Cross-correlating Astrophysical and Cosmological Gravitational Wave Backgrounds with the Cosmic Microwave Background

Abstract

General Relativity provides us with an extremely powerful tool to extract at the same time astrophysical and cosmological information from the Stochastic Gravitational Wave Backgrounds (SGWBs): the cross-correlation with other cosmological tracers, since their anisotropies share a common origin and the same perturbed geodesics. In this letter we explore the cross-correlation of the cosmological and astrophysical SGWBs with Cosmic Microwave Background (CMB) anisotropies, showing that future GW detectors, such as LISA or BBO, have the ability to measure such cross-correlation signals. We also present, as a new tool in this context, constrained realization maps of the SG-WBs extracted from the high-resolution CMB Planck maps. This technique allows, in the low-noise regime, to faithfully reconstruct the expected SGWB map by starting from CMB measurements.

CLASS_GWB: robust modeling of the astrophysical gravitational wave background anisotropies

“…The anisotropies of the GWB have already been computed by several authors, both for its cosmological [25][26][27][28][29][30][31][32][33][34][35] and astrophysical [36][37][38][39][40][41][42][43] component, using analytical and simulationbased methods. The goal of this project is to build upon these works to develop an end-to-end approach that takes the best of those two methods: (i) a rigorous analytical treatment of cosmological perturbations and (ii) a numerical and simulation-based treatment of those aspects of GW sources and hosts that cannot easily accounted for by analytical prescriptions.…”

Probing pre-Recombination Physics by the Cross-Correlation of Stochastic Gravitational Waves and CMB Anisotropies

“…Note added: While this project was nearly complete, we became aware of Ref. [78], where the cross-correlation between CMB temperature anisotropies and the cosmological and astrophysical SGWB was analyzed and used to produce constrained realization maps of the SGWB anisotropies out of the CMB ones.…”

“…We thank the authors of Ref. [78] for sharing the draft of their paper with us. Numerical computations for this research were done on the Sciama High Performance Compute cluster, which is supported by the ICG, SEPNet, and the University of Portsmouth.…”

Primordial gravitational waves from excited states

“…Although using a different method, i.e. directly solving for the mode functions Q Xi , analytical solutions were found explicitly in [40], with results generalised in [42], by considering a top-hat profile for the time dependence of the bending parameter 24 η ⊥ (N ), with height and width given by the constants η ⊥ and δ, and in the regime of a sharp turn δ 1. In particular, by setting Bunch-Davies initial conditions, the mode functions in the out and feature region take the simple forms (4.4) and (4.13), respectively.…”

“…As we will show, the latter can cause a significant production of primordial GWs at localised frequencies, both during and after inflation. With the appropriate conditions, excited states during inflation can produce observable signals accessible for instance to LISA or SKA, turning them, along with the next-generation of CMB observatories, into main contributors to the nascent field of multi-messenger primordial cosmology [21][22][23][24][25][26].…”