Constraining Non-Einsteinian Polarizations with Pulsar Timing Arrays

Pulsar timing arrays detect gravitational waves by searching for correlated signals between a collection of millisecond pulsars. In general relativity (GR), the induced interpulsar correlations are predicted to follow the Hellings-Downs curve. Some alternative theories of gravity predict additional gravitational wave polarizations beyond the ones in GR, which would change the interpulsar correlations. In this talk, I will discuss the requirements and limitations of pulsar timing arrays to constrain non-Einsteinian polarizations, and discuss prospects with future pulsar timing arrays.