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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How can extra (non-curled up) dimensions be hidden from us?

Wikipedia says: If extra dimensions exist, they must be hidden from us by some physical mechanism. One well-studied possibility is that the extra dimensions may be "curled up" at such tiny ...
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Why don't external sources change how a string vibrates?

If the vibrations of strings give rise to everything in our perceived reality why don't everyday vibrations cause the strings to "change their tune" and thus the matter/forces they bring about? What ...
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42 views

Compactified extra dimensions and symmetry

It's my understanding that M-Theory necessitates 11 space-time dimensions (10 spatial dimensions plus 1 time dimension) in order work mathematically. This appears to jar with reality, which only ...
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29 views

The limited Computing Capabilities of Space, Increased quantized info leads to time-dilation?

Are there any approaches to Special and General Relativity using space as a computing medium? With space having a maximum computing capability and time dilation as lag? Could this idea describe the ...
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277 views

Does the need for renormalization in QFT vanish once you use a more fundamental theory (e.g., string theory)?

It is often explained that renormalization arises in QFT because QFT is a low-energy effective theory that needs to be replaced by a more fundamental theory at higher energies/smaller distances. While ...
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24 views

SUSY preserved by an extended D-brane

There's a nice way to prove that for an extended D-brane half of SUSY is preserved, from perturbative string argument with SUSY Ward identities and the doubling trick (at least, at tree-level and ...
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Tadpole-free condition

Tadpole-free is a very important condition for perturbative string theory (which is equivalent to the theory to be expanded around the "right" vacuum). For simplicity, let's consider closed string ...
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18 views

What information do quiver gauge diagrams provide?

I am struggling to understand what the information one can extract by looking a quiver diagram for a quiver gauge theory is. I understand what quivers are but I cannot get some physical intuition and ...
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19 views

T-Duality for closed bosonic string: what is the difference between a graviphoton and a B-vector?

Consider the closed bosonic string in 26 dimensions, of which one physical dimension, say $X^{24}$ is compactified into a circle of radius $R$. The lowest lying massless states are the graviton, the ...
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58 views

What exactly does it mean to wrap a D-brane or a M-brane in a Riemann surface $\Sigma_g$?

What exactly does it mean to wrap a D-brane or an M-brane in a Riemann surface $\Sigma_g$ ($g$ is the genous)? Is there some mathematical statement? And why do we get various supersymmetric gauge ...
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64 views

Why string theorist use the following result? [duplicate]

$1+2+3.......$so on $ = -1/12.$ I have seen a few proofs of this result. And I hope most of you are familiar with them. Why string theorist use this ambiguous result in string theory, when assigning ...
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1answer
31 views

What exactly are the ADE type of gauge theories?

What exactly are the ADE type of (susy) gauge theories? What exactly we mean, intuitively, the ADE singularities? What are their relation to brane constructions and do you have any references one ...
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129 views

Why M-theory has only M2 and M5 branes?

Why M-theory has only M2 and M5 branes? In string theory, depending on the type one considers, you get all kind of D-branes. What is so special in M-theory that only allows 2 and 5 branes?
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1answer
26 views

Branes on a tip of a conifold; how to understand it?

I am not sure if this question makes sense "intuitively" but here it is. In Klebanov-Witten theory one puts branes on the tip of a cone over a Calabi-Yau manifold. My question is what does it mean to ...
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1answer
98 views

States in light cone string theory

Currently I'm trying to understand string theory in the light cone quantization. I just have had a look into Polchinski (Vol. 1, Introduction to the bosonic string), because – as far as I could see – ...
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29 views

Is the $\alpha'$ expansion in string theory an asymptotic expansion?

The low-energy bosonic effective actions of string theory lead to Einstein-Hilbert gravity, along with scalars and $p$-form Maxwell fields. For example, the action for type IIA string theory is $S = ...
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1answer
20 views

What does it mean the term “probe brane”?

What does it exactly mean the term "probe brane"? People say for example: We put a stack of N branes at some point and then a probe brane ..." How do they appear in AdS/CFT? Can you give me an ...
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1answer
42 views

How is a string different from a harmonic oscillator or a point?

I am reading String Theory and M-Theory: A Modern Introduction by Becker, Becker and Schwartz. I've tried to read this book before but not succeeded because I didn't know enough math or physics. This ...
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2answers
80 views

If a theory gets two predictions right, how likely it is that the rest of the predictions are true too? [closed]

The question lucidly defines what I am trying to inquire, so there is no need to elucidate it any further. Another question would be, General/Special Relativity has gotten some predictions right as ...
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46 views

What does string theory and loop quantum gravity say about the Planck Epoch and anything before the Big Bang?

General Relativity is known to commit suicide exuberantly at the planck epoch, and is unable to say anything further, whereas string theory and loop quantum gravity breathe well under these ...
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38 views

Lorentz violation in String theory

First of all, why are there so many researches to find Lorentz violation? Are there some models of (super-)string theory that include Lorentz violation at some scale?
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1answer
41 views

Extended SuSy from the kappa-Symmetry WZW terms

In José de Azcárraga, Jerome Gauntlett, J.M. Izquierdo, Paul Townsend, Topological Extensions of the Supersymmetry Algebra for Extended Objects, Phys.Rev.Lett. 63 (1989) 2443 (spire) it was ...
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36 views

Supergravity prerequisites for branes in string theory [duplicate]

I have a one-semester background in string theory (bosonic string theory, the NSR string, conformal field theory), but I have not taken any full length courses on supersymmetry and supergravity. I'm ...
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26 views

Available material on Giant Gravitons

I am looking for a pedagogical introduction to giant gravitons (if one exists!). I have basic string theory/SUSY knowledge but no introduction to AdS/CFT. (Do I need to do some reading on AdS/CFT ...
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230 views

Noether currents in QFT

I am trying to organize my knowledge of Noether's theorem in QFT. There are several questions I would like to have an answer to. In classical field theory, Noether's theorem states that for each ...
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1answer
44 views

Invariance of the low energy effective string action

It is well known that the action of General Relativity $$S = \frac{1}{16\pi G}\int R\;\sqrt{-g} d^D X$$ is invariant under "diffeomorphisms". The low energy effective action for bosonic strings is ...
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Conserved charge of a conformal transformation

From Becker, Becker and Schwarz String Theory and M-Theory: For the infinitesimal conformal transformation $$\tag{3.25}\delta z=\varepsilon(z)\quad\text{and}\quad \delta\bar ...
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1answer
84 views

Theories that predict the number of space-time dimensions

My impression in that most theories assume three spatial dimensions and one temporal dimension, though could in principle be formulated in others numbers of dimensions without inconsistencies. I know, ...
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1answer
86 views

Is it worth reading The Elegant Universe? [closed]

noob question here. I'm interested in reading The Elegant Universe by Brian Greene, but I've read some reviews that say the science has been discredited. I'm a total layman, has the science been ...
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33 views

Algebraic number theory and physics [duplicate]

I would like to ask if there are any aspects of algebraic number theory related to physics (for example in string theory or Moonshine etc). I am thinking of attending a course on algebraic number ...
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3answers
633 views

Are quantum mechanics and general relativity predictions of string theory, or were they built into the theory from the start?

Are quantum mechanics and general relativity predictions of string theory, or were they built into the theory from the start? If the former, why aren't tests of GR and QM considered simultaneous tests ...
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34 views

Kappa symmetry and degrees of freedom in Green Schwarz

For $N=2$ Green Schwarz superstring, the $\kappa$-symmetry parameter is $\kappa^{A\alpha}$. So there are two of them (one for each $N$), and each is a world sheet vector AND a target space spinor. The ...
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Vertex insertions as functionals

In lecture notes on string theory by David Tong (available for free here http://www.damtp.cam.ac.uk/user/tong/string.html) a brief explanation of the vertex operator for tachyon is given. The main ...
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52 views

Why holographic renormalization?

Why is there a need to perform holographic renormalization for the normal $AdS_5\times S^5$/CFT$_4$ correspondence if the brane theory is conformal? Since the flow along the AdS direction $r$ is ...
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2answers
82 views

Why does AdS/CFT with non-zero temperature correspond to a black hole in the bulk?

Is there a good intuitive explanation on why AdS/CFT with non-zero temperature corresponds to a black hole in the bulk? And what is the role of temperature and chemical potential in this black hole?
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36 views

Brane polarisation (Myers Effect/Polchinski-Strassler/KPV)

I have a question about brane polarisation. In the most famous cases I know of--the original giant D2 brane of Myers, the Polchinski-Strassler resolution of the $\mathcal{N}=1^*$ IR singularity, and ...
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1answer
42 views

AdS/CFT in global coordinates (as opposed to Poincare coordinates)

When the usual derivation for AdS/CFT is given for the most famous example of Type IIB string theory on $AdS_5 \times S^5$, the AdS space is clearly seen as the near horizon geometry of a stack of D3 ...
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54 views

Coulomb Branch vs. Higgs Branch (and the connection with D-branes, AdS/CFT)

I am confused about the difference between the Coulomb and Higgs branches of the moduli space of supersymmetric gauge theories. It's easy to find a definition for $D=4$, $\mathcal{N}=2$ supersymmetric ...
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37 views

Where can I find a video on Liouville Non-Critical String Path Integral?

Would anybody know of a video lecture course in which Polyakov's non-critical string path integral $$Z = \int D [\psi(\xi)]\, \, \exp \left\{ \frac{D-26}{48 ...
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Questions regarding $D=4 $ ${\cal N}=4$ supersymmetric Yang-Mills

I have some questions regarding the $D=4 $ ${\cal N}=4$ super-Yang-Mills theory (the one with a really long action which can be acquired by compactifying the 10-dimensional ${\cal N}=1$ theory). I ...
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1answer
35 views

Why does Weyl invariance imply a traceless energy-momentum tensor?

I've begun to self-study String Theory from Polchinski and Becker, Becker and Schwarz. I don't see why the fact that the Polyakov action is invariant under Weyl transformations is related to the ...
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2answers
66 views

Definition of Duality (opposed to Symmetry)

I'm learning basic string theory right now and we came across T-duality which was presented as a symmetry of the formula for the mass of a string in the context of compactification. There was a remark ...
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Modular S matrix in 2D rational conformal field theory

The modular $S$ matrix in 2D CFT is defined by $$ \chi_a(-\frac{1}{\tau})=S_{ab} \chi_b(\tau). $$ Can $S$ depend on the modular parameter $\tau$?
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how to measure the wave emitted from some particles after input sine wave into the particle

which waves can be input into the particle? is it sine wave? is the wave emitted from the particle after input wave into the particle different? if want to measure the output wave, how to use math ...
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1answer
43 views

Are end points of an open bosonic strings orthogonal to D-branes?

I'm apologizing for such simple question, I just started to learn string theory. If one end of an open bosonic string is attached to a Dp-brane it means that in directions normal to the brane ...
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113 views

How do we know there are dimensions above the third?

Excluding the interpretation of time being the forth dimension, what mathematical evidence is there that suggests it exists? When talking about string theory they say how there is 12 dimensions and I ...
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What's the string size cutoff?

The instantaneous string size is infinite Susskind say that the string's instantaneous size is infinite. its peak-to-mean amplitude and distance between endpoints is the harmonic series. it's ...
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1answer
48 views

Generalized spin connection and dreibein in higher spin gravity

I am studying 3D higher spin gravity and I would like to know the mathematical and physical meaning of generalized spin connection and generalized dreibein that appear in this theory. It is well known ...
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1answer
27 views

In Rational Gaussian Model, why must $R^2$ be rational?

I am reading Fusion Rules and Modular Transformations in 2D Conformal Field Theory and Verlinde talks about the rational gaussian model. The simplest class of RCFT's are the rational gaussian ...
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67 views

What is the motivation behind the GSO projection in superstring theory?

I do agree that the GSO "works", making the number of degrees of freedom match on the bosonic and fermionic side and that it sweeps away the problematic tachyon. However it is very artificial, it ...