3 papers
gr-qc2026
Bumblebee Gravity -- Lessons from Perturbation Theory
Nils A. Nilsson
These proceedings summarise some recent efforts in understanding a class of vector-tensor theories known as {\it bumblebee} models, which spontaneously break local Lorentz and diff…
gr-qc2026
There and back again -- Closed timelike curves as EFT selection principle
Bum-Hoon Lee, Nils A. Nilsson, Somyadip Thakur
Modified gravity is often approached in the context of effective-field theory (EFT), with the view that the EFT corrections permit a more desirable theory. In this paper, we posit…
hep-th2026
A no-go theorem in bumblebee vector-tensor cosmology
Carsten van de Bruck, Mohammad Ali Gorji, Nils A. Nilsson +2
Bumblebee models, a class of vector-tensor theories in which a vector field acquires a nonzero vacuum expectation value that spontaneously breaks spacetime symmetries, are ubiquito…