A Phenomenological Study of WIMP Models: Friedmann equations

Table of Links

Acknowledgements

1 Introduction to thesis

1.1 History and Evidence

1.2 Facts on dark matter

1.3 Candidates to dark matter

1.4 Dark matter detection

1.5 Outline of the thesis

2 Dark matter through ALP portal and 2.1 Introduction

2.2 Model

2.3 Existing constraints on ALP parameter space

2.4 Dark matter analysis

2.5 Summary

3 A two component dark matter model in a generic 𝑈(1)𝑋 extension of SM and 3.1 Introduction

3.2 Model

3.3 Theoretical and experimental constraints

3.4 Phenomenology of dark matter

3.5 Relic density dependence on 𝑈(1)𝑋 charge 𝑥𝐻

3.6 Summary

4 A pseudo-scalar dark matter case in 𝑈(1)𝑋 extension of SM and 4.1 Introduction

4.2 Model

4.3 Theoretical and experimental constraints

4.4 Dark Matter analysis

4.5 Summary

5 Summary

Appendices

A Standard model

B Friedmann equations

C Type I seasaw mechanism

D Feynman diagrams in two-component DM model

Bibliography

B Friedmann equations

Our universe at a large scale can be described well if we assume isotropy and homogeneity of space. The Friedmann-Lemaitre-Robertson-Walker (FLRW) metric hold these assumptions, which is given by,

here p and 𝜌 are the pressure and energy density of the fluid respectively whereas 𝑢𝜇 is the velocity vector in comoving coordinates. One can now derive the Friedmann equations as

Using the above two equations, one can derive the density evolution equation,

where H is the Hubble parameter.