Research On The Problem Of Gamma Ray Burst Scale

Since 1998,great progress has been made in the research of cosmology.The observations of high-redshift type Ia supernovae and cosmic microwave background indicate the universe's accelerating expansion.In order to explain this phenomenon,two ways are put forward.One way is to modify Einstein equation on the left,that is to say,modify gravitation theory.The other way is to add the so-called dark energy on the right side of Einstein equation.There is no doubt that the analysis of the expansion history of the universe is clearly one of the most basic research content.However,the anisotropic observations of cosmic microwave background and SNIa has its own limitations.Gammma ray bursts are considered the most intense explosions in the Universe.Compared with SNIa,gamma photon has strong penetrability,almost not affected by the intergalactic dust material.At the same time,the average redshift of gamma ray bursts is 2?3,so gamma ray bursts can fill the redshift gap between cosmic microwave background radiation and SNIa.In the first chapter,we mainly introduced the basic knowledge of gamma ray bursts.In the second chapter,we use ?2 fitting method for six luminosity correlations to get their best parameter values.Luminosity correlation is the correlation between observables and absolute luminosity or energy of gamma ray bursts.But the determination of parameter values in luminosity correlation are obtained in the case of particular cosmological model,so by using data of gamma ray burst to limit the cosmological model has a so-called circulation problem.We simultaneously minimize ?2 with respect to both correlation parameters and function parameters.With the help of principal component analysis,we first reduce the dimensionality of trainning set which is the ensemble of H0-independent comoving angular diameter vector.Then we combine correlation parameters with parameters which remained after dimension reduction,by using the Levenberg-Maxquardt(L-M)technique to minimize ?2,we obtain optimal values of parameters in luminosity correlation.Meanwhile,we classify the gamma ray bursts as high redshift and low redshift by their redshifts more than 1.4 or less than 1.4.Fitting in the same way respectively,then we judge whether the luminosity relations changes with the red shift.