ScalingStacks

8.1.7. Actions for the line

We consider the unoriented curve 𝐑{\mathbf{R}}. Let M={±(1−1n)}n∈𝐙>0M=\{\pm(1-\frac{1}{n})\}_{n\in{\mathbf{Z}}_{>0}}.

Consider S,TS,T two finite subsets of 𝐑{\mathbf{R}} with |S|=|T|=n|S|=|T|=n. Let fS:S→∼{1,…,n}f_{S}:S\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}\{1,\ldots,n\} and fT:T→∼{1,…,n}f_{T}:T\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}\{1,\ldots,n\} be the unique increasing bijections. We define

ϕ⁡(S,T):Hom𝒮∙​(𝐑)⁡(S,T)→∼Hn∙=End𝒰∙⁡(en),θ↦TfT∘χ⁡(θ)∘fS−1.\phi(S,T):\operatorname{Hom}\nolimits_{{\mathcal{S}}^{\bullet}({\mathbf{R}})}(S,T)\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}H_{n}^{\bullet}=\operatorname{End}\nolimits_{{\mathcal{U}}^{\bullet}}(e^{n}),\ \theta\mapsto T_{f_{T}\circ\chi(\theta)\circ f_{S}^{-1}}.

We define a functor Φ:𝒮M∙​(𝐑)→𝒰∙\Phi:{\mathcal{S}}^{\bullet}_{M}({\mathbf{R}})\to{\mathcal{U}}^{\bullet}. We put Φ⁡(S)=e|S|\Phi(S)=e^{|S|} and Φ​(f)=ϕ​(S,T)​(f)\Phi(f)=\phi(S,T)(f) for f∈Hom𝒮∙​(𝐑)⁡(S,T)f\in\operatorname{Hom}\nolimits_{{\mathcal{S}}^{\bullet}({\mathbf{R}})}(S,T).

The next proposition follows from Proposition 7.4.33.

0PCS

Proposition 8.1.19. The functor Φ:𝒮M∙​(𝐑)→𝒰∙\Phi:{\mathcal{S}}^{\bullet}_{M}({\mathbf{R}})\to{\mathcal{U}}^{\bullet} is an equivalence of differential pointed categories.

Consider ξ+:𝐑>0→𝐑\xi_{+}:{\mathbf{R}}_{>0}\to{\mathbf{R}} and ξ−:𝐑<0→𝐑\xi_{-}:{\mathbf{R}}_{<0}\to{\mathbf{R}} the inclusion maps.

We define φ±:Lξ±​(−,−,en)→∼L±​(−,−,en)∘(Φ∧Φ)\varphi_{\pm}:L_{\xi_{\pm}}(-,-,e^{n})\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}L^{\pm}(-,-,e^{n})\circ(\Phi\wedge\Phi) by

φ±​(T,S)=ϕ⁡(S,T⊔ξ±​({±1,…,±n})):Hom𝒮∙​(𝐑)⁡(S,T⊔ξ±​({±1,…,±n}))→∼L±​(e|T|,e|S|,n).\varphi_{\pm}(T,S)=\phi(S,T\sqcup\xi_{\pm}(\{\pm 1,\ldots,\pm n\})):\operatorname{Hom}\nolimits_{{\mathcal{S}}^{\bullet}({\mathbf{R}})}(S,T\sqcup\xi_{\pm}(\{\pm 1,\ldots,\pm n\}))\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}L^{\pm}(e^{|T|},e^{|S|},n).

Similarly, we define φ±′:Rξ±​(−,−,en)→∼R±​(−,−,en)∘(Φ∧Φ)\varphi^{\prime}_{\pm}:R_{\xi_{\pm}}(-,-,e^{n})\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}R^{\pm}(-,-,e^{n})\circ(\Phi\wedge\Phi) by

φ±′​(T,S)=ϕ⁡(T⊔ξ±​({±1,…,±n}),S):Hom𝒮∙​(𝐑)⁡(T⊔ξ±​({±1,…,±n}),S)→∼R±​(e|S|,e|T|,n).\varphi^{\prime}_{\pm}(T,S)=\phi(T\sqcup\xi_{\pm}(\{\pm 1,\ldots,\pm n\}),S):\operatorname{Hom}\nolimits_{{\mathcal{S}}^{\bullet}({\mathbf{R}})}(T\sqcup\xi_{\pm}(\{\pm 1,\ldots,\pm n\}),S)\mathrel{\mathop{\kern 0.0pt\to}\limits^{\sim}}R^{\pm}(e^{|S|},e^{|T|},n).
0PCT

Proposition 8.1.20. Together with φ±\varphi_{\pm} (resp. φ±′\varphi_{\pm}^{\prime}), the functor Φ\Phi induces equivalences of bimodule 22-representations between Lξ±L_{\xi_{\pm}} and L±L^{\pm} (resp. Rξ±R_{\xi_{\pm}} and R±R^{\pm}).

Original mathematics by the credited authors. Source collection and HTML conversion remain in progress.

Andrew Manion, Raphael Rouquier

Original source: arXiv:2009.09627v2