Input for fundamental physics Model independent way to extract information Known tests (very)...
19
Input for fundamental physics Model independent way to extract information Known tests (very) sensitive to theoretical priors challenges to experiment & ןןןןןן- ןןןןןןןןןן ןןRam Brustein Determining the nature of DARK ENERGY Irit Maor Paul Steinhardt
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Transcript of Input for fundamental physics Model independent way to extract information Known tests (very)...
Input for fundamental physics Model independent way to extract information Known tests (very) sensitive to theoretical
priors challenges to experiment & theory
אוניברסיטת בן-גוריון
Ram Brustein
Determining the nature ofDARK ENERGY
Irit MaorPaul Steinhardt
0)(3
)(4
83 2
pH
pGH
GH
N
N
Focus on: Equation Of State
standard GR form
Space curvature w = -1/3Higher tensor invariants Scalar fieldsExtra dimensionsScale dependent GN
Modified Friedman eq.• and more, …“never underestimate the creativity of a theorist!”
22 3
2
3
1
3
21
a
aa
H
Hpw
T
TT
FP model EOS additional possibilities: Tegmark
state finder: Sahni et al. 0|0| , tt aa
Classic tests measure integrals of EOSbackground
• luminosity distance
• volume
• angular distance
• shearfluctuations• ISW• linear/non-linear growth factors• speed of sound
z
xH
dxr
1
1 )(
rzdL )1(
)1/( zrdA
)()()( zrzHz
zAP
Hrdz
dV/2
situation unclear: Please help!
situation clear
For example:Luminosity distance dL vs. redshift z
20
2
0)(
ln)1(3ln
0)1(3
H
H
zdwd
wH
T
T
TT
TTT
Textbook form is not sufficient
g= m /(1- m)
z
Q
Q
Qm
Qm
Q
T
TT
xdxwg
wpppw
1
1
ln)(3exp11/
/
Splitting components off, for example, NR matter (dark and visible)
Degeneracy!
a) DLb) DL/DLc) wQ (z)For 9 different EOS
Assuming 1. perfect knowledge of M
2. flat U.
Maor et al. (2001)
P. Antilogus
J. Frieman et al
Weller & Albrecht
Similar conclusions P. Astier, Kujat et al, E. Linder, ...
I. Maor et al
NOT
MEASURE
w'
V
Vpw
2
21
221
Fast roll – w ~ +1Slow roll – w ~ -1Oscillations – w~ 0
w < -1, w > +1 possible, easy !!!
KVVK
VK9
1110
High sensitivity to choice of theoretical framework and priors
» need to keep an open mind about priors: for example restricting wQ>-1
» present experimental results in a way that will allow modifying priors
? use some input from theory to parametrize evolution
Practical implications:
Breaking the Degeneracy ?
I. Combine different types of high precision (~ percent) measurements
about 20% in current value of wQ & not very helpful for time-dependence, but …
• sensitivity estimates depend on actual value of EOS: away from -1 / large positive w' are best
• Hard to distinguish between different forms of DE.
* partial analysis
*
• DE expected to “disappear” for z > 2• CMB photons travel most of the way through MD U.
No gain compared to “low z” probes
• Best accuracy for dA from CMB ~ 1% (e.g. 1st peak)
CMB comparable to future SNIa experiments
(M known+ flat U.+…)
For example: CMB + SNIaMaor et al (2002)Maor & Brustein (2003)Frieman et al, Caldwell & Doran, ...
╬ Confusion about possible attainable sensitivity of other experiments (shear, volume, growth factor, …)
Breaking the Degeneracy ?
II. Invent new “local” tests:
“move the detector to a different z”
III. Accept theoretical input:
e.g.: that dark energy is a CC,
a specific quintessence model, …
Measure z(t)
)()(1 0
ta
atz
Hztz )1()(
HzHztz )1()(
223 )1( HwH T
1)1()1(
)( 23
2
Twz
ztz
35
232 )(
)1( z
tzzwT
Practical ??
Jimenez & Loeb, Jimenez et al
ConclusionsKnown tests (very) sensitive to theoretical priors
Challenges to Experiment & Theory
• Need: public access to data independent combined analysis explore different priors
• Need:– either a new “local” test - ???– or new theoretical input - ??? – or LUCK
• CMB vs. SN Ia
x=z+1
Maor & Brustein (2003)
Maor et al astro-ph/0112...
Linder, astro-ph/0212...
