On the side of interesting good news, I just heard that yet another Fields Medalist has a blog. This time it’s David Mumford, who is blogging here, with his latest posting about path integrals.

His website contains a wealth of other very worthwhile material, including copies of pretty much all of his papers, some of which had been quite hard to find. Much of Mumford’s career has been in the field of algebraic geometry, where he is a towering figure for mathematicians working during the past few decades. This is not just due to his ideas, but also to his expository talents, which have made many of his monographs and papers the standard place young mathematicians have gone to learn parts of the subject.

Michael Schmitt’s Collider Blog is not new, but it’s great to see that after a period of relative quiet he’s been very active there. His postings from the last couple months give some great detailed explanations of recent news from HEP experimental analyses.

The news from Mochizuki is that there will be a workshop in March on his work, with proceedings to be published. Go Yamashita will be giving two weeks of lectures there. One can hope that this is good news, in that it promises the possibility of an exposition of Mochizuki’s claimed proof of the abc conjecture that will allow other mathematicians to finally understand it well enough to evaluate it.

On the much less interesting news front, multiverse mania continues. Much of this mania seems to have to do with people’s fascination with the idea of different copies of themselves doing somewhat different things an infinite number of times elsewhere. I fear that in my case the multiverse is just causing me to do the same thing an infinite number of times in this universe, which is really tedious. In any case, latest developments are:

- Nathalie Wolchover and Peter Byrne have a new piece at Quanta: In a Multiverse, What Are the Odds?, which leads with the news that “the multiverse camp is growing”, while headlining the obvious “measure” problem that you can’t calculate anything with the idea. Paul Steinhardt is quoted as saying

The multiverse idea is baroque, unnatural, untestable and, in the end, dangerous to science and society.

which is about right, but the rest of the article is mostly dubious claims from the multiverse promotion crowd. More to come next week, looks like the usual bubble collision business.

- Ars Technica has a report on last week’s debate in Brooklyn about the multiverse. Tegmark was on the pro-multiverse side, Wilczek on the anti-side, Janna Levin in the middle. According to the reporter

Overall, Wilczek seemed to get the better of this part of the debate.

Much of the debate seemed to be about the “Many Worlds” interpretation, with Wilczek describing this as an empty idea: “metaphysical baggage added on”, and Tegmark rather enthusiastic about this kind of thing. On the cosmological multiverse, I gather Wilczek’s attitude wasn’t so much negative as that it was too speculative to be interesting.

- What started this multiverse obsession among prominent theorists was the work by KKLT and others supposedly showing that you could get the right cosmological constant in string theory, but that when you did so you ended up with an exponentially large number of possibilities and a likely loss of any predictivity. At the time I thought that was the end of that line of thought in string theory, but instead it turned out to be the beginning of the bizarre period of multiverse mania

we now live in.

The latest news is that KKLT doesn’t actually work, that you can’t get stable string vacua that way. I don’t think though that this will have any effect on multiverse mania and its use as an excuse for the failure of string theory unification. It seems to me that we’re now ten years down the road from the point when discussion revolved around actual models and people thought maybe they could calculate something. As far as this stuff goes, we’re now not only at John Horgan’s “End of Science”, but gone past it already and deep into something different.

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“The latest news is that KKLT doesn?t actually work, that you can?t get stable string vacua that way.”

Are the results of that paper generic, or do they only apply to a specific set of models? Just reading the abstract makes it seem like it’s the latter, though I’m definitely no expert on this stuff.

Peter,

“I don’t know” is an acceptable answer.

Amused,

Sure, I’m no expert and don’t know. But I mentioned this because I heard from someone much better informed than me about it, and they believed it was significant (i.e. it’s not that there are other known ways of doing this). I’m hoping someone better informed will comment here about this. One reason I haven’t looked into this more is that it seems to me that virtually no string theorists any longer care about the technical issue involved. Maybe some commenters will show up to prove me wrong…

Amused,

If you want something amusing about this, see Lubos’s blog, where he picked this up from me. An expert on the problems with KKLT has written in to complain about “the lack of scientific attitude of some members of the string pheno community”. It seems that string theorists trying to examine the problems of KKLT get something like the response to anyone pointing out problems with string theory. In this subject now, as I suspected, it’s all about the politics of defending an ideology, no longer about science.

“The latest news is that KKLT doesn’t actually work, that you can’t get stable string vacua that way.”

Well, not in this universe, but there are infinitely many other universes where it does work! 😉

The multiverse idea is baroque, unnatural, untestable and, in the end, dangerous to science and society.It may also rot your teeth. Being unnatural, it’s undoubtedly outlawed in some states.

A side benefit of “multiverse mania” is that the ironic phrase “In what universe?” seems to have entered the lexicon. (Thanks, perhaps, to Sheldon??)

Peter, I think the real reason for the popularity of the multiverse is for people to imagine that in at least one of them, string theory is right.

(And that in at least one other, “they” received the Milner prize…)