16
votes
1answer
351 views
+50

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 ...
3
votes
0answers
55 views
+50

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 ...
3
votes
1answer
108 views
+50

Deriving the Fierz-Pauli propagator

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 ...
1
vote
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 ...
-1
votes
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 ...
3
votes
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, $$\begin{equation} \langle \phi (z,\bar{z})\phi(\omega, \bar{\omega})\rangle ~=~ ...
6
votes
2answers
150 views
+100

Problem understanding the symmetry factor in a feynman diagram

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 $\phi^4$ ...
3
votes
1answer
62 views
+50

Blackbody cavity relationship between energy of oscillators and EM radiation

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 ...