Wednesday, September 26, 2012

uncertainty and inflation

all fields associated with elementary particles fluctuate on the time scale $\Delta t$ by energies $\Delta E$ which can be estimated to be $>\hbar / \Delta t$ according to the uncertainty principle. Why isn't then the inflation field generating inflationary epochs every time (i.e. nowadays too!) if it acquires enough energy by statistical fluctuation?

Wednesday, September 19, 2012

planetary atmospheres

why don't planets lose their atmospheres to outer space? one would assume that the Boltzmann distribution would always allow a certain fraction of molecules to have kinetic energies large enough to overcome the gravitational potential.

bonus question: wouldn't the same thing apply to other gravitationally bound equilibrated systems such as open clusters, globular clusters and galaxies?

Wednesday, September 12, 2012

Copernican principle

what ways are there for testing the isotropy and homogeneity of the Universe on large scales? to what extend are those symmetry assumption tested and how would a violation impact on FLRW-models?

Wednesday, September 5, 2012

atmospheric pressure on Venus

the atmospheric pressure on the surface of Venus is almost 100 times larger than on Earth, despite the fact that the gravitational acceleration is 10% less. how is that possible?

bonus question: why is the pressure on Mars so low? (actual numbers are $p=6\times10^{-3}$ bar at a third of Earth's gravity)