combinatorics / Algebraic combinatorics: Kazhdan-Lusztig polynomials and Bruhat order

The combinatorial invariance conjecture for Kazhdan-Lusztig polynomials

Theorem 1.1: for arbitrary Coxeter systems (W,S)(W,S) and (W′,S′)(W',S'), including infinite and noncrystallographic ones, and u≤bu\le b, u′≤b′u'\le b', any poset isomorphism [u,b]→[u′,b′][u,b]\to[u',b'] gives Pu,bW=Pu′,b′W′P^W_{u,b}=P^{W'}_{u',b'} for the equal-parameter polynomials; restricting to subintervals determines every Px,yP_{x,y} and, by reciprocity, every RR-polynomial on the interval. The proof uses moment-graph sheaves (Braden-MacPherson, Fiebig, Elias-Williamson), an edge schedule transported from a reflection order of the second system, and Dyer's path formula. It gives no procedure computing PP from the poset, and it treats equal parameters only.

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combinatoricsSep 24, 2026Significance 52/100Registry: lean checked

The combinatorial invariance conjecture for Kazhdan-Lusztig polynomials

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Theorem 1.1: for arbitrary Coxeter systems (W,S)(W,S) and (W′,S′)(W',S'), including infinite and noncrystallographic ones, and u≤bu\le b, u′≤b′u'\le b', any poset isomorphism [u,b]→[u′,b′][u,b]\to[u',b'] gives Pu,bW=Pu′,b′W′P^W_{u,b}=P^{W'}_{u',b'} for the equal-parameter polynomials; restricting to subintervals determines every Px,yP_{x,y} and, by reciprocity, every RR-polynomial on the interval. The proof uses moment-graph sheaves (Braden-MacPherson…

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Theorem 1.1: for arbitrary Coxeter systems (W,S)(W,S) and (W′,S′)(W',S'), including infinite and noncrystallographic ones, and u≤bu\le b, u′≤b′u'\le b', any poset isomorphism [u,b]→[u′,b′][u,b]\to[u',b'] gives Pu,bW=Pu′,b′W′P^W_{u,b}=P^{W'}_{u',b'} for the equal-parameter polynomials; restricting to subintervals determines every Px,yP_{x,y} and, by reciprocity, every RR-polynomial on the interval. The proof uses moment-graph sheaves (Braden-MacPherson, Fiebig, Elias-Williamson), an edge schedule transported from a reflection order of the second system, and Dyer's path formula. It gives no procedure computing PP from the poset, and it treats equal parameters only.

Theorem 1.1: for arbitrary Coxeter systems (W,S)(W,S) and (W′,S′)(W',S'), including infinite and noncrystallographic ones, and u≤bu\le b, u′≤b′u'\le b', any poset isomorphism [u,b]→[u′,b′][u,b]\to[u',b'] gives Pu,bW=Pu′,b′W′P^W_{u,b}=P^{W'}_{u',b'} for the equal-parameter polynomials; restricting to subintervals determines every Px,yP_{x,y} and, by reciprocity, every RR-polynomial on the interval. The proof uses moment-graph sheaves (Braden-MacPherson, Fiebig, Elias-Williamson), an edge schedule transported from a reflection order of the second system, and Dyer's path formula. It gives no procedure computing PP from the poset, and it treats equal parameters only.

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