# Forster's Lower Bound

Speaker:

## Time:

Friday, 6 May 2016, 16:00 to 17:00

## Venue:

• A-201 (STCS Seminar Room)

## Organisers:

We will talk about the notion of the sign-rank of a {-1, 1}-valued matrix, which measures the robustness of it's rank under sign preserving changes.  We will first see a neat geometric interpretation of the sign-rank, and then see how showing an upper bound on the spectral norm of A implies a lower bound on its sign-rank, and also see implications in lower bounds on communication complexity and circuit complexity in certain models.

References:
Jurgen Forster. A Linear Lower Bound on the Unbounded Error Probabilistic Communication Complexity, 2001
Satyanarayana V. Lokam: Complexity Bounds using Linear Algebra