Contents

# Contents

## Idea

The Higgs field or Higgs boson is a scalar physical field/fundamental particle in a gauge theory such as the standard model of particle physics supposedly responsible for the spontaneously broken symmetry of the electroweak field (electroweak symmetry breaking) and for giving elementary particles their masses by the Higgs mechanism.

## Properties

### Mass and vacuum (in-)stability

The rest mass of the Higgs particle observed at the LHC experiment is about $125$ GeV (ATLAS Collaboration 12, CMS Collaboration 12, ATLAS Collaboration 15, see Gibbs 11a, HLL 11 for early discussion).

This is determined by a local minimum of the Higgs potential (see Kusenko 15 for exposition):

Curiously, the Higgs potential is such that the Higgs field at this mass is at least close to being at the border between vacuum stability and false vacuum. This was highlighted before the actual measurement (EEGHR 09, Gibbs 11b):

Then it was amplified again after the detection of the Higgs particle at the LHC (DVEEGI 12):

More detailed computation at 2-loop confirmed this result, showing that the observed Higgs vacuum is indeed very close to the boundary between the stable and the meta-stable region (BKPV 15):

In summary (Kusenko 15):

$[$The$]$ conclusion is that the best theoretical fit to measured parameters, including the Higgs and top-quark masses, points to a metastable Universe. However, their analysis also concludes that values of parameters are closer to a region of absolute stability than suggested by previous studies: it is possible for the Universe to be fully stable (and for the standard model to work all the way up to the Planck scale), if the true values of measured parameters are only 1.3 standard deviations away from the current best estimates.

However quantum tunneling/vacuum decay is an intrinsically non-perturbative effect which needs careful treatment beyond perturbative quantum field theory (e.g. AFFS 17)

graphics grabbed form Schwartz 15, slide 44

### Possible causes of the near criticality

Given, by the above discussion, that the parameters of the Higgs field are observed to be inside a special reason of their potential parameter space, it is natural to speculate that there is some mechanism that enforces or at least prefers this position.

In BDGGSSS 13, Section 5.2 is speculation that for dynamics over a landscape of vacua critical points may generally serve as attractors.

More specifically, Isidori-Pattori 17 claims that, under reasonable assumptions (including gauge coupling unification, but excluding “naturalness”) supersymmetric-extensions of the standard model of particle physics (MSSM) predict a parameter range for the top quark and Higgs field mass that is close to coinciding with the corresponding parameter space for Higgs field near criticality:

graphics grabbed from Isidori-Pattori 17

That supersymmetry, possibly in a G2-MSSM, would be a natural mechanism behind the near criticality of the Higgs field was also claimed in Kane 18, “Clue 4”.

### Cosmological instability?

However, it has been argued that an actual false vacuum of the Higgs is incompatible with cosmology, as due to vacuum fluctuations during inflation the vacuum decay would not have been avoided (EGR 07, HKSZ 14, EGMRSST 15, EKSYZ 16). In (BDGGSSS 13, section 7, Kane 18 , “Clue 4”) it was argued that this suggests a further principle which prevents the vacuum instability and that a natural such principle is supersymmetry. (This argument has a long history, see Gibbs 11b).

### Asymptotic safety?

The near criticality of the Higgs field vacuum discussed above implies that the coefficient $\lambda$ of the quartic part of the Higgs potential is close to zero after renormalization group flow (“RGE”) to around the Planck scale of about $10^{19}$ GeV (e.g. BDGGSSS 13, p. 17-18):

In fact also the beta function $\beta_\lambda$ of the quartic coupling $\lambda$ (i.e. its logarithmic derivative with respect to scale) is close to zero around the Planck scale of about $10^{19}$ GeV (BDGGSSS 13, p. 18):

Earlier it has been suggested that this reflects the principle of asymptotic safety (Shaposhnikov-Wetterich 09). But this would mean that not only $\lambda$ and its RGE-derivative $\beta_\lambda$ vanish around the Planck scale, but that in fact all higher derivatives do, too (see e.g. Niedermaier 06, equation (1.5)) hence that $\beta_\lambda$ asymptotes to zero. But this does not seem to be the case; in (BDGGSSS 13, p. 17-18) it says:

As shown in fig. 2 (upper right), the corresponding Higgs quartic beta-function vanishes at a scale of about $10^{17}$-$10^{18}$ GeV. In order to quantify the degree of cancellation in the β-function, we plot in fig. 2 (lower right) $\beta_\lambda$ in units of its pure top quark contribution. The vanishing of $\beta_\lambda$ looks more like an accidental cancellation between various large contributions, rather than an asymptotic approach to zero.

### Higgs inflation?

Starting with Jegerlehner 13 has been argued that the near-criticality of the Higgs potential is in fact consistent or even necessary for Higgs inflation to be a viable model. See Jegerlehner 18.

## Models

There is no lack of proposals for realizing the Higgs field in various big schemes of mathematical structures modelling physics.

For instance

• in the technicolor model the Higgs field is not a fundamental particle but a compound of fermions. This realizes the Higgs effect entirely in ordinary gauge theory;

• in noncommutative geometry it has been shown that the Higgs may be modeled as a component of the gauge bosons assuming that the KK-reduction is over a certain non-commutative space of classical dimension 0.

## History

The Higgs mechanism was proposed in 1963-1964 by a fair number of authors essentially simultaneously, see the References below. The explicit prediction of the Higgs boson implied by this mechanism though seems to be solely due to (Higgs 64).

The Higgs boson (or at least something very much like it) was finally detected in 2013 at the LHC experiment.

So for the Higgs particle prediction and experimental detection lie apart by about 50 years. Compare maybe to the neutrino, which was predicted in 1930 and detected in 1956, about 26 years later.

standard model of particle physics and cosmology

theory:Einstein-Yang-Mills-Dirac-Higgs
gravityelectroweak and strong nuclear forcefermionic matterscalar field
field content:vielbein field $e$principal connection $\nabla$spinor $\psi$scalar field $H$
Lagrangian:scalar curvature densityfield strength squaredDirac operator component densityfield strength squared + potential density
$L =$$R(e) vol(e) +$$\langle F_\nabla \wedge \star_e F_\nabla\rangle +$$(\psi , D_{(e,\nabla)} \psi) vol(e) +$$\nabla \bar H \wedge \star_e \nabla H + \left(\lambda {\vert H\vert}^4 - \mu^2 {\vert H\vert}^2 \right) vol(e)$

## References

### General

The original articles explaining what is now called the Higgs mechanism by spontaneous symmetry breaking were

• P. Anderson, Plasmons, gauge invariance and mass, Physical Review 130: 439. (1963)

• François Englert, Robert Brout, Broken Symmetry and the Mass of Gauge Vector Mesons, Physical Review Letters 13 (9): 321–23. (1964)

• Gerald Guralnik, C. R. Hagen, ; T. W. B. Kibble, Global Conservation Laws and Massless Particles Physical Review (1964)

• Peter Higgs, Broken Symmetries and the Masses of Gauge Bosons, Physical Review Letters 13 (16): 508–509. (1964)

While all these articles essentially describe the Higgs mechanism, apparently only the one by Peter Higgs explicitly points out that this mechanism predicts the existence of a new, then unobserved, boson, the one therefore now called the Higgs boson.

Review includes

• Sally Dawson, Christoph Englert, Tilman Plehn, Higgs Physics: It ain’t over till it’s over, Physics Reports (arXiv:1808.01324)

The general theory of spontaneous symmetry breaking is reviewed in

• Jeremy Bernstein, Spontaneous symmetry breaking, gauge theories, the Higgs mechanism and all that, Rev. Mod. Phys. 46, 7–48 (1974) (pdf)

The phenomenology of Higgs models is discussed in

• Marcela Carena, Howard E. Haber, Higgs Boson Theory and Phenomenology, Prog.Part.Nucl.Phys.50:63-152,2003 (arXiv:hep-ph/0208209)

### Detection

Early discussion of the detection of a Higgs field of 125 GeV at LHC is in

• Philip Gibbs, Seminar Watch (Higgs Special), Rumoured Higgs at 125 GeV and What Would a Higgs at 125 GeV Tell Us?, Prespacetime Journal, December 2011, Vol. 2 Issue 12 pp. 1899-1905 (web)

• Martin Holthausen, Kher Sham Lim, Manfred Lindner, Planck Scale Boundary Conditions and the Higgs Mass, JHEP 1202 (2012) 037 (arXiv:1112.2415)

The official announcement of the detection at LHC is due to

• G. Aad et al. (ATLAS Collaboration), Observation of a New Particle in the Search for the Standard Model Higgs Boson with the ATLAS Detector at the LHC, Phys. Lett. B 716, 1 (2012) (arXiv:1207.7214)

• S. Chatrchyan et al. (CMS Collaboration), Observation of a New Boson at a Mass of 125 GeV with the CMS Experiment at the LHC, 716, 30 (2012) (arXiv:1207.7235)

• G. Aad et al. (ATLAS Collaboration, CMS Collaboration), Combined Measurement of the Higgs Boson Mass in $p p$ Collisions at $\sqrt{s} = 7$ and 8 TeV with the ATLAS and CMS Experiments, Phys. Rev. Lett. 114, 191803 (2015) (arXiv:1503.07589)

### Vacuum (in-)stability

Before experimental observation of the Higgs mass at the LHC, the three possible outcomes for vacuum stability were analyzed in

More discussion of the near-criticality of the vacuum stability after the observation of the Higgs mass is due to

with a more precise analysis due to

Careful discussion of the stability issue under renormalization is in

• Anders Andreassen, William Frost, Matthew D. Schwartz, Consistent Use of the Standard Model Effective Potential, Phys. Rev. Lett. 113, 241801 (2014) (arXiv:1408.0292)

and with emphasis on non-perturbative effects in quantum tunneling/vacuum decay

• Anders Andreassen, David Farhi, William Frost, Matthew D. Schwartz, Precision decay rate calculations in quantum field theory, Phys. Rev. D 95, 085011 (2017) (arXiv:1604.06090)

Review includes

• Alexander Kusenko, Are We on the Brink of the Higgs Abyss?, Physics 8, 108 (2015)

• Sebastian Baum, On the metastability of the Standard Model, 2015 (pdf)

• Holger Gies, Vacuum stability and the mass of the Higgs boson, 2015 (pdf)

• Matthew Schwartz, Do we know if our universe is stable?, Rutgers Seminar 2015 (pdf)

• Alessandro Strumia, Higgs and Vacuum (In)Stability, talk at GGI 2017 (pdf)

• Anders Andreassen, William Frost, Matthew D. Schwartz, Scale Invariant Instantons and the Complete Lifetime of the Standard Model, Phys. Rev. D 97, 056006 (2018) (arXiv:1707.08124)

Speculation about what this near-criticality of the Higgs vacuum could be pointing to:

attractor mechanism in a landscape of vacua:

an supersymmetric-extension of the standard model of particle physics (e.g. MSSM, G2-MSSM, …)

• Gino Isidori, Andrea Pattori, On the tuning in the $(m_h, m_t)$ plane: Standard Model criticality vs. High-scale SUSY, Physics Letters B Volume 782, 10 July 2018, Pages 551-558 (arXiv:1710.11060)

as well as Kane 18, “Clue 4”.

Arguments that a false Higgs vacuum is incompatible with cosmological evolution (inflation) include the following:

• J.R. Espinosa, Gian Giudice, A. Riotto, Cosmological implications of the Higgs mass measurement, JCAP 0805:002, 2008 (arXiv:0710.2484)

• Anson Hook, John Kearney, Bibhushan Shakya, Kathryn M. Zurek, Probable or Improbable Universe? Correlating Electroweak Vacuum Instability with the Scale of Inflation, J. High Energ. Phys. (2015) 2015: 61 (arXiv:1404.5953)

• Jose R. Espinosa, Gian Giudice, Enrico Morgante, Antonio Riotto, Leonardo Senatore, Alessandro Strumia, Nikolaos Tetradis, The cosmological Higgstory of the vacuum instability (arXiv:1505.04825)

• William E. East, John Kearney, Bibhushan Shakya, Hojin Yoo, Kathryn M. Zurek, Spacetime Dynamics of a Higgs Vacuum Instability During Inflation, Phys. Rev. D 95, 023526 (2017) (arXiv:1607.00381)

The interpretation in terms of asymptotic safety is discussed in

• M. Shaposhnikov and C. Wetterich, Asymptotic safety of gravity and the Higgs boson mass, Phys. Lett. B 683 (2010) 196 (arXiv:0912.0208)

### In string theory

Discussion of the Higgs field from intersecting D-brane models is due to

Discussion of the Higgs mechanism in the G2-MSSM and related models is due to

• Gordon Kane, String theory and generic predictions for our world – superpartner masses, LHC signatures, dark matter, EWSB, cosmological history of universe, etc, talk at String phenomenology 2011, August 2011 (pdf)

• Gordon Kane, Piyush Kumar, Ran Lu, Bob Zheng, Higgs Mass Prediction for Realistic String/M Theory Vacua, Phys. Rev. D 85, 075026 (arXiv:1112.1059)

(a useful informed comment is here)

and related to the issue of the vacuum stability in

which is based on

Last revised on March 20, 2019 at 02:58:05. See the history of this page for a list of all contributions to it.