Physics and field theory are related but distinct concepts.
Physics, in a general sense, is the branch of science that deals with the study of matter, energy, and the fundamental forces that govern the universe. It encompasses a wide range of subfields, such as classical mechanics, electromagnetism, thermodynamics, quantum mechanics, and more. Physics aims to understand the behavior of physical systems, develop mathematical models to describe their properties, and make predictions about their future states.
Field theory, on the other hand, is a specific framework within physics that describes physical phenomena in terms of fields and their interactions. It is particularly relevant in the context of quantum field theory (QFT), which is a framework that combines quantum mechanics and special relativity to describe elementary particles and their interactions.
In classical physics, fields such as the electromagnetic field or gravitational field are used to describe the forces and interactions between objects. These fields are represented by mathematical functions that assign a value to each point in space and time. Classical field theory provides a framework to describe and understand phenomena such as the propagation of waves, the behavior of fluids, and the dynamics of continuous media.
In quantum field theory, fields are treated as quantum mechanical operators that satisfy certain commutation or anticommutation relations. This allows for the quantization of fields, meaning that they can exist in different energy states and particles are regarded as excitations or quanta of these fields. Quantum field theory provides a powerful framework to describe the behavior of elementary particles, their interactions, and the probabilistic outcomes of particle processes.
So, while physics is a broader discipline that encompasses various subfields, field theory is a specific mathematical framework within physics, particularly relevant in the context of quantum field theory, to describe physical phenomena in terms of fields and their interactions.