We've had several threads here at PF about Bojowald's work. He is one of the main people responsible for the development of Loop Quantum Cosmology (LQC) as a field. Still fairly young, born in 1973, so still in his thirties.
He was the author in 2001 of landmark paper which you could say started LQC.
He took over the standard Friedman model of cosmology, which all cosmologists use. It is simplified from the full Einstein theory by assuming that matter is distributed uniformly (which it seems to approximately be in reality).
And he quantized that standard cosmo model in a simple straightforward way that takes account of what happens in the full LQG theory. His LQC imitated the full theory, but was not identical to it because the situation in cosmology is so much simpler (matter being evenly distributed).
And he found that when it was quantized it
didn't have a singularity any more.
It had a bounce. At very high density quantum effects (if you want, something akin to the Heisenberg uncertainty principle that quantum systems resist being pinned down) cause repulsion that overcame attraction and made a contracting geometry rebound and turn into an expanding geometry. Gave expansion a big kick in fact.
That was the 2001 landmark paper that started LQC. Just 4 pages and one figure in Physical Review Letters.
http://arxiv.org/abs/gr-qc/0102069
Absence of Singularity in Loop Quantum Cosmology
Martin Bojowald
4 pages, 1 figure
"It is shown that the cosmological singularity in isotropic minisuperspaces is naturally removed by quantum geometry. Already at the kinematical level, this is indicated by the fact that the inverse scale factor is represented by a bounded operator even though the classical quantity diverges at the initial singularity. The full demonstation comes from an analysis of quantum dynamics. Because of quantum geometry, the quantum evolution occurs in discrete time steps and does not break down when the volume becomes zero. Instead, space-time can be extended to a branch preceding the classical singularity independently of the matter coupled to the model. For large volume the correct semiclassical behavior is obtained."
Now the field of Quantum Cosmology is dominated by LQC. If you do a Spires search with keyword "quantum cosmology" for recent stuff, the great majority of the most cited papers will be Loop. It used to be that the most cited QC papers were by Hawking and Hartle and Vilenkin and Linde and Veneziano and like-minded folks----a different group entirely and somewhat more stringish. But that changed radically after 2001. Quantum cosmology grew and became mainly loop. (We'll see if this changes, with Asymptotic Safety and also with Horava Gravity. It is something to watch!)
Here is a sample of QC papers written after 2005, ranked by citation count. This will give you an idea of what kind of research comprises Quantum Cosmology and what the impact has been stemming from Bojowald's seminal papers.
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2005&FORMAT=WWW&SEQUENCE=citecount%28d%29
This will give 334 papers published 2006 or later, with the most cited ones first. And the top 50 papers are mostly all Loop*.
So you could say that Bojowald is a young successful researcher, and that he started something.
Whether and how much it is RIGHT is another question. We will have to see. For one thing LQC is constantly changing. The latest papers show they are shifting over to a spin foam model. Before that, there was a major reformulation around 2006 and 2007. It's an active line of research. Another thing that is happening (I think very important) is the removal of simplifying assumptions---like isotropy. The LQC universe no longer has to look so uniform as it did before.
If anyone wants links to papers showing recent developments, please ask.
*21 of the first 25, were Loop, and 18 of the next 25----so 39 of the 50 most-cited papers. There are some good physical reasons for this, which perhaps we should discuss.
