Questions tagged [string-field-theory]

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Topological M-theory as a quantum theory of non-abelian self-dual gerbes? [closed]

Hey guys I will try to give a construction of a field theory of non-abelian gerbes. What do you think about the approach?
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Does a smooth world sheet imply strings moving faster than light?

In string theory, one wants to study the interaction of strings throughout time. The interacting strings sweep out a surface in Minkowski space. To write down an action for the string, we need to ...
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The different frameworks around the string

I am studying string theory and I realize that the relations between the different frameworks are not clear to me. Following this question, one could repeat the discussion but now taking $p=1$. We get ...
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3 answers
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How is spacetime curvature generated in string field theory?

In String Theory, the graviton originates from a mode of vibration of the fundamental strings and spacetime curvature itself is somehow generated by the strings themselves. In String Field Theory, ...
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Calculation of effective action in Einstein frame

I want to do the calculation for the effective action in Einstein frame (see Tong's lecture notes Chapter 7.3), this action in string frame is given by \begin{align}\label{exp1} S=\frac{1}{2 \kappa_{0}...
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1 answer
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Degree of a multilinear product in string field theory

I am going through the paper $L_{\infty}\textit{ Algebras and Field Theory, O. Hohm and B. Zwiebach (2017) }$ (https://arxiv.org/abs/1701.08824) and I cannot for the life of me figure out how and why ...
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3 answers
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Where do virtual particles come from?

Do I understand correctly that for the existence of virtual particles, a single physical object is needed - a quantum field? And virtual particles are excitations of this field that fills all space. ...
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Why string amplitude could be computed by path integral of string field theory?

I am trying to understand BCOV's paper: Kodaira-Spencer theory of gravity and exact results for quantum string amplitudes. In this paper, it was shown that the higher genus string amplitude for B-...
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What is the string equivalent of the Feynman Propagator?

The Feynman propagator for a massless point particle is proportional to: $$\Delta(x-y;t_1-t_2)=\frac{1}{|x-y|^2-(t_1-t_2)^2}$$ which is, formerly, the Fourier transform of $\dfrac{1}{|k|^2-E^2}$. For ...
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Equivalents definitions of string field

One can define the Tachyon field in SFT via State-Operator correspondence by $\Phi(0)|0\rangle = c(0)e^{ikX(0)}|0\rangle = c_1|0;k\rangle$ with $|0;k\rangle = e^{ikX(0)}|0\rangle$. I'm trying to ...
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Level of String Fields

I know that the Tachyon state $c_1|0;k\rangle$, where $|0;k\rangle = e^{ikX}|0\rangle$, has eigenvalue $-1$ under $L_0$ operator. Using $L_0 = \alpha'p^2 + \sum_{n\ge1}\alpha_{-n}\cdot \alpha_n$ it is ...
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Chern-Simons (CS) theory

I have a question about Constructuion of Chern-Simon Action. In its paper "Non-commutative geometry and string field theory", Witten construct the Action of the String Field Theory inspiring ...
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Are there applications for the cancellation of one-loop divengeces in $SO(8192)$ bosonic string theory?

I recently read in Polchinski's textbook on string theory (Volume one, page 229) that an orientifold of the 26-dimensional bosonic string can be considered. Investigating further, I found that after ...
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2 votes
1 answer
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String quantum cosmology

In canonical quantum gravity we have Wheeler–DeWitt equation and we can chose homogeneous and isotropic ansatz (it kills many problems) to describe quantum universe. In string theory, as I understand,...
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Level truncation in String Field Theory

In string field theory, to study tachyon condensation at level-2, the string field is truncated to $$\Psi=t c_{1}|0\rangle+ u c_{-1}|0\rangle+ v L_{-2}^{(m)} c_{1}|0\rangle,$$ where $t,u, v$ are ...
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Tachyon mode in Brane-Antibrane system (Type II)

Lets First start with coincident $D3$ brane- $D3$ Brane system. Superstring stretch between these two contain a Tachyon mode But GSO projection removes this. For open string, $D$ branes serve just as ...
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String topology in string theory

How do string topology, string field theory and topological strings interact? Does anybody see a global picture? By string topology I mean the TQFT based on the homology of the space of loops ...
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Classical field theory with fields on different base spaces

Keeping things at a "basic level", a field is a function from a base manifold (of dimension D) to some other space. Usually the base manifold is the spacetime but may be something different (a lattice,...
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Does string theory violate general covariance?

In a 2007 note on ArXiv, it said: String theory unifies all interaction but provides a perturbative background dependent formulation which violates general covariance. However, another 2012 paper ...
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Could every particle encode the distances to all other particles?

I was thinking about quantum gravity and pre-geometry and wondering this question: "If space does not exist. How does a particle know how far away it is from another particle?" i.e. there are no ...
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1 answer
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How can you show diffeomorphism invariance of closed string field theory?

String Field theory if it predicts General Relativity should have 26D space-time diffeomorphism invariance (presumably). How can one show that Closed String Field Theory has this symmetry? (Besides ...
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How do strings (in string theory) get created or destroyed?

Something has been bothering me about string theory. From what I can tell, string theory is a first quantized theory of the position and momenta along a string, and that the fields of QFT are not ...
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Is it true the Michio Kaku has completed a unified field theory started by Einstein by making use of string theory? [duplicate]

This professor has a few documentaries available explaining science to the layman like myself and he showed an equation no longer then a sentence that he says unifies all the know forces and particles ...
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10 votes
1 answer
975 views

Is the String Field of String Field Theory the same (ontologically identical to) as the field of QFT?

Disclaimer: Although my maths is quite good and I have a background in computer science and software engineering, I am a philosopher specialising in information theory (and what is called the ...
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Do Aichelburg-Sexl spacetime give excitation to a string?

I read about an article stating the excitation of a charged string passing through a shockwave in the Aichelburg-Sexl spacetime, how does it excites the string?
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Witten's Open String Field Theory vs. Light Cone Quantization?

I am a quite confused on the differences between these two formulations of open string field theory, and am unable to reconcile how they are related. M. Kaku's 1972 paper formulates a string field ...
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5 votes
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Flux compactifications and the scalar potential

Does the scalar potential: $$V=e^K(K^{I \bar{J}})D_IW D_{\bar{J}}\bar{W}-3|W|^2$$ where $K$ is the Kähler potential and $W$ the superpotential, $D=\partial_I+\partial_IK$ and $I$ runs over all the ...
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Where is a proof that string field theory is generally covariant?

Given a space-time coordinate of a string $X^\mu(\sigma)$ dependent on the position $\sigma$ around the string. And a string field functional $\Phi[X]$, is there a proof that the equations of motion (...
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2 votes
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What is the "single equation" in string theory that's an inch long? [duplicate]

Michio Kaku, famous theoretical physicist claims to be one of the founders of string field theory and to have contributed a equation that's "no bigger than your thumb" that ties general relativity and ...
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4 votes
1 answer
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What is Kaku's equation about?

When Michio Kaku talks about science he often likes to refer to string theory and sometimes to his equation which looks like this (not sure if wrote right): $$L = \Phi^\dagger[i\partial_{\tau}-H]\Phi +...
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Brane interactions?

In particle physics, in QFT's, interactions come from the interaction piece in the Lagrangian (action). In string theory, waiting for a complete formulation of SFT, we have to add "by hand" ...
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Review of String Field Theory

Could anybody suggest the comprehensive review of String Field Theory? Original papers are lengthy and it would take quite a long time to read them all.
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String Field Theory and AdS/CFT

I am a PhD student and I am choosing the topic to work on in the graduate school. I am interested in various non-perturbative aspects of String Theory. Does anybody know if there were any attempts to ...
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7 votes
1 answer
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Has Sen quantized superstring fields?

Today I saw a paper by Ashoke Sen titled "BV Master Action for Heterotic and Type II String Field Theories". Is it really the "quantization" of superstring fields for the first time? What can be its ...
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3 votes
1 answer
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What is meant by the following divergent formula?

I have encountered the following formula a couple of times (in different physics contexts which I do not have a good understanding of) $$\int_{0}^\infty \frac{dt}{t}e^{-tx}=-\log x$$ Formally one ...
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2 votes
1 answer
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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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3 answers
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What is the general theory that describes the interactions between strings?

What is the general theory that describes the interactions between strings? I mean the basic object in the theory is (closed) string and they have interactions among them. The string theory, as I ...
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8 votes
1 answer
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Why do people look for a field formalism for String Theory

String theory was originally formulated from a perturbative description (using quantum mechanics (QM) and replacing points by strings and evaluating path integral). Still, although QM has an upgrade ...
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7 votes
0 answers
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Why is it difficult to construct the Ramond-Ramond sector in Berkovits' SFT?

I've been trying to get familiar with string field theory (SFT) and I've stumbled upon the statement that the Ramond-Ramond (RR) sector of Nathan's SFT has not been constructed yet. Why is that?
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4 votes
2 answers
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A three string tree diagram evaluated in CFT is different from string field theory evaluation

Hi Guys generally when you evaluate the 3 open string tachyon tree level amplitude in CFT, you do a conformal transformation mapping the worldsheet to the upper half of the complex plane and the ...
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45 votes
9 answers
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What are the strings in string theory made of?

This is a follow-up to an intriguing question last year about tension in string theory. What are the strings in string theory composed of? I am serious. Strings made of matter are complex objects ...
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3 votes
1 answer
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How to deal with crossing duality and modular invariance in string field theory?

An answer I gave elsewhere. Some cases to ponder over. A closed string splits into two closed strings, which then merge again into a single closed string. The overall string worldsheet has the ...
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4 votes
1 answer
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Why do strings split in string theory?

In string theory, we are told strings can split and merge if the string coupling is nonzero, even while the worldsheet action remains Nambu-Goto or Polyakov plus a topological term. However, a ...
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10 votes
3 answers
2k views

Is String Theory a Field Theory?

Is String Theory a Field or Quantum Mechanical Theory of the String rather than a Particle? I should know this having studied this for a term, but we jumped into the deep end, without really ...
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9 votes
1 answer
400 views

Is there a background independent closed string field theory?

Analogous to the background independent open string field theory by Witten. If there isn't, what are the main stumbling blocks preventing its construction?
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17 votes
1 answer
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Is string theory local?

By locality I mean something like the Atiyah-Segal axioms for Riemannian cobordisms (see e.g. http://ncatlab.org/nlab/show/FQFT). I.e. to any (spacelike) hypersurface in the target we associate a ...
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12 votes
2 answers
2k views

What does second quantization mean in the context of string theory?

String field theory (in which string theory undergoes "second quantization") seems to reside in the backwaters of discussions of string theory. What does second quantization mean in the context of a ...
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