# All Questions

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### Why do we need complex representations in Grand Unified Theories?

EDIT4: I think I was now able to track down where this dogma originally came from. Howard Georgi wrote in TOWARDS A GRAND UNIFIED THEORY OF FLAVOR There is a deeper reason to require ...
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### A question about genus one string amplitude

In BCOV's paper http://arxiv.org/abs/hep-th/9309140 the genus one string amplitude of a Calabi-Yau 3-fold was explained in the B-model as the Ray-Singer torsion (there is a similar discussion in the ...
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Fierz-Pauli action can be written as $$S = \int d^Dx \; \frac{1}{2} h_{\mu \nu} \mathcal{O}^{\mu \nu, \alpha \beta}h_{\alpha \beta}$$ where the operator $$\mathcal{O}^{\mu \nu} {}_{\alpha ... 1answer 34 views +50 ### What really happen with resonance inductive coupling I can't figure out the picture of resonance inductive coupling I can image how magnetic inductive coupling works, It scatter magnetic around one coil and if second coil being near it then induce ... 3answers 191 views +50 ### Double-double-slit with entangled photons Edited question to face complaints about ambiguity Following experimental setup. Bob uses a nonlinear crystal to create two entangled photons A and B. Consider a standard pair of EPR-entangled ... 0answers 83 views +50 ### Vertex operator and normal ordering The two point function, or propagator for a free massless boson, \phi in 2 dimensions is given by,$$ \langle \phi (z,\bar{z})\phi(\omega, \bar{\omega})\rangle ~=~ ...
I am trying to understand a $1/2$ in the symmetry factor of the "cactus" diagram that appears in the bottom of page 92 In Peskin's book. This is the diagram in question (notice that we are in $\phi^4$ ...
This question is based on Planck's view of blackbody radiation in a cavity. Here is a quote from here: ...where $\langle E \rangle$ is the average energy of the oscillators present on the walls of ...