REVIEW
Saltatory Relaxation of the Cosmological Constant
High Energy Physics - Theory · Submitted 30 May 2000 · 41 references
Pith's verdict: Two genuinely new string-theoretic ingredients for Brown-Teitelboim relaxation, wrapped around a headline relation that is conditional on an assumption the authors themselves flag.
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Referee report
The paper
The paper claims
String/M-theory brane properties and coincident-brane density of states can make saltatory relaxation of the cosmological constant fast enough, and requiring stability on cosmological timescales then implies a supersymmetry breaking scale below a few TeV.
The reading
Extended reading notes
Core claim
The central load-bearing assertion is Eq. (47): requiring that the effective cosmological term be stable on cosmological timescales, rather than absolutely stable, yields the relation M_SUSY^2 less than about (10^-3 eV)(M_Planck), equivalently a supersymmetry breaking scale below a few TeV. If correct, this connects the observed cosmological constant, the Planck scale, and the scale of supersymmetry breaking in a single inequality, and it makes the saltatory relaxation mechanism testable at colliders.
Load-bearing premise
The load-bearing premise is the identification of the bare cosmological constant with the supersymmetry breaking scale, Eq. (41): lambda M^2 ~ M_SUSY^4. The authors justify it only by saying it is 'reasonable to expect' (Sec. 5.1). If the bare cosmological term is instead set by a hidden sector at a much higher scale, the stability bound B > 1 fails and the vacuum is unstable in the simplest scenario. The authors acknowledge this explicitly: 'Unless the hidden sector contribution to the bare cosmological term is somehow suppressed to this TeV scale, in our simplest scenario the vacuum will be unstable.'
Original abstract
We modify and extend an earlier proposal by Brown and Teitelboim to relax the effective cosmological term by nucleation of branes coupled to a three-index gauge potential. Microscopic considerations from string/M theory suggest two major innovations in the framework. First, the dependence of brane properties on the compactification of extra dimensions may generate a very small quantized unit for jumps in the effective cosmological term. Second, internal degrees of freedom for multiply coincident branes may enhance tunneling rates by exponentially large density of states factors. These new features essentially alter the relaxation dynamics. By requiring stability on the scale of the lifetime of the universe, rather than absolute stability, we derive a non-trivial relation between the supersymmetry breaking scale and the value of the cosmological term. It is plausibly, though not certainly, satisfied in Nature.
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
We modify and extend an earlier proposal by Brown and Teitelboim to relax the effective cosmological term by nucleation of branes coupled to a three-index gauge potential. Microscopic considerations from string/M theory suggest two major innovations in the framework. First, the dependence of brane properties on the compactification of extra dimensions may generate a very small quantized unit for jumps in the effective cosmological term. Second, internal degrees of freedom for multiply coincident branes may enhance tunneling rates by exponentially large density of states factors. These new features essentially alter the relaxation dynamics. By requiring stability on the scale of the lifetime of the universe, rather than absolute stability, we derive a non-trivial relation between the supersymmetry breaking scale and the value of the cosmological term. It is plausibly, though not certainly, satisfied in Nature.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We modify and extend an earlier proposal by Brown and Teitelboim to relax the effective cosmological term by nucleation of branes coupled to a three-index gauge potential. | contribution 0.98 | 0.88 | 0.08 | asserted 0.99 |
| s1 | Microscopic considerations from string/M theory suggest two major innovations in the framework. | contribution 0.86 | 0.18 | 0.03 | hedged possibility 0.86 |
| s2 | First, the dependence of brane properties on the compactification of extra dimensions may generate a very small quantized unit for jumps in the effective cosmological term. | contribution 0.92 | 0.21 | 0.07 | hedged possibility 1.00 |
| s3 | Second, internal degrees of freedom for multiply coincident branes may enhance tunneling rates by exponentially large density of states factors. | contribution 0.96 | 0.21 | 0.06 | hedged possibility 0.99 |
| s4 | These new features essentially alter the relaxation dynamics. | interpretation 0.88 | 0.53 | 0.09 | asserted 0.98 |
| s5 | By requiring stability on the scale of the lifetime of the universe, rather than absolute stability, we derive a non-trivial relation between the supersymmetry breaking scale and the value of the cosmological term. | result 0.92 | 0.93 | 0.62 | asserted 1.00 |
| s6 | It is plausibly, though not certainly, satisfied in Nature. | interpretation 0.84 | 0.39 | 0.11 | hedged possibility 0.99 |
What was examined, and what was not
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References
How the literature uses it
45 arXiv papers cite this in 56 sentences
Papers citing it · 32 sentences without a confident label
Contests it 1 paper
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However the analysis in [ref] does not take moduli stabilization into account and the resultant distribution of quantized fluxes does not imply the preference of a small cosmological constant.
Probability of Vacuum Stability in Type IIB Multi-K\"ahler Moduli Models · Introduction · contest 0.84
Builds on it 1 paper
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In its simplest incarnation, our approach is a generalization of the idea pioneered in [ref] about discharging cosmological constant by nonperturbative membrane nucleation processes, and also benefits from results of [ref] .
Implications of Weak Gravity Conjecture for de Sitter Decay by Flux Discharge · Introduction · 0.96
Uses its method or tool 1 paper
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This rate may be derived from a worldline formalism that has the advantage of being easily generalized to higher-dimensional objects [ref] .
De Sitter space constraints on brane tensions and couplings · Nucleation of 2-branes · 0.88
Compares with it 4 papers
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However there are important technical differences when we compare to those models since in our theory the bulk cosmological constant depends on the $4$-form dual magnetic fluxes (bi)linearly, as opposed to quadratically [ref] , as is clear from Eq. ([ref]).
Pancosmic Relativity and Nature's Hierarchies · Lg · 0.99
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This is in sharp contrast to previous works [ref] where the flux sector does not include linear $4$-form terms but starts with $F^2$.
Implications of Weak Gravity Conjecture for de Sitter Decay by Flux Discharge · Introduction · 0.98
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This picture is similar in looks to that proposed in Ref. [ref] , where a saltatory relaxation (i.e., relaxation by jumps) of the cosmological constant takes place as the universe tunnels repeatedly down the potential.
The Cosmological Constant Problem and Inflation in the String Landscape · Inflation in the landscape · 0.99
Cites it as background 17 papers
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The instanton taxonomy was proffered in [ref] for the theories with $4$-form fluxes screening the cosmological constant [ref] .
A Quantum-Mechanical Mechanism for Reducing the Cosmological Constant · Introduction · 0.97
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Their classification was initiated in [ref] for the theories with $4$-form fluxes screening the cosmological constant [ref] .
Hidden Variables of Gravity and Geometry and the Cosmological Constant Problem · Introduction · 0.89
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A complementary line of inquiry, starting with the seminal work [ref] , has been to frame the question in terms of statistical distributions in the landscape of flux vacua [ref] .
Moduli Stabilisation and the Statistics of SUSY Breaking in the Landscape · Introduction · 0.95
Discussion
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