In quantum field theory, the interaction between two electrons that leads to their repulsion can be described using Feynman diagrams. One common representation of this interaction involves the exchange of a virtual photon between the electrons. However, it's important to note that the virtual photon is not a physical particle in the same sense as a real photon. Instead, it is a mathematical construct used to represent the underlying electromagnetic interaction between the electrons.
In Feynman diagrams, the vertical axis represents time, and the horizontal axis represents space. The electrons are represented by solid lines, and the exchange of the virtual photon is depicted by a wavy line connecting the two electron lines. The direction of the arrow on the virtual photon line indicates the direction of the interaction.
The presence of the virtual photon in the Feynman diagram arises from the application of quantum field theory and the rules for calculating particle interactions. According to these rules, the interaction between two charged particles, such as electrons, is mediated by the exchange of gauge bosons—in this case, the virtual photon, which is associated with the electromagnetic force.
The virtual photon is a mathematical representation of the exchange of energy and momentum between the interacting electrons. It is a transient entity that does not exist as a measurable particle in the usual sense. Instead, it represents a disturbance or a fluctuation in the electromagnetic field that occurs during the interaction. The exchange of the virtual photon allows for the transfer of the electromagnetic force between the electrons, resulting in their repulsion.
In summary, the virtual photon in a Feynman diagram representing electron-electron repulsion is a mathematical representation of the exchange of energy and momentum associated with the electromagnetic interaction between the electrons. It is not a physically observable particle but a tool used in quantum field theory calculations to describe the underlying processes.