Beyond Einstein Modern cosmology begins with Einstein’s seminal paper of 1917 in which he first brought together comoslogy and GR. Since that time, we have been on a noble quest to understand the origin and evolution of the universe. IN the last 10 years, that quest has taken a dramatic turn thanks to the host of new technologies that have opened eyes up to the distant universe for the first time in human history. From the wealth of data that has been collected over the last decade, a consensus model has emerged

Einstein 2004 Consensus Model Hot Big Bang Inflation Radiation 1917 2004 Consensus Model Hot Big Bang Inflation Radiation From all of these observations there has emerged a consensus model, a merging of the hot big bang model of Friedmann, Lemaitre and Gamow, inflationary cosmology of the 1980s, and Dark Energy. This consensus model agrees with all current observations. This is signficant cause for celebration. However, it does not mean our job is done yet, or that this model is necessarily correct. First of all, this is not really a model at all. It is a scenario. We do not understand how the ingredients in this model emerge from fundamental physics. Is the big bang a beginning of time, as supposed? What field or fields drive inflation? What is the dark matter that played such an important role in the formation of stars, galaxies and clusters. And what is the dark energy that is overtaking the universe and determining our future. At the moment, we have lots of possible answers to each of these questions, and these are woven together in a wide family of models with different predictive power. To address these questions is going to require every technology available – everything considered in this meeting PLUS there are likely to be important inputs from LHC, measurements of CP violation, neutrino detection and dark matter searches PLUS tests of general relativity and for time-variation of couplings. Searches for gravitational waves and understanding the nature of black holes is also likely to be influential. And then, there remains the possibility that maybe, just maybe, the whole picture is wrong. In cosmology, we must be aware that ours is not a tabletop science where we are free to explore at will. We can only observe from one vantage point in the universe and gather bits and pieces of evidence from which we reconstruct a history. There is always the worry of radical alternative possibility. This morning I have been asked to focus on inflation, which is the keystone to this whole picture. I will try to explain what is needed theoretically and empirically to address these two questions. REPEAT THEM How do the ingredients for inflation emerge from fundamental physics and what about the possibility of a radical alternative. (Dark) Matter Dark Energy

Inflation: Open Issues Einstein 1917 Inflation: Open Issues What causes the acceleration? What is the inflaton? and why are its couplings so finely tuned? Predictions uncertain? Transplanckian effects? Ironically, while tremendous progress has been made on the observational front in supporting inflation, little progress has been made on the theoretical front. In fact, if anything there has been retrogress. A question that has been with us since the first days after new inflation has been. Variants? Dark Energy?

Inflation: What to do? Einstein 1917 Inflation: What to do? Determine if “simple”, “minimal” inflation explains our universe: single field single characteristic mass scale uniformly varying equation of state minimum required fine-tuning I think it will take quite an effort to resolve these issues. The most important thing we can do in the meantime is push on observations to determine if a simple, minimal version of inflation explains our universe. I think this, more than anything else, will tell us if we are on the right track and if we are headed towards a powerfully predictive theory, or if we are from this goal To be specific, what I mean by simple or minimal is

Inflation: What to do? Einstein 1917 Inflation: What to do? Determine if “simple”, “minimal” inflation explains our universe: flatness nearly scale-invariant spectrum adiabaticity gaussianity spectral tilt (ns ~ 0.95) gravitational waves (T/S ~ 20-30%) ? CMB Anisotropy & LSS It is simple or minimal models of inflation that unequivocally produce a set of six predictions that are observationally testable. RECITE. So far, this class is doing well. This is the reason why I am enthusiastic about inflation. ? ? ? CMB Pol

Density Fluctuation amplitude With N ~ 60 e-folds to go in Planck units energy scale for inflation: With N~60 e-folds to go, These last quantitative conditions spring forth straightforward from the derivation of density perturbations. I will save you that calculation except for the last step. tilt:

Based on M.Tegmark, et al, astro-ph/030173 x

POL

from U. Seljak & M. Zaldarriaga

The Degeneracy Problem G-waves & The Degeneracy Problem Boyle, PJS

The Degeneracy Problem G-waves & The Degeneracy Problem Boyle, PJS

The Degeneracy Problem G-waves & The Degeneracy Problem Boyle, PJS

What if one or more tests fail ? x

? Inflation “Non-Minimal” Inflation? flatness nearly scale-invariant spectrum adiabaticity gaussianity spectral tilt (ns ~ 0.95) gravitational waves (T/S ~ 20-30%) I have been asked to address my remarks to the issues of the very early universe and the origin of the large scale properties of the universe. Why is the universe nearly homogeneous, isotropic and flat? Where did the density perturbations come from? Here it is pretty clear what is needed observationally to make progress.

Cyclic Model Einstein Alternative ? “bang” radiation matter 1917 Alternative ? “branes” Cyclic Model “bang” radiation matter dark energy “contraction” “crunch” They will be BLAH. That is because it is these measurements that will best determine the missing parts of the stor at present. Y Superstring theory

Cyclic Model V Y Y Like simple inflation, characterized by M, w “branes” Like simple inflation, characterized by M, w V Y Y

w < -1/3: homogeneity, isotropy, flatness INFLATION w < -1/3: homogeneity, isotropy, flatness

w < -1/3: homogeneity, isotropy, flatness INFLATION w < -1/3: homogeneity, isotropy, flatness 3(1+w) < 2

w > 1: homogeneity, isotropy, flatness CYCLIC w > 1: homogeneity, isotropy, flatness contraction

w > 1: homogeneity, isotropy, flatness CYCLIC w > 1: homogeneity, isotropy, flatness contraction w > 1 (1+w)

scale-invariant perturbations approach: quantum fluct. exit horizon & re-enter later expanding contracting “dual” e  1/ e e << 1 e >> 1 (or w >> 1) Another Degeneracy Problem !

From L. Boyle, PJS, N. Turok, astro-ph/0310533 POL

Cyclic Inflation Gravitational Waves Very Blue Slightly Red Small to Moderate Non-gaussianity Never Cyclic model based on 3 ideas: bang is a transition; evolution is periodic going Non-adiabaticity Never Some models

Beyond Einstein What does this pattern represent?