Creation of Matter

1
Creation of Matter

• Early universe was very hot
• energetic photons -gt matter-antimatter pairs
• 
  protonantiproton
• 
  neutronantineutron
• But after 0.000001 seconds, the Universe was too
  cool to make pp pairs
• Most matter-antimatter pairs annihilate each
  other
• BUT, our universe is a little ASYMMETRIC so we
  end up with a small excess of matter
• no. protons 1000000.0000000001
• no. antiprotons 1000000.0000000000
• 1 extra proton left. Gave all the starsgave all
  the material in our bodies

2
Creation of Light Nuclei

• During first few minutes have
• p n -gt pn (deuterium)
• pn pn -gt Helium
• Relative number of protons and neutrons depends
  on
• - neutron being a little heavier than the proton
• - neutron decay with 890 s lifetime
• - how quickly Helium is made
• We end up with n/p 14 or 2 neutrons for
  every 14 protons
• All the neutrons in He giving about 75 H and 25
  He after first 3 minutes (and still mostly today)
• H, He, H2, He3, Li are fossil record from this
  time. Tell temperature at t1 minute

3
Exploring Very Early Times

• Fossil evidence available to astronomy are
  remnants from the first few minutes after the Big
  Bang
• To explore back to earlier times we use our
  understanding of physics
• Particle accelerators can briefly reproduce the
  Temp of early times. The highest energy machine
  is equivalent to about 1 picosecond
  (.000000000001) after the universe began
• Even earlier times can be understood by
  extrapolation but going back to the moment of
  Creation needs a complete knowledge of gravity
  and a more complete understanding of time itself

4
Why is Gravity so Weak?

• The Weak, Strong, and Electromagnetic Forces all
  have about the same strength at Fermilabs energy
  (though not at room temperature) and are well
  described by theories
• Gravity is much, much weaker. 37 orders of
  magnitude weaker than EM. Only dominates at
  larger distances as EM has both positive and
  negative charges and others are short-ranged
• No complete theory of gravity exists. Einstein
  tried for one and this is Stephen Hawkings
  primary work. Will be necessary to understand the
  very, very early universe when all 4 forces had
  the same intrinsic strength

5
Weakness of Gravity II

• Need new theories, two of which are Supersymmetry
  and Extra Dimensions
• Supersymmetry (SUSY)
• postulates the existence of extra particles,
  which are partners to existing (selectrons
  partner to electrons, etc)
• All particles produced similarly in the very
  early universe. All forces also the same at that
  time
• As Universe cools during first picosecond SUSY
  particles freeze out as they are heavier. Their
  existence helps to explain gravitys weakness
  (though not completely)
• SUSY particles could explain missing mass
  observed in astronomy

6
Weakness of Gravity III Extra Dimensions

• Lets assume (for fun) that we live in an
  11-dimensional world
• time
• normal 3-D position space
• 7 extra dimensions which are small
  (compactified is the physics term) less than 1
  mm
• Only gravity can communicate to the extra
  dimensions (all other particles and forces are
  confined to the normal 3D space)
• Fairly simple geometry explains why gravity
  appears weak - it has to spread its force fields
  over a larger space which thereby dilutes them in
  the normal 3D space itself