One can get some idea of what progress there might have been in particle theory during 2007 by querying the SPIRES database for 2007 papers that already have lots of citations. Doing
find topcite 50+ and date 2007
turns up 20 papers of which 6 are experimental papers. Remarkably, the 14 other papers are all about one topic: unparticles. These all refer to Howard Georgi’s initial Unparticle Physics paper from March 2007, in which he describes a possible effective field theory that would be scale invariant and correspond to unusual phenomena potentially observable by collider experiments, phenomena he describes in terms of “unparticles”. In less than a year Georgi’s paper has accumulated 118 citations, with the blogger at Resonaances making fun of the phenomenon of “unpapers” with abstracts such as:
We consider unparticles in whatever uncontext. You are encouraged to forget the paper as soon as soon as you add it to your citation list.
but also making the very relevant comment that this does seem to be getting attention because it is a legitimately new idea:
I must give the credit to Howard for drawing our attention to a whole wide class of collider signatures. Besides, I appreciate Howard’s writing style. He is probably the last man on Earth who truly enjoys particle physics.
As far as I can tell, unparticles don’t solve any of the problems of the Standard Model, but they are theoretically possible phenomena of a different kind that experimentalists can look for, and having as many as possible of such phenomena is very worthwhile. The more different things people are looking for, the more likely they’ll find something unexpected that otherwise might not have been noticed.
This week New Scientist has a long and quite good cover story about unparticles, and recent attempts to use them to explain dark matter, which ends with:
Georgi reserves judgement on whether his unparticles really could be the key to solving the dark matter problem until more work is done, but he’s pleased that people are investigating the possibility. “All I knew was that I had found something cool and I wanted other people to take a look and see what kinds of weird things they might be capable of doing – what mysteries they might solve,” he says. “I’m happy because that’s exactly what people are now doing.”
The story has also made it into the Telegraph.
Besides the unparticle phenomenon, there appear to be very few 2007 theory papers that anyone is paying much attention to. I’ve tried to search around and come up with a list of 2007 papers that have so far gotten 25 citations or more, and a list follows. I’m probably missing some [Note added: additions welcome, and will be added to the list]. The main themes shared by most of these papers are AdS/CFT and attempts to construct metastable vacua as part of a study of the landscape [Note added: this characterization is of the hep-th papers, adding in lots of ones I missed from hep-ph shows that the hep-ph ones cover a much wider variety of topics] .
SPIRES has yet to compile a 2007 “topcites” list, but it looks like the pattern should be very much the same as the last few years: