# Questions tagged [string-theory]

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 linking diagrams in string theory like $SO(6)$?

https://youtu.be/5rB1YKjEwco (51:33) A toy model is presented but I want to know the name of this toy model as well as $\phi^4$ in QFT what is that called? What is it doing with the $SO(6)$ group?
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In Randall Sundrum (RS) model-type 1 : A Large Mass Hierarchy from a Small Extra Dimension, it’s mentioned that: This result contrasts sharply with the scenario of large extra dimensions for solving ...
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### Gauge invariance / charge conservation on string ending on brane

Consider a fundamental string charged under the Kalb-Ramond 2-form $B$ and ending on a D5-brane. Charge conservation implies the existence of a 1-form gauge field $A$ with field strength $F$ living on ...
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### Should I capitalize the term 'superstring revolution'? [closed]

I'm writing an essay in physics and will include the word 'superstring revolution'. There have been two superstring revolutions before. In my understanding, such revolutions changed people's views ...
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### Mathematical prerequisites for M-theory [duplicate]

I am interested in learning M-theory; however I have no Idea as to what mathematics is required for it. Are the prerequisites the same as string theory? Is there more mathematical knowledge needed for ...
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### String length $\gg$ Planck length?

The potential energy of a string $E_{pot}$ is given by $$E_{pot}=T \times L\tag{1}$$ where $T$ is the string tension and $L$ is the length of the string. The internal kinetic energy $E_{kin}$ of a ...
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### Neumann vs Dirichlet boundary conditions for vector fields

From hep-th/9611230, A vector field $A_\mu$ in $3 + 1$ dimensions may obey either Dirichlet boundary conditions, in which the components of $F_{\mu\nu}$ with $\mu$ and $\nu$ tangent to the boundary ...
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### Moduli space for Riemann surfaces with boundaries and open string loop diagrams

I'm searching for information on the moduli space for Riemann surfaces with boundaries, like the ones used to compute open string loop diagrams. I found a huge lot of info for the case without ...
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### Amount of SUSY preseved by branes

Consider 10d superstring theory, a D5 brane extended in the 012789 directions, and an NS5 brane extended in the 012345 directions. I have read that this configuration preserves 1/4 of the ...
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### What does cohomology of $Q_B$ mean in BRST quantization in Polchinski?

While proving no-ghost theorem ($4.4$ Polchinski) the term cohomology of $Q_B$ is used quite a lot of time. From what I understand this has to be a set since "cohomology of $Q_B$" is ...
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I have a question regarding an equation in the book "Gauge/Gravity Duality" by Martin Ammon and Johanna Erdmenger which however can also be found in other AdS/CFT books or lecture notes. The ...
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### How does commutator of $Q_B$ with change in $H$ results in moving around in gauge space

In ch-$4$ Polchinksi states following: In order to move around in space of gauge choices, the BRST charge must remain conserved. Thus it must commute with change in the Hamiltonian. Commutation with ...
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### About the use of static gauge in string theory

In the paragraph before equation (2.1.44) of GSW 1st Volume, 25th anniversary edition, it's said that after fix the choice of conformal gauge $h_{\alpha \beta} = \eta_{\alpha \beta}$, there still a ...
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### How do I understand this conformal transformation?

I am learning conformal transformation, and this is by far the most confusing transformation for me. For the 2D bc system $$S=\frac{1}{2\pi}\int d^2 z b\overline{\partial}c,$$ we have the ghost ...
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### How many different vacua really are there in the string theory landscape?

How many different vacua are there in the string theory landscape? Different sources give different estimates: some sources talk about the number $10^{500}$, others $10^{272\ 000}$, still others say ...
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### What does Polchinki mean when he says identifying under involution?

I am reading chapter 7 of Polchinki's String Theory vol. 1 textbook and I am trying to understand why one obtains the cylinder (annulus) from the torus by identifying points under involution. To be ...
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### Open-closed amplitude in bosonic string theory

I want to know the scattering amplitude involving both open and closed string, more specifically, the amplitude between two gluons and one graviton in open closed set up. Is there a reference where ...
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### To what degree have Calabi-Yau manifolds been shown to be all linked by conifold transitions?

Originally, the number of Calabi-Yau manifolds (these are special vacuum solutions of Einsteins GR) was estimated by Yau to be a small finite number, later he revised it to be a large finite number - ...
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### Polchinski OPE of spacetime translation current

I am trying to derive $$j^\mu(z):e^{ik\cdot X(0,0)}: \;\sim \frac{k^\mu}{2z}:e^{ik\cdot X(0,0)} \tag{2.3.14a}$$ from Polchinski's String Theory vol.1 equation (2.3.14a). using \$j^{\mu}=\frac{i}{\...