According to quantum field theory (QFT), particles are not simply point-like objects but are instead described as excitations of quantum fields that permeate all of space. These fields are fundamental and are not dependent on the presence of an observer to exist.
In quantum field theory, each type of particle is associated with a corresponding field. For example, the electron is associated with the electron field, the photon with the electromagnetic field, and so on. These fields are defined throughout spacetime and interact with each other.
According to the principles of QFT, particles can be created or annihilated through interactions between these fields. The interactions are governed by mathematical equations known as field equations, such as the Dirac equation for the electron field or the Maxwell equations for the electromagnetic field. These equations describe how the fields evolve and how particles can emerge and disappear.
Importantly, in QFT, particles are described as excitations or quanta of their respective fields. These excitations can have properties such as energy, momentum, and spin. Even in the absence of an observer to measure them, these excitations can still exist and undergo interactions according to the dynamics prescribed by the theory.
The concept of particle existence in QFT is not tied to observation but rather to the underlying mathematical framework and the dynamics of the fields. Observations or measurements performed by observers provide information about the properties of particles and their interactions, but they do not fundamentally determine the existence of particles themselves.
In summary, particles in QFT are not dependent on the presence of an observer to exist. They are described as excitations of quantum fields that exist independently and follow the dynamics of the theory. Observers can measure and interact with these particles, but their existence is not contingent upon observation.