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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130 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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59 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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35 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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288 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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94 views

Deriving the critical dimension of bosonic string theory

I am going through the lecture note by Gleb Arutyunov on the derivation of critical dimension for bosonic string theory. I was able to reproduce all the results till the last step given on page 62. ...
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427 views

Is Electromagnetic Mass Possible?

If the sinusoidal electric component of a light wave were off-set to one side of the magnetic component and then the smaller "lobe" were to cancel out with much of the larger side, then where would ...
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48 views

boundary conditions Faddeev-Popov ghosts bosonic string

I have a question concerning the Faddeev-Popov ghost boundary conditions in the path integral quantization of bosonic strings. My ghost action is: $S_g= - \frac{i}{2\pi} \int d^2 \xi \sqrt{-h} \; ...
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50 views

Powercounting in String Frame?

if I consider the low energy effective action of type IIB string theory in the string frame, i.e. with an $e^\phi$ prefactor, is it possible to do standard powercounting with this action? I.e. how do ...
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332 views

Tree level and loop level

I'm trying to read through a paper which explains the following about Universal Extra Dimensions (UED) vs ADD models: The new feature of the UED scenario compared to the brane world is that ...
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68 views

About the duality when embedding Gopakumar-Vafa into superstring theory

Vafa proposed a duality when embedding the Gopakumar-Vafa duality into superstring theory. Vafa's duality is about a correspondence N=1 supersymmetric gauge theory and superstring propagating on ...
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66 views

About deriving the multi-trace index in terms of the single-trace index

This question is in reference to this paper Combining their equations 5.2, 5.3, 5.6 and 5.7 one seems to be looking at the integral/partition function, $Z(x) = \prod_{n=1}^{n =\infty}\left [ \int ...
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84 views

Construction of the supergravity side explicitly in gauge/gravity dualities

Although the motivation of this question comes from the AdS/CFT correspondence, it actually is related to a more general principle of gauge/gravity duality. We know from Maldacena's conjecture that a ...
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118 views

Holonomy twisting

There is Witten's topological twist of standard SUSY QFTs with enough SUSY into Witten-type TQFTs. What is a holonomy twist?
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56 views

Standard Quantum Mechanics representation as a constrained 2 + 1 space-time (membrane) theory?

Could a particular Standard Quantum Mechanics representation be a constrained 2 + 1 space-time theory (membrane theory) ? (i) This question is motivated by a possible (approximative) analogy with ...
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173 views

Our Universe in collision with another one

This question is related to the possibility that there are many other universes in the UNIVERSE,the multiverse, that were created during collisions between membranes, according to string theories. The ...
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72 views

Expectation of 2-form field $B_{MN}$ in string theory

In the context of string theory, in particular when we are dealing with a low energy effective action, if we have an effective action of the form, $$S_{\mathrm{eff}} \sim S^{(0)} + \alpha S^{(1)} + ...
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92 views

M-Theory: Are the branes still colliding and matter is being produced into our universe?

In M-Theory membranes are rippling in the 11th dimension and when they collided the bing bang happened and the ripples produced matter, is it still happening and matter is still being produced? ...
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117 views

Can decompactification explain the inflation of the early universe?

I've just reread chapter 11 of this book where it is explained among other things, that our four dimensional universe could be unstable concerning a decompactification transition, since potential ...
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105 views

Superstring theory and renormalization [duplicate]

Possible Duplicate: Does the renormalization group apply to string theory? Renormalization in string theory QED and some quantum theories require renormalization techniques and take it as ...
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0answers
115 views

Is it really true that slow-roll inflation is incompatible with string theory?

In this blog post, Motl claimed that slow-roll inflation is incompatible with string theory. Is that really true, and why do people think so?
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219 views

Derivation of the supergravity action in 11D

The Einstein-Hilbert action of general relativity is uniquely determined by general covariance and the requirement that only second derivatives in the metric appear. Yang-Mills theory can be motivated ...
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107 views

Non-locality from quantum loops

I am reading a paper on quantum gravity (written circa 1988 but I don't think it's relevant to give a more precise reference) where I read the following statement: "universe loops will in general ...
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86 views

Why/When can the gauge superfield and/or chiral superfield kinetic term in $(2,2)$ SUSY be ignored?

This is in reference to the argument given towards the end of page $61$ of this review paper. There for the path-integral argument to work the author clearly needed some argument to be able to ignore ...
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59 views

Spectrum of Free Strings [duplicate]

Possible Duplicate: Spectrum of Free Strings As far as I understand, both in bosonic and superstring theory one considers initially a free string propagating through D-dimensional ...
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95 views

CFT on a torus and diagonal modular invariants

Suppose we have a CFT which is sigma model with a torus target $T^2$ at a rational value of the moduli. Does it always give rise to a diagonal modular invariant?
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158 views

Picture changing operators

What is a picture-changing operator in string theory? How do they work?
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319 views

Static gauge choice in string theory

In solving different problems in string theory and also in brane theory, we consider this static gauge choice and I think that's due to the local symmetry(Repara. Inv. and Weyl) that we have in our ...
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223 views

Singularities in Bianchi models in general relativity ( physical science)

what are the conditions to check point type singularity in a bianchi type model ? bianchi type model are of Type I,II,III,IX,IV or u can say we use different Bianchi type models having some specific ...
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1answer
84 views

How can a string be unidimensional if they can be open ended or close ended?

I just don't understand how a object with 2 ends can be unidimensional.
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1answer
155 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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2answers
431 views

How exactly do superstrings reduce the number of dimensions in bosonic string theory from 26 to 10 and remove the tachyons?

In bosonic string theory, to obtain the photon as the first excited state, the ground state must have a negative mass (tachyon). By applying $1 + 2 + 3 + \cdots = -1/12$, it can be shown (in a ...
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2answers
394 views

What Observations could undeniably support string theory?

What experiments could provide observable "stringy" effects. All valid experiments are acceptable (also theoretical experiments).
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3answers
15k views

Total number of subatomic particles in the universe. Are they finite ? assuming any of GR or QM or even ST

Total number of subatomic particles in the universe. Are they finite ? assuming any of GR or QM or even ST.
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1answer
318 views

Are string theories gauge theories?

The wikipedia page for String Theory lists SO(32) and E8×E8 as group symmetries of some of the string theory types, and the page on E8 says: E8×E8 is the gauge group of one of the two types of ...
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2answers
268 views

Imaginary time and string theory

Is imaginary time an extra dimension? In other words, are time and imaginary time considered two separate dimensions? If so, does imaginary time appear (as a separate dimension) in string theory (thus ...
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1answer
892 views

Branes Collision -> Big Bang

Imagine universe occurred when two parallel branes collided, Momentum of Branes converted to big bang kinetic energy after Collision. Thus, high-energy quanta are high-Vibrating strings. what ...
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1answer
103 views

Geodesic curvature and Weyl transformations

The geodesic curvature is given by $$k=\pm t^a n_b\nabla_a t^b,$$ where $t^a$ is a unit vector tangent to the boundary of the string worldsheet and $n_a$ is an outward vector orthogonal to $t^a$. I ...
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1answer
180 views

About solitons, what is the difference between kinks and vortices?

I am reading papers about solitons for my small reports, and i could not understand its physical meaning in detail. I know soliton is solitary wave which behaves like particle. And many text they ...
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1answer
228 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
93 views

Entropy of Black Hole

What is the relation between the entropy of rotating and non rotating Black hole? Which one's entropy is greater?
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1answer
288 views

Would someone who is only interested in string theory benefit from working out the problems in Jackson electrodynamics?

This is a soft question. I'm not sure if it is appropriate for this site. Would someone who is only interested in string theory benefit from working out the problems in Jackson electrodynamics? I ...
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1answer
417 views

How is the operation of a Goldleaf Electroscope explained in terms of virtual particles?

If an electroscope is charged negatively the electrons on the leaves will repell each other and stand apart. It is clear than there is a steady force between the leaves that counters gravity. How is ...
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3answers
56 views

How do you define a “universe” (in the context of multiverse)?

How do you define a universe (in the context of multiverse)? The traditional definition of universe is something like "The Universe is all of spacetime and everything that exists therein". But in ...
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1answer
62 views

What are the two dimensions of relativity that are added to string theory?

Based on the Ramanujam's modular functions, somehow these magic numbers 10 and 26 spacetime dimensions appear in string theory. The dimensions can be viewed as 8 + 2 and 24 + 2. The number 2 is added ...
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1answer
71 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 ...
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1answer
61 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 ...
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1answer
89 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 ...
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1answer
64 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 ...
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1answer
105 views

Canonical partner of time in QFT and string theory

In analytical mechanics, the Hamiltonian or total energy becomes the conjugate momentum of the time in the symmetric form of the equations. This seems very strange and interesting to me. Does it have ...