Figure 1.1. The current status for the WIMP searches in direct detection. Be-cause of the inability to distinguish between neutrino and dark matter, WIMP... 25

Figure 1.2. Various methodologies searching for the sub-GeV dark matter. To search for the light dark matter, we need to find new method than nucleon... 26

Figure 1.3. The current and future experimental bounds for the light dark matter with the liecht mediators. SIMP mechanism is also testable in the left panel 29

Figure 1.4. The usual feature of the slow-roll inflation. Φ is the inflaton and slow-rolling is related with the strong Hubble friction from the inflaton equa-... 30

Figure 2.1. A figure for the dominated contents of the energy density according to the scale factor. AD era can not precede MD era due to the structure formation. 36

Figure 2.2. The effective massless and entropy degree of freedom according to the photon temperature of the universe. 38

Figure 2.3. The Coma cluster of nebulae (Left) and the rotational velocity of OB stars in M31 (Right). Left panel: Virial theorem can be used to estimate... 43

Figure 2.4. The CMB temperature map of the universe. CMB temperature map shows the existence of anisotropy explicitly. 44

Figure 2.5. The correlation function of temperature (Dl) according to the angular momentum (1) The correlation function of temperature varies with angu-...[이미지참조] 45

Figure 2.6. The gravitational lensing analysis for Bullet Cluster (Left) and X-ray analysis for the gas and plasma (Right) with the gravitational lensing contours. 46

Figure 2.7. Simulation of the large scale structure formation according to the cosmological redshift z. Image Credit: Center for Cosmological Physics 47

Figure 2.8. The matter power spectrum according to the wave number k. The red line is the ACDM prediction. It can match almost all of the data from observations. 49

Figure 2.9. A typical standard annihilation channel of a WIMP with the standard model particles 'f' (Left) and the behavior of the freeze-out process for... 51

Figure 2.10. The integrated interaction Feynman diagram for each detection method. 53

Figure 2.11. Parameter space for the Mono-γ searches from ATLAS (Left) and CMS (Right). Left panel : To show the parameter space or the Mono-γ... 54

Figure 2.12. Galactic center GeV excess from the Fermi-LAT (Left) and 3.55 keV excess from the XMM-Newton X-ray cosmic mission (Right). 56

Figure 2.13. Parameter space of WIMP direct detection for the spin-independent WIMP-nucleon cross section and WIMP mass. 57

Figure 2.14. Noble targets for the light dark matter searches (Left) and the current status of the constraints for sub-GeV dark matter (Right). Left panel:... 58

Figure 2.15. The figure for the Missing Satellite Problem. In 1999, there was a significant mismatch for the number of sub-halos and dwarf-galaxies. 59

Figure 2.16. Cusp-shaped behavior in the cold dark matter simulation (blue dotted line) and Cored shape of the observed galaxy (solid red line). This... 60

Figure 2.17. The rotational velocities are not unique and have distribution for the similar shaped galaxies. 61

Figure 2.18. Large self-interaction can solve the Cusp-Core and Too-Big-To-Fail Problems. Acceptable range for the self-interaction from the small scale prob-... 64

Figure 2.19. 3 → 2 self-annihilation and self-interaction diagrams Because the self-annihilation is a kind of self-interaction, they can have the same interac-... 65

Figure 2.20. The schematic diagram for the SIMP condition. є is a kinetic mixing angle of mediators. 66

Figure 2.21. Figures for the horizon problem (Left) and the flatness problem (Right). Left panel: The red line shows the physical scale and blue line means... 69

Figure 2.22. Figures for the solution of the horizon problem (Left) and the solution of flatness problem (Right). Left panel: Because the Hubble constant... 71

Figure 2.23. The observational parameter space for the spectral index ns and the tensor-to-scalar ratio γ at the pivot scale 0.002 Mpc-1.[이미지참조] 74

Figure 2.24. The slow-rolling behavior of the natural inflation model. 75

Figure 2.25. The canonical potential shape of the Higgs inflation model. v and λ are a vacuum expectation value and a quartic coupling of the Standard... 76

Figure 3.1. The overall resonant features for both correct and incorrect calculation results. The size of the cross section value is rescaled to compare the... 80

Figure 3.2. Approximately, the WIMP thermal average with the resonance depends on the єR1/2 (Left) and SIMP thermal average with the resonance de-...[이미지참조] 83

Figure 4.1. Typical Feynman diagrams for the self-annihilation (Left) and self-interaction (Right). The red dot means the triple coupling κ dependence. 87

Figure 4.2. Relic density for the Z₃ SIMP dark matter. The forbidden channels are much dominant than the SIMP channel in the range of mχ 〈 mz' 〈 1.5mχ[이미지참조] 89

Figure 4.3. Theoretical constraints for the Z₃ SIMP dark matter. We put the unitarity, perturbativity, stability bounds and the self-interaction values,... 92

Figure 4.4. Experimental constraints for the Z₃ SIMP dark matter. They are related to the gauge kinetic mixing angle є and the mediator mass. Also, we... 93

Figure 4.5. The parameter space for the relic density and mass of S without and with the correct treat for the resonance (red dashed and red solid). The... 95

Figure 4.6. The parameter space for the relic density of χ dark matter (Left) and S dark matter (Right) according to the mediator mass. Both of panels... 96

Figure 4.7. The Feynman diagrams for the self-annihilation and self-interaction in the vector SIMP model. SU(2)X gauge coupling can control both of the...[이미지참조] 97

Figure 4.8. Relic density plots only for the 3 → 2 channels (Left) and for the both SIMP and forbidden channels (Right). Left panel : h₁ in the plot is hDL...[이미지참조] 101

Figure 4.9. Kinetic equilibrium condition with the Higgs decay. The corresponding channel is XhDL → XhDL(→ lSMlSM). h₁ in the plot is hDL, in this...[이미지참조] 102

Figure 4.10. Kinetic equilibrium condition from the direct scattering with the Z' mediated channel, Xe- → Xe-. Also, there are many theoretical and ex-...[이미지참조] 104

Figure 4.11. The parameter space for the relic density and self-interaction. Left panel : There are generally two solutions for relic density according to the... 106

Figure 4.12. The parameter space for SIMP conditions and experimental constraints. 107

Figure 5.1. The Feynman diagrams for the self-interaction (Left) and self-annihilation (Right). There are only one self-interaction and self-annihilation... 112

Figure 5.2. Parameter space for the perturbativity problem in the minimal dark pion SIMP model. The both of the plots are same were Nc＝3, Nπ＝8. Left...[이미지참조] 113

Figure 5.3. New diagrams mediated by the vector mesons for self-interaction and self-annihilation. There are 2-π and 3-π resonances. 116

Figure 5.4. The parameter space for order parameter mπ/fπ and σself/mπ versus mπ. Top left and right panels: These two plots are the same and the...[이미지참조] 118

Figure 5.5. Experimental constraints and the SIMP conditions. If we consider the dark U(1) and Z' as a gauge boson, SIMP pion can be in the thermal... 119

Figure 6.1. The potential shape of inflection point inflation. 121

Figure 6.2. Parameter space for λ3/V0 and Nmax with the 1σ (green band) and 2σ (yellow band) of the ns from the Planck data. The large field difference...[이미지참조] 124

Figure 6.3. Parameter space of ξ and c which is defined by h0＝c/√ξ. All of the regions are trans-Planckian for χ0 field in the Einstein frame. However, in...[이미지참조] 126

Figure 6.4. Parameter space for ns and γ according to the value of ξ with fixed tan Θ and h0. In order to satisfy the spectral index measured by Planck, ξ~...[이미지참조] 127

Figure 6.5. The number of e-folding from the Horizon exit and reheating temperature with the equation of states at γ＝10-1 and γ＝10-5.[이미지참조] 128

Figure 6.6. Similar parameter space with fig. 6.3 with the various equation of states instead of the number of e-folding. 130

Figure 6.7. Similar parameter space with fig. 6.4 with the various equation of states instead of the number of e-folding. 131

Figure 7.1. Parameter space for ξ₂ vs ξ₁. The cutoff |Λ₂| can be pushed up to the Planck scale for R ~ O(1). 136

Figure 7.2. The slow-roll and measurable parameters for R and the number of e-folding. The red stars are the case of R＝0 to compare with the only...[이미지참조] 138

Figure 7.3. The slow-roll and measurable parameters by using perturbative reheating, N＝55.4 + 1/4log (γ/0.01).[이미지참조] 139

Figure 7.4. The branching ratio plots for the inflaton mass mχ. Each plot has the inflaton mass scale as 10-4 GeV 〈 mχ 〈 mc and 2.5 GeV 〈 mχ 〈...[이미지참조] 143

Figure 7.5. Parameter space for the linear non-minimal coupling and lifetime of χ for the mass of χ. The lifetime of χ is smaller than the age of the universe... 144

Figure 7.6. The parameter space for the relic density with R＝1.5,2 and γ＝0.01. λχH and mχ are constrained by the relic density, △Neff and the reheating temperature.[이미지참조] 146