REVIEW
Gauged supergravity from type IIB string theory on Y^{p,q} manifolds
High Energy Physics - Theory · Submitted 1 Aug 2006 · 40 references
Pith's verdict: A genuinely useful KK ansatz for IIB on Y^{p,q}, plus a clean η/s computation whose charge-independence is real but narrower than the word 'universal' suggests.
T0 · AI review
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Referee report
The paper
The paper claims
The paper argues that the shear-viscosity-to-entropy ratio of a strongly coupled plasma stays at $1/4π$ even when a conserved R-charge chemical potential is turned on, and shows this for the infinite family of quiver gauge theories dual to黑
The reading
What carries the argument
Two pieces carry the argument. The first is the Kaluza-Klein ansatz that writes the ten-dimensional metric as a five-dimensional metric plus the Sasaki-Einstein metric on $Y^{p,q}$ with the Reeb fiber promoted to $dψ + A + A_μ dx^μ$, together with $F_{(5)} = (1+*)G_{(5)}$ with $G_{(5)} = 4gε_{(5)} - (1/3)g^2 J_{(2)} ∧ *_5 F_{(2)}$. This ansatz is asserted to be consistent at the nonlinear level: the ten-dimensional Bianchi identity and Einstein equations reduce exactly to the five-dimensional Maxwell-Chern-Simons and Einstein equations of minimal gauged supergravity. The second is the fluctuation analysis: the transverse-traceless metric perturbation $φ = c_2^{-2} δg_{12}/2$ obeys a minimally coupled scalar equation in the charged black hole background, and after a change of radial variable to $x = c_1/c_2$ the incoming-wave solution is expanded as $φ_ω = x^{-iw}(F_0 + iw F_ω + …)$ with $w = ω/(2πT)$. The charge dependence cancels in the boundary limit of the kernel, which is what produces the charge-independent $η/s$.
Extended reading notes
Core claim
The central claim is that the ratio of shear viscosity to entropy density in the strongly coupled $SCFT_{p,q}$ plasma dual to an R-charged black hole of five-dimensional minimal $N=2$ gauged supergravity is $η/s = 1/(4π)$, independent of the $U(1)_R$ chemical potential. The computation proceeds by perturbing the charged black hole metric in the $g_{12}$ direction, reducing the quadratic fluctuation action to that of a minimally coupled scalar, and solving the resulting radial equation in a low-frequency expansion about the horizon. The charge $Q$ enters the fluctuation equation in a complicated way, so universality is not automatic; the authors show that the function controlling the boundary kernel obeys a first-order equation with an explicit solution, and that its boundary limit reproduces $-iωs/(8π)$ with $s$ the Bekenstein-Hawking entropy density. Combined with the Kubo formula this gives the quoted ratio. They also note that the speed of sound in this plasma is $c_s^2 = 1/3$, again independent of chemical potential, because the pressure is one third of the energy density.
Load-bearing premise
The load-bearing premise is that the nonlinear Kaluza-Klein ansatz keeping only the metric and five-form is a genuinely consistent truncation of type IIB on $Y^{p,q}$, so that discarding the $SU(2) × U(1)$ vector multiplets present in the massless sector does not secretly source the Kaluza-Klein tower; the paper asserts this consistency and checks that the ten-dimensional equations reduce to the five-dimensional ones, but the argument that the vectors cannot be kept is carried over from a $T^{1,1}$ result.
Editorial extensions
If this is right
- The ratio $η/s = 1/(4π)$ holds for the entire infinite family of $N=1$ superconformal quiver gauge theories $SCFT_{p,q}$ at finite temperature and finite R-charge chemical potential, not only for $N=4$ Yang-Mills with R-charges.
- The R-charged black hole solutions of five-dimensional gauged supergravity lift to explicit ten-dimensional type IIB backgrounds on $Y^{p,q}$, so their thermodynamics and hydrodynamics have a genuine string-theory interpretation.
- The speed of sound in these plasmas is $c_s^2 = 1/3$ at any chemical potential, since the pressure equals one third of the energy density, so the near-conformal bulk-viscosity relation is not disturbed by the charge.
- Because the reduction to minimal $N=2$ gauged supergravity is the only consistent truncation on $Y^{p,q}$, the $N=2$ STU model with three independent R-charges cannot be realized from these manifolds, even though a linearized Kaluza-Klein analysis might suggest otherwise.
Reading between the lines
- If $η/s$ is unchanged by an R-charge chemical potential in both orbifold quivers and the $T^{1,1}$ quiver, it is tempting to read the result as saying the ratio is constant along the renormalization-group flow that connects the $Z_2$ orbifold of $N=4$ Yang-Mills in the ultraviolet to the $T^{1,1}$ fixed point in the infrared.
- The authors' own conjecture points at a sharper test: a plasma with a chemical potential but $c_s^2 \neq 1/3$, such as a cascading gauge theory, would separate the universal shear-viscosity statement from the conformal symmetry that makes the present computation tractable.
- The cancellation of $Q$ in the low-frequency kernel is reminiscent of a horizon-attached quantity, which suggests the ratio could be derivable from the near-horizon geometry alone rather than from the full radial solution.
- Because the truncation drops the $SU(2) \times U(1)$ vector multiplets, a natural follow-up is to ask whether the same $η/s$ persists in a consistent truncation that retains some of them, for example through a different internal manifold where such a truncation is known to exist.
Original abstract
We first construct a consistent Kaluza-Klein reduction ansatz for type IIB theory compactified on Sasaki-Einstein manifolds Y^{p,q} with Freund-Rubin 5-form flux giving rise to minimal N=2 gauged supergravity in five dimensions. We then investigate the R-charged black hole solution in this gauged supergravity, and in particular study its thermodynamics. Based on the gauge theory/string theory correspondence, this non-extremal geometry is dual to finite temperature strongly coupled four-dimensional conformal gauge theory plasma with a U(1)_R-symmetry charge chemical potential. We study transport properties of the gauge theory plasma and show that the ratio of shear viscosity to entropy density in this plasma is universal. We further conjecture that the universality of shear viscosity of strongly coupled gauge theory plasma extends to nonzero R-charge chemical potential.
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 first construct a consistent Kaluza-Klein reduction ansatz for type IIB theory compactified on Sasaki-Einstein manifolds Y^{p,q} with Freund-Rubin 5-form flux giving rise to minimal N=2 gauged supergravity in five dimensions. We then investigate the R-charged black hole solution in this gauged supergravity, and in particular study its thermodynamics. Based on the gauge theory/string theory correspondence, this non-extremal geometry is dual to finite temperature strongly coupled four-dimensional conformal gauge theory plasma with a U(1)_R-symmetry charge chemical potential. We study transport properties of the gauge theory plasma and show that the ratio of shear viscosity to entropy density in this plasma is universal. We further conjecture that the universality of shear viscosity of strongly coupled gauge theory plasma extends to nonzero R-charge chemical potential.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We first construct a consistent Kaluza-Klein reduction ansatz for type IIB theory compactified on Sasaki-Einstein manifolds Y^{p,q} with Freund-Rubin 5-form flux giving rise to minimal N=2 gauged supergravity in five dimensions. | contribution 0.76 | 0.94 | 0.08 | asserted 1.00 |
| s1 | We then investigate the R-charged black hole solution in this gauged supergravity, and in particular study its thermodynamics. | contribution 0.99 | 0.92 | 0.05 | asserted 0.80 |
| s2 | Based on the gauge theory/string theory correspondence, this non-extremal geometry is dual to finite temperature strongly coupled four-dimensional conformal gauge theory plasma with a U(1)_R-symmetry charge chemical potential. | interpretation 0.98 | 0.29 | 0.11 | asserted 0.99 |
| s3 | We study transport properties of the gauge theory plasma and show that the ratio of shear viscosity to entropy density in this plasma is universal. | result 0.97 | 0.93 | 0.44 | asserted 1.00 |
| s4 | We further conjecture that the universality of shear viscosity of strongly coupled gauge theory plasma extends to nonzero R-charge chemical potential. | future work 0.62 | 0.28 | 0.31 | speculative 1.00 |
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References
How later papers used it
59 later papers cite it
1 later paper by other authors is listed below: 1 built on it and 1 compared its own results with it. It appears under more than one label.
Builds on it 1 of 6 papers with this label
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Showed that this paper's consistent Kaluza-Klein reduction to minimal D=5 N=2 gauged supergravity can also be extended to include the massive supermultiplet containing the breathing mode.
Universal Kaluza-Klein reductions of type IIB to N=4 supergravity in five dimensions (2010) · 0.98 · paraphrased: the licence does not allow quoting
Compares with it 1 of 2 papers with this label
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Compared its own equations of motion, which reduce to equations (2.15) and (2.16) of this paper with F_2^here = (1/3)F_2^there.
Universal Kaluza-Klein reductions of type IIB to N=4 supergravity in five dimensions (2010) · 0.99 · paraphrased: the licence does not allow quoting
How the literature uses it
60 arXiv papers cite this in 92 sentences
Papers citing it · 69 sentences without a confident label
Builds on it 6 papers
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We will show that the consistent KK reduction to minimal $D=5$ $N=2$ gauged supergravity of [ref] can also be extended to include the massive supermultiplet containing the breathing mode.
Universal Kaluza-Klein reductions of type IIB to N=4 supergravity in five dimensions · Introduction · 0.98
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These are the sources for the naked singularity existing in the supergravity configurations carrying the same amount of mass [ref] , extending the analysis and interpretation originally done in [ref] in the context of $=4$ SYM and $AdS_5×S^5$.
Small Black holes vs horizonless solutions in AdS · Mesonic half-BPS sector in $=1$ toric gauge theories · 0.92
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Besides including the modes discussed in [ref] , our truncation incorporates in a supersymmetric way all the supergravity states dual to the universal gauge sector of the associated conformal theories.
Type IIB supergravity on squashed Sasaki-Einstein manifolds · Introduction · 0.92
Uses its method or tool 1 paper
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These solutions can be uplifted on[Using the results of [ref] we can uplift on an arbitrary five-dimensional Sasaki-Einstein space; the resulting $AdS_3$ solutions have already been presented in [ref] .] an $S^5$ to type IIB supergravity using the formulae in [ref] .
D=5 SU(2)xU(1) Gauged Supergravity from D=11 Supergravity · Uplifting the Klemm-Sabra magnetic string solution · 0.92
Compares with it 2 papers
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Repeating the same procedure as we have for the $S^5$ reduction, we find that the Killing spinor equations along the $T^1,1$ directions are solved with $λ= η_0$ being a constant spinor satisfying [equation] This is in contrast with the results of [ref] , where their Killing spinor obeys both the projection conditions above, as well as having a functional dependence on the $SU(2)$ directions given by a factor of $e^iψ/2$.
Type IIA embeddings of $D=5$ minimal gauged supergravity via Non-Abelian T-duality · $T^1,1$ truncation · 0.95
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We can recover the KK reduction to minimal $D=5$ $N=2$ gauge supergravity of [ref] (see also [ref] ) by setting $U=V=e^Z=K_1=L_2=G_i=H_i=M_a=N_a=0$ and $K_2 = - F_2$.
Universal Kaluza-Klein reductions of type IIB to N=4 supergravity in five dimensions · Minimal $N=2$ gauged supergravity in $D=5$ · 0.88
Cites it as support 2 papers
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For example, for the class of $AdS_5 ×M_5$ solutions of type IIB supergravity, where $M_5$ is a Sasaki-Einstein manifold, that are dual to $N=1$ SCFTs in $d=4$, it was shown in [ref] (see also [ref] ) that there is a consistent KK reduction of IIB supergravity on $M_5$ to minimal gauged supergravity in $D=5$.
D=5 SU(2)xU(1) Gauged Supergravity from D=11 Supergravity · Introduction · 0.97
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As shown in [ref] this class includes all such theories with a dual IIB or M-theory description, as all these theories admit a consistent truncation to $D=5$ minimal gauged supergravity.
Magnetic Brane Solutions in AdS · Discussion · 0.96
Cites it as background 10 papers
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A few years ago it was shown that the most general supersymmetric $AdS_5$ solutions of $D=11$ supergravity [ref] (of which Sasaki-Einstein $Y^p,q$ [ref] belong) permits a consistent reduction to minimal $N=2$ $D=5$ gauged supergravity [ref] .
3D gauged supergravity from wrapped M5-branes with AdS/CMT applications · Introduction · 0.85
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At the two-derivative level, the full non-linear reduction of the bosonic sector of IIB theory on SE$_5$ was carried out in [ref] .
Computing 1/N^2 corrections in AdS/CFT · Actual computation for AdS$_5×SE_5$ · 0.84
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Solutions which carry only $R$-charge have been studied in [ref] at the linearised level.
Half BPS states in AdS_5 x Y^{p,q} · Introduction · 0.82
Discussion
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