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Combustion can create energy by breaking/creating bonds between atoms via the electromagnetic force to produce a resultant lower energy system. Nuclear fusion and fission processes can create energy by producing particular nuclei which are more stable than their precursors via the strong force which lowers the resultant system's energy.

Matter and its corresponding antimatter can create energy by annihilation. But what is the force that mediates this process? Why does this force not operate similarly during matter-matter or antimatter-antimatter interaction?

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The force mediating matter-antimatter annihilation depends on what particle(s) get produced by the annihilation. For example, when an electron and a positron annihilate to two photons, the electromagnetic force is involved. But when they annihilate to a Z boson, which can happen at sufficiently high energies, the weak nuclear force is involved. They are also presumed to have a miniscule chance of annihilating to two gravitons, in which case the gravitational force is involved.

Two electrons, or two positrons, cannot annihilate to two photons, or to a Z boson, or to two gravitons, because this would violate the conservation of electric charge.

Although annihilation seems dramatic, you should not think of it as something special. When you think about Feynman diagrams, it looks similar to scattering. And of course it doesn't "create energy"; it just rearranges the existing energy into different particles.

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When discussing elementary particle interactions and the interactions of composite systems from these particles one is in the realm of quantum mechanics and special relativity. In quantum mechanics there are four fundamental forces , electromagnetic, strong, weak and gravitational ( presuming quantization of gravity).These are the forces which may be involved in any elementary systems' interactions, including when annihilation is observed. There are no annihilation forces.

Annihilation is the result of the combination of the two systems, quantum mechanics and special relativity. In special relativity, every particle and system of particles is represented by a four vector, and at the framework where the system is at rest, i.e. the momentum zero the mass of the system is identical with energy. $$m_0^2c^2=\biggl(\frac{E}{c}\biggr)^2-||\mathbf{p}||^2$$ Or in natural units where $c=1$, $$m_0^2=E^2-||\mathbf{p}||^2$$ Quantum mechanics then enters, which has conserved quantum numbers, and thus does not allow everything to annihilate with everything else in an interaction. Quantum numbers have to be conserved, and that is why baryons annihilate with antibaryons ,(conservation of baryon number), electrons with positrons (conservation of lepton number) etc.

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  • $\begingroup$ If you mean that no forces are involved in annihilation, I don't agree. An electron and a positron annihilating to two photons involves the standard electromagnetic vertex... the same one involved in, say, electron-positron scattering. And the only way to calculate the annihilation amplitude is to calculate Feynman diagrams for the specific forces involved. I do agree that there is not a separate "annihilation force" different from the four fundamental forces. $\endgroup$ – G. Smith Jul 15 '18 at 4:56
  • $\begingroup$ @G.Smith i will clarify $\endgroup$ – anna v Jul 15 '18 at 5:02

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