## Saturday, June 11, 2016 ... /////

### String theory vs a cynical demagogue

Five days ago, I didn't have the nerves to complete the reading of another demagogic rant by an aggressive crackpot named Sabine Hossenfelder.

I did find the time and nerves minutes ago. The second part is at least as outrageously false and unacceptable as the first one. Let's discuss the individual sentences.

In his book Why String Theory?, Conlon tells the history of the discipline from a string theorist’s perspective. As a counterpoint, let me tell you how a cynical outsider might tell this story:
An honest scientist or reader doesn't need "counterpoints" to every statement. He wants to know the truth whenever it's known and the relevant evidence whenever answers remain uncertain. Also, don't overlook the words "cynical outsider". Why is this phrase used? The answer is obvious. She wants to spread these lies and hope that some idiotic readers will embrace them but she doesn't want to have any responsibility for these lies, so she attributes them to a virtual "cynical outsider". You're not just a nasty liar, Ms Hossenfelder, but also an outrageous coward, weasel, and fraudster.

OK, is something true about the story by this cynical lying jerk?
String theory was originally conceived as a theory of the strong nuclear force, but it was soon discovered that quantum chromodynamics was more up to the task.
Yes, the first sentence. It's what most books sketching the history of the field basically say because it's true. What is a lie is the suggestion in between the lines that string theorists hide this fact. They don't. They don't hide any facts.

There is nothing wrong about the circumstances under which string theory was born – or, more precisely, first encountered by the human race. People should be evaluated according to the acts they do in their lives, not according to some accidents involving their birth they couldn't control. Similarly but even more sharply, theories are evaluated according to their agreement with the empirical data and their ability to predict or explain them, not according to some historical coincidences about the context in which the scientists have first glimpsed the theory.

In the early 1970s, when QCD was found, it was quickly realized that it was more directly useful to accurately explain the behavior of hadrons. However, the original stringy model wasn't really wrong. The AdS/CFT correspondence found in the late 1990s shows that there exists a dual, equivalent (but very surprisingly so) description of gauge theories in which strings seem to be the fundamental objects. However, these strings exist in a spacetime with an extra radial holographic direction (and perhaps other dimensions). The AdS/CFT correspondence explains both the remarkable "partial successes" of string theory as a theory of hadrons in the late 1960s; as well as the reasons why there were some disagreements.
After noting that string theory contains a particle that could be identified as the graviton, it was reconsidered as a theory of quantum gravity.
The prediction of a consistently interacting massless spin-two particle is amazing and no theory disconnected from string theory has achieved a similar one. A theory that does so automatically solves the very difficult task of reconciling general relativity with quantum mechanics. The task is so difficult that one shouldn't really be surprised that the number of known solutions remains very low, namely one.
It turned out however that string theory only makes sense in a 25-dimensional space. To make that compatible with observations, 22 of the dimensions were moved out of sight by rolling them up (compactifying) them to a radius so small they couldn’t be observationally probed.
Like in the previous sentences, the negative atmosphere in these sentences is absolutely and totally unjustifiable. The ability of string theory to dictate the total number of spacetime dimensions is an amazing testimony of its uniqueness and predictive power and the discovery of the critical dimension, $D=26$, was an important event in the history of the field.

There is absolutely nothing unnatural about the claim that some of the spacetime dimensions are compactified. Each direction in the space may either be macroscopically large or microscopic. These options are a priori equally likely because string theory unequivocally implies that they are equally consistent. It is therefore totally reasonable for string theory to produce a spacetime with $D=4$ decompactified spacetime dimensions plus some number of compactified ones. The geometry of the compact dimensions "knows" about the particle spectrum and interactions one knows from the $D=4$ effective field theory.

Also, it's a complete lie for the cynical jerk to suggest that the very concept of compactification was some newly invented fix. In reality, compactification has been known from the work of Kaluza, first written down in 1919; Klein described details about the compactification procedure and its physical consequences (plus constraints) around 1926.

After his 1916 discovery of general relativity, Albert Einstein has worked on his attempts to find a unified field theory – he believed that a union of GR and electromagnetism would be enough for that. Almost all of these attempts to make the Einstein-Maxwell system "more unified" are seen as hopeless misguided failures now. There exists exactly one exception: Einstein also wrote a few papers about the Kaluza-Klein theory with compactified extra dimensions. This actually made sense and the basic concept has been know to work. Building on this compactification paradigm, Oskar Klein actually found a field theory that was remarkably close to the Standard Model already in the 1930s.

The cynical jerk also says that "the dimensions were compactified to be unobservable" and suggests that it's some trick by the theorists to deliberately avoid the testability. But this is complete nonsense because already 100+ years ago, Max Planck realized that the Planck length $\ell_{\rm Pl} = \sqrt{\hbar G/c^3}$ is the distance scale at which the quantum, relativistic, and gravitational phenomena become visible and appear together. Because this length is easily calculated to be around $10^{-35}$ meters, it follows – and it's been known for more than 100 years – that the bulk of the truly fundamental phenomena in quantum gravity must be expected to occur at length scales so short (and energy scales so high) that we just can't access them by direct experiments.

This value of the fundamental length constant is a fact and to criticize it is on par with criticizing that $2+2=4$. An honest, sane person just cannot criticize or demonize similar facts. Because the compactification is possible and governed by processes in the fundamental theory of quantum gravity, it simply must be expected that the Planck length is a good enough order-of-magnitude estimate for the size of all the dimensions that aren't infinite. So the size of these dimensions is "probably" tiny or Planckian not because someone wanted to "hide" something but because it follows from robust arguments based on the same methods that have been successful at dozens of other places in physics.
Next it was noted that the theory also needs supersymmetry.
String theory doesn't "need" supersymmetry. String theory has the remarkable property that it predicts supersymmetry, the most amazing kind of a symmetry that circumvents the Coleman-Mandula theorem, i.e. the claim that given some seemingly natural assumptions, all symmetries of Nature must be of a very simple kind. String theory was the place in which the supersymmetry was first found – at least if we focus on the history of supersymmetry in the West.

It is absolutely sick to pretend that supersymmetry is some liability or a debt. It is an amazing finding. Supersymmetry is a shockingly beautiful and shockingly realistic symmetry according to thousands of the best minds who have written and keep on writing tens of thousands of papers in which supersymmetry plays a crucial role. Some of these papers are very deep and formal and many of them will unavoidably have a lasting value, others are very directly linked to phenomena that the LHC may already be observing or not and their fate will depend on the experiments. To use the sour language while talking about the "need for supersymmetry" is on par with saying that some museum "needs" to maintain Beethoven's symphonies. Creatures who consider these things to be liability are just uncultural animals.
This brings down the number of space dimensions to 9, but also brings a new problem:
The total number of spatial dimensions is whatever it is and it is absolutely irrational to say that one finite value compatible with the observations is better than another value just because it's smaller. The number 9 is different from 25 but it is in no a priori way "better". In combination with some facts about the stability of Nature etc., it is clear that realistic string models are the supersymmetric ones and with this extra assumption, it follows that there are 9 (string) or 10 (M) spatial dimensions in total.
The world, unfortunately, doesn’t seem to be supersymmetric.
It's simply not true. The correct statement is that we haven't made the relevant observations to decide whether the world is supersymmetric – a reason why the LHC physicists write a new paper about their experimental search for supersymmetry roughly once a week. A person who believes that it's known that the world isn't supersymmetric must completely misunderstand a huge portion of the ongoing experiments as well as a huge portion of the ongoing theoretical work.
Hence, it was postulated that supersymmetry is broken at an energy scale so high we wouldn’t see the symmetry.
It's an oversimplified language that SUSY is "broken". In reality, SUSY is a local symmetry and those can't be broken. Just like the electroweak symmetry, SUSY is "nonlinearly realized" in the world around us. But whether "breaking" or "nonlinear realization" is the phrase we pick, it's important that the situation of SUSY and the electroweak symmetry may be absolutely analogous – and in the SUSY models seriously studied by the phenomenologists, they are absolutely analogous.

It's entirely normal for a symmetry to be "broken" at some scale. Again, it's not some "sacrifice" that a physicist should be ashamed of. Some symmetries are broken, some symmetries remain unbroken. If you place a pencil on a tip, it's in a symmetric position but it will fall down – the rotational symmetry around the axis of the pencil will be broken. This occurs whenever there is a negative, unstable direction in the configuration space. The probabilities that there is one or there is none must be considered to be comparable to 50%. If the potential is $V\sim -x^2$ around $x=0$, the $x\leftrightarrow -x$ symmetry will be broken. The function $-x^2$ is in no way "uglier" than $+x^2$. It's just different – and has some qualitatively different physical consequences.

This is a delusion that these physics-hating crackpots similar to Ms Hossenfelder do all the time. They take whatever conclusion or amazing discovery string theory has made and they start to produce sentences that – in an absolute contradiction with all the evidence – there is something "sour" about the claim or feature or symmetry or mechanism or anything else. None of these negative associations is justifiable in any way. They always show nothing more than the staggering irrational prejudices of the sourballs. And everyone who has taken any of these negative sentences emitted by the likes of Ms Hossenfelder seriously is an irrational brainwashed scumbag.
Even with that problem fixed, however, it was quickly noticed that moving the superpartners out of direct reach would still induce flavor changing neutral currents that, among other things, would lead to proton decay and so be in conflict with observation.
This is a total distortion. There is nothing intrinsically bad about SUSY that could be described by these words. Any and every kind of new physics at a higher scale, e.g. around the corner, induces some processes that contradict the existing observation if the parameters are chosen generically. The theory of new physics must be of some "special kinds" to be compatible with the observations. And the only legitimate question is whether the elimination of the unwanted processes may be explained by technically natural principles or not.

And SUSY generally fits to the group "it can", mainly because of the following:
Thus, theorists invented R-parity to fix that problem.
Theorists were not the first ones who "invented" R-parity. Mother Nature or Auntie Mathematics did so well before the theorists. Theorists only noticed a symmetry that may be reconciled with the effective field theories. In the low-energy field theories, one may have a feeling that he is "building" or "inventing" something like the R-parity. But if one actually uses a string theory vacuum, he unavoidably sees that the R-parity has to be well-defined. Most of these vacua simply predict that this R-symmetry must exist – even if the low-energy effective field theorists could have overlooked this symmetry for some time.

Why do they do so? Because the Standard Model has the following property. Take a particle of the Standard Model – or any bound state of these particles – and look at its baryon number $B$ (it's plus minus one-third for quarks and antiquarks, and otherwise zero); and the lepton number $L$ (one for leptons, minus one for antileptons, otherwise zero). Can we predict whether the particle is a boson or a fermion? In other words, can we predict its $(-1)^{2J}$? Yes, we can. As you should verify, these particles demonstrably obey$(-1)^{3(B-L)} = (-1)^{2J}$ Why? Well, because the quarks and leptons are the only fermions of the Standard Model and both sides of the equations are $(-1)$ for those (because the lepton number or a baryon number but not both is odd; or because the spin is half-integer); and they are easily seen to be $(+1)$ for the rest of the particles (gauge bosons and the Higgs boson). This is not something that theorists have artificially fudged. This is another fact equivalent to $2+2=4$. It's simply true. And it explains that for every completion such as supersymmetrization of the Standard Model, one may define the R-parity as$(-1)^{3(B-L) + 2J}$ and allow this operator to be a symmetry. Like every symmetry, it may be unbroken or broken. In this particular case, an unbroken, exact R-parity is actually possible. So the supersymmetry phenomenologists haven't "fudged" anything. They have just noticed a fact – that the Standard Model particles automatically, demonstrably, and unavoidably have the R-parity equal to $(+1)$. You would need more than fudging – you would need to rewrite the laws of mathematics – to claim that the R-parity can be completely "removed" from particle physics. It's as impossible as the assumption $2+2=5$.

So the scumbags who take Ms Hossenfelder's rants seriously are basically being persuaded that everyone who takes $2+2=4$ seriously is a fraudster and physicists with a good taste are obliged to assume $2+2=5$. Sorry, they are not. The R-parity may be defined in basically all string-inspired or similar supersymmetric models and the only freedom one has is to decide whether the symmetry is broken (R-parity-violating physics) or unbroken. Clearly, the breaking of this symmetry, if any, is observed to be small enough because the heavily R-parity-violating physics is predicting strong unwanted process. We're not fudging anything here. We're just experimentally measuring the answer to the question whether the R-parity is broken and if it is, how much (approximately).

Any kind of demonization here is absolutely indefensible once again.
The next problem that appeared was that the cosmological constant turned out to be positive instead of zero or negative. While a negative cosmological constant would have been easy to accommodate, string theorists didn’t know what to do with a positive one. But it only took some years to come up with an idea to make that happen too.
No theory and no theorist had known a reason to expect a positive yet small cosmological constant. So the observation came as a surprise to many theorists. Steven Weinberg's anthropic arguments could be marginally considered a counterexample. In the late 1970s, he had focused on arguments (tests whether stars may arise in a cosmological model) that allowed him to see an "allowed interval" in which a positive tiny cosmological constant similar to the (later) observed one was natural.

The positive cosmological constant seems compatible with string theory – and if it's not compatible, no one has presented a truly convincing proof yet – but at the same moment, it's hard. A positive cosmological constant is analogous to the cases of a "broken symmetry". For example, supersymmetry is always broken in a de Sitter space. This makes many calculations harder. But this difficulty doesn't imply that a theory has been ruled out.

It hasn't been settled what's the right explanation – if there is one – why the cosmological constant is positive yet tiny. The multiverse answer seems plausible but it surely fails to be fully convincing which is why many utterly sensible people – and string theorists – remain skeptical about it. So we just don't know the answer for certain.

But note that the likes of Ms Hossenfelder always try to abuse any situation and any kind of an answer as a "negative". If an explanation isn't found quickly, they complain that it takes too much time (a Canadian Šmoit notoriously demanded physicists to complete their theories before the deadlines of Stalinist five-year plans). If an explanation is proposed relatively quickly, like "only some years" in this case, they complain that it's too fast. Whatever is the truth or whatever turn Nature, mathematics, or the physics research happen to take, they think it's bad. They're demagogic dogmatically negative filth. Some answers may take minutes to be found, some answers may wait for centuries. For a given question, we just don't know which of these schedules is relevant before the answer is found and settled.
String theory was hoped to be a unique completion of the standard model including general relativity.
And it was basically proven to be the unique completion. Up to some moment, the only evidence was that string theory was remaining the only game in the real-world town. However, actual mathematical proofs that string theory is the only (mathematically possible) game in town began to emerge in recent years, too.
Instead it slowly became clear that there is a huge number of different ways to get rid of the additional dimensions, each of which leads to a different theory at low energies.
That's how Nature works – there is one theory of physics and it has many solutions (even vacuum-like solutions) and physics expanded around these solutions may be described by many effective theories. Even independently of string theory, there are very good reasons to think that this is how Nature has to work – because the particle content we observe in Nature apparently isn't unique in any canonical sense. Again, all negativism is unsubstantiated here.

It's not just fundamental physics that has this property. For example, there is one microscopic theory of genetics which is rooted in DNA. But there are many possible DNA molecules and they lead to very different consequences. Only a ludicrously tiny subset of the possible DNA molecules is realized on Earth. But it doesn't mean that there's something wrong with genetics. It's a part of the beauty that the DNA isn't really unique. Some data may be "almost unique" or be fully derived from some other data. But neither in biology nor in fundamental physics, all the data is fully determined. Something depends on the historical accidents. The theories known to be right surely have solutions that we don't need in the environment we inhabit.
String theorists are now trying to deal with that problem by inventing some probability measure according to which the standard model is at least a probable occurrence in string theory.
It's not a "problem" in the sense of "something bad". It's at most a problem in the sense of an interesting challenge to invite a theorist to produce an explanation and that's what actual scientists work to do, using various approaches. They try and they sometimes fail – I surely think that most proposals concerning the anthropic measures fail. But any negativism about the very general point that people are producing their own solutions is nothing else than the sign of her anti-scientific obsession. It's right for scientists to deal with problems in science – that's their job description. Ms Hossenfelder obviously has a problem with the fact that others, not her, are solving problems which is why she is not a scientist.
So, you asked, why not string theory? Because it’s an approach that has been fixed over and over again to make it compatible with conflicting observations.
String theory has never been fixed. It cannot be fixed. It is demonstrably a totally rigid theoretical structure that has always had exactly the same characteristics and predictions – even though our understanding of the theory wasn't and couldn't have been complete from the beginning.
Every time that’s been done, string theorists became more convinced of their ideas. And every time they did this, I became more convinced they are merely building a mathematical toy universe.
Everyone who has a profound brain understands that the long sequence of profound insights since the birth of string theory have increased the certainty that the theory is very deep and physical. Everyone who has a fart brain thinks otherwise.
String theorists of course deny that they are influenced by anything but objective assessment. One noteworthy exception is Joe Polchinski who has considered that social effects play a role, but just came to the conclusion that they aren’t relevant.
Sociological pressures influence people (especially the gullible ones) and their behavior but they don't affect the scientific truth or the existence, validity, and strength of the evidence. Ms Hossenfelder has never done any natural science in her life. Instead, she's all about demagogic sociological distortions. I have explained why she's full of šit many times, e.g. here.

Serious papers on science are filled with actual scientific evidence and impartial, ideally clever, ideas. And those are features that decide about the success of a paper. Sometimes who only writes papers about sociology or motivated by sociology just can't become respectable among genuine natural scientists.

In this new essay, she spends several annoying paragraphs with accusations of biases. It's very clear that she is the only one in these debates whose talk is primarily a reflection of her biases – well, lies, dishonesty, bad mood, and indefensible mudslinging.
Why not string theory? Because enough is enough.
Why even the most politically correct scientists should feel the moral duty to clean their community from filth such as Ms Hossenfelder? Because the harm that these individuals have created is genuine and exceeds any speculative positive contributions in the future by many orders of magnitude.