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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3
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1answer
51 views

Dirac operator partial integration

When you have an action with bosonic $X$ and fermionic $\psi$ (Majorana) fields and perform a SUSY transformation $\epsilon$ (the constant, infinitesimal parameter of transformation, a real, ...
0
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0answers
45 views

Regarding Randall Sundrum model

In Randall Sundrum model 2, that is the one with non compact fifth dimension, there is only one brane, which is the Planck brane. The TeV brane is removed by taking the radius of the fifth dimension ...
3
votes
0answers
76 views

Non-abelian bosonization

Reading this review about non-abelian bosonization, Non-abelian bosonization by I.Karmazin, I stumbled about two questions Below equation 6, I don't get the final point in the statement about the ...
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votes
1answer
53 views

Simple question [closed]

How much of this can you understand and which videos or simplified ways would you suggest for me to understand more? http://www.youtube.com/watch?v=2rjbtsX7twc I understood about... 3%... I ...
3
votes
0answers
614 views

holographic principle and Wheeler's bag of gold

How is it possible to explain "bag of gold" spacetimes (see Marlof) such that the ideas are compatible with AdS/CFT and the holographic principle?
5
votes
1answer
68 views

Questions on D branes and their role in the AdS/CFT correspondence

I'm a beginner in learning the AdS/CFT correspondence, and I come across two problems that I hope an answer will be given here. D branes in string theory are usually introduced through the T-duality ...
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0answers
61 views

Is Functional Analysis used at all in String Theory? [closed]

Is functional analysis used at all in string theory? (and if so, how?)
10
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1answer
247 views

Equation of state of cosmic strings and branes

I'm sure these are basic ideas covered in string cosmology or advanced GR, but I've done very little string theory, so I hope you will forgive some elementary questions. I'm just trying to fit some ...
1
vote
1answer
74 views

Can the strings in string theory be thought of as troughs in a field?

I figure that string theory is a new breed of QFT which looks at fields in terms of a network of strings and also incorporates gravity into its module, however my question is that since elementary ...
0
votes
1answer
82 views

breitenlohner freedman stability condition

I am looking for a simple way to derive the breitenlohner-freedman bound. Actually I can't understand why we have stability above the BF bound and instability below the BF bound,while both have ...
-4
votes
1answer
106 views

Why do we believe in a “force” driven universe? [closed]

Why do we not believe in the potential for a "unified force field" universe, to the exclusion of the belief in the potential for a mechanical, gear driven universe, if the correct shape for the gear ...
0
votes
0answers
29 views

How does lattice field theory relate to string theory?

The former is sort of a "mapping" technique with the goal of making quantum fields computable, while the latter wants to act as an underlying system of it. (as far as I know) What is their relation to ...
3
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3answers
461 views

Polyakov action: difference induced metric and dynamical metric

The Polyakov action is given by: $$ S_p ~=~ -\frac{T}{2}\int d^2\sigma \sqrt{-g}g^{\alpha\beta}\partial_{\alpha}X^{\mu}\partial_{\beta}X^{\nu}\eta_{\mu\nu} ~=~ -\frac{T}{2}\int d^2\sigma ...
2
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1answer
45 views

A paradoxical equation in RNS string fermionic part

It is well known for RNS string, $i.e.$, worldsheet supersymmetry formalism, the open string NS sector has worldsheet fermion expansion: \begin{equation} \psi^{\mu}_{\pm} = \frac{1}{\sqrt 2} \sum_{r ...
2
votes
1answer
550 views

Philosophical Interpretation of String Theory [closed]

I want to know whether string theory is supposed to describe the world exactly, or whether it's just an approximation of some more fundamental theory. Is it similar to how the wave-equation ...
0
votes
0answers
26 views

how to specify eigenfunctions(eigentensors) of Lichnerowicz operator?

Lichnerowicz operator is an operator which acts on transverse trace-free symmetric tensors. If this statement is correct, my question is that any transverse trace-free symmetric tensor is an ...
0
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0answers
38 views

Massive gauge string sigma model action

I want to know how to insert massive gauges in string sigma model action. For massless fields it is possible by integrating the U(1) field over the string worldsheet, but in the case of massive gauge ...
10
votes
2answers
142 views

Why do fermions come in generations, but not bosons?

Why does the $1/2$ spin of fundamental fermions (electrons, quarks, and neutrinos) split them into three variants that differ only in mass, while the integer spins of massless fundamental bosons (e.g. ...
1
vote
1answer
84 views

Is it possible to make superpartner of Standard Model live in Mirror World?

In the ordinary Supersymmetry (SUSY), the superpartner of SM live in SM world (matter world). Then we introduce mirror world with mirror particle live there. I would like to make a new concept that ...
3
votes
2answers
238 views

Quantum Yang-Mills Theory and AdS/CFT

I just read the first chapter of Becker-Becker-Schwarz. To quote: A remarkable discovery made in the late 1990s is the exact equivalence (or duality) of conformally invariant quantum field ...
2
votes
1answer
151 views

Physics in torus, cylinder, Klein bottle and mobius strip

In string theory, or supersymmetric gauge theory, they often calculate the partition function on specific Riemann surfaces, such as torus, cylinder, Klein bottle, Mobius strip. Refer to the ...
2
votes
1answer
54 views

D-brane book-keeping and non-abelianity

In Becker's book String Theory and M-Theory in the chapter about T-duality and D-brane (Chapter 6) the following comment is made The Chan–Paton factors associate $N$ degrees of freedom with each ...
2
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3answers
4k views

Why does string theory require 9 dimensions of space and one dimension of time?

String theorists say that there are many more dimensions out there, but they are too small to be detected. However, I do not understand why there are ten dimensions and not just any other number? ...
5
votes
1answer
121 views

What produces String tension in Strings theory?

In (classical) physics, tension describes the pulling force exerted by each end of a string, which is a one-dimensional continuous object, At the atomic level, tension is produced when atoms or ...
3
votes
1answer
209 views

Higgs branch and Coulomb branch

I heard that the distinguish between Higgs branch and Coulomb branch is the limit of some parameters. (If i remember correctly, something like FI parameters. ) Here i want to know what is FI ...
2
votes
0answers
56 views

Open string 4-tachyon amplitude for cylinder/annulus topology in bosonic string theory

One knows the formula for the open string $4$-tachyon amplitude for the disk topology in the bosonic string theory : it is proportional to the $s \leftrightarrow t \leftrightarrow u$ symmetrisation ...
2
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0answers
90 views

What is the future of complexity theory in black-hole physics and string theory? [closed]

I found the recent work by Hayden and Harlow and Susskind very fascinating. I have also heard talks by Scott Aaronson about this emerging connection. In particular this idea of understanding ...
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votes
1answer
103 views

Why & What extra dimensions in M-theory?

I am not into String or M theory. Recently I am again reminded that M-theory "requires extra dimensions" beyond the usual string theories, beyond the usual space-time dimensions. To me, dimensions ...
4
votes
1answer
84 views

What is the difference between D branes, M branes, and NS branes?

I know that D$p$ branes are branes with $p$ spatial dimension with satisfying Dirichlet boundary condition. I want to confirm the following things. First, I heard the D-branes are massive, and these ...
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vote
0answers
82 views

Beta function of the non-linear sigma model

In chapter 7.1.1. inTong's notes about String Theory could someone sketch how can I show the statements that he nmakes around eq. 7.5 That the addition of the counterterm can be absorbed by ...
4
votes
0answers
76 views

Relation of Betti numbers to Veneziano's scattering amplitude?

I came across Veneziano's famous formula for the scattering amplitude for four tachyons written as $$A(s,t)= \sum_{n \geq0} \frac{(-1)^n}{n-1 + ...
8
votes
0answers
574 views

String theory from a mathematical point of view

I have a great interest in the area of string theory, but since I am more focused on mathematics, I was wondering if there is any book out there that covers mathematical aspects of string theory. I ...
1
vote
1answer
66 views

D7 brane profile

I have a doubt about the differential equation leading to the profile of a d7 brane embedded in a 10 dimensional space. According to http://arxiv.org/abs/hep-th/0306018, equation (6), we have the ...
5
votes
0answers
101 views

String frame and Einstein frame for a Dp-brane

The low energy effective action for $N$ D$p$-branes in the string frame is $$ S_\text{eff} = \frac{1}{16\pi G_{10}}\int d^{10}x \sqrt{-g}\ e^{-2\phi}(R+ 4(\partial\phi)^2+\cdots) $$ where $R$ is the ...
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4answers
509 views

Quantum mechanics threshold

First of all I beg your forgiveness as I am not a physicist and the question I am going to ask may sound silly. I am aware that beyond a certain threshold in the hierarchy of building blocks of ...
2
votes
1answer
88 views

How to calculate the Wald functional?

I want to calculate the Wald functional for arbitrary higher curvature Lagrangians - like getting equation 6.31 from 6.30 in this paper. A priori the above looks like an extremely complicated ...
3
votes
1answer
234 views

Could strings be geons?

Is it possible that string theory strings are geons? This may be an overly speculative or naive question, but is there an obvious reason why not? Both strings and geons seem to have roughly the same ...
7
votes
2answers
761 views

Is string length in string theory quantized?

Is there a minimal string length (maybe the Planck length), and is it quantized? Do strings have a 0-dimensional (ie point) cross-section?
2
votes
1answer
107 views

How does string theory describe classical gravity theory, and QFT? [closed]

I am learning string theory, as I understand, gravitons exist as modes in string excitations, and also other particles. It gave me this picture: a lot of strings fulling in the spacetime, excitations ...
1
vote
1answer
96 views

Moduli spaces in string theory vs. soliton theory

In both string theory and soliton theory, moduli spaces are frequently used. As far as I known, for soliton theory, moduli spaces are something like collective coordinates for solitons, and for ...
1
vote
1answer
93 views

Difference between Veneziano amplitude and Virasoro shapiro amplitude

I have been study about Veneziano amplitude and Virasoro Shapiro amplitude. I want to summarize this two amplitude in the following way, please check that i am understand them properly. Veneziano ...
3
votes
2answers
120 views

What is the logic of not regarding perturbative renormalizability as a fundamental requirement?

I read a statement in Becker and Becker's String Theory and M-Theory page 2. After pointing out the non-renormalizablity of GR by the dimension of gravitational constant, it is said: Some ...
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0answers
61 views

Quantum to String: making the transition

We have a Hamiltonian containing a quantum simple harmonic oscillator coupled to a meter and a force. There is a term in the Hamiltonian that involves the oscillator position and the force, a term ...
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0answers
60 views

Form of Dilaton term in polarization tensor

The vertex operator associated with massless state is $$V(k,\epsilon) = -\frac{2}{\alpha}\epsilon_{\mu\nu}(k)\bar{\partial}X^\mu(\bar{z})\partial X^\nu(z)e^{ik\cdot X(z,\bar{z})}$$ The polarization ...
1
vote
1answer
77 views

The quantum state of the Universe

As far as I know, the two popular attempts to quantize gravity (string theory and loop quantum gravity) rely on unmodified quantum mechanics. Since they aim to become ToEs, this also mean that the ...
8
votes
1answer
486 views

Why does tachyon arise in bosonic string theory?

I am looking for precise mathematical and physical reasons which cause the presence of tachyon in bosonic string theory(specially closed bosonic string theory). Has it to do with the specific form of ...
2
votes
0answers
66 views

What is elliptic genera?

What is elliptic genera in physics? Reading many relevant papers, they just defined elliptic genus as sort of partition function. I try to find useful materials to explain it, but I couldn't find ...
2
votes
0answers
40 views

T duality for lower codimension branes or ALF spaces

These are purely mathematical questions in some sense but I believe this is relevant in string theory as the title says. I wonder if it is possible to perform T-duality of Taub-NUT space not along ...
2
votes
2answers
75 views

World-sheet energy-momentum tensor and OPE

On p43 of Polchinski's book, it says that under the world-sheet translation $\sigma^a\rightarrow\sigma^a+\epsilon v^a$, $X^\mu\rightarrow X^\mu-\epsilon v^a\partial_a X^\mu$. And $$j^a=iv^b T_{ab},$$ ...
2
votes
1answer
103 views

Operator product expansion in CFT

I'm on Polchinski's p39. Can someone please tell me the steps in the equivalence below? $$\exp\left[\frac{\alpha'}4\int d^2z_4 d^2z_5\ln|z_5-z_4|^2\frac{\delta}{\delta X^\mu(z_4,\bar ...