1. Dark Energy Equation-of-State parameter for high redshifts
Article by Ariadna Montiel and Nora Bretón
Presented by Pedro Mendes (s )

2. Table of contents
Brief introduction to Dark Energy in the context of the Einstein equations and FTW Geometry
Brief introduction to Gamma Ray Burst
Calibrating GRB data
Results
Conclusion

3. Dark Energy Proposed as a consequence of the Einstein’s equations
First direct evidence in 1998, from observations of Type 1a supernovas observations

4. Diving into the Math: FTW Geometry
Separating the densities:
- density of matter and dark matter
- density of dark energy

5. Diving into the Math: FTW Geometry
Equation of state for Dark Energy: From energy-momentum conservation: - density at the present time

6. Diving into the Math: FTW Geometry
Using the density equation on the 1st Friedmann equation: Where: is the fractional density parameter.

7. Diving into the Math: FTW Geometry
Final expression for ω: Aim of the paper: get ω from H.

8. Luminosity distance
Relation with Hubble parameter:

9. Gamma Ray Bursts
Discovered in the 60’s by the U.S. Vela spy satellites
Origins: supernovas and hypernovas, or merging of 2 neutron stars in a binary system
All observed GRB originate outside the Milky Way.

10. Calibrating GRB
By Kodama et al., using a sample of 69 GRB’s: However, this give a point of divergence in the redshift.

11. Calibrating GRB

12. Calibrating GRB
Best relation for the tendency (26 of the 69 sets): This gives:

13. Fitting the data

14. Fitting the data

15. Analyzing Fit
Asymptotic behavior around a value slightly bigger that ω=-1
Completely diverges around z=1.54

16. Why z = 1.54?
When:
So, this is only valid for z<1.54

17. Conclusions Higher redshift supernovas are needed to study Dark Energy
GRB are a powerful tool to study supernovas
We can obtain a relation between the GRB parameters, supernovas redshift and Dark Energy EoS
However, current models can’t describe z>1.54