Mike Duff on M-Theory in New Scientist

This weeks New Scientist features four articles by Mike Duff on M-Theory in which he explains the motivations behind it and answers his critics. It is worthy that New Scientist has allowed him to attack some earlier articles in the magazine that attempted to compare cosmic strings with pseudoscience, and M-Theory with religion. My impression is that more people are beginning to realize that there are good reasons why many of the best theorists are not giving up on string theory just because a few people use such rhetoric to try to discredit its successes.

M-Theory came to prominence in 1995 when Ed Witten started to take the idea of supermemberane theories in 11 dimensions seriously, but its history goes back to at least 1987 when Mike Duff and others classified the possibilities for membrane theories in various dimensions. They showed that the recently discovered superstring theories might emerge from dimensional reductions with the membranes wrapped round to form the strings. Physicists still don’t have a full description of the dynamics of these membranes but a partial solution is provided by Matrix Models.

In his New Scientist article, Mike Duff explains how M-Theory came about. It is important to appreciate that it is not just a wild idea that someone came up with at random. It follows from a need to bring together the standard model of particle physics with general relativity in a way free of the infinities that plague some approaches. The five Superstring theories in 10 dimensions are the only obvious solutions to this problem and they can all be unified into a unique framework using M-Theory. No other approach answers the same questions.

But M-theory is not without its problems. There is an embarrassment of choice when you look at  ways to reduce it to 4 spacetime dimensions in order to match it to physics accessible to experiment. It is hoped that the Large Hadron Collider will discover supersymmetry bringing some hope that a connection between string theories and physics at reachable energies is possible. The trouble is that string theory does not make a definitive prediction that supersymmetry will be observed, and conversely the existence of supersymmetry does not necessarily imply string theory. At best we can say is that there is a correlation between these two ideas so the discovery or not of supersymmetry in the Higgs sector will have a strong influence on the acceptability of string theory.

A second unresolved problem with M-Theory is the absence of a full non-perturbative formulation that is required to make possible any analysis of its phenomenology at the Planck scale. These shortcomings have been explored in a paper on the arXiv last week by Steve Giddings. Mike Duff has identified some relationships between string theories and the information theory of qubits that might just be the first signs of where to look for such a formulation. In work with Borsten, Dahanayake, Ebrahim Marrani and Rubens, Duff has explored a subtle relationship between the classification of STU black holes and 4 qubit entanglement. He takes pains to stress that for the moment at least they “are only claiming that it is useful, not deep.”

The idea that the laws of physics emerges from the dynamics of information has been around for some time and has been boosted in recent years by the theoretical success of the holographic principle and entropic gravity. Whether or not this is a way to understand the fundamentals of M-theory is unclear. It’s a hard problem but not without hope.

Having been lucky enough to meet Mike Duff and some of his students, I know that he remains committed to his work on M-theory and the search for a deeper understanding of its principles. He is unusually open to new ideas but is quick to get to the mathematical details and dismiss anything that simply does not work out. It is not so hard to invent ideas using some persuasive numerology that sound good through the written word, but nature prefers the sound logic of equations.


10 Responses to Mike Duff on M-Theory in New Scientist

  1. Luboš Motl says:

    It’s remarkable that Nude Socialist allowed an actual great person who knows what he’s talking about and who knows how to say it crisply to write such a long text.

    Of course, I’ve met him, too. For example, here I met him almost falling from the floating staircase of Harvard’s Jefferson Lab: :-)

  2. carla says:

    He went to Queens college London which is a good university, but by no means the best for a brilliant physicist. I wonder how he did in his A levels?

  3. Kea says:

    Duff no longer has any excuse to be ignorant of category theory and its applications to M theory. What he does is not particularly sophisticated mathematically, so he can hardly take credit for being open to new ideas.

    • carla says:

      It’s not really in the interest of Duff to pursue new ideas since that’s for the agile minds of his PhD students in their 20s. He’s there to give advice and give an aura of greatness to the place.

      • Kea says:

        Yes, behaviour in line with the patriarchal system. Remember, though, that under a patriarchy, the young men are not permitted to step too far out of line. One does not hear them admit in public even the most obvious ideas, such as the non existence of just about every M theory prediction to date (the mathematics of M theory does not excuse the appalling physics record), although I have heard first hand that some of these young men actually don’t believe in fairy fields or dark forces. A pity they are not permitted to actually admit it without the threat of discrimination and ostrcism until death.

      • Philip Gibbs says:

        LOL Carla, what a terribly ageist thing to say. If you look at Duff’s recent publication list you will find that as well as many papers with his students and outside postdocs, he publishes jointly with Sergio Ferrara who is of similar age, and the seminal observations on the role of hyperdeterminants were published by him as sole author.

        I think the idea that you have to be young to have an agile mind is a myth. What holds older people back more often is the ordinary realities of life such as administration and family duties which are less often distractions for younger scientists.

      • Lawrence B. Crowell says:

        People as they age can maintain a healthy mind. Paul Erdos lived into his 90s and was doing number theory and graph theory up to the end. There are a number of things one can do to prevent mental deterioration with age. The first is to keep an open and active mind, keep engaged with intellectually worthwhile subjects, and stay on top of new ideas. The next is to prevent one’s thinking from getting trapped in an obsessive loop of repeated ideations. The best way to prevent this is to avoid extreme religious and political thinking, which can be every bit as mentally unhealthy as any addictive drug. This also requires one to admit error on one’s part when that is evident. The most serious fallacy is to think of one’s self as infallible. The other is to avoid mind altering and addictive substances, in particular alcohol and other forms of drugs.

    • Philip Gibbs says:

      Kea, I dont know what Duff thinks about category theory so I’ll just give my own point of view. I like the concepts behind category theory very much and the results in M-theory seem very encouraging.I think n-category theory will play an important role in understanding the fundamental mathematics behind the existance of our multiverse :) .

      I would love to use those ideas myself or even contribute, but in truth I am just not very good at category theory. I know the basics but I can’t grok the more abstract side of it. I prefer more concrete problem solving type research, aswell as the more philosophical questions about how the laws of physics should work. Luckily other people like you who are better at that abstract style of maths are there to advance the subject so I am happy to sit back and admire the results.

  4. In the continual dominance of M theory culminates the crisis of not only theoretical physics but of Big Science in general. It does not matter whether the theory works or not, what matters is how many receive their monthly salary from producing articles about it.

    The failure of M-theory was clear already from the beginning: the notion of spontaneous compactification is certainly the ugliest brain child that theoretical physics has ever managed to give birth to. Certainly it was originally introduced in the lack of anything better and in hope that this something better would soon emerge. This did not happen and the ultimate outcome is the archive trash produced by the old stars like Susskind about which we can read in New Scientist.

    M-theory has been for theoretical physics what Lysenkoism was for Soviet biology. It is certainly not an accident that the funding system of Big Science is extremely hierarchical just like Soviet Union and dissidents are mercilessly thrown out of the system just like they were thrown out in days of Lysenko.

    • Lawrence B. Crowell says:

      It is likely the universe has “stringy” and “braney” structures. I will not necessarily say I think this is the final answer, or even that this “must be so.” However, this is extremely rich in structure and it seems more implausible to think this is pure math-fiction.

      Duff and his crew Borsten, Dahanayake, Marrani and Rubens have demonstrated some remarkable correlations between BPS black holes and extremal black holes with 3 and 4 qubit entanglements. It also turns out there are correlations between Dp-branes for p = 0, 2, 4, 6 I have a couple of notepads of calculations I have been working on with how F_4 diagonalizes the Jordan matrix algebra and eigenstates associated with G_3/H_3 = E_{8(8)}/SO(16). This connects with Phillip Gibbs’ work on the hyperdeterminant with cubic equations (elliptic curves) and quartic equations. This is an interesting area to learn about.

      Bousso and Susskind have a paper out on WMI and the stringy landscape. Frankly I find Duff et al have a much cleaner approach to the quantum mechanics of string-M-theory than this. The mathematics it tight and the results have a pretty clear and crisp outcome.

      As I said this is not anything to “believe in.” M-theory and related issues appear to be the most effective approach to working with this arena of physics. We do not have much experimental data as yet, but that might change. We may get to test some of this, however obliquely, with the LHC and get some signatures which uphold stringy-physics, or maybe we will get nothing at all. Test quantum gravity in full requires of course interaction energies that are far beyond anything we may ever manage to generate. So we are looking through a dark glass in many ways.

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