**SMS scnews item created by Haotian Wu at Sun 12 Mar 2017 2112**

Type: Seminar

Distribution: World

Expiry: 11 Sep 2017

**Calendar1: 16 Mar 2017 1200-1300**

**CalLoc1: Carslaw 535A**

CalTitle1: Geometry & Topology Seminar: Sasha Fish -- On the values of quadratic forms on difference sets or on non-periodic Bohr sets

Auth: haotianw@14-202-233-61.static.tpgi.com.au (hawu2800) in SMS-WASM

### Geometry & Topology Seminar

# On the values of quadratic forms on difference sets or on non-periodic Bohr sets (or what did I do this summer)

### Sasha Fish (Sydney)

**Thursday 16 March 12:00–13:00 in Carslaw 535A.**

Please join us for lunch after the talk!

**Abstract:**
I will be talking about a recent progress on the following question: Given a quadratic form Q in N variables (of a mixed signature) over the integers, show that the set of values:

1) Q(E-E) for a large set E inside Z^N contains a non-trivial subgroup of the integers.

2) Q(B) = Q(Z^N) for any non-periodic Bohr set B in Z^N.

Some parts of the talk are based on the joint work (in progress) with Kamil Bulinski (Sydney).