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Bingbang, Inflation

Bingbang, Inflation. and. Quantum Cosmology. Misao Sasaki. Message of this lecture. Bing Bang Universe. ・・・ confirmed. Inflationary Universe. ・・・ probably correct. Quantum Gravity/Cosmology. ・・・ in progress. Two major theories in modern physics. General Relativity

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Bingbang, Inflation

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  1. Bingbang, Inflation and Quantum Cosmology Misao Sasaki

  2. Message of this lecture • Bing Bang Universe ・・・ confirmed • Inflationary Universe ・・・ probably correct • Quantum Gravity/Cosmology ・・・ in progress

  3. Two major theories in modern physics • General Relativity gravity = space-time geometry black hole expanding universe • Quantum Mechanics “vacuum” fluctuations quantum tunneling matter = particle-wave complementarity Unification of the two theories = most challenging problem in modern physics Quantum Gravity key to origin of the Universe

  4. Einstein’s General Relativity Albert Einstein (1915) Gravitation = Geometry of space-time spacetime curvature energy-momentum density of matter G = 6.7×10-11 Nm2 /kg2(gravitational constant) c = 3×108 m/sec (velocity of light)

  5. Cosmological principle(Copernican principle) Universe looks the same everywhere in every direction homogeneity isotropy homogeneous & isotropic space open flat closed angle < 180o angle = 180o angle > 180o

  6. Friedmann equation Friedmann (1922) Expansion rate of the Universe a Space expands!

  7. Discovery of “Hubble’s Law” galaxies more distant recede faster Edwin Hubble (1929) 140 km/s 2 Mpc 140 km/s 2 Mpc our galaxy 1 Mpc = 3 Million light years (Mly) 1 Mpc 70 km/s expansion rate today:H0 = 70 km/s/Mpc

  8. Large scale structure of the Universe seeing far ＝ seeing past 30,000 ｋｍ/s Hubble’s observation 1Gly (300Mpc) size of observable universe: 10Gly (light velocity ＝ 300,000 km/sec)

  9. Birth of the Universe Big Bang ! Gamov’s fire ball cosmology (1940’s) Universe was small in the past. No galaxies, no stars １4 Gyrs ago Matter distributed uniformly in space extremely high temperature, high density George Gamow

  10. Penzias & Wilson (1965) Discovery of Cosmic Microwave Background (CMB) noise in radio wave from all directions of sky Radiation from deep space; from high temperature era of the Universe seeing far = seeing past ! Wilson and Penzias

  11. Extremely Brief History of the Universe • Hot soup of photons and elementary particles • Nucleosynthesis in the first 3 minutes: 4He, D, 7Li,... big bang • Clear-up (neutralization) at 380,000 yrs after birth • Formation of stars & galaxies > 1 Gyr after birth

  12. Proton Electron QSOs galaxy Clear-up of the Universe 380,000 yrs after big bang Ionized Plasma neutralization of Proton (+) & Electron ( - ) ⇒ photons are not scattered any more C M B clear-up Big Bang time 14 Gyr 1 Gyr 10 Gyr

  13. If we observe sky at visible frequency band, (~500,000 GHz) we see surface of clouds (Last Scattering Surface) at radio frequency (~100 GHz) we see surface of cosmic clear-up ＝LSS of CMB (380,000 yrs old Universe)

  14. Cosmological Redshift Cosmic Expansion l ∝ size of the Universe l Light once very blue became redder and redder, even redder than Infra Red, and became micro (Radio) waves today

  15. CMB Planck distribution Purest Planck distribution in nature “thermal spectrum”

  16. Before Big Bang ? Alan Guth Katsuhiko Sato Andrei Linde Theory of Inflationary Universe (1980~) accelerated expansion due tovacuum energy

  17. What is “vacuum” energy? • false vacuum absence of any matter, but ‘space’ itself contains potential energy (vacuum energy) energy density remains the same even if space expands total energy = (energy density) x (volume) huge energy is produced by expansion

  18. baby universe Cosmic Inflation observable size of the Universe looks perfectly smooth & flat x 1030 or more explains “homogeneity” & “flatness” birth of mega-size universe quantum vacuum fluctuations are also stretched to mega scales and they become seeds for formation of stars and galaxies

  19. cold universe hot universe Birth of Big Bang Universe Whole vacuum energy is converted to heat birth of matter (quarks, electrons, neutrinos, ...) & radiation (photons) ~ 10-34 sec old universe proton = 3 quarks ~ 1028 K

  20. Evidence for Inflation predictions • Universe after inflation is extremely flat. • Microscopic quantum vacuum fluctuations grow to • macroscopic density fluctuations to form galaxies. These fluctuations leave distinguishable imprints on CMB temperature fluctuations Predictions agree perfectly with observation

  21. Map of 380,000 yrs old Universe(Last Scattering Surface) by WMAP satellite Temperature is highly uniform If we magnify fluctuations by 100,000 times If the Universe were100 yrs old, this was 1 day old Universe Temperature T is slightlyhigher inRed regions, while it is slightlylower in Blue regions

  22. CMB anisotropy power spectrum theory WMAP data This tells us a lot about the past and present of the Universe

  23. best-fit model (flat: K=0) no dark energy model (flat: K=0) no dark energy model (closed: K>0) Expansion of the Universe ··· Friedmann eqn. “dark” energy accelerated expansion

  24. Content of the Universe today Dark Energy ~ “vacuum” energy accelerated expansion of the Universe 96% of the Universe is unknown! Dark Matter large scale structure of the Universe Atoms stars, visible objects

  25. future of ＣＭＢ observation WMAP PLANCK (simulation) much better understanding of the Universe much finer CMB map but these are indirect evidence of inflation

  26. Proof of Quantum Gravity ! End of Inflation (10-34 sec old) GWs EM waves clear-up of Universe (350,000 yrs old) Direct evidence? • vacuum fluctuations of spacetime grow to macroscopic • gravitational waves which propagate until today Gravitational Waves = “final” frontier of Astronomy

  27. Penrose Hawking Universe before inflation? Hawking-Penrose singularity theorem (1970) Universe has a finite past beginning of the Universe = space-time singularity? physical laws break down at singularity! General Relativity is inapplicable quantum gravity is needed

  28. Quantum Cosmology Quantum Gravity • Quantum theory of Space-time • Quantum gravity is still in its infancy • Superstring theory, M-theory, loop quantum gravity, .... Quantum mechanics of cosmic scale factor: a(t) • quantum approach to the birth of the Universe • first step toward full quantum gravity

  29. Tunneling - characteristic of quantum theory - classical theory particle cannot penetrate the barrier quantum theory probability wave permeates through the barrier “probability wave” of a particle

  30. Uncertainty Principle vacuum fluctuations - characteristic of quantum field theory - • vacuum is not a quiet empty space of nothing • elementary particles are randomly created and annihilated • at microscopic scales Planck Constant smaller the sizeL , larger the energyE

  31. Planck length: Planck energy: Planck Scale At scale L ~ 10-33cm, energy fluctuations become so large that even spacetime geometry is no longer smooth at all. (~ power consumed by a family / month)

  32. J.A. Wheeler spacetime foam World of Quantum Gravity black holes and worm holes are violently created and annihilated at scales ~ 10-33 cm (Planck scale) • the whole Universe was in quantum state when its size was ~10-33 cm Universe (=spacetime) itself is probabilistic

  33. de Sitter spacetime solution of Einstein equation filled with vacuum energy (cosmological constant) contraction expansion R E minimum radius of the Universe R E barrier in the motion of radius of the Universe Rmin t time R can become smaller than Rmin in quantum theory

  34. Creation of the Universe from “nothing” Vilenkin (1982), Hawking, … born through quantum tunneling from R=0（nothing） barrier height barrier against “motion” of the Universe classical de Sitter solution quantum solution Vilenkin Radius quantum tunneling nothing

  35. Summary: from “nothing” to “something” • Universe might have been born out of “nothing”. • The baby Universe was perhaps of Planck size (10-33 cm). (research still at primitive stage) • inflation by vacuum energy to gigantic size. Then the • vacuum energy was converted to matter and radiation. Birth of hot (Big Bang) Universe (testing theory against observation) • nucleosynthesis, photon decoupling, star/galaxy formation, • solar system, birth of life, ....

  36. Future of the Universe? • if expands forever expansion rate decreases indefinitely Thermal death (empty space with dead stars & galaxies) expansion rate increases indefinitely Big Rip (everything will be ripped apart) expands at a constant rate Steady state (realization of “inflationary universe”) • if expansion stops • Universe eventually starts to contract • Big Crunch (everything will be crushed to a single point) End of the Universe? Beginning of a new Universe?

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