Added a rather unusual reference

- Mattia Coloma, Domenico Fiorenza, Eugenio Landi,
*An exposition of the topological half of the Grothendieck-Hirzebruch-Riemann-Roch theorem in the fancy language of spectra*, (arXiv:1911.12035)

with Latin section titles.

]]>I have added to *orientation in generalized cohomology* a section with the traditional definition (here). It includes statement and proof (here) that traditonally defined universal multiplicative $E$-orientation for vector bundles with $G$-structure is equivalently the class of a ring spectrum homomorphism $M G \longrightarrow E$.

Another discussion of orientation is also in Stong’s notes :)

]]>I finally learned about the general abstract story behind the notion of orientation in $R$-cohomology, for $R$ an $E_\infty$-ring, in terms of trivialization of $GL_1(R)$-associated $\infty$-bundles – from this lecture by Mike Hopkins

I added some remark about that to orientation in generalized cohomology. Needs more polishing and expansion, but I have to interrupt for the moment.

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