Wednesday, February 24, 2016

speed of light and speed of gravity

can you explain why electromagnetic and gravitational waves travel at the same speed?

Wednesday, February 17, 2016

negative cosmological constant

could $\Lambda$ be negative? what consequences would that have for the evolution of FLRW-universes and would it be conceivable from a theoretical point of view?

Wednesday, February 10, 2016

curved or straight?

please list as many experiments as possible that would allow you to distinguish between curvature and dark energy with an equation of state of $w=-1/3$.

Wednesday, February 3, 2016

correlation function

can you show that the integral $\int\mathrm{d}^nx\:C(r)$ of the correlation function $C(r)$ as a function of distance $r$, $r^2=\sum_{i=1}^n x_i^2$, of a random field in $n$ dimensions vanishes?