Abstract We consider the three-dimensional stationary Schrödinger equation deformed by Dunkl operators, and constrained to the surface of a torus. After separation of variables in toroidal coordinates, it is shown that the Schrödinger equation admits solutions in terms of Heun functions, provided the potential has a certain form. As an application, elementary solutions of bound-state type are constructed that are expressed through Heun polynomials.

Abstract Few-body scattering and loosely bound states in the vicinity of an isolated narrow Feshbach resonance are well described by a conceptually simple contact interaction two-channel model, where an open atomic continuum channel is coupled to a closed molecular channel. However, real systems are often characterized by the multiplicity of both continuum and molecular channels. Here we develop a systematic framework to deal with multi-channel problems within a contact interaction approximation. We demonstrate the differences and similarities of adding a molecular or atomic channel to the two-channel model. By means of direct comparison, we show that while an additional atomic channel makes loosely bound states shallower, an additional molecular channel makes them more deeply bound. This approach facilitates the study of the influence of multi-channel environments on few-body physics in a systematic manner by gradually increasing the level of complexity. Furthermore, we account for real atomic systems whose understanding can benefit from this study.

We present the experimental apparatus enabling the observation of the heteronuclear Efimov effect in an optically trapped ultracold mixture of 6Li-133Cs with high-resolution control of the interactions. A compact double-species Zeeman slower consisting of four interleaving helical coils allows for a fast-switching between two optimized configurations for either Li or Cs and provides an efficient sequential loading into their respective MOTs. By means of a bichromatic optical trapping scheme based on species-selective trapping we prepare mixtures down to 100 nK of 1×104 Cs atoms and 7×103 Li atoms. Highly stable magnetic fields allow high-resolution atom-loss spectroscopy and enable to resolve splitting in the loss feature of a few tens of milligauss. These features allowed for a detailed study of the Efimov effect.

In this work, we present a study on the role of atomic configurations in forming van der Waals molecules through three-body recombination. Fixing the angle between the two momenta associated with the Jacobi vectors, we calculate the reaction probability for a specific configuration. In this way, we elucidate the nature of the total reaction probability in reactions X + He + He→XHe + He, which is essential for understanding van der Waals molecules formation in molecular beams and buffer gas cells.

Despite its role in the continuing evolution of the Universe, only a small fraction of the mass of visible material can be attributed to the Higgs boson alone. The overwhelmingly dominant share may/should arise from the strong interactions that act in the heart of nuclear matter; namely, those described by quantum chromodynamics. This contribution describes how studying and explaining the attributes of pseudoscalar mesons can open an insightful window onto understanding the origin of mass in the Standard Model and how these insights inform our knowledge of hadron structure. The survey ranges over distribution amplitudes and functions, electromagnetic and gravitational form factors, light-front wave functions, and generalized parton distributions. Advances made using continuum Schwinger function methods and their relevance for experimental efforts are highlighted.

We summarize the main properties of the so called ''abnormal solutions'' of the Wick--Cutkosky model, i.e. two massive scalar particles interacting via massless scalar exchange ("photons"), within the Bethe--Salpeter equation. These solutions do not exist in the non-relativistic limit, in spite of having very small binding energies. They present a genuine many-body character dominated by photons, with a norm of the valence constituent wave function (two-body norm) that vanishes in the limit of zero binding energy. We present new results concerning the massive-exchange case, in particular determine under which conditions is it possible to obtain such peculiar solutions without spoiling the model by tachyonic states ($M^2<0$).