Modified Chaplygin Gas (mcg) Structure Formed

In recent years, the observations from SNe Ia and WMAP indicate that theexpansion of the universe is accelerating,but this result can not explain with theStandard cosmological model which is familar to us.In order to alleviate the con-tradiction, people thought of amending the standard cosmological model.Suchcorrections are mainly embodied in two aspects: one is introducing an dynam-ics component with negative pressure ,usually referred as dark energy,which isa homogeneous distribution in the universe. The being of dark energy has beendemonstrated by WMAP.Observation shows that the universe does have this mat-ter, and the amount of dark energy occupies 73% in cosmic budget, The introduc-tion of dark energy is actually a correction of the right of Einstein gravitationalfield equation. Alternative to it,we can consider modifying the part of geometryin Einstein's equation,such as f(R) theories of gravity.since dark energy can explain the expansion of cosmic acceleration, research-ing dark energy has become an important subject of physics and astronomy.Inthis text,we firstly introduces the background knowledge of cosmology,and basedon the standard cosmological models we review the history of the universe accel-erating expansion,then we Brie?y summaries of the current established variousdark energy model.Next we introduce the structure formation,hoping to combinethe model with observation parameters,consequently estimating various dark en-ergy models.So in the third part we specifically introduced the related researchtheory and method from the linear and non-linaer regime.In the fourth section,weSelect modified Chaplygin gas (MCG) model to specific application of the the-ory. After reviewing the dynamic evolution of MCG ,we discuss the in?uenceof MCG as dark energy to structure formation from the linear and non-linearregime.For the linear part of the discussion, We choose some cosmology parame-ters to research,and make the contrast with the observation ,we find that the resultconsists well with observation.For the non-linear part,following Ref[3],we combinethe Spherical Collapse model and Press-shceter theory,dividing the nonlinear pro-cess into two phases,the first process is from forming small density contrast toturnaround.The second process is from turnaround to virialation.We respectively discuss the density contrast of turnaround and virialation ,and compared the re-sults with GCG ,LCDM ,Einstein-de sitter.The results showed that, in theearly universe,The value of the corresponding quantity of MCG is approximat-ing the one of Einstein-de sitter.So we can conclude that Modified Chaplygin Gasas dark energy can give good prediction of non-linear perturbation.