If you’re interested in the various sorts of internal divisions these days among people doing what gets called “string theory”, you might want to take a look at this blog entry and the discussion there with string phenomenologist Joseph Conlon.
Back in 2002 or so when I started writing my popular book, it was a lot clearer what the term “string theory” meant and who counted as a “string theorist”. If I were writing about this today, there would be a much more confusing situation to try and explain. There’s still a conventional “string theory” story about a supposed theory of everything based on quantized strings often told to the public, but it no longer corresponds much to what researchers who call themselves “string theorists” are actually doing.
To get some better picture of this, it might be a good idea to take a look at the big string theory summer conferences. The biggest is Strings XXXX, this year in Beijing, about six weeks away. No talk titles available yet, but in recent years one clear pattern has been that most of the talks have little if anything to do with the “string theory” of the textbooks (4gravitons tries to categorize things here) . These conferences have been going on for over 20 years.
Since 2002, there has been a breakaway conference, String Phenomenology 20XX, which I think Conlon characterizes accurately as follows:
one reason the String Pheno conference was founded was because people working on pheno topics weren’t getting a look-in at the Strings conference and so set up their own conference. I think the Strings conference is most accurately regarded as the Princeton view of the world (broadly, every year it reflects subjects popular at the IAS and a couple of other similar places).
Generally, the ratios vary with place. A small fraction do string pheno in the US, a significant number in Europe, almost none in India, quite a few in Korea…
This year’s version of this conference has just gotten underway in Greece, you can follow the talks here. One big topic this year is the possible 750 GeV diphoton excess. Around the time of Strings 2016 we should hear whether this is real or not. If it is, String Phenomenology 2017 will likely be completely dominated by the topic, if not, it will have vanished without a trace.
Finally, at the other end of the spectrum is String-Math 20XX, which has been going on since 2011, and this year starts next week in Paris. Quite a few first-rate mathematicians are involved this year. As with Strings 20XX, most of the talks don’t actually have anything at all to do with the theory of a quantized string, and this is more of a “QFT-Math” than “String-Math” conference at this point.
One can read the blog comments mentioned to get some idea of the arguments going on about “phenomenology” vs. “mathematics”. The “phenomenologists” argue that they are the ones doing physics and engaging with data, but don’t really point out that the models they work with have no known (i.e. not purely speculative) connection to any known physical phenomenon. They’re hopeful someday things will be different, but there’s no evidence at all of any progress in that direction.
Phenomenologists like Conlon do battle with their Strings 20XX brethren by accusing them of doing “mathematics”, not “physics”, of in essence really being just an offshoot of the String-Math 20XX crowd. There’s an implicit argument that such people don’t deserve jobs in a physics department, but should move to a math department. I can report though, that while much of the String-Math 20XX research is more than welcome in the math community, that’s not true of most of what goes on at Strings 20XX (a conference that very few mathematicians ever attend).
If you find the current situation confusing, rest assured that you’re not the only one…