Publications (27)
The non-adiabatic pressure in general scalar field systems
Adam J. Christopherson, Karim A. Malik
We discuss the non-adiabatic or entropy perturbation, which controls the evolution of the curvature perturbation in the uniform density gauge, for a scalar field system minimally c…
Vorticity from isocurvature in the early universe
Adam J. Christopherson, Karim A. Malik
Vorticity is ubiquitous in nature however, to date, studies of vorticity in cosmology and the early universe have been quite rare. In this paper, based on a talk in session CM1 of…
Relating metric and covariant perturbation theories in gravity
Adam J. Christopherson
Modified theories of gravity have been invoked recently as an alternative to dark energy, in an attempt to explain the apparent accelerated expansion of the universe at the present…
New astrophysical bounds on ultralight axionlike particles
Nilanjan Banik, Adam J. Christopherson, Pierre Sikivie +1
Motivated by tension between the predictions of ordinary cold dark matter (CDM) and observations at galactic scales, ultralight axionlike particles (ULALPs) with mass of the order…
Modelling non-dust fluids in cosmology
Adam J. Christopherson, J. C. Hidalgo, Karim A. Malik
Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or `dust', this approach gives the correct resul…
Calculating Non-adiabatic Pressure Perturbations during Multi-field Inflation
Ian Huston, Adam J. Christopherson
Isocurvature perturbations naturally occur in models of inflation consisting of more than one scalar field. In this paper we calculate the spectrum of isocurvature perturbations ge…