Book contents
- Frontmatter
- Dedication
- Contents
- Preface to the First Edition
- Preface to the Second Edition
- A note on the choice of metric
- Text website
- Part 1 Effective field theory: the StandardModel, supersymmetry, unification
- Part 2 Supersymmetry
- 9 Supersymmetry
- 10 A first look at supersymmetry breaking
- 11 The Minimal Supersymmetric Standard Model
- 12 Supersymmetric grand unification
- 13 Supersymmetric dynamics
- 14 Dynamical supersymmetry breaking
- 15 Theories with more than four conserved supercharges
- 16 More supersymmetric dynamics
- 17 An introduction to general relativity
- 18 Cosmology
- 19 Particle astrophysics and inflation
- Part 3 String theory
- Part 4 Appendices
- References
- Index
14 - Dynamical supersymmetry breaking
from Part 2 - Supersymmetry
- Frontmatter
- Dedication
- Contents
- Preface to the First Edition
- Preface to the Second Edition
- A note on the choice of metric
- Text website
- Part 1 Effective field theory: the StandardModel, supersymmetry, unification
- Part 2 Supersymmetry
- 9 Supersymmetry
- 10 A first look at supersymmetry breaking
- 11 The Minimal Supersymmetric Standard Model
- 12 Supersymmetric grand unification
- 13 Supersymmetric dynamics
- 14 Dynamical supersymmetry breaking
- 15 Theories with more than four conserved supercharges
- 16 More supersymmetric dynamics
- 17 An introduction to general relativity
- 18 Cosmology
- 19 Particle astrophysics and inflation
- Part 3 String theory
- Part 4 Appendices
- References
- Index
Summary
One of the original reasons for the interest in supersymmetry was the possibility of dynamical supersymmetry breaking. So far, however, we have exhibited models in which supersymmetry is unbroken in the true ground state, as in the case of QCD with only massive quarks or models with moduli spaces or approximate moduli spaces. In this chapter, we describe a number of models in which a non-trivial dynamics breaks supersymmetry. We will see that dynamical supersymmetry breaking occurs under special, but readily understood, conditions. In some cases we will be able to exhibit this breaking explicitly, through systematic calculations. In others we will have to invoke more general arguments. Then we will turn to theories in which supersymmetry is preserved in the lowest energy state but in which there exist metastable states with broken supersymmetry. We will argue that this is a generic phenomenon and see that it is even sometimes true in massive QCD.
Models of dynamical supersymmetry breaking
We might ask why, so far, we have not found supersymmetry to be dynamically broken. In supersymmetric QCD with massive quarks, we might give the Witten index as an explanation. We might also note that there is no promising candidate for a goldstino. With massless quarks we have flat directions and, as the fields get larger, the theory becomes more weakly coupled so that any potential tends to zero.
This suggests two criteria for finding models with dynamical supersymmetry breaking (DSB).
The theory should have no flat directions at the classical level.
The theory should have a spontaneously broken global symmetry.
The second criterion implies the existence of a Goldstone boson. If the supersymmetry were unbroken, any would-be Goldstone boson must lie in a multiplet with another scalar as well as a Weyl fermion. This other scalar, like the Goldstone particle, has no potential so the theory has a flat direction. But, by assumption, the theory classically (and therefore almost certainly quantum mechanically) has no flat direction. So supersymmetry is likely to be broken. These criteria are heuristic but, in practice, when a systematic analysis is possible, they always turn out to be correct.
- Type
- Chapter
- Information
- Supersymmetry and String TheoryBeyond the Standard Model, pp. 198 - 210Publisher: Cambridge University PressPrint publication year: 2016