# Questions tagged [duality]

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### Regarding a possible duality between (2+1)D gravity and Chern-Simons Theory

Is there a duality between (2+1)D gravity and Chern-Simons Theory? Or they merely have related features? If so, of which type and why? Thanks!
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### Dualities in Physics and Fourier Transforms

In many articles, authors compare physical dualities to Fourier transforms. For example: Joseph Polchinski, in his article "String Duality" (hep-th/9607050v2), writes: "Weak/strong ...
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### At what coordinate is the D-brane located in the T dual world?

I have a simple question on the geometrical intuition of D branes. I am currently reading the TASI notes by Polchinski. Say one has a bosonic open string with all Neumann boundary conditions and ...
1answer
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### What is $\mu_5$ in string theory?

I have come across the quantity $\mu_5$ in string theory quite a lot but I have not found it explicitly defined anywhere. The bosonic worldvolume action reads  \begin{equation} S = \frac{\mu_5}{g_s}...
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### $T$-duality in effective gauge theories of a $D(p+1)$-brane

I am considering a $D(p+1)$-brane in a space $\mathbb R^{1,p}\times S_R^1$ where $S_R^1$ is the circle of radius $R$. I am assuming low energies $ER\ll1$, so that only the massless spectrum of the ...
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### Does there exist a duality between the following two quantum systems?

Consider two systems: A) $N$ number of independent spin $0$ bosons living on a circle. B) A single spin $0$ boson moving on an $N$-torus. How do we detect the difference between the two systems ...
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1answer
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### Complementary channel of convex combination of channels

Consider two channels $N_1$ and $N_2$ which have Kraus operators $\{A_k\}$ and $\{B_k\}$ respectively, where the index $k$ runs over the number of Kraus operators. Define a third channel $N$ as a ...
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### Is there any GENERAL symmetry behind holography and dualities?

Holography tells that a theory with gravity in D-dimensions is equivalent to a field theory in D-1 on the boundary. Similarly, after the second string revolution, we know there are symmetries called ...
2answers
326 views

### Energy momentum tensor of EM field written in symmetric form

I'm reading A. Zee's book, Einstein Gravity in a Nutshell. In problem 7 of chapter IV.2, it is said that the energy momentum tensor of the electromagnetic field \begin{align} T^{\mu\nu}=\eta_{\lambda\...