## Saturday, October 07, 2017

### Five homicides by Ethan Siegel

Ethan Siegel is a trained astrophysicist who writes some popular pieces on science, currently for Forbes.

Many of his texts about the elementary enough physics are excellent – or at least very good high school term papers. However, he sometimes writes about the state-of-the-art fundamental or particle physics and all these texts are complete garbage. Every expert must see that Siegel isn't one of them, he just doesn't understand the basic things and his knowledge doesn't exceed that of an average layman who has read several popular books on physics.

It's too bad that over 99% of his readers are totally incapable of figuring out that they're served complete junk and the self-confident tone with which Siegel writes about these matters that are way outside his expertise is a part of his scam.

That's also the case of his new essay
Five Brilliant Ideas For New Physics That Need To Die, Already.
What he doesn't appreciate is that in science, brilliant ideas and theories may only die when they're replaced with more brilliant ones or, ideally, when they're actually falsified experimentally. None of the five victims of his murders are "quite" falsified as of today although this claim is more obvious for some of them than for others. Siegel has described his planned murder of (or the global ban on)
1. Proton decay
2. Modified gravity
3. Supersymmetry
4. Technicolor
5. WIMP dark matter
Siegel basically wants to murder almost all of physics.

First, proton decay. Siegel says that the protons don't decay because we haven't seen a proton decay yet. Holy cow. In reality, the absence of evidence doesn't mean the evidence of absence. I think that even the people without a PhD in particle physics should be capable of understanding the previous sentence. We have only experimentally observed that that the proton lifetime exceeds $$10^{34}$$ years or so.

However, sensible typical models give some $$10^{34}$$-$$10^{36}$$ years now, with natural enough "record breakers" giving $$10^{36}$$ years among the non-supersymmetric models and $$10^{39}$$ years among the supersymmetric ones. So the proton decay is obviously alive and kicking. One may discuss whether orders of magnitude should be added to the price of the huge experiments that are trying to find a decaying proton but to say that we have proven that the protons don't decay is just a complete lie or an embarrassing stupidity, depending on whether the speaker realizes that it's bullšit or not.

If one goes beyond the phenomenological model building and uses really state-of-the-art top-down perspective that includes quantum gravity and string theory, it seems much more likely that the proton has to be unstable. Why? Because a stable proton would mean that the baryon number is strictly conserved. However, it would mean – via Noether's theorem – that the corresponding $$U(1)_B$$ symmetry is an exact symmetry in Nature. Now, in quantum gravity, all symmetries are local so there should better be a an unbroken $$U(1)_B$$ gauge symmetry analogous to the electromagnetic symmetry.

If that existed with a natural value of the gauge coupling constant, it would be easy to see it. We obviously don't see it – a new type of a Coulomb-like force etc. So you could say that the coupling constant of this gauge symmetry could be tiny. But tiny gauge couplings are "mostly banned" as well by the weak gravity conjecture which has gained credibility since we announced it more than a decade ago. In particular, when a star collapses to a black hole which evaporates, the baryon number that was positive to start with almost certainly drops to zero because black holes mostly emit photons and gravitons, not protons. So it just looks unlikely that the proton may be perfectly stable. These arguments don't imply that an experiment is guaranteed to see a decaying proton by 2020 or any particular moment. But the arguments surely do imply that Siegel speaks like an utterly uninformed layman if he concludes that we know that the proton is stable.

Second, modified gravity. He says that every known variant of modified gravity disagrees with something we observe. I sort of agree with this appraisal. But that doesn't quite mean that there's no conceivable version of modified gravity that will be written down in the future and that agrees with everything. In recent years, there has been a mixed inflow of new arguments and evidence. Some of them have weakened the case of modified gravity, some of them strengthened it. Concerning the latter, I could mention the hype about Erik Verlinde's models. I think that this hype is unjustified but it's true that there exist possible scenarios within schemes that are natural in top-down physics that could justify some sort of MOND or derive MOND from holography, as I argued many years before Erik Verlinde.

To say the least, the modified gravity remains a major "frontrunner" to the most justifiable and smooth theories of dark matter – or theories that explain the same phenomena that are sometimes attributed to dark matter. To say that all people must stop thinking about modified gravity is just crazy.

Third, supersymmetry. Siegel would like to euthanize supersymmetry against its will as well. As I mentioned, the usual name describing the euthanasia against the victim's will is a murder or homicide.

He says that it's been proven that SUSY cannot explain the hierarchy problem i.e. the lightness of the Higgs boson relatively to the Planck scale. There are at least two problems with this statement. First, it's untrue. Second, even if it were true, it just wouldn't "kill" all the reasons why sensible people believe that supersymmetry must exist in Nature.

Concerning the current state of supersymmetry and naturalness, we have surely found from the LHC that the incorporation of supersymmetry in Nature, if it's exploited by Mother Nature at all, is less natural than a median supersymmetry researcher assumed a decade ago. However, it's simply not true that supersymmetry is no longer compatible with naturalness. Naturalness is fuzzy, somewhat dependent on personal preferences, subjective degree of tolerance etc. But most papers that study this seriously simply don't conclude that natural supersymmetry has been ruled out.

There's a lot of viable models with various superpartner masses below $$1\TeV$$. On top of that, it's simply not true that all or most superpartner masses need to be this light for naturalness. Two random papers. This April 2016 paper by Baer and three co-authors estimates that one needs to collect 3,000 inverse femtobarns of data at the LHC, about 30 times more than what has been collected, to decide about the fate of natural SUSY. So they obviously concluded that the viability of natural SUSY will remain an open question for a long time.

A random similar paper – there are really many papers like that and they represent a bulk of recent literature about SUSY and naturalness: Dutta and Mimura, August 2016. They argue that MSSM with the electroweak supersymmetry breaking is still alive and may be alive even if $$\mu$$, the Higgsino mass, is large. So the LHC has simply not excluded natural supersymmetry, let alone supersymmetry as a whole.

On top of that, nothing has changed about the other reasons to find SUSY attractive – its almost necessity in superstringy models of the Universe; gauge coupling unification; WIMP dark matter candidate, and others.

The LHC has shown that the range of validity of the Standard Model is way wider than a median particle physicist expected a decade ago (it hasn't deviated from my expectations much so far because I was always skeptical about claims that new physics had to be around the corner – it always looked like phenomenologists' bias to me, bias based on their desire to get the Nobel prize as soon as possible). But some physics is still to be expected at some moment of the future and supersymmetry remains a top candidate for the big idea that will be tested – and a big idea that fundamental physicists will treat very seriously even if the evidence will continue to be absent.

To try to "kill" supersymmetry is just another proof of someone's complete incompetence as a particle physicist. It's still equally important in theoretical studies; and even in phenomenology, it still has about the same fraction of the interest, and for good reasons.

Fourth, technicolor. That's the victim I am least eager to defend because technicolor looked badly motivated for a very long time. But to see is more positively, it has remained one of the phenomenological ideas that the model builders are naturally reviving in one way or another – one of the top ten ideas that are "not supersymmetry". Even if the justification for this idea is weak and it has never been really strong, you simply cannot "kill" or "ban" ideas in the top ten just because you love killing at a random moment for no good reason, as Siegel does.

Fifth, WIMP dark matter. It's incredible in the combination with Siegel's proposed murder of MOND. If he wants to ban physicists' research of both WIMP and MOND, what is really his explanation of the dark matter? Dark matter may be explained by some MOND or composed of WIMPs, SIMPs, MACHOs, planetary size black holes, axions, or two or three other major "types of particles". But some of these explanations has to be right. Or a different one but one can't switch to a new explanation before a sensible new one is actually proposed.

According to numerous people, WIMP and MOND could still be the top 2 available explanations for these phenomena at this moment – and Siegel would like to "kill" i.e. ban both of them? What is his alternative? No dark matter particle has been found directly even though it could have happened a priori. But some explanation has to be right and the probabilities of either answer haven't changed much by the null results of the experiments. In particular, WIMP remains an important plausible paradigm that researchers simply cannot ban because they don't really have viable replacements that would be in a demonstrably better shape.

His desire to make these important theories "die" without a falsification reflects his incompetence in fundamental physics and perhaps his unstoppable desire to murder for no good reason. Maybe Ethan Siegel needs to find a good psychiatrist.