Probing the curvature and dark energy

Gong, Yungui

龚云贵

Chongqing University of Posts and Telecommunications

重庆邮电学院

“宇宙暗物质和暗能量”研讨会， 2005 年 7 月 8日

• Dark Energy Introduction

• Current Status of Parameterizations

• One-parameter Parameterization

• Conclusion

Why Dark Energy? 03.175

98.0

46.0

2

26.031.0

15.017.00

m

Model independent method

• Taylor expansion of Hubble parameter, M. Visser, CQG 21 (2004) 2603

• Prameterizations of energy density: 2nd Order Polynomial, U. Alam etal. MNRAS 354 (2004) 275

• Negative Power Polynomial, U. Alam etal. MNRAS 354 (2004) 275

1))1()1((3

)1(2)1(,)1()1(

2210

2212

210

zAzAA

zAzAzAzAA QQ

1))1()1()1((3

)1()1(,)1()1/(

31

201

13

1110

zBzBzB

zBzBzBzBB QQ

Common Parameterization of WQ

• Constant equation of state w

• Linear equation of state w=w0+w1z

• Stable Parameterizations

• Wetterich Parameterization

• Parameterization

20)))1ln(1/(1(3

0 ))1ln(1(,)1( 0

zbz Q

zbQQ

z

zez a

Qzz

QQaa

1,)1( 0)1/(3)1(3

00

)1ln(1,))1ln(1()1( 0/33

00

zbzbz Q

bQQ

20)1(2/3)1(3

0 )1(,)1(

220

z

zez a

Qzz

QQa

H.K. Jassal, MNRAS 356(2005) L11

Fitting Results

• Taylor expansion of Hubble parameter

Y. Gong, astro-ph/0405446 , Class. Quantum Grav. 22 (2005) 2121

1))1()1((3

)1(2)1(,)1()1(

2210

2212

210

zAzAA

zAzAzAzAA QQ

1))1()1()1((3

)1()1(,)1()1/(

31

201

13

1110

zBzBzB

zBzBzBzBB QQ

z

zez a

Qzz

QQaa

1,)1( 0)1/(3)1(3

00

20)1(2/3)1(3

0 )1(,)1(

220

z

zez a

Qzz

QQa

20)))1ln(1/(1(3

0 ))1ln(1(,)1( 0

zbz Q

zbQQ

)1ln(1,))1ln(1()1( 0/33

00

zbzbz Q

bQQ

Supernova Fit to dark energy

One parameter Parameterization

z

wzw

1

)( 0

zzez

wzw

1/0

1)(

Y. Gong and Y.Z. Zhang, astro-ph/0502262

4.175

2.01.1

05.001.0

05.025.0

2

0

0

0

wk

m

z

wzw

1

)( 0

5.176

97.0

001.0

04.028.0

2

17.019.00

046.0045.00

0

w

k

m

zzez

wzw

1/0

1)(

Results

Summary

Thanks!