# Tagged Questions

AdS/CFT is a special case of the holographic principle. It states that a quantum gravitating theory in Anti-de-Sitter (AdS) space is exactly equivalent to the gauge theory/Conformal Field Theory (CFT) on its boundary.

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### large N expansion vs AdS/CFT

I'm beginning to learn AdS/CFT and I have an elementary question. It is said that since it is very hard to calculate 4 point and above correlators in a strongly coupled CFT, we can use instead the ...
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### How is the two-point function of an operator dual to a scalar ADS field obtained in ADS/CFT?

The two point function of an operator dual to a scalar field in ADS/CFT can obtained directly from computation of the on-shell action in momentum space and then taking it back to position space. The ...
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How is the mass of the black hole defined in a asymptotcally AdS solution of the black hole? How can I find it? Beacause in asymptotcally flat solution I can read it from the $g_{tt}$ component of the ...
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### Correlator of energy-momentum tensor and OPE

In http://arxiv.org/abs/hep-th/9108028 Equation (2.22), the correlation function of then energy-momentum tensor with some primary fields is We can view this as sum over the OPE of the energy-...
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### Implication of non-positive tripartite information

Hayden et al 2011 showed that tripartite information is non-positive given Ryu-Takanayagi formula. (For definition of tripartite information, see for instance section 4.4 of this paper) Is there ...
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### Circular Wilson Loop in AdS/CFT

I'm trying to get the AdS solution to the circular wilson loop. The standard AdS metric is: $ds^2 = \frac{L^2}{z^2}(\eta_{\mu \nu} dx^{\mu} dx^{\nu} + dz^2)$ If I take the circle of radius R at ...
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### Are the quasinormal modes scalar quantities?

I am studying the so-called quasinormal modes (QNMs) in the context of the AdS/CFT correspondence and I got stuck. For instance, if I choose a weird patch of coordinates for the, say, AdS5-...
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### What is the origin of the five-form field in bubbling Ads geometries?

I have been reading the paper: Bubbling Ads space and the 1/2 BPS geometries[hep-th/0409174]. In the paper they look at 1/2 BPS states in the field theory which are dual to D3 branes IIB supegravity. ...
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### Collapse of two large black holes in AdS

In $4d$ flat space, two black holes of mass $M$ can collapse to form another one of (roughly) mass $2M$. This process is spontaneous, as reflected by the fact that the black hole entropy $S=M^2$ ...
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### Norm definition for arbitrary spin fields in AdS

In AdS/CFT one usually hears of normalizable and non-normalizable modes regarding the independent solutions for the different fields. I've found that the "natural" definition of the norm in the case ...
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### What is a zero temperature horizon?

While reading the paper "Disorder horizons: Holography of randomly disordered fixed points" by Hartnoll and Santos, I came across this: We are interested in solutions with a zero temperature ...
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### What is known about the physics of Planckbrane (another brane) in Randall–Sundrum model?

Randall–Sundrum model imagines that our universe is a five-dimensional anti-de Sitter space and the elementary particles except for the graviton are localized on a (3 + 1)-dimensional brane or branes. ...
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In certain limits of 2 dimensional CFT's, it is possible to compute the entropy of the theory in terms of the density of states which is given by the Cardy formula $$S = 2\pi \left(\sqrt{\frac{c_R \... 0answers 82 views ### What is a Witten diagram? Recently I heard the terminology of Witten diagram. Studying QFT, I frequently see Feynman diagrams and use them to compute scattering amplitudes, one-loop corrections and so on. In string theory ... 0answers 31 views ### What is the global Virasoro symmetry generators in BTZ spacetime? This is the case of AdS3, how about BTZ? The picture is from arxiv:1506.01353. 1answer 77 views ### CFT and temperature I have tried to think about this for some time but could not really go anywhere. Sorry for the sloppy question and thanks for any pointer. My question is about CFT at finite temperature and ... 0answers 29 views ### What does black hole temperature mean? [duplicate] From the title, the question is a bit open ended. Let me make it a bit simpler. 1. What region of the black hole has temperature? Is it the surface space? the region outside? . . . etc , any precise ... 2answers 104 views ### AdS/CFT Group Theory I have a two part question about AdS/CFT: Is the only necessary ingredient that the isometry group of AdS matches the conformal group in one dimension less or are there other prerequisites to build ... 1answer 59 views ### AdS/CFT and Kondo problem/ Ginzburg-Landau theory I was reading the review on Unconventional superconductivity by Mike Norman, towards the end (page 22) he comments two things about AdS/CMT: "In the condensed matter context in two dimensions, one ... 0answers 46 views ### Boundary condition for holographic Green's function I understand that to obtain retarded Green's function using AdS/CFT one needs to put ingoing wave boundary condition at the horizon, when one is considering a finite temperature system. For system ... 0answers 84 views ### Why is it that the conformal anomaly has to be scale invariant? When reading about conformal anomalies, such as in this paper it is often stated that the anomaly (ie.  \delta W[g]/ \delta \sigma where  W[g] is the quantum effective action for gravity) must be ... 0answers 39 views ### Thermal AdS3 in Chern Simons I am currently working with (2+1) gravity in Chern-Simons formulation and I have a question about thermal AdS. The way I understand that one retrieves thermal AdS is by Wick rotation and ... 0answers 54 views ### Fluctuating string in AdS black hole People frequently use fluctuating string in AdS black hole (see 1,2,3 etc) to study dynamics of a "free external quark" in quark-gluon-plasma (QGP) at finite temperature. The background black hole ... 0answers 96 views ### Boundary stress-energy tensor form ADS/CFT In "Gravitational Dynamics From Entanglement "Thermodynamics"" by Lashkari/McDermott/Van Raamsdonk, the authors derive the linearised Einstein equations from ADS/CFT. At page 6 they use$$t_{\mu{\nu}}(...
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I am a bit confused about the status of naked singularities that appear in black hole physics and more so in the context of AdS/CFT. Here is what I know about this in brief. For a charged Reissner-...
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### Solution of Dirichlet problem for scalar field in Ads

I am reading "Anti de Sitter space and holography" by Witten. In this article he derives the two-point function for CFT from theADS/CFT correspondence for a massless scalar field living in the bulk. ...
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### Near horizon limit of near-extreamal black brane

It is known that the near horizon limit of a ($d+1$) dimensional extremal charged black hole (BH) is $AdS_2\times S^{d-1}$. I was looking at this paper by Faulkner et al. They consider a ($d+1$) ...
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### Witten diagrams and the precise statement of the AdS/CFT correspondence

I'm reading Witten's early paper on AdS/CFT. My understanding is that, on the gravity side, you vary the action to find the full, classical equations of motion, solve them subject to arbitrary ...
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### What is the meaning of weakly coupled in gravity theories?

In a Colloquium lecture of Juan Maldecena, He states that weak coupling states the theory is hard to change the metric. And tolds that weakly coupled system requires a lot of fields. Can you give ...
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### Norm of Dilatation operator [closed]

The dilatation operator is given by $$D=x^{a}\frac{\partial}{\partial x^{a}}+z\frac{\partial}{\partial z}$$ How the norm can be $$D^{2}=\frac{L^{2}}{z^{2}}(\eta_{\mu\nu}x^{\mu}x^{\nu}+z^{2})$$ where ...
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### Dual of the Identity operator (AdS/CFT)

We know that in a CFT the spectrum of gauge invariant operators must contain an Identity operator (for the operator algebra to close). For those CFTs that admit a holographic dual what does the ...
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### AdS/CFT: why is the fifth coordinate in AdS space inversely proportional to an energy scale?

In several different articles about the AdS/CFT correspondence, it is stated that one can show that the fifth coordinate $z$ on the AdS side, in coordinates such that the AdS metric becomes: ds^2 = ...
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### Massless limit to massive scalar in AdS space

I was trying to solve massive scalar wave equation in AdS spacetime (or rather in BTZ). I noticed few funny things : The $m\to 0$ limit to the solution is subtle. One of the two independent ...
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### String Field Theory and AdS/CFT

I am a PhD student and I am choosing the topic to work on in the graduate school. I am interested in various non-perturbative aspects of String Theory. Does anybody know if there were any attempts to ...
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### Can a particle tunnel from inside a black hole?

Event horizon isn’t special from GTR standpoint, and at least in AdS/CFT correspondence gravity can be “removed” from consideration entirely. So can a particle whose wave function is completely inside ...