Publications de Oliver Paul C. Janssen

Publications associées (6)

The Axidental Universe

Random axion theories with several hundred fields have enormous numbers of distinct meta-stable minima. A small fraction of these have vacuum energy compatible with current measurements of dark energy. The potential also contains regions suitable for infla ...

IOP Publishing Ltd2025

Positivity bounds on electromagnetic properties of media

Oliver Paul C. Janssen

We study the constraints imposed on the electromagnetic response of general media by microcausality (commutators of local fields vanish outside the light cone) and positivity of the imaginary parts (the medium can only absorb energy from the external field ...

Springer Nature2024

Axion minima in string theory

Oliver Paul C. Janssen

We study the landscape of axion theories in compactifications of type IIB string theory on orientifolds of Calabi-Yau threefolds. In a sample of approximately 400,000 geometries we find that in the regime of perturbative control there are only a handful of ...

SPRINGER2025

KSW criterion in large field models

Oliver Paul C. Janssen

We extend the analytic description of complex no-boundary solutions in the context of inflation to large field models. We discuss the Kontsevich-Segal-Witten (KSW) criterion and find it is satisfied in small field models, while in large field models it dep ...

IOP Publishing Ltd2024

Kontsevich-Segal criterion in the no-boundary state constrains anisotropy

Oliver Paul C. Janssen

We show that the Kontsevich-Segal-Witten (KSW) criterion applied to the no-boundary state constrains anisotropic deformations of de Sitter space. We consider squashed S3 and S1×S2 boundaries and find that, in both models, the KSW criterion excludes a signi ...

2025

Non-analyticity of the S-matrix with spontaneously broken Lorentz invariance

Oliver Paul C. Janssen

We study the S-matrix of Goldstones in the renormalizable theory of a U(1) complex scalar at finite charge, i.e. in a state that breaks Lorentz invariance. The theory is weakly coupled so that this S-matrix exists at all energies. Unlike the Lorentz invari ...

Springer Nature2024