Physics:Quantum Electroweak theory

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Electroweak theory is a Book I topic in the Quantum Collection. Electroweak theory is the unified quantum field theory that combines the electromagnetic and weak interactions into a single framework based on the gauge symmetry group SU(2)_L \times U(1)_Y. It forms a central part of the Standard Model of particle physics. Electroweak unification: electromagnetic and weak interactions arising from a single gauge structure Electroweak theory is the unified quantum field theory that combines the electromagnetic and weak interactions into a single framework based on the gauge symmetry group SU(2)_L \times U(1)_Y. It forms a central part of the Standard Model of particle physics. Electroweak theory shows that the electromagnetic force and weak nuclear force are different manifestations of a single interaction at high energies.
Quantum Electroweak theory.

Unification of forces

Electroweak theory shows that the electromagnetic force and weak nuclear force are different manifestations of a single interaction at high energies.

At low energies:

  • electromagnetic interaction → long-range force
  • weak interaction → short-range force

At high energies, they merge into a unified electroweak interaction.[1]

Gauge symmetry

The theory is based on the symmetry group: SU(2)L×U(1)Y

where:

  • SU(2)L acts on left-handed fermions
  • U(1)Y corresponds to weak hypercharge

Gauge fields are introduced to preserve local symmetry, leading to four gauge bosons.[2]

Gauge bosons

The electroweak theory predicts four gauge bosons:

  • Wμ1,Wμ2,Wμ3 (from SU(2))
  • Bμ (from U(1))

These combine to form the physical particles:

  • W+ and W− (charged weak bosons)
  • Z0 (neutral weak boson)
  • γ (photon)

This mixing explains how electromagnetic and weak forces are related.[3]

Spontaneous symmetry breaking

The electroweak symmetry is not directly observed because it is spontaneously broken.

This occurs through the Higgs mechanism, introducing a scalar field whose vacuum expectation value selects a specific ground state: ⟨ϕ⟩≠0

As a result:

  • W± and Z0 acquire mass
  • the photon remains massless

This explains the short range of the weak interaction.[4]

Electroweak Lagrangian

The electroweak Lagrangian includes:

  • fermion kinetic terms
  • gauge field terms
  • Higgs field contributions
  • interaction terms

These components together describe the full dynamics of the electroweak interaction.

Weak interactions

The weak interaction involves processes such as:

  • beta decay
  • neutrino interactions
  • flavor-changing processes

These are mediated by the W± and Z0 bosons.

Experimental confirmation

Electroweak theory has been confirmed by numerous experiments, including:

  • discovery of the W and Z bosons
  • precision measurements at particle accelerators
  • observation of the Higgs boson

These results strongly support the validity of the theory.[2]

Role in the Standard Model

Electroweak theory, together with quantum chromodynamics, forms the core of the Standard Model.

It unifies two of the fundamental forces and provides a consistent framework for describing particle interactions.

Conceptual importance

Electroweak theory demonstrates how gauge symmetry and spontaneous symmetry breaking combine to produce realistic physical theories.

It is a cornerstone of modern particle physics and a key step toward deeper unification.

See also

Table of contents (198 articles)

Index

Full contents

9. Quantum optics and experiments (5) Back to index
Experimental quantum physics: qubits, dilution refrigerators, quantum communication, and laboratory systems.
Experimental quantum physics: qubits, dilution refrigerators, quantum communication, and laboratory systems.
14. Plasma and fusion physics (8) Back to index
Conceptual illustration of plasma physics in a fusion context, showing magnetically confined ionized gas in a tokamak and the collective behavior governed by electromagnetic fields and transport processes.
Conceptual illustration of plasma physics in a fusion context, showing magnetically confined ionized gas in a tokamak and the collective behavior governed by electromagnetic fields and transport processes.

References

  1. ↑ Peskin, M. E.; Schroeder, D. V. An Introduction to Quantum Field Theory (1995).
  2. ↑ 2.0 2.1 Schwartz, M. D. Quantum Field Theory and the Standard Model (2014).
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named weinberg
  4. ↑ Higgs, P. W. (1964). Broken symmetries and the masses of gauge bosons.
Author: Harold Foppele


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