1. February 16, 2009Scott Dodelson, AAAS Meeting Gravitational Waves as a Probe of the Early Universe

2. February 16, 2009Scott Dodelson, AAAS Meeting Consider the United States in 1790 Over-densities of order 50 Concentrated in East Vast Voids with low density

3. February 16, 2009Scott Dodelson, AAAS Meeting Consider the United States Today Over-densities of order 10,000 Concentration in coasts Traces of primordial density (Boston- Washington; East > West) Vast Voids

4. February 16, 2009Scott Dodelson, AAAS Meeting The story of this evolution is the story of the United States When we understand the evolution from one map to another, we can understand the sociological, economic, and political forces acting on the US the people, or the constituents, of the US

5. February 16, 2009Scott Dodelson, AAAS Meeting Less parochially, we rely on cosmic maps WMAP Sloan Digital Sky Survey Today, there are huge overdensities: the density in this room is 10 30 larger than in an average spot in the Universe This map of the Cosmic Microwave Background (CMB) shows that the photon/baryon distribution was smooth to one part in 10,000 at t=400,000 years.

6. February 16, 2009Scott Dodelson, AAAS Meeting Less parochially, we rely on cosmic maps This map of the Cosmic Microwave Background (CMB) shows that the photon/baryon distribution was smooth to one part in 10,000 at t=400,000 years. WMAP Sloan Digital Sky Survey Today, there are huge overdensities: the density in this room is 10 30 larger than in an average spot in the Universe Modern Cosmology quantitatively explains this evolution: Gravitational Instability

7. February 16, 2009Scott Dodelson, AAAS Meeting Quantifying Cosmic Evolution has led to great Discoveries Kravtsov et al. Cosmic Web Dark Sector Galaxy Formation

8. February 16, 2009Scott Dodelson, AAAS Meeting Lingering Question Who/what planted the seeds of structure?

9. February 16, 2009Scott Dodelson, AAAS Meeting Was it even possible? Hubble Radius (Distance light travels as the Universe doubles in size) at t=400,000 years How are these two spots correlated with one another?

10. February 16, 2009Scott Dodelson, AAAS Meeting The Horizon Problem Distance Time Distance between 2 spots in CMB t = 400,000 yrs Hubble Radius

11. February 16, 2009Scott Dodelson, AAAS Meeting The Horizon Problem Distance Time Distance between 2 spots in CMB t = 400,000 yrs Hubble Radius

12. February 16, 2009Scott Dodelson, AAAS Meeting The Horizon Problem Distance Time Distance between 2 spots in CMB t = 400,000 yrs Hubble Radius Be careful extrapolating backwards …

13. February 16, 2009Scott Dodelson, AAAS Meeting Expansion is Governed by the Constituents of the Universe Early times correspond to large energies The Standard Model of Particle Physics has been tested up to ~100 GeV Higher energies/earlier times might bring new particles/forces

14. February 16, 2009Scott Dodelson, AAAS Meeting Probe Unification of Physics at High Energy George Rieke LHC Tevatron Seeds of Structure

15. February 16, 2009Scott Dodelson, AAAS Meeting Distance Time Distance between 2 spots in CMB t = 400,000 yrs Hubble Radius Inflation Solves the Horizon Problem Inflation

16. February 16, 2009Scott Dodelson, AAAS Meeting The Seeds of Structure Einstein’s Theory of General Relativity associates over-dense regions with distortions in the fabric of space-time. What was distorting Space-Time during Inflation?

17. February 16, 2009Scott Dodelson, AAAS Meeting Quantum Mechanical Fluctuations Ubiquitous on the sub-atomic level … Inflation stretches them to astronomical sizes

18. February 16, 2009Scott Dodelson, AAAS Meeting Seeds of Structure  Quantum mechanical fluctuations generated during inflation  Perturbations freeze out when distances get larger than horizon  Evolution when perturbations re-enter horizon Distortions in Space-Time

19. February 16, 2009Scott Dodelson, AAAS Meeting Sealing the Deal & Identifying the Physics Einstein’s theory allows for different types of distortions in the fabric of space-time. Seeds of structure are scalar or density perturbations. There are also tensor perturbations or gravitational waves. Scalar/Density Tensor/Gravitational Waves

20. February 16, 2009Scott Dodelson, AAAS Meeting Gravitational Waves are Produced, e.g., in Collisions of Black Holes But they are also produced microscopically due to quantum mechanics … just like density perturbations.

21. February 16, 2009Scott Dodelson, AAAS Meeting How can we detect Primordial Gravitational Waves? Backer, Jaffe, Lommen 2003 Primordial Signal Measure Polarization of Cosmic Microwave Background

22. February 16, 2009Scott Dodelson, AAAS Meeting Compton scattering of unpolarized anisotropic radiation produces polarization Require Quadrupole (small before t=400,000 yrs) Require Compton scattering (rare after t=400,000 yrs) Signals factor of 10 smaller than temperature anisotropies

23. February 16, 2009Scott Dodelson, AAAS Meeting Polarization field decomposed into E- and B- modes Mission Concept Study: Theory 2008

24. February 16, 2009Scott Dodelson, AAAS Meeting Polarization field decomposed into E- and B- modes Mission Concept Study: Theory 2008 Density perturbations produce only E-modes

25. February 16, 2009Scott Dodelson, AAAS Meeting Polarization field decomposed into E- and B- modes Mission Concept Study: Theory 2008 Density perturbations produce only E-modes Gravity waves produce E- and B- modes

26. February 16, 2009Scott Dodelson, AAAS Meeting Results Samtleben, Staggs, & Winstein 2008 E-modes have been detected: their spectrum agrees with theoretical prediction

27. February 16, 2009Scott Dodelson, AAAS Meeting New QUAD Results Pryke et al. 2008

28. February 16, 2009Scott Dodelson, AAAS Meeting Scientists are voting with their feet

29. February 16, 2009Scott Dodelson, AAAS Meeting Scientists are voting with their feet

30. February 16, 2009Scott Dodelson, AAAS Meeting We have sharpened questions that have been asked for millennia … “Who Created These?” Isaiah 40:26 … and we have real hopes of answering them over the coming decade. What physics drove inflation in the early universe, thereby producing the seeds of structure?