Exploring the String Landscape: The Dynamics, Statistics, and Cosmology of Parallel Worlds Stein Pontus Ahlqvist Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2013 c 2012 Stein Pontus Ahlqvist All rights reserved ABSTRACT Exploring the String Landscape: The Dynamics, Statistics, and Cosmology of Parallel Worlds Stein Pontus Ahlqvist This dissertation explores various facets of the low-energy solutions in string theory known as the string landscape. Three separate questions are addressed – the tunneling dynamics between these vacua, the statistics of their location in moduli space, and the potential real- ization of slow-roll inflation in the flux potentials generated in string theory. We find that the tunneling transitions that occur between a certain class of supersymmetric vacua related to each other via monodromies around the conifold point are sensitive to the details of warping in the near-conifold regime. We also study the impact of warping on the distribution of vacua near the conifold and determine that while previous work has concluded that the conifold point acts as an accumulation point for vacua, warping highly dilutes the distribution in pre- cisely this regime. Finally we investigate a novel form of inflation dubbed spiral inflation to see if it can be realized near the conifold point. We conclude that for our particular models, spiral inflation seems to rely on a de Sitter-like vacuum energy. As a result, whenever spiral inflation is realized, the inflation is actually driven by a vacuum energy. Contents Introduction 1 1 Background 3 1.1 Extra Dimensions in String Theory . 3 1.1.1 Calabi-Yau Manifolds . 4 1.1.2 Moduli Space of Calabi-Yau Manifolds . 9 1.2 The Type II Superstring . 24 1.2.1 The Open String . 25 1.2.2 The Closed String . 26 1.2.3 Type IIB Supergravity . 28 1.3 Flux Compactification . 30 1.3.1 No-Go Theorem . 31 1.3.2 Adding Local Sources . 33 1.3.3 Tadpole Condition . 34 1.3.4 Four Dimensional Physics . 36 1.3.5 Warping Correction to The Kähler Metric . 39 1.3.6 The Conifold Geometry . 41 1.3.7 Branes and Fluxes on the Conifold . 48 1.3.8 Warping on the Conifold . 51 1.3.9 Warped Kähler Metric on the Deformed Conifold . 53 i 1.4 Tunneling in Quantum Field Theory . 56 1.4.1 Thin Wall Approximation . 58 1.5 Numerical Techniques . 61 1.5.1 The Shooting Method . 62 1.5.2 The Relaxation Method . 64 2 Conifolds and Tunneling in the String Landscape 70 2.1 Introduction . 70 2.2 Flux Compactification of One Parameter Models . 71 2.2.1 The Superpotential, Kähler Potential, and Scalar Potential . 71 2.2.2 Picard-Fuchs Equations . 76 2.2.3 Numerical Computation of Periods . 79 2.3 Near-Conifold Potential and Numerical Data . 81 2.3.1 The Kähler Potential and its Derivatives . 82 2.3.2 The Superpotential and its Derivatives . 83 2.3.3 The Flux Potential Near the Conifold . 84 2.3.4 Mirror Quintic Near-Conifold Numerical Data . 84 2.4 Finding Vacua . 86 2.5 Numerical Conifunneling . 87 2.5.1 Equations of Motion and Setup . 88 2.5.2 Relaxation in the Bulk . 92 2.5.3 Results from Relaxation in the Vicinity of the Conifold Point . 95 2.6 The Physics of Conifunneling . 98 2.6.1 Geometric Interpretation . 98 2.6.2 The Shortest Path . 102 2.7 Discussion . 104 ii 3 Warped Vacuum Statistics 106 3.1 Introduction . 106 3.2 Background . 107 3.3 Analytical Distributions . 108 3.3.1 Counting the Vacua . 108 3.3.2 Incorporating Warping . 123 3.3.3 Finite Fluxes . 127 3.4 Numerical Vacuum Statistics . 137 3.4.1 Unwarped Analysis . 138 3.4.2 Warped Analysis . 140 3.4.3 Monte-Carlo Vacua . 141 3.5 Discussion . 143 4 Exploring Spiral Inflation in String Theory 147 4.1 Introduction . 147 4.2 Spiral Inflation . 148 4.2.1 Slow-Roll Conditions for Multiple Fields . 148 4.2.2 Spiral Trajectories and the Global Properties of the Potential . 150 4.3 Potentials in String Theory . 153 4.3.1 Near Conifold Form of the Metric and Potential . 155 4.4 Spiraling in String Theory . 159 4.4.1 Spiral Inflation Versus de Sitter Space . 160 4.5 Numerical Simulations . 163 4.5.1 Initial Conditions . 165 4.5.2 Duration of Spiral Inflation . 166 4.6 Discussion . 167 Concluding Remarks 170 iii List of Figures 1.1 Cycles of a genus two surface . 21 1.2 An example of a potential with two non-degenerate minima. 57 1.3 The bounce for the Euclidean (inverted) potential . 58 1.4 Interpolating soliton . 60 1.5 Example of undershooting and overshooting . 62 1.6 Example results of the relaxation method . 66 1.7 Relaxation method near a singular point . 68 1.8 Hard wall modification of the relaxation method . 69 2.1 Results from relaxation method in the bulk. 94 2.2 Relaxation in the bulk superimposed on the potential. 94 2.3 Relaxation near the conifold point. 95 2.4 Relaxation near the conifold point for the axio-dilaton. 96 2.5 Relaxation near the conifold superimposed on potential. 97 2.6 Contributions to the tension from various sources. 99 2.7 Geometrical perspective of conifunneling. 101 2.8 Brane nucleation in conifunneling . 101 3.1 Regions of integration . 145 3.2 Numerical versus analytical distribution . 146 4.1 Near conifold potential . 163 iv 4.2 Spiral potential that does not rely on vacuum energy . 164 4.3 Solutions to the initial conditions for spiral inflation . 165 4.4 Evolution of the spiral condition . 167 4.5 Number of e-foldings for different angular momenta . 168 4.6 Spiral inflation versus vacuum energy . 169 v ACKNOWLEDGMENTS Over the last five years, I have had the pleasure to interact with many wonderful people and am grateful to many of them for their insights, support, and company. First and foremost, I would like to thank my wonderful wife Sheana who has been the most inspiring, thoughtful, and supportive friend I could have ever asked for. I also want to thank my adviser Brian Greene for helping me understand and, perhaps more importantly, appreciate physics. I also want to extend my appreciation to my defense committee for their patience and flexibility as well as their feedback and insights. I also want to thank David Kagan who has been incredibly generous with his time and help and with whom it has been a great pleasure working. I also want to thank Subir Sabharwal, Yonah Lemonik, Arthur Franke, Gary Cheng, Stefanos Marnerides, and Kurt Hinterbichler who besides being great friends have all made learning physics a pleasure. Last, but certainly not least, I want to thank my parents Stein-Göran and Hélène Ahlqvist, as well as my sisters Gabriella Ahlqvist and Alexandra Schönning for their endless love and support. vi DEDICATIONS To Sheana, Mom, and Dad vii 1 Introduction It has been a fundamental and largely unquestioned assumption in physics until the mid 20th century that the constituents of nature are point-like. While it may not seem like a radical idea, introducing extended objects such as strings into physics has given birth to an entire subfield of mathematical physics known as string theory. By simply requiring a quantum mechanical fundamental string to propagate in a Lorentz invariant way one can show that Einstein’s equations of general relativity must be satisfied. What may be even more impressive is that one can also show that consistency can only be achieved in a specific space-time dimension. So, while other theories of physics can be consistently formulated in arbitrary dimensions, string theory requires there to be precisely ten dimensions.1 Clearly, we only experience four such dimensions at low energy so it becomes crucial to understand what happens to the additional six. The most well-studied approach is to compactify the additional dimensions on an internal manifold leaving only four large dimensions. Ideally, one would like to make predictions on how the dynamics of string theory affects low-energy physics in four dimensions. Here we currently reach a roadblock. As it turns out there are many consistent low-energy solutions of string theory, and currently it is not know which, if any, corresponds to our observable universe. This landscape of string theory is in many ways one of the major challenges of modern string theory mainly due to its vast size and computational complexity2. A heuristic argument based on counting the number of 1Interestingly, the fact that this calculation should even yield an integer is not clear at the outset. 2There is actually also a landscape in quantum field theory. See the concluding remarks for a brief discussion of this. 2 inequivalent flux compactifications for a generic Calabi-Yau manifold shows that there may be as many as 10500 distinct solutions, clearly too many to sort through one-by-one. Clearly it is of great importance to understand the structure of this landscape which is what we presently attempt. We begin this dissertation with a review of the required background material. This includes Calabi-Yau manifolds and their associated moduli spaces, an in-depth discussion on warping in the deformed conifold geometry for type IIB supergravity, as well as a brief review of tunneling in quantum field theory and the numerical techniques that are useful in finding these tunneling solutions. In chapter 2 we focus on understanding the tunneling dynamics in the string landscape.