Modern ideas in theoretical physics revolve around the concept of extra-dimensions and the attempt to unify the four fundamental forces of nature with string theories. Our Universe has been a great & extraordinary laboratory where we formulate hypotheses to disprove these ideas. Can we find extra dimensions via the cosmic microwave background radiation left over from the first three minutes in our Universe? How do we test such an idea using modern satellite technologies like Planck and WMAP? The story started from a doctorate thesis & ends with a satellite that has been recently launched into space.

1. A Universe Less Ordinary
Searching for Extra Dimensions in the Background
Bernard Leong
Theoretical Physicist “for hire” in Hackerspace SG
@bleongcw / bleongcw (at) gmail.com
1

2. Disclaimers: I shall not answer ...
2

3. Disclaimers: I shall not answer ...
If God created the world,
who created God?
2

4. Disclaimers: I shall not answer ...
If God created the world,
who created God?
or when Stephen says
something about God....
2

5. What I am going to talk about...
Credit to Huifen & Chew Lin for this XKCD art
3

6. What I am going to talk about...
Why are we searching for
extra dimensions?
Credit to Huifen & Chew Lin for this XKCD art
3

7. What I am going to talk about...
Why are we searching for
extra dimensions?
What is the story of Our
Universe so far?
Credit to Huifen & Chew Lin for this XKCD art
3

8. What I am going to talk about...
Why are we searching for
extra dimensions?
What is the story of Our
Universe so far?
How do we find extra
dimensions in the cosmic
microwave background?
Credit to Huifen & Chew Lin for this XKCD art
3

9. 4

10. Strong
vs Electromagnetic
102
4

11. Strong
vs Electromagnetic
102
Strong
vs Weak
105
4

12. Strong
vs Electromagnetic
102
Strong
vs Weak
105
Strong
vs Gravity
1039
4

13. Strong
vs Electromagnetic
102
Strong
vs Weak
105
Strong
vs Gravity
1039
Why is gravity
so “weak”?
4

14. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
Gravity
Electromagnetism
10 3
10 16
10 18
Energy (GeV)
5

15. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
Gravity
Electromagnetism
10 3
10 16
10 18
Energy (GeV)
5

16. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
Gravity
Electromagnetism
10 3
10 16
10 18
Energy (GeV)
5

17. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
Gravity
Electromagnetism
10 3
10 16
10 18
Energy (GeV)
5

18. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
String or M-
Theory
Gravity
Electromagnetism
10 3
10 16
10 18
Energy (GeV)
5

19. Coupling Strength
?
Strong Nuclear Force
Weak Nuclear Force
String or M-
Theory
Gravity
Electromagnetism
or Loop Quantum
Gravity
10 3
10 16
10 18
Energy (GeV)
5

20. Small & Large Extra Dimensions
6

21. Small & Large Extra Dimensions
Kaluza Klein Theory (1920s)
6

22. Small & Large Extra Dimensions
Kaluza Klein Theory (1920s)
Arkani-Hamed, Dvali & Dimopolous (ADD)
Randall-Sundrum (RS)
6

23. Small & Large Extra Dimensions
Kaluza Klein Theory (1920s)
Arkani-Hamed, Dvali & Dimopolous (ADD)
Randall-Sundrum (RS)
6

24. General Relativity in a nutshell
“Matter teaches Space how to bend &
Space teaches matter how to move.”
- J. A. Wheeler
“Relativistische Zeitdiiatation eines künstlichen
Satelliten”, Friedwardt Winterberg,
Astronautica Acta (1955)
7

25. 8

26. Source: WMAP
9

27. 10

28. Temperature for
the fluctuations:
0.0005K
Source: WMAP & Planck Satellite Images
11

29. 12

30. Cosmic The first peak
Microwave measures the
Background curvature of
Power the universe:
Spectrum Our Universe
is flat
Gravitational
Waves
interacting
with CMB
13

31. 14

32. 15

33. 16

34. Extra dimensions act as a brake and slow down the
effect of gravity on polarization. If no polarization
signal is observed, one possibility is that the extra
dimension is inhibiting the gravitational wave.
17

35. 18

36. A few years
later ...
18

37. A few years
later ...
18

38. A few years
later ...
Phys.Rev. D66 (2002) 104010
18

39. “The subject is a very much difficult and intricate one than at first, one is inclined to think and I
feel that I have not succeeded in catching the keynote. When that is found, the various results
here given will no doubt appear in their real connection with one another, perhaps even as
immediate consequences of a thoroughly adequate conception of the question.”
- Tait
19