Perturbation techniques 3 Perturbation theory Bispectra 1 Cluster expansion 1 Compactification 1 Dielectric perturbation 1 Dual resonator 1 Effective field theory 1 Expansion 1 Frequency shift 1 Goodness of fit 1 Instantons 1 Large scale structure of universe 1 Leading measurement 1 Leading orders 1 Mass gap 1 Metamaterials 1 Methods:statistical 1 Microwave resonators 1 Mode volume 1 N-body simulation 1 Next-to-leading orders 1 Nonperturbative 1 One dimensional photonic crystal 1 Phase sensitivity 1 Photonic crystal cavities 1 Photons 1 Point at infinity 1 Quantum field theory 1 Quantum theory 1