Abnormal Bound Systems

TL;DR

This paper discusses a class of bound systems dominated by massless exchange particles, which are relativistic and cannot be described by traditional Schrödinger equations, challenging conventional understanding of bound states.

Contribution

It introduces the concept of abnormal bound systems dominated by exchange particles, extending previous theoretical findings to a more general physical context.

Findings

Existence of bound systems dominated by exchange particles.

Such systems are relativistic and involve massless constituents.

They cannot be described by the Schrödinger equation.

Abstract

It is taken for granted that bound systems are made of massive constituents that interact through particle exchanges (charged particles interacting via photon exchanges, quarks in elementary particles interacting via gluon exchanges, and nucleons in nuclei interacting via meson exchanges). However, as was recently theoretically found, there exist systems dominated by exchange particles (at least for the zero exchange masses). In these systems, the contribution of massive constituents is negligible. These systems have a relativistic nature (since they are mainly made of massless particles moving at the speed of light), and therefore, they cannot be described by the Schroedinger equation. Though these results were found so far in the simple Wick--Cutkosky model (spinless constituents interacting via the ladder of spinless massless exchanges), the physical ground for their existence seems to be rather general.