yukawa institute for y tp theoretical … › oct20 public lecture...• universe might have been...
TRANSCRIPT
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Misao Sasaki
佐々木 節
Y TPYUKAWA INSTITUTE FOR
THEORETICAL PHYSICS
Let's Enjoy Science
20 Oct., 2013
We can now study these questions quantitatively
based on observational data
Era of Precision Cosmology 精密宇宙論の時代
Cosmology Today (現代の宇宙論) • Origin/Birth of the Universe (宇宙の誕生・起源)
Origin of Space-Time and Matter (時空と物質の起源)
• Evolution/Structure of the Universe (宇宙の進化と構造)
Dynamics of Space-Time/Gravity
(時空・重力のダイナミックス)
3 Cosmological principle (宇宙原理)
Universe looks the same everywhere in every direction
isotropy
等方
homogeneity
一様
open flat closed
angle < 180o angle = 180o angle > 180o
homogeneous & isotropic space
Expansion rate
of the Universe
4 Einstein equation for cosmology
= Friedmann equation Friedmann (1922)
2
2
8
3
G KH
a
1 0 1
gravitational constant
density
cosmic scale factor
(open), (flat), (closed) -
G
a
K
daH a
dt
a
Space expands!
宇宙の膨張率
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2 Mpc
Hubble’s Law (ハッブルの法則)
2 Mpc
70 km/s
140 km/s
140 km/s
1 Mpc = 3 Million light years (Mly)
our galaxy
Edwin Hubble (1929)
1 Mpc
galaxies more distant recede faster
expansion rate today: H0 = 70 km/s/Mpc
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30,000 km/s
size of observable universe: 10Gly (light velocity = 300,000 km/sec)
Large scale structure of the Universe
宇宙の大規模構造
seeing far = seeing past
遠くを見る=過去を見る
1Gly (300Mpc)
Hubble’s universe
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Universe was small in the past.
No galaxies, no stars 14 Gyrs ago
Matter distributed uniformly in space
extremely high temperature, high density
Big Bang !
Gamov’s fire ball cosmology (1940’s)
ガモフの「火の玉」宇宙論
Big-Bang Universe
George Gamow
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Radiation from deep space;
from high temperature era
of the Universe
Discovery of Cosmic Microwave
Background (CMB)
Wilson and Penzias
noise in radio wave from
all directions of sky
Penzias & Wilson (1965)
seeing far = seeing past !
宇宙マイクロ波背景放射
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Hot soup of photons and
elementary particles
Nucleosynthesis in the first
3 minutes: 4He, D, 7Li,...
Clear-up/neutralization
at 380,000 yrs after birth
Formation of stars &
galaxies > 1 Gyr after birth
Extremely Brief History of the Universe
big
bang
(光子と素粒子の熱いスープ)
(最初の3分間で元素合成)
(38万年後に晴上り/中性化)
(10億年後から星・銀河形成)
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we see
surface of clouds
Last Scattering Surface (最終散乱面)
If we observe sky at visible frequency band,
we see surface of cosmic clear-up
=LSS of CMB 宇宙マイクロ波背景放射の最終散乱面
(380,000 yrs old Universe)
at radio frequency (~100 GHz)
(可視光 ~ 500,000 GHz)
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Cosmological Redshift
Cosmic
Expansion
Light once very blue became
redder and redder, even redder than Infra Red,
and became micro (Radio) waves today
l ∝ size of the Universe
l
(宇宙論的赤方偏移)
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Purest
Planck distribution
in nature
“thermal spectrum”
熱平衡分布
CMB Planck distribution (プランク分布)
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accelerated expansion due to vacuum energy
Theory of Inflationary Universe
Before Big Bang ?
Katsuhiko Sato Alan Guth Andrei Linde
インフレーション宇宙理論 (1980~)
真空のエネルギーによる加速膨張
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What is “vacuum” energy?
• false vacuum (偽の真空)
huge energy is produced by expansion
total energy = (energy density) x (volume)
energy density remains the same even if
space expands
空間が膨張してもエネルギー密度は一定
absence of any matter, but ‘space’ itself
contains potential energy (vacuum energy)
物質のない「空間」が潜在的エネルギーを持つ
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observable size of the Universe 観測可能な宇宙のサイズ
baby universe
x 1030 or more
birth of mega-size
universe
Cosmic Inflation
looks perfectly
smooth & flat
explains
“homogeneity” & “flatness” 一様性と平坦性を説明
quantum vacuum fluctuations are also stretched to mega scales
and they become seeds for formation of stars and galaxies
真空の量子揺らぎも巨大サイズに引き伸ばされ星や銀河の種になる
(宇宙のインフレーション)
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Birth of Big Bang Universe
Whole vacuum energy is converted to heat 真空のエネルギーがすべて熱になる
birth of matter 物質の誕生
(quarks, electrons, neutrinos, ... & photons)
cold universe hot universe
~ 10-34 sec old universe ~ 1028 K
(ビッグバン宇宙の誕生)
strongest phase transition in the history of the Universe
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Predictions of Inflation
• Microscopic quantum vacuum fluctuations grow to
macroscopic density fluctuations to form galaxies.
(真空の量子揺らぎが密度揺らぎに成長し銀河になる)
(インフレーション宇宙論の予言)
Predictions agree perfectly with observation
• These fluctuations leave distinguishable imprints
on CMB temperature fluctuations
(この量子揺らぎはCMB揺らぎに特徴的痕跡を残す)
• Universe after inflation is extremely flat.
(インフレーション後の宇宙は極めて平坦)
18 Map of 380,000 yrs old Universe
(Last Scattering Surface) by Planck satellite
If the Universe were100 yrs old, this was 1 day old Universe
Temperature is highly uniform
510T
T
Temperature T is slightly higher in Red regions,
while it is slightly lower in Blue regions
If we magnify fluctuations by 100,000 times
(2013)
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CMB angular power spectrum
Agreement with theory tells us much about the Universe
theory
Planck 2013 data
温度揺らぎの角度パワースペクトル
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Content of the Universe today
Dark Energy (暗黒エネルギー)
~ “vacuum” energy
accelerated expansion
of the Universe
Dark Matter (暗黒物質)
large scale structure
of the Universe
Atoms (原子・通常の物質)
stars, visible objects
96% of the Universe is unknown!
現在の宇宙の構成要素
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Quantum Cosmology (量子宇宙論)
Quantum gravity is still in its infancy Superstring theory, M-theory, loop quantum gravity, ....
Need Quantum Gravity
(量子重力理論が必要)
Universe before Inflation? (インフレーション以前?)
Quantum mechanics of cosmic scale factor: a(t)
宇宙の大きさ a(t) を量子力学で取扱う
• quantum approach to the birth of the Universe
(宇宙誕生の量子論的理解) • first step toward full quantum gravity
(完全な量子重力理論への第一歩)
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At scale L ~ 10-33cm, energy fluctuations become so large
that even spacetime geometry is no longer smooth at all.
Planck Scale
Planck length: PlanckL = -3310 cm
Planck energy: Planck
2E = /c-510 g
PlanckE 810 kcal or 500 kw hour
(~ power consumed by a family / month)
J.A. Wheeler
23 World of Quantum Gravity
The whole Universe was in quantum state
when its size was ~10-33 cm
black holes and worm holes are violently created and annihilated
at scales ~ 10-33 cm (Planck scale)
Existence of the Universe is probabilistic
宇宙の存在自身が確率的
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Summary: from “nothing” to “something”
• Universe might have been born out of “nothing”.
• The baby Universe was perhaps of Planck size (10-33 cm).
• nucleosynthesis, photon decoupling, star/galaxy formation,
solar system, birth of life, ....
• inflation by vacuum energy to gigantic size. Then the
vacuum energy was converted to matter and radiation.
“無”から“有”へ
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Message of this lecture
• Big Bang Universe ・・・ confirmed
・・・ probably correct
・・・ in progress
• Inflationary Universe
• Quantum Gravity/Cosmology