Inflation and Fundamental Physics What do cosmological measurements say about the very early universe? C.P. Burgess Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.   Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion. Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience. with M. Cicoli, M.Gomez-Reino,G.Tasinato, F.Quevedo and I.Zavala

Outline Inflation String inflation Why is it so widely believed to have happened? What can we expect to learn? String inflation Why build models only a mother could love? UniverseNet Inflation

Outline Inflation String inflation Why is it so widely believed to have happened? What can we expect to learn? String inflation Why build models only a mother could love? UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? WMAP Concordance cosmology provides a great description of the wealth of cosmological data. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? NCSA simulation Evidence supports the picture that structure forms from the collapse of an initially uniform distribution. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Radiation domination: Matter domination: Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Initially very homogeneous Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Initially very homogeneous Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? fluctuations freeze once larger than H-1, so the problem is while so the product aH decreases with t Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? fluctuations freeze once larger than H-1, so the problem is while so the product aH decreases with t Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum eg: if the universe bounced UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum but: how do you get a bounce? UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum or: if the expansion accelerated UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum require aH to grow by ~ e60 UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum but: why should it start? Or end? UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? courtesy A. Linde Concordance model works well, if the universe starts off in just the right way: Initially very flat: Initially very homogeneous: surprise given speed of expansion seem to be no primordial defects Who says it took place? What might one hope to learn if so? Possible solution: extrapolation into the past is wrong Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum and must it end everywhere? UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? A. Guth Archetype: if p = - r then Friedmann eq implies much like dark energy (but with a larger H) Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? A. Guth; A. Linde; A. Albrecht & P. Steinhardt How to achieve p = - r ? For a single homogeneous scalar field so homogeneous slow roll can make things work Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Lyth So Hubble scale is approximately constant provided are small Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? For example V = (1/2) m2 f2 (large-field model) then positive and ~ e are small for large f. (Must then have m not too large.) Also, inflation ends as f is driven to smaller values. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Large-field variation V = V0 – A exp (-l f) then negative and >> e are small for large f (and V is bounded in this region) Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? For example V = V0 - (1/2) m2 f2 then negative, bigger than e are small for small f and m . Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Mukhanov; Hawking; Linde; Guth & Pi; Steinhardt; … Bonus: besides providing a framework within which primordial seeds of CMB fluctuations can be explained, inflation also provides a mechanism: primordial quantum fluctuations. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? CMB and large-scale structure sample density correlations Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Separating primordial from late-time fluctuations primordial part transfer function Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Separating primordial from late-time fluctuations Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Structure growth requires k/a > H and the universe is matter dominated. k-4 suppression because modes with k/a = H during rad. dom. must await mat. dom. UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Evidence is that primordial fluctuations are simple with index and As chosen to ensure Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? ns = 1 is special (Harrison-Zeldovich) d T/T tracks Newtonian potential so with then is scale invariant if ns = 1. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Mukhanov; Hawking; Linde; Guth & Pi; Steinhardt; … What is predicted by single-field models? Must propagate initial d f at horizon exit to determine d F at late times, but why should d f be nonzero? Although classical fluctuations are damped during inflation, they are replenished by quantum fluctuations so d f ~ H/2p Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Can compute linear fluctuations in inflaton and metric and evolve forward using quantum fluctuations as the initial condition at horizon exit. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Tensor modes evolve independently. Scalar mixes with Newtonian potential by an amount controlled by df/dt UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Mukhanov For single field there is a simple integral for modes with k/a < H Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Primordial fluctuations can be robustly evolved when outside the Hubble scale UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? For two regions with F approximately constant Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Ff varies inversely with e if initial region is inflating. UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? In this way one finds standard single-field formulae Scalar perturbations Tensor perturbations Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum In principle 3 parameters (H, e, h) give 4 observables. UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? In this way one finds standard single-field formulae Scalar perturbations Tensor perturbations Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Conventional to define r = QT/QF (= 16 e = -8 nT.) UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? In this way one finds standard single-field formulae Scalar perturbations Tensor perturbations Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum Conventional to define r = QT/QF (= 16 e = -8 nT.) UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? In particular, d T/ T ~ 10-5 implies Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum So if e and h are similar in size then V should be very large relative to other particle physics scales. (Measurement of tensor modes would remove the assumption that e and h are similar Also, large-field models tend to give larger tensor modes UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? The good news: Predictive* and good agreement with observations: Close to HZ spectrum (precisely constant H gives scale invariant result) Gaussian fluctuations (ie <f f f f> not independent of <f f>) because slow roll implies weak inflaton self-couplings Evolution to present relatively model-independent Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum and possibly more if tensor fluctuations are obseved UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? *Less predictive with more complicated models eg: Additional scalar fields: Should there be other light fields besides the inflaton during inflation then there are more than 3 parameters and predictions can change. In particular, z is no longer conserved, so can obtain more complicated post-inflationary evolution. (Can also remain simple, such as if in thermal equilibrium.) Interactions can be stronger, so can obtain observable non-gaussianity. Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Linde *Less predictive with more complicated models eg: Additional scalar fields: Should there be other light fields besides the inflaton during inflation then more than 3 parameters and predictions can change. In particular, interactions can be stronger and z is no longer conserved, so can obtain observable non-gaussianity. Who says it took place? What might one hope to learn if so? For example: hybrid inflation Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? The bad news: Homogeneous slow roll is usually not generic, and can be sensitive to initial conditions; Very flat potentials have naturalness problems, and inflationary potentials are so flat they are sensitive to ‘planck slop’ (Mp suppressed interactions); Reheating not understood Predictions possible at all? (transplackia, multiverse) Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? Much of the bad news depends on the details of physics at the large energies relevant to the inflationary epoch: Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum If the inflationary scale is so close to the gravity scale, won’t all of the new degrees of freedom at this scale completely change the picture? UniverseNet Inflation

Inflation Who says it took place? What might one hope to learn if so? The bottom line (part I): The great success of standard cosmology relies on relatively special initial conditions Very simple single-field inflationary models provide a simple description of these initial conditions Cosmological measurements provide limited information about very high energy physics Successful cosmologies rely on features that are unusual for physical theories (flat scalar potentials): what does this tell us? Who says it took place? What might one hope to learn if so? Start with the picture of how scales evolve during and after inflation; Describe the inflaton-metric system in its original and Mukhanov form; Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum UniverseNet Inflation

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