In physical cosmology, the electroweak epoch was the period in the evolution of the early universe when the temperature of the universe had fallen enough that the strong force separated from the electronuclear interaction, but was still high enough for

electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...

and the

weak interaction In nuclear physics and particle physics, the weak interaction, weak force or the weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, and gravitation. It is th ...

to remain merged into a single electroweak interaction above the critical temperature for electroweak symmetry breaking (159.5±1.5 GeV in the

Standard Model The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

of particle physics). Some cosmologists place the electroweak epoch at the start of the inflationary epoch, approximately 10⁻³⁶ seconds after the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

. Others place it at approximately 10⁻³² seconds after the Big Bang, when the potential energy of the inflaton field that had driven the

inflation In economics, inflation is an increase in the average price of goods and services in terms of money. This increase is measured using a price index, typically a consumer price index (CPI). When the general price level rises, each unit of curre ...

of the universe during the inflationary epoch was released, filling the universe with a dense, hot quark–gluon plasma. Particle interactions in this phase were energetic enough to create large numbers of exotic particles, including W and Z bosons and

Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...

s. As the universe expanded and cooled, interactions became less energetic, and when the universe was about 10⁻¹² seconds old, W and Z bosons ceased to be created at observable rates. The remaining W and Z bosons decayed quickly, and the weak interaction became a short-range force in the following quark epoch. The electroweak epoch ended with an electroweak phase transition, the nature of which is unknown. Speculation in the 1990s that it may be a first order transition suggested it could source a gravitational wave background and a baryogenesis, provided the Sakharov conditions are satisfied and in Russian, republished as and the Higgs boson energy was below 45 GeV. Subsequent work with the

and a measurement of the Higgs boson as over 114GeV, showed the transition during the electroweak epoch was not a first- or a second-order

phase transition In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic Sta ...

but a continuous crossover, preventing any baryogenesis, or the production of an observable gravitational wave background. However, many extensions to the Standard Model including

supersymmetry Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...

and the two-Higgs-doublet model have a first-order electroweak phase transition (but require additional CP violation).

References

* Physical cosmology Big Bang {{physical-cosmology-stub

See also

References