Results 31 to 40 of about 4,634,710 (292)

Probing Cosmological Parameters with GRBs [PDF]

open access: yesAIP Conference Proceedings, 2004
In light of the recent finding of the narrow clustering of the geometrically-corrected gamma-ray energies emitted by Gamma Ray Bursts (GRBs), we investigate the possibility to use these sources as standard candles to probe cosmological parameters such as the matter density Omega_m and the cosmological constant energy density Omega_Lambda. By simulating
Di Girolamo, T.   +2 more
openaire   +2 more sources

Estimating cosmological parameter covariance [PDF]

open access: yesMonthly Notices of the Royal Astronomical Society, 2014
We investigate the bias and error in estimates of the cosmological parameter covariance matrix, due to sampling or modelling the data covariance matrix, for likelihood width and peak scatter estimators. We show that these estimators do not coincide unless the data covariance is exactly known. For sampled data covariances, with Gaussian distributed data
Taylor, Andy, Joachimi, Benjamin
openaire   +2 more sources

Evolution of second-order cosmological perturbations. [PDF]

open access: yes, 1984
We present a method for constructing gauge-invariant cosmological perturbations which are gauge-invariant up to second order. As an example, we give the gauge-invariant definition of the second-order curvature perturbation on uniform density ...
Blair, D   +999 more
core   +6 more sources

Baryon Physics and Tight Coupling Approximation in Boltzmann Codes

open access: yesUniverse, 2019
We provide two derivations of the baryonic equations that can be straightforwardly implemented in existing Einstein−Boltzmann solvers. One of the derivations begins with an action principle, while the other exploits the conservation of the stress ...
Masroor C. Pookkillath   +2 more
doaj   +1 more source

A Bias-free Cosmological Analysis with Quasars Alleviating H 0 Tension

open access: yesThe Astrophysical Journal Supplement Series, 2023
Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, H _0 , obtained by Type Ia ...
Aleksander Łukasz Lenart   +4 more
doaj   +1 more source

Higgs field and cosmological parameters in the fractal quantum system [PDF]

open access: yes, 2017
For the fractal model of the Universe the relations of cosmological parameters and the Higgs field are established. Estimates of the critical density, the expansion and speed-up parameters of the Universe (the Hubble constant and the cosmological ...
Valeriy Abramov, Abramov Valeriy
core   +1 more source

The Cosmological Parameter: Constant or Dynamical

open access: yesJournal of Physics: Conference Series, 2020
After providing a brief history of the cosmological constant, some early cosmological models are discussed. The most popular current cosmological model is the ΛCDM model, but there are several problems associated with this model, e.g., the cosmological constant problem and fine tuning.
Beesham, Aroonkumar   +1 more
openaire   +1 more source

DIRECTIONAL DEPENDENCE OF ΛCDM COSMOLOGICAL PARAMETERS [PDF]

open access: yesThe Astrophysical Journal, 2013
6 pages, 7 figures, published in ...
Axelsson, M.   +5 more
openaire   +3 more sources

The dynamics of cosmological scenarios inspired by quantum gravity [PDF]

open access: yes, 2006
PhDIn this thesis we study the dynamics of cosmological scenarios inspired by quantum gravity. Part I investigates novel features of the semi-classical regime of homogeneous and isotropic loop quantum cosmology.
Mulryne, David James
core   +2 more sources

Cosmographic constraints from late-time probes including fast radio bursts

open access: yesAstronomy & Astrophysics
Context. Late-time astrophysical probes offer a powerful way to investigate the expansion history of the Universe. Among these probes, fast radio bursts (FRBs) are millisecond-duration astrophysical transients whose extragalactic origin makes them a ...
Sales Lázaro L.   +9 more
doaj   +1 more source

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