94,298 research outputs found
Combination of Conventional and Optimisation Techniques for Performance Prediction in Large Waterflood Projects
Imperial Users onl
Characteristic Scales of Baryon Acoustic Oscillations from Perturbation Theory: Non-linearity and Redshift-Space Distortion Effects
An acoustic oscillation of the primeval photon-baryon fluid around the
decoupling time imprints a characteristic scale in the galaxy distribution
today, known as the baryon acoustic oscillation (BAO) scale. Several on-going
and/or future galaxy surveys aim at detecting and precisely determining the BAO
scale so as to trace the expansion history of the universe. We consider
nonlinear and redshift-space distortion effects on the shifts of the BAO scale
in -space using perturbation theory. The resulting shifts are indeed
sensitive to different choices of the definition of the BAO scale, which needs
to be kept in mind in the data analysis. We present a toy model to explain the
physical behavior of the shifts. We find that the BAO scale defined as in
Percival et al. (2007) indeed shows very small shifts ( 1%) relative
to the prediction in {\it linear theory} in real space. The shifts can be
predicted accurately for scales where the perturbation theory is reliable.Comment: 21 pages, 9 figures, references and supplementary sections added,
accepted for publication in PAS
Requirements on collider data to match the precision of WMAP on supersymmetric dark matter
If future colliders discover supersymmetric particles and probe their
properties, one could predict the dark matter density of the Universe and would
constrain cosmology with the help of precision data provided by WMAP and
PLANCK.
We investigate how well the relic density can be predicted in minimal
supergravity (mSUGRA), with and without the assumption of mSUGRA when analysing
data. We determine the parameters to which the relic density is most sensitive,
and quantify the collider accuracy needed. Theoretical errors in the prediction
are investigated in some detail.Comment: 42 pages, 16 figures. v2 incorporates referee's comments: minor
corrections/clarifications with additional figures to show regions of m12-m0
plane considere
A Robust Variable Step Size Fractional Least Mean Square (RVSS-FLMS) Algorithm
In this paper, we propose an adaptive framework for the variable step size of
the fractional least mean square (FLMS) algorithm. The proposed algorithm named
the robust variable step size-FLMS (RVSS-FLMS), dynamically updates the step
size of the FLMS to achieve high convergence rate with low steady state error.
For the evaluation purpose, the problem of system identification is considered.
The experiments clearly show that the proposed approach achieves better
convergence rate compared to the FLMS and adaptive step-size modified FLMS
(AMFLMS).Comment: 15 pages, 3 figures, 13th IEEE Colloquium on Signal Processing & its
Applications (CSPA 2017
Chasing the non-linear evolution of matter power spectrum with numerical resummation method: solution of closure equations
We present a new numerical scheme to treat the non-linear evolution of
cosmological power spectra. Governing equations for matter power spectra have
been previously derived by a non-perturbative technique with closure
approximation. Solutions of the resultant closure equations just correspond to
the resummation of an infinite class of perturbation corrections, and they
consistently reproduce the one-loop results of standard perturbation theory. We
develop a numerical algorithm to solve closure evolutions in both perturbative
and non-perturbative regimes. The present numerical scheme is particularly
suited for examining non-linear matter power spectrum in general cosmological
models, including modified theory of gravity. As a demonstration, we study
weakly non-linear evolution of power spectrum in a class of modified gravity
models, as well as various dark energy models.Comment: 17 pages, 8 figures; Fig.3 updated and typos fixe
- …