涩里番

Title: A positive combinatorial rule for psi class products on multicolored spaces

Abstract: It is well known that a product of psi classes on the moduli space M_{0,n}-bar, the most commonly studied compactification of the moduli space M_{0,n} of choices of n distinct marked points on P^1, is equal to a multinomial coefficient and has many natural combinatorial interpretations. However, simple positive combinatorial formulas are more elusive for other natural compactifications of M_{0,n}, including Hassett spaces in which the points are "weighted", in addition to the "multicolored" setting in which the marked points are assigned colors. We demonstrate, in the case of multicolored spaces, how an alternating sum formula can be simplified to a positive combinatorial rule via a sign-reversing involution, and discuss some applications of the formula.

Location: UQAM PK-5675

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