6 papers
Disformal Maps: Classification and Singular Dynamics
Mohammad Ali Gorji, Pavel Jiroušek, Alexander Vikman +1
Being agnostic about the field content of a gravitational system, we consider a general disformal transformation of the metric, , on a four-dimensional Lore…
Quantum mechanics with a ghost: Counterexamples to spectral denseness
Cédric Deffayet, Atabak Fathe Jalali, Aaron Held +2
We quantise integrable point-particle systems with opposite-sign kinetic terms and nontrivial interactions. Using methods from separability theory, we show that previously determin…
Unitary Time Evolution and Vacuum for a Quantum Stable Ghost
Cédric Deffayet, Atabak Fathe Jalali, Aaron Held +2
We quantize a classically stable system of a harmonic oscillator polynomially coupled to a ghost with negative kinetic energy. We prove that due to an integral of motion with a pos…
On the Bondi accretion of a self-interacting complex scalar field
Dražen Glavan, Alexander Vikman, Tom Zlosnik
Scalar fields with a global U(1) symmetry often appear in cosmology and astrophysics. We study the spherically-symmetric, stationary accretion of such a classical field onto a Schw…
Causality and Stability from Acoustic Geometry
Ignacy Sawicki, Georg Trenkler, Alexander Vikman
In scalar-tensor theories with derivative interactions, backgrounds spontaneously break local Lorentz invariance. We study the motion of perturbations of the scalar, "phonons", on…
Ghostly interactions in (1+1) dimensional classical field theory
Cédric Deffayet, Aaron Held, Shinji Mukohyama +1
We investigate the classical stability of two coupled scalar fields with opposite-sign kinetic terms evolving in 1+1 dimensional Minkowski spacetime. In the first part, we characte…