Chapter 9 & 10 Overheads
What is a phase transition?
What do phase transitions have to do with Cosmology?
What is a monopole?
Why was Blas looking for them?
What is a GUT?
What theory did Alan Guth come up with the explain the absence of monopoles?
What is the Inflation Theory?
The Inflation Theory proposes a period of extremely rapid (exponential)
expansion of the universe shortly after the Big Bang.
Limitations of the Big Bang Theory
While the Big Bang theory successfully explains the shape of the cosmic
microwave background spectrum and the origin of the light elements, it
leaves open a number of important questions:
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Why is the universe so uniform on the largest length scales?
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Where are the monopoles?
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Why is space so flat?
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Why is the universe expanding?
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Why is the physical scale of the universe so much larger than the fundamental
scale of gravity, the Planck length, which is one billionth of one trillionth
of the size of an atomic nucleus?
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Why are there so many photons in the universe?
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What physical process produced the initial fluctuations in the density
of matter?
The Inflation Theory
The Inflation Theory, developed by Alan Guth, Andrei Linde, and Paul Steinhardt,
offers answers to these questions and several other open questions in cosmology.
It proposes a period of extremely rapid (exponential) expansion of the
universe shortly after the Big Bang, during which time the energy density
of the universe was dominated by a cosmological constant term that later
decayed to produce the matter and radiation that fill the universe today.
The Inflation Theory links important ideas in modern physics, such as symmetry
breaking and phase transitions, to cosmology.
Predictions of the Inflation Theory
In its simplest form, the Inflation Theory makes a number of important
predictions:
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That the density of the universe is close to the critical density, and
thus the geometry of the universe is flat.
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That the fluctuations in the primordial density in the early universe had
the same amplitude on all physical scales.
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That there should be, on average, equal numbers of hot and cold spots in
the fluctuations of the cosmic microwave background temperature.
MAP will
be able to test these predictions.
Further Reading:
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Guth, A.L. & Steinhardt, P.J., "The Inflationary Universe", Scientific
American, May 1984.
David N. Spergel
Gary Hinshaw
Charles L. Bennett