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A Phenomenological Dark Energy Model and its Inconsistency

Chien -I Chiang 江建誼. A Phenomenological Dark Energy Model and its Inconsistency. Outline. Horava Gravity Theory Cosmological Solution A Phenomenological Dark Energy Model Inconsistency of the model. Horava Gravity Theory. Anisotropic Scaling with dynamical critical exponent

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A Phenomenological Dark Energy Model and its Inconsistency

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  1. Chien-I Chiang 江建誼 A Phenomenological Dark Energy Model and its Inconsistency

  2. Outline • Horava Gravity Theory • Cosmological Solution • A Phenomenological Dark Energy Model • Inconsistency of the model

  3. Horava Gravity Theory • Anisotropic Scaling with dynamical critical exponent • The Action of the Theory should satisfy this scaling symmetry. Take , for example, the following action satisfy this symmetry

  4. Horava Gravity Theory • Lorentz Symmetry • Foliation Structure: • Coordinate transformations adapted to the foliation : • ADM decomposition:

  5. Horava Gravity Theory • Foliation-preserving Diffeomorphisms: • Kinetic term of the space-time action:where

  6. Horava Gravity Theory • The whole action with detailed-balanced with soft violation :

  7. The Friedman Equations • Consider homogeneous and isotropic cosmological solution with FRW form • Assume the matter contribution to be the form of a perfect fluid with the energy density and pressure .

  8. The Friedman Equations • Park obtained • The upper (lower) sign denotes the case. Mu-In Park A Test of Horava Gravity: The Dark Energy arXiv:0906.4275 [hep-th]

  9. The Friedman Equations • The term, exists only for and become dominant for small scale factor, implying that the cosmological solutions of GR are recovered at large scale. • There’s no contribution from the soft IR modification to the second Friedman equation.

  10. Phenomenological Dark Energy Model Proposed by Park • Comparing the GR and the Horava:

  11. Phenomenological Dark Energy Model Proposed by Park • Identifying fundamental constants with parameters in Horava theory: • Identify dark energy sector as the extra terms due to Horava space-time action:

  12. Phenomenological Dark Energy Model Proposed by Park • Equation of state parameter: • Determing the Parameters:

  13. Inconsistency • The Data used by Park: • By some rearrangement we have K. Ichikawa and T. Takahashi, “The Hubble Constant and Dark Energy from Cosmological Distance Measures,” JCAP 0804, 027 (2008) [arXiv:0710.3995 [astro-ph]].

  14. Inconsistency • We choose the following set: • By this we obtain • Hence we have

  15. Comments • By using the data set used by Park, we can see that the dark energy density ratio in this model is too small comparing to 0.7. Even if the equation of state parameter have good behavior, the energy density ratio problem would still be a big problem.

  16. Comments • In this model, the equation of state parameter will differ to cosmological constant model only when . However, it does not depends on , which is a very strange feature.

  17. Thanks For Your Attention

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