Astrophysics (Index)About

CMB anisotropies

(variations in the spectrum of the CMB)

CMB anisotropies are variations in the spectrum of the cosmic microwave background (CMB) across the sky, essentially variations in the temperature associated with the black-body spectrums observed at various points in the celestial sphere. The variations are tiny, but they are clues, both to recombination (when the CMB was released) and what led up to it, and the effects on the CMB of passing through the universe since. Anisotropies can be classified as primary anisotropies, stemming from recombination and before, versus late time anisotropies (aka secondary anisotropies) from the effects of the universe that the photons have since passed through. Anisotropy contributors (beyond Earth atmosphere, and foreground microwave emissions from within the Milky Way):

(Diffusion damping is another primary contributor, but decreases the primary anisotropies.) The common analysis consists of a multipole expansion of the power spectrum (power meaning the square of the varying temperature-differences from the mean temperature), which is displayed as a graph of a function of power against the "l" (the degrees aka multipole moments aka multipole numbers of the spherical harmonic modes).

Anisotropies of high interest also include those of CMB polarization, which are considered a potential clue to the characteristics of primordial gravitational waves and inflation.


(CMB,cosmology)
Further reading:
https://en.wikipedia.org/wiki/Cosmic_microwave_background
http://www.astro.ucla.edu/~wright/CMB-DT.html
https://pages.uoregon.edu/jschombe/cosmo/lectures/lec23.html
https://astronomy.swin.edu.au/cosmos/C/Cosmic+Microwave+Background+Dipole
https://ui.adsabs.harvard.edu/abs/1996ASPC...94..309S/abstract
https://academic.oup.com/ptep/article/2014/6/06B101/1561631
https://astro.uni-bonn.de/~kbasu/ObsCosmo/Slides/cmb-1.pdf
https://astro.uni-bonn.de/~kbasu/ObsCosmo/Slides2019/CMB_Part2.pdf

Referenced by pages:
angular power spectrum
anisotropy
ARCADE
baryon acoustic oscillations (BAO)
CMB dipole
CMB surveys
CMBFAST
Cosmic Anisotropy Telescope (CAT)
cosmic microwave background (CMB)
COSMOSOMAS
diffusion damping
initial fluctuation spectrum
initial fluctuations
MAXIMA
missing baryon problem
non-Gaussian (NG)
polarization modes
primordial black hole (PBH)
primordial gravitational waves
quantum fluctuations
RELIKT-1
Sachs-Wolfe effect (SWE)
Saskatoon
South Pole Telescope (SPT)
spherical harmonics
Tenerife Experiment
Wilkinson Microwave Anisotropy Probe (WMAP)
Yuan-Tseh Lee Array (YTLA)

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