Quantum gravity in the sky
  Quantum gravity is known to be mostly a kind of metaphysical speculation. In this brief essay, we try to argue that, although still extremely difficult to reach, observational signatures can in fact be expected. The early universe is an invaluable laboratory to probe "Planck scale physics". With the example of Loop Quantum Gravity, we detail some expected features. 
Aurelien Barrau, Julien Grain
gr-qc astro-ph.CO hep-th physics.hist-ph