Cosmology Seminar: Robert Hagala

Robert Hagala is a PhD student at the ITA

Waves in Scalar-Tensor Theories

Many viable Scalar-Tensor theories for modified gravity introduce scalar 
fields that are coupled to matter. The equations that describe the 
evolution of the scalar fields are field equations similar to the 
Klein-Gordon equation, with additional source terms depending on the 
specific model.
The usual way to solve the scalar field equation for a given model, has 
been to apply the quasi-static approximation, thus neglecting the time 
derivatives and solving it like a Poisson equation. We have developed a 
method to integrate the full field equation numerically, allowing for 
new phenomena not seen when using the quasi-static approximation.
We present results from our latest research, studying waves arising when 
solving the full field equations in spherical symmetry. As examples, 
we use the Symmetron model and the Disformally coupled model, where the 
propagation of waves has surprising effects. We show how these new 
effects can lead to further constraints on the models, and to new 


Bridget Falck and Benjamin Racine
Published Nov. 22, 2016 1:14 PM - Last modified Nov. 22, 2016 1:14 PM