Origin of the Universe - 2 ASTR 2120 Sarazin. What does it all mean?

Transcription

1 Origin of the Universe - 2 ASTR 2120 Sarazin What does it all mean?

2 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? 4. Why is the Universe homogeneous? 5. Why is the Universe inhomogeneous?

3 Standard Model Particles

4 Forces and Gauge Symmetries Gravity Principle of Equivalence: Gravity = Acceleration locally Relativity gauge symmetry Electromagnetism Quantum mechanics, wavefunction Ψ Ψ e iφ Unitarity Weak force Isotopic Spin p Strong force Color symmetry n

5 Crystal Symmetry Breaking (cont.) cool homogeneous (hot) hot symmetry phase change crystal: forces link atoms cool broken symmetry phase change potential energy release

6 Unification: Super Symmetry At high temperatures, one super symmetry all forces, all particles are the same At lower temperatures, broken symmetry four forces, different particles Electromagnetic + Weak electroweak force T ~ K (Weinberg-Salam) EM, Weak, Strong leptoquark force T ~ K EM, Weak, Strong, Gravity Super Symmetry T ~ K (SUSY)

7 Super Symmetry (SUSY) Includes other gauge symmetries, plus: fermions bosons every fermion has a boson partner every boson has a fermion partner

8 Super Symmetry (SUSY) Wino - somebody give this guy a drive home!

9 Super Symmetry (SUSY)

10 Super Symmetry (SUSY) New conserved quantity, R parity R ( 1) 2S+3B+ L S spin B baryon number 1 ( 3 N N ) quarks anti quarks L lepton number N leptons N anti leptons R = +1 for standard model particles R = -1 for supersymmetric partner particles

11 R Parity Examples Particle S B L 2S+3B+L R electron 1/ photon u quark 1/2 1/ proton 1/ pion R 1 ( ) 2S+3B+L Particles have R=+1

12 R Parity Examples Particle S B L 2S+3B+L R electron 1/ positron 1/ proton 1/ antiproton 1/ R 1 ( ) 2S+3B+L Anti-particles have R=+1

13 R Parity Examples Particle S B L 2S+3B+L R electron 1/ selectron photon photino 1/ R 1 ( ) 2S+3B+L Super-particles have R= 1

14 Super Symmetry (SUSY) New conserved quantity, R parity R ( 1) 2S+3B+ L S spin B baryon number 1 ( 3 N N ) quarks anti quarks L lepton number N leptons N anti leptons R = +1 for standard model particles R = -1 for supersymmetric partner particles

15 Lightest Supersymmetric Particle (LSP) Lightest supersymmetric particle (LSP) must be stable since 1) Cannot decay to SUSY particle since all are heavier 2) Cannot decay to standard model particles since LSP has R = -1 and all SM particles have R = +1 Main candidates are gravitino, neutralino = (photino, zino, higgsino) & perhaps sneutrinos All interact only by weak and gravitational interactions Ideal Dark Matter candidates if produced copiously in Big Bang and mass is right.

16 Axions Another particle outside of the standard model is the axion Associated with symmetry which keeps the strong interaction from violating CP invariance Weakly interacting, light (10-6 to 1 ev), produced in Big Bang Candidate Dark Matter particles Also, super-partners (axino, saxino) might be LSP, also Dark Matter candidates

17 Unification: Super Symmetry

18 Strength of Forces

19 In the beginning... Universe begun with supersymmetry forces symmetry breaking Universe is a crystal of broken supersymmetry supersymmetry Crystal of broken symmetry

20 Fundamental Answers in Cosmology (?) 1. Why did the Big Bang occur? Universe supersymmetry forces broken symmetry Known Universe crystal of broken symmetry Release of potential energy lots of energy explosive expansion

21 Fundamental Answers in Cosmology (?) 1. Why did the Big Bang occur? 2. Why is the Universe old? T (SUSY) ~ K ~ T(protons) Gravity breaks off early, now very weak Gravity too weak to stop expansion

22 Fundamental Answers in Cosmology (?) 1. Why did the Big Bang occur? 2. Why is the Universe old? 3. Why is the Universe made of matter? t ~ sec, T ~ K (?) matter-antimatter symmetry broken

23 Fundamental Answers in Cosmology (?) 1. Why did the Big Bang occur? 2. Why is the Universe old? 3. Why is the Universe made of matter?

24 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? d = c t H d = c t H d = 2 c t H cannot mix

25 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? Symmetry breaking large release of energy vacuum energy rapid, accelerated expanion of Universe ** Inflation **

26 Inflation

27 Inflation Cosmological const. soln, large Ω Λ Eqn. of Cosmic Dynamics d(r /r 0 ) dt Ω = H M 0 (r /r 0 ) + K 2 c 2 + Ω 2 Λ (r /r 0 ) 2 H 0 "0" start of inflation rather than now, label "i" Big cosmological constant, Ω Λ >> Ω M, K 2 c 2 d(r /r i ) dt = H i Ω Λ 1/2 (r /r i ) (r /r i ) = exp H i Ω Λ 1/2 t H i Ω Λ 1/2 t ~ 100 ( ) r exp(100)r i ~ r i 1/2 H i 2

28 Inflation

29 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? Symmetry breaking large release of energy vacuum energy rapid, accelerated expanion of Universe Inflation Universe was much smaller before inflation, could be mixed

30 Inflation

31 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? Symmetry breaking large release of energy vacuum energy rapid, accelerated expanion of Universe Inflation Universe was much smaller before inflation, could be mixed

32 Inflation = Space Nearly Flat Inflation radius of curvature becomes very large space flat K = 0

33 Inflation = Space Nearly Flat Inflation radius of curvature becomes very large space flat K = 0

34 Planck 2015 Cosmology (H 0 = 71 km/sec/mpc) Ω M = 0.28 Ω Λ = % Dark Energy, 24% Dark Matter, 4% Baryons Flat Universe Ω M + Ω Λ = (±0.005) Accelerating Universe, will expand forever (?) Age of Universe t 0 = 13.8 billion years

35 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? 5. Why is the Universe inhomogeneous? Quantum fluctuations in early Universe plus Inflation

36 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? 5. Why is the Universe inhomogeneous? Quantum fluctuations in early Universe plus Inflation

37 Fundamental Answers (Cont.) 4. Why is the Universe homogeneous? 5. Why is the Universe inhomogeneous? Quantum fluctuations (big fluctuations, small sizes) in early Universe plus Inflation long wavelength but small density fluctuations at recombination make structure in Universe Predicts correct relation of density and size to make structures today, agrees with WMAP

38 Early History of Universe 1. Planck epoch (t < s, T > K) t Pl G! c 5 = s Planck time Supersymmetry, all forces the same, quantum gravity

39 Early History of Universe 1. Planck epoch (t < s, T > K) 2. Supersymmetry breaking (t ~ s, T ~ K) Gravity separate from lepto-quark force 3. Grand Unification (Lepto-Quark) epoch (10-43 < t < s, > T > K) Strong, EM, weak force unified, gravity weaker

40 Early History of Universe 4. Lepto-Quark symmetry breaking (t ~ s, T ~ K) Strong force separate from electro-weak force 5. Inflation epoch (10-35 < t < s, > T > K)?? Exponential inflation of Universe, curvature è 0, homogeneous universe, density fluctations Electro-weak epoch (10-35 < t < s, > T > K) EM and Weak forces unified Matter-antimatter asymmetry created?

41 Early History of Universe 6. Electro-Weak Symmetry breaking (t ~10-12 s, T ~ K) All four forces now separate 7. Quark-Gluon epoch (10-12 < t < 10-6 s, > T > K) Free quarks, quark-gluon plasma No hadrons (e.g., protons and neutrons)

42 Early History of Universe 8. Hadron Epoch (10-6 s < t, T < K) Protons, neutrons form Antimatter annihilates Unstable particles decay Nucleosynthesis, radiation dominated era, matter dominated, recombination, dark energy expansion

43 Fundamental Questions in Cosmology 1. Why did the Big Bang occur? þ 2. Why is the Universe old? þ 3. Why is the Universe made of matter? þ 4. Why is the Universe homogeneous? þ 5. Why is the Universe inhomogeneous? þ Quantum field theory, supersymmetry, and inflation explain the origin of the Universe?

44 Gravity Supersymmetry provides possible route to quantum theory of gravity But General Relativity: gravity is due to curvature of spacetime Are these inconsistent?

45 Geometry Revisited General Relativity Gravity = curvature of 4-dimensional space time Klein-Kalusa (1921) Add 5th dimension, curvature = electromagnetism 5th dimension very small, loop String Theory (M theory) Universe has 11 dimensions (10 space, 1 time) Curvature gives all forces Universe only expanded in 4 dimensions (3 space, 1 time) Others remained small (~10-33 cm) but not zero

46 String Theory Particles (points) become small vibrating strings Avoids infinities as well Different vibrations give different particles

47 Vibrating String

48 String Theory Are gauge supersymmetry theories and string theory different solutions? Holographic Principle (Duality): Information in N-dimensional space lower dimensional boundary of space (gauge field)

49 String Theory Hologram: 3-D information on a place is encoded into 2-D surface of film

50 String Theory Hologram: 3-D information on a place is encoded into 2-D surface of film as wave patterns

51 String Theory Hologram: 3-D information on a place is encoded into 2-D surface of film as wave patterns

52 String Theory Hologram: 3-D information on a place is encoded into 2-D surface of film

53 Holographic Principle (Duality) Real curvature of higher dimension space can be encoded in complex wavefunctions (gauge field theory) on lower dimensional boundary of space Curvature in space (real) Gauge field on surface (complex)

54 String Theory Are gauge supersymmetry theories and string theory different solutions? Holographic Principle: Information in N-dimensional space lower dimensional boundary of space (gauge field) (String theory on anti-desitter space = conformal field theory on lower dimensional boundary) String theory in N-dimensional space SUSY gauge theory in 4-d spacetime?

55 Cosmology