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Recently, evidence of stochastic gravitational wave background (SGWB) signalsobserved by pulsar timing array (PTA) collaborations, has promptedinvestigations into their origins. We explore the compatibility of a proposedinflationary scenario, incorporating an intermediate null energy condition(NEC)-violating phase, with the PTA observations. The NEC violation potentiallyamplifies the primordial tensor power spectrum, offering a promisingexplanation for PTA observations. Numerical analyses, primarily focused onNANOGrav's 15-year results, reveal the model's compatibility with PTA data.Notably, the model predicts a nearly scale-invariant GW spectrum in the mHzfrequency range, which sets our scenario apart from other interpretationspredicting a red primordial GW spectrum on smaller scales.

Null energy condition violation during inflation and pulsar timing array observations