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String Inflation

This article explores the concept of string inflation and its potential benefits in understanding the early universe. It discusses the mechanisms, initial conditions, and reheating processes in string inflation models, as well as the mind-broadening aspect of studying inflation. The text language is English.

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String Inflation

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Presentation Transcript

  1. String Inflation Is it helping? C.P. Burgess

  2. Outline • Helping with what? • Why build models only a mother could love? • What might help look like? • Mechanisms; robustness • Initial conditions; naturalness; • Reheating and scales; signatures; • Mind-broadening;… • A tentative scorecard UniverseNet Lecce 2010

  3. Outline • Helping with what? • Why build models only a mother could love? • What might help look like? • Mechanisms; robustness • Initial conditions; naturalness; • Reheating and scales; signatures; • Mind-broadening;… • A tentative scorecard UniverseNet Lecce 2010

  4. Outline • Helping with what? • Why build models only a mother could love? • What might help look like? • Mechanisms; robustness • Initial conditions; naturalness; • Reheating and scales; signatures; • Mind-broadening;… • A tentative scorecard UniverseNet Lecce 2010

  5. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  6. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  7. Help with what? Observation: horizon and flatness problems (and possibly defect problem) arise because the co-moving Hubble length, H-1/a = (1/aH), grows during the present Hot Big Bang epoch. • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  8. Help with what? Starobinsky; Guth Linde; Albrecht & Steinhardt They would be resolved if H-1/a = (1/aH), were instead to shrink during an earlier epoch. e.g. exponential inflation: a = a0 eHt • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  9. Help with what? Mukhanov, Linde, Hawking, Steinhardt, Guth, Pi,… • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Inflationary Bonus: Simple models provide a good description of primordial fluctuations. UniverseNet Lecce 2010

  10. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  11. Help with what? But…. Simple inflation models require tuned potentials ‘Planck slop’ • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  12. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Tuning: technical naturalness or control of approximations? UniverseNet Lecce 2010

  13. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Technically unnatural: eg the electroweak hierarchy UniverseNet Lecce 2010

  14. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Technically unnatural: eg the electroweak hierarchy UniverseNet Lecce 2010

  15. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Technically unnatural: eg the electroweak hierarchy Must cancel to 20 decimal places!! UniverseNet Lecce 2010

  16. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Technically natural: eg size of atoms vs size of nuclei UniverseNet Lecce 2010

  17. Help with what? ‘t Hooft But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Technically natural: eg size of atoms vs size of nuclei UniverseNet Lecce 2010

  18. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Whether inflationary models are unnatural depends on the particle content at these very high energies. String inflationary models tend to be natural in this sense because of supersymmetry, shift symmetry, extra dims UniverseNet Lecce 2010

  19. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Tunings to 1 part in 100 are not so unnatural, technically. UniverseNet Lecce 2010

  20. Help with what? But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Tuning: the real issue is control of approximations: if a given potential is asserted to inflate within a given set of approximations, have all contributions been included to the required accuracy? UniverseNet Lecce 2010

  21. Help with what? Copeland et al, Kachru, McAllister,…. But…. Simple inflation models require tuned potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Tuning: the real issue is control of approximations: if a given potential is asserted to inflate within a given set of approximations, have all contributions been included to the required accuracy? e.g. Planck slop: UniverseNet Lecce 2010

  22. Help with what? But…. Simple inflation models require tuned potentials Are predictions of simple models robust? e.g. • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  23. Help with what? But…. Simple inflation models require tuned potentials Are predictions of simple models robust? Sometimes special initial conditions required • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  24. Help with what? But…. Simple inflation models require tuned potentials Are predictions of simple models robust? Sometimes special initial conditions required How does reheating work, and what are the degrees of freedom that are relevant? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  25. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? String Theory: Best explored, and possibly the only, quantum theory of gravity at small distances UniverseNet Lecce 2010

  26. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? String Theory: Best explored, and possibly the only, quantum theory of gravity at small distances First known theory that could be the theory of everything UniverseNet Lecce 2010

  27. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? But…. How to make contact with experiment given that Ms is likely very large? UniverseNet Lecce 2010

  28. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? But…. How to make contact with experiment given that Ms is likely very large? How does one make falsifiable predictions with enormous number of vacua? UniverseNet Lecce 2010

  29. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Inflation: impressive phenomenology seeking a fundamental theory within which to sit; String Theory: an impressive fundamental theory seeking experimental consequences to test UniverseNet Lecce 2010

  30. Help with what? courtesy of Rocky Kolb • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  31. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  32. Help with what? What we’d like string theory to tell us about inflation: How generic is it in the landscape? Initial conditions, flat potentials, … • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  33. Help with what? What we’d like string theory to tell us about inflation: How generic is it in the landscape? Initial conditions, flat potentials, … How does reheating work? Does SM couple strongly enough to inflaton? Do other channels couple even more strongly? • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  34. Help with what? What we’d like string theory to tell us about inflation: How generic is it in the landscape? Initial conditions, flat potentials, … How does reheating work? Does SM couple strongly enough to inflaton? Do other channels couple even more strongly? What are the other dimensions doing? • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  35. Help with what? What we’d like string theory to tell us about inflation: How generic is it in the landscape? Initial conditions, flat potentials, … How does reheating work? Does SM couple strongly enough to inflaton? Do other channels couple even more strongly? What are the other dimensions doing? How robust are inflationary inferences drawn using simple single-field slow-roll models? • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  36. Help with what? What we’d like string theory to tell us about inflation: How generic is it in the landscape? Initial conditions, flat potentials, … How does reheating work? Does SM couple strongly enough to inflaton? Do other channels couple even more strongly? What are the other dimensions doing? How robust are inflationary inferences drawn using simple single-field slow-roll models? Are qualitatively new kinds of signatures or mechanisms possible? • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  37. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  38. Help with what? What we’d like inflation to tell us about string theory: Predicting in the landscape: perhaps some features of present-day universe correlate with its earlier history • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  39. Help with what? What we’d like inflation to tell us about string theory: Predicting in the landscape: perhaps some features of present-day universe correlate with its earlier history. Inflationary mechanisms can be among other low-energy modules that guide the search for realistic vacua among the many string solutions. • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  40. Help with what? What we’d like inflation to tell us about string theory: Predicting in the landscape: perhaps some features of present-day universe correlate with its earlier history. Inflationary mechanisms can be among other low-energy modules that guide the search for realistic vacua among the many string solutions. Can hope to learn about time-dependent solutions and non-supersymmetric parts of the landscape. • What needs fixing? • about strings • about inflation • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  41. Help with what? • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  42. Help with what? What is so hard about finding inflation in string theory? It has many 4D scalars. (brane positions; or moduli) • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  43. Help with what? What is so hard about finding inflation in string theory? It has many 4D scalars; supersymmetry can give these very flat potentials • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  44. Help with what? Brustein & Steinhardt What is so hard about finding inflation in string theory? It has many 4D scalars; supersymmetry can give these very flat potentials; BUT: a convincing case for inflation requires reliably knowing the potential that stabilizes moduli • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  45. Help with what? Giddings, Kachru & Polchinski Kachru, Kallosh, Linde & Trivedi It has recently become possible to compute the low-energy potential for all moduli for some string constructions • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? UniverseNet Lecce 2010

  46. Help with what? Giddings, Kachru & Polchinski Kachru, Kallosh, Linde & Trivedi It has recently become possible to compute the low-energy potential for all moduli for some string constructions: First done for Type IIB vacua • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Key ingredients: D3 and D7 branes & orientifolds Fluxes sourced by these branes, wrapping extra dimensions UniverseNet Lecce 2010

  47. Help with what? Giddings, Kachru & Polchinski It has recently become possible to compute the low-energy potential for all moduli for some string constructions: First done for Type IIB vacua • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? At low energies: a 4D no-scale sugra: for moduli Ti=ti + i bi UniverseNet Lecce 2010

  48. Help with what? Klebanov & Strassler • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Strongly warped throats arise in response to specific flux configurations. Warped throats strongly redshift energies à la Randall & Sundrum UniverseNet Lecce 2010

  49. Help with what? Kachru, Kallosh, Linde & Trivedi Denef & Douglas Use other means (wrapped ED3, gaugino condensation) to stabilize remaining moduli • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? KKLT regime believe approximations if UniverseNet Lecce 2010

  50. Help with what? Balasubramanian, Bergland, Conlon, Quevedo Use other means (wrapped ED3, gaugino condensation) to stabilize remaining moduli • What needs fixing? • about inflation • about strings • What might one hope to learn? • about inflation • about strings • Why now? Large-volume regime: for W0 ~ O(1) can believe approximations if UniverseNet Lecce 2010

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