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Questions tagged [string-theory]

A class of theories that attempt to explain all existing particles (including force carriers) as vibrational modes of extended objects, such as the 1-dimensional fundamental string. PLEASE DO NOT USE THIS TAG for non-relativistic material strings, such as, e.g., a guitar string.

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Is it 4-D or 11-D Universe? [on hold]

I know these are just theories, but I wish to know which of the two are the most used right now to speculate how many dimensions of space and time our universe has. I heard that in the standard ...
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30 views

Kinematic aspects of quantum gravity

Quantum gravity proposals at the leading perturbative order, such as the quantisation of linearized gravity, or the low-energy effective action like in string theory, provide the dynamics for the ...
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1answer
48 views

Quantum expressions for the Virasoro constraints

I am trying to derive the quantum form of the Virasoro constraints. $$ L_{m} = \frac{1}{2} \sum_{n} :\alpha_{m-n}.\alpha_{n}: $$ :...: meaans normal ordering. Using the common commutator between ...
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1answer
30 views

What superstring or brane phenomenology can be observed in LHC heavy ion collisions?

What superstring or brane phenomenology can be observed in heavy ion collisions at the LHC energy densities. Of course, I am aware that LHC experiments can constrain the conclusions from the ...
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0answers
61 views

Does a Black-hole Represent a Limit To The Value of Energy-density? [closed]

I've recently read an article that stated the singularity of a black hole could be a string, which is stipulated to be pure energy. If that's the case, does this mean that the singularity of a black ...
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23 views

What is the simplest possible explanation of the String Theory? [duplicate]

I was recently reading through 'The Little Book of String Theory' by Steven S. Gubser, and found it too complicated. Now, some people may say that the string theory is meant to be complicated as even ...
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34 views

Penrose diagram of Janus black holes

Recently I'm interested in the Janus black holes, it's a solution of three dimensional Einstein-scalar action which can be embedded in ten dimensional type IIB supergravity with appropriate ansatz. ...
2
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1answer
73 views

Why can AdS/CFT correspondence be applied to condensed matter systems when their space is not anti-deSitter?

The AdS/CFT correspondence postulates a duality between string theory of gravity and a CFT on an AdS background. This duality is employed in some condensed matter systems. I was wondering why it is ...
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1answer
38 views

Relationship between compactification moduli and generations in standard model

The situation I am describing is a $10D$ heterotic string theory which is compactified on a Calabi-Yau to get a $N=1$, $4D$ effective theory. It is mentioned in Ashoke Sen's notes on string ...
2
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1answer
65 views

Are there other types or versions of holographic principle?

Holographic principle (https://en.wikipedia.org/wiki/Holographic_principle) establishes a correlation between a bulk and its boundary. It says, in layman terms, that the amount of information in a ...
2
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1answer
51 views

Energy of string in bosonic string theory

When we start from the Polyakov action, we can choose to work in the conformal gauge $h^{\alpha\beta}=\eta^{\alpha\beta}$ where $h^{\alpha\beta}$ is the metric on the world-sheet and $\eta^{\alpha\...
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1answer
79 views

Does string theory violate general covariance?

In a 2007 note on ArXiv, it said: String theory unifies all interaction but provides a perturbative background dependent formulation which violates general covariance. However, another 2012 paper ...
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42 views

Does the background shift affects the renormalization group equations?

In Section 21 of "Quantum Field theory" by Mark Srednicki, it is shown that there are two equivalent ways to get the quantum action of the shifted field $\phi'= \phi-\tilde{\phi}$, where $\phi$ is the ...
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1answer
87 views

Do strings propagate through space time or do they make space time?

In the beginning of string theory textbooks, strings are said to live in a background "target" space time. They then propagate through this space time. Strings also have a spin 2 ("graviton") mode, ...
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1answer
45 views

Are the “extra dimensions” in string theory universal?

Are the extra (compactified) dimensions from string theory universal, in that any particle/field with a sufficiently small enough wavelength will be able to propagate through them? The reason I want ...
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3answers
244 views

Does string theory accommodate effects of dark energy?

String theory is arguably, among best candidates for a Theory of Everything. So, because every TOE is an attempt to bind together the big and very small effects and things, a TOE must be able to ...
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0answers
27 views

Aharony-Bernman-Jafferis-Maldacena (ABJM) and k=1 Chern Simons matter

I have read recently that the partition function / half-BPS wilson vev (w/ NG probe) of a Chern-Simons matter theory with N=6 U(N)k x U(N)-k super-conformal symmetry (ABJM) on S3 is proportional to ...
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0answers
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Resources on Gubeser-Klebanov-Polyakov (GKP) strings and N=4 Super-Yang Mills dual description

*I have learned recently that the Gubeser-Klebanov-Polyakov string / folded string in AdS3 (if I recall correctly, and I assume with some additional virasoro constraints, etc) is dual to large-spin ...
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47 views

Understanding Moonshine via Heterotic E8xE8 (resubmitted, originally asked on mathematics stack exchange)

Recently I have become familiar with the conjectured relationship of monstrous moonshine and pure (2+1)-dimensional quantum gravity in AdS with maximally negative cosmological constant and, it’s being ...
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2answers
81 views

Where is the Physical Singularity under the Holographic Principle?

From this article, it states that The holographic principle states that the entropy of ordinary mass (not just black holes) is also proportional to surface area and not volume; that volume itself ...
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1answer
38 views

Mass formula for open string with mixed boundary conditions

I want to give an expression for the mass formula of an open string with has Neumannn condtion in $m$ directions and Dirichlet in $n$ directions $X^{i}(\sigma ^{1}=0)=x_{0}^{i}, X^{i}(\sigma ^{1}=\pi)=...
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0answers
51 views

How does Alain Connes NCG compare phenomenologically with superstring theory?

In Veltmans book on QFT, diagrammatica, the full SM Lagrangian is published. There are more than a hundred terms and it looks pretty uninspiring and not quite the kind of equation one would want to ...
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Free Field Realization of Current Algebras and its Hilbert space

I have some conceptual confusion regarding the interplay between current algebras, their free field representation and the Hilbert space generated from it. Let's sketch a simple example, $\mathfrak{...
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1answer
64 views

If strings of matter are of the same substance how can matter carry differing charges?

Considering that a string is a loop of energy composed of the same underlying material how is it possible for it to be either positively or negatively charged? For that matter, how is it possible for ...
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1answer
39 views

Generalization of Chern-Simons Wilson Line

The Wilson line in Abelian Chern-Simons theory is $$\langle\exp\left(i\int dt\dot{x}^{\mu}A_{\mu}\right)\rangle=\int\mathcal{D}A\exp\left(i\int dt\dot{x}^{\mu}A_{\mu}+\frac{i}{4\pi}\int A\wedge F\...
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1answer
39 views

Root weights and states in orbifold compactifications

I have the following question regarding orbifold compactifications of the heterotic string: What is the relation between a certain representation and the weights of the root lattice? I mean: take ...
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1answer
40 views

Question about Mode expansion of free compact boson

$(1+1)$-Dim free compact boson, Lagrangian is $$\mathcal{L}= \frac{1}{2}(\partial_\mu\phi(\sigma,t))^2$$ with $\phi(x,t)\sim\phi(x,t)+2\pi r$ and periodic boundary condition along $x$, i.e. $\phi(\...
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0answers
19 views

Branes without Fayet-Iliopoulos term

Often D-brane effective actions are given as (let's take D3-branes) $$ S=-T\int d^4x \sqrt{-det(g_{mn}+2\pi\alpha'F_{mn})}. $$ After expansion in $2\pi\alpha'$ there is a constant Fayet-Iliopoulos ...
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1answer
54 views

What happens to the $U(1)$ factor in the $U(N)$ SYM gauge group of the AdS/CFT correspondence?

I'm learning about the AdS/CFT correspondence. I know that from the open string perspective, the dynamics on a stack of $N$ coincident $D3$-branes is given by a $\mathcal{N} = 4$ Super Yang Mills ...
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0answers
28 views

Differentiating D3 brane worldvolume theories with NS5 brane and NS5 antibrane boundary conditions

In 'Supersymmetric Boundary Conditions in N=4 Super Yang-Mills Theory', Gaiotto and Witten derive boundary conditions for the worldvolume theory of the D3 brane. In particular the boundary conditions (...
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1answer
58 views

Transformation algebra of supersymmetry transformation

Given supersmmetry transformation: $$δX^\mu = i\barξψ^\mu.δψ^\mu = ξγ^a(∂_aX^\mu-\frac i2\barχ_a ψ^\mu). δχ_a = 2 D_aξ.$$ How to calculate the transformation algebra of $X^\mu$ and $\psi^\mu$? ...
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166 views

Supersymmetry and reparametrization invariance of superstring action

Section $4.3.5$ Superstring action and its symmetries, Page$229$ Superstring theory by Green, Schwarz and Witten. $S_1=-\frac1{2π} ∫d^2σ\ eh^{αβ}∂_αX^μ∂_βX_μ.\quad S_2=\frac i{2π}∫d^2σ\ e\barψ^μρ^α∇...
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0answers
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A generalized Veneziano formula for p-branes?

The rise of string theory as a theory of quantum gravity is in debt to G. Veneziano and his formula for the string scattering in terms of Euler beta function. Could a generalization of that formula, ...
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48 views

Lattice model realization of $SU(2)$ WZW model at level $k$?

Is there any lattice model realization of the following model: $c=1$ boson at the self-dual radius, or the $SU(2)$ WZW model at $k=1$. This is a question inspired by: Orbifolds of the $c =1$ ...
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1answer
70 views

Number of strings? [duplicate]

Is each particle associated with an unique string and where exactly is the string located, if it's vibration produces the appearance of a particle? What I mean is if I see an electron, does it have an ...
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0answers
43 views

Symmetries on String theory

Recently I was watching and reading about String theory, M-theory and the supersymmetry, when I remembered one question that I had while reading 'The Elegant Universe' by Brian Greene that is: why do ...
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Partition function computation on a Riemannian Manifold

This discussion comes from Chapter 10, Mirror Symmetry. I am given a Riemannian manifold $M$, and a classical (Euclidean) theory: $$(1)\quad S_E={\int}_0^\beta d\tau\space\Bigl(\frac{1}{2}g_{ij}{\dot{...
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0answers
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Superstrings and supermembranes withouth the maximal spin constraint

Can supermembranes exist in higher dimensional superspaces if we admit higher spin fields?
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42 views

Are there any practical implications of string theory? [duplicate]

In my understanding, Strings theory tries to establish a functional model explaining how the world works. What are some practical applications of string theory? Would a solution to one of the ...
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0answers
79 views

Diffeomorphism invariance of scattering amplitude in bosonic string theory

It is mentioned in Polchinski's book (vol 1) that the diffeomorphism invariance of the scattering amplitude (see Polchinski, vol 1, eq 5.3.9) follows from the equation of motion of $b_{ab}$ (see ...
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1answer
66 views

Emergent physics in the gap between the Planck scale and the “size” of quarks [closed]

The smallest probed length scale to date is around $\Delta x \approx 10^{-18} m$ (see here). If we compare this to the Planck scale of $\Delta x \approx 10^{-35} m$ we are left with almost 20 orders ...
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1answer
228 views

String behavior in electron orbitals?

It feels like this should be a incredibly easy question to find an answer to, but I’m coming up zeroes in my search - if I’ve overlooked a parallel question please feel free to close this. ...
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2answers
227 views

Weyl anomaly in 2d CFT (string theory lectures by D.Tong)

In his lectures on String Theory (http://www.damtp.cam.ac.uk/user/tong/string.html), Tong gives a proof of the Weyl anomaly, using equation $(4.36)$. It seems wrong to me. Here he uses the OPE ...
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1answer
32 views

Effective low energy actions in string cosmology

I wonder why can SUGRA actions be used in string cosmology, since in some cases they are used to model big bang scenarios (for example the pre big bang scenario in chapter 4 of Gasperini's "Elements ...
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1answer
205 views

What is a theory of gravity?

Let me introduce this question by noting that my training is in condensed matter physics, and my familiarity with gravity is superficial at best. Hence, this question may be somewhat naive. In ...
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0answers
73 views

Does string theory need operator formalism to quantize?

Can we really use path integral approach to quantize for (first-quantized) string theory? This question is motivated from the following fact: even though we can establish exact correspondence between ...
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1answer
71 views

Why do we consider solitons as a composite object?

Can someone explain why do we consider solitons as a composite object? I know that there are dual theories which the role of fundamental and solitonic objects can be mapped to each other, but I can't ...
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1answer
46 views

Equation of motion for a massless scalar in 2 dimensions

I'm working through Polchinski's String Theory (Volume 1, Chapter 2, page 34), with $D$ scalar fields: The action is given by $$ S = \frac{1}{2 \pi \alpha'}\int d^{2}z \partial X^{\mu} \overline{\...
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1answer
63 views

Can holography be applied to every model?

Can all models have a holographic representation? I was talking with a physicist and he told me: "Holography is not a property you can just apply to any model of the universe willy-nilly. It either ...
2
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1answer
227 views

Should all black holes have Bekenstein-Hawking entropy especially in string theory?

There are so many confusing descriptions of how Bekenstein-Hawking entropy binds black holes, and thus the question. I previously asked similar questions, but I realized questions were misleading and ...