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Cosmological Inflation

Jason Dekdebrun Theoretical Physics Institute, UvA Advised by Kostas Skenderis. Cosmological Inflation. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A. Introduction. Gives answers to some of the earliest moments of our history.

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Cosmological Inflation

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  1. Jason Dekdebrun Theoretical Physics Institute, UvA Advised by Kostas Skenderis Cosmological Inflation TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAA

  2. Introduction • Gives answers to some of the earliest moments of our history. • Proposed by Alan Guth in 1980. • Universe undergoes an early, exponential expansion. • Solves many of the BIG problems plaguing cosmology.

  3. What Quantifies Inflation? • Friedmann-Robertson-Walker (FRW) metric for a flat universe: • Inflation when:

  4. Why Does Inflation Occur? • Occurs when the energy density of the universe is constant:

  5. Horizon Problem Observer 10 billion years 10 billion years ° ° ° ° ? 20 billion years total, BUT universe is only 14 billion years old!!! Cosmic Microwave Background

  6. Inflation Answer • H = ®, constant in time. • (aH)-1 = ®-1 e-® t, decreases with time! • During inflation, sphere of causal contact decreases with time. Objects that are in causal contact soon come out of causal contact.

  7. INFLATION! Sphere Of Causal Contact Not In Causal Contact Causal Contact!

  8. My Research: The Standard Scenario • A single scalar field, the inflaton . • Background FRW space-time. • During inflation, V() dominates the universe. • The inflaton slowly rolls down its potential, causing inflation.

  9. Slow-Roll Scenario Inflation! Important Point!: Cosmic Microwave Background is NOT from Big Bang! Reheating! α β δ € ζ Ω Σ π

  10. Perturbations • In the case of the inflaton, perturbations are considered quantum fluctuations:

  11. Perturbations added to the FRW metric: • This leads to perturbed general relativity quantities (Einstein tensor, Christoffels, Ricci tensor, etc.)

  12. Example:

  13. Equations To Solve • We would like to solve Einstein’s equations, • where the energy-momentum tensor, • is derived from the Lagrangian:

  14. Example: Second Order (i,j) Einstein Equation

  15. Also the Klein-Gordon equation: • This is derived from an action using the same Lagrangian.

  16. Example: Second Order Klein-Gordon Equation

  17. Gauge Invariant Variables • Under a spatial translation by di, the following perturbations transform as: • Combining these in just the right way leads to a variable with no transformation:

  18. First order Einstein equations: • 3 more gauge invariant variables:

  19. Second Order Curvature Perturbation: • This gauge invariant variable will be the link between theory and observation.

  20. fNL & Observations • What is fNL? • fNL is the amplitude of the three-point correlation function. • Correlation of curvature perturbations, ³(2). • Also known as the bispectrum. • Any detection of the bispectrum indicates non-Gaussianity.

  21. Planck Satellite • Launched May 14th, 2009. • Finish collecting data in 2012. • Will provide very important measurements of non-Gaussianity.

  22. Conclusion • Measurements of non-Gaussianity will help distinguish amongst the many different models of inflation. • This will give us a closer look and deeper understanding of the very beginning of our universe!

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