## Wednesday, October 26, 2016

### spherical gravitational wave

is it possible to have a spherically symmetric gravitational wave around an object?

## Wednesday, October 19, 2016

### electricity and gravity

why is there a cosmological constant (even) in the classical Poisson-equation, $\Delta\Phi = 4\pi G\rho + \lambda$, but no such term in the wave-equation of electrodynamics, $\Box A^\mu = 4\pi\jmath^\mu$?

## Wednesday, October 12, 2016

### $CPT$ and relativity

with earlier CQWs and the idea that in relativity there's no fundamental difference between space and time coordinates (apart from the signature of the metric), could you formulate a combined $PT$-invariance of the field equation, where $\vec{x}\rightarrow-\vec{x}$ and $t\rightarrow-t$? what's the relation to charges of the gravitational field (i.e. masses) and a combined $CPT$-symmetry?

## Wednesday, October 5, 2016

### solutions to general relativity

is it possible to find a solution to Einstein's field equation for an arbitrary distribution of matter? in what way is the problem different from electrodynamics?