DOCSLIB.ORG

Topic 3 Evidence for the Big Bang

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Topic 3 Evidence for the Big Bang Topic 3 Primordial nucleosynthesis Evidence for the Big Bang ! Back in the 1920s it was generally thought that the Universe was infinite ! However a number of experimental observations started to question this, namely: • Red shift and Hubble’s Law • Olber’s Paradox • Radio sources • Existence of CMBR Red shift and Hubble’s Law ! We have already discussed red shift in the context of spectral lines (Topic 2) ! Crucially Hubble discovered that the recessional velocity (and hence red shift) of galaxies increases linearly with their distance from us according to the famous Hubble Law V = H0d where H0 = 69.3 ±0.8 (km/s)/Mpc and 1/H0 = Age of Universe Olbers’ paradox ! Steady state Universe is: infinite, isotropic or uniform (sky looks the same in all directions), homogeneous (our location in the Universe isn’t special) and is not expanding ! Therefore an observer choosing to look in any direction should eventually see a star ! This would lead to a night sky that is uniformly bright (as a star’s surface) ! This is not the case and so the assumption that the Universe is infinite must be flawed Radio sources ! Based on observations of radio sources of different strengths (so-called 2C and 3C surveys) ! The number of radio sources versus source strength concludes that the Universe has evolved from a denser place in the past ! This again appears to rule out the so-called Steady State Universe and gives support for the Big Bang Theory Cosmic Microwave Background ! CMBR was predicted as early as 1949 by Alpher and Herman (Gamow group) as a “remnant heat” left over from the very hot and dense initial Universe ! They predicted that after the Big Bang the Universe should “glow” in the gamma ray part of the spectrum ! This will subsequently cool as the Universe expands shifting the wavelength of this “last light” to a temperature of ~5K ! Eventually observed in 1965 by Penzias and Wilson ! The CMBR is now a very powerful tool for cosmologists ! Recent experiments such as COBE and WMAP have measured the CMBR anisotropies at the 10-5 level ! Gives us information on Big Bang, Dark Matter, etc. αβγ theory (Origin of Chemical Elements) ! Actually Alpher & Gamow: Bethe included (by Gamow) as a joke ! Proposed an early Universe that was hot and dense ! Assumed that the Early Universe consisted only of neutrons ! As the temperature fell neutron decay to protons was possible ! Subsequently they proposed a single process for all elemental abundances in the Universe - that of neutron capture - ! Protons via β-decay: n → p + e + νe ! First step: p + n → 2H + γ αβγ theory νe νe αβγ theory - abundances ! Successive neutron For these capture creates heavier calculations elements capture cross-sections ! At each step the progress measured at controlled by the balance Los Alamos between the rate of during World War II production and the rate of were used destruction (1 MeV ! By setting up and solving a neutrons sequence of differential =1010K) equations of this type, a distribution could be dNA/dt = F(S,T)[σ A-1NA-1 - σANA] produced in reasonable F is collision frequency (function of agreement with the trend of thermodynamic state variables) the observed abundances NA is the no. of atoms with atomic no. A σA is the neutron capture cross-section Cross-sections (quick revision) ! Consider the simple case in which a beam of particles is incident on nuclei of some type, then the cross-section is the probability of a particular process occurring per target nucleus, per incident particle ! The total area “blocked out” is the ! In neutron capture the rate at (number of nuclei per unit volume) x (the which the reaction is occurring volume) x (σ). Thus the fraction of the depends upon the relative beam which is removed by the reaction is: velocity v of the particles and target nuclei and is given by the dN/N = - nσ dx product of particle density, the relative velocity, the cross where n = number density x beam area section and the total number of Integration yields target nuclei. N = N exp(- nσx) ! We shall discuss neutron 0 capture further in understanding or N = N0 exp(- x /λ ) the production of elements where λ is the mean free path heavier than Iron αβγ theory - success and failure ! Abundance for He agrees well with observation ! By splitting the elements into 15 “groups” by atomic weight and using an average cross-section for each group gives a reasonable fit to abundance data ! BUT predicted abundances for heavier elements were incorrect ! Problem getting past A=4 due to lack of stable elements with A=5, 8 ! Results carved the way for calculations of thermonuclear fusion ! Discussion is relevant to neutron capture topic later This is an extract from the “Chart of nuclides” Big Bang: Underlying principles I ! Universe expanded some 14 billion years ago from a singularity ! At extremely high temperatures elementary particles can simply be created from thermal energy kT = mc2 (essentially E = mc2) ! After the BB the Universe expands and cools ! As temperatures fall below the threshold temperature for particle production then annilihilation rate > creation rate Big Bang; Underlying Principles II ! Normal physics laws (including standard model of particle physics) ! Small matter-antimatter asymmetry ! Gravitation described by General Relativity ! Cosmological principal (Universe is homeogeneous and isotropic) Robertson- Walker metric ! Expansion of the Universe is governed by field equations of GR The Big Bang Time Space Key events after Big Bang Time Temp/Energy Event 10-43 s kT = 1019 eV Planck era, quantum gravity, prior to this all forces one, gravity first to decouple, many exotic particles 10-35 s kT = 1015 eV Inflation starts, Strong nuclear force decouples 10-10 s T = 1015 K – Free electrons, quarks, photons, -10-4 s 1012 K neutrinos all strongly interacting 10-4 s T = 1012 K – Free electrons, protons, neutrons, -101 s 1010 K photons, neutrinos all strongly interacting Key events after Big Bang Time Temp/Energy Event 101 s T = 1010 K Neutrinos “decouple” from the cosmic plasma (cross-section falls dramatically) 102 s T = 7.5-6x109 K Pair production of e+e- ceases 102 s kT = 0.8 MeV Proton:neutron ratio is frozen Next Thermal energy still high enough 300 s to photodissociate atoms Neutron decay continues, n:p ratio changing Next Primordial nucleosynthesis starts 103 s Note ions not atoms due to mean thermal energy Key events after Big Bang Time Temp/Energy Event ~ 103 s T ~ 108 or 9 K “Dark ages”: Universe is a sea of to to free nuclei, electrons and photons. 400,000 T = 3000 K Photons Thomson scatter off years electrons so Universe remains opaque to photons. Physics in this period is less well-established. 380,000 T = 3000 K Photons can no longer ionize, years photons decouple, “last scattering surface”. Origin of CMBR. Fundamental forces Cosmic Microwave Background Cosmic Microwave Background Very close to a perfect thermal (Black Body) spectrum with a temperature of 2.7K The neutron:proton ratio ! The main 3 reactions involved in determining the number of protons and neutrons in the early Universe are: + (i) n + e p + νe (+ 1.8 MeV) - (ii) p + e (+0.8MeV) n + νe - (iii) n p + e + νe (+ 0.8 MeV) ! Note that reaction (ii) is endothermic in a left- right direction i.e. requires energy into the system (KE of incoming particles) in order to proceed The neutron:proton ratio ! At T > 1010 K, kT > 1 MeV, t < 1 s, reactions (i) and (ii) maintain protons and neutrons in thermal equilibrium • When kT >> mn – mp = Δm, protons and neutrons are nearly equal in number • When Δm becomes significant compared to kT, the neutron-proton ratio is given by the Boltzmann factor exp(−Δmc2/kT) ! At T ~ 1010 K, kT ~ 0.8 MeV, t ~ 1 s, the reaction rates for (i) and (ii) become slow compared to the expansion rate of the universe • neutrinos decouple (weak interaction rate slow compared to expansion rate) • e+e− pair creation suppressed (γ energies drop below 0.511 MeV) • neutron:proton ratio “freezes out” ! Below this temperature only reaction (iii) continues The neutron:proton ratio ! We use the Boltzmann distribution to estimate the n:p ratio at this point 2 3 $ mc ' N ∝ m 2 exp& − ) % kBT ( ! hence 3 " % 2 " 2 % Nn mn (mn − mp )c = $ ' exp$ − ' N p # mp & # kBT & € 2 ! where kT = 0.8 MeV and (mn - mp) = 1.3 MeV/c € This yields a value of Nn:Np ~ 0.2 Primordial nucleosynthesis ! At this point kT is too high p + n ⇔ 2H + γ for primordial 2H + 2H ⇔ 3He + n nucleosynthesis to start 2H + 2H ⇔ 3H + p (formation of nuclei) due 3 2 4 to dissociation H + H ⇔ He + n 3He + 2H ⇔ 4He + p ! Therefore reaction (iii) continues in the left-right 2H + 2H ⇔ 4He direction – this is neutron 3He + 4He ⇔ 7Be + γ decay 3H + 4He ⇔ 7Li + γ ! After a further 300 7Be + n ⇔ 7Li + p seconds primordial 7Li + p ⇔ 24He nucleosynthesis starts Note: ions not atoms Solved problem ! If the neutron:proton ratio starts at 0.2 and the neutron continues to decay for a further 300 seconds what is the neutron:proton ratio at the end of this period given that the neutron’s lifetime is 890 seconds? ! The neutron’s lifetime is 890 seconds therefore in 300 seconds: N $ t ' $ 300' = exp& − ) = exp& − ) = 0.714 N0 % τ ( % 890( ! Therefore the fraction of neutrons that have decayed = 0.286 ! Next we write N n (1− d) " % € Nn Nn (1− d) N p $ ' = = N N + dN Nn # p & t= 300s p n 1+ d N " % p Nn Nn where = 0.2 and d=0.286 to give $ ' = 0.135 N p N # p & t= 300s € € € Abundances vs time Note that a neutron:proton ratio of 0.135:1 is equivalent to 12:88 Assuming that the 12 neutrons go to forming 4He we would expect 76% Hydrogen (1H) and 24% Helium (4He) - in excellent agreement with observation Modern day abundances ! Comparison of modern day elemental abundances from primordial nucleosynthesis can also give important cosmological information such as the baryon density or the baryon to photon ratio ! Concordance with CMB is important check on theory Summary ! Big Bang Nucleosynthesis (BBNS) successfully predicts the production of light elements shortly after the Big Bang ! The thermal history of the early Universe and nuclear physics are used to explain the sequence of events ! Light element abundances can be accurately predicted and related to cosmological parameters .
Load more

Recommended publications
  • Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking
    W&M ScholarWorks Undergraduate Honors Theses Theses, Dissertations, & Master Projects 5-2016 Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking Matthew Ramin Hamedani Heffernan College of William and Mary Follow this and additional works at: https://scholarworks.wm.edu/honorstheses Part of the Nuclear Commons Recommended Citation Heffernan, Matthew Ramin Hamedani, "Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking" (2016). Undergraduate Honors Theses. Paper 974. https://scholarworks.wm.edu/honorstheses/974 This Honors Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Undergraduate Honors Theses by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking Matthew Heffernan Advisor: Andr´eWalker-Loud Abstract We perform a quantitative study of the sensitivity of Big Bang Nucleosynthesis (BBN) to the two sources of isospin breaking in the Standard Model (SM), the split- 1 ting between the down and up quark masses, δq (md mu) and the electromagnetic ≡ 2 − coupling constant, αf:s:. To very good approximation, the neutron-proton mass split- ting, ∆m mn mp, depends linearly upon these two quantities. In turn, BBN is very ≡ − sensitive to ∆m. A simultaneous study of both of these sources of isospin violation had not yet been performed. Quantifying the simultaneous sensitivity of BBN to δq and αf:s: is interesting as ∆m increases with increasing δq but decreases with increasing αf:s:. A combined analysis may reveal weaker constraints upon possible variations of these fundamental constants of the SM.
    [Show full text]
  • Arxiv:1707.01004V1 [Astro-Ph.CO] 4 Jul 2017
    July 5, 2017 0:15 WSPC/INSTRUCTION FILE coc2ijmpe International Journal of Modern Physics E c World Scientific Publishing Company Primordial Nucleosynthesis Alain Coc Centre de Sciences Nucl´eaires et de Sciences de la Mati`ere (CSNSM), CNRS/IN2P3, Univ. Paris-Sud, Universit´eParis–Saclay, Bˆatiment 104, F–91405 Orsay Campus, France [email protected] Elisabeth Vangioni Institut d’Astrophysique de Paris, UMR-7095 du CNRS, Universit´ePierre et Marie Curie, 98 bis bd Arago, 75014 Paris (France), Sorbonne Universit´es, Institut Lagrange de Paris, 98 bis bd Arago, 75014 Paris (France) [email protected] Received July 5, 2017 Revised Day Month Year Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the three evi- dences for the big bang model, together with the expansion of the universe and the Cos- mic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations, and calculated in primordial nucleosynthesis. However, there remains a yet–unexplained discrepancy of a factor ≈3, between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor by new observations. The precision in deuterium observations in cosmological clouds has recently improved dramatically, so that nuclear cross sections involved in deuterium BBN need to be known with similar precision. We will shortly discuss nuclear aspects re- lated to BBN of Li and D, BBN with non-standard neutron sources, and finally, improved sensitivity studies using Monte Carlo that can be used in other sites of nucleosynthesis.
    [Show full text]
  • Origin and Evolution of the Universe Baryogenesis
    Physics 224 Spring 2008 Origin and Evolution of the Universe Baryogenesis Lecture 18 - Monday Mar 17 Joel Primack University of California, Santa Cruz Post-Inflation Baryogenesis: generation of excess of baryon (and lepton) number compared to anti-baryon (and anti-lepton) number. in order to create the observed baryon number today it is only necessary to create an excess of about 1 quark and lepton for every ~109 quarks+antiquarks and leptons +antileptons. Other things that might happen Post-Inflation: Breaking of Pecci-Quinn symmetry so that the observable universe is composed of many PQ domains. Formation of cosmic topological defects if their amplitude is small enough not to violate cosmological bounds. There is good evidence that there are no large regions of antimatter (Cohen, De Rujula, and Glashow, 1998). It was Andrei Sakharov (1967) who first suggested that the baryon density might not represent some sort of initial condition, but might be understandable in terms of microphysical laws. He listed three ingredients to such an understanding: 1. Baryon number violation must occur in the fundamental laws. At very early times, if baryon number violating interactions were in equilibrium, then the universe can be said to have “started” with zero baryon number. Starting with zero baryon number, baryon number violating interactions are obviously necessary if the universe is to end up with a non-zero asymmetry. As we will see, apart from the philosophical appeal of these ideas, the success of inflationary theory suggests that, shortly after the big bang, the baryon number was essentially zero. 2. CP-violation: If CP (the product of charge conjugation and parity) is conserved, every reaction which produces a particle will be accompanied by a reaction which produces its antiparticle at precisely the same rate, so no baryon number can be generated.
    [Show full text]
  • 19. Big-Bang Cosmology 1 19
    19. Big-Bang cosmology 1 19. BIG-BANG COSMOLOGY Revised September 2009 by K.A. Olive (University of Minnesota) and J.A. Peacock (University of Edinburgh). 19.1. Introduction to Standard Big-Bang Model The observed expansion of the Universe [1,2,3] is a natural (almost inevitable) result of any homogeneous and isotropic cosmological model based on general relativity. However, by itself, the Hubble expansion does not provide sufficient evidence for what we generally refer to as the Big-Bang model of cosmology. While general relativity is in principle capable of describing the cosmology of any given distribution of matter, it is extremely fortunate that our Universe appears to be homogeneous and isotropic on large scales. Together, homogeneity and isotropy allow us to extend the Copernican Principle to the Cosmological Principle, stating that all spatial positions in the Universe are essentially equivalent. The formulation of the Big-Bang model began in the 1940s with the work of George Gamow and his collaborators, Alpher and Herman. In order to account for the possibility that the abundances of the elements had a cosmological origin, they proposed that the early Universe which was once very hot and dense (enough so as to allow for the nucleosynthetic processing of hydrogen), and has expanded and cooled to its present state [4,5]. In 1948, Alpher and Herman predicted that a direct consequence of this model is the presence of a relic background radiation with a temperature of order a few K [6,7]. Of course this radiation was observed 16 years later as the microwave background radiation [8].
    [Show full text]
  • A1143: History of the Universe, Autumn 2012 10. Big Bang
    A1143: History of the Universe, Autumn 2012 10. Big Bang Nucleosynthesis and the Cosmic Microwave Background Reading: Assuming that you have already read Chapter 5 and Sections 8.1-8.3 (go back to them if you haven’t), go on to read section 8.4. You can skip 8.5, which is a level of detail we won’t have time to get to. Then read Chapter 10. If you want to understand more about nuclear reactions, which is useful background, then read Chapter 9, especially 9.6; however, Chapter 9 is optional. The Big Bang Theory Recall the definition of the BBT I gave back in Section 5: The universe has expanded from a very hot, very dense state that existed at a finite time in the past (approximately 14 billion years ago). We are now in a position to be somewhat more specific in our definition, namely that the BBT assumes: (a) that the universe on large scales (roughly speaking, tens of millions of light years or more) can be approximated as homogeneous (b) that the expansion of the universe is governed by GR, given the matter and radiation (e.g., photons) present in the universe (c) that atoms and nuclei and radiation obeyed the same fundamental physical laws in the past that they do today. Together, assumptions (a) and (b) mean that the expansion factor a(t) follows the Friedmann equation given back in Section 8, according to which 4πG 3p a¨(t)= − × a(t) × ρ¯ + . 3 c2 Herea ¨(t) is a mathematical way of denoting “the acceleration of a at time t.” You should have an intuitive feel for what this means — if the acceleration is negative, then the expansion is slowing down — but don’t worry about the mathematical details.
    [Show full text]
  • Thermal History of the Universe and Big Bang Nucleosynthesis Cosmology Lecture (Chapter 8)
    thermal history of the universe and big bang nucleosynthesis cosmology lecture (chapter 8) Markus Possel¨ + Bjorn¨ Malte Schafer¨ Haus der Astronomie and Centre for Astronomy Fakultat¨ fur¨ Physik und Astronomie, Universitat¨ Heidelberg August 1, 2013 repetition thermal history of the universe synthesis observations summary outline 1 repetition 2 thermal history of the universe adiabaticity thermodynamical distributions freeze-out 3 synthesis stars spallation explosive big-bang 4 observations 5 summary Markus Possel¨ + Bjorn¨ Malte Schafer¨ thermal history of the universe and big bang nucleosynthesis repetition thermal history of the universe synthesis observations summary repetition • Friedmann-Lemaˆıtre cosmological models: • homogeneous and isotropic metric (Robertson-Walker line element) • homogeneous and ideal fluids, described by ρ and w • evolving metric, described by Hubble function H(a) ! distance measures, interesting features • geometrical measurements (SN distances) constrain densities • cosmological fluids, influence H(a) by their eos parameter w • preferred model: ΛCDM, flat and accelerating −4 • radiation Ων ' 10 • matter Ωm = 0:25 • curvature Ωk ' 0 • cosmological constant ΩΛ = 0:75 Markus Possel¨ + Bjorn¨ Malte Schafer¨ thermal history of the universe and big bang nucleosynthesis repetition thermal history of the universe synthesis observations summary thermal history of the universe • temperature of fluids drop while universe expands • 3 important stages • temperature is high enough to allow nuclear reactions ! big bang nucleosynthesis
    [Show full text]
  • Big Bang Nucleosynthesis and Physics Beyond the Standard Model
    OUTP-95-16P (rev) REVIEW ARTICLE Big Bang nucleosynthesis and physics beyond the Standard Model Subir Sarkar Department of Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, U.K. Abstract. The Hubble expansion of galaxies, the 2.73 K blackbody radiation background and the cosmic abundances of the light elements argue for a hot, dense origin of the universe — the standard Big Bang cosmology — and enable its evolution to be traced back fairly reliably to the nucleosynthesis era when the temperature was of O(1) MeV corresponding to an expansion age of O(1) sec. All particles, known and hypothetical, would have been created at higher temperatures in the early universe and analyses of their possible effects on the abundances of the synthesized elements enable many interesting constraints to be obtained on particle properties. These arguments have usefully complemented laboratory experiments in guiding attempts to extend physics beyond the Standard SU(3)c SU(2) U(1) Model, incorporating ideas such ⊗ L⊗ Y as supersymmetry, compositeness and unification. We first present a pedagogical account of relativistic cosmology and primordial nucleosynthesis, discussing both theoretical and observational aspects, and then proceed to examine such constraints in detail, in particular those pertaining to new massless particles and massive unstable particles. Finally, in a section aimed at particle physicists, we illustrate applications of such constraints to models of new physics. arXiv:hep-ph/9602260v2 15 Sep 1996 PACS numbers: 98.80.Cq 14.60.-z 14.80.-j 95.30.-Cq Short title: BBN and physics beyond the SM Submitted to: Institute of Physics Publishing February 1, 2008 Dedicated to Dennis Sciama on his 67th birthday † 2 Contents Page 1.
    [Show full text]
  • Big Bang Nucleosynthesis As a Probe of New Physics 3
    Big Bang Nucleosynthesis as a Probe of New Physics 1 Big Bang Nucleosynthesis as a Probe of New Physics Maxim Pospelov∗ Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5, Canada Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada Josef Pradler† Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5, Canada Key Words Big bang nucleosynthesis, early Universe, abundances of light elements, ex- tensions of the Standard Model, dark matter Abstract Big bang nucleosynthesis (BBN), an epoch of primordial nuclear transforma- tions in the expanding Universe, has left an observable imprint in the abundances of light elements. Precision observations of such abundances, combined with high-accuracy predic- tions, provide a nontrivial test of the hot big bang and probe non-standard cosmological and particle physics scenarios. We give an overview of BBN sensitivity to different classes arXiv:1011.1054v1 [hep-ph] 4 Nov 2010 of new physics: new particle or field degrees of freedom, time-varying couplings, decaying or annihilating massive particles leading to non-thermal processes, and catalysis of BBN by charged relics. CONTENTS INTRODUCTION .......................................... 2 Universe at redshift of a billion: basic assumptions and main stages of BBN ............. 4 NEW PHYSICS AFFECTING THE TIMING OF MAIN BBN EVENTS ........... 12 BBN with new degrees of freedom ..................................... 12 BBN with sliding couplings and mass scales. ..............................
    [Show full text]
  • Recombination and the Cosmic Microwave Background
    M. Pettini: Introduction to Cosmology | Lecture 9 RECOMBINATION AND THE COSMIC MICROWAVE BACKGROUND Once Big Bang Nucleosynthesis is over, at time t ∼ 300 s and tempera- ture T ∼ 8 × 108 K, the Universe is a thermal bath of photons, protons, helium nuclei, traces of other light elements, and electrons, in addition to neutrinos and the unknown dark matter particle(s). The energy density is dominated by the relativistic component, photons and neutrinos. With the exception of neutrinos and the dark matter which by this time have decoupled from the plasma, all particle species have the same temperature which is established by interactions of charged particles with the photons. Photons interacted primarily with electrons through Thomson scattering: γ + e− ! γ + e− i.e. the elastic scattering of electromagnetic radiation by a free charged particle. Thomson scattering is the low-energy limit of Compton scattering and is a valid description in the regime where the photon energy is much less than the rest-mass energy of the electron. In this process, the electron can be thought of as being made to oscillate in the electromagnetic field of the photon causing it, in turn, to emit radiation at the same frequency as the incident wave, and thus the wave is scattered. An important feature of Thomson scattering is that it introduces polarization along the direction of motion of the electron (see Figure 9.1). The cross-section for Thomson scattering is tiny: 2 2 1 e −25 2 σT = 2 2 = 6:6 × 10 cm (9.1) 6π0 mec and therefore Thomson scattering is most important when the density of free electrons is high, as in the early Universe or in the dense interiors of stars.1 1 Photons are also scattered by free protons, but σT for proton scattering is smaller by a factor 2 (me=mp) (eq.
    [Show full text]
  • 6.1 the Early Universe
    6.1 The Early Universe The Key Ideas • Pushing backward in time towards the Big Bang, the universe was hotter and denser in a fairly predictable manner (aside from surprising “glitches” such as the inflation…) • At any given time, the temperature translates into a characteristic mass of particles (kT ~ mc2), which dominate that epoch: the Universe as the ultimate accelerator? • As the energies increase, different physical regimes and different fundamental interactions come into play • The closer we get to the Big Bang (i.e., further away from the experimentally probed regime), the less certain the physics: the early Universe as the laboratory of physics beyond the standard model? • Our extrapolations must break down by the epoch of ~ 10 - 43 sec ~ Plack time, where the quantum gravity must be important 2 The Cosmic Thermal History … on a logarithmic time axis - a theorist’s delight! The Planck Era (from M. Turner) 3 Some Key Moments in the Thermal History of the Universe: • Planck era, t ~ 10 - 43 sec: quantum gravity, … ??? … • Inflation, t ~ 10 - 33 sec: vacuum phase transition, exponential expansion • Grand Unification, t ~ 10 - 32 sec: strong and electroweak interactions split • Baryogenesis , t ~ 10 - 6 sec: quark-hadron transition • Nucleosynthesis , t ~ 1 ms to 3 min: D, He, Li, Be form • Radiation to matter dominance transition, t ~ 10 5 yr: structure begins to form • Recombination, t ~ 380,000 yr: hydrogen becomes neutral, CMBR released, dark ages begin • Reionization, t ~ 0.3 - 1 Gyr: first galaxies and QSOs reionize the universe,
    [Show full text]
  • Dynamical Emergence of the Universe Into the False Vacuum, Arxiv:1510.05001V1 [Astro-Ph.CO] (See Arxiv Version V1)
    Prepared for submission to JCAP Dynamical Emergence of the Universe into the False Vacuum Johann Rafelski and Jeremiah Birrell Department of Physics, University of Arizona, Tucson, Arizona, 85721, USA Abstract. We study how the hot Universe evolves and acquires the prevailing vacuum state, demonstrating that in specific conditions which are believed to apply, the Universe becomes frozen into the state with the smallest value of Higgs vacuum field v = h , even if this is h i not the state of lowest energy. This supports the false vacuum dark energy Λ-model. Under several likely hypotheses we determine the temperature in the evolution of the Universe at which two vacuua v1, v2 can swap between being true and false. We evaluate the dynamical surface pressure on domain walls between low and high mass vaccua due to the presence of matter and show that the low mass state remains the preferred vacuum of the Universe. Keywords: particle physics-cosmology connection, cosmological phase transitions, dark en- ergy theory Contents 1 Introduction 2 2 Effective Potential in the Hot Universe 3 2.1 Higgs Effective Potential W (v) 3 2.2 Including Hot Matter in the SM Effective Potential 3 2.3 High Temperature Behavior: Capture in a False Vacuum 4 arXiv:1510.05001v2 [astro-ph.CO] 19 Nov 2015 2.4 Low Temperature Behavior 6 3 Swapping of True and False Vacuua 7 3.1 General consideration 8 3.2 Swap via lepton density 8 3.3 Dynamical Pressure on a Domain Wall 10 4 Discussion and Consequences 12 printed October 13, 2018 1 Introduction This work presents relatively simple arguments for why the cosmological evolution selects the vacuum with smallest Higgs VEV v = h which, in general, could be and likely is the ‘false’ h i vacuum.
    [Show full text]
  • Big-Bang Nucleosynthesis with Updated Nuclear Data
    Nuclear Physics in Astrophysics IV IOP Publishing Journal of Physics: Conference Series 202 (2010) 012001 doi:10.1088/1742-6596/202/1/012001 Big-Bang Nucleosynthesis with updated nuclear data Alain Coc Centre de Spectrom´etrie Nucl´eaire et de Spectrom´etrie de Masse (CSNSM), CNRS/IN2P3, Universit´eParis Sud 11, UMR 8609, Bˆatiment 104, F–91405 Orsay Campus, France E-mail: [email protected] Elisabeth Vangioni Institut d’Astrophysique de Paris, UMR-7095 du CNRS, Universit´ePierre et Marie Curie, 98 bis bd Arago, 75014 Paris (France) E-mail: [email protected] Abstract. Primordial nucleosynthesis is one of the three evidences for the Big-Bang model together with the expansion of the Universe and the Cosmic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations and calculated primordial nucleosynthesis. This comparison was used to determine the baryonic density of the Universe. For this purpose, it is now superseded by the analysis of the Cosmic Microwave Background (CMB) radiation anisotropies. Big-Bang nucleosynthesis remains, nevertheless, a valuable tool to probe the physics of the early Universe. However, the yet unexplained, discrepancy between the calculated and observed lithium primordial abundances, has not been reduced, neither by recent nuclear physics experiments, nor by new observations. 1. Introduction There are presently three evidences for the Big-Bang Model : the universal expansion, the Cosmic Microwave Background (CMB) radiation and Primordial or Big-Bang Nucleosynthesis (BBN). The third evidence for a hot Big-Bang comes from the primordial abundances of the “light elements”: 4He, D, 3He and 7Li.
    [Show full text]