DOCSLIB.ORG

Cosmological Anomalies Shed Light on the Dark Sector

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cosmological Anomalies Shed Light on the Dark Sector COSMOLOGICAL ANOMALIES SHED LIGHT ON THE DARK SECTOR by Tanvi Karwal A dissertation submitted to The Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy. Baltimore, Maryland June, 2019 c 2019 Tanvi Karwal ⃝ All rights reserved Abstract Little is known about dark energy and dark matter; but their simple descriptions in the ΛCDM model of cosmology fit numerous datasets well. Recently however, tensions have emerged between the results of different datasets, as have certain unex- pected results. These anomalies may indicate new physics beyond ΛCDM; a revision of how we describe the dark sector. My work uses cosmological anomalies to explore the dark sector. My research resolves perhaps the most exciting tension in cosmology, the Hubble tension, with early dark energy (EDE). I developed two physical models for EDE and find that these models not only solve the Hubble tension, but also fit mostcosmolog- ical datasets well. No other solution to the Hubble tension proposed thus far can do both - fully solve the tension while still fitting early and late-time measurements of the Universe. The model that succeeds ΛCDM should solve not only the Hubble tension but ii ABSTRACT also other cosmological tensions such as the S8 anomaly. My research investigates a decaying dark matter model to address both tensions simultaneously but finds the constraints from late-universe observations too stringent to permit a full resolution. I am also building a phenomenological tool to model the dark sector in a widely- used cosmological code. This tool, generalised dark matter, is a powerful formalism capable of emulating the effects of a wide variety of dark matter and dark energy models, simplifying placing constraints on different fundamentally-motivated models. The formalism and two immediate applications of it are discussed. My work also shows that a curious cosmic-ray (CR) measurement likely has an astrophysical explanation rather than one motivated by dark matter. More flux in CR positrons is observed at high energies than expected, indicating new sources for high-energy CR positrons. My work demonstrates that nearby pulsars could source these positrons and it develops a new analysis technique to distinguish dark matter and pulsar sources for CR data. The aforementioned anomalies and many others have persisted in cosmology for years. It may be time to look beyond the standard model of cosmology for new physics and new descriptions of the dark sector. iii ABSTRACT Readers Marc Kamionkowski (Primary Advisor) Adam Riess Petar Maksimovic Sabine Stanley Susan Kassin iv Acknowledgments Science is not accomplished in isolation and I am grateful for the encouragement and guidance I have received from many. I am infinitely grateful to my advisor Marc Kamionkowski. Your advising is largely responsible for moulding me into the researcher I am today. Hopefully, we can agree that that is a compliment. Thank you for being kind and understanding, even when you have to remind me how old the Earth is. Besides striving to be as brilliant as you, I also aspire to be as unperturbed as you. I am extremely grateful for your support, presenting me with every opportunity for growth and of course, your endless anecdotes. I hope to return as a collaborator someday. My closest collaborators Tristan Smith, Vivian Poulin and `academic uncle' Ilias Cholis, I have learnt more from you than you tried to teach me. Thank you for trusting my scientific judgement as well as pointing out its fallacies. We have accomplished some spectacular science together and I look forward to more science to come. v ACKNOWLEDGMENTS I am grateful also to others who mentored me, whether knowingly or not. Julian Mu~noz,Patrick Breysse, Ibou Bah and Kim Boddy, you are magnanimous scientists and I deeply appreciate the time you spent on me when you had no obligation to. Kim, I want to grow up to be you. Roller-coasters are more fun when you have people to scream with, and I am grateful for the many graduate students I shared this ride with. In particular, Dan Pfeffer, Kim Berghaus and Kirsten Hall, you are my cornerstones. Dan, I relyonyou far more than I care to admit, you are a bouncy-castle of support. Kim, thank you for telling me to solve my problems. You have weird approaches to motivational speeches, but they work wonderfully. Kirsten, I found a soul-sister in you and I appreciate your calming and validating words, as well as your love of art and cake. You guys give me the warm-and-fuzzies. On a similar note, thank you Kelley Key for keeping all us graduate students in check and always having zombie-movie recommendations for me. I felt truly taken care of at this department, in large part thanks to you. I must also thank Naitri Jadeja, mostly because she forced me to by interminably whining, but also because she kept me sane during the many years of graduate school. Finally, I thank my walking birthplace Anita Karwal, the previous tenant and book-thief Janvi Karwal, and black-belt embarrasser Atul Karwal. You guys make me believe I can do anything. vi Dedication To my loving parents and sister. I wrote a PhD thesis just to cure your insomnia. vii Contents Abstract ii Acknowledgments v List of Tables xii List of Figures xiii 1 Introduction 1 2 The Hubble Tension 10 2.1 Early Dark Energy at the Background Level . 12 2.1.1 Model . 13 2.1.2 Method . 18 Fisher Matrices . 19 Planck Data . 22 2.1.3 Constraints on the EDE . 24 Fixing τ = τPl .............................. 25 Fixing τ = τPl + 2στ;Pl .......................... 26 viii CONTENTS Fixing τ = τPl + 5στ;Pl .......................... 29 2.1.4 Conclusions . 29 2.2 Ultra-Light Axion-like Fields as Early Dark Energy . 37 2.2.1 The cosmological dynamics of ULAs . 40 Background dynamics . 40 Perturbed dynamics in the fluid formalism . 43 Initial conditions of perturbations . 44 2.2.2 Current constraints to ULAs . 46 2.2.3 Implications for cosmological tensions . 49 The Hubble tension . 49 EDGES exotic 21 cm measurement . 53 2.2.4 Conclusions . 56 2.3 A Resolution of the Hubble Tension with Early Dark Energy . 57 3 Combining Cosmological Tensions 70 3.1 Decaying dark matter model . 73 3.1.1 Background dynamics . 74 3.1.2 Calculation of ∆Neff ........................... 76 3.1.3 Effects on observables . 77 3.2 Methodology . 80 3.3 Results . 81 3.4 Discussion and conclusions . 89 4 Generalised Dark Matter 92 ix CONTENTS 4.1 GDM Dynamics . 94 4.1.1 Background dynamics . 94 4.1.2 Perturbation evolution . 94 4.1.3 Effect on the CMB . 95 4.2 Applications of the GDM formalism . 100 4.2.1 Principal component analysis with GDM . 100 4.2.2 The CMB low multipole tension . 101 5 The Cosmic-Ray Positron Excess 103 5.1 The CR positron excess and possible explanations . 104 5.2 The pulsar explanation of the CR positron excess . 106 5.2.1 Data . 108 5.2.2 Astrophysical uncertainties surrounding the pulsar explanation . 108 Neutron star birth distribution . 109 Neutron star spin-down distribution properties . 112 Injection properties of CR positrons . 115 CR propagation through the ISM and heliosphere . 119 Pulsar simulations . 120 5.2.3 Differentiating pulsars and dark matter with CRs . 122 Power-spectrum analysis of the CR positron spectrum . 122 Results . 124 Projections for future data . 126 5.3 Conclusions . 128 x CONTENTS Bibliography 131 Vita 166 xi List of Tables 2.1 Fiducial values of ΛCDM parameters used in the Fisher-matrix analysis . 24 2.2 The best-fit χ2-values per experiment for various cosmologies . 68 2.3 Best-fit parameter values for various cosmologies . 69 3.1 Priors on MCMC parameters . 82 3.2 Best-fit parameter values for ΛCDM and DDM for various datasets . 88 3.3 The best-fit χ2-values per experiment for ΛCDM and DDM . 89 5.1 Spin-down power distribution properties for pulsar simulations . 116 5.2 CR propagation model parameters . 120 5.3 Potential to observe features in the CR e+ spectrum for various experiments 128 xii List of Figures 2.1 Background evolution of early dark energy . 15 2.2 Shifts in the CMB TT spectrum due to EDE . 17 2.3 Partial derivatives of the TT power spectrum with respect to ΛCDM and EDE parameters . 21 2.4 Results for EDE and the Hubble parameter fixing τ = τPl .......... 27 2.5 Results for EDE and the Hubble parameter fixing τ = τPl + 2στ;Pl ..... 28 2.6 Results for EDE and the Hubble parameter fixing τ = τPl + 5στ;Pl ..... 30 2.7 Correlations between the Hubble parameter and EDE for various zc .... 31 2.8 The best-fit CMB TT spectra for ΛCDM and ΛCDM+EDE models . 33 2.9 The maximum allowed fractional energy density in EDE . 35 2.10 Background evolution of the ULA EDE . 42 2.11 Cosmological constraints on the density of ULA EDE today . 47 2.12 Posteriors for ULA EDE and ΛCDM parameters . 48 2.13 Effect of ULA EDE on the Hubble parameter . 52 2.14 Effect of ULA EDE on the EDGES tension . 54 xiii LIST OF FIGURES 2.15 Posteriors for ΛCDM and EDE cosmologies showing the EDE solution to the Hubble tension . 61 2.16 Variation of physical scales due to EDE . 62 2.17 CMB TT residuals of the EDE cosmology compared to ΛCDM . 67 3.1 Effect of DDM on observables . 78 3.2 Posteriors for ΛCDM and DDM for Planck data . 83 3.3 Posteriors for ΛCDM and DDM for Planck + local H0 ............ 84 3.4 Posteriors for ΛCDM and DDM for Planck + local H0 + supernovae + BAO 85 3.5 Diminishing the H0 and S8 tensions simultaneously .
Load more

Recommended publications
  • Cosmology Falling in Love with Sterile Neutrinos
    Cosmology Falling in Love with Sterile Neutrinos Jörn Kersten Based on Torsten Bringmann, Jasper Hasenkamp, JK, JCAP 07 (2014) [arXiv:1312.4947] Outline 1 Introduction 2 Self-Interacting Dark Matter 3 Dark Matter Interacting with Neutrinos 3 / 23 1 Introduction 2 Self-Interacting Dark Matter 3 Dark Matter Interacting with Neutrinos 4 / 23 Or does it? Tensions in ΛCDM cosmology The Universe after Planck Flat ΛCDM cosmology fits data perfectly Planck, arXiv:1303.5062 5 / 23 The Universe after Planck Flat ΛCDM cosmology fits data perfectly Planck, arXiv:1303.5062 Or does it? Tensions in ΛCDM cosmology 5 / 23 Measurements of Cosmic Microwave Background (CMB): ∆Neff = 1:51 ± 0:75 at 68% CL ACT, ApJ 739 (2011) ∆Neff = 0:81 ± 0:42 at 68% CL SPT, ApJ 743 (2011) +0:68 ∆Neff = 0:31−0:64 at 95% CL Planck, arXiv:1303.5076 Hints for Dark Radiation Dark radiation: relativistic particles 6= γ; νSM Parameterized via radiation energy density " # 7 T 4 ρ ≡ 1 + N ν ρ rad eff 8 T γ T ≡ Tγ Neff: effective number of neutrino species Standard Model: Neff = 3:046 Existence of dark radiation , ∆Neff ≡ Neff − 3:046 > 0 6 / 23 Hints for Dark Radiation Dark radiation: relativistic particles 6= γ; νSM Parameterized via radiation energy density " # 7 T 4 ρ ≡ 1 + N ν ρ rad eff 8 T γ T ≡ Tγ Neff: effective number of neutrino species Standard Model: Neff = 3:046 Existence of dark radiation , ∆Neff ≡ Neff − 3:046 > 0 Measurements of Cosmic Microwave Background (CMB): ∆Neff = 1:51 ± 0:75 at 68% CL ACT, ApJ 739 (2011) ∆Neff = 0:81 ± 0:42 at 68% CL SPT, ApJ 743 (2011) +0:68
    [Show full text]
  • Dark Radiation and Dark Matter from Primordial Black Holes
    DARK RADIATION AND DARK MATTER FROM PRIMORDIAL BLACK HOLES Dan Hooper – Fermilab and the University of Chicago Next Frontiers in the Search for Dark Matter, GGI September 26, 2019 Dan Hooper – Dark Radiation & Dark Matter from PBHs This talk is based on Dark Radiation and Superheavy Dark Matter from Black Hole Domination With Gordan Krnjaic and Sam McDermott, JHEP 1908 (2019) 001, arXiv:1905.01301 For related work, see Morrison and Profumo, arXiv:1812.10606 and Lennon et al, arXiv:1712.07664 Dan Hooper – Dark Radiation & Dark Matter from PBHs Was the Early Universe Dominated by Black Holes? § Inhomogeneities in the early universe can led to the formation of primordial black holes § Very roughly, we expect the mass of these black holes to be similar to the energy enclosed within the horizon at or near the end of inflation: § In this mass range, black holes evaporate very rapidly, disappearing well before BBN § If even a small fraction of the energy density after inflation was in the form of black holes, this fraction would grow as the universe expands -3 (black holes evolve as matter, �BH � a , rather -4 than radiation, �rad � a ); § From this perspective, it is well-motivated to consider scenarios in which the early universe included an era in which the energy density was dominated by black holes Dan Hooper – Dark Radiation & Dark Matter from PBHs Was the Early Universe Dominated by Black Holes? § Quantitatively, the density of black holes will ultimately exceed the energy density in SM radiation (before the black holes evaporate) if the
    [Show full text]
  • Dark Radiation from the Axino Solution of the Gravitino Problem
    21st of July 2011 Dark radiation from the axino solution of the gravitino problem Jasper Hasenkamp II. Institute for Theoretical Physics, University of Hamburg, Hamburg, Germany [email protected] Abstract Current observations of the cosmic microwave background could confirm an in- crease in the radiation energy density after primordial nucleosynthesis but before photon decoupling. We show that, if the gravitino problem is solved by a light axino, dark (decoupled) radiation emerges naturally in this period leading to a new upper 11 bound on the reheating temperature TR . 10 GeV. In turn, successful thermal leptogenesis might predict such an increase. The Large Hadron Collider could en- dorse this opportunity. At the same time, axion and axino can naturally form the observed dark matter. arXiv:1107.4319v2 [hep-ph] 13 Dec 2011 1 Introduction It is a new opportunity to determine the amount of radiation in the Universe from obser- vations of the cosmic microwave background (CMB) alone with precision comparable to that from big bang nucleosynthesis (BBN). Recent measurements by the Wilkinson Mi- crowave Anisotropy Probe (WMAP) [1], the Atacama Cosmology Telescope (ACT) [2] and the South Pole Telescope (SPT) [3] indicate|statistically not significant|the radi- ation energy density at the time of photon decoupling to be higher than inferred from primordial nucleosynthesis in standard cosmology making use of the Standard Model of particle physics, cf. [4,5]. This could be taken as another hint for physics beyond the two standard models. The Planck satellite, which is already taking data, could turn the hint into a discovery. We should search for explanations from particle physics for such an increase in ra- diation [6,7], especially, because other explanations are missing, if the current mean values are accurate.
    [Show full text]
  • The Early Universe As a Laboratory for Particle Physics
    The Early Universe as a Laboratory for Particle Physics Nikita Blinov April 6, 2021 York University Triumph of the Standard Model Standard Model describes properties and interactions of leptons, quarks and force carriers 100+ years of science !"#N $ift Shop 2 Triumph of the Standard Model Standard Model describes properties and interactions of leptons, quarks and force carriers 100+ years of science !"#N $ift Shop Enormous dynamic range when combined with gravity ,ar)e Hadron Collider probes ~10-20 m Cosmic Micro(ave Background: ~10+24 m 3 The Cosmological Fine Print 4n largest scales, the universe is (ell-described by a %andf l of para'eters Planck ‘18 Only 'eas red indirectly 2%y not 03 .nconsistent (it% q ant m estimates No candidate in Standard Model 4 The Expanding Universe 6ar-a(ay ob7ects (like )alaxies) are receding fro' s - bble (1929) "arlier estimates by Lemaitre (1927) and #obertson (1928) 5 The Expanding Universe 6ar-a(ay ob7ects (like )alaxies) are receding fro' s - bble (1929) 6 #iess et al 2019 Expansion in General Relativity $eneral #elativity relates expansion rate to t%e contents of the niverse Hotter and denser in the past! 7 Early Universe Primer =%e niverse e9panded from a %ot dense state "volution described by C>1 $yr 1 !o'pare (it%* Solar s rface* = ~ 0>? e@ #oo' te'p* = ~ 1AB0 e@ Galaxy formation, life etc 8 Early Universe Primer =%e niverse e9panded from a %ot dense state "volution described by C10 000 yr 1C>1 $yr !o'pare (it%* Solar s rface* = ~ 0>? e@ #oo' te'p* = ~ 1AB0 e@ -ydrogen recombination: Galaxy formation,
    [Show full text]
  • Strategic Overview of Fermilab Particle Astrophysics Program
    Strategic Overview of Fermilab Particle Astrophysics Program Craig Hogan PAC 16 January 2015 Particle Astrophysics at Fermilab Fermilab (and HEP) mission: study the fundamental nature of matter, energy, space and time Cosmic studies uniquely probe deep mysteries: dark matter, cosmic acceleration, neutrino mass, gravity Challenging experiments require capabilities of national laboratories: technologies, development, engineering, scale, management DOE labs share effort on most cosmic experiments Program is planned with University community Fermilab’s plan is based on the scientific drivers in the HEPAP P5 report, as shaped by community support needs, agency funding opportunities, and unique laboratory capabilities 2 Craig Hogan | Particle Astrophysics Program 1/8/15 Fermilab Center for Par0cle Astrophysics Strategic Plan - January 2015 P5 Driver Experiments Dark Maer G1: SuperCDMS Soudan, COUPP/PICO, Darkside, DAMIC G2: SuperCDMS SNOLAB, LZ, ADMX G3: R&D towards advanced WIMP and Axion experiments Dark Energy DES, DESI, LSST CMB SPT-3G, CMB-S4 Exploring the Holometer, Pierre Auger Unknown Detector R&D R&D on new techniques for par0cle astrophysics experiments Astrophysics Strong coupling with par0cle astrophysics experiments Theory Dark Matter Astrophysical evidence suggests that most of our Galaxy is made of a new form of matter Theory suggests that it may be detectable in this decade Weakly Interacting Massive Particles (WIMPs) Axions (solution to CP problem of strong interactions) P5: diverse program for direct detection of WIMPs and axions
    [Show full text]
  • Cosmology in LARGE Volume String Models
    2013 Oct.24th@Tohoku Moduli-Induced Axion Problem Tetsutaro Higaki (KEK) 1208.3563 and 1304.7987 with K. Nakayama and F. Takahashi 2013 Oct.24th@Tohoku Moduli-Induced Axion Probe for extra dimensions Tetsutaro Higaki (KEK) 1208.3563 and 1304.7987 with K. Nakayama and F. Takahashi Cosmological test for string models CMB Ex-dim. + D-branes Axionic dark radiation (= relativistic DM): ΔNeff = O(0.1) Key: Moduli problem in reheating Φ: Moduli/Inflaton a: Axion Axionic dark radiation exists even for mΦ >> 100TeV. Dark radiation Dark radiation ΔNeff in ρrad ΔNeff: Dark radiation, Neff: Effective neutrino number, 3.046: The SM value Effective neutrino number Neff • Observations from Planck (95%): [Planck collaborations] (CMB) (CMB+BAO) (CMB+H0) Effective neutrino number Neff • Observations from Planck (95%): [Planck collaborations] (CMB) (CMB+BAO) (CMB+H0) Dark radiation is hinted, while tension between H0 measurement and CMB/BAO. See also [Hamann and Hasenkamp]: (CMB+HST+C+BAO+WL) Axions in string theory: Dark radiation candidates QCD axion: Strong CP and CDM Ultralight . Original motivations: • A solution of strong CP problem: θ < 10-10 • A candidate of CDM Motivation for string theory Unified theory including quantum gravity! Gauge Matter Gravity D-brane Axions in string theory • Axions via compactifications: C n: n-form gauge field for strings/branes. They can be ultralight and very weak – shift symmetry:aaaaaaaaaaaa; – solution of CP and/or CDM with Moduli Reheating field: • String moduli: Long lifetime: Light + 1/MPl (if SUSY) • Other possibilities: – Inflaton (also in non-SUSY if coupled to axions) – Open string state, e.g., SUSY-breaking fields [Coughlan et al.] Moduli oscillation Radiation Vinflation Vmoduli : moduli VEV : Inflaton potential The decay = Reheating + dark radiation.
    [Show full text]
  • CF1 Sterile Neutrino Dark Matter Bibhushan
    STERILE NEUTRINO DARK MATTER MODELS / THEORY BIBHUSHAN SHAKYA SNOWMASS CF1 MEETING SEPTEMBER 11, 2020 1 STERILE NEUTRINO DARK MATTER MODELS / THEORY AN (INCOMPLETE, RAPID) OVERVIEW For greater details, see one of several reviews in the literature, e.g. • Sterile Neutrino Dark Matter; Boyarsky+, 1807.07938 • A White Paper on keV Sterile Neutrino Dark Matter; Adhikari+, 1602.04816 • Sterile Neutrino Dark Matter from Freeze-in; Shakya, 1512.02751 • The Phenomenology of Right Handed Neutrinos; Drewes, 1303.6912 • keV Neutrino Model Building; Merle, 1302.2625 • … 2 WHY STERILE NEUTRINOS (AS DARK MATTER) ? • Neutrino masses require BSM, most straightforward implementations feature right handed/sterile neutrinos • Very weakly coupled to SM sector: small but non-negligible production in early Universe, as well as long lifetime, are “automatic” • Relatively straightforward/predictive phenomenology: depends mostly on the sterile neutrino mass and mixing angle with SM neutrinos. Diverse signatures: extended neutrino sectors generally feature observable signals in indirect detection, cosmology, colliders, low energy (neutrino) experiments • Hints of sterile neutrinos at several experiments (3.5 keV line, short baseline anomalies) 3 STERILE NEUTRINO AS DARK MATTER: CAVEATS (PROBLEMS / OPPORTUNITIES) • MASS SCALE: The natural value of the mass of a singlet is at the cutoff scale of the theory (e.g. Planck or GUT scale), most of the viable DM candidates have much lower masses (sub-electroweak scale) • Not a disaster: singlet fermion mass does not get large quantum corrections (unlike the higgs); Seesaw mechanism works across a wide range of mass scales (from keV to GUT scale) Nevertheless, need an explanation for the mass scale 4 STERILE NEUTRINO AS DARK MATTER: CAVEATS (PROBLEMS / OPPORTUNITIES) • MASS SCALE: The natural value of the mass of a singlet is at the cutoff scale of the theory (e.g.
    [Show full text]
  • WISP Dark Matter Theory
    WISP Dark Matter Theory. Andreas Ringwald (DESY) Latest Results in Dark Matter Searches Stockholm, Sweden 12-14 May 2014 Introduction > Plenty of dark matter (DM) candi- dates spanning huge parameter range in masses and couplings > Two classes stand out because of their convincing physics case and the variety of experimental and observational probes: § Weakly Interacting Massive Particles (WIMPs), such as neutralinos § Very Weakly Interacting Slim (=ultra- light) Particles (WISPs), such as axions, axion-like particles and hidden photons [Kim,Carosi `10] Andreas Ringwald | WISP Dark Matter Theory, Latest Results in Dark Matter Searches, Stockholm, 12-14 May 2014 | Page 2 Theoretically favored WISP candidates > Pseudo Nambu-Goldstone bosons: § “Axion-Like Particles” (ALPs) arising from breaking of global U(1) symmetries at high energy scale f a ; angular part of complex SM singlet Higgs-like field • Low energy effective field theory has shift symmetry a ( x ) a ( x ) + const . , forbidding 2 2 explicit mass terms, m a a ( x ) , in the Lagrangian ! • Effective couplings to/ SM particles suppressed by powers of high energy scale f a , e.g. coupling to photons, ↵ a C F F˜µ⌫ aγ µ⌫ L ⊃−8⇡ fa • Examples: • Axion from breaking of global chiral symmetry; axion field acts as dynamical theta parameter, [Peccei,Quinn 77; Weinberg 78; Wilczek 78] spontaneously relaxing to zero, (thus CP conserved in strong interactions) • mass due to chiral symmetry breaking, • Majoron from breaking of global lepton number symmetry [Chikashige et al. 78] • high scale
    [Show full text]
  • On Dark Matter - Dark Radiation Interaction and Cosmic Reionization
    IITB-PHY11122017 PREPARED FOR SUBMISSION TO JCAP On dark matter - dark radiation interaction and cosmic reionization Subinoy Das,a Rajesh Mondal,b;c Vikram Rentala,d Srikanth Suresha aIndian Institute of Astrophysics, Bengaluru – 560034, India bAstronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, U.K. cDepartment of Physics and Centre for Theoretical Studies, Indian Institute of Technology Kharag- pur, Kharagpur – 721302, India dDepartment of Physics, Indian Institute of Technology - Bombay, Powai, Mumbai 400076, India E-mail: [email protected], [email protected], [email protected], [email protected] Abstract. The dark matter sector of our universe can be much richer than the conventional picture of a single weakly interacting cold dark matter particle species. An intriguing possibility is that the dark matter particle interacts with a dark radiation component. If the non-gravitational interactions of the dark matter and dark radiation species with Standard Model particles are highly suppressed, then astrophysics and cosmology could be our only windows into probing the dynamics of such a dark sector. It is well known that such dark sectors would lead to suppression of small scale structure, which would be constrained by measurements of the Lyman-α forest. In this work we consider the cosmological signatures of such dark sectors on the reionization history of our universe. Working within the recently proposed “ETHOS” (effective theory of structure formation) framework, we show that if such a dark sector exists in our universe, the suppression of low mass dark matter halos would also reduce the total number of ionizing photons, thus affecting the reionization history of our universe.
    [Show full text]
  • Dark Radiation IAXO
    Dark radiation in IAXO José Manuel Carmona Universidad de Zaragoza 1. The axiverse from string theory 2. Moduli and dark radiation 3. The cosmic axion background and IAXO References: Arvanitaki et al., PRD 81 (2010) Conlon & Marsch, JHEP 10 (2013), PRL 111 (2013) J. Conlon, talk at ESQG (Frankfurt, 2016) J. Redondo, private communication Fine-tuning and the strong CP problem and seems like a big fine-tuning: strong CP problem • Moreover, no symmetry of the SM is restored as Other similar apparent fine-tunings: cosmological constant, hierarchy problem However, has no anthropic solution: call for a dynamical mechanism PQ mechanism: a new (anomalous) spontaneously broken chiral symmetry U(1)PQ • QCD axion: the NG boson of the SSB, BUT: all other sources of explicit U(1)PQ breaking should be at least 10 orders of magnitude down with respect to the potential generated by the QCD anomaly • Quantum gravity effects? String theory Axions in string theory Massless fields arise in string theory under compactification of M6 as Kaluza-Klein zero modes of antisymmetric tensor fields, present in all string theories • Number of massless scalar fields is determined by the topology of the compactification (e.g., number of 2-cycles in M6 , usually more than one hundred) Axions in string theory Massless fields arise in string theory under compactification of M6 as Kaluza-Klein zero modes of antisymmetric tensor fields, present in all string theories • Number of massless scalar fields is determined by the topology of the compactification (e.g., number of 2-cycles in M6 , usually more than one hundred) • Anomaly-cancellation conditions result in axion-like couplings for these fields String compactifications have plenty of candidates for axion-like particles But… do they really predict the QCD axion? Difficulties: 1.
    [Show full text]
  • 25. Neutrinos in Cosmology
    1 25. Neutrinos in Cosmology 25. Neutrinos in Cosmology Revised August 2019 by J. Lesgourgues (TTK, RWTH) and L. Verde (ICC, U. of Barcelona; ICREA, Barcelona). 25.1 Standard neutrino cosmology Neutrino properties leave detectable imprints on cosmological observations that can then be used to constrain neutrino properties. This is a great example of the remarkable interconnection and interplay between nuclear physics, particle physics, astrophysics and cosmology (for general reviews see e.g., [1–4]). Present cosmological data are already providing constraints on neutrino properties not only complementary but also competitive with terrestrial experiments; for instance, upper bounds on the total neutrino mass have shrinked by a factor of about 14 in the past 17 years. Forthcoming cosmological data may soon provide key information, not obtainable in other ways like e.g., a measurement of the absolute neutrino mass scale. This new section is motivated by this exciting prospect. A relic neutrino background pervading the Universe (the Cosmic Neutrino background, CνB) is a generic prediction of the standard hot Big Bang model (see Big Bang Nucleosynthesis – Chap. 23 of this Review). While it has not yet been detected directly, it has been indirectly confirmed by the accurate agreement of predictions and observations of: a) the primordial abundance of light elements (see Big Bang Nucleosynthesis – Chap. 23) of this Review; b) the power spectrum of Cosmic Microwave Background (CMB) anisotropies (see Cosmic Microwave Background – Chap. 28 of this Review); and c) the large scale clustering of cosmological structures. Within the hot Big Bang model such good agreement would fail dramatically without a CνB with properties matching closely those predicted by the standard neutrino decoupling process (i.e., involving only weak interactions).
    [Show full text]
  • Abstracts Dark Universe.Odt
    TALKS Rouzbeh Allahverdi - Nonthermal Dark Matter and Baryogenesis We study a simple TeV-scale model of baryon number violation which explains the observed proximity of the dark matter and baryon abundances. The model has constraints arising from both low and high-energy processes, and in particular, predicts a sizable rate for the neutron-antineutron (n−n¯) oscillation at low energy and the monojet signal at the LHC. We find an interesting complementarity among the constraints arising from the observed baryon asymmetry, ratio of dark matter and baryon abundances, n−n¯ oscillation lifetime and the LHC monojet signal. There are regions in the parameter space where the n−n¯oscillation lifetime is found to be more constraining than the LHC constraints, which illustrates the importance of the next-generation n−n¯oscillation experiments. Otávio Alonso - Probing Dark Matter properties using photometric surveys Despite decades of its first proposal, Dark Matter is still one of the big mysteries in cosmology. Different probes can shed light into different aspects of it, but they agree in a good level that it can be modeled as a pressureless perfect fluid, although we have reason to call that into question. Here we discuss how can we learn about Dark Matter from weak lensing and galaxy clustering in the context of photometric surveys. In particular, we present a phenomenological framework that generalizes DM behavior and look for constraints using The Dark Energy Survey data. Yang Bai - Primordial Extremal Black Holes as Dark Matter We show that primordial (nearly) extremal black holes with a wide range of masses from the Planck scale to around 1000 tons could be cosmologically stable and explain dark matter, given a dark electromagnetism and a heavy dark electron.
    [Show full text]