- Tunable tachyon mass in the PT-broken massive Thirring model(arXiv)
Abstract : We study the full phase diagram of a non-Hermitian PT-symmetric generalization of the paradigmatic two-dimensional massive Thirring model. Employing the non-perturbative functional renormalization-group, we find that the model hosts a regime where PT symmetry is spontaneously broken. This new phase is characterized by a relevant imaginary mass, corresponding to monstronic excitations displaying exponentially growing amplitudes for time-like intervals and tachyonic (Lieb-Robison-bound breaking, oscillatory) excitations for space-like intervals. Furthermore, since the phase manifests itself as an unconventional attractive spinodal fixed point, which is typically unreachable in finite real-life systems, we find that the effective renormalized mass reached can be tuned through the microscopic parameters of the model. Our results further predict that the new phase is robust to external gauge fields, contrary to the celebrated BKT phase in the PT unbroken sector. The gauge field then provides an effective and easy means to tune the renormalized imaginary mass through a wide range of values, and therefore the amplitude growth/oscillation rate of the corresponding excitations
2.Attracting the Electroweak Scale to a Tachyonic Trap (arXiv)
Abstract : We propose a new mechanism to dynamically select the electroweak scale during inflation. An axion-like field φ that couples quadratically to the Higgs with a large initial velocity towards a critical point φc where the Higgs becomes massless. When φ crosses this point, it enters a region where the Higgs mass is tachyonic and this results into an explosive production of Higgs particles. Consequently, a back-reaction potential is generated and the field φ is attracted back to φc. After a series of oscillations around this point it is eventually trapped in its vicinity due to the periodic term of the potential. The model avoids transplanckian field excursions, requires very few e-folds of inflation and it is compatible with inflation scales up to 105 GeV. The mass of φ lies in the range of hundreds of GeV to a few TeV and it can be potentially probed in future colliders.