A_infty

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\(A_\infty\) structures

Idea: associativity only up to higher coherent homotopy. Naturally present on the homology complex of any DGA.

attachments/Pasted%20image%2020220424234854.png attachments/Pasted%20image%2020220424234915.png attachments/Pasted%20image%2020220424234958.png

attachments/Pasted%20image%2020220326220951.png

Definitions: attachments/Pasted%20image%2020220326220208.png attachments/Pasted%20image%2020220326220259.png attachments/Pasted%20image%2020220326221114.png Examples:

  • \(H_{\mathrm{dR}}({-})\)

    • \({\operatorname{HH}}({-})\)
  • Any loop space.

attachments/Pasted%20image%2020220326220332.png attachments/Pasted%20image%2020220326220411.png

Coherence

attachments/Pasted%20image%2020220326221646.png # A_infty algebra

attachments/Pasted%20image%2020220207231003.png Here

  • First relation \(m_1^2=0\) makes \(A\) a chain complex
  • Second relation makes multiplication a chain morphism
  • Third relation makes \(m_2\) associative up to chain homotopy
  • Higher relations impose homotopy coherence

See Gerstenhaber bracket, coalgebra, Maurer-Cartan equations. attachments/Pasted%20image%2020220323182816.png

pre-CY structures

Somehow give rise to TQFTs. attachments/Pasted%20image%2020220323183021.png

A_infty categories

attachments/Pasted%20image%2020220326013641.png attachments/Pasted%20image%2020220326013621.png attachments/Pasted%20image%2020220326013559.pngattachments/Pasted%20image%2020220326014230.png

Twisted complexes

attachments/Pasted%20image%2020220326014255.png attachments/Pasted%20image%2020220326014303.png # Bimodules

Related to tilting modulues attachments/Pasted%20image%2020220326220828.png

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