![Page 1: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/1.jpg)
1
Andreas Albrecht
UC Davis
COSMO 02
Chicago, September 2002
TitleModels of Cosmic Acceleration:Challenges and Exciting
Directions
![Page 2: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/2.jpg)
2
Faculty PositionHigh Energy Theoretical Physicist
Department of PhysicsUniversity of California, Davis
The Department of Physics at the University of California at Davis invites applications for a faculty position in theoretical high energy physics. Appointment at any level is possible depending upon qualifications and experience. The successful candidate will be the first of three planned new appointments directed toward pursuit of exciting new ideas and challenges associated with the interface between formal theory and phenomenology.
This position is open until filled; but to assure full consideration, applications should be received no later than
January 2, 2003. This targeted starting date for appointment is July 1, 2003.
Advertisement
![Page 3: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/3.jpg)
3
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 4: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/4.jpg)
4
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 5: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/5.jpg)
5I.1 The cosmological constant problem / links to fundamental gravity.
As far as we can tell so far, the cosmic acceleration might be the result of
4120 4 310 10PM eV
![Page 6: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/6.jpg)
6I.1 The cosmological constant problem / links to fundamental gravity.
= 10120
0 ?
Vacuum Fluctuations
Greatest unsolved problem in physics:
Why is 12010 QFT
![Page 7: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/7.jpg)
7I.1 The cosmological constant problem / links to fundamental gravity.
Challenges:
• 0 dream may not work
• A more mature fundamental theory of gravity could overturn ideas about the origins of acceleration
• Huge potential for observations to impact fundamental theories
![Page 8: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/8.jpg)
8
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 9: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/9.jpg)
9
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 10: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/10.jpg)
10I.2The “why this/why now” problems
Why this?
Where does this strange parameter come from?
4120 4 310 10PM eV
![Page 11: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/11.jpg)
11I.2The “why this/why now” problems
Why now?
If the source of acceleration is some dynamical matter (“quintessence”), then it has to acquire the value
4120 4 310 10eff PM eV
today (t=14.5 Gyr). (not some other time)
R MQ
TodayTime
![Page 12: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/12.jpg)
12
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 13: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/13.jpg)
13
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 14: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/14.jpg)
14I.3 Quantum corrections/long range forces
If the acceleration is produce by a scalar field (quintessence):
i) The quintessence field must have a mass
How can this value stay safe from quantum corrections?
3210Qm eV
![Page 15: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/15.jpg)
15I.3 Quantum corrections/long range forces
If the acceleration is produce by a scalar field (quintessence):
ii) If such a small mass is preserved, there is a new long range force mediated by the quintessence field.
How can 5th force bounds be evaded?
(Carroll)
![Page 16: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/16.jpg)
16
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 17: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/17.jpg)
17
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 18: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/18.jpg)
18II.1 The quantum physics of
i) The entropy bound:
If there really is a , the late-time asymptotic state of the universe will have a horizon with area:
This implies a Hawking-Beckenstein type upper bound on the entropy:
Are we then compelled to only consider only models of physics with a finite dimensional Hilbert space? (Excludes field theory, M-theory, SHO, etc.)
A
"ln "4 MAX
AS S N
G
T. Banks & W. Fischler
![Page 19: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/19.jpg)
19II.1 The quantum physics of
ii) Other constraints on fundamental theories with :
Do scattering states exist? etc
![Page 20: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/20.jpg)
20II.1 The quantum physics of
iii) Causal set theory of gravity:
a prediction of causal set theory?!
2 2TOT
(Ahmed et al. Sep 2002)
![Page 21: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/21.jpg)
21
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 22: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/22.jpg)
22
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 23: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/23.jpg)
23II.2 Dark energy/quintessence, Stage I (adventures)
Inflation has taught us how to accelerate the universe with a scalar field… why not try again?
1)/cos(4 fMV
With f 1018GeV, M 10-3eV
PNGB: Frieman, Hill, Stebbins, & Waga 1995
4MV
]1[ /4 PMeMV
M=1 meV - 1GeV
Zlatev, Wang & Steinhardt 1998
Scalar field domination/ acceleration
![Page 24: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/24.jpg)
24II.2 Dark energy/quintessence, Stage I (adventures)
Inflation has taught us how to accelerate the universe with a scalar field… why not try again?
1)/cos(4 fMV
With f 1018GeV, M 10-3eV
PNGB: Frieman, Hill, Stebbins, & Waga 1995
4MV
]1[ /4 PMeMV
M=1 meV - 1GeV
Zlatev, Wang & Steinhardt 1998
Scalar field domination/ acceleration
N.B Resurrect the 0 dream
![Page 25: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/25.jpg)
25II.2 Dark energy/quintessence, Stage I (adventures)
Some more scalar field models of dark energy:
Dodelson Kaplinghat & Stewart 2000
RQ
Time
M
Albrecht & Skordis 1999
OscillatingShadowing
There are many other examples
![Page 26: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/26.jpg)
26II.2 Dark energy/quintessence, Stage I (adventures)
A note about the “why this/now” problem:
• Essentially all existing quintessence models “solve” it by relating to parameters in the quintessence equations
• Attractor behavior gets rid of initial conditions dependence
• How compelling this “solution” is depends on how convinced you are that nature has chosen those parameters.
( )t
![Page 27: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/27.jpg)
27II.2 Dark energy/quintessence, Stage I (adventures)
A note about Quantum corrections/long range forces:
• Almost all models of dynamical dark energy/quintessence completely ignore these issues. “adventures”
![Page 28: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/28.jpg)
28
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 29: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/29.jpg)
29
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 30: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/30.jpg)
30II.3 Dark energy/quintessence, Stage II (getting serious)
Stage II: Take quantum corrections/long range forces seriously
*PNGB: Frieman, Hill, Stebbins, & Waga 1995
* Extra dimensions
A.A, Burgess, Ravndal 2001
* Supergravity Kalosh et al. 2002 (?)
• Challenging particle physics issues
![Page 31: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/31.jpg)
31II.3 Dark energy/quintessence, Stage II (getting serious)
Stage II: Take quantum corrections/long range forces seriously
*PNGB: Frieman, Hill, Stebbins, & Waga 1995
*Kalosh et al. 2002 (?)
*A.A, Burgess, Ravndal 2001
• Challenging particle physics issues
Also: Risky because more radical developments could invalidate these efforts
![Page 32: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/32.jpg)
32
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 33: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/33.jpg)
33
I) Challenges for models of cosmic acceleration
I.1 The cosmological constant problem / links to fundamental gravity.
I.2The “why this/why now” problems
I.3 Quantum corrections/long range forces
III) Conclusions
II) Exciting Directions
II.1 The quantum physics of
II.2 Dark energy/quintessence, Stage I (adventures)
II.3 Dark energy/quintessence, Stage II (getting serious)
Models of Cosmic Acceleration: Challenges and Exciting Directions, COSMO-02
![Page 34: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/34.jpg)
34
III) Conclusions
Modeling cosmic acceleration leads to:
Exciting challenges and new directions, many of which are connected with very fundamental questions.
Real opportunity for dramatic observational advances
Weller & AA
![Page 35: Andreas Albrecht UC Davis COSMO 02 Chicago, September 2002](https://reader035.vdocuments.net/reader035/viewer/2022062322/5681464e550346895db360ba/html5/thumbnails/35.jpg)
35
z
D L
% deviation
( )w z
Parameters and Cosmic Confusion IV-35
NB: Don’t be afraid of degeneracies!! Data can still distinguish among many interesting models
Maor et al.