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If P is a lattice polytope, then one can define a polynomial
deltaP(t), which encodes the number of lattice points
in any fixed dilation of P. The polynomial deltaP(t)
is a classic combinatorial invariant, called the Ehrhart delta-polynomial
of P. We will present a new geometric interpretation of the coefficients
of deltaP(t). That is, they are sums of dimensions of orbifold
cohomology groups of a toric stack. As a combinatorial application, we will
prove a weighted version of Ehrhart Reciprocity.
After the seminar we will take the speaker to lunch. See the Algebra Seminar web page for information about other seminars in the series. Anthony Henderson anthonyh@maths.usyd.edu.au. |