A number of background independent quantizations procedures have recently been employed in 4d nonperturbative quantum gravity. We investigate and illustrate these techniques and their relation in the context of a simple 2d topological theory. We discuss canonical quantization, loop or spin network states, path integral quantization over a

The precise nature of photospheric flows, and of the transport effects they give rise to, has been the subject of intense debate in the last decade. Here we attempt to give a brief review of the subject emphasizing interdisciplinary (solar physics-turbulence theory) aspects, key open questions, and recent developments.

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We use the recent results on solar acoustic modes coming from GOLF and MDI, to demonstrate that we improve the quality of the inversion of the sound speed and the density by avoiding several biases coming from the turbulent surface. The present accuracy allows a quantitative discussion on the physics of the solar nuclear core. We now exclude