Spontaneous Symmetry Breaking
A physics phenomenon where the underlying mathematical equations of a system possess symmetry, but the ground state (vacuum) drops into a non-symmetric state.
Governing formula
Vacuum Expectation Value ⟨0|φ|0⟩ = v ≠ 0
SI unit
Energy VEV (GeV)
In depth
Essential to the Brout-Englert-Higgs mechanism in electroweak theory. At high energies, electromagnetic and weak forces are unified under symmetric SU(2)×U(1) gauge group; as the universe cooled, the Higgs field settled into a non-zero vacuum state, breaking symmetry and endowing W/Z bosons with mass.
Examples in the real world
Electroweak symmetry breaking separating unified electroweak force into long-range electromagnetism and short-range weak nuclear force.