Can we test cosmic homogeneity and isotropy?

Dr. Jenny Wagner, 2024-03-19

Galaxy & Cosmology Seminar

https://astro.tsinghua.edu.cn/info/1120/2798.htm

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Introduction

1. simple Friedmann equation at 0-rd level.

2. boundary condition

• [ ] average against GR?

1. define homogeneity and isotropy

clever option 2!

nowadays idea: op3.

Test of cosmic homogeneity and isotropy

possible tensions between observation and theory?

Matter test

• arc distrubution of GRB, galaxy.

Matter 2: do we have a peculiar velocity? right fig: degenaracy between the peculiar velocity and hubble flow.

Matter 3: CMB dipole v.s. cosmic matter dipole

• radio galaxies from NVSS, 2.7 sigma
• ~million quasars from WISE, 4.4 sigma
• (wait for 5 sigma)
• possible solution:
  • see the redshift evolution?

Space-time test

1. uniqueness of Friedmann model parameters

• Hubble tension

2. curvature test

general comments

fitting problem in cosmology

Summary

data-driven era now!