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Probing inflation, dark matter, dark energy, etc. using the Lyman-alpha
forest
Patrick McDonald (CITA)
Cosmologists work to answer some of the oldest questions of humanity:
How did
the Universe begin? What is it made of? What rules does it follow?
Observations
of the large-scale structure (LSS) of the Universe address these
questions in several ways: Measurements of the scale dependence of
density fluctuations tell us about the initial conditions for structure
formation, set in the very early Universe. Measurements of the
expansion and growth of structure with time tell us about the matter
content and gravitational laws. I will mostly discuss one LSS probe:
the Lyman-alpha forest (LyaF) - the absorption in high redshift quasar
spectra by neutral hydrogen in the intergalactic medium. The LyaF
provides a good probe of the density field over the redshift range
z~2-5 on scales down to tens of kiloparsecs. When combined with the
CMB on larger scales, the LyaF observed in thousands of quasar spectra
from the Sloan Digital Sky Survey (SDSS) currently provides the best
constraints on the power spectrum of initial density perturbations,
neutrino masses that affect structure formation, and warm dark matter.
These constraints should improve significantly in the near future. I
will also discuss the SDSS-III/BOSS survey, the next generation of
SDSS-LSS, which will focus on probing dark energy using the standard
ruler provided by the baryonic acoustic oscillation feature, detectable
both in galaxy clustering at z~0-0.7 and Lyman-alpha forest absorption
at z~2-3.
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