Extending classical big bang theory
|
|
- Ashlynn Carroll
- 5 years ago
- Views:
Transcription
1 Chapter 21 Extending classical big bang theory The big bang is our standard model for the origin of the Universe and has been for almost half a century. This place in well earned. At a broader conceptual level, all of modern cosmology rests on observations (for example, the very existence of the cosmic microwave background radiation) that make sense only if there was a big bang or something very much like it in our past. At a more nuts and bolts level, the standard big bang model accounts quantitatively for a variety of relatively precise observational data (for example, those associated with specific properties of the cosmic microwave background and with the observed abundances of light elements) that would be difficult to explain with any competing theory. However, there are some observations in modern cosmology suggesting that the classical big bang is an essentially correct but perhaps incomplete picture of the origin and evolution of our Universe. In this chapter we address some of these issues. 841
2 842 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY 21.1 Successes of the Big Bang Let us begin by being more explicit about the successes of the standard big bang and its place in the modern picture of cosmology. As we have already discussed to some degree in Chapter 16, The standard cosmology rests on a relatively few observations and concepts: 1. The redshifts of distant galaxies imply that we live in an expanding Universe described at the simplest level by the Hubble law. 2. On large enough scales (beyond that of superclusters of galaxies) the Universe appears to be both homogeneous and isotropic (cosmological principle). 3. The properties of distant quasars suggest that these powerful energy sources were once more energetic and more closely spaced than they are today, implying that the properties of the Universe on large scales has evolved with time. 4. The cosmic microwave background (CMB) is all pervading, highly isotropic but with measureable fluctuations at the one part in 10 5 level, and possesses an almost perfect blackbody spectrum with a temperature of ± K. 5. The elemental composition of the Universe is (by mass) three parts H to one part He, with but a trace of heavier elements.
3 21.1. SUCCESSES OF THE BIG BANG Because gravitation and not electromagnetism governs the largescale structure of the Universe, it must be charge neutral on large scales. Conversely, observations indicate that the Universe is highly asymmetric with respect to matter and antimatter, with no evidence for significant equilibrium concentrations of antimatter. 7. There are many fewer baryons in the Universe than there are microwave photons. 8. In contrast to the homogeneity of the Universe on very large scales (cosmological principle), matter on scales comparable to superclusters of galaxies and smaller exhibits complex and highly evolved structure, This contrasts sharply with the smoothness of the CMB. Furthermore, observations indicate that this structure began to develop very early in the history of the Universe. 9. Detailed analysis of fluctuations in the CMB and of the brightness of distant Type Ia supernovae indicate that (a) The expansion of the Universe is presently accelerating. (b) The geometry of the Universe is remarkably flat (euclidean). 10. The bulk of the matter in the Universe is not luminous (dark matter), being observable only through its gravitational influence. 11. Various observational constraints imply that most of this dark matter is not baryonic.
4 844 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY The first five observations fit well within classical big bang cosmologies: Observations (1) (2) indicate that we live in an expanding, isotropic universe, Observations (3) (5) indicate that this Universe has evolved over time and had a beginning in a very hot, very dense initial state (the big bang). The remaining observations need not be inconsistent with the classical big bang, but they require either ad hoc imposition of particular initial conditions on the Universe, or assumption of specific properties for the microscopic properties of the matter and energy fields that the Universe contains that we shall address in the next section.
5 21.2. PROBLEMS WITH THE BIG BANG Problems with the Big Bang As we have indicated in the previous section, observational properties (6) (11) constitute problems for the classical big bang model. They do not necessarily invalidate the big bang, but they indicate that the big bang in its minimal form may be incomplete. In most cases we shall find that this incompleteness is likely to originate in an inadequate understanding of how the particle and field content of the Universe couples to its evolution. Let us now discuss these problems.
6 846 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY The Horizon Problem Observational property (4) [isotopy of the CMB] presents a potential conflict with causality because The nearly constant temperature of the CMB in widely separated parts of the sky is understandable only if those regions were in causal contact in the past. But in the standard big bang it is easy to show that regions on the sky separated by more than a degree or two in angle could never have been in causal contact (had sufficient time to exchange light signals) since the big bang. That is, they lie outside each other s horizons, as illustrated in Fig on the following page, and thus cannot have been in causal contact in the past.
7 21.2. PROBLEMS WITH THE BIG BANG 847 Horizon: greatest distance from which light could have reached us since the big bang (a) Earth Observable Universe Object presently inside the horizon. It can be seen from Earth Earth Object outside the horizon. It cannot be seen from Earth because light from it has not had time to reach us since the big bang. Earth's horizon Part of the Universe that both the Earth observer and distant observer can see (b) Horizon increases with time Earth (c) Distant observer Distant observer's horizon Earth The object that was outside the horizon now enters our horizon and is visible from Earth. (d) A and B are now outside of each other's horizons. This means they have always been outside of each other's horizons in the standard big bang model. A Earth B Horizon for A Earth horizon Horizon for B Figure 21.1: Horizons in an expanding universe. (a) A (cosmological) horizon is the greatest distance from which light could have reached us since the beginning of time. (b) Horizons expand with time, so objects currently outside our horizon may come within our horizon in the future. (c) Cosmological horizons are defined relative to each observer, so each has her own horizon. (d) Horizon problem produced by the CMB having identical temperatures on opposite sides of the sky for an observer: how do A and B know to have the same temperature if they could never have exchanged signals in the past?
8 848 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY Tiny change in initial conditions Scale factor Actual flat Universe Different tiny change in initial conditions Time Figure 21.2: The flatness problem: producing a flat Universe today requires remarkable fine-tuning of the initial curvature for the Universe The Flatness Problem Observational property 9(b) implies that the Universe is euclidean. This indicates that the Universe is very near the closure density. Consistent with big bang, but this condition can be realized only if parameters are very finely tuned in the early universe (Fig. 21.2). Example (Exercise): the fractional deviation of the density from the critical density at any time in the evolution of the Universe is ρ ρ = ρ ρ c ρ = 3kc2 8πGa 2 ρ, From this result, unless the flatness is tuned to one part in at the Planck time we end up with a Universe that is far from flat today. While possible, this does not seem to be a very natural initial condition.
9 21.2. PROBLEMS WITH THE BIG BANG 849 Strong Strength of force E & M Weak Gravity GUTs scale Magnetic monopoles produced? Planck scale Temperature Figure 21.3: The magnetic monopole problem of the standard big bang: where are the massive relic particles that would be expected to be produced at phase transitions like grand unification (labeled GUTs)? The Magnetic Monopole Problem There are reasons to believe that massive particles like magnetic monopoles could be produced copiously at phase transitions in the early universe, as illustrated in Fig This has two adverse consequences: Such particles have never been detected in experiments, and If they were produced in large numbers they would have halted the expansion of the Universe and then caused it to collapse. These problems are removed if we simply declare that such particles are not produced in large numbers, but why should such an initial condition be required?
10 850 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY The Structure and Smoothness Dichotomy Observational properties (4) and (8) (smoothness of CMB vs. existence of large-scale structure) present a severe compatibility issue: The remarkably high smoothness of the CMB implies that the early Universe was strikingly devoid of density perturbations. Where then did the density perturbations responsible for the growth of rich structure in the present Universe on the supercluster and smaller scale originate? The form of the density perturbations required to give the observed structure is known so they could be postulated as initial conditions, but again we would like to know why.
11 21.2. PROBLEMS WITH THE BIG BANG The Vacuum Energy Problem Observation 9(a) (accelerated expansion) has a simple explanation only if the Universe contains dark energy. This would be most naturally explained if dark energy is a consequence of vacuum fluctuations. However, estimates of the vacuum energy content of the Universe are spectacularly wrong in comparison with the corresponding observational constraints. The accelerated expansion is consistent with the big bang picture if we simply postulate the existence of dark energy in the Universe in the required amount. But it is highly unsatisfying to have no understanding of where this fundamental influence on the evolution of the Universe comes from.
12 852 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY The Matter Antimatter and Baryogenesis Problem Observation (8) indicates that the physical universe contains almost entirely matter with little corresponding antimatter. We can impose this as an initial condition but that is bothersome given that matter and antimatter enter modern elementary particle physics theory on an equal footing. A closely-related problem (because annihilation of baryons with antibaryons produces photons) is how to account for the large excess of photons over baryons in the Universe (Observation 7).
13 21.2. PROBLEMS WITH THE BIG BANG Modifying the Classical Big Bang We shall now discuss some possible resolutions of these problems. In attempting to resolve the problems we have to be careful to preserve the successes of the big bang model. The successful predictions of the big bang model rest primarily on the evolution of the Universe at times later than about one second after the initiation of the big bang. Therefore, any modification of our cosmological model that influences the Universe at times less than about one second after the big bang will leave the successes of the big bang intact if they leave appropriate initial conditions for the subsequent evolution. We begin with a proposed modification of the evolution of the Universe operative only in the first tiny fraction of a second of the big bang that has the potential to resolve the first four problems listed above in a single stroke.
14 854 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY 21.3 Cosmic Inflation The theory of cosmic inflation is based on a simple but striking idea that has been discussed already in conjunction with the de Sitter solution: In the presence of an energy density that is constant over all space, the Einstein equation admits an exponentially growing solution. If the Universe underwent a short burst of exponential growth before settling down into more normal big bang evolution, there would be potentially large implications for the evolution of the Universe. We shall take the essential point of inflation to be this general idea of the Universe experiencing a period of exponential growth. There are many specific versions of inflationary theory that implement this in different ways. For the most part we shall leave those specifics for the interested reader to pursue in the specialist literature. Our reason is that there is now compelling evidence that the basic idea of inflation is necessary to explain the evolution of the early Universe, but no specific version of inflation currently available gives a completely satisfactory accounting of the cause and detailed effects of the inflationary period.
15 21.3. COSMIC INFLATION Inflationary Theory From earlier discussion of the de Sitter solution, A universe with pure vacuum energy expands exponentially, a(t)=e Ht, where the Hubble parameter H is constant. The basic idea of inflationary theory is that shortly after its birth the Universe found itself in a situation dominated by a constant (or nearly constant) energy density. This drove an exponential expansion for a very short period of time that cooled the Universe rapidly because of the expansion. Then at the end of this period the Universe exited from the inflationary conditions and reheated. The mechanism for reheating depends on the version of inflation assumed, but generally involves the rapid conversion of the constant energy density driving inflation into the mass energy of more normal particles). This then produced a situation dominated by radiation rather than vacuum energy, which caused the Universe to evolve according to a standard (hot) big bang scenario (power law rather than exponential dependence of the scale factor on time).
16 856 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY In various versions of inflation different reasons are assumed for the initial conditions that triggered the exponential expansion. The original inflationary idea due to Alan Guth assumed that inflation was driven by a Lorentz scalar field associated with a first-order phase transition. This is conceptually simple, but proved to be incompatible with observations (as Guth himself realized). It was found that the resulting inflation could not halt in a manner that would give something that looks like the real Universe. In subsequent versions of inflation the inflation was often assumed to be driven by a scalar field having a time dependence of a particular form called a slow rollover transition. Although such theories often give a reasonably good account of data, they suffer from 1. having little connection to scalar fields known already to exist in elementary particle physics, and 2. requiring extremely fine empirical tuning of parameters to account well for data. In keeping with the philosophy outlined above, we omit discussion of these different forms of inflation and instead concentrate on the consequences of inflationary expansion.
17 21.3. COSMIC INFLATION 857 (a) s (b) Hot big bang? Hot big bang a Inflation ~10 50 T 2? No inflation Inflation Reheat Time Time Figure 21.4: The inflationary scenario. (a) In the inflationary epoch the Universe expands exponentially, which can increase the scale factor by factors of or larger on a timescale of order s. (b) The Universe cools as it expands exponentially. At the end of inflation some mechanism, not yet well understood, must reheat the Universe, which then continues a standard hot big bang evolution. Figure 21.4 illustrates the behavior of the scale factor and the temperature in highly schematic fashion during inflation and the following big bang evolution. During inflation the Universe expanded at a much higher rate than in normal big bang evolution. At the same time, the temperature dropped rapidly in the exponentially expanding Universe. Finally, when the period of inflation halted the Universe first rapidly reheated and then began to decrease in temperature according to the standard big bang scenario. The question marks represent our substantial lack of knowledge concerning the Universe prior to the inflationary period.
18 858 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY 1 2 Eventual location of Earth Causally-connected, homogenous region Horizon Inflation Standard big bang evolution 1 Horizon 2 Inflationary universe expands faster than the horizon Horizon expands faster than big bang universe 1 Reenter horizon 2 In inflation an original small, homogeneous region expands much faster than does the horizon distance. Then when inflation ends and normal big bang evolution begins, the horizon expands faster than the Universe. Figure 21.5: Solution of the horizon problem in the inflationary universe Taking the inflationary cure The inflationary scenario provides (in principle) a solution to the four fundamental problems posed above. Solution of the Horizon Problem The solution of the horizon problem is illustrated in Fig The tremendous expansion means that regions that we see widely separated in the sky now at the horizon were much closer together before inflation. Thus, they could have been in contact by light signals.
19 21.3. COSMIC INFLATION 859 Solution of the Flatness Problem The tremendous expansion greatly dilutes any initial curvature. Think of standing on a basketball. It would be obvious that you are standing on a two-dimensional curved surface. Now imagine expanding the basketball to the size of the Earth. As you stand on it now, it will appear to be flat, even though it is actually curved if you could see it from large enough distance. The same idea extended to four-dimensional spacetime accounts for the present flatness (lack of curvature) in the space of the Universe. Out to the greatest distances that we can see the Universe looks flat on large scales, just as the Earth looks approximately flat out to our horizon.
20 860 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY Solution of the Monopole Problem The rapid expansion of the Universe tremendously dilutes the concentration of any magnetic monopoles that are produced. Simple calculations indicate that they become so rare in any given volume of space that we would be very unlikely to ever encounter one in an experiment designed to search for them. Nor would they have sufficient density to alter the gravity and thereby the normal expansion of the Universe following inflation.
21 21.3. COSMIC INFLATION 861 Subatomic scale Vacuum Time Particle Antiparticle Vacuum Figure 21.6: Quantum fluctuations can create a particle-antiparticle pair from the vacuum for a fleeting instant. In inflation such microscopic fluctuations can be stretched to macroscopic scales, producing density perturbations that can later seed the formation of large-scale structure. Inflation and the Formation of Structure Perhaps the most important consequence of inflation is that it provides a possible solution to the origin of large-scale structure. The inflationary explanation is in fact rather remarkable. During inflation quantum fluctuations such as that illustrated in Fig (which must be present because of the uncertainty principle) end up being stretched from microscopic to macroscopic dimensions by the exponential expansion. Because this process occurs during the entire time of inflation, one ends up with density fluctuations of macroscopic size varying over many length scales.
22 862 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY Technically, this produces what is termed a scale-invariant spectrum of density fluctuations, and it is known empirically that this is the spectrum of density perturbations that is most likely to lead to the observed large-scale structure in the Universe. These density perturbations will generally be expanded beyond the horizon during inflation. But after inflation is over and normal big bang evolution sets in, the horizon grows with time. Eventually these density perturbations come back within the horizon where they can serve as nucleation centers for the formation of structure.
23 21.3. COSMIC INFLATION 863 Angular wavelength (degrees) Temperature fluctuation (µk) Inflation with dark energy Inflation with no dark energy Open universe, no inflation, no dark energy WMAP CBI ACBAR BOOMERANG Multipole order Figure 21.7: Temperature fluctuations in the cosmic microwave background from satellite and high-altitude balloon observations compared with various theoretical models. Although there are many specific theories of inflation, it is encouraging that simulations of large-scale structure give reasonable results when the effects of inflation are included. Furthermore, the fluctuations in the CMB observed by WMAP are described best by theories that include the effect of inflation. For example, Fig compares the angular fluctuations in temperature for the CMB with various models with and without inflation and with and without dark energy. Models with both dark energy and inflation are clearly favored.
24 864 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY Inflation Doesn t Replace the Big Bang Inflation is not a theory in competition with the big bang: The theory of inflation modifies only the first tiny instants of creation. After the completion of the brief period of inflation, it is assumed that big bang evolution continues as described earlier. Thus, inflation should be viewed as a modified form of the big bang that accounts for effects due to the properties of elementary particles that are not included in the standard big bang.
25 21.4. THE ORIGIN OF THE BARYONS The Origin of the Baryons In the standard big bang the preponderance of matter over antimatter and of photons over baryons in the Universe have to be introduced through initial conditions without fundamental justification. Sakharov first enumerated the ingredients required to generate baryon asymmetries within the standard big bang model: 1. There must exist elementary particle interactions in the Universe that do not conserve baryon number N B. 2. There must exist interactions that violate both charge conjugation symmetry (C) and the product of charge conjugation and parity (P) symmetries (the product is denoted CP). 3. There must be departures from thermal equilibrium during the evolution of the Universe.
26 866 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY In these requirements Baryon number N B takes the value +1 for a baryon and 1 for an antibaryon. Baryon number is then the algebraic sum of these numbers for all the particles in a reaction. Conservation of baryon number (observed in every experiment done so far) means that this number does not change in the interaction. Charge conjugation symmetry (C) is symmetry under exchange of a particle with its antiparticle. Parity symmetry (P) is symmetry under inversion of the coordinate system through the origin. CP symmetry is symmetry under inversion of the coordinate system and exchange of particle with antiparticle. Most interactions conserve these symmetries to high precision but the weak interactions are known to violate P, C, and CP.
27 21.4. THE ORIGIN OF THE BARYONS 867 Departures from thermal equilibrium are likely to have occurred at various times in the evolution of the Universe. At least the weak interactions are known to violate both C and CP symmetry. Thus (in principle) all ingredients exist to account for baryon asymmetry except for baryon non-conserving reactions. Experimentally, baryon non-conservation has never been observed. However, there are theoretical reasons to believe that baryon conservation might not be an exact symmetry but just one that has not yet been observed to be violated. For example baryon non-conservation may occur only on a energy scale not yet reached in laboratory experiments but that could have occurred in the early Universe.
28 868 CHAPTER 21. EXTENDING CLASSICAL BIG BANG THEORY One class of elementary particle theories that features baryon-number violating interactions prominently and thus could have played a role in producing the baryons is that of Grand Unified Theories (GUTs). In the Standard Electroweak Theory of elementary particle physics the electromagnetic interactions and the weak interactions have been (partially) unified. This means that at high enough energy (in this case a scale of about 100 GeV, where a GeV is 10 9 ev) the weak and electromagnetic interactions take on the same properties. A GUT attempts to extend this idea to unify weak, electromagnetic, and strong interactions into a single unified theory. The characteristic GUT energy scale is very high ( GeV is a common estimate), but on that scale GUTs typically violate baryon number strongly. At one time GUTs were favored as the likely way to account for baryogenesis but there have since been shown to be difficulties with this approach. In particular, it seems that a baryon asymmetry generated by a GUTs phase transition would likely be wiped out by the cosmic inflation described earlier. Thus a viable theory of baryon asymmetry may require a baryonviolating phase transition at a lower energy scale than the GUTs scale.
29 21.4. THE ORIGIN OF THE BARYONS 869 A possible alternative mechanism is leptogenesis. Leptogenesis postulates that perhaps the baryon asymmetry was generated by strongly CP-violating processes in the electroweak sector. But it is not clear that this can account for the observed baryon asymmetry of the Universe because the known electroweak interactions do not exhibit interactions with the required characteristics. However, the correct electroweak theory could be more general than the present one (which is not tested exhaustively at energies of 100 GeV or larger, and is now known to be contradicted by the small but finite masses observed for neutrinos). Thus, an improved electroweak theory eventually might be able to account for the baryon asymmetry.
Beyond the Classical Big Bang
Chapter 33 Beyond the Classical Big Bang The big bang is our standard model for the origin of the Universe and has been for almost half a century. This place in well earned. At a broader conceptual level,
More informationPhysics 133: Extragalactic Astronomy and Cosmology. Week 8
Physics 133: Extragalactic Astronomy and Cosmology Week 8 Outline for Week 8 Primordial Nucleosynthesis Successes of the standard Big Bang model Olbers paradox/age of the Universe Hubble s law CMB Chemical/Physical
More informationAstr 2320 Thurs. May 7, 2015 Today s Topics Chapter 24: New Cosmology Problems with the Standard Model Cosmic Nucleosynthesis Particle Physics Cosmic
Astr 2320 Thurs. May 7, 2015 Today s Topics Chapter 24: New Cosmology Problems with the Standard Model Cosmic Nucleosynthesis Particle Physics Cosmic Inflation Galaxy Formation 1 Chapter 24: #3 Chapter
More informationThe Concept of Inflation
The Concept of Inflation Introduced by Alan Guth, circa 1980, to provide answers to the following 5 enigmas: 1. horizon problem. How come the cosmic microwave background radiation is so uniform in very
More informationA100H Exploring the Universe: Big Bang Theory. Martin D. Weinberg UMass Astronomy
A100H Exploring the : Martin D. Weinberg UMass Astronomy astron100h-mdw@courses.umass.edu April 21, 2016 Read: Chap 23 04/26/16 slide 1 Early Final Exam: Friday 29 Apr at 10:30 am 12:30 pm, here! Emphasizes
More informationInflation. Week 9. ASTR/PHYS 4080: Introduction to Cosmology
Inflation ASTR/PHYS 4080: Intro to Cosmology Week 9 1 Successes of the Hot Big Bang Model Consists of: General relativity Cosmological principle Known atomic/nuclear/particle physics Explains: dark night
More informationHubble's Law. H o = 71 km/s / Mpc. The further a galaxy is away, the faster it s moving away from us. V = H 0 D. Modern Data.
Cosmology Cosmology is the study of the origin and evolution of the Universe, addressing the grandest issues: How "big" is the Universe? Does it have an "edge"? What is its large-scale structure? How did
More informationINFLATION. - EARLY EXPONENTIAL PHASE OF GROWTH OF SCALE FACTOR (after T ~ TGUT ~ GeV)
INFLATION - EARLY EXPONENTIAL PHASE OF GROWTH OF SCALE FACTOR (after T ~ TGUT ~ 10 15 GeV) -Phenomenologically similar to Universe with a dominant cosmological constant, however inflation needs to end
More informationIntroduction to Cosmology
Introduction to Cosmology Subir Sarkar CERN Summer training Programme, 22-28 July 2008 Seeing the edge of the Universe: From speculation to science Constructing the Universe: The history of the Universe:
More informationIntroduction to Inflation
Introduction to Inflation Miguel Campos MPI für Kernphysik & Heidelberg Universität September 23, 2014 Index (Brief) historic background The Cosmological Principle Big-bang puzzles Flatness Horizons Monopoles
More informationCosmology and particle physics
Cosmology and particle physics Lecture notes Timm Wrase Lecture 9 Inflation - part I Having discussed the thermal history of our universe and in particular its evolution at times larger than 10 14 seconds
More informationOrigin of the Universe
Origin of the Universe Shortcomings of the Big Bang Model There is tremendous evidence in favor of the Big Bang Cosmic Microwave Background Radiation Abundance of Deuterium, Helium, Lithium, all cooked
More informationThe History and Philosophy of Astronomy
Astronomy 350L (Spring 2005) The History and Philosophy of Astronomy (Lecture 27: Modern Developments II: Inflation) Instructor: Volker Bromm TA: Amanda Bauer The University of Texas at Austin Big Bang
More informationi>clicker Quiz #14 Which of the following statements is TRUE?
i>clicker Quiz #14 Which of the following statements is TRUE? A. Hubble s discovery that most distant galaxies are receding from us tells us that we are at the center of the Universe B. The Universe started
More informationChapter 22 Lecture. The Cosmic Perspective. Seventh Edition. The Birth of the Universe Pearson Education, Inc.
Chapter 22 Lecture The Cosmic Perspective Seventh Edition The Birth of the Universe The Birth of the Universe 22.1 The Big Bang Theory Our goals for learning: What were conditions like in the early universe?
More informationThe Early Universe. 1. Inflation Theory: The early universe expanded enormously in a brief instance in time.
The Early Universe The Early Universe 1. Inflation Theory: The early universe expanded enormously in a brief instance in time. 2. The fundamental forces change during the first second after the big bang.
More informationThe Expanding Universe
Cosmology Expanding Universe History of the Universe Cosmic Background Radiation The Cosmological Principle Cosmology and General Relativity Dark Matter and Dark Energy Primitive Cosmology If the universe
More information4.3 The accelerating universe and the distant future
Discovering Astronomy : Galaxies and Cosmology 46 Figure 55: Alternate histories of the universe, depending on the mean density compared to the critical value. The left hand panel shows the idea graphically.
More informationThe Cosmological Principle
Cosmological Models John O Byrne School of Physics University of Sydney Using diagrams and pp slides from Seeds Foundations of Astronomy and the Supernova Cosmology Project http://www-supernova.lbl.gov
More informationChapter 18. Cosmology in the 21 st Century
Chapter 18 Cosmology in the 21 st Century Guidepost This chapter marks a watershed in our study of astronomy. Since Chapter 1, our discussion has focused on learning to understand the universe. Our outward
More informationStructures in the early Universe. Particle Astrophysics chapter 8 Lecture 4
Structures in the early Universe Particle Astrophysics chapter 8 Lecture 4 overview Part 1: problems in Standard Model of Cosmology: horizon and flatness problems presence of structures Part : Need for
More informationLecture notes 20: Inflation
Lecture notes 20: Inflation The observed galaxies, quasars and supernovae, as well as observations of intergalactic absorption lines, tell us about the state of the universe during the period where z
More informationChapter 17 Cosmology
Chapter 17 Cosmology Over one thousand galaxies visible The Universe on the Largest Scales No evidence of structure on a scale larger than 200 Mpc On very large scales, the universe appears to be: Homogenous
More informationHot Big Bang model: early Universe and history of matter
Hot Big Bang model: early Universe and history of matter nitial soup with elementary particles and radiation in thermal equilibrium. adiation dominated era (recall energy density grows faster than matter
More informationAy1 Lecture 18. The Early Universe and the Cosmic Microwave Background
Ay1 Lecture 18 The Early Universe and the Cosmic Microwave Background 18.1 Basic Ideas, and the Cosmic Microwave background The Key Ideas Pushing backward in time towards the Big Bang, the universe was
More informationCosmic Background Radiation
Cosmic Background Radiation The Big Bang generated photons, which scattered frequently in the very early Universe, which was opaque. Once recombination happened the photons are scattered one final time
More informationXIII. The Very Early Universe and Inflation. ASTR378 Cosmology : XIII. The Very Early Universe and Inflation 171
XIII. The Very Early Universe and Inflation ASTR378 Cosmology : XIII. The Very Early Universe and Inflation 171 Problems with the Big Bang The Flatness Problem The Horizon Problem The Monopole (Relic Particle)
More informationOne of elements driving cosmological evolution is the presence of radiation (photons) Early universe
The Frontier Matter and Antimatter One of elements driving cosmological evolution is the presence of radiation (photons) Early universe Matter and antimatter But we live in universe full of matter -- where
More informationCosmology. An Analogy 11/28/2010. Cosmology Study of the origin, evolution and future of the Universe
Cosmology Cosmology Study of the origin, evolution and future of the Universe Obler s Paradox If the Universe is infinite why is the sky dark at night? Newtonian Universe The Universe is infinite and unchanging
More informationExploring the Early Universe. Chapter Twenty-Nine. Guiding Questions. The Isotropy Problem
Exploring the Early Universe Chapter Twenty-Nine Guiding Questions 1. Has the universe always expanded as it does today, or might it have suddenly inflated? 2. How did the fundamental forces of nature
More information2. The evolution and structure of the universe is governed by General Relativity (GR).
7/11 Chapter 12 Cosmology Cosmology is the study of the origin, evolution, and structure of the universe. We start with two assumptions: 1. Cosmological Principle: On a large enough scale (large compared
More informationAstronomy 182: Origin and Evolution of the Universe
Astronomy 182: Origin and Evolution of the Universe Prof. Josh Frieman Lecture 14 Dec. 2, 2015 Today The Inflationary Universe Origin of Density Perturbations Gravitational Waves Origin and Evolution of
More informationVU lecture Introduction to Particle Physics. Thomas Gajdosik, FI & VU. Big Bang (model)
Big Bang (model) What can be seen / measured? basically only light _ (and a few particles: e ±, p, p, ν x ) in different wave lengths: microwave to γ-rays in different intensities (measured in magnitudes)
More informationMatter vs. Antimatter in the Big Bang. E = mc 2
Matter vs. Antimatter in the Big Bang Threshold temperatures If a particle encounters its corresponding antiparticle, the two will annihilate: particle + antiparticle ---> radiation * Correspondingly,
More informationIt is possible for a couple of elliptical galaxies to collide and become a spiral and for two spiral galaxies to collide and form an elliptical.
7/16 Ellipticals: 1. Very little gas and dust an no star formation. 2. Composed of old stars. 3. Masses range from hundreds of thousands to 10's of trillions of solar masses. 4. Sizes range from 3000 ly
More informationFundamental Particles
Fundamental Particles Standard Model of Particle Physics There are three different kinds of particles. Leptons - there are charged leptons (e -, μ -, τ - ) and uncharged leptons (νe, νμ, ντ) and their
More informationMIT Exploring Black Holes
THE UNIVERSE and Three Examples Alan Guth, MIT MIT 8.224 Exploring Black Holes EINSTEIN'S CONTRIBUTIONS March, 1916: The Foundation of the General Theory of Relativity Feb, 1917: Cosmological Considerations
More informationAstro-2: History of the Universe. Lecture 12; May
Astro-2: History of the Universe Lecture 12; May 23 2013 Previously on astro-2 The four fundamental interactions are? Strong, weak, electromagnetic and gravity. We think they are unified at high energies,
More informationThe Universe: What We Know and What we Don t. Fundamental Physics Cosmology Elementary Particle Physics
The Universe: What We Know and What we Don t Fundamental Physics Cosmology Elementary Particle Physics 1 Cosmology Study of the universe at the largest scale How big is the universe? Where What Are did
More informationLab Monday optional: review for Quiz 3. Lab Tuesday optional: review for Quiz 3.
Announcements SEIs! Quiz 3 Friday. Lab Monday optional: review for Quiz 3. Lab Tuesday optional: review for Quiz 3. Lecture today, Wednesday, next Monday. Final Labs Monday & Tuesday next week. Quiz 3
More informationAstro-2: History of the Universe
Astro-2: History of the Universe Lecture 11; May 21 2013 Previously on astro-2 In an expanding universe the relationship between redshift and distance depends on the cosmological parameters (i.e. the geometry
More informationInflationary Universe and. Quick survey about iclickers Review of Big Bang model of universe Review of Evidence for Big Bang Examining Inflation
Inflationary Universe and Quick survey about iclickers Review of Big Bang model of universe Review of Evidence for Big Bang Examining Inflation Survey questions 1. The iclickers used in class encouraged
More informationSurvey questions. Inflationary Universe and. Survey Questions. Survey questions. Survey questions
Inflationary Universe and Quick survey about iclickers Review of Big Bang model of universe Review of Evidence for Big Bang Examining Inflation Survey questions 1. The iclickers used in class encouraged
More informationLecture #25: Plan. Cosmology. The early Universe (cont d) The fate of our Universe The Great Unanswered Questions
Lecture #25: Plan Cosmology The early Universe (cont d) The fate of our Universe The Great Unanswered Questions Announcements Course evaluations: CourseEvalUM.umd.edu Review sheet #3 was emailed to you
More informationGalaxies 626. Lecture 3: From the CMBR to the first star
Galaxies 626 Lecture 3: From the CMBR to the first star Galaxies 626 Firstly, some very brief cosmology for background and notation: Summary: Foundations of Cosmology 1. Universe is homogenous and isotropic
More informationEarlier in time, all the matter must have been squeezed more tightly together and a lot hotter AT R=0 have the Big Bang
Re-cap from last lecture Discovery of the CMB- logic From Hubble s observations, we know the Universe is expanding This can be understood theoretically in terms of solutions of GR equations Earlier in
More informationLecture 12. Inflation. What causes inflation. Horizon problem Flatness problem Monopole problem. Physical Cosmology 2011/2012
Lecture 1 Inflation Horizon problem Flatness problem Monopole problem What causes inflation Physical Cosmology 11/1 Inflation What is inflation good for? Inflation solves 1. horizon problem. flatness problem
More informationCosmology. Chapter 18. Cosmology. Observations of the Universe. Observations of the Universe. Motion of Galaxies. Cosmology
Cosmology Chapter 18 Cosmology Cosmology is the study of the structure and evolution of the Universe as a whole How big is the Universe? What shape is it? How old is it? How did it form? What will happen
More informationWhat is cosmic inflation? A short period of fast expansion, happening very early in the history of the Universe. Outline.
Outline Covers chapters 1 & 11 in Ryden Grand Unification Grand Unification II Gravity? Theory of Everything? Strong force Weak force EM t Planck : ~1-43 s t GUT : ~1-36 s t EW : ~1-12 s t Phase Transitions
More informationChapter 18. Cosmology. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 18 Cosmology Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cosmology Cosmology is the study of the structure and evolution of the Universe as a whole
More information3. It is expanding: the galaxies are moving apart, accelerating slightly The mystery of Dark Energy
II. Cosmology: How the universe developed Outstanding features of the universe today: 1. It is big, and full of galaxies. 2. It has structure: the galaxies are clumped in filaments and sheets The structure
More informationLecture 37 Cosmology [not on exam] January 16b, 2014
1 Lecture 37 Cosmology [not on exam] January 16b, 2014 2 Structure of the Universe Does clustering of galaxies go on forever? Looked at very narrow regions of space to far distances. On large scales the
More informationChapter 29. The Hubble Expansion
Chapter 29 The Hubble Expansion The observational characteristics of the Universe coupled with theoretical interpretation to be discussed further in subsequent chapters, allow us to formulate a standard
More informationAstronomy 182: Origin and Evolution of the Universe
Astronomy 182: Origin and Evolution of the Universe Prof. Josh Frieman Lecture 13 Nov. 20, 2015 Today Particle Physics & the Early Universe Baryogenesis The Inflationary Scenario Assignments Today: Essay
More informationInflation. By The amazing sleeping man, Dan the Man and the Alices
Inflation By The amazing sleeping man, Dan the Man and the Alices AIMS Introduction to basic inflationary cosmology. Solving the rate of expansion equation both analytically and numerically using different
More informationAbout the format of the literature report
About the format of the literature report Minimum 3 pages! Suggested structure: Introduction Main text Discussion Conclusion References Use bracket-number (e.g. [3]) or author-year (e.g. Zackrisson et
More informationAstronomy 162, Week 10 Cosmology Patrick S. Osmer Spring, 2006
Astronomy 162, Week 10 Cosmology Patrick S. Osmer Spring, 2006 Information Makeup quiz Wednesday, May 31, 5-6PM, Planetarium Review Session, Monday, June 5 6PM, Planetarium Cosmology Study of the universe
More informationContents. Part I The Big Bang and the Observable Universe
Contents Part I The Big Bang and the Observable Universe 1 A Historical Overview 3 1.1 The Big Cosmic Questions 3 1.2 Origins of Scientific Cosmology 4 1.3 Cosmology Today 7 2 Newton s Universe 13 2.1
More informationThe first 400,000 years
The first 400,000 years All about the Big Bang Temperature Chronology of the Big Bang The Cosmic Microwave Background (CMB) The VERY early universe Our Evolving Universe 1 Temperature and the Big Bang
More informationWhat forms AGN Jets? Magnetic fields are ferociously twisted in the disk.
What forms AGN Jets? Magnetic fields are ferociously twisted in the disk. Charged particles are pulled out of the disk and accelerated like a sling-shot. Particles are bound to the magnetic fields, focussed
More informationChapter 22 Reading Quiz Clickers. The Cosmic Perspective Seventh Edition. The Birth of the Universe Pearson Education, Inc.
Reading Quiz Clickers The Cosmic Perspective Seventh Edition The Birth of the Universe 22.1 The Big Bang Theory What were conditions like in the early universe? How did the early universe change with time?
More informationThe Standard Big Bang What it is: Theory that the universe as we know it began billion years ago. (Latest estimate: 13:7 ± 0:2 billion years!) I
The Standard Big Bang What it is: Theory that the universe as we know it began 13-15 billion years ago. (Latest estimate: 13:7 ± 0:2 billion years!) Initial state was a hot, dense, uniform soup of particles
More informationDark Matter and Energy
Dark Matter and Energy The gravitational force attracting the matter, causing concentration of the matter in a small space and leaving much space with low matter concentration: dark matter and energy.
More informationWhat is the 'cosmological principle'?
What is the 'cosmological principle'? Modern cosmology always starts from this basic assumption the Universe is homogeneous and isotropic. This idea seems strange there's empty space between me and the
More informationThe Big Bang The Beginning of Time
The Big Bang The Beginning of Time What were conditions like in the early universe? The early universe must have been extremely hot and dense Photons converted into particle-antiparticle pairs and vice-versa
More informationRapid Inflation of the Early Universe. 27. Exploring the Early Universe. The Isotropy Problem. Possible Causes of Cosmic Inflation
27. Exploring the Early Universe Rapid inflation of the early Universe Mass & energy formed during inflation Most matter & antimatter annihilated each other Neutrinos & helium are primordial fireball relics
More informationChapter 22 Back to the Beginning of Time
Chapter 22 Back to the Beginning of Time Expansion of Universe implies dense, hot start: Big Bang Back to the Big Bang The early Universe was both dense and hot. Equivalent mass density of radiation (E=mc
More informationLecture 12 Cosmology III. Inflation The beginning?
Lecture 12 Cosmology III Inflation The beginning? Unsolved issues in the standard model Horizon problem: Why is the CMB so smooth? The flatness problem: Why is Ω~1? Why is the universe flat? The structure
More informationThe Standard Big Bang What it is: Theory that the universe as we know it began billion years ago. (Latest estimate: 13:82 ± 0:05 billion years!)
The Standard Big Bang What it is: Theory that the universe as we know it began 13-14 billion years ago. (Latest estimate: 13:82 ± 0:05 billion years!) Initial state was a hot, dense, uniform soup of particles
More informationOUSSEP Final Week. If we run out of time you can look at uploaded slides Pearson Education, Inc.
OUSSEP Final Week Last week hopefully read Holiday-Week 23rd November Lecture notes Hand in your Hubble Deep Field Reports today! (If not today then in my mail box @ International College.) Today we will
More informationThe oldest science? One of the most rapidly evolving fields of modern research. Driven by observations and instruments
The oldest science? One of the most rapidly evolving fields of modern research. Driven by observations and instruments Intersection of physics (fundamental laws) and astronomy (contents of the universe)
More informationPOST-INFLATIONARY HIGGS RELAXATION AND THE ORIGIN OF MATTER- ANTIMATTER ASYMMETRY
POST-INFLATIONARY HIGGS RELAXATION AND THE ORIGIN OF MATTER- ANTIMATTER ASYMMETRY LOUIS YANG ( 楊智軒 ) UNIVERSITY OF CALIFORNIA, LOS ANGELES (UCLA) DEC 27, 2016 NATIONAL TSING HUA UNIVERSITY OUTLINE Big
More informationLecture 24: Cosmology: The First Three Minutes. Astronomy 111 Monday November 27, 2017
Lecture 24: Cosmology: The First Three Minutes Astronomy 111 Monday November 27, 2017 Reminders Last star party of the semester tomorrow night! Online homework #11 due Monday at 3pm The first three minutes
More informationHomework 6 Name: Due Date: June 9, 2008
Homework 6 Name: Due Date: June 9, 2008 1. Where in the universe does the general expansion occur? A) everywhere in the universe, including our local space upon Earth, the solar system, our galaxy and
More informationAstro 507 Lecture 28 April 2, 2014
Astro 507 Lecture 28 April 2, 2014 Announcements: PS 5 due now Preflight 6 posted today last PF! 1 Last time: slow-roll inflation scalar field dynamics in an expanding universe slow roll conditions constrain
More informationThe Big Bang Theory, General Timeline. The Planck Era. (Big Bang To 10^-35 Seconds) Inflationary Model Added. (10^-35 to 10^-33 Of A Second)
The Big Bang Theory, General Timeline The Planck Era. (Big Bang To 10^-35 Seconds) The time from the exact moment of the Big Bang until 10^-35 of a second later is referred to as the Planck Era. While
More informationAssignments. Read all (secs ) of DocOnotes-cosmology. HW7 due today; accepted till Thurs. w/ 5% penalty
Assignments Read all (secs. 25-29) of DocOnotes-cosmology. HW7 due today; accepted till Thurs. w/ 5% penalty Term project due last day of class, Tues. May 17 Final Exam Thurs. May 19, 3:30 p.m. here Olber
More informationCosmology. Big Bang and Inflation
Cosmology Big Bang and Inflation What is the Universe? Everything we can know about is part of the universe. Everything we do know about is part of the universe. Everything! The Universe is expanding If
More informationMASAHIDE YAMAGUCHI. Quantum generation of density perturbations in the early Universe. (Tokyo Institute of Technology)
Quantum generation of density perturbations in the early Universe MASAHIDE YAMAGUCHI (Tokyo Institute of Technology) 03/07/16@Symposium: New Generation Quantum Theory -Particle Physics, Cosmology, and
More informationAgenda. Chapter 17. Cosmology. Cosmology. Observations of the Universe. Observations of the Universe
Agenda Chapter 17 3/17/09 Measure Solar Altitude is it really 2pm? Announce: Observation: Tue March 24 Test 2: Tue March 24 Online stuff due by Test 2 Ch. 17 Cosmology Labwork: Hubble s Law & Large Scale
More informationCH 14 MODERN COSMOLOGY The Study of Nature, origin and evolution of the universe Does the Universe have a center and an edge? What is the evidence
CH 14 MODERN COSMOLOGY The Study of Nature, origin and evolution of the universe Does the Universe have a center and an edge? What is the evidence that the Universe began with a Big Bang? How has the Universe
More information26. Cosmology. Significance of a dark night sky. The Universe Is Expanding
26. Cosmology Significance of a dark night sky The Universe is expanding The Big Bang initiated the expanding Universe Microwave radiation evidence of the Big Bang The Universe was initially hot & opaque
More informationA100 Exploring the Universe Big Bang Theory and the Early Universe. Martin D. Weinberg UMass Astronomy
A100 Exploring the Universe and the Martin D. Weinberg UMass Astronomy astron100-mdw@courses.umass.edu December 02, 2014 Read: Chap 23 12/04/14 slide 1 Assignment on Chaps 22 23, at the end of next week,
More informationLecture 05. Cosmology. Part I
Cosmology Part I What is Cosmology Cosmology is the study of the universe as a whole It asks the biggest questions in nature What is the content of the universe: Today? Long ago? In the far future? How
More informationLecture 36: The First Three Minutes Readings: Sections 29-1, 29-2, and 29-4 (29-3)
Lecture 36: The First Three Minutes Readings: Sections 29-1, 29-2, and 29-4 (29-3) Key Ideas Physics of the Early Universe Informed by experimental & theoretical physics Later stages confirmed by observations
More informationWhat is the evidence that Big Bang really occurred
What is the evidence that Big Bang really occurred Hubble expansion of galaxies Microwave Background Abundance of light elements but perhaps most fundamentally... Darkness of the night sky!! The very darkness
More informationChapter 27 The Early Universe Pearson Education, Inc.
Chapter 27 The Early Universe Units of Chapter 27 27.1 Back to the Big Bang 27.2 The Evolution of the Universe More on Fundamental Forces 27.3 The Formation of Nuclei and Atoms 27.4 The Inflationary Universe
More informationThe cosmological constant puzzle
The cosmological constant puzzle Steven Bass Cosmological constant puzzle: Accelerating Universe: believed to be driven by energy of nothing (vacuum) Vacuum energy density (cosmological constant or dark
More informationThe early and late time acceleration of the Universe
The early and late time acceleration of the Universe Tomo Takahashi (Saga University) March 7, 2016 New Generation Quantum Theory -Particle Physics, Cosmology, and Chemistry- @Kyoto University The early
More informationAstroparticle physics the History of the Universe
Astroparticle physics the History of the Universe Manfred Jeitler and Wolfgang Waltenberger Institute of High Energy Physics, Vienna TU Vienna, CERN, Geneva Wintersemester 2016 / 2017 1 The History of
More informationLecture 20 Cosmology, Inflation, dark matter
The Nature of the Physical World November 19th, 2008 Lecture 20 Cosmology, Inflation, dark matter Arán García-Bellido 1 News Exam 2: good job! Ready for pick up after class or in my office Average: 74/100
More informationLecture #24: Plan. Cosmology. Expansion of the Universe Olber s Paradox Birth of our Universe
Lecture #24: Plan Cosmology Expansion of the Universe Olber s Paradox Birth of our Universe Reminder: Redshifts and the Expansion of the Universe Early 20 th century astronomers noted: Spectra from most
More informationArchaeology of Our Universe YIFU CAI ( 蔡一夫 )
Archaeology of Our Universe YIFU CAI ( 蔡一夫 ) 2013-11-05 Thermal History Primordial era 13.8 billion years by WMAP/NASA Large Scale Structure (LSS) by 2MASS Cosmic Microwave Background (CMB) by ESA/Planck
More informationCosmology. Thornton and Rex, Ch. 16
Cosmology Thornton and Rex, Ch. 16 Expansion of the Universe 1923 - Edwin Hubble resolved Andromeda Nebula into separate stars. 1929 - Hubble compared radial velocity versus distance for 18 nearest galaxies.
More informationChapter 26: Cosmology
Chapter 26: Cosmology Cosmology means the study of the structure and evolution of the entire universe as a whole. First of all, we need to know whether the universe has changed with time, or if it has
More informationConnecting Quarks to the Cosmos
Connecting Quarks to the Cosmos Institute for Nuclear Theory 29 June to 10 July 2009 Inflationary Cosmology II Michael S. Turner Kavli Institute for Cosmological Physics The University of Chicago Michael
More informationJohn Ellison University of California, Riverside. Quarknet 2008 at UCR
Overview of Particle Physics John Ellison University of California, Riverside Quarknet 2008 at UCR 1 Particle Physics What is it? Study of the elementary constituents of matter And the fundamental forces
More informationOrigin of the Universe - 2 ASTR 2120 Sarazin. What does it all mean?
Origin of the Universe - 2 ASTR 2120 Sarazin What does it all mean? Fundamental Questions in Cosmology 1. Why did the Big Bang occur? 2. Why is the Universe old? 3. Why is the Universe made of matter?
More informationThe Cosmic Microwave Background
The Cosmic Microwave Background The Cosmic Microwave Background Key Concepts 1) The universe is filled with a Cosmic Microwave Background (CMB). 2) The microwave radiation that fills the universe is nearly
More informationThe first one second of the early universe and physics beyond the Standard Model
The first one second of the early universe and physics beyond the Standard Model Koichi Hamaguchi (University of Tokyo) @ Colloquium at Yonsei University, November 9th, 2016. Credit: X-ray: NASA/CXC/CfA/M.Markevitch
More information