Why string theory doesnt work

And there they found an interesting set of ideas first proposed by Werner Heisenberg , one of the founders of quantum mechanics. In the early days of quantum mechanics the first half of the 20th century , it wasn't exactly clear what would be the best mathematical approach to explain all that weirdness.

In the s, Heisenberg suggested a rather extreme idea: instead of taking the normal classical physics approach of 1 write down the starting positions of all the particles involved in an interaction, 2 have a model of that interaction, and 3 follow the evolution through time of those particles, using your model to predict a result. Instead, he argued, why don't we just skip all that work and develop a machine, called the scattering matrix, or s-matrix, that immediately jumps from the initial state to the final state, which is what we really want to measure.

That machine encodes all the interaction in a giant box without actually worrying about the evolution of the system. It was a cool idea but proved too difficult for anybody to get excited about, and it died on the vine — until physicists got desperate in the '60s. Reviving this approach to the newfound strong nuclear force , theorists extended and developed the s-matrix idea, finding that certain mathematical functions that repeated themselves were especially powerful.

Other theoretical physicists dived in, and couldn't resist the urge to give the framework a traditional interpretation in terms of time and space and following the evolution of particles. And there they found something surprising: in order to describe the strong force, it had to be carried by tiny, vibrating strings.

These strings appeared to be the basic building block of the strong force, with their quantum mechanical vibrations determining their properties in the microscopic world — in other words, their vibrations made them look and act like tiny little particles. In the end, this early version of string theory, known as baryonic string theory for the kinds of particles it tried to explain, didn't quite cut the mustard.

It was fiendishly difficult to work with, making predictions nearly impossible. It also required the existence of particles that travel faster than the speed of light , called tachyons. That was a major problem for early string theory, since tachyons don't exist, and if they did they would flagrantly violate the incredibly successful special theory of relativity.

Oh, did I mention that baryonic string theory required 26 dimensions to make sense mathematically? That was a pretty big pill to swallow, considering that the universe has only four dimensions.

Ultimately, baryonic string theory died for two reasons. First, it made predictions that disagreed with experiments.

That's a big no-no. The article ends by quoting an exchange between Steve Shenker and my colleague Brian Greene. Brian seems to be one of the few string theorists around willing to actually consider the idea that the theory might be wrong, arguing that if string theory is wrong, it would be good to know this soon so physics can move on. You know, some of the gibing here and there, between us in particular, is harmless.

Stop embarrassing yourself. I think that you are confusing science and politics. The approach of a scientist is to find the relevant facts and data, and make his own conclusions using the brain.

Apart from…. String theory undeniably brought a lot of popularity to the anthropic principle. This achievement makes at least some people happy. Though the same people are probably not overly fond of Lawrence Krauss, who has dared to criticize creationism despite being a layperson on Christian science. Besides the comments on Khovanov homology by the way I met Khovanov for the first time this week, he was here at Columbia giving a series of talks , I also wrote about the Baum-Connes conjecture and Witten localization.

I certainly intend to do more of this and to when possible make more explicit the links I see between these kinds of mathematics and basic questions about quantum field theory. It takes a non-trivial amount of time and effort to absorb new mathematical ideas and by so dominating the mathematical end of particle theory for twenty years, string theory has monopolized the time of the mathematically sophisticated members of the community.

It has also quite literally driven out of the field a lot of people who were interested in other sorts of ideas about how to apply mathematics to questions in particle theory. The mathematically interesting aspects of string theory form an incredibly difficult and complex subject.

If particle theorists acknowledge what has happened to their field, they may finally be able to move on to something more promising. In my opionion, people like Peter Woit, Urs Schreiber and Co are doing a useful service to the physics community by carrying on this sort of public debate in a spirited but relatively civil manner.

Explain what you think is important in your area. What recent progress has there been in non-perturbative QCD? Would string theory have anything further to say to mathematics or would we mathematicians only have to know about the topM-theory? Incidentally, the prediction of realistic string models for the low energy gauge group is SU 3 x SU 2 x U 1. Till then, string theory has absolutely nothing to say about physics. Mathematical beauty some of it debatable is not reality; otherwise the world would be superconformal.

The so-called superstring phenomenology, such as the brane models, is a joke that may fool a few people all the time. Most have a brain, you know, and are not sheep uncritically following whatever a shill may say on the subject.

The fact is that string theory ideas are being featured alongside religion in popular media as an explanation of the universe. Enough said. Let me be more specific why all of these effects of string theory on strongly coupled gauge theories and on mathematics ARE derived from string theory as a theory of quantum gravity including gauge theories with fermions etc.

In early , you could have said that it is just type IIB supergravity, except that today we know a plenty of ways how you can see that the gauge theory is dual to the whole of string theory, including the excited strings. The quantum gravitational phenomena that you can see from the conformal field theory include topology change inside asymptotic AdS spaces, see Maldacena et al.

Mirror symmetry is a relation between two Calabi-Yaus that look geometrically different, but give you the same physics if you compactify string theory on them. If you want to study some mathematical questions about the geometry of Calabi-Yaus only, you truncate the full string theory onto topological string theory. Actually, I think string theory has been such a success as math precisely because it has failed so badly in its original motivation. It looks like they are also following fad trends.

In quantum gravity, the most common examples are space-time fluctuations eg decoherence caused by , defects in the structure of space-time deviations from GR , violations or deformations of Lorentz-symmetry, consequences of the Planck length setting a limit to the resolution of shortest distances, and so on.

All these are possible consequences of quantum gravity that can be searched for by help of phenomenological models. It is in fact very popular, which has its own downsides. Every time someone writes a paper that supposedly tests something quantum gravity, it is all over the news.

Unfortunately, much of this research is rather shallow and low quality, an issue that would be remedied by better funding. So common you will find it mentioned on the slides of a recent talk that I gave as the main cause of the problem. If you invest into quantum gravity as research in a scientific discipline, you also must invest into studying its potentially observable effects. Where are the dozens of research groups dedicated to quantum gravity phenomenology?

Over the history of science, it has happened over and over again that something once deemed impossible became possible. To speak of my personal opinion, presently the most promising areas seem to me CMB entanglement and massive quantum oscillators. Both of these only test the perturbative end, but at least that would move quantum gravity into the realm of being an actual science. Imagine how awesome this would be. The non-perturbative end is of course much more difficult.

You would want to look at relics from the early universe, and to solve the inverse problem one would almost certainly have to combine different observables. Another possibility are naked singularities. It has been claimed some years ago that naked singularities contrary to expectation might actually be created in gravitational collapse without requiring very special initial conditions. This would mean that we potentially could have uncensored view of strong curvature regions.

Remains the question how would you tell a naked singularity from a black hole and what could we learn from this? You might not agree that these are interesting experiments. But getting an answer for which experimental avenue is the most promising is exactly why this field needs funding. My reaction is that I find this a wrong choice of action. There is way too much of that. I think that funding should not play a role when choosing a research subject. And I completely agree with you when you write that there is no system except us — and I would love to see more people try to rebel against it.

To change a system takes sacrifice, it is always easier to work with it. In my own case I have now worked for more than four years without research funding — essentially because I refuse d to work on subjects, which might have secured me a career. As to phenomenology I am certainly no expert. There is of course a difference between BSM physics and quantum gravity phenomenology — and my take on the latter is very much aligned with what Conrad wrote in the above.

I suspect that the only observable effect of quantum gravity might be the standard model itself. Apart from pure quantum gravity phenomenologists, these proposals have come from people studying LQG, spin foam models, causal sets. As you know well, because you are an organizer of it, there are enough people working on quantum gravity phenomenology to populate a person meeting every year or two.

I agree that so far no novel phenomena have been observed, but we do have impressive limits on some of these, some of these above the Planck scale. It is well known that the largest fraction of physicists work in the field of condensed matter physics. In this context electronic structure methods are the theoretical workhorse.

Therefore it is natural that a search for the most highly cited articles in APS journals mainly reveals articles related to electronic structure theory. Here is a very incomplete list:. Of course, this only tells us that there are more people working in this other subfield of physics or, perhaps, that the citation manners are different in these two areas.

String theory does get quite close to reproducing the standard model, and the obstructions there do indeed appear to be technical. Shantanu, Conlon is a well-known young string theorist. Any one who wants to can read what Harlow wrote, read what I wrote, and decide who it is who is being disingenuous here.

I also see that writing a posting mainly saying nice things about a book defending string theory and wishing everyone happy holidays draws comments from string theory ideologues about what an embittered person I am…. Yes, I think you misunderstood this, sorry.

I am still working on qg pheno. But I am feeling rather stupid about it to be honest. Actually, I wanted to leave, but then the money came through. So now I have two years to figure out what to do next.

People go where money goes. There are enough people to populate an person meeting, yes. How many people can you list who have a position that pays full time for qg pheno?

I could come up with maybe ten. How many positions have there been in the last decade searching for candidates in qg pheno? I know of maybe three. How many research groups on qg pheno are there in the world? How many positions have there been for LQG and string theory in comparison? How many departments have string theory or LQG groups, or the occasional other theoretical mathematical?

Do you really believe that this is a good balance between theory development and phenomenology? Contact with experiment is taken for granted, and difficulties that are generally down to instrument sensitivity or funding. If quantum gravity and unification research could be sufficiently compartmentalized, I doubt anyone but a few esoterists would care about the debate, such as it is.

Many scientists from all disciplines and millions of non-scientists alike idolize people like Einstein and Hawking. Maybe Siegel missed some nuances. Imagine if you applied the same logic to artists — do artists stop producing art when they have no money?

No, of course not, they eat porridge for a while, live on the dole, find a patron, whatever. I think that science and art are related in this respect, its a question of passion, idealism —. I was forced to leave some years ago — my research is way off mainstream, but I publish in top journals — and I have continued my work and have manage to get funding elsewhere.

This is the type of rebellion I would wish to see more of. If the funding system sucks, well, then find your money elsewhere! But I agree with Bee that probably such cases are almost non-existent. Maybe you and him are the only current examples.

Is such a service no longer available? At any rate I do hope that PI would organize the next incarnation of the QG phenomenology conference to keep the tradition. I know that there are very few examples of people who work without research funding. An example: Schwarzschild did his important work while fighting in WWI. I think that the analogy with artists is relevant. None of them are planning on giving up this fight in favor of doing string theory in their spare time.

Science communication seems to work by establishing tropes and building on them, and the sort of tropes Conlon is working with are a newer invention, the result of a younger string theory community finding its voice.

I doubt Harlow expected his post to go viral. One amusing thing about his post. It is clear and short and it makes quite a few interesting points some of which are new for me. I liked especially the following points:.