Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail

Understand

Cauchy-characteristic evolution (CCE) is a powerful method for accurately extracting gravitational waves at future null infinity.

• In this work, we extend the previously implemented CCE system within the numerical relativity code SpECTRE by incorporating a scalar field.
• This allows the system to capture features of beyond-general-relativity theories.
• We derive scalar contributions to the equations of motion, Weyl scalar computations, Bianchi identities, and balance laws at future null infinity.