Photons were, indeed, produced in great numbers by the mutual annihilation of the primitive particles and antiparticles.

ECONOMIST: Particle physics makes sense, but it assumes too much

Fewer than zero particles being present usually means that you have antiparticles instead.

ECONOMIST: Physics and philosophy

When the universe had cooled some more, those particles and antiparticles should have gone on to annihilate one another, leaving only photons behind.

ECONOMIST: Particle physics makes sense, but it assumes too much

These are interesting because they and their antiparticles exhibit CP-violating tendencies.

ECONOMIST: The arrow of time

But there is no such thing as an antiphoton (photons are their own antiparticles, and are pure energy in any case), so that cannot apply here.

ECONOMIST: Physics and philosophy

When inflation ended, and the universe had cooled enough for virtual particles to emerge from the magma, particles and antiparticles should have appeared in exactly equal numbers.

ECONOMIST: Particle physics makes sense, but it assumes too much

Antiparticles frequently only survive for microseconds.

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