# Tag Info

### Is Norton's dome valid (or does $\frac{d^2 \vec{p}}{dt^2} = \vec{0} \implies \frac{d^n \vec{p}}{dt^n} = \vec{0} \ \forall \ n > 2$)?

Your example is not analogous to Norton's dome. Norton's point is that Newtonian mechanics says that the trajectory of a particle obeys $\ddot{x}(t) = F(x(t),\dot{x}(t), t)$ at every point in time $t$,...
• 107k

### Permanent magnets - why spontaneous symmetry breaking?

First I will write some general remarks about spontaneous appearance of orientation. After that I go to the question specifically. Take the following demonstration: Take a large plate, in the middle ...
• 15.4k
Accepted

### What were the $r$ and $n$ of $\theta$s (Polchinski String theory section 8.6 page 265)?

The numbers $r_i\in\mathbb{N}$ are the degeneracies/multiplicies of the eigenvalues $\theta_i$ of the diagonal background gauge field $A_{25}$ in the compactified 25th direction  A_{25}~=~-\frac{1}{...
• 170k
1 vote

### Nonlinear symmetry realization: what is it for and caveats?

• 1,718

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