Unstable Klein-Gordon Modes in an Accelerating Universe

Unstable Klein-Gordon modes in an accelerating universe Dark Energy -does not behave like particles or radiation Quantised unstable modes -no particle or radiation interpretation Accelerating universe -produces unstable Klein-Gordon modes

Plan Solve K-G coupled to exponentially accelerating space background Canonical quantisation ->Hamiltonian partitioned into stable and unstable components Fundamental units of unstable component have no Fock representation Finite no. of unstable modes + Stone von Neumann theorem -> Theory makes sense

BASICS CM QM QFT -Qm Harmonic -Fock Space Oscillator

Classical Mechanics

Quantum Mechanics

Quantum Harmonic Oscillator

Quantum Field Theory

Fock Space

Klein-Gordon Change to time coordinate K-G becomes

Canonical Quantisation

Hamiltonian Sum of quadratic terms Bogoliubov transformation

Bogoliubov transformation preserves Canonical Commutation Relations

Bogoliubov Transformation

Energy Partitioning

Existence of Preferred Physical Representation Stone-von Neumann Theorem guarantees a preferred representation for H D H L has usual Fock representation There is a preferred representation for the whole system

Cosmological Consequences

Current/Future work This theory is semi-classical Dark energy at really long wavelengths A quantum gravity theory Dark energy at short wavelengths (we hope!)

Horava Gravity (Horava Phys. Rev. D 2009) Candidate for a UV completion General Relativity Higher derivative corrections to the Lagrangian Dispersion relation for scalar fields (Visser Phys. Rev. D 2009)

Development of unstable modes