Counting polynomials with a prescribed Galois group

Seminar: 
Algebra and Number Theory Seminar
Event time: 
Tuesday, March 1, 2022 - 4:30pm
Speaker: 
Vlad Matei
Speaker affiliation: 
Tel Aviv University
Event description: 

An old problem, dating back to Van der Waerden, asks about counting irreducible polynomials degree n polynomials with coefficients in the box [H,H] and prescribed Galois group. Van der Waerden was the first to show that Hn+O(Hnδ) have Galois group Sn and he conjectured that the error term can be improved to o(Hn1).
Recently, Bhargava almost proved van der Waerden conjecture showing that there are O(Hn1+ε) non Sn extensions, while Chow and Dietmann showed that there are O(Hn1.017) non Sn, non An extensions for n3 and n7,8,10.
In joint work with Lior Bary-Soroker, and Or Ben-Porath we prove a lower bound in the case of G=An, and upper and lower bounds for C2 wreath Sn/2. The proof for An can be viewed, on the geometric side, as constructing a morphism φ from An/2 into the variety z2=Δ(f) where each φi is a quadratic form. This in turn induces a linear map An/2 to An/An. For the upper bound for C2 wreath Sn/2 we prove a monic version of Widmer's result four counting polynomials with imprimitive Galois group.

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