Testing Gravity with Frequency-Dependent Overlap Reduction Function in Pulsar Timing Array

Kavli Affiliate: Misao Sasaki

| First 5 Authors: Qiuyue Liang, Ippei Obata, Misao Sasaki, ,

| Summary:

The positive evidence of a nano-hertz gravitational wave background recently
found by several pulsar timing array (PTA) collaborations opened up a window to
test modified gravity theories in a unique frequency band in parallel to other
gravitational wave detection experiments. In particular, the overlap reduction
function (ORF) in PTA observation is sensitive to the phase velocity of
gravitational waves. In this work, we provide analytical expressions for the
coefficients of the multipole moments in the ORF, and utilize these analytical
results to study constraints on the phase velocity from the frequency dependent
overlap reduction function obtained from the Chinese PTA (CPTA) data. While the
data contain large error bars yet, interesting constraints are found in the
frequency-dependent ORF in the case of subluminal phase velocity. This makes us
expect that the nano-hertz band gravitational wave background will become one
of the important arenas for exploring modified gravity theories.

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