Sunday, May 18, 2008


So I've obviously been a really bad blogger recently, but I was quite busy. One of things I was doing was attending a workshop at the ECT* (not sure what's up with the star; I suppose ECTRNPARA was a little too long, so they used a shell wildcard) in Trento, Italy. The workshop was sort of a miniature version of the lattice conference, with representatives from all major collaborations talking about the state of the art in simulations with dynamical fermions. I briefly considered live-blogging it like I do with the lattice conferences, but in the end decided against it for various reasons. The ECT* is very nicely located in a historical villa a little outside of Trento itself; the meeting room is in the basement of a side building, though, so there is nothing to distract one from the talks. The workshop was very well organised, with hotels, meals and everything arranged in advance, so five stars to the organisers and ECT* staff for that.

Contentwise, the workshop brought few real surprises, but a lot of confirmation of the fact that dynamical fermion simulations are now pretty far advanced due to a combination of algorithmic advances and ever greater and faster parallel computers. To all but eliminate systematic errors, ultimately, one will need to simulate at small lattice spacings (0.04 fm, say), large volumes (5 fm, say) and at the physical light quark masses. At the moment, each major group is accomplishing at least one of these, with some approaching two out of the three. In three or four years at the latest, somebody will have an ensemble of configurations fulfilling all three. Given that lattice spacings this small, or quark masses anywhere in the vicinity of the physical point, were considered completely out of reach just three years ago, it is fair to say that the lattice has come a long way in a short time.

Some people will therefore sometime use phrases like "when we will have solved QCD", but great as that sounds one first needs to consider what solving QCD means. Even when we have predictions for the hadronic ground state mass spectrum with essentially zero systematic error, there will still be excited states, decay constants and widths, scattering lengths, form factors, multi-hadron states and potentials, and so forth coming from QCD, and many of these will likely require considerable effort in terms of new theoretical developments in order to make it viable to extract them from lattice simulations. So unless "solving QCD" means "computing the hadronic ground state mass spectrum", we won't solve it for a fair while to come. Which is good news, because otherwise I'd really have to start looking for a different job, and I actually like this one.

And of course then there is the often-mentioned possibility that the LHC might find evidence of technicolor or some other new strongly coupled physics at higher energies, putting lattice theorists at the cutting edge of the energy frontier. That sounds more like some kind of dream though.

I've also been doing other interesting things, but I'll save those for a different post. If everything goes as hoped for, there may also be an exciting guest post on this blog in the not too distant future.