At least if we just want $E \otimes MU \neq 0$, the question about $E_1$ rings is equvialent to the same question about weak rings (= half-unital, not-necessarily-associative ring spectra) since we can upgrade the latter to the former via the stable version of the James construction.)

$\endgroup$
2
  • $\begingroup$ If E is any ring spectrum, complex oriented or not, then the Devinatz--Hopkins--Smith nilpotence theorem says that 1 is nilpotent in pi_0(E) if and only 1 is nilpotent in MU_0(E). $\endgroup$ Commented Dec 4, 2023 at 4:10
  • $\begingroup$ @JeremyHahn Ah sure. I guess I didn't say, but I was hoping for an elementary argument, along the lines of how one usually shows this in the commutative case with the Atiyah-Hirzebruch spectral sequence. Does one really need the nilpotence theorem to show this? $\endgroup$ Commented Dec 4, 2023 at 5:32

1 Answer 1

5
$\begingroup$

The initial example of such an $E$ is the Thom spectrum $M\xi$ associated to the $E_1$-map $\Omega \Sigma BU(1) \to BU$, studied by Baker and Richter in "Quasisymmetric functions from a topological point of view" and "Some properties of the Thom spectrum over loop suspension of complex projective space". The $p$-localization $M\xi_{(p)}$ is a wedge sum of suspensions of $BP$, and receives an essential map from $MU$, cf. Proposition 7.1 in the former paper. There is no map of ring spectra from $MU$ to $M\xi$, cf. Remark 4.2 in the latter paper.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .