I’ll be in England later in the month, in Oxford much of the week of the 26th-30th. That week is the week of the 2022 Clay Research Conference and Workshops. The evening of Tuesday the 27th I’ll be giving a public talk on Unified Theories of Physics, sponsored by the Oxford Centre of the Institute of physics.
The 2022 HowTheLightGetsIn festival in London was supposed to be the weekend of September 17-18, but has been postponed two weeks because of the death of the Queen. It’s now scheduled instead for the weekend of October 1-2 and I’ll likely be there, participating in a couple of panel discussions.
More of the Same:
I’ve written too much here over the years about the problems with multiverse theories. For short versions, there’s also FAQ entries here and here, and a piece called Theorists Without a Theory I wrote for Inference. Seeing some recent things about this topic from people I generally agree with (e.g. here and here) leads to an uncontrollable urge to reiterate some of my arguments, so:
- You can’t argue against the concept of a multiverse in general, dismissing unobservable universes. If you had a very successful theory based on ideas that simultaneously implied successful predictions about what you can observe, as well as unobservable parallel universes, you could get indirect evidence for a multiverse. The strength of this evidence would depend on the details of the theory, but it’s logically possible that this could be strong evidence.
- Arguments pro or con about the “multiverse” that simultaneously engage with the many-worlds interpretation of quantum mechanics and inflationary or string theory landscape models are a waste of time. These are two completely different subjects, which raise completely different issues and have nothing to do with each other. For the rest of this I’ll stick to the second subject, ignore the first.
- If you want to have a serious discussion on this topic, it should be about a particular model or well-defined class of models. One popular class is inflationary models. Here people often write down a well-defined model, but the problem is that it’s a toy model (e.g. no SM fields, just gravity and a hypothetical inflaton field unrelated to any field for which we have a tested theory). Another popular class is the “string theory landscape”. Here the problem is that you don’t have a well-defined model. People who work on this work not with a well-defined theory but with a list of properties of a conjectured, currently non-existent, theory (e.g. “M-theory”). There’s nothing wrong with doing this to see if you get interesting predictions about the world, which would give you some confidence in the existence of the conjectural theory. There is something seriously wrong with doing this if after decades of work you find that the list of properties you have is vacuous in terms of explanatory power.
- It’s important to understand just how vacuous the “string theory landscape” class of models is. The problem is not just a measure problem on the space of possible universes, but much worse: one has no idea what this space is that you would like to put a measure on.
- “Pseudo-science” is an accurate description of “string theory landscape” research. People have complained to me that it is too harsh, should only be applied to activities of people who are abusing the good name of science for discreditable purposes. Doing something because you refuse to admit failure of a scientific idea you have a lot invested in seems to me a discreditable purpose.
Update: Joe Conlon is upset that I’ll be speaking in Oxford. He objects to my credentials, but perhaps my views on his field of string phenomenology (which are shared by a large fraction of the physics community) might have something to do with it. I’m wondering if Conlon also complained about this recent Oxford speaker (video here).