The Official String Theory Web Site:--> Cosmology :--> The Big Bang :--> Quarks vs. antiquarks

Quarks outnumber antiquarks

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TIME: 10-11 seconds

. At this stage of the Big Bang, the tiny expanding Universe is filled with radiation creating pairs of particles and antiparticles, and pairs of particles and antiparticles annihilating back into radiation.
. We know from observing elementary particles in the present era that every known particle has an antiparticle with the opposite charge and the same spin. (Particles with zero charge are their own antiparticles.) The antiparticle of a quark is called an antiquark. At the beginning of the Big Bang, the Universe was so hot that quarks and antiquarks were created from radiation and annihilated back into radiation at a high rate. There was an equal number of quarks and antiquarks on the average at any one moment.
. But as the Universe expanded, it cooled, and the cooler radiation was less likely to create quark-antiquark pairs. As quarks and antiquarks "froze" out of the radiation background, a greater number of quarks than antiquarks was left over.
. We know this must have happened, because we observe more quarks than antiquarks today. All of the protons and neutrons in all of the elements in the Universe are made out of quarks, not antiquarks. Quarks are clearly more numerous than antiquarks.
. But this quark excess can't be explained using the Standard Model of particle physics. Therefore the domination of quarks over antiquarks is an area where studies of the early Universe could shed light on particle physics we haven't yet been able to study by direct particle scattering in an accelerator.

How old is the Universe? // Structure of the Universe // The Big Bang // Before the Big Bang? // What about string theory?

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