In observational cosmology,a supernova la is used as a standard candle in order to extend the Hubble diagram to a higher redshift range.Astrophysicists found that the observed brightness of high redshift supernovae la...In observational cosmology,a supernova la is used as a standard candle in order to extend the Hubble diagram to a higher redshift range.Astrophysicists found that the observed brightness of high redshift supernovae la is dimmer than expected.This dimming effect is considered observational evidence for the existence of dark energy in the universe.It should be noted that this conclusion is based on an assumption that the mass density of the cosmic plasma is very small.Therefore,the dimming effect caused by the Compton scattering of free electrons in cosmic plasma can be neglected.X-ray observations suggest that the mass density of the cosmic plasma may be very large.In theory,the observed dimming effect of high redshift supernovae Ia may be caused by the Compton scattering of free electrons in the cosmic plasma.In this paper it will be shown that this idea is reasonable.Therefore,there is no need to introduce the confusing concept of dark energy into cosmology.展开更多
We revisit the epoch of cosmic speed-up characterized by the redshift of transition from a decelerated to an accelerated phase.This redshift is termed the transition redshift(z_(t)).We use the spatially flat and non-f...We revisit the epoch of cosmic speed-up characterized by the redshift of transition from a decelerated to an accelerated phase.This redshift is termed the transition redshift(z_(t)).We use the spatially flat and non-flat variants of the most commonΛCDM and XCDM models to put constraints on the transition redshift along with the other model parameters.The data for this analysis come from the recent and updated Pantheon+supernova(SN)data set and the Hubble parameter measurements obtained from Cosmic Chronometers.We consider both data sets with their respective covariance matrices incorporating all statistical and systematic uncertainties.We observe that using the combined data sets of H(z)and SNe,the best fit value of transition redshift lies in the range 0.61<z_(t)<0.79 for all four dark energy models.Incidentally,we observe a positive curvature for the non-flat models,correlations between several model parameters and a strong degeneracy between the curvature and the equation of state parameter.展开更多
文摘In observational cosmology,a supernova la is used as a standard candle in order to extend the Hubble diagram to a higher redshift range.Astrophysicists found that the observed brightness of high redshift supernovae la is dimmer than expected.This dimming effect is considered observational evidence for the existence of dark energy in the universe.It should be noted that this conclusion is based on an assumption that the mass density of the cosmic plasma is very small.Therefore,the dimming effect caused by the Compton scattering of free electrons in cosmic plasma can be neglected.X-ray observations suggest that the mass density of the cosmic plasma may be very large.In theory,the observed dimming effect of high redshift supernovae Ia may be caused by the Compton scattering of free electrons in the cosmic plasma.In this paper it will be shown that this idea is reasonable.Therefore,there is no need to introduce the confusing concept of dark energy into cosmology.
文摘We revisit the epoch of cosmic speed-up characterized by the redshift of transition from a decelerated to an accelerated phase.This redshift is termed the transition redshift(z_(t)).We use the spatially flat and non-flat variants of the most commonΛCDM and XCDM models to put constraints on the transition redshift along with the other model parameters.The data for this analysis come from the recent and updated Pantheon+supernova(SN)data set and the Hubble parameter measurements obtained from Cosmic Chronometers.We consider both data sets with their respective covariance matrices incorporating all statistical and systematic uncertainties.We observe that using the combined data sets of H(z)and SNe,the best fit value of transition redshift lies in the range 0.61<z_(t)<0.79 for all four dark energy models.Incidentally,we observe a positive curvature for the non-flat models,correlations between several model parameters and a strong degeneracy between the curvature and the equation of state parameter.
