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The nil-Hecke algebra of a Weyl group $W$ is a version of the Hecke algebra of $W$ where the square of each simple generator $T_i$ is set equal to zero. For each $w\in W$, one defines an element $T_w$ of the nil-Hecke algebra to be a product of simple generators $T_i$ corresponding to a reduced factorization of $w$. It is known that the resulting element $T_w$ is independent of the choice of reduced factorization of $w$ and, moreover, the elements $T_w, w\in W$, form a basis of the nil-Hecke algebra. Further, the nil-Hecke algebra acts naturally on the space of polynomials on the Cartan subalgebra by divided difference operators, aka BGG-Demazure operators.

I am interested in the basis element $T_w$, as well as its action on the space of polynomials, in the particular case where $w$ is a Coxeter element of $W$. Has that particular element appeared somewhere before, eg., when $W$ is the Symmetric group ?

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    $\begingroup$ @Victor: I guess you are working in the framework of Kostant and Kumar? It would be helpful to add a background reference for the basic construction and properties such as the action on polynomials. (Also, I'm unsure why you use the term "algebra" rather than just "ring" here. In the Kostant-Kumar construction of the nil Hecke ring there is no direct use of a generic Iwahori-Hecke algebra or its various specializations.) $\endgroup$ Commented Nov 21, 2012 at 17:44
  • $\begingroup$ I don't think this answers your question, so I'll leave it as a comment. In Khovanov-Lauda's paper `A diagramatic approach to categorification of quantum groups II', equations (11)-(13) give some formulas for the interaction between $T_w$, $w$ the Coxeter element, and certain idempotents acting on polynomials ($W$ is the symmetric group). These formulas are then used to prove the categorical Serre relations, which takes the form of an exact sequence. One of the maps is given by multiplying by the Coxeter element in the quiver Hecke algebra. $\endgroup$
    – David Hill
    Commented Nov 27, 2012 at 15:38

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