Upcoming galaxy surveys will allow us to probe the growth of the cosmic largescale structure with improved sensitivity compared to current missions, and will also map larger areas of the sky. This means that in addition to the increased precision in observations, future surveys will also access the ultralargescale regime, where commonly neglected effects such as lensing, redshiftspace distortions, and relativistic corrections become important for calculating correlation functions of galaxy positions. At the same time, several approximations usually made in these calculations such as the Limber approximation break down at those scales. The need to abandon these approximations and simplifying assumptions at large scales creates severe issues for parameter estimation methods. On the one hand, exact calculations of theoretical angular power spectra become computationally expensive, and the need to perform them thousands of times to reconstruct posterior probability distributions for cosmological parameters makes the approach unfeasible. On the other hand, neglecting relativistic effects and relying on approximations may significantly bias the estimates of cosmological parameters. In this work, we quantify this bias and investigate how an incomplete modelling of various effects on ultralarge scales could lead to false detections of new physics beyond the standard ÎCDM model. Furthermore, wemore »
Finding eVscale Light Relics with Cosmological Observables
Cosmological data provide a powerful tool in the search for physics beyond the Standard Model (SM). An interesting target are light relics, new degrees of freedom which decoupled from the SM while relativistic. Nearly massless relics contribute to the radiation energy budget, and are commonly searched through variations in the effective number đeff of neutrino species. Additionally, relics with masses on the eV scale (meV10 eV) become nonrelativistic before today, and thus behave as matter instead of radiation. This leaves an imprint in the clustering of the largescale structure of the universe, as light relics have important streaming motions, mirroring the case of massive neutrinos. Here we forecast how well current and upcoming cosmological surveys can probe light massive relics (LiMRs). We consider minimal extensions to the SM by both fermionic and bosonic relic degrees of freedom. By combining current and upcoming cosmicmicrowavebackground and largescalestructure surveys, we forecast the significance at which each LiMR, with different masses and temperatures, can be detected. We find that a very large coverage of parameter space will be attainable by upcoming experiments, opening the possibility of exploring uncharted territory for new physics beyond the SM.
 Award ID(s):
 1813694
 Publication Date:
 NSFPAR ID:
 10173387
 Journal Name:
 ArXivorg
 Page Range or eLocationID:
 1  17
 ISSN:
 23318422
 Sponsoring Org:
 National Science Foundation
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