What is the source of the fields in quantum field theory?

The origin of the concept of the field lies in the 18th century, when the spatial distribution of certain variables was discussed in continuum mechanics and fluid mechanics.It was not considered to be a separate entity and the dynamics of the fields were derived from the properties of the molecules or volume elements underlying the field using the Newtonian particle mechanics. The field concept gained a completely new meaning due to the emerging electrodynamics at the end of the 19th century, since the electromagnetic field could not be explained as a macroscopic state constructed from microscopic subsystems.The electromagnetic field became a new irreducible entity. Michael Faraday and James Clerk Maxwell still believed that the electromagnetic field is only an excited state of the aether and thus led the field to motion or mechanical tensions in a matter-form, the aether, back.But the Michelson-Morley experiment contradicted the aether theory.The existence of the aether, which fills the empty space, was henceforth discarded in physics. The observation that the electromagnetic field also exists in vacuum, without carrier matter, without an invisible carrier substance such as the aether, led to the electric field being regarded as an independent physical system.

Today, the concept of field is (at least) equal to the concept of matter.The empty space can contain both matter and fields. Finally, in quantum field theory, the matter particles are also regarded as field quanta, i.e. quantified excitations of fields.The question of whether particles or fields are ultimately the more “fundamental” in nature is still controversial (2018). Most physicists, however, believe that there are no localized particles or empty space, but only fields (and their quantums, which can be found at any point where the field is not zero).

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