Answer:

1.

quantum mechanics

quantum mechanics, science dealing with the behaviour of matter and light on the atomic and subatomic scale. It attempts to describe and account for the properties of molecules and atoms and their constituents—electrons, protons, neutrons, and other more esoteric particles such as quarks and gluons.

2.

A first quantized free photon is a complex massless vector field A=(A^\mu) whose field strength satisfies Maxwell's equations in vacuum. This allows for the construction of the localized states of the photon with a definite sign of energy and helicity.

Answer:

quantum mechanics

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