Status of Cosmic Microwave Background Observations for the Search of Primordial Gravitational Waves

Abstract

The cosmic microwave background (CMB) is one of the most powerful tools for cosmology. Its polarization could have imprinted the sign of an inflationary background of gravitational waves, which is supposed to have originated at 10−38/10−35 seconds after the Big Bang. Detecting this background is extremely difficult because of the weakness of the signal (if any) left on the CMB polarization and because of the need to control the systematic effects. Additionally, the presence of astrophysical foregrounds, the possibility of leakage from curl-free to curl-like components, including gravitational lensing, and the instrumental noise and systematics, require sensitive detectors and smart systematic effect control. We discuss the experimental efforts spent in this field, highlighting the key observational difference and the choice that could lead, in the near future, to the detection of the curl component of the CMB polarization, a clear sign of the inflationary expansion.

Cosmic Microwave Background Observations: looking for the Cosmic Web through the Sunyaev Zeldovich effect

“…Studying the primary anisotropies and the polarization of the CMB is allowing us to enter into the so called precision cosmology. Within this framework, we can derive the cosmological parameters with extreme precision and know the energy content of our universe to a fraction of a percent [20,1].…”

Observing galaxy clusters and the cosmic web through the Sunyaev Zel’dovich effect with MISTRAL

“…Studying the primary anisotropies and the polarization of the CMB is allowing us to enter into the so called precision cosmology. Within this framework, we can derive the cosmological parameters with extreme precision and know the energy content of our universe to a fraction of a percent [1,17].…”

Cryogenic Systems for Astronomical Research in the Special Astrophysical Observatory of the Russian Academy of Sciences

“…At the lower boundary of the band (100 GHz), the atmosphere gives not very significant absorption almost everywhere, and observatories are located even on the seashore [11]. The upper edge of the sub-THz range is open to ground observations only in unique places on Earth, such as the Atacama Desert [1,2], Pamir [12], Tibet [13], Mauna Kea, Hawaii [14], and the Antarctic Plateau [15]. In the central part of the sub-THz range, the atmospheric transparency windows are 1.3 mm (~230 GHz) (the operating range of the current Event Horizon Telescope (EHT) [16]) and especially 0.8 mm (~375 GHz) (the EHT perspective window), which is highly critical for choosing the location of the observatory.…”