Groundwork for Estimating TDI Armlength Variables During Science Analysis @LISAcommunity

Uploaded August 2020 | Updated September 2026, 3 minutes ago

Groundwork for Estimating TDI Armlength Variables During Science Analysis
Jessica Page ,Tyson Littenberg

The light travel time between the LISA spacecraft (S/C) is typically considered as input for Time Delay Interferometry (TDI) processing. Alternatively, including TDI parameters in the LISA data model -- suggested in Tinto et al (2004) -- as part of a global fit analysis pipeline produces gravitational wave inferences that are marginalized over uncertainty in the spacecraft separations and provides an independent measure of the spacecraft orbits. As an initial step toward these goals, inferences on the LISA armlengths found by minimizing the laser frequency noise in the Michaelson XYZ TDI channels for a rigidly rotating S/C configuration (TDI 1.5) are demonstrated using a Markov Chain Monte Carlo algorithm. The likelihood function includes correlations between the XYZ channels via a parameterized noise covariance matrix for the general case of unequal LISA arms. Simulated laser frequency noise is analyzed and posteriors using the orthogonal TDI channels (AET) and both the equal and unequal-arm Michaelson channels are compared.

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$Stochastic background of gravitational waves from turns in the landscape Stochastic background of gravitational waves from turns in the landscape Jacopo Fumagalli,Sebastien Renaux-Petel,Lukas Witkovski We have recently proposed a new model-independent mechanism for producing primordial black holes from a period of multi-ﬁeld inﬂation. The desired enhancement of primordial ﬂuctuations at short scales naturally occurs when the inﬂationary trajectory exhibits a strong turn, that is a limited period during which the trajectory strongly deviates from a geodesic in ﬁeld space. The mechanism, independently of being able to account for all or a fraction of dark matter in the form of primordial black holes, has the potential of exhibiting unique features accessible to observation through a stochastic background of gravitational waves. The peculiar features in the induced gravitational waves spectrum, such as characteristic peaks and oscillating patterns, oﬀers the possibility to link the microscopic dynamics of inﬂation with the gravitational waves energy density potentially detectable by LISA.$

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