*Project 14:*

## Stress testing the dark energy equation of state imprint on supernova data

This work determines the degree to which a standard Lambda-CDM analysis based on type Ia supernovae can identify deviations from a cosmological constant in the form of a redshift-dependent dark energy equation of state w(z).

We introduce and apply a novel random curve generator to simulate instances of w(z) from constraint families with increasing distinction from a cosmological constant. After producing a series of mock catalogs of binned type Ia supernovae corresponding to each w(z) curve, we perform a standard Lambda-CDM analysis to estimate the corresponding posterior densities of the absolute B-band magnitude of type Ia supernovae, the present-day matter density, and the equation of state parameter.

Using the Kullback-Leibler divergence between posterior densities as a difference measure, we demonstrate that a standard type Ia supernova cosmology analysis has limited sensitivity to extensive redshift dependencies of the dark energy equation of state. In addition, we report that larger redshift-dependent departures from a cosmological constant do not necessarily manifest easier-detectable incompatibilities with the Lambda-CDM model.

Our results suggest that physics beyond the standard model may simply be hidden in plain sight.

Full citation: Moews *et al.*, 2019, Physical Review D, Volume 99, Issue 12, id.123529

This project is a result from COIN Residence Program #5 – Chania, Greece/2018.

Pre-print – Bibtex – Random curve generator

Team:

Ben Moews, U. Edinburgh (UK)

Rafael S. de Souza, U. North Carolina (USA)

Emille E. O. Ishida, CNRS/UCA (France)

Alex I. Malz, New York U. (USA)

Caroline Heneka, Scuola Normale Superiore di Pisa (Italy)

Ricardo Vilalta, U. Houston (USA)

Joe Zuntz, U. Edinburgh (UK)