Informal Discovery Cosmology Seminar – University of Copenhagen

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Informal Discovery Cosmology Seminar

Speaker: Domenec Espriu (Univ. Barcelona)

Title: Local measurement of Lambda using pulsar timing arrays (PTA)

Abstract: If Lambda is different from zero gravitational waves are anharmonic in Friedmann-Robertson-Walker coordinates and although the anharmonicity is very small it gives noticeable effects for GW originating in extragalactic sources such as spiraling black hole binaries. The results indicate that the timing residuals induced by gravitational waves from such sources in PTA would show a peculiar angular dependence with a marked enhancement around a particular value of the angle subtended by the source and the pulsars, depending mainly on the actual value of the cosmological constant and the distance to the source. The position of the peak could represent a gauge of the value of $\Lambda$. The enhancement that the new effect brings about could facilitate the first direct detection of gravitational waves while representing a local measurement of Lambda