Is the cosmic acceleration slowing down? Tuo Zhongliang KITPC, CAS April 1st, 2011.
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Transcript of Is the cosmic acceleration slowing down? Tuo Zhongliang KITPC, CAS April 1st, 2011.
Is the cosmic acceleration Is the cosmic acceleration slowing down?slowing down?
Tuo ZhongliangTuo Zhongliang
KITPC, CASKITPC, CASApril 1st, 2011April 1st, 2011
OutlineOutline
Eternal acceleration or escape eternal acceleratiEternal acceleration or escape eternal acceleration?on?
Cosmographic approachCosmographic approach
Non-parametrization method Non-parametrization method
SummarySummary
Riess
Perlmutter
The accelerating expansionThe accelerating expansion
SNIa observations in 1998 find cosmic acceleration.
Concordance model (LCDM)
WMAP7
Dark energy: 73.4%
Dark matter: 22.2%
Normal matter: 4.4%
the big rip
“Cosmic Doomsday”
R.R.Caldwell, M.Kamionkowski and N.N.Weinberg, Phys.Rev.Lett.91(2003)071301
Can the universe escape eternal acceleration?J. D. Barrow, R. Bean and J. Magueijo, Mon.Not.Roy.Astron.Soc.316:L41,2000
A difference of 120 orders of magnitude
Cosmographic approach
Redshift expansion
y-redshift expansion,
Thus to reduce the systematic error
Hubble parameterHubble parameterFor z<zcut or y<ycut,
For zcut<z<1.0 or ycut<y<1.0,
Data setsSNeIa: Union2 (R.Amanullah et al. e-Print: arXiv:1004.1711 )
Distance modulus
Marginalization over μ0
Data setsHubble parameter (D. Stern et al. e-Print: arXiv:0907.3149 )
Marginalization over H0
1-D marginalized probability distribution of q1-D marginalized probability distribution of q00
dL zdL y
0 .8 0 .6 0 .4 0 .2 0 .0 0 .20 .0
0 .2
0 .4
0 .6
0 .8
1 .0
q 0
Pq 0
dLH zdLH y
1 .0 0 .8 0 .6 0 .4 0 .2 0 .00 .0
0 .2
0 .4
0 .6
0 .8
1 .0
q 0
Pq 0
Evolution behavior of q(z)Evolution behavior of q(z)
Evolution behaviors of q(z)Evolution behaviors of q(z)
dLH z
C D M
0.2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 3
2
1
0
1
2
3
z
q
dLH y
C D M
0.2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 3
2
1
0
1
2
3
z
q
dL z C D M
0.2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 3
2
1
0
1
2
3
z
q
dL y C D M
0.2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 3
2
1
0
1
2
3
z
q
Comparison with the Hubble dataComparison with the Hubble data
CD M
dL zdL ydL
H zdLH y
0 .0 0 .2 0 .4 0 .6 0 .8 1 .0
1 .0
1 .5
2 .0
2 .5
z
HzH 0
Non-parametrization methodNon-parametrization method
Independent of the calibration
Reconstructed deceleration parametersReconstructed deceleration parameters
CD M
dL zdL ydL
H zdL
H y
0 .0 0 .2 0 .4 0 .6 0 .8 1 .0
4
2
0
2
4
6
z
qz
SummarySummary
The universe transited from deceleration from acThe universe transited from deceleration from acceleration at higher redshift than what the LCDM celeration at higher redshift than what the LCDM model predictsmodel predicts
The universe is still in the stage of accelerating eThe universe is still in the stage of accelerating expansionxpansion
SNIa data favor a transient acceleration, even wiSNIa data favor a transient acceleration, even with the Hubble parameter data added in.th the Hubble parameter data added in.
Thanks!Thanks!