Research On Dynamic Evolution Of Non-Canonical Scalar And Parametric Model Of Dark Energy

Since the observation data in 1998 found that the universe is accelerating expansion,scientists have been committed to proposing a mechanism to explain the source of the accelerated expansion of the universe.The "cosmological constant+cold dark matter" model based on the big bang,namely ACDM model,is one of the best cosmological models that fit the current observation data as a whole.However,in some aspects,ACDM model also has problems,which is called "cosmological constant problem" as a whole,mainly including "Fine-tuning Problem","Coincidence Problem","Hubble Tension "and "S8 Tension".In order to solve these problems,dynamic dark energy is proposed.This kind of scalar field is generally similar to the slow rolling of a small ball in the potential field to provide negative pressure to drive the accelerated expansion of the universe.The analysis method of dynamic system is introduced to analyze the dark energy model,which makes the dynamic dark energy theory have a great development.The attractor characteristics in the dynamic system have become an important solution to alleviate the problems existing in some ACDM models.The first chapter of this paper first introduces some basic concepts of dynamic system and the methods used in this paper,then briefly introduces some basic cosmological concepts,and the second chapter introduces the origin of cosmic accelerated expansion and dark energy model,The third chapter is the focus of this paper.We start with the K-essence model.Under the dynamic dark energy model,we mainly use the K-essence model in the form of power law,and consider a new form of interaction between matter and dark energy which Q=??m??H-1,which is different from the previous dynamic attraction points,the new Scaling-like attractor can well alleviate the coincidence problem,and different from the previous Scaling solution,this kind of attractor can realize the acceleration and expansion of the late universe.In Chapter 4,we study the parameterized dark energy model.In the parameterized model,we choose to directly parameterize the evolution equation ?? ?? ln(1+z)+1 from K-essence in the form of L=F(X)-V(?).the corresponding EoS is ?=1/3(?/[1-N?]-3),N=ln a,where ? is the undetermined single parameter that needs to be fitted with observation data.As a result,we get that if there is no spatial curvature,?has a fitting value of-0.027-0.111+0.120?if the spatial curvature is positive,has a fitting value of-0.007-0.116+0.116,we can get the evolution form of dark energy,So as to give a reasonable explanation for the accelerated expansion of the universe.Finally,we summarize and prospect the work of this paper.