DOES EXOTIC MATTER EXIST

1
DOES EXOTIC MATTER EXIST?

• Vacuum behaves in exotic fashion near an event
  horizon
• basis for Hawking evaporation
• does not work if horizon is not present
  no good for holding wormholes open
• Believed that vacuum (and all forces of nature)
  behave differently at high energies (i.e., high
  temperatures)
• e.g., conditions just after Big Bang
• fundamental idea in grand unified theories
• Observations suggest that the matter/energy of
  the Universe was exotic just after Big Bang

2
BIG BANG THEORY

• Universe started out tiny and hot
• Explains universal glow of sky cosmic
  microwave background
• Explains 25 helium formed in first 3 minutes
• Predicts
• expansion slows down continuously due to gravity
  of all matter energy
• may recollapse, expand forever, or coast
  depending on how much matter/energy is in
  Universe
• Does not explain
• relative amts. of radiation/matter in Universe
  (107 photons/baryon)
• total density of matter/energy (flatness)
• observed uniformity of Universe

3
INFLATION of the EARLY UNIVERSE

• Basic idea Expansion of Universe tremendously
  accelerated shortly after Big Bang
• occurred at 10-36 sec (Planck time was 10-44
  sec)
• Universe inflated by factor 1030
• requires matter to have repulsive gravity
  exotic matter
• Proposed by Alan Guth (1980) to explain
• flatness problem
• Problem expansion of universe just right
• Solution curvature stretched out by inflation
• horizon problem
• Problem Universe uniform in all directions and
  locations, but different regions could not have
  communicated
• Solution regions were in contact before
  inflation started

4
INFLATION PROPOSES THAT UNIVERSE FORMED OUT OF
NOTHING

• Then Positive energy of all matter/energy
  negative energy of
  vacuum 0
• Now Positive energy of expanding matter
  negative gravitational energy 0
• Universe has zero total energy flat
  Universe will never recollapse, will
  coast indefinitely
• Everything in Universe appeared spontaneously
  from vacuum fluctuations
• phase transition, like fog condensing from
  supercooled vapor
• Could it happen again?

5
AN ACCELERATING UNIVERSE?

• Negative vacuum energy would accelerate the
  expansion of the Universe
• ordinary matter/energy would decelerate it
• this is what Einstein called the cosmological
  constant
• introduced to explain how Universe could remain
  stationary
• later called it his biggest blunder
• Direct evidence that Universe was expanding more
  slowly in the past
• acceleration more gentle than during era of
  inflation
• increases estimated age of Universe resolves
  discrepancy with measured ages of stars

6
CHILD UNIVERSE?

• Imagine creating wormhole
  inside black hole
• Would lead to a different
  Universe
• Suppose that new Universe
  inflates
• We could be inside such a Child Universe!
• multiverse an infinite assembly of child
  universes
• New Universe may have different properties from
  old one!
• Different constants of nature?
• Different structure of forces?
• Different number of dimensions?

7
SO IF THERE COULD BE AN INFINITE ARRAY OF
UNIVERSES WITH DIFFERENT PROPERTIES, WHY IS OURS
JUST SO?

• Not made entirely of H ( no complex
  chemistry) or Fe ( no nuclear power in
  stars)
• Dense enough for stars to condense but not so
  dense that everythings a black hole
• Exists long enough for stars to produce heavy
  elements and life to evolve
• Fine-tuned so that life has time to evolve before
  all stars burn out

COINCIDENCE? I DONT THINK SO...
8
ANTHROPIC PRINCIPLES (Carter 1970)

• Weak anthropic principle
• The fact that we can exist to observe the
  Universe implies that conditions must be somewhat
  special at our location
• physical laws must be consistent with development
  of life
• Were on a hospitable planet near a star, not
  floating in space or close to a quasar
• Strong anthropic principle
• Universe must be so as to allow observers to
  exist
• More palatable (?) of the Universes that make up
  the multiverse, only those with special
  conditions can have observers

9
ANTHROPIC PRINCIPLES (contd.)

• Smolin (1997) Natural selection for Universes?
• Assumes that Universes able to form lots of black
  holes are similar to those most hospitable to
  life
• related to conditions for stellar evolution
• shaky assumption
• Assumes black holes are necessary in order to
  create Child Universes
• Thus Universes that can form many black holes
  have more progeny
• Assumes Child Universes differ from parents by
  small mutations
• no mechanism identified WHATSOEVER interesting
  but wild speculation
• If all this were true, Universes could evolve
  toward conditions that favor life!