An Effective Field Theory for large oscillons

Abstract

We consider oscillons — localized, quasiperiodic, and extremely long-living classical solutions in models with real scalar fields. We develop their effective description in the limit of large size at finite field strength. Namely, we note that nonlinear long-range field configurations can be described by an effective complex field ψ(t,x) which is related to the original fields by a canonical transformation. The action for ψ has the form of a systematic gradient expansion. At every order of the expansion, such an effective theory has a global U(1) symmetry and hence a family of stationary nontopological solitons — oscillons. The decay of the latter objects is a nonperturbative process from the viewpoint of the effective theory. Our approach gives an intuitive understanding of oscillons in full nonlinearity and explains their longevity. Importantly, it also provides reliable selection criteria for models with long-lived oscillons. This technique is more precise in the nonrelativistic limit, in the notable cases of nonlinear, extremely long-lived, and large objects, and also in lower spatial dimensions. We test the effective theory by performing explicit numerical simulations of a (d + 1)-dimensional scalar field with a plateau potential.

Quantum decay of scalar and vector boson stars and oscillons into gravitons

“…A perturbative expansion in terms of the spatial gradient or binding energy is often used to determine the configuration of oscillons [74], whereas some systematic approaches to calculate the configuration in the non-relativistic effective field theory are also proposed in refs. [51,[75][76][77][78]. Those objects are realized by the QCD axion after the QCD phase transition in the post-inflationary PQ symmetry breaking scenario [79] and in a large misalignment scenario [80].…”

Oscillon spectroscopy

“…More recently, they have gained substantial interest and several aspects have been further investigated, including their formation, longevity, their classical and quantum radiation as well as the model dependence of their behaviour, see e.g. [6][7][8][9][10][11][12][13][14][15] and [16] for a recent review. Oscillons have been shown to emerge naturally in scenarios ranging from preheating to bubble collisions (see e.g.…”