Abstract: Recently, several major international pulsar timing array collaborations, including NANOGrav, PPTA, EPTA, and IPTA, have detected a common-spectrum process resembling a gravitational wave background in their latest data, indicating that pulsar timing arrays may soon detect gravitational waves in the nanohertz band. We will report some new developments in probing novel physics through pulsar timing arrays, including the search for scalar-induced gravitational waves, gravitational wave backgrounds generated by cosmic strings, signals from ultralight vector dark matter, modes beyond tensor polarization, and gravitational wave backgrounds produced by massive gravity.
