27,802 research outputs found
Radial Redshift Space Distortions
The radial component of the peculiar velocities of galaxies cause
displacements in their positions in redshift space. We study the effect of the
peculiar velocities on the linear redshift space two point correlation
function. Our analysis takes into account the radial nature of the redshift
space distortions and it highlights the limitations of the plane parallel
approximation. We consider the problem of determining the value of \beta and
the real space two point correlation function from the linear redshift space
two point correlation function. The inversion method proposed here takes into
account the radial nature of the redshift space distortions and can be applied
to magnitude limited redshift surveys that have only partial sky coverage.Comment: 26 pages including 11 figures, to appear in Ap
Is Strangeness Still Strange at the LHC?
Strangeness production is calculated in a pQCD-based model (including nuclear
effects) in the high transverse momentum sector, where pQCD is expected to work
well. We investigate pion, kaon, proton and lambda production in pp and
heavy-ion collisions. Parton energy loss in AA collisions is taken into
account. We compare strange-to-non-strange meson and baryon ratios to data at
RHIC, and make predictions for the LHC. We find that these ratios significantly
deviate from unity not only at RHIC but also at the LHC, indicating the special
role of strangeness at both energies.Comment: Contribution to SQM 2007, 6 pages 2 figure
An Inversion Method for Measuring Beta in Large Redshift Surveys
A precision method for determining the value of Beta= Omega_m^{0.6}/b, where
b is the galaxy bias parameter, is presented. In contrast to other existing
techniques that focus on estimating this quantity by measuring distortions in
the redshift space galaxy-galaxy correlation function or power spectrum, this
method removes the distortions by reconstructing the real space density field
and determining the value of Beta that results in a symmetric signal. To remove
the distortions, the method modifies the amplitudes of a Fourier plane-wave
expansion of the survey data parameterized by Beta. This technique is not
dependent on the small-angle/plane-parallel approximation and can make full use
of large redshift survey data. It has been tested using simulations with four
different cosmologies and returns the value of Beta to +/- 0.031, over a factor
of two improvement over existing techniques.Comment: 16 pages including 6 figures Submitted to The Astrophysical Journa
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