En-ring

In mathematics, an $\mathcal{E}_n$-algebra in a symmetric monoidal infinity category C consists of the following data:

• An object $A(U)$ for any open subset U of Rⁿ homeomorphic to an n-disk.
• A multiplication map:

  $\mu: A(U_1) \otimes \cdots \otimes A(U_m) \to A(V)$

for any disjoint open disks $U_j$ contained in some open disk V

subject to the requirements that the multiplication maps are compatible with composition, and that $\mu$ is an equivalence if $m=1$. An equivalent definition is that A is an algebra in C over the little n-disks operad.

Examples

• An $\mathcal{E}_n$-algebra in vector spaces over a field is a unital associative algebra if n=1, and a unital commutative associative algebra if n≥2.

• An $\mathcal{E}_n$-algebra in categories is a monoidal category if n=1, a braided monoidal category if n=2, and a symmetric monoidal category if n≥3.

• If Λ is a commutative ring, then $X \mapsto C_*(\Omega^n X; \Lambda)$ defines an $\mathcal{E}_n$-algebra in the infinity category of chain complexes of $\Lambda$-modules.

See also

• Categorical ring

References

• http://www.math.harvard.edu/~lurie/282ynotes/LectureXXII-En.pdf
• http://www.math.harvard.edu/~lurie/282ynotes/LectureXXIII-Koszul.pdf

External links

• http://ncatlab.org/nlab/show/En-algebra