The First 380,000 Years in 10 Minutes Introduction to Baryon Acoustic Oscillations Sanha Cheong Adviser: Prof. Regina Demina Department of Physics and Astronomy University of Rochester [email protected] http://www.pas.rochester.edu/~scheong/ August 7, 2016 Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 1/13 I Started off from a singularity (infinite density and temperature) called the Big Bang I Has been expanding ever since I Homogeneous and isotropic universe (in large scale) I Decreasing in density and temperature Basic Cosmological Principle (and Assumptions) What happened (and is happening) in the universe? Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 2/13 I Has been expanding ever since I Homogeneous and isotropic universe (in large scale) I Decreasing in density and temperature Basic Cosmological Principle (and Assumptions) What happened (and is happening) in the universe? I Started off from a singularity (infinite density and temperature) called the Big Bang Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 2/13 I Homogeneous and isotropic universe (in large scale) I Decreasing in density and temperature Basic Cosmological Principle (and Assumptions) What happened (and is happening) in the universe? I Started off from a singularity (infinite density and temperature) called the Big Bang I Has been expanding ever since Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 2/13 I Decreasing in density and temperature Basic Cosmological Principle (and Assumptions) What happened (and is happening) in the universe? I Started off from a singularity (infinite density and temperature) called the Big Bang I Has been expanding ever since I Homogeneous and isotropic universe (in large scale) Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 2/13 Basic Cosmological Principle (and Assumptions) What happened (and is happening) in the universe? I Started off from a singularity (infinite density and temperature) called the Big Bang I Has been expanding ever since I Homogeneous and isotropic universe (in large scale) I Decreasing in density and temperature Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 2/13 I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 I ∼ 380; 000 yrs old = Photon Epoch First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 First 380,000 Years of the Universe First 10s of the universe... I Before then is mostly theoretical I Planck scale, inflation, SSB, etc. I More in the regime of particle physics So, how is 10s old universe? I Hot and dense plasma of (mostly H) nuclei and electrons (primordial plasma) and dark matter 4 I >> 10 K, still too hot to form neutral atoms I Random over-dense regions (inhomogeneities) I ∼ 380; 000 yrs old = Photon Epoch Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 3/13 This creates longitudinal waves in the primordial plasma: Baryon Acoustic Oscillations Photon Epoch Photons interact actively with the primordial plasma via Compton scattering. Photons and baryons are coupled. However, over-dense regions also have strong gravitational potential well due to dark matter. Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 4/13 Photon Epoch Photons interact actively with the primordial plasma via Compton scattering. Photons and baryons are coupled. However, over-dense regions also have strong gravitational potential well due to dark matter. This creates longitudinal waves in the primordial plasma: Baryon Acoustic Oscillations Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 4/13 Photon Epoch Photons interact actively with the primordial plasma via Compton scattering. Photons and baryons are coupled. However, over-dense regions also have strong gravitational potential well due to dark matter. This creates longitudinal waves in the primordial plasma: Baryon Acoustic Oscillations (a) Matter (b) Light (c) Density Plot Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 4/13 Photon Epoch Photons interact actively with the primordial plasma via Compton scattering. Photons and baryons are coupled. However, over-dense regions also have strong gravitational potential well due to dark matter. This creates longitudinal waves in the primordial plasma: Baryon Acoustic Oscillations (a) Matter (b) Light (c) Density Plot Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 4/13 Photon Epoch Photons interact actively with the primordial plasma via Compton scattering. Photons and baryons are coupled. However, over-dense regions also have strong gravitational potential well due to dark matter. This creates longitudinal waves in the primordial plasma: Baryon Acoustic Oscillations (a) Matter (b) Light (c) Density Plot Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 4/13 I Down to ∼ 4000 K by 380,000 yrs old (z ≈ 1100) I Cold enough to form neutral (hydrogen) atoms −! Recombination! I Neutral atoms do not interact electromagnetically −! Matter is now decoupled from light. But Wait! Recombination! Recall that the universe is cooling down! Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 5/13 I Cold enough to form neutral (hydrogen) atoms −! Recombination! I Neutral atoms do not interact electromagnetically −! Matter is now decoupled from light. But Wait! Recombination! Recall that the universe is cooling down! I Down to ∼ 4000 K by 380,000 yrs old (z ≈ 1100) Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 5/13 I Neutral atoms do not interact electromagnetically −! Matter is now decoupled from light. But Wait! Recombination! Recall that the universe is cooling down! I Down to ∼ 4000 K by 380,000 yrs old (z ≈ 1100) I Cold enough to form neutral (hydrogen) atoms −! Recombination! Introduction to Baryon Acoustic Oscillations Sanha Cheong, UR 5/13 But Wait! Recombination! Recall that the universe is cooling down! I Down to ∼ 4000 K by 380,000 yrs old (z ≈ 1100) I Cold enough to form neutral (hydrogen) atoms −! Recombination! I Neutral atoms do not interact electromagnetically −! Matter is now decoupled from light.