Theoretical Study On Cosmological Evolution And Related Properties Of Tsallis Holographic Dark Energy Model In Loop Quantum Cosmology

Since 1998,a large amount of astronomical data have indicated that the current expansion of our universe is accelerating.Over the years,many scientific researchers have been devoting to finding a reasonable theoretical explanation for the accelerated expansion of the universe,which is also a frontier hot topic in current cosmology.So far,relevant theories have emerged one after another,in which the two mainstream theories,namely modified gravity and dark energy model,have the most research potential and are also loved by the majority of researchers.In this thesis,the cosmological evolution and related properties of the interacting Tsallis holographic dark energy model are investigated in classical Einstein cosmology and loop quantum cosmology,respectively.The main contents are as follows:In classical Einstein cosmology,by choosing the two types of infrared cut-off(i.e.,Hubble cut-off and Ricci cut-off),(1)we will deeply study the evolutionary law of density parameters,equation of state(EoS)parameters and deceleration parameters for the Tsallis holographic dark energy(THDE)model with the two different interaction forms,the research results show that the Tsallis holographic dark energy models can describe the transition of universe from dark matter-dominated to dark Energy-dominated,namely,the universe turns from decelerating expansion to accelerating expansion;(2)We will perform the three kinds of different geometric diagnoses for the THDE model,i.e.,the statefinder diagnosis,statefinder hierarchy diagnosis and composite null diagnosis(CND).The study finds that the three diagnoses can well differentiate the studied models from the ACDM model;(3)Taking the horizon as the cosmic boundary,we will explore the thermal properties of the thermodynamic system by calculating the total entropy of the cosmic components within the horizon.The research results show that the change rate of the total entropy is greater than zero within the horizon with the Tsallis holographic dark Energy-dominated,which shows the thermodynamic system satisfies the so-called the generalized second law of thermodynamics,minewhile,also satisfies the thermal equilibrium condition when choosing the Hubble cut-off.Furthermore,in the loop quantum cosmology,the two types of infrared cut-off(i.e.,Hubble cut-off and Ricci cut-off)are similarly chosen.By means of the same method mentioned above,we will study the evolutions of the cosmological quantities,three different geometric diagnoses and the related thermodynamic properties for the Tsallis holographic dark energy models with the four different interaction forms.The research results that(1)the evolutions of the related cosmological quantities to the Tsallis holographic dark energy models conforms to the laws of cosmological evolution.When choosing Hubble cut-off,the loop quantum effect has the great influence on the density parameters,EOS parameters and deceleration parameters in the early stage of the universe.However,under Ricci cut-off,its influence on the relevant cosmological quantities becomes stronger in the late stage of the universe;(2)Compared with classical Einstein cosmology,the three kinds of geometric diagnoses have more ideal diagnostic effects in loop quantum cosmology,which can effectively distinguish dark energy models corresponding to different coupling parameters,and are also well differentiated from ACDM models;(3)The model not only satisfies the generalized second law of thermodynamics,but also satisfies the thermal equilibrium condition of the thermodynamic system when the Hubble cut-off is selected.Finally,it is worth mentioning that by comparing the results in loop quantum cosmology with the ones in classical Einstein cosmology,we find that the latter is a special case of the former in the case of plc??,that is,loop quantum cosmology includes classical Einstein cosmology as a special case,which is the generalaized theory of classical Einstein cosmology.