Wormholes and masses for Goldstone bosons

There exist non-trivial stationary points of the Euclidean action for an axion particle minimally coupled to Einstein gravity, dubbed wormholes. They explicitly break the continuos global shift symmetry of the axion in a non-perturbative way, and generate an effective potential that may compete with QCD depending on the value of the axion decay constant. In this paper, we explore both theoretical and phenomenological aspects of this issue. On the theory side, we address the problem of stability of the wormhole solutions, and we show that the spectrum of the quadratic action features only positive eigenvalues. On the phenomenological side, we discuss, beside the obvious application to the QCD axion, relevant consequences for models with ultralight dark matter, black hole superradiance, and the relaxation of the electroweak scale. We conclude discussing wormhole solutions for a generic coset and the potential they generate.Comment: 50 pages, 15 figures. v2: minor changes, refs adde

Chaotic Vibrations in a Buckled Beam Induced by a Galloping Phenomenon

Chaos theory has spectacularly evolved since the pioneering work by E. Lorenz on chaotic motion in a simple, deterministic system. Since then, the chaotic behavior of many other deterministic, low-dimensional systems in a large variety of fields has been developed. In the particular field of aeroelasticity of aircraft structures several reports of chaos have been documented. However, we are unaware of any report of chaotic systems of civil (non-aeronautical) use induced by an aeroelastic phenomenon. In this paper a well defined civil, aeroelastic system, susceptible to exhibit chaotic behavior is presented. The system consists of a buckled beam from which a second beam is suspended. This last beam (hereafter, galloping beam) has a square cross- section and can undergo transverse galloping. The system is subjected to an uniform wind flow and, as it will be shown in the paper, for wind velocities larger than a threshold value, the galloping beam begins to oscillate and induces, for a determined set of parameter values, a chaotic motion in the buckled bea

The potential of leptonic minimal flavour violation

We explore the possibility of spontaneous lepton flavour symmetry breaking in the context of Minimal Flavour Violation and within a minimal and predictive See-Saw model. In this context the Yukawa couplings are the vacuum expectation values of scalar fields transforming under the flavour group. The scalar potential giving rise to the acquisition of the vev of the scalar fields is derived and analyzed. In the minimization the Majorana character of neutrino masses plays a distinctive role, absent for the quark caseR. A. acknowledge partial support from the European Union FP7 ITN INVISIBLES (Marie Curie Actions,PITN- GA-2011- 289442), CiCYT support through the project FPA2009-09017, CAM partial support through the project HEPHACOS P-ESP-00346 and MICINN support through the grant BES-2010-03786

A primer on Higgs Effective Field Theory with Geometry

These lecture notes, prepared for the 2022 QUC summer school at KIAS, provide an introduction to Higgs Effective Field Theory and the use of field geometry in Quantum Field Theory. While not sounding the depths of any of these topics, we will cover and give a sense of the inner workings of: the action for Goldstone bosons, the independence of scattering amplitudes from field parametrisations, linear vs non-linear realizations --their `geography' and experimental prospects to tell them apart--, ultra-violet completions and the LSZ formula for fields in curved space.Comment: 34 pages, 5 figures, 11 exercises for students to tr