Tate K-theory is the elliptic cohomology theory associated with the Tate curve (the Tate elliptic curve over the Laurent series ring $\mathbb{Z}((q))$ ) (AHS 01, 2.7, Lurie 09, 4.3)
The corresponding elliptic genus is the Witten genus (AHS 01, Sec. 2.7).
The underlying cohomology theory is given by Laurent series in topological K-theory, and equivalently by completion of circle group-equivariant K-theory of free loop spaces $\mathcal{L}(-)$ (KM 04, Section 5, see also Lurie 09, Section 5.2):
(For more exposition see also Dove 19, Sec. 6.2).
The equivariant version of Tate K-theory is a form of equivariant elliptic cohomology. For $G$ a finite group and $X$ a topological G-space it comes down (Ganter 07, Def. 3.1, Ganter 13, Def. 2.6, review in Dove 19, Def. 6.16) to the sub-ring
of the direct sum, over conjugacy classes of group elements $g$, of Laurent polynomials with coefficients in equivariant K-theory-groups on the $g$-fixed loci for equivariance group the centralizer of $g$
on those elements which satisfy the rotation condition:
Rotation condition. The $C_g$-equivariant vector bundles $V_j$ which form the coefficient of $q^{j/\left\vert g \right\vert }$ are such that $g$ acts on them by multiplication with $\exp\big( 2 \pi i \frac{j}{\left\vert g \right\vert} \big)$.
This rotation condition may be understood more intrinsically (this is made explicit on p. 63 of Dove 19) as that in implied by the orbifold K-theory on Huan's inertia orbifold (Huan 18), induced by the nature of the quotient groups
appearing there. This quotient exactly equates the action of $g \in G$ with that of a rotation of $S^1$.
Hence, in generalization of twisted ad-equivariant K-theory there is twisted ad-equivariant Tate K-theory (an equivariant elliptic cohomology theory) relating to the Verlinde ring of positive energy loop group representations (Lurie 09, Sec. 5.2, Luecke 19, Cor. 3.2.5, Dove 19).
The Ochanine genus lifts to a homomorphism of ring spectra $M Spin \to KO((q))$ from spin structure cobordism cohomology theory to Tate K-theory (Kreck-Stolz 93, lemma 5.8, lemma 5.4). This is the spin-orientation of elliptic cohomology
As elliptic cohomology over the Tate sphere:
Matthew Ando, Michael Hopkins, Neil Strickland, Section 2.7 of: Elliptic spectra, the Witten genus and the theorem of the cube, Invent. math. 146, 595–687 (2001) (doi:10.1007/s002220100175)
Jacob Lurie, A Survey of Elliptic Cohomology, in: Algebraic Topology Abel Symposia Volume 4, 2009, pp 219-277 (pdf, doi:10.1007/978-3-642-01200-6_9)
As completed $S^1$-equivariant K-theory of free loop space
As a form of equivariant elliptic cohomology (twisted ad-equivariant Tate K-theory):
Nora Ganter, Section 3.1 in: Stringy power operations in Tate K-theory (arXiv:math/0701565)
Nora Ganter, Power operations in orbifold Tate K-theory, Homology Homotopy Appl. Volume 15, Number 1 (2013), 313-342. (arXiv:1301.2754, euclid:hha/1383943680)
Zhen Huan, Quasi-elliptic cohomology, 2017 (hdl:2142/97268)
Zhen Huan, Quasi-elliptic cohomology and its Spectrum (arXiv:1703.06562)
Zhen Huan, Quasi-Elliptic Cohomology I, Advances in Mathematics, Volume 337, 15 October 2018, Pages 107-138 (arXiv:1805.06305, doi:10.1016/j.aim.2018.08.007)
with a streamlined account in
For simply-connected compact Lie groups:
For finite groups:
Last revised on July 9, 2021 at 06:16:02. See the history of this page for a list of all contributions to it.