Sabine Hossenfelder Interview: Dark Matter, SUSY, LIGO
Sabine Hossenfelder, a theoretical physicist at the Frankfurt Institute for Advanced Studies (FIAS) who also writes the blog Backreaction, discusses dark matter, supersymmetry, loop quantum gravity, and LIGO in this interview. She argues that neither particle dark matter nor modified gravity is settled, that supersymmetry remains unsupported by evidence, and that theoretical physics faces a systemic problem of theorists not producing testable new ideas.
Table of Contents
Key Takeaways
- Sabine Hossenfelder states that both particle dark matter and modified gravity have pros and cons, with the question far from settled.
- She argues the major problem in foundational physics research is theorists failing to produce good ideas for where to look for new phenomena, not experimentalists.
- She recommends that universities interested in quantum gravity set up research groups on quantum gravity phenomenology rather than loop quantum gravity specifically.
- She expects LIGO to deliver new data relevant to solar system formation theory, the population density of black holes and neutron stars, and precision tests of general relativity.
- She states supersymmetry is already overpopulated as a research area and that there is zero evidence it relates to the real world.
What is Sabine Hossenfelder’s view on dark matter versus modified gravity?
Both particle dark matter and modified gravity have pros and cons, and Hossenfelder states she does not think the case is remotely close to being settled.
How does Hossenfelder respond to the idea that physical models should be beautiful and minimal?
Hossenfelder says she has never heard that physical models are commonly regarded as beautiful and minimal, and adds that even if that were a common view, she does not see why it would matter. She suggests it is quite possible that relying on the aesthetic sense of humans to find a good theory to describe nature is a pretty bad idea.
What does Hossenfelder think about the absence of LHC results for supersymmetry?
Asked about the absence to date of encouraging Large Hadron Collider (LHC) results for supersymmetry, Hossenfelder states that the fundamental assumptions behind supersymmetry should have been reassessed 30 years ago. She adds that she cannot predict how such a reassessment would affect future experiments.
What direction should experimental particle physics take?
Hossenfelder argues that the major problem in foundational physics research is not the experimentalists but the theorists. She states that theorists need to come up with good ideas for where to look for new physical phenomena, but instead merely amend models that should have been abandoned long ago. She describes this as a systemic problem that will be hard to fix.
Should top universities set up loop quantum gravity research groups?
Hossenfelder states that loop quantum gravity is even more detached from physics than string theory, and that its mathematics is less interesting in its own right. She would not recommend that any university set up a research group specifically on loop quantum gravity. Instead, she suggests departments interested in quantum gravity set up a research group on quantum gravity phenomenology, hiring people to address how experimental evidence that gravity is quantized could be found, and ultimately which theory of quantum gravity is correct.
What theoretical developments might follow from LIGO’s black hole merger observations?
Hossenfelder states that LIGO will likely deliver lots of new and exciting data for areas including the theory of solar system formation, the population density of black holes and neutron stars, and precision tests of general relativity (GR). She says these data sets will open many avenues for theoretical work. This answer covers developments in the most general sense, including the Japanese, Indian, and space versions of LIGO.
What has Hossenfelder learned from running the “Ask a Physicist” program?
Hossenfelder says everyone who calls the Ask a Physicist program is very passionate about physics. She says the experience reminded her how much fascination physics research inspires, and that it is good to be reminded of that enthusiasm.
Where does Hossenfelder find inspiration and motivation?
Hossenfelder says she is happy to contribute small pieces that she hopes will one day help solve a larger puzzle. She finds plenty of inspiration in the literature, which she describes as full of open problems waiting for someone to tackle them. She says the harder part is choosing wisely which project to spend time on, a decision that must also take into account what pays the rent.
She adds that she goes through phases when she lacks motivation for her research. In those cases, she says she usually spends time working on something entirely different, citing her music videos as examples. She says writing also helps a lot.
How can students be trained to resist anti-science and misinformation?
Hossenfelder states that all students should receive a rudimentary education in logical fallacies, cognitive and social biases, and methods to prevent or mitigate them.
Might Hossenfelder leave academia, and why?
Referring to her March 22, 2017 blog entry on perverse incentives in academia, Hossenfelder says she has considered leaving academia on and off for many years because of this. She states that succeeding in academia often requires playing by certain rules, and that her best chances at success would require working on topics she does not think have much promise. She says she does not see the point in doing that.
Would Hossenfelder recommend a young theoretical physicist focus on supersymmetry research?
Hossenfelder recommends that young physicists avoid putting all their eggs in one basket, building a research profile that allows specialization in different directions if necessary. Regarding supersymmetry specifically, she says she has no idea why anyone would want to focus on it exclusively at this point, calling the field already overpopulated and stating there is zero evidence it relates to the real world.
What does the future hold for Hossenfelder?
Hossenfelder says she has three music videos about physics topics coming up in the following months. She says she has also written a popular science book she hopes will be released in Spring 2018, though the date was not fixed at the time of the interview. She mentions wanting to think further about a covariant version of Verlinde’s emergent gravity she recently worked on, saying it worked better than she anticipated and that she finds this intriguing. She also says she will be working on a project about the phenomenology of quantum gravity, following up on a paper she wrote some years earlier.
FAQ
Is the dark matter versus modified gravity question settled?
No. Hossenfelder states that both particle dark matter and modified gravity have pros and cons, and that the case is not remotely close to being settled.
Does Hossenfelder blame experimentalists for the lack of progress in particle physics?
No. She states the major problem is theorists failing to produce good ideas for where to look for new phenomena, while continuing to amend models that should have been abandoned long ago.
Should universities create loop quantum gravity research groups?
Hossenfelder would not recommend it. She describes loop quantum gravity as more detached from physics than string theory and suggests quantum gravity phenomenology as a better research focus.</p
What might LIGO contribute to theoretical physics?
Hossenfelder expects LIGO to deliver new data on solar system formation theory, black hole and neutron star population density, and precision tests of general relativity.
Does Hossenfelder recommend supersymmetry research for young physicists?
No. She says the field is already overpopulated with zero evidence it relates to the real world, and recommends a diversified research profile instead.
Has Hossenfelder considered leaving academia?
Yes. She says perverse incentives described in her March 22, 2017 blog entry have led her to consider leaving on and off for many years.
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Read the next interview with physicist David Hestenes
I have a BS in Information Sciences from UW-Milwaukee. I’ve helped manage Physics Forums for over 22 years. I enjoy learning and discussing new scientific developments. STEM communication and policy are big interests as well. Currently a Sr. SEO Specialist at Shopify and writer at importsem.com
挺有意思的
hahah
Very good article.
Physics lately, 30 years or so, I won't argue about the dates, often seems to intrude on philosophy. I say this cause I actually feel uncomfortable just thinking about the physics concepts flying around in the 2017's and the implications. It hurts emotionally if I think or feel too hard about it. It reminds of something between the matrix and a hollow deck and being trapped in amber. How real does real have to be to be satisfying. If I don't feel like I'm in a pod and connected to wires, but feel like I am in a real world that I have some small influence in and on I feel ok. But, I'd have to largely be unaware of a reality like a cheap 1 room apartment pod of wires and peeling wall paper. It's gotta be better than that. I don't want to think about it much. Makes me shiver. I much prefer the illusion, if there is a sad but true reality behind our existence. I believe in God because I want to believe, that someone understands what's going on. Even if my certainty, it might be argued, rests on an illusion of perception of a thought and dream, I am satisfied if I feel not alone. In other words my reality can't just depend on me. There really are others out there? I'm not alone? I think God knows loneliness like that and turned himself into 3 beings, and liked that fellowship so much he kept on making more and more and never intends to stop. That's what I would do.
love dadobaggins
Simple and beautiful models. These are what Einstein was also fond of.
Apart from the ever.changing number of parallel universes, universe is quite simple to understand as from creation. The creation of matter and anti-matter through the radiation magnetic moments with the macro magnetic fields is the only model to explain the boson-higgs bosons, fermion transformations even a phenomenon taught in Radiography Testing courses today to explain the high energy radiation-matter interactions at MeV's to be resulted in electron positron pairs. At the cosmogenic origin the same interactions gave the quark, anti-quark pairs to form the matter and anti-matter galaxies.
Besides that, I suggest you to reckon seriously on the role of the Unified Fields as regards the dark energy to answer the missing gravitational energy holding the galaxies together. This dark energy is nothing but the gravitational force induced by the ever expanding cosmogenic magnetic fields hemselves inducing the electric fields that give rise to the unified gravitational fields as explained by the mathematical sophistications on the second Maxwell's equations.
Can you give a couple of examples? That would be helpful.Simply add a parameter to a theory. Say, instead of ##G=T## use ##G=T+c T_1## with some constant c. The original theory is simpler, by Occam's razor "Don't add entities without necessity", which includes such additional terms. Now let's look at the empirical content. An observation which falsified the new equation falsifies the old equation too, given that it is a particular case, with ##c=0##. On the other hand, it is possible that observation fits with the second equation for some ##c >0##, but not for ##c=0##. In this case, the first equation would be falsified, the second not. So, the simpler equation is more falsifiable, thus, has more empirical content, and should be preferred by Popper's criterion.
Of course, one can invent examples in the other direction too, the ultimate most simple theory would be "we know nothing", with zero empirical content. But the case where the more complex theory has more parameters to fit, and therefore less empirical content is, I think, quite typical. It goes back to Popper himself, and is, therefore, part of established standard scientific methodology.
How to give a meaningful explanation of aesthetic feelings like beauty of a theory is much less clear. And beauty can be very misleading. A lot of mysticism has some beauty, so that beauty can lead us into mysticism.
It has. There is Popper's criterion of empirical content: We should prefer theories which make more falsifiable predictions. A theory with more free parameters to fit with observation has typically less predictive power.Can you give a couple of examples? That would be helpful.
Meanwhile I recently started reading Philosophy of Science: A Very Short Introduction, a primer by Samir Okasha; and he happens to raise a similar point to the one I was groping for; he doesn't use the phrase "Occam's razor" but to say "parsimony" is to say essentially the same thing:
All of which echoes something that Hossenfelder says in the interview that this thread is about – here is that quote:
We might like the "feel" of parsimony (I certainly do); we might like Popper's argument that theories ought to be falsifiable (despite criticisms by some of that argument); but these sorts of things are preferences on our part. Hossenfelder seems to be implying what might be an interesting caution though she doesn't go into detail.
Why should one care?
That's more of a counterargument, given the trans-Planckian problem with Hawking radiation. Ok, to have some Hawking-like radiation you don't need much, all you need is that you have to prevent stability (stable stars do not Hawking-radiate), while everything else somehow radiates. So, it is not really a counterargument. But it is nothing which should somehow count as positive.i was replying to this claim
Loop quantum gravity is even more detached from physics than is string theory, and the math is less interesting on its own right. No, I wouldn’t recommend to any university to set up a research group on loop quantum gravity. If some department is interested in quantum gravity, they should set up a research group on quantum gravity phenomenology, and hire people to take on the question how to find experimental evidence that gravity is even quantized. (And, at some point, find out which theory of quantum gravity is the correct one.).
A related question might be whether Occam's razor (which I would argue is rooted in aesthetics) has any real utility;It has. There is Popper's criterion of empirical content: We should prefer theories which make more falsifiable predictions.
A theory with more free parameters to fit with observation has typically less predictive power.
i'm sure abhay ashketar or smolin or rovelli would disagree.Why should one care?
what about loop quantum gravity reproducing hawking entropy and radiation?That's more of a counterargument, given the trans-Planckian problem with Hawking radiation. Ok, to have some Hawking-like radiation you don't need much, all you need is that you have to prevent stability (stable stars do not Hawking-radiate), while everything else somehow radiates. So, it is not really a counterargument. But it is nothing which should somehow count as positive.
Nice overall interview. But this must probably the dumbest thing she ever said:
I have never heard of the fact that “physical models are commonly regarded as beautiful and in a sense minimal” and even if that was so I don’t know why it would matter. Yes, quite possibly it’s a pretty bad idea to rely on the aesthetic sense of humans to find a good theory to describe nature.
There are no LHC results for supersymmetry, if we live inside a real material bubble of a raspberry shaped CP symmetric multiverse. Then super symmetry has even a multiple long distance entangled form down to each quantum.
A related question might be whether Occam's razor (which I would argue is rooted in aesthetics) has any real utility; this blog piece presents a good argument against its over-use in physics and other branches of science: Why The Simplest Theory Is Never The Right One: Occam’s Razor Has A Double Edge. Here's a quote; the bold is mine and highlights the relevance to this thread:
For example Dirac (and many others) has always maintained such a view.Following up on this – Wikiquote has some particularly toothsome remarks by Dirac along these lines; they are taken from a 1963 article by him in Scientific American. The article was reprinted in 2010 and can be found here; the title is "The Evolution of the Physicist's Picture of Nature". These quotes are pulled directly from the article; bold is mine:
Clearly Dirac was expressing a preference only; his argument goes no deeper than that. So even in his time others might have dismissed such a view as irrelevant, just as they might today. This is besides the fact that beauty is subjective.
Martin, where have you seen such comments on the models?I didn't mean the latest speculative models, I mean mathematical models in general and throughout history. For example Dirac (and many others) has always maintained such a view.
Martin, where have you seen such comments on the models?Even as a layperson reading pop-sci accounts, I retain a strong impression that over the years, some inside physics have complained of the un-tidyness of various modern models; that smacks of an aesthetic argument.
Beyond that, mathematics famously has aesthetic appeal; and since physics relies so heavily on math, it wouldn't be surprising that some researchers and authors inside physics would say the same, at least in pop-sci presentations. I did a quick Google and "symmetry" seems particularly mentioned. Here are just a few hits out of many:
– A PBS-related article: Symmetry: How Beautiful Math Makes Elegant Physics
– A particular physicist's pop-sci book: Deep Down Things: The Breathtaking Beauty of Particle Physics (re: the standard model)
– Another book, with a Penrose forward: Fearful Symmetry: The Search for Beauty in Modern Physics
Feynman too seems, in his recorded remarks and interviews, to hint here & there at aesthetics; the difference is, I doubt he would have insisted on it in relation to usefulness. Indeed, in his lecture on harmonics, he says this: In this one discovery of the Greeks, there are the three aspects: experiment, mathematical relationships, and aesthetics. Physics has made great progress on only the first two parts.
What are your views on Loop quantum gravity, and should top Universities like Princeton, Harvard, MIT, Stanford sponsor a loop quantum gravity research group and faculty?
Loop quantum gravity is even more detached from physics than is string theory, and the math is less interesting on its own right. No, I wouldn’t recommend to any university to set up a research group on loop quantum gravity. If some department is interested in quantum gravity, they should set up a research group on quantum gravity phenomenology, and hire people to take on the question how to find experimental evidence that gravity is even quantized. (And, at some point, find out which theory of quantum gravity is the correct one.)
Reference https://www.physicsforums.com/insights/interview-theoretical-physicist-sabine-hossenfelder/
i'm glad you asked the question i've asked.
i'm sure abhay ashketar or smolin or rovelli would disagree.
given sabine's answer
what about loop quantum cosmology's contact with observation in CMB and other observable?
what about loop quantum gravity reproducing hawking entropy and radiation?
what about asymptotically safe gravity, noncommutative geometry, causal dynamic triangulation etc?
should universities that do have LQG research groups and LQG researchers like penn state shut down their LQG research group and fire abhay ashketar et al?
since the LHC found no evidence of SUSY, and proton decay has found no evidence of proton decay as predicted by GUT's
Should universities that do not currently have a string theory research group, set one up in light of current LHC SUSY results?
Very good article. @Greg Bernhardt I wanted to give my vote and give it a "5", but I don't see anywhere I can click on to vote….
Martin, where have you seen such comments on the models?
I am surprised that she has never heard that the models are commonly regarded as simple and beautiful. Aren't they?