In physics, dimensionless particles typically refer to fundamental particles that do not possess any measurable spatial extent or size. These particles are considered point-like, meaning they are treated as mathematical points without any physical size or extension.
In a three-dimensional universe, the concept of dimensionless particles can be understood within the framework of quantum field theory. According to this theory, particles are described as excitations of underlying fields that permeate all of space. These fields are associated with specific quantum properties, such as electric charge, mass, and spin.
The notion of dimensionless particles arises from the fact that these particles are described solely by their quantum numbers and properties, rather than having a defined size or spatial extent. In other words, their interactions and behaviors are determined by their fundamental properties, such as their mass, charge, and spin, rather than their spatial dimensions.
It's important to note that when we say particles are dimensionless, it does not mean they exist outside the three-dimensional universe. Instead, it means they lack spatial extension within the dimensions we consider. They still exist and interact within the framework of three-dimensional space, but their behavior and properties are not dependent on spatial dimensions.
Quantum field theory provides a mathematical framework to describe and understand the behavior of particles, including those that are dimensionless. It allows us to study the interactions and dynamics of particles within a three-dimensional universe, even though some particles may be considered point-like and lacking spatial dimensions.