1. String/Brane Cosmology
Can Microscopic Physics and Cosmology Inform One Another?
C.P. Burgess
Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.
Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion.
Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.
with J.Blanco-Pillado, J.Cline, C.Escoda, M.Gomez-Reino,
R.Kallosh, A.Linde and F.Quevedo (hep-th/ )

2. Outline Motivation Branes and naturalness String inflation Outlook
What can string theory and cosmology hope to teach one another?
Branes and naturalness
Rephrasing the cosmological constant problem
String inflation
Inflating the better racetrack
Outlook
08/12/2018
Decoherence

3. Outline Motivation Branes and naturalness String inflation Outlook
What can string theory and cosmology hope to teach one another?
Branes and naturalness
Rephrasing the cosmological constant problem
String inflation
Inflating the better racetrack
Outlook
08/12/2018
Decoherence

4. Outline Motivation Branes and naturalness String inflation Outlook
What can string theory and cosmology hope to teach one another?
Branes and naturalness
Rephrasing the cosmological constant problem
String inflation
Inflating the better racetrack
Outlook
08/12/2018
Decoherence

5. Outline Motivation Branes and naturalness String inflation Outlook
What can string theory and cosmology hope to teach one another?
Branes and naturalness
Rephrasing the cosmological constant problem
String inflation
Inflating the better racetrack
Outlook
08/12/2018
Decoherence

6. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

7. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
Science progresses because short distance physics decouples from long distances.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

8. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
* Inflationary fluctuations arise at very high energies: MI » 10-3 Mp
Science progresses because short distance physics decouples from long distances.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

9. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
* Inflationary fluctuations arise at very high energies: MI » 10-3 Mp
* Cosmology (inflation, quintessence, etc) relies on finely-tuned properties of scalar potentials, which are extremely sensitive to short distances.
Science progresses because short distance physics decouples from long distances.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

10. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
* Inflationary fluctuations arise at very high energies: MI » 10-3 Mp
* Cosmology (inflation, quintessence, etc) relies on finely-tuned properties of scalar potentials, which are extremely sensitive to short distances.
* Infrared modifications to gravity (MOND, Bekenstein, DGP, etc) strongly constrained by UV consistency issues.
Science progresses because short distance physics decouples from long distances.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

11. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
D branes in string theory are surfaces on which some strings must end, ensuring their low-energy modes are trapped on the brane.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

12. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
Leads to the brane-world scenario, wherein we are all brane-bound.
08/12/2018
Decoherence

13. Strings, Branes and Cosmology
Why doesn’t string theory decouple from cosmology?
Why are branes important for cosmology and particle physics?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
Identifies hidden assumptions which particle physicists and cosmologists have been making: eg: all interactions don’t see the same number of dimensions.
08/12/2018
Decoherence

14. Branes and Naturalness
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

15. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

16. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
* Shows that the string scale could be as small as TeV
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

17. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
* Shows that the string scale could be as small as TeV
* Shows that the vacuum energy is not as directly tied to the cosmological constant as was thought
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

18. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
* Shows that the string scale could be as small as TeV
* Shows that the vacuum energy is not as directly tied to the cosmological constant as was thought
* Allows room for a restricted form of nonlocality in the effective theories arising in cosmology and particle physics.
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

19. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
* Shows that the string scale could be as small as TeV
* Shows that the vacuum energy is not as directly tied to the cosmological constant
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
In 4D a vacuum energy is equivalent to a cosmological constant, and so also to a curved universe.
08/12/2018
Decoherence

20. Branes and Naturalness
* Shows that extra dimensions can be as large as microns;
* Shows that the string scale could be as small as TeV
* Shows that the vacuum energy is not as directly tied to the cosmological constant
Removal of such assumptions has allowed new insights into low-energy naturalness problems.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
In 4D a vacuum energy is equivalent to a cosmological constant, and so also to a curved universe.
In higher D solutions exist having large 4D energy but for which the 4D geometry is flat.
08/12/2018
Decoherence

21. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

22. String Inflation Why try to embed inflation into string theory?
Inflationary models must be embedded into a fundamental theory in order to explain:
Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

23. String Inflation Why try to embed inflation into string theory?
Inflationary models must be embedded into a fundamental theory in order to explain:
* Why the inflaton potential has its particular finely-tuned shape
(and if anthropically explained, what assigns the probabilities?)
Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

24. String Inflation Why try to embed inflation into string theory?
Inflationary models must be embedded into a fundamental theory in order to explain:
* Why the inflaton potential has its particular finely-tuned shape
(and if anthropically explained, what assigns the probabilities?)
* What explains any special choices for initial conditions
Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

25. String Inflation Why try to embed inflation into string theory?
Inflationary models must be embedded into a fundamental theory in order to explain:
* Why the inflaton potential has its particular finely-tuned shape
(and if anthropically explained, what assigns the probabilities?)
* What explains any special choices for initial conditions
* Why the observed particles get heated once inflation ends.
Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

26. String Inflation Why try to embed inflation into string theory?
Inflationary models must be embedded into a fundamental theory in order to explain:
* Why the inflaton potential has its particular finely-tuned shape
(and if anthropically explained, what assigns the probabilities?)
* What explains any special choices for initial conditions
* Why the observed particles get heated once inflation ends.
Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Can identify how robust inflationary predictions are to high-energy details, and so also what kinds of very high-energy physics might be detectable using CMB measurements.
Start with the picture of how scales evolve during and after inflation;
Describe the inflaton-metric system in its original and Mukhanov form;
Describe the squeezing of the Mukhanov vacuum into the Bunch-Davies vacuum
08/12/2018
Decoherence

27. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
String theory has many scalars having very flat potentials.
These scalars (called moduli) describe the shape and size of the various extra dimensions
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

28. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
String theory has many scalars having very flat potentials.
BUT their potentials are usually very difficult to calculate.
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

29. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
String theory has many scalars having very flat potentials.
BUT their potentials are usually very difficult to calculate.
A convincing case for inflation requires knowing the potential for all of the scalars.
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

30. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
String theory has many scalars having very flat potentials.
BUT their potentials are usually very difficult to calculate.
A convincing case for inflation requires knowing the potential for all of the scalars.
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

31. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
For Type IIB strings it is now known how to compute the potentials for some of the low-energy string scalars.
Giddings, Kachru & Polchinski
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

32. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Branes want to squeeze extra dimensions while the fluxes they source want the extra dimensions to grow. The competition stabilizes many of the ‘moduli’
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
08/12/2018
Decoherence

33. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
The moduli which remain after this stabilization can also acquire a potential due to nonperturbative effects. Plausibly estimated…
KKLT models
08/12/2018
Decoherence

34. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
The moduli which remain after this stabilization can also acquire a potential due to nonperturbative effects. Calculable for P4[11169]
‘The Better Racetrack’
Douglas & Denef
08/12/2018
Decoherence

35. String Inflation Why try to embed inflation into string theory?
Why is it hard?
What have we learned?
Remind the audience here that the scale of inflation is very high and so the relevant fundamental theory is not far from the Planck scale.
This potential can inflate, for some choices for the properties of P4[11169] – giving rise to realistic inflationary fluctuations!
Closest yet to inflation from an explicit string vacuum! Blanco-Pillado et.al.
08/12/2018
Decoherence

36. The Bottom Line:
Branes continue to be useful in identifying hidden assumptions in naturalness problems.
Dark Energy, Inflation,…possibly more.
We are getting very close to finding inflation in explicit string calculations
Seem not to solve fine-tunings
Provide a context for sharpening anthropism
New insights on reheating (eg cosmic strings)
Signals largely robust, except near horizon exit
08/12/2018
Decoherence

37. fin
08/12/2018
Decoherence