Finite-difference conjecture for Ext dimensions of complete intersections

Let RR be a complete intersection ring with kk relations and nn variables, where k1k\geq 1. For any map f:NNf:\mathbb{N}\longrightarrow\mathbb{N}, define Δ0f(m)=f(m)\Delta^0f(m)=f(m) and Δr+1f(m)=Δrf(m+1)Δrf(m)\Delta^{r+1}f(m)=\Delta^rf(m+1)-\Delta^rf(m). Set f(m)=ExtR(C,C)(m)f(m)=\operatorname{Ext}_R(\mathbb{C},\mathbb{C})(m), with ExtR(C,C)(m)\operatorname{Ext}_R(\mathbb{C},\mathbb{C})(m) denoting the degree-mm Ext group. Finite-difference conjecture. The following hold:

  • If k=1k=1, then for every mnkm\geq n-k,
Δk1(dimExtR(C,C)(m))=2nk.\Delta^{k-1}\bigl(\operatorname{dim}\operatorname{Ext}_R(\mathbb{C},\mathbb{C})(m)\bigr)=2^{n-k}.
  • If k2k\geq 2, then for every mn(k+1)m\geq n-(k+1),
Δk1(dimExtR(C,C)(m))=2nk.\Delta^{k-1}\bigl(\operatorname{dim}\operatorname{Ext}_R(\mathbb{C},\mathbb{C})(m)\bigr)=2^{n-k}.

The preceding cases k=1,2,3k=1,2,3 motivate this numerical pattern for larger kk, but no resolution is given in the supplied text.

Sources & referencesView supporting material

Primary source

Antoine Caradot and Zongzhu Lin, “Differential graded algebras with divided powers and homotopy Lie algebras”, arXiv:2511.22614 (2026).

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