The cosmic microwave background: observing directly the early universe

Abstract

The Cosmic Microwave Background (CMB) is a relict of the early universe. Its perfect 2.725K blackbody spectrum demonstrates that the universe underwent a hot, ionized early phase; its anisotropy (about 80 µK rms) provides strong evidence for the presence of photon-matter oscillations in the primeval plasma, shaping the initial phase of the formation of structures; its polarization state (about 3 µK rms), and in particular its rotational component (less than 0.1 µK rms) might allow to study the inflation process in the very early universe, and the physics of extremely high energies, impossible to reach with accelerators. The CMB is observed by means of microwave and mm-wave telescopes, and its measurements drove the development of ultra-sensitive bolometric detectors, sophisticated modulators, and advanced cryogenic and space technologies. Here we focus on the new frontiers of CMB research: the precision measurements of its linear polarization state, at large and intermediate angular scales, and the measurement of the inverse-Compton effect of CMB photons crossing clusters of Galaxies. In this framework, we will describe the formidable experimental challenges faced by ground-based, near-space and space experiments, using large arrays of detectors. We will show that sensitivity and mapping speed improvement obtained with these arrays must be accompanied by a corresponding reduction of systematic effects (especially for CMB polarimeters), and by improved knowledge of foreground emission, to fully exploit the huge scientific potential of these missions.

A Fluid–Structure Coupling Analysis of a Far-Field Flat Mirror for AliCPT-1 Telescope Calibration

“…Primordial gravitational waves refer to gravitational waves generated during the early stages of cosmic formation due to the superluminal expansion of the universe [1,2]. The aim is to detect primordial gravitational waves and explore fundamental cosmic properties in order to understand the structure and evolutionary processes of the early universe, as well as the theory of cosmic inflation [3].…”