![]() ![]() There are a few different definitions of "distance" in cosmology which are all asymptotic one to another for small redshifts. In accord with our present understanding of cosmology, these measures are calculated within the context of general relativity, where the Friedmann–Lemaître–Robertson–Walker solution is used to describe the universe. The distance measures discussed here all reduce to the common notion of Euclidean distance at low redshift. They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is not directly observable, but is more convenient for calculations (such as the comoving coordinates of the quasar, galaxy, etc.). This red shift corresponds to a distance of about 13 billion light years if one uses the current WMAP value of 71km/s/mpc for the Hubble parameter is used. The rst reconstructs the EoS using comoving distance and the second makes use of the Hubble parameter data. ![]() In order to obtain general results, we use two model-independent approaches. Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe. We investigate the possibilities of reconstructing the cosmic equation of state (EoS) for high redshift. This option has a clear advantage, because the cosmological redshift will be defined by the same formula as the gravitational redshift 1 + z g 00 r g 00 e ( 2 ) where g 00 ( e ) and g 00 ( r ) are the time components of the metric tensor g for the emitter and receiver, respectively. Figure4illustrates the results for three combina-tions of data.
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