REVIEW
On the scaling behavior of the cosmological constant and the possible existence of new forces and new light degrees of freedom
High Energy Physics - Phenomenology · Submitted 25 Oct 1999 · 24 references
Pith's verdict: The one-loop cancellation in Eq. (9) is real and worth knowing; the light-scalar fix for the sign is where the paper is soft, and the stress-test's threshold objection lands.
T0 · AI review
Why Pith says this
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Referee report
The paper
The paper claims
The observed cosmological constant may be the residue of Standard Model running between the lightest neutrino masses, with a wrong sign that hints at a new light scalar.
The reading
What carries the argument
The load-bearing object is the one-loop renormalization group equation for the physical cosmological constant in the far infrared, $(4π)^2 dΛ_{ph}/dt = 12 m_S^4 - 4Σ_i m_{ν_i}^4$, together with the cancellation that makes it small: because the induced term is $Λ_{ind} = -m^4/2λ$, its $\beta$ function built from the Standard Model equations for $m^2$ and $λ$ reproduces, at leading order, exactly the negative of the neutrino vacuum-bubble contribution. What survives is a fourth-power mass sum, so the size of the generated constant is set by the fourth powers of the lightest masses rather than by the electroweak scale. The second piece of machinery is the Cosmon: a non-linearly realized dilaton $S$ entering as $e^{S/M}$ multipliers, whose mass $m_S^2 = Λ_{QCD}^4/M^2$ comes from the QCD trace anomaly and the scale $M$ of dilatation breaking, giving $m_S ∼ 10^{-3}$ eV and a Compton wavelength of a fraction of a millimetre for $M ∼ 10^{10}$ GeV.
Extended reading notes
Core claim
The paper establishes that the fine-tuned cancellation between the Higgs-induced vacuum energy and the bare vacuum term is not stable under renormalization group flow, but that the breakdown is far gentler than one might fear. Working below the electron mass, where only neutrinos remain active, the authors show that the leading $m^4 h_j^2/λ$ contributions to the running of the induced term cancel against the corresponding vacuum-bubble contributions, leaving $dΛ_{ind}/dt = -(2/(4π)^2)Σ_j m_j^4$ and hence $(4π)^2 dΛ_{ph}/dt = -4Σ_j m_j^4$. Integrating this across the mass splittings of a double-hierarchy neutrino spectrum with $m_{ν_e} ≃ m_{ν_s} ≪ m_{ν_μ} ≃ m_{ν_τ}$ yields $|Λ_{ph}|$ in the range singled out by the supernovae and CMB data, roughly $(2 ± 1) × 10^{-47}$ GeV$^4$. The prediction's sign, however, is negative, so the authors add a light real scalar whose positive contribution $12 m_S^4$ to the $\beta$ function outweighs the neutrino term when $m_S ≳ 4 m_ν$, and they argue that a pseudo-Goldstone boson of spontaneously broken dilatation symmetry naturally has both the required mass and an almost decoupled phenomenology.
Load-bearing premise
The whole construction starts from the premise that the physical cosmological constant is exactly zero at some very far infrared scale, a fine-tuned boundary condition the paper explicitly declines to derive and instead takes as natural because the measured value is so small.
Editorial extensions
If this is right
- The magnitude of the cosmological constant becomes a function of neutrino masses, so a measured absolute neutrino mass scale would translate directly into a predicted vacuum energy density.
- A new scalar of mass a few times $10^{-3}$ eV should exist, producing a Yukawa-like force of roughly gravitational strength with a range of order $0.02$ to $0.2$ mm.
- Because the coupling is to the anomalous trace of the energy-momentum tensor rather than the full trace, the new force carries composition-dependent baryon-number and isospin components in addition to the dominant mass-dependent term.
- The intermediate scale $M ∼ 10^{10}$ GeV required for the Cosmon mass coincides with the scale needed for right-handed Majorana neutrino masses, so the breaking of dilatation symmetry could be the origin of the see-saw scale.
- The renormalization group flow is driven toward $Λ_{ph} = 0$ in the far infrared when the beta function is positive, which the authors suggest could explain the approach to vanishing vacuum energy.
Reading between the lines
- If the running between neutrino thresholds really sets the observed vacuum energy, then the cosmological constant is not a constant at all but a quantity that redshifted during cosmic history, which would leave a mild imprint on the expansion history at epochs between neutrino decoupling and today.
- The required near-equality $m_S ≳ 4 m_ν$ between a new scalar and the lightest neutrino is unexplained in the paper; a natural reading is that both masses descend from the same intermediate scale $M$, which would make the submillimetre force range and the neutrino mass hierarchy two faces of one parameter.
- Short-range gravity experiments that improve sensitivity at $0.02$ to $0.2$ mm with composition-differing test masses are the cheapest route to confirm or exclude the proposal, since the predicted coupling strength of about $1/3$ of gravity is well inside existing torsion-balance reach.
- The same machinery applied at the Fermi scale would generate a far larger contribution once the top quark and weak bosons become active, so the paper's own logic implies that the cancellation must be re-established at each threshold, a requirement the authors defer to future work.
Original abstract
A large value of the cosmological constant (CC) is induced in the Standard Model (SM) of Elementary Particle Physics because of Spontaneous Symmetry Breaking. To provide a small value of the observable CC one has to introduce the vacuum term which cancels the induced one at some point in the very far infrared cosmic scale. Starting from this point we investigate whether the cancellation is preserved at different energy scales. We find that the running of the Higgs mass, couplings and the vacuum term inevitably result in a scaling dependence of the observable CC value. As a consequence one meets a nonzero CC at an energy scale comparable to the typical electron neutrino mass suggested by some experiments, and the order of magnitude of this constant is roughly the one derived from recent supernovae observations. However the sign of it is negative -- opposite to what is suggested by these observations. This discrepancy may be a hint of the existence of an extra very light scalar, perhaps a Cosmon-like dilaton, which should essentially decouple from the SM Lagrangian, but that it nevertheless could mediate new macroscopic forces in the submillimeter range.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
A large value of the cosmological constant (CC) is induced in the Standard Model (SM) of Elementary Particle Physics because of Spontaneous Symmetry Breaking. To provide a small value of the observable CC one has to introduce the vacuum term which cancels the induced one at some point in the very far infrared cosmic scale. Starting from this point we investigate whether the cancellation is preserved at different energy scales. We find that the running of the Higgs mass, couplings and the vacuum term inevitably result in a scaling dependence of the observable CC value. As a consequence one meets a nonzero CC at an energy scale comparable to the typical electron neutrino mass suggested by some experiments, and the order of magnitude of this constant is roughly the one derived from recent supernovae observations. However the sign of it is negative -- opposite to what is suggested by these observations. This discrepancy may be a hint of the existence of an extra very light scalar, perhaps a Cosmon-like dilaton, which should essentially decouple from the SM Lagrangian, but that it nevertheless could mediate new macroscopic forces in the submillimeter range.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A large value of the cosmological constant (CC) is induced in the Standard Model (SM) of Elementary Particle Physics because of Spontaneous Symmetry Breaking. | background 1.00 | 0.08 | 0.03 | asserted 1.00 |
| s1 | To provide a small value of the observable CC one has to introduce the vacuum term which cancels the induced one at some point in the very far infrared cosmic scale. | background 0.93 | 0.11 | 0.04 | asserted 0.98 |
| s2 | Starting from this point we investigate whether the cancellation is preserved at different energy scales. | contribution 0.85 | 0.40 | 0.02 | unclear 0.55 |
| s3 | We find that the running of the Higgs mass, couplings and the vacuum term inevitably result in a scaling dependence of the observable CC value. | result 1.00 | 0.94 | 0.28 | asserted 1.00 |
| s4 | As a consequence one meets a nonzero CC at an energy scale comparable to the typical electron neutrino mass suggested by some experiments, and the order of magnitude of this constant is roughly the one derived from recent supernovae observations. | result 0.99 | 0.82 | 0.22 | asserted 0.86 |
| s5 | However the sign of it is negative -- opposite to what is suggested by these observations. | result 0.95 | 0.83 | 0.14 | asserted 1.00 |
| s6 | This discrepancy may be a hint of the existence of an extra very light scalar, perhaps a Cosmon-like dilaton, which should essentially decouple from the SM Lagrangian, but that it nevertheless could mediate new macroscopic forces in the submillimeter range. | interpretation 1.00 | 0.35 | 0.69 | hedged possibility 1.00 |
What was examined, and what was not
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References
How the literature uses it
32 arXiv papers cite this in 62 sentences
Papers citing it · 43 sentences without a confident label
Contests it 1 paper
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The corresponding authors claim that in the work on the RGE running of the CC [ref] part of the one-loop corrections to the CC have been missed out, namely the explicit $μ$ dependent part of the full one-loop effective action.
Relaxing neutrino mass bounds by a running cosmological constant · Conclusions and Outlook · contest 0.82
Cites it as support 1 paper
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This interaction between the KR axion and gravitational Chern-Simons terms proves essential in leading [ref] to a cosmological vacuum of the RVM type [ref] , which in turn implies an early inflationary era, without inflaton fields [ref] .
Torsion in string-inspired cosmologies and the universe dark sector · Introduction: A case for going beyond GR and Riemannian Geometry · 0.99
Cites it as background 16 papers
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We mention at this point that one such theoretical framework is the so-called “running vacuum model (RVM)” framework [ref] (where a time dependent vacuum energy is assumed, but with equation of state $w_vacuum = -1$ as in the de Sitter case).
Torsion in string-inspired cosmologies and the universe dark sector · Introduction: A case for going beyond GR and Riemannian Geometry · 0.80
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The RVM cosmology [ref] is an effective cosmological framework, with a cosmic-time-varying dark energy $Λ(t)$, which, nonetheless, is still characterised by an equation of state of de Sitter type: [equation] where $p$ ($ρ$) denotes the vacuum pressure (energy) density.
Lorentz Symmetry Violation in String-Inspired Effective Modified Gravity Theories · Condensates and Running-Vacuum-Model inflation · 0.93
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The fast and fruitful theoretical developments undergone by the RVM framework over time can easily be traced in the literature by considering the derivation of its basic equations for the vacuum energy density (VED), originally guessed from old semiqualitative arguments based on the renormalization group (RG) approach to cosmology – see [ref] and references therein – until reaching its mature status at present through explicit renormalization calculations within QFT in curved spacetime [ref] .
Running Vacuum in the expanding Universe: a unified QFT paradigm for Inflation and Dark Energy · Discussion and outlook · 0.88
Discussion
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