REVIEW
Domain walls, near-BPS bubbles, and probabilities in the landscape
High Energy Physics - Theory · Submitted 29 May 2006 · 71 references
Pith's verdict: Section 2's multi-moduli BPS machinery and the e^{-S0/2} Minkowski decay rate are solid and will be cited; the dramatic AdS decay rate rests on an unquantified assumption about the wall tension, and Eq. 5.19 has an algebra slip.
T0 · AI review
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Referee report
The paper
The paper claims
Static supersymmetric walls between string vacua, once uplifted to de Sitter, become near-critical bubble walls whose one-way decay channels act as sinks and can invert the usual landscape probability distribution.
The reading
What carries the argument
The load-bearing device is the pair of first-order BPS flow equations for a flat domain wall in $d=4$, $N=1$ supergravity with arbitrary Kähler potential and any number of moduli: $a'/a = ±|Z|$ and $z^{i}{}' = ∓2 g^{i j̄} ∂_{j̄}|Z|$, where $Z = e^{K/2}W$ is the covariantly holomorphic superpotential. Rewriting the supergravity action plus Gibbons–Hawking boundary terms as a sum of squares of these equations turns the on-shell action into a boundary term, which yields the wall tension directly and reproduces the known critical and super-critical tensions without a Nester construction. The second device is the near-BPS expansion: in the Parke thin-wall formulas, written in the variables $x = (ρ_0/2Λ)^2$ and $y = Λ_2/λ^2$, the BPS limit sits at the singular point $x=1$, $y=-1$ where the bubble radius and the tunneling exponent diverge, and expanding about that point in the small uplifting $V_0$ produces both the universal $S_0/2$ result and the gravitino-mass expression. The third device is the replacement of detailed balance by current equations $ḢP_0 = -J_{0s} - J_{01} + J_{10}$ and $ḢP_1 = -J_{1s} - J_{10} + J_{01}$, whose stationary ratio $p = P_1/P_0$ is set by whichever of the sink rate and the upward rate is larger.
Extended reading notes
Core claim
The central claim is that near-BPS reasoning fixes the decay rate of uplifted de Sitter vacua, and that the resulting rates are large enough to restructure landscape probabilities. For a de Sitter vacuum obtained by uplifting a supersymmetric Minkowski minimum, the paper finds a model-independent tunneling exponent $B = 12π^2/V_0 = S_0/2$, i.e. half the de Sitter entropy, so the decay time is shorter than the recurrence time $t_r ∼ e^{S_0}$ by a factor $e^{S_0/2}$ — for our vacuum, roughly $e^{10^{120}/2}$. For a de Sitter vacuum obtained by uplifting a supersymmetric AdS minimum of depth $|V_0|$, the exponent is instead of order $8π^2/m_{3/2}^2$ times an $O(1)$ factor built from the ratio $C^2 = |V_1|/|V_0|$, tying the decay rate to the gravitino mass rather than to the cosmological constant; since $|V_0|$ before uplifting can exceed the present vacuum energy by a hundred orders of magnitude, this rate can far exceed $e^{-S_0}$. Because a piece of space that tunnels to a collapsing AdS region or to Minkowski never returns, these channels are sinks, and solving the resulting current equations rather than the detailed-balance equation gives, in the wide-sink regime, an inverted distribution $P_1/P_0 = e^{S_1 - |S(φ)| - C_0} ≫ 1$: most of the de Sitter comoving volume sits in the higher-energy vacuum, and the upward current is suppressed relative to the sink current by $e^{-S_0}$.
Load-bearing premise
The claim that uplifted AdS vacua decay quickly rests on the expectation that uplifting lowers the bubble wall tension; if the tension stays at or above its supersymmetric value, the gravitational suppression factor $(1 - 9σ^4/(16|V_1|^2))^{-1}$ diverges or turns negative and tunneling is forbidden, and the paper supports the expectation with only one numerical check in the KL model. The universal Minkowski result $B = S_0/2$ does not need this premise, but the gravitino-mass result does.
Editorial extensions
If this is right
- The decay rate of an uplifted Minkowski vacuum is fixed at $e^{-S_0/2}$ independent of wall tension and of the depth of the AdS minimum, so it is a universal prediction of KKLT-type uplifting rather than a model-by-model number.
- For uplifted AdS vacua the rate scales as $\exp(-O(m_{3/2}^{-2}))$, which for a gravitino mass above roughly $10^2$ GeV exceeds $e^{-S_0} \sim e^{-10^{120}}$ by an enormous factor, making such vacua short-lived on cosmological timescales.
- Because the decay channels to collapsing space and to Minkowski are irreversible, the comoving volume in de Sitter vacua decreases in time as $\exp(-e^{-C_0}t/(1+p))$, so no true stationary distribution exists in the landscape.
- In the wide-sink regime the standard Hartle–Hawking weighting $P \propto e^{24π^2/V}$ is replaced by an inverted distribution peaked at larger vacuum energy, and the upward current ratio $J_{01}/J_{0s}$ becomes of order $e^{-S_0}$.
- The lifetime bound that our own vacuum has survived longer than its age becomes a selection rule on the depth of the pre-uplifting AdS minimum and hence on the gravitino mass.
Reading between the lines
- The universal $S_0/2$ exponent suggests a general principle worth stating separately: whenever a de Sitter vacuum is produced by a small explicit breaking of a supersymmetric pair of vacua, the tunneling exponent is half the entropy rather than the full entropy, because the near-BPS wall supplies one of the two factors of the CDL suppression. It would be worth checking whether the same halving app
- The sink argument implicitly assumes that a bubble interior, once collapsed, is removed from the probability accounting rather than recycled through a quantum jump back to de Sitter; the paper notes this option in a footnote and sets it aside. A reader could test how sensitive the inverted distribution is to allowing even a strongly suppressed return channel.
- Because the AdS decay rate tracks $m_{3/2}$, the sink mechanism converts a cosmological-constant question into a supersymmetry-breaking question. That suggests an observable-side consequence: if the landscape picture is right, the gravitino mass and the depth of the pre-uplifting AdS minimum are not independent parameters but are linked by the requirement that our vacuum has not already drained.
- The paper keeps fluxes fixed across every wall it constructs, and says so explicitly in the introduction and discussion. Extending the sink analysis to transitions that change flux would be the natural next step, since those transitions are the ones that connect different area codes rather than different points within one.
Original abstract
We develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. After the uplifting, some of the vacua become dS, whereas some others remain AdS. The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. The channels of irreversible vacuum decay serve as sinks for the probability flow. The existence of such sinks is a distinguishing feature of the landscape. We show that it strongly affects the probability distributions in string cosmology.
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 develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. After the uplifting, some of the vacua become dS, whereas some others remain AdS. The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. The channels of irreversible vacuum decay serve as sinks for the probability flow. The existence of such sinks is a distinguishing feature of the landscape. We show that it strongly affects the probability distributions in string cosmology.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. | contribution 1.00 | 0.96 | 0.11 | asserted 1.00 |
| s1 | Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. | contribution 0.88 | 0.21 | 0.03 | asserted 0.99 |
| s2 | After the uplifting, some of the vacua become dS, whereas some others remain AdS. | background 0.77 | 0.20 | 0.03 | asserted 0.94 |
| s3 | The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. | interpretation 0.97 | 0.26 | 0.08 | hedged possibility 1.00 |
| s4 | As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. | result 1.00 | 0.95 | 0.42 | asserted 0.86 |
| s5 | The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. | result 0.77 | 0.60 | 0.14 | asserted 1.00 |
| s6 | The channels of irreversible vacuum decay serve as sinks for the probability flow. | interpretation 0.94 | 0.51 | 0.18 | asserted 1.00 |
| s7 | The existence of such sinks is a distinguishing feature of the landscape. | interpretation 0.93 | 0.41 | 0.17 | asserted 1.00 |
| s8 | We show that it strongly affects the probability distributions in string cosmology. | result 0.56 | 0.90 | 0.36 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v5
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- figures and tables
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- P abstract
- S sections
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- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-th/0605266 by the authors.
References
How the literature uses it
34 arXiv papers cite this in 102 sentences
Papers citing it · 70 sentences without a confident label
Builds on it 2 papers
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Thus, our results generalize the class of the BPS domain walls of four-dimensional $𝒩=1$ supergravities studied previously e.g. in [ref] .
Three-forms, dualities and membranes in four-dimensional supergravity · Conclusions · 0.97
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Finally, an interesting development would be to employ this new three-form multiplet as part of low energy effective theories coming from flux compactifications of string theory, extending earlier works [ref] , and in particular to study the compatibility with [ref] and the relation to [ref] .
Three-forms and Fayet-Iliopoulos terms in Supergravity: Scanning Planck mass and BPS domain walls · Discussion · 0.83
Uses its method or tool 7 papers
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To compute the full tension, including the effect of the closed string moduli, we use the an approximation similar to that of [ref] as described in section [ref].
Evidence for a bound on the lifetime of de Sitter space · Corrections to the tension · 1.00
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Around a straight enough membrane, one can assume such flow to be governed by the BPS flow equations discussed in [ref] .
Swampland Conjectures for Strings and Membranes · Membranes · 0.91
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With its help the flow equations take the form Ȧ=- , ϕ̇^i = 2 g^i ∂_ , whereas the equation for $ϑ$ in [ref] is automatically satisfied, cf. [ref] .
Domain walls from ten dimensions · Ten–dimensional flow from four–dimensional effective theory · 0.85
Compares with it 3 papers
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As compared to the tension obtained purely in supergravity [ref] , [ref] additionally contains the explicit contribution from the branes [ref].
Domain walls from ten dimensions · The D–brane modified c-theorem · 0.80
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The path we found numerically is a spatial planar interpolation between two vacua that minimizes the action integral, [equation] Dropping the (2+1) planar integral, we get the tension of this transition domain wall, [equation] Comparing to the similar problem in supergravity [ref] , we dropped the Kahler sector and 4D gravity.
Conifolds and Tunneling in the String Landscape · The BPS Path · 0.96
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This reduced action is identical in form to the one obtained in [ref] in the absence of membranes, basically because of the observed reciprocal cancellations of various terms localised on the membrane.
Three-forms, dualities and membranes in four-dimensional supergravity · BPS action and domain wall tension · 0.90
Cites it as support 1 paper
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An investigation of the rates of tunneling in the landscape performed in [ref] suggests that this condition most probably is met for many of such vacua.
Stationary Measure in the Multiverse · No Boltzmann brains · 0.97
Cites it as background 8 papers
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The decay to AdS space (or, more accurately, a decay to a collapsing open universe with a negative cosmological constant) was studied in Ref. [ref] .
Boltzmann brains and the scale-factor cutoff measure of the multiverse · Vacuum Decay Rates · 0.88
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This has been extensively studied in the literature starting in [ref] (see also a more recent discussion about this topic in [ref] and references therein).
Brane Nucleation in Supersymmetric Models · Flat membrane solutions in supergravity models · 0.85
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The main application of the logical independence of the probability rules is to the measure problem in cosmology [ref] , the problem of how to make statistical predictions for observations in a universe that may be so large that almost all theoretically possible observations actually occur somewhere.
The Born Rule Dies · Introduction · 0.87
Discussion
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