Dark Energy Equation-of-State parameter for high redshifts Article by Ariadna Montiel and Nora Bretón Presented by Pedro Mendes (s3220524)

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

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

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

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

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

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

Luminosity distance Relation with Hubble parameter:

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.

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

Calibrating GRB

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

Fitting the data

Fitting the data

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

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

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