1. Click to add Text Cosmology (Astrophysics) Bill Rutherford Dec 12 2014

2. What is Cosmology? Cosmology is the study of the origin, evolution and fate of the universe The Hubble parameter H characterizes the observed expansion which all models are obliged to explain H = v/d recession velocity over distance (often measured by red shift) or H = /a the change in scale factor over the scale factor of the universe

3. Big Bang with Inflation 1 Initial Anomaly 2 Quantum Fluctuations 3 Inflation 4 Cosmic Background Radiation 4 -> 5 Dark Ages 5 First Stars & Reionization 6 Formation of Galaxies 7 Acceleration of Expansion Image courtesy NASA

4. What is the Big Bang theory? Theory that the universe began as a hot, dense, uniform soup of particles that filled space uniformly, and was expanding rapidly How the early universe expanded and cooled How the light chemical elements formed How matter congealed to form stars, galaxies, and clusters of galaxies

5. Big Bang Ω M + Ω R + Ω Λ = 1 a(τ) parametrises uniform expansion of the universe τ = conformal distance/speed of light Dark Energy Radiation Dominated for ~47,000 yrs Matter Dominated for ~ 8.8 B yrs Dark Energy Dominated ~5 B yr ago now

6. What is Cosmic Inflation? a(t) increases by ~e 60 Inflation is a modification of the standard big bang theory, providing a very brief prequel What caused the expansion? (big bang theory describes only the aftermath of the bang) Where did the matter come from? (big bang theory assumes that all matter existed from the very beginning)

7. Inflation via Gravitational Repulsion The positive energy of the repulsive gravity material (inflaton) was compensated by the negative energy of gravity. The total energy of the universe may very well be zero. Matter + Dark Matter + Radiation Gravity Total Energy =+ ~ 0

8. Status 2014 The cosmic microwave background (CMB) has a faint pattern in it preserved from accumulated activity, which is being analyzed By studying the CMB cosmologists can extract information regarding the history of the Universe, such as ordinary matter, dark matter, dark energy, and the curvature of the Universe

9. Status 2014 It has been possible to infer model parameters from analyzing observational data and comparing to alternative explanations The best fit so far is a model called ΛCDM which is shorthand for “inflationary cosmology with cold dark matter and a cosmological constant”

10. Status 2014 The latest Planck results affirm the ΛCDM model excluding some scale invariant sub-models The current Hubble parameter was measured to be 67.80±0.77 (km/s)/Mpc Images courtesy ESA - Planck The B-mode polarization data will be released in Q1 of 2015 The B-mode ratio factor has been estimated as constrained to 0.11 by dust and other effects

11. Particle Overview Image courtesy LBNL Quantum foam event(s)

12. Status 2014 It is assumed that the primordial universe supports quantum wave phenomena as is generally the case It appears quantum wave activity present in the inflationary scalar field was then propagated in following stages This pattern was apparently transformed in scale from smaller than a proton to larger than a galaxy by inflation then expansion

13. Evidence? Image courtesy CALTECH We are viewing the universe through a local distribution of mass, energy and fields Earth

14. Evidence? Image courtesy ESA - Planck Multifrequency scan of Cosmic Microwave Background (CMB)

15. Evidence? Image courtesy ESA - Planck Dust Map We are viewing the universe through a dust cloud

16. Evidence? Image courtesy Coldcreation The CMB is coming through a maze of intermediate factors

17. Evidence? Images courtesy NASA- Hubble The CMB is viewed through a field of galaxies and particles

18. Evidence? When radiation was still trapped by matter, the tightly coupled system of photons, electrons and protons behaved as a single gas or fluid, with photons scattering off electrons like ricocheting bullets As in the air, a small disturbance in gas density would have propagated as compression waves The compressions heated the gas and the rarefactions cooled it, so any disturbance in the early universe resulted in a shifting pattern of temperature fluctuations.

19. Evidence? Right after recombination you see an isotropic CMB (blue circle in centre, same in all directions) since only photons from the region right around you have had time to reach you. As time progresses, you see photons from more distant regions. You first see a quadrupole variation around you (red and blue at 90 degree angles), then an octopole, etc. by the current epoch some 10 billion years later what you see is very fine angular scale structure in the CMB temperature.

20. Evidence? Image courtesy ESA - Planck Fine angular structure of CMB temperature variations (~70 µK)

21. Evidence? Image courtesy Wayne Hu – PhD Thesis – Berkeley 1995 The LSS has density structure which scatters photons, the density variations are responsible for subsequent gravitational evolution

22. Evidence? Image courtesy ESA - Planck The angular power spectrum peak at about 1° corresponds to the density variations ΛCDM prediction l = 180/ Ѳ

23. Evidence? Image courtesy Bryan Christie Design The event horizon never allows thermal equilibrium to occur except during inflation

24. Evidence for Inflation The cosmic background radiation is uniform in temperature to 1 part in 100,000. It was released when the universe was about 370,000 years old. In standard cosmology without inflation, a mechanism to establish this uniformity would need to transmit information at ~100 times the speed of light. In inflationary models, the universe begins so small that uniformity is easily established - just like the air in this room spreading to fill it uniformly. Then inflation stretches the region to be large enough to include the visible universe.

25. Inflation Details The process of inflation consists of three steps: Prior to the expansion period, an inflaton field was at a higher-energy state (false vacuum). Random quantum fluctuations triggered a phase transition whereby a part of the inflaton field decayed releasing its potential energy, as it settled to a lower energy state (the rest just kept on expanding) This action generated a repulsive force that drove a bubble to expand

26. Evidence for Inflation According to general relativity, the flatness of the universe is related to its mass density: Image courtesy NASA WMAP closed open flat

27. Evidence for Inflation A universe at the critical density is like a pencil balancing on its tip. If Ω in the early universe was slightly below 1, it would rapidly fall to zero - and no galaxies would form If Ω was slightly greater than 1, it would rapidly rise to infinity,the universe would recollapse, and no galaxies would form To be as close to critical density as we measure today, at one second after the big bang, Ω must have been equal to one to 15 decimal places, i.e. Ω M + Ω R + Ω Λ = 1

28. Evidence for Inflation Since inflation makes gravity become repulsive, the evolution of Ω changes too. Ω is driven towards one, extremely rapidly (it could begin at almost any value) Since the mechanism by which inflation explains the flatness of the early universe almost always overshoots, it predicts that even today the universe should have near critical density

29. Evidence for Inflation Until 1998, observation pointed to Ω ≈ 0.2–0.3. Latest observations by the ESA Planck satellite (combined with other astronomical observations): Ω = 1.0010 ± 0.0065 with dark energy ~68.3% In 1998 it was discovered that the expansion of the universe has been accelerating for about the last 5 billion years Dark energy is causing this to happen

30. Slow Roll Inflation Scalar Field Potential Energy Matter Creation Expansion Quantum Fluctuations Slow Roll Field within event horizon and at “thermal equilibrium” End of Inflation Quantum contributions to seeding CMB power spectrum

31. Pressure Wave The dark matter only interacts with gravity and so stays near the centre Before decoupling (due to expansion cooling), the photons and baryons move together After decoupling photons are interacting less with baryonic matter so they diffuse away This relieves the pressure leaving baryonic matter at a location often referred to as the sound horizon

32. Pressure Wave Start with a single density perturbation The plasma is totally uniform except for a small excess at the origin (at the end of inflation) High pressure drives the gas + photon fluid outward at ~0.5c leaving dark matter behind

33. Pressure Wave Initially both the photons and the baryons move outward together This wave continues for ~10 5 years at the same time covariantly as the universe is expanding

34. Pressure Wave After ~3.7 x 10 5 years the universe has cooled enough for protons to capture electrons forming neutral Hydrogen This decouples the photons which stream away leaving the baryon peak stalled Baryons Photons

35. Pressure Wave The photons continue to stream away forming the CMB while the baryons, having lost their motive pressure, remain in place Baryons Photons Sound Horizon

36. Pressure Wave Photons become more uniform, baryons remain over dense in a shell ~100 Mpc in radius at 370,000 years 100 Mpc Baryons Photons

37. Pressure Wave The final configuration is a peak at the centre and an “echo” in a spherical shell Baryons Photons CMB spectrum Scaffold for massive black holes e.g. at centre of galaxies

38. Pressure Wave There are also several lower amplitude harmonics of the main wave similar to a flute

39. Power Spectrum Image courtesy ESA - Planck 1 st Fundamental Wave 2 nd Harmonic Wave 3 rd Harmonic Wave Damping Tail

40. Multiverse Overview Image courtesy National Geographic Continuous inflation infers a multiverse

41. M Theory Steinhardt–Turok model Collision of 2 out of many multidimensional spaces called branes (from string theory) Predicts similar physical data to inflation but from a lower initial temperature Lower prediction than inflation for gravity waves and hence B-modes

42. Inflation Gravity Waves Image courtesy CALTECH - BICEP2

43. What is B-Mode Polarization? Image courtesy CALTECH - BICEP2 Tensor Mode (T) Scalar Mode (S)

44. B-Mode Evidence Image courtesy University of Chicago – Wayne Hu As the tensor mode gravity waves (T) increase relative to the density waves (S) a B-polarization mode appears close to the main peak Cross = temperature- polarization cross power spectra

45. B-Mode Evidence Image courtesy CALTECH - BICEP2 Patch of the CMB viewed from a south pole observatory

46. B-Mode Research The tensor to scalar mode ratio factor (r) for B-Modes to E-Modes is approximated as r = 16 where is a slow roll inflation parameter the parameter ~ - Ḣ /H 2 Thus r directly probes and constrains the value of the Hubble parameter (H) during inflation

47. Gaussian Research Recent research is concentrating on the presence of subtle non Gaussian effects in the CMB spectra

48. Open Discussion