arXiv subjects

Rickson Wielian

Publications and source records attributed to Rickson Wielian.

3 recordsLinked to original sources

arXiv2026

Large-Field Vacuum Decay in General Multi-Scalar Theories

Many theories beyond the standard model exhibit multiple scalar particles. Such multi-scalar theories can in principle host lower-energy vacua, and thus predict that our universe has a finite lifetime due to false vacuum decay. This scenario cannot be ruled out a priori as even the standard model's electroweak vacuum has been shown to be metastable; however, for theoretical consistency, we still require that the model does not predict a lifetime much smaller than the age of the universe. The calculation of these tunneling rates at leading order for multi-scalar theories typically includes numerical approaches, or approximations which are frequently not analytically controlled. In this article we show that, in the large-field regime, a one-dimensional radial bounce always produces the exact dominant contribution to the leading order tunneling rate, with corrections being exponentially suppressed. This allows us to write simple analytical expressions to calculate the tunneling rate in multi-scalar theories, in terms of an effective quartic coupling $λ_\text{eff}$. For theories with biquadratic scalar potentials, we also derive straightforward analytical expressions for $λ_\text{eff}$ in terms of the original theory's couplings. Finally, we provide example applications of our results to study the vacuum stability of the 2HDM+a model and the 3-3-1 model.

hep-ph↗

arXiv2024

Transfer Matrix Approach for Topological Edge States

We suggest and develop a novel approach for describing topological properties of a periodic system purely from the transfer matrix associated to a unit cell. Our approach uses the Iwasawa decomposition to parametrise the transfer matrix uniquely in terms of three real numbers. This allows us to obtain simple conditions for the existence of topologically protected edge states and to provide a visual illustration of all possible solutions. In order to demonstrate our method in action, we apply it to study some generalisations of the Su-Schrieffer-Heeger (SSH) model, such as the tetramer SSH4 model and a dimerised one-dimensional photonic crystal. Finally, we also obtained a simple pictorial proof of the Zak phase bulk-edge correspondence for any one dimensional system using this approach.

cond-mat.mes-hall↗

arXiv2022

Phase retrieval from angular streaking of XUV atomic ionization

We demonstrate an accurate phase retrieval of XUV atomic ionization by streaking the photoelectron in a circularly polarized IR laser field. The streaking phase can then be converted to the atomic time delay containing the Wigner and continuum-continuum components. Our demonstration is based on a numerical solution of the time-dependent Schrödinger equation. We test this technique using the hydrogen atom ionized by an isolated attosecond XUV pulse across a wide range of photon energies. In parallel, we run a series of RABBITT simulations and demonstrate equivalence of the phase and timing information provided by the two methods. This validates the proposed technique and makes it a useful tool that can be applied to a broad range of atomic and molecular targets exposed to XUV radiation from novel free-electron laser sources.

physics.atom-ph↗