Selected Topics on the Dark Side by Cosmin Ilie A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Physics) in The University of Michigan 2011 Doctoral Committee: Professor Katherine Freese, Chair Professor Gregory Tarle Assistant Professor David John Baker Assistant Professor Dragan Huterer Assistant Research Scientist Monica Valluri To Raluca ii ACKNOWLEDGEMENTS At this point of finishing my thesis, I can certainly picture numerous people I am in- debted to, and here I should thank them all with my sincere heart. I owe my deepest gratitude to my adviser, Prof. Katherine Freese for her mentoring, teaching, encouragement and support over the years. She set an example of a great scholar and adviser, whose patience and professionalism always motivated me. The depth and breadth of her knowledge are a precious resource and I am fortunate for having first hand access to it. Needles to say, without her guidance and help this dissertation would not have been possible. At times, when I felt discouraged by what seemed like daunting tasks ahead of me, she always knew how to motivate me. And for this I will forever be grateful to her. I would hereby like to thank Prof. David John Baker, Prof. Dragan Huterer, Prof. Gre- gory Tarle and Dr. Monica Valluri for agreeing to be a part of my dissertation committee. I am grateful to Prof. Ratindranath Akhouri and Prof. James Wells for their mentorship and guidance during the early stage of my PhD. A great deal of thanks also goes to the all the people I have closely collaborated with on the various projects included in this thesis. I am indebted to Prof. Thirtabir Biswas, Dr. Doug Spolyar and Dr. Monica Valluri for their invaluable input and insightful comments. I am grateful to Dr. Pat Scott for TLUSTY spectra for Dark Stars and to Prof. Paul Shapiro and Dr. Ilian Iliev for sharing data from simulations of DM haloes. Many thanks go to all faculty in the physics department I had the chance to learn from. I would also like to show my gratitude to all the administrative staff in the Physics Student Services or at the MCTP that have helped me countless times. I have to express my grate- iii fulness to the Weinberg Theory Group at the University of Texas Austin for their hospitality during the Spring of 2011 when part of this dissertation was written. I want to thank Genes Claudiu and Luiza for their support and friendship. In my first few years at Michigan together we were “bridging” an ocean separating us from home. To Bin Wang for his true friendship over the years. Finally, I would like to thank my family. To my parents for being supportive of all the major decisions I took. To my wife, Raluca, for so many reasons I cannot express in words. For always being there for me. She continued to believe in me and was always was able dissipate my deepest fears. Without her presence by my side, without her tremendous love and continuous support, I could never have gone this far. iv TABLE OF CONTENTS DEDICATION ................................... ii ACKNOWLEDGEMENTS ............................ iii LIST OF FIGURES ................................ viii LIST OF TABLES ................................. xv LIST OF APPENDICES .............................. xvii LIST OF ABBREVIATIONS ........................... xviii ABSTRACT ..................................... xx CHAPTER I. Introduction ................................. 1 1.1 TheBigBangscenario ....................... 1 1.1.1 Universepre-BBN .. .. .. .. .. .. 4 1.1.2 Universepost-BBN. 6 1.1.3 LimitationsofstandardBigBangscenario. 9 1.2 ConnectingDarkEnergyandInflation . 12 1.2.1 Inflation.......................... 12 1.2.2 DarkEnergy ....................... 17 1.2.3 Onepossibleconnectingscenario . 19 1.3 DarkMatter ............................. 21 1.3.1 Evidenceofitsexistence . 21 1.3.2 SearchesforDM . .. .. .. .. .. .. 23 1.4 DarkStars .............................. 24 II. Are we seeing the beginnings of Inflation? ................ 29 2.1 PhantomDarkEnergy . 34 2.2 “PartialReheating”andLatetimedeSitterPhase . .... 40 v 2.3 TransitiontoRadiationandCyclicity . 43 2.3.1 PhaseI:Reheating . 44 2.3.2 PhaseII:“Standard”RadiationDomination . 46 2.3.3 Cyclicity ......................... 48 2.4 NumbersandConstraints . 53 2.5 Conclusions ............................. 56 III. Dark Stars and Boosted DM annihilation rates ............. 58 3.1 Introduction ............................. 58 3.1.1 Boosted Leptophilic AnnihilationMotivatedby PAMELA data............................ 59 3.1.2 EffectofConcentrationParameter . 61 3.1.3 CanonicalValues . 62 3.2 EquilibriumStructureoftheDarkStar . 63 3.2.1 InitialConditionsandAccretionRates . 63 3.2.2 BasicEquations. 64 3.2.3 DarkMatterDensities . 66 3.2.4 EnergySources. .. .. .. .. .. .. 69 3.3 Results................................ 72 3.3.1 ‘Final’ Luminosityfor Dark Stars withboostedDM . 73 3.3.2 StructureandEvolutionofDS . 74 3.4 SummaryandConclusions . 93 IV. Supermassive Dark Stars .......................... 95 4.1 Motivation.............................. 95 4.2 StructureandEvolutionoftheDarkStar . 99 4.2.1 BasicEquations. 99 4.2.2 DarkMatterDensities . .101 4.2.3 EnergySources: . .105 4.3 ResultsofStellarStructureAnalysis . 106 4.4 DetectabilitywithJWST. .114 4.5 ConcludingRemarks . .116 V. Observability of Dark Stars with JWST ..................123 5.1 DarkStarSpectra ..........................123 5.2 DarkStarFormationRate . .124 5.3 DarkStarsinHubbleSpaceTelescope . 128 5.3.1 Comparison of DS stellar output with HST Sensitivity . 128 5.3.2 Using HST data to constrain the Numbers of Dark Stars 131 5.4 DarkStarsinJWST . .. .. .. .. .. .. ..135 5.4.1 Detection at z 10 as a J115 banddropout . 137 5.4.2 Detection at z ∼ 12 as a H banddropout . 138 ∼ 150 vi 5.4.3 Detection at z 15 as a K200 dropout . .140 5.5 SMDSvsPopIIIgalaxiesinJWST∼ . .141 5.6 SummaryandConclusions . .145 VI. Conclusions and Future Work .......................158 6.1 Conclusions .............................158 6.2 FutureWork .............................160 APPENDICES ................................... 162 BIBLIOGRAPHY ................................. 179 vii LIST OF FIGURES Figure 1.1 Illustration describing the different expansion phases of the universe. Im- ageCredit:NASA.............................. 2 1.2 WMAP data revealing the contents of the Universe. Note that the energy density of various components is diluted by cosmic expansion at different rates, therefore earlier times would have a completely different energy density budget, as illustrated by the left panel. Image Credit: NASA / WMAPScienceTeam............................ 3 1.3 CMB temperature as measured over the years. In the lower two pictures the color scale is chosen in such a way to magnify the inhomogeneities found. One should remember that they are less than one part in 105. ImageCredit:NASA/WMAPScienceTeam. 8 1.4 Time Line of the Universe: Very shortly after the Big Bang a phase of rapid exponential expansion occurred. The quantum fluctuations were stretched by an enormous factor during that age and they eventually formed the seeds of large scale structures we see today, such as Galaxies, Clus- ters, etc. Those were formed as the universe cooled enough for gravita- tional instabilities to start growing. Approximately 9 billion years ago a new phase of accelerated expansion begun due to DE becoming the dominant component. Image Credit: NASA / WMAP Science Team. ... 9 1.5 Schematic shape of the inflaton potential. Left Panel: This corresponds to the “old inflation” scenario, where at the first the field is trapped in a false vacuum state and tunnels to the true vacuum via bubble nucleation. Right Panel: This would be a generic potential for “chaotic inflation”. 13 viii 1.6 Image of the Abell 1689 cluster as seen by HST. Lensing arcs in the image and the clear distortion of the background (red and blue) galax- ies are an indication of strong gravitational lensing. Credit:NASA, N. Benitez (JHU), T. Broadhurst (Racah Institute of Physics/The Hebrew University), H. Ford (JHU), M. Clampin (STScI),G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team andESA. 22 2.1 Numerical solutionsfor the energy densitiesas we complete a cycle from 1 a deStiter phase back to it. Here we have chosen: ω = 3 , µp =5, µr = .1, 2 m = 10− Mp and we have set Mp to one. Note the six distinct phases: I.A and I.B corresponding to reheating; II.A and II.B corresponding to a radiation dominated universe; III.A and III.B corresponding to the phan- tom and dS phase respectively. In order to make all phases clearly distinct 45 we chose the transition set the minimum energy density at around 10− instead of the realistic meV 4 ........................ 49 3.1 “Final” luminosities(as the Dark Star enters the ZAMS) as a function of Boost factor for the µ-channel and AH4 models examined in Bergstrom et al. (2009). The contour regions are generated using the range of WIMP masses for a fixed boost factor taken from the corresponding 2σ contours in fig. 1 in Bergstrom et al. (2009). The central star-shaped point in the right panel will be taken to be our designated boosted AH4 model and is consistentwithbothFermiandPAMELA. 75 3.2 Luminosity evolution as a function of time for the four cases under con- sideration. The upper left panel displays the only boosted case, the AH4 model, with B = 1500, mχ = 2.35 TeV and c = 3.5. The other pan- els correspond to the unboosted case of a 100 GeV WIMP with σv = 3 1026cm3/s and concentration parameters as labeled. .h