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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State space of strings: Spin-1 particles in the conformal gauge?

I obviously have a problem with basics of group theory. consider an open string in flat spacetime. there are usually two common gauge to solve the classical problem and quantize the strings: ...
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138 views

Generalisations of AdS/CFT with string theory on both sides

From my previous post, I found out from the comments that there are various generalisations of AdS/CFT with different things replacing the CFT on the RHS; such as AdS/CMT, AdS/QCD, and also with ...
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2answers
194 views

Strings and their masses

How do strings present in particles give mass to them? Is it only by vibrating? I have been trying to find the answer but could not find it anywhere, can this question be answered?
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1answer
159 views

A question about BRST current in bosonic string theory

I have a question about Eq. (4.3.3) in Polchinski's string theory book volume I, p. 131. It is said Replacing the $X^{\mu}$ with a general matter CFT, the BRST transformation of the matter fields ...
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1answer
83 views

A question of BRST symmetry of bosonic string theory

This question relates to this post I tried to verify Eq. (4.2.7) in Polchinski's string theory book vol I p. 127 but I miserably miss a sign $$ \delta_B (b_A F^A) = i \epsilon (S_2 + S_3) ...
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115 views

How do I show the existence of a conserved ghost number with BRST in bosonic string theory?

I have three questions about the BRST symmetry in Polchinski's string theory vol I p. 126-127, which happen together Given a path integral $$ \int [ d\phi_i dB_A db_A d c^{\alpha}] ...
2
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0answers
64 views

About the most general (diff$\times$Weyl)-invariant and Poincare-invariant form of action

I have a question about the most general (diff$\times$Weyl)-invariant and Poincare-invariant form of action. In Polchinski's string theory p15, there is an action for manifold without boundary ...
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1answer
125 views

Regularization and renomalization in the lightcone quantization of bosonic string

This question relates to this link. But I still don't understand it >_< In Polchinski's string theory vol I, p. 22, there is a divergence term (when $\epsilon \rightarrow 0$) in the zero point ...
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1answer
191 views

Energy of a string

What is the correct definition of the energy of a string ? I suddenly get confused with the definition of the energy of a string. Considering, for instance, a bosonic open string in the light-cone ...
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1answer
346 views

Why Weyl invariance is important for consistent string theory

This post is related to this link. I know there is a Weyl invariance for the Polyakov action at least in classical level. My question arises from obtaining effective action in string theory, such as ...
5
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1answer
212 views

The basic equation of bosonization

[..quoting from Page 11 of Polchinski Vol2..] Given $1+1$ conformal bosonic fields $H(z)$ one has their OPE as, $H(z)H(0) \sim -ln(z)$ Then from here how do the following identities come? ...
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1answer
159 views

Is the conjecture about $E(11)$ and M-theory (West's conjecture) generally accepted?

I was reading this paper by West, in which it is argued that: Eleven dimensional supergravity can be described by a non-linear realisation based on the group $E\left(11\right)$ From ...
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94 views

What is the entropy of a string?

In his The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics (p. 373) Susskind states that the entropy of a string is [...] proportional to its length. ...
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37 views

Moduli potential in Type IIB String Theory

In the book String Theory and M-Theory by K. Becker, M. Becker and J.H. Schwarz: Why is the potential for moduli given by eq (10.168): $$\tag{10.168 }V(T,K) ~=~ \frac1{4\mathcal{V}^3} \Big( ...
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1answer
65 views

How does one extract the universal part of entanglement entropy?

I want to know how equation 2.11 (page 9) follows from 2.10 (page 8) in this paper. The two references mentioned just before 2.11 also seem to skip this crucial step. Unless I am missing something ...
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134 views

Orientifold Plane, Anti-Dp Brane and SUSY breaking

In "String Theory and M-Theory" by K. Becker, M. Becker and J.H. Schwarz, page 222, they give a brief introduction about the (space-filling) Orientifold Plane $O9$ as an object needs to be add in the ...
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1answer
956 views

Zero modes ~ zero eigenvalue modes ~ zero energy modes?

There have been several Phys.SE questions on the topic of zero modes. Such as, e.g., zero-modes (What are zero modes?, Can massive fermions have zero modes?), majorana-zero-modes (Majorana zero ...
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2answers
370 views

Newtonian gravity from the holographic principle?

Can one understand Newton's law of gravitation using the holographic principle (or does such reasoning just amount to dimensional analysis)? Following an argument similar to one given by Erik ...
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1answer
170 views

Dimension & non - locality problem in string theory

I have some questions with string theory: Why is it that there is exactly 4 large spacetime dimensions while the rest remain small? It is a nonlocal QFT. How could that fit in GR?
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1answer
161 views

When is entanglement entropy the same as free energy?

I am given the feeling that there exists scenarios when this equality holds. Can anyone state/refer to the situations? One case that I hear of is that for $2+1$ CFTs the entanglement entropy ...
6
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0answers
140 views

Why is it hard to give a lattice definition of string theory?

In Polyakov's book, he explains that one possible way to compute the propagator for a point particle is to compute the lattice sum $\sum_{P_{x,x'}}\exp(-m_0L[P_{x,x'}])$, where the sum goes over all ...
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1answer
86 views

How to obtain the constant $a^g$ in Eq.(2.7.19) in Polchinski's string theory book

Excuse me, I have calculated $a^g$ a lot of times, using the relation between $:\;:$ and ${}^{{}_\circ}_{{}^\circ} \; {}^{{}_\circ}_{{}^\circ}$. But I can't get the same result with the book. It is ...
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1answer
385 views

The future of supersymmetry [duplicate]

Considering the fault of any experimental evidence from LHC for supporting the supersymmetry idea until now, can we say that it is dead? Generally the people who are working on this subject say that ...
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1answer
251 views

Does string/M-theory address higher-dimensional membrane vibration modes?

A loop is a 1-sphere that can vibrate in increasingly complex ways as it is embedded in higher dimensional spaces. Does string theory assume that 1-spheres are the only possible vibrating ...
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1answer
552 views

bc CFT Energy-momentum tensor from Noether's theorem

Following Polchinski's book (String Theory 1), we have the bc action : $$S = \frac{1}{2 \pi}\int~d^2z ~b\bar \partial c\tag{2.5.4}$$ where $b$ and $c$ have holomorphic weights $\lambda$ and $1- ...
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3answers
793 views

The Chern-Simons/WZW correspondence

Can someone tell me a reference which proves this? - as to how does the bulk partition function of Chern-Simons' theory get completely determined by the WZW theory (its conformal blocks) on its ...
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1answer
306 views

About the general expression of trace anomaly and CFT partition functions

I have put up a question here, http://mathoverflow.net/questions/139685/proof-of-the-general-expression-for-anomaly-in-a-cft-and-its-partition-function Here I am putting up a slightly different ...
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1answer
56 views

How to see timelike excitation has a negative norm from the “old covariant quantization”

I have a question in reading Polchinski's string theory vol I p 123, about the "old covariant quantization". It is said ... $\langle 0;k | 0; k' \rangle = ( 2\pi)^D \delta^D (k-k') \tag{4.1.15}$ ...
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1answer
89 views

A question related to “old covariant quantization” of string theory

I have a question about "old covariant quantization" in Polchinski's string theory p. 123. It is said The only nontrivial condition at this level is $(L_0^{\rm m} + A) | \psi \rangle =0 $, ...
2
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1answer
224 views

Deriving entanglement entropy from Renyi entropy

My questions are based on this paper - http://arxiv.org/abs/0905.4013 Firstly I want to know as to whether some assumptions are needed about the relationship between the systems $A$ and $B$ for the ...
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1answer
104 views

Virasoro operator in “old covariant quantization”

I met some problem about the Virasoro operator in "old covariant quantization" in Polchinski's string theory vol I p 123. It is given $$L_0^{\rm m}=\alpha' p^2 + \alpha_{-1} \cdot \alpha_1 + \cdots ...
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1answer
135 views

A question about the higher-order Weyl variation for the geodesic distance

I have a question in deriving Eqs. (3.6.15b) and (3.6.15c) in Polchinski's string theory vol I p. 105. Given $$\Delta (\sigma,\sigma') = \frac{ \alpha'}{2} \ln d^2 (\sigma, \sigma') ...
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2answers
169 views

A question for the generalization of gauge transformation with two antisymmetric indices

I have a question about the generalization of gauge transformation with two antisymmetric indices. Starting from Eq. (3.7.6) in Polchinski's string theory book p. 108. $$S_{\sigma} = \frac{1}{4 \pi ...
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0answers
345 views

What are the basic postulates of string theory? [closed]

I read the Popular Science books, The Brief history of time (Hawking), The fabric of the cosmos (Greene), and The Grand Design (Hawking), etc. but did could not manage to understand what string ...
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1answer
79 views

A question about the Weyl transformation for the vertex operator of the closed-string tachyon

I met a problem of derving the Weyl transformation on the closed-string tachyon, Eq. (3.6.8) in Polchinski's string theory, vol 1, p 103. Given the vertax operator of the closed-string tachyon ...
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1answer
147 views

Vertex operator for closed string tachyon

The problem related to this post, but my question is even more elementary. In p 101 of Polchinski's string theory vol I, it is stated Using the state-operator mapping, the vertex operator for the ...
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1answer
166 views

A question about Poincare invariance of Polyakov action

I have a question the variation of the Polyakov action, related to this Phys.SE post. For Polyakov action $$ S_p[X,\gamma]=-\frac{1}{4 \pi \alpha'} \int_{-\infty}^{\infty} d \tau \int_0^l d \sigma ...
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1answer
200 views

A question about Lorentz invariance of the Polyakov action

I have a super basic and stupid question about the Lorentz invariance of the Polyakov action (cannot skip the disclaimer..) $$S_p[X,\gamma]=-\frac{1}{4 \pi \alpha'} \int_{-\infty}^{\infty} d \tau ...
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2answers
87 views

A question about surface term of ghost fields

(skip disclaimer) Hi, I have a question in Polchinski's string theory vol I p 90, after introducing the ghost fields $b_{ab}$ and $c^a$, it is claimed The equations of motion then provide a ...
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1answer
319 views

How are low energy effective actions derived in string theory?

For example the eq 2.1 here with regards to Type IIB. Unless I am terribly missing/misreading something Polchinski doesn't ever seem to derive these low energy supergravity actions. I would like to ...
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1answer
72 views

A question about variation of metric under Weyl and coordinate transformations

I have a question about deriving variation of metric under Weyl and coordinate transformations in Polchinski's string theory (3.3.16). Under transformation $$\zeta: g \rightarrow g^{\zeta}, \,\,\, ...
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3answers
340 views

What does string theory say about the metric expansion?

Specifically, what happens to those small intertwined hidden dimensions? Do those expand too?
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1answer
144 views

Euler number of the world sheet

I have a question in the section 3.2 "The Polyakov path integral" in Polchinski's string theory p. 83. Given $$ \chi=\frac{1}{4 \pi} \int_M d^2 \sigma g^{1/2} R + \frac{1}{2 \pi} \int_{\partial ...
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1answer
142 views

A question about vertex operator

(skip disclaimer) I have a question about writing raising and lowering operators in the Schroedinger basis in the section of vertex operator in Polchinski's string theory vol 1 p.68. It is given ...
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1answer
330 views

${f=ma}$: a duality between F-theory and M-theory?

$$F = M \Big|_{A(T^2) \to 0}$$ The above equation is the duality equation between F-theory and M-Theory on a vanishing 2-torus. What's the explanation for this equation? Is there anything similar ...
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1answer
166 views

About the conserved charge for the ghost number current in $bc$ conformal field theory

(skip disclaimer) I have a question about the conserved charge for the ghost number current in $bc$ conformal field theory in Polchinski's string theory p62. It is said For the ghost number ...
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1answer
126 views

Anticommuting relation in $bc$ CFT

(skip disclaimer) I have a question about conformal field theory in Polchinski's string theory vol 1 p. 61. Given anticommuting fields $b$ and $c$ and the Laurent expansions $$ b(z) = ...
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1answer
146 views

SL(2,R) to SL(2,Z) in Type IIB String Theory

I heard from Prof. Katrin Becker (in her "SUSY for Strings and Branes - Part 1" lecture) that the classical $SL(2,\mathbb{R})$ symmetry in type IIB String theory becomes $SL(2,\mathbb{Z})$ in Quantum ...
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67 views

one loop correlator in ads cft

Is there any example of explicit one loop computation for Witten diagrams? It seems like it will be hard to compute for even for a simple $\phi^4$ theory in the bulk.
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2answers
150 views

A question about Virasoro algebra

(skip disclaimer) I have a question in Polchinski's string theory book volume 1 p54, related to the Virasoro algebra. Introducing complex coordinates $$w=\sigma^1 + i \sigma^2 $$ $$z=\exp (-i ...