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Testing String Theory with Cosmological Observations? String Cosmology R. Branden- berger Testing String Theory with Cosmological Inflation Motivation Observations? Inflation Problems CAP-CRM Prize Lecture Message String gas Principles Features Robert Brandenberger Structure Perturbations McGill University Analysis Conclusions June 15, 2012 1 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 Thanks to: String Cosmology R. Branden- berger Klaus Hepp (ETH Zürich) Inflation Konrad Osterwalder (ETH Zürich) Motivation Inflation Arthur Jaffe (Harvard) Problems Message Jennie Traschen String gas Principles Raul Bott, Sidney Coleman (Harvard) Features Structure Bill Press, Doug Eardley (Harvard) Perturbations Analysis Neil Turok, Andy Albrecht Conclusions Anne-Christine Davis (DAMTP), Slava Mukhanov (LMU), Cumrun Vafa (Harvard), Xinmin Zhang (IHEP Beijing) 2 / 40 String Cosmology R. Branden- Hume Feldman, Leandros Perivolaropoulos, Jong berger Kung, Jinwu Ye, Tomislav Prokopec, Andrew Inflation Sornborger, Richhild Moessner, Mark Trodden, Raul Motivation Inflation Abramo, Matthew Parry, Martin Götz, Stephon Problems Message Alexander, Damien Easson, Antonio Guimaraes, Zeeya String gas Merali, Ghazal Geshnizjani, Scott Watson, Thorsten Principles Features Battefeld. Structure Perturbations Subodh Patil, Natalia Shuhmaher, Patrick Martineau, Analysis Rebecca Danos, Nima Lashkari, Andrew Stewart, Conclusions Francis Cyr-Racine, Jean Lachapelle, Johanna Karouby, Wei Xue, Laurence Perreault-Levasseur My colleagues at McGill 3 / 40 String Cosmology R. Branden- Hume Feldman, Leandros Perivolaropoulos, Jong berger Kung, Jinwu Ye, Tomislav Prokopec, Andrew Inflation Sornborger, Richhild Moessner, Mark Trodden, Raul Motivation Inflation Abramo, Matthew Parry, Martin Götz, Stephon Problems Message Alexander, Damien Easson, Antonio Guimaraes, Zeeya String gas Merali, Ghazal Geshnizjani, Scott Watson, Thorsten Principles Features Battefeld. Structure Perturbations Subodh Patil, Natalia Shuhmaher, Patrick Martineau, Analysis Rebecca Danos, Nima Lashkari, Andrew Stewart, Conclusions Francis Cyr-Racine, Jean Lachapelle, Johanna Karouby, Wei Xue, Laurence Perreault-Levasseur My colleagues at McGill 3 / 40 Main Messages String Cosmology R. Branden- berger Inflation Motivation Inflation There are alternatives to inflationary cosmology. Problems Message String Theory leads to a new paradigm for early String gas Principles universe cosmology. Features String Theory can be tested with cosmological Structure Perturbations observations. Analysis Conclusions 4 / 40 Outline String Cosmology 1 Inflation: Current Paradigm of Early Universe Cosmology R. Branden- berger Motivation Review of Inflationary Cosmology Inflation Motivation Problems of Inflationary Cosmology Inflation Problems Message Message String gas 2 String Gas Cosmology Principles Features Principles Structure Features of String Gas Cosmology Perturbations Analysis Conclusions 3 String Gas Cosmology and Structure Formation Review of the Theory of Cosmological Perturbations Analysis 4 Conclusions 5 / 40 Plan String Cosmology 1 Inflation: Current Paradigm of Early Universe Cosmology R. Branden- berger Motivation Review of Inflationary Cosmology Inflation Motivation Problems of Inflationary Cosmology Inflation Problems Message Message String gas 2 String Gas Cosmology Principles Features Principles Structure Features of String Gas Cosmology Perturbations Analysis Conclusions 3 String Gas Cosmology and Structure Formation Review of the Theory of Cosmological Perturbations Analysis 4 Conclusions 6 / 40 Current Paradigm for Early Universe Cosmology String Cosmology R. Branden- berger The Inflationary Universe Scenario is the current paradigm Inflation of early universe cosmology. Motivation Inflation Successes: Problems Message Solves horizon problem String gas Principles Solves flatness problem Features Structure Solves size/entropy problem Perturbations Analysis Provides a causal mechanism of generating primordial Conclusions cosmological perturbations (Chibisov & Mukhanov, 1981). 7 / 40 Current Paradigm for Early Universe Cosmology String Cosmology R. Branden- berger The Inflationary Universe Scenario is the current paradigm Inflation of early universe cosmology. Motivation Inflation Successes: Problems Message Solves horizon problem String gas Principles Solves flatness problem Features Structure Solves size/entropy problem Perturbations Analysis Provides a causal mechanism of generating primordial Conclusions cosmological perturbations (Chibisov & Mukhanov, 1981). 7 / 40 String Cosmology R. Branden- berger Inflation Motivation Inflation Problems Message String gas Principles Features Structure Perturbations Analysis Conclusions Credit: NASA/WMAP Science Team 8 / 40 String Cosmology R. Branden- berger Inflation Motivation Inflation Problems Message String gas Principles Features Structure Perturbations Analysis Conclusions Credit: NASA/WMAP Science Team 9 / 40 Challenges for the Current Paradigm String Cosmology R. Branden- berger In spite of the phenomenological successes, current Inflation realizations of the inflationary scenario suffer from Motivation Inflation several conceptual problems. Problems Message In light of these problems we need to look for input from String gas new fundamental physics to construct a new theory Principles Features which will overcome these problems. Structure Perturbations Question: Can Superstring theory lead to a new and Analysis improved paradigm? Conclusions Question: Can this new paradigm be tested in cosmological observations? 10 / 40 Challenges for the Current Paradigm String Cosmology R. Branden- berger In spite of the phenomenological successes, current Inflation realizations of the inflationary scenario suffer from Motivation Inflation several conceptual problems. Problems Message In light of these problems we need to look for input from String gas new fundamental physics to construct a new theory Principles Features which will overcome these problems. Structure Perturbations Question: Can Superstring theory lead to a new and Analysis improved paradigm? Conclusions Question: Can this new paradigm be tested in cosmological observations? 10 / 40 Challenges for the Current Paradigm String Cosmology R. Branden- berger In spite of the phenomenological successes, current Inflation realizations of the inflationary scenario suffer from Motivation Inflation several
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