Probing for dynamics of dark energy

with latest cosmological dataHong Li

Department of AstronomyPeking University

In collaboration withJunqing Xia, Gongbo Zhao, Zuihui Fan a

nd Xinmin Zhang

outline

• Brief review on DE • Global anlysis on the determination of

EOS of DE with WMAP3+LSS+SNe• Constraints on EOS including GRBs • Summary

Dark Energy: Negative pressure:)3(

3

4/ p

Gaa

0a 3/1/ 03 pwp

* Smoothly distributed, (almost ) not clusteringCandidates:I Cosmological constant (or vacuum Energy)

g

GT

8

1/ pw eV10~m

)102(8

3-

43

eVG

p

12010~/ obth cosmological constant problem!II Dynamical Field: Quintessence, K-essence, Phantom, Quintom etc

)(2

1QVQQL

VQpVQ QQ 22

2

1,

2

1

11 Qw

The equation of state (EOS) w: a parameter characterizing DE

The model independent data analysis need the parameterization of w:

zwww 10

)1/(

)1(

10

10

zzww

awww

●

●

* Vacuum : w=-1

* Quintessence:

* Phantom:

* K-essence: or but cannot across -1 * Quintom: crossing w=-1 ……………..

Global fitting procedure

• Parameterization of EOS:

• Perturbation included

G.-B. Zhao, et al., PRD 72 123515 (2005)

• Method : modified CosmoMC

• Data : WMAP+LSS+SN

• Cosmological parameters:

)1()( 10 awwaw

assuming flat universe,

For non-flat, see later

))sin(ln()( 210 awwwaw

Constrains on dark energy with SN Ia (Riess) + SDSS + WMAP-1

Observing dark energy dynamics with supernova, microwave background and galaxy clustering Jun-Qing Xia, Gong-Bo Zhao, Bo Feng, Hong Li and Xinmin Zhang Phys.Rev.D73, 063521, 2006

The importance of DE perturbation!

2007.6.5 IHEP 博士论文答辩

Constraints on EOS with WMAP3Relative error: ~9%

Relative error > 50% !!

* Emphasizing the importance of the perturbation of DE* A constant EOS considered by the WMAP group

Global fitting with SN Ia, SDSS and WMAP3

• The standard ΛCDM model is still a good fit to the current data

• Quintom is mildly favored

410.0176.0305.0178.00 146.1

w

410.0176.0305.0178.00 146.1

w

802.0622.0996.1652.01 6.0

w

Probing dynamics of DE with supernova, galaxy clustering and the three-year Wilkinson Microwave Anisotropy Probe (WMAP) observations G.-B. Zhao, J.-Q. Xia, B. Feng and X. Zhang, astro-ph/0603621

)1/(*1 zzwww 0

Global fitting with

• Parameterization of EOS: • Perturbation included• Method : MCMC• Data : WMAP+SDSS+SN• Cosmological

parameters:

K

)1()( 10 awwaw

The flat Universe is a good approximation, for within 2σC.L. 06.0K

Global analysis of the cosmological parameters including GRBs

• Results from the global analysis with WMAP3+LSS

+SNe(Riess 182 samples)+GRBs (Schaefer 69 sa

mple)

• New method for solution of the circulation problem

the 69 modulus published by Schaefer (in astro-ph/0612285)

Bias with only GRB

Need global analysis

Hong Li, M. su, Z.H. Fan, Z.G. Dai and X.Zhang, astro-ph/0612060, to appear in Phys. Lett. B

WMAP3+LSS+SN

WMAP3+LSS+SN+GRB

)1/(* zzwww a0

The relevant papers on study with GRBs:E.L.Wright astro-ph/0701584

F.Y. Wang, Z. G. Dai and Z. H. Zhu, astro-ph/0706.0938

They use the shift paramater R, BAO from LSS, and so on…..

Problems:

• The circulation problem : Due to the lack of the low-redshift GRBs, the experiential correlation is obtained from the high-redshift GRBs with input cosmology !

• Using shift parameter : the loss of the full information of CMB data in the global fitting

CMBz

k

k

m

zE

dzR

0 )'(

'sinn

020.067.1 ),,,,(:)6

023.070.1 ),,,,,,(:)5

038.077.1 ),,,,,,(:)4

032.066.1 ),,,,,,(:)3

030.074.1 ),,,,,,(:)2

022.070.1 ),,,,,(:)1

022

022

022

022

022

022

RAHhh

RAnHhh

RmAnHhh

RrAnHhh

RAnHhh

RAnHhh

scb

ksscb

sscb

sscb

ssscb

sscb

S_r is the fluence of the r-ray; t_j is the Break time; n is the circumburst particle Density; eta_r is the fraction of the kineticEnergy that translate to the r-rays;E_peak is the peak energy of the spectrum

What is the circulation problem?

• Due to the lack of the low-redshift GRBs, the experiential correlations are obtained from the high-redshift GRBs with input cosmology which we intend to constrain, it lead to the circulation problem!

From the observation, we can get: S_r, t_j, n, eta_r, E_peak

With a fire ball GRB model:

Ghirlanda et al.

UsuallyInput a cosmology

Get A & C

A new method for overcoming the circulation problem for GRBs in global analysis

ApeakcEE

We integrate them out in order to get the constraint on the cosmological parameter:

We let A and C free:

We can avoid the circulation problem ! And method can apply to the other correlations.

EEpeak Correlation as an example:We takeHong Li et al., to appear

For flat universe !

With free ! K

For flat universe !

The constraints on A and C related with the correlation:

i. e., in the literature C is set to [0.89, 1.05]; A is set to 1.5One can find that, this will lead to the bias to the final constraints on The cosmological parameters!

SUMMARY Our results on determining EOS of DE with MCM

C from WMAP+SDSS+SN(+GRBS) ; Cosmological constant fits the current data well

at 2 sigma; Quintom is mildly favored ; The Future observation like SNAP and Planck will improve the constant

J.-Q. Xia, H. Li, G.-B. Zhao and X. Zhang, astro-ph/0708.1111