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Linné on line arrow Physics and the Cosmos arrow Macrocosmos arrow Big Bang arrow The electroweak era

The electroweak era

When the temperature has decreased further there is not enough energy to create very heavy (hypothetical) particles. Still, the energy is high enough that all the particles that we know of, as part of the Standard Model, can still be produced. Heavier particles disappear more and more as they decay into lighter particles.

Some particles cannot decay anymore, due to the conservation of some quantum numbers. Such particles could still be present in the Universe today as part of the dark matter. One example of such a hypothetical particle is the neutralino, which is part of the Supersymmetric extension of the Standard Model.

One problem within the Big Bang-model is that the average particle energy decreases with 12 orders of magnitude during this epoch (from 1023 to 1011 eV). The phenomenon that the energy decreases so much without any big physical change is not expected when one compares with other phases and therefore somewhat worrying. This period is sometimes called the great desert due to the feature that "nothing" happens.

The temperature at the end of this period has become so low that the electroweak Z,W-bosons are no longer produced in large quantities and they decrease in number as they decay. In the next phase of the evolution quarks become bound and form hadrons.