Abstract
So far we have concentrated on the chiral symmetry of the QCD Hamiltonian and the explicit symmetry breaking by the quark masses. We have discussed the importance of chiral symmetry for the properties of Green functions with particular emphasis on the relations among different Green functions as expressed through the chiral Ward identities. Now it is time to address a second aspect which, for the low-energy structure of QCD, is equally important, namely, the concept of spontaneous symmetry breaking. A (continuous) symmetry is said to be spontaneously broken or hidden if the ground state of the system is no longer invariant under the full symmetry group of the Hamiltonian. In this chapter we will first illustrate this by means of a discrete symmetry and then turn to the case of a spontaneously broken continuous global symmetry.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsNotes
- 1.
The case of a quantum field theory with an infinite volume \(V\) has to be distinguished from, say, a nonrelativistic particle in a one-dimensional potential of a shape similar to the function of Fig. 2.2. For example, in the case of a symmetric double-well potential, the solutions with positive parity always have lower energy eigenvalues than those with negative parity (see, e.g., Ref. [11]).
- 2.
The field \(\Upphi'\) instead of \(\Upphi\) is assumed to vanish at infinity.
- 3.
For continuous symmetry groups one may have a non-countably infinite number of ground states.
- 4.
- 5.
- 6.
The Lagrangian is invariant under the full group O(3) which can be decomposed into its two components: the proper rotations connected to the identity, SO(3), and the rotation-reflections. For our purposes it is sufficient to discuss SO(3).
- 7.
We say, somewhat loosely, that \(T_1\;\hbox{and}\;T_2\) do not annihilate the ground state or, equivalently, finite group elements generated by \(T_1\;\hbox{and}\;T_2\) do not leave the ground state invariant. This should become clearer later on.
- 8.
The restriction to compact groups allows for a complete decomposition into finite-dimensional irreducible unitary representations.
- 9.
Using the replacements \(Q_k\to \hat l_k\;\hbox{and}\;\Upphi_l\to\hat x_l,\) note the analogy with \(i[\hat l_k,\hat x_l]=-\varepsilon_{klm}\hat x_m.\)
- 10.
The abbreviation \(\sum\!\!\!\!\!\!\!\!\int_n|n\rangle\langle n|\) includes an integral over the total momentum \(\vec{p}\) as well as all other quantum numbers necessary to fully specify the states.
References
Bardeen, J., Cooper, L.N., Schrieffer, J.R.: Phys. Rev 106, 162 (1957)
Bardeen, J., Cooper, L.N., Schrieffer, J.R.: Phys. Rev. 108, 1175 (1957)
Bernstein, J.: Rev. Mod. Phys 46, 7 (1974) (Erratum, ibid. 47, 259 (1975))
Bogoliubov, N.N.: Sov. Phys. JETP 7, 41 (1958)
Bogoliubov, N.N.: Zh. Eksp. Teor. Fiz 34, 58 (1958)
Cheng, T.P., Li, L.F.: Gauge Theory of Elementary Particle Physics (Chap. 5.3). Clarendon, Oxford (1984)
Gell-Mann, M., Lévy, M.: Nuovo. Cim. 16, 705 (1960)
Georgi, H.: Weak Interactions and Modern Particle Theory (Chaps. 2.4–2.6). Benjamin/Cummings, Menlo Park (1984)
Goldstone, J.: Nuovo. Cim. 19, 154 (1961)
Goldstone, J., Salam, A., Weinberg, S.: Phys. Rev. 127, 965 (1962)
Greiner, W.: Theoretical Physics. Quantum Theory, vol. 4a (in German). Deutsch, Thun (1985)
Li, L.F., Pagels, H.: Phys. Rev. Lett. 26, 1204 (1971)
Nambu, Y.: Phys. Rev. Lett. 4, 380 (1960)
Nambu, Y., Jona-Lasinio, G.: Phys. Rev. 122, 345 (1961)
Nambu, Y., Jona-Lasinio, G.: Phys. Rev. 124, 246 (1961)
Ryder, L.H.: Quantum Field Theory (Chap. 8). Cambridge University Press, Cambridge (1985)
Schwinger, J.S.: Ann. Phys. 2, 407 (1957)
Weinberg, S.: The Quantum Theory of Fields. Modern Applications, vol. 2 (Chap. 19). Cambridge University Press, Cambridge (1996)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2011 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Scherer, S., Schindler, M.R. (2011). Spontaneous Symmetry Breaking and the Goldstone Theorem. In: A Primer for Chiral Perturbation Theory. Lecture Notes in Physics, vol 830. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-19254-8_2
Download citation
DOI: https://doi.org/10.1007/978-3-642-19254-8_2
Published:
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-19253-1
Online ISBN: 978-3-642-19254-8
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)