ASTR 596 PC
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Preflights
Preflight 6: Large Scale Structure
Post your response on the course Compass site
Due Monday, April 19, 12noon
Reading
Course Texts
The questions are meant to direct you to the
main conceptual points; I recommend you first focus on these
rather than on the technical details, which can become involved.
- Peacock
- Chapters 15, 16
Questions
The questions are really meant to help guide your thinking
as you read. You may find it helpful to look at the questions
first and bear them in mind as you read.
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Density Fluctuations and Large-Scale Structure.
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Inflation produces density flucuations which
are nearly scale invariant,
Gaussian, and "adiabatic".
In physical terms, what is meant by each of these properties?
For each, describe a fluctuation spectrum which would
fail to have the property.
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To quantify cosmic density fields, a particularly useful
statistics the power spectrum.
What does this measure? What is its physical significance?
What power spectrum does inflation predict?
What potentially useful information is not
encoded in the power spectrum?
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Observationally, how does the amplitude of density
fluctuations depend on lengthscale?
What is a characteristic scale for fluctuations
to be "large," and how is it defined?
What is required to theoretically
describe the evolution of perturbations
on scales above and below this characterstic length?
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Gravitational Instability.
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Describe physical origin of the Jeans instability,
the Jeans length, and the Jeans mass.
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What is the main qualitative difference between the growth of
matter density fluctuations during radiation domination
versus growth during matter domination?
What is the physical origin of the difference?
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What is a transfer function?
What does it account for, physically?
Why is it a useful?
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Other questions or comments?
Brian D. Fields
Last modified: Mon Apr 12 13:20:09 CDT 2010