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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What are the implications of the Holographic principle?

What are the implications for the Holographic principle? I understand the basics of the principle, the relationship with black holes and string theory but what this is going to tell us? Does it help ...
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119 views

Questions about Type HE Matrix String Theory

I was reading the heterotic string section of this thesis desertation by Luboš Motl, since I think I now understand the Type IIA Matrix String Theory. The only thing I knew about Type HE Matrix ...
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222 views

What happens to the amplituhedron in a non-peturbative context?

The Amplituhedron has recently been popular; it supposedly encodes perturbative scattering amplitudes in a simple, geometric fashion. What happens to it in a non-perturbative context? Is there ...
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388 views

What is the definition of a “UV-complete” theory?

I would like to know (1) what exactly is a UV-complete theory and (2) what is a confirmatory test of that? Is asymptotic freedom enough to conclude that a theory is UV-complete? Does it become ...
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342 views

Is integrability necessary for the Amplituhedron?

It is well known that there exist mappings between operators in N = 4 Super Yang–Mills and spin chain states making the theory Bethe Ansatz integrable. Is integrability a necessity for the ...
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53 views

Extra dimensions and the big bang [duplicate]

If there were extra compact dimensions,and at the big bang all dimensions were compact,my question is why the big bang failed to expand those presumed extra dimensions like it did with the 3 spatial ...
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2answers
825 views

If gravity doesn't exist,what are the implications? [duplicate]

I just heard about new theories proposed by Erik Verlinde about the fact that Gravity doesn't exist..or at least it's not a foundamental force. My question is : if this is true what are the ...
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328 views

Do I need to study the “Standard Model” before studying String Theory?

After this semester, I'll have a background up to a first course in QFT (first 5 or 6 chapters of Peskin and Schroeder). The next step in QFT will be something specific to the Standard Model ...
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A question about inverse Green's function

(The background is in a book, An introduction to String Theory and D-brane Dynamics 2nd, by Richard J Szabo p87, Eq. (6.31)) Given $$N(\theta,\theta')= - \frac{1}{\pi} \sum_{n=1}^{\infty} \frac{ ...
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103 views

UV-IR cancellation of the open string cylinder diagram and the field theory limit

In string theory, the ultraviolet divergences of open string loop diagrams are reintepreted as closed string infrared divergences, by seeing that an annulus with a small loop is also a long tube. In ...
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174 views

Explanation for the minus sign in $\Omega_3$ in the Kappa symmetry of the Green - Schwarz formalism for F1 strings

Just so that there can be more higher - level physics questions here, let me post this question + answer. Also because I'm a bit sad that there are almost no questions on the Green-Schwarz ...
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157 views

Renormalizability of the Polyakov Action

I was told today that the Polyakov action for a $p$-brane is (superficially) re-normalizable iff $p\leq 1$. Of course, when I went to check for myself, I screwed up my power-counting, and I'm having ...
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663 views

Derivation of the Polyakov Action

As is usually done when first presenting string theory, the Nambu-Goto Action, $$ S_{\text{NG}}:=-T\int d\tau d\sigma \sqrt{-g} $$ ($g:=\det (g_{\alpha \beta})$ is the induced metric on the ...
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105 views

A question about the coupling between string and gauge field $A_{\mu}$

I have a question about deriving the coupling term of string and the gauge field on brane. According to David Tong's lecture note p184/(191 in acrobat), the coupling is given by $$ ...
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100 views

Polchinsky's Evaluation of the One Loop String Path integral

I try to evaluet the matrix M in the Polchinsky's article(Communications in Mathematical Physics,1986, Volume 104, Issue 1, pp 37-47,"Evaluation of the one loop string path integral",Joseph ...
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191 views

What are the good introductory resources for M-theory towards AdS/CFT? [duplicate]

I see a list here with a section titled M-theory - http://www.superstringtheory.com/links/reviews.html In there these two look promising, http://arxiv.org/abs/hep-th/9607201 and ...
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198 views

Curved spacetime as a coherent state in string theory

I have a question about Polchinski's string theory book, volume I, p 108. When we write the Polyakov action in curved spacetime, it is said $$ S_{\sigma} = \frac{1}{4\pi\alpha'} \int_M d^2 \sigma ...
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91 views

SuperConformal approach to SuperGravity

In the book (Supergravity - Daniel Z.Freedman & Antoine Van Proeyen - Cambridge), there are (Chapters 16-17) a presentation of pure supergravity or supergravity with matter, from a SuperConformal ...
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357 views

Expectation value of the stress-energy tensor in 2-D CFT

Due to a previous question, I am confused with the expectation value of the stress-energy tensor in a 2-D conformal field theory. Let's take the example of string theory, to sketch the problem. ...
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118 views

Is Veneziano amplitude able to explain the physical properties of strongly interacting hadrons (such as proton and neutron)? [duplicate]

In theoretical physics, the Veneziano amplitude refers to the discovery made in 1968 by Italian theoretical physicist Gabriele Veneziano that the Euler beta function, when interpreted as a scattering ...
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3answers
183 views

A question about an identity in deriving Born-Infeld action

I have a question in David Tong's Example Sheet 4 Problem 5b, how to verify the last equation (*) on p.2? (There is a solution for example sheet 3, but seems to be no solution for example sheet 4.) ...
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2answers
460 views

3 Questions about modern Physics [closed]

First i'd like to apologize for both my writting skills (i'm not english) and for my physics knowledge (being them very basic and/or naive). With general relativity from Einstein, gravity is no ...
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313 views

Why does one of the extra dimensions of F-Theory have to be a temporal dimension?

F-Theory, as I understand it, is a realisation of Type IIB String Theory as a 12-dimensional theory in such a way that the $SL(2,\mathbb Z)$ symmetry becomes natural because Type IIB String Theory is ...
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2answers
111 views

Factor of two differences for free field Green's functions in conformal field theory

I have a question about the expressions for free field Green's functions in conformal field theory. It comes from three origins 1) In Polchinski's string theory volume I p36, it is given $$ ...
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288 views

Defining Euclidean global AdS

How does one see that that the Euclidean AdS is the same as the hyperbolic space at the same dimension ie $EAdS_n = \mathbb{H}_n = SO_0(n,1)/SO(n)$? Or is this to be seen as the definition of ...
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430 views

Symmetric transverse traceless tensors of rank $s$ and $(s,0,0,..,0)$ representations of $SO(n)$

Can someone help see this connection as to why a spin $s$ (an Integer) particle is to be thought of as a symmetric transverse traceless tensor of rank $s$ and that they lie in the $(s,0,0,..,0)$ ...
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396 views

Why does string theory have such a huge landscape?

I was browsing through Foundations of Space and Time, a compilation of essays on various theories of quantum gravity. The following passage in the introduction intrigued me: Each compactification ...
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1answer
790 views

What is Mathematical formulation of Holographic principle? [closed]

What is Mathematical formulation of Holographic principle The holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can ...
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70 views

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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141 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
196 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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164 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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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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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}] ...
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65 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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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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203 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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351 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 ...
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214 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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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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98 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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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
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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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143 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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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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375 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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174 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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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 ...
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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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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 ...