Well, Lads

By Sean Carroll | October 27, 2010 8:45 am

It is a truth universally acknowledged that, among the world-class theoretical physicists of our time, the one with the most entertaining web page is Gerard ‘t Hooft. (Even though he would be annoyed to see that WordPress refuses to display the apostrophe in his name correctly.) See for example the Constitution for 9491 Thooft, an asteroid that was named in his honor. Sounds like a place I would like to visit, once the hotel situation has advanced a bit.

I’m mentioning it because I was struck by this succinct answer to the question, “Will the Higgs be found?” Nothing especially newsworthy, I just enjoyed the spirit of the reply.

More and more frequently, I receive letters and mails from wise people outside physics, telling me that “they know” that the Higgs will not be found, that our theories are baloney, how dare we spend billions of public funds to build machines such as LHC, “to prove, against better judgment, that our theories still stand a chance of being correct”, and so on.

Well, lads, I am not going to answer all of you in person. What you have in common is a blissful ignorance of the scientific facts concerning the Standard Model. Fact is that the W+, W- and the Z boson each carry three spin degrees of freedom, whereas the Yang-Mills field quanta, which describe their interactions correctly in great detail, each carry only two. Those remaining modes come from the Higgs field. What this means is that three quarters of the field of the Higgs have already been found. The fourth is still missing, and if you calculate its properties, it is also clear why it is missing: it is hiding in the form of a particle that is difficult to detect. LHC will have to work for several years before it stands a chance to see the statistical signals of this Higgs particle. What compounds the matter even more is that there may well be several sets of Higgs fields. If there are two, which is eight quarters of the field, we will get five Higgses rather than one. This would be a quite realistic possibility but it would make the detection of each one of them even harder, because they cause more complex statistical signals that are more difficult to predict.

Recently, Dvali, Giudice, Gomez and Kahagias proposed an extremely clever way to get around the need for an explicit Higgs particle, involving extended non-perturbative states they call “classicalons.” This isn’t the kind of thing ‘t Hooft is objecting to — these are wise people inside physics! My money is still on finding the Higgs, but it’s always good to know what the options are.

  • Axe

    How do we know the remaining modes come from the Higgs field and not some other field with different properties?

    My money is on not finding the Higgs.

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  • TimG

    Axe, as I understand the Standard Model Higgs field is essentially the minimal case which could give us the physics we see (massive W+, W-, and Z bosons, etc.). If physics beyond the Standard Model such as supersymmetry holds true, things could be more complicated, with multiple Higgs fields. But we’d still call it a Higgs if it worked by means of the Higgs mechanism (which after decades of study is still one of very few ways anyone has been able to come up with to make the physics work. Sean alludes to another at the end of this post — see more discussion here: http://resonaances.blogspot.com/2010/10/throughout-previous-decade-gia-dvali.html).

    But I think the general point is that it would be unwise to put your money on not finding the Higgs unless you have a solid understanding of the technical details of the Higgs mechanism and all the reasons why people expect it — meaning actually understanding the math, not just reading blog postings about it.

  • Valatan


    that’s right–there are plenty of clever, complicated things you could do if you wanted to–for instance, imagine two fermions coalescing to form a sort of Cooper Pair that we then interpret as the Higgs at low* energies.

    There might be all sorts of high-energy physics taking place beyond the Standard Model. Of course, there might not be.

    *here, of course, low means lower than some threshhold energy higher than the LHC’s energy

  • Aaron Sheldon

    For a scientific theory to be useful in progressing knowledge, wouldn’t you want it to fail on some scale at the limit of achievable observation? If not, you are left in the rather uncomfortable situation of having a theory that does not explain all the observed properties of the universe, but also does not have any counter examples; so that you have no idea where, and when the theory fails.

    There is also the small matter of hubris, not only is it dangerous, it is also unpleasant to listen to.

    Basically you are worse off finding the Higgs than not finding it. There is little utility in confirming theories (aside from refuting skeptics such as those advocating Lorentz violation), when compared to finding contrary experiments. Personally I much prefer the surprise of discovering something I did not know then dredging the barrel of known science. Also for the sake of your jobs, I hope the Higgs is not found. If not you are in the really uncomfortable situation of justifying the employment of theoretical physicists when the standing theory has no room for change. Sure there is lots we do not know but if the current theory has no obvious failings then explaining what we do not know amounts to nothing more than speculation.

  • TimG

    Aaron, as I understand there are good reasons to think that if the Higgs exists it will be found in the range of energies accessible to the LHC. Moreover, there is also some reason to suspect *new* physics to show up in that energy range. So the experiment provides a chance to both confirm a widely held theory and probe new physics. As such, I don’t really see how your criticism is applicable.

  • TimG

    Aaron, just to add to my above comment:

    “There is little utility in confirming theories” seems about as antithetical a statement to science as I could imagine. That’s how science works: You come up with theories, and then you confirm them with experiments. The approach has served us pretty well for the last few centuries.

    Regarding “unpleasant to listen to”, I don’t see a lot of scientists shouting about their theories on street corners. No one is forcing you to listen. But as for me, I appreciate the efforts of Sean and others to keep the public informed.

  • http://home.uchicago.edu/%7Esgralla/ Sam Gralla

    ‘t Hooft’s website says that the gravitational force between two subatomic particles is normally very weak, but that the “gravitational force is as strong as it can ever be … at the horizon of a black hole”. I can’t think of a single sense in which this could be right, given that the spacetime curvature at a horizon can be made arbitrarily small by increasing the mass of the black hole.

    Any ideas, Sean or anyone else?

  • Aaron Sheldon

    I’m not contesting the conclusions of the Standard Model. What I am saying is that if the Higgs is found, and if new particles or interactions are found, then you are in a very tight spot of having a Standard Model that is complete, but observations that are unexplained.

    For example, incorrect classical predictions for the precession of Mercury, or the dispersion of gold ions in a magnetic field spurred the developments of early twentieth century physics.

    I would say physics is at risk of becoming a victim of its own success.

  • Aaron Sheldon

    Actually finding evidence to bolster this claim or that, is really bad science, and it is currently killing the life sciences, and I hope this virulent infection does not spread to the basic sciences. Anyone sufficiently clever or suffering from a mild psychiatric disorder can find patterns in data; it takes an exceptional scientist to prove they do not exist. All kidding aside, the best results in any scientific discipline are typically the negative results, where one discovers the weaknesses in your theories.

    Last century we did not have to reach to far to find where things fell apart. But now we are at risk of having the grounds where things fall apart being considerably out of reach. I’m just expressing the hope that things fall apart within our reach.

  • TimG

    Aaron, you’re saying you think that finding the Higgs *and* finding new physics would be a bad thing? I don’t understand that — if anything, I think that’s the outcome most physicists are rooting for.

    It’s quite possible, indeed widely believed, that the standard model is just a low energy approximation to the physics of the real world, with more surprises waiting at higher energies. Hopefully we will see some of this new physics at the LHC.

    Regarding the relative value of positive and negative results, if *all* you ever got were negative results, science wouldn’t have progressed very far. Also, the sorts of theories we’re talking about here are a lot more sophisticated than just “finding patterns”.

    Regarding the comparison to the life sciences, physicists are in the fortunate position of being able to test things in a much more definitive way than many other disciplines. In high-energy physics, the standard for claiming a “discovery” is 5 sigma significance.

  • Aaron Sheldon

    I’m also not arguing that we haven’t found the strongest experimental evidence supporting the Standard Model. Clearly the evidence outrageously supports the Standard Model, aside from some technical issues in calculating the masses of protons and neutrons. But clearly you must see that never ending experiments that confirm a theory do not push the progress of human knowledge forward nearly as much as a strong and confirmed counter example.

    A belief that the Standard Model is a low energy approximation is just speculation, without strong direction from experiments to indicate where to take future theories. I stand by the, rather broad, statement that intellectual progress can only be made when standing theories are contradicted, because this is where you discover the failings in your assumptions about the universe.

    So lets try this from another angle: we know the range over which the Standard Model has great utility, however because of an absence of contradictory observation we do not have any idea, except the most course to say Planck scale and cosmic distances, of the range over which the Standard Model is valid.

    Part of what makes classical mechanics and electrodynamics so useful to engineers is that, not only do they know the range over which those theories are useful, they also know to high accuracy the range over which the theories are valid. A theory that cannot be invalidated, while being empirically useful, is not that intellectually contributory.

  • chris

    @Sam Gralla

    ‘t Hoofts points on this are nicely summarized in

    as far as i understand it (and i might miss a lot), the essence of his argument is that if you look at a BH from outside and just try to compute its S-matrix, you will realize that all energy scales will contribute. the pictorial example is a particle falling into a BH: if it comes close to the horizon and you are looking at it from the outside, you will see it freeze in. if you add vacuum fluctuations to the picture, these will freeze in, too. so close to the horizon there will be a WW or HH or whatever pair production and you, outside, will see a real W, H etc. if the production happened close enough to the horizon.

    so even if you can argue away the coordinate singularity at the horizon, the horizon remains to be an eminently physical object if viewed from the outside. actually, this realization is at the heart of the holographic principle and all that follows.

  • http://home.uchicago.edu/~sgralla Sam Gralla

    Thanks for the link, Chris. I scanned it and didn’t see this claim or something like it, but it does look interesting.

  • Marcel Kincaid

    “Basically you are worse off finding the Higgs than not finding it. There is little utility in confirming theories (aside from refuting skeptics such as those advocating Lorentz violation), when compared to finding contrary experiments. ”

    Massive logic failure. That there is little utility in confirming theories does not imply that we are better off having our mostly-confirmed theories fail further confirmation.

  • Aaron Sheldon

    There is no logic failure because better and worse are subjective, they depend on the perspective of the speaker.

    I take it that your perspective is that of risk aversion; that is, your choice of ‘better’ is further confirmation of confirmed theories because it carries less risk (and thus less information).

    From my perspective ‘better’ is when our technological limits, such as the LHC, can probe the absolute limits of existing theory. We very well may no longer be living in an age where this can be accomplished, there is a historical precedent for the situtation.

    I stand by my statement that if the Higgs is found then we are not better off, because we are faced with the problem that our technological limits cannot probe our theoretical limits. This is more a statement of hope for contemporary theoretical physics than one of pure logic.


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .


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