## Wednesday, December 4, 2013

### quantum microwave background

CQW celebrates its second anniversary!

would a classical description of the microwave background today be applicable? please justify your answer using the thermal wavelength.

bonus question: motion extremises the action in classical Lagrangian mechanics. is that extremum a maximum or a minimum?

## Wednesday, November 27, 2013

### classical photons

the flux density of a blackbody would have form

S(\omega) \propto \omega^3\exp\left(-\frac{\hbar\omega}{k_BT}\right)

if the photons were classical distinguishable particles. can you derive Wien's displacement law and the Stefan-Boltzmann law and point out the differences to the Planck-spectrum?

## Wednesday, November 20, 2013

can you express the density parameter $\Omega_\gamma$ of a Planck-distributed relativistic species as a function of temperature only?