In quantum field theory (QFT), particles are interpreted as excitations or ripples in underlying fields. This conceptual shift from particles being fundamental entities to being manifestations of fields arose from the development of quantum mechanics and our understanding of the behavior of particles at the quantum level.
According to QFT, the fundamental entities of nature are not isolated particles but rather fields that pervade all of space. These fields are associated with specific types of particles, such as the electromagnetic field being associated with photons. Fields are described by mathematical functions that assign a value to each point in space and time.
The concept of fields being more fundamental or "real" than particles stems from a number of reasons:
Conservation Laws: Fields provide a framework that naturally explains the conservation of physical quantities such as energy, momentum, and charge. In QFT, these conservation laws emerge from symmetries associated with the fields and their interactions. The behavior of particles, including their creation and annihilation, is described by the dynamics of these fields.
Relativity and Covariance: Fields are inherently compatible with the principles of special relativity. They allow for the formulation of relativistically covariant equations, meaning the equations retain their form under Lorentz transformations. This is crucial for consistent descriptions of particles moving at high speeds.
Unification of Forces: QFT allows for the unification of different fundamental forces by treating them as different aspects or manifestations of fields. For example, the electromagnetic and weak forces are described by a unified electroweak theory, where the photon and W and Z bosons are associated with different excitations of the underlying field.
Quantization: Fields in QFT are inherently quantized, meaning that they can only exist in discrete energy states or quanta. This naturally accounts for phenomena such as particle creation and annihilation, as well as the discrete nature of certain physical observables.
While particles are observable and interact with detectors, they are considered excitations of the underlying fields. This perspective allows for a more consistent and comprehensive understanding of the behavior and interactions of particles at the quantum level.
It's worth noting that the distinction between fields and particles can sometimes be a matter of interpretation or perspective. In certain contexts, particle-like behavior may be more prominent, while in others, the wave-like or field-like aspects take precedence. The particle-field duality is a fundamental aspect of quantum mechanics and QFT, highlighting the complex and interconnected nature of the quantum world.