1. 1 On Generalized Chaplygin Gas Yungui Gong 龚云贵 重庆邮电学院 超弦 / 理论、粒子物理及宇宙学专题研讨会 10 月 21 日 -11 月 3 日 10/23/2004

2. 2 Motivation

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4. 4 Chaplygin gas As a perfect fluid with the equation of state Motivation: Nambu-Goto action for a d-brane moving in a (d+2)-dimensional spacetime in the light-cone parameterization Quintessence filed potential

5. 5 Cosmological Solution

6. 6 Generalized Chaplygin Gas Quintessence filed potential As a perfect fluid with the equation of state Flat universe, Chaplygin gas is the only source

7. 7 Cosmological Solution: Possible Unification of dark matter and dark energy

8. 8 Chaplygin gas as dark energy

9. 9 Constraints 1.The total energy density is non-negative 2.The current density is not increasing 3.Sound speed (1) (2) (3)

10. 10 Constraints on GCG (1) (2) Used (1) (3) Used (1)

11. 11 Physical Constraints From (2), we get

12. 12 SN Fitting Method

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19. 19 Age fitting

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21. 21 Current Measurements on matter density Peebles, PJE, astro-ph/0410284