What Banged

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What Banged?
Neil Turok
DAMTP and CTC Cambridge
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Over the course of the 20th century, a very
successful account of the history of the universe
was developed, based on Einsteins theory of
gravity and the laws of nuclear and particle
physics

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G?? 8 ? G T??
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Fast forward to 2001
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The Wilkinson-MAP Satellite
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1992
2001
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Theory versus Reality (2001)
Fluctuation Level
Temperature
Polarization
Prediction Coulson, Crittenden, NT (1994)
(l 2?/??
100 10 1 .1
Angle on Sky (Degrees)
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Standard Inflationary Model
singularity
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The model includes
Inflationary Energy
Ordinary Matter (5 today)
Dark Matter (25 today)
Dark Energy (70 today) each of which has
to be delicately adjusted to fit the observations

Dark Energy
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gravitational lensing

(Tyson et al. 1995)
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The model fits a wide range of observations
BUT The initial
conditions are mysterious How did time begin?
What happened at the singularity? What was
the inflationary energy? Why did the universe
start out inflating? Why was 10-100 of the
energy in dark energy?
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Some argue this means we live in a multiverse.
The properties of our universe were selected by
our existence the anthropic principle
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All the particles and forces

• Fermions u d c s t b x 3 x 4
• e ? ?? x 4
• ?????????????????????e?????????x 2 ( rh ?s)
• Bosons ga x 8 x 2 strong
• Wa x 3 x 2 weak
• A x 2 electromag
• Ha x 4
  higgs ?
• h???x 2 graviton
• Dark Matter particles?
• Dark Energy

90
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In the late 1990s a powerful new mathematical
model emerged, called M theory
It represents a natural extension of of
Einsteins vision of spacetime
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.
Particle 0-brane
String 1-brane
Membrane 2-brane
Braneworld 3-brane
In M theory, these all occur, and there are 7
extra dimensions of space
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Six are curled up in a little ball Their size
and shape determine the pattern of elementary
particles and the constants of nature So
particle physics is now a branch of cosmology!
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• Explains
• why gravity is so weak
• why left spinning particles right
• how the density of matter and the size of the
  six dimensions can be finite at the bang

Brane
Brane
Bulk
dark matter?
ordinary matter
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The dark energy density is very small because it
relaxed to a tiny value over many cycles of
cosmic evolution The size and shape of the
extra dimensions govern the passage of the
universe through the big bang The stable cycling
of the universe may uniquely fix all the
constants of nature
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• This cyclic model can reproduce all of
  inflations successes so far
• Which picture, if either, is right?
• How can we tell?
• By more theoretical checks
• By making new observations

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Searches for Cosmic Defects
Cruz, Martinez-Gonzales, Vielva, Hobson, NT
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Possible Texture
Cruz, Martinez-Gonzales, Vielva, Hobson, NT
Science, October 2007
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Fit cold spot to a texture
mK
43ox43o patch
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Gravitational Waves
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July 08
ESA Planck satellite
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Gravitational waves from the early universe
cause a swirling polarization pattern
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Laser Interferometric Space Antenna
Launch 2015?
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Summary my view The singularity is the
key, because thats where everything came from!
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Holographic Cosmology
dual descriptions
Boundary without gravity
time
singularity
Universe with gravity
-gt Passage across the singularity is possible
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Boyle, Steihardt, NT 2005
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The Anthropic Multiverse
1. Hard to formulate precisely 2. What is being
selected for? 3. What is the multiverse?
No theory of initial conditions -gt no theory
for the probabilities Not clear if it is
falsifiable
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• Some have therefore resorted to
• the Anthropic Principle the
• universe is the way it is because
• we are here.
• They admit this is a considerable
• retreat
• A loss of precision
• A loss of targets
• Plenty of pain for meagre gains

Frank Wilczek
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Today
Vacuum energy dominates, branes stretch .
Steinhardt NT
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Matter expanded away, homogeneity and
flatness established
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ripples amplified -gt Scale-invariant
fluctuations !
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BIG CRUNCH
extra dimension collapses density,
curvature finite on branes
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BIG BANG
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New structures form and cycle begins anew
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Early Inflation -gt gravitational waves
non-gaussianity Cyclic model
-gt none Cyclic model could be refuted by ESA
Planck satellite (early 2008)
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Conclusions

• We live in a golden age of
• discovery of the universe
• A good standard model
• Key problem for the future
• What banged?

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Concordance vs Cyclic