Supersymmetry: Unveiling the Ultimate Laws Of Nature [Paperback]

For example, consider this exercise in friendly vaguary: "One can estimate the maximum possible value of the cosmological constant from the observed expansion rate of the universe. We can also estimate naively what size the cosmological constant should be if we made the simplest guess. The problem is that the maximum size the cosmological constant could have, and still be consistent with what we observe, is many powers of 10 smaller than the naive estimate." I can barely even decipher this ambiguous hand-waving as an indication of the cosmological constant problem; I find it hard to believe that anyone not already familiar with this problem would gain any understanding from this sort of description. They'd do much better to read, for example, Joao Magueijo's beautiful exposition.

Kane does clear up enough to carry across some of his keen insights, including on the daunting task of finding experimental evidence of supersymmetry and on what the shape of fundamental theory implies for different versions of the anthropic principle. He also provides some of the reasons why supersymmetry actually makes predictions that fail in ways the Standard Model already succeeds at least somewhat, casting doubt on the inevitability that supersymmetry will prove to be a successful description of physical law. Actually the book could gain from further splashes of cold water; many times Kane ends up implying that supersymmetry's first impressions are clearly inconsistent with known theory and new versions of the theory were devised that always make predictions just out of reach of our collider technology. Somehow though, Kane repeatedly concludes with assured confidence that this out-of-reach version of the theory will be vindicated. As with strings, the exuberance of the theorist leaves a vague disquiet, if you can sense it, at the prolonged enthusiasm for intricate mathematical elegance in the absence of experimental verification of theoretical predictions - made before the fact, not as postdictions. In the meantime, the wealth of newly observed physical phenomena, such as dark energy, that were wholly unanticipated in decades of arcane theoretical work, beg for that disquiet to receive a greater acknowledgement than can be found here.

While Kane necessarily avoids burdensome mathematics, he does offer some "proofs" and "requirements" of supersymmetry that can be explained qualitatively. This plus the Feynman diagrams are about the best you can expect without grabbing an advanced graduate-level textbook.

One caveat: the author seems almost religiously convinced that the evidence for supersysmmetry is "just around the corner" and always speaks as if the experimental proof is a fait accompli. Based on limits to the theory, we really ought to be seeing the lightest superpartner already and the reader feels that the book takes on an unrealistically-optimistic tone.

One of the questions readers might ask is what difference does supersymmetry make? Is it just a particularly nice way of writing the equations of the standard model? Kane does a nice job of explaining these differences, and helping the reader understand how supersymmetry, as a theory, can be tested.

For example, the Standard Model predicts something called the Higgs boson. The exact number of Higgs bosons, and their characteristics, will help shape the Standard Model. If it turns out that supersymmetry describes nature, we should find that there are at least five types of Higgs bosons.

Kane has included an entire chapter on the subject of testing supersymmetry. One of the nice things about his chapter is the way in which he explains how beam intensity affects the determination of a theories viability. Often, it's not just a matter of finding some new particle, but of observing processes with different decay products at different rates. This is where intensity comes in, as it allows a faster acquisition of the statistics to distinguish between different models. In other words, a collider's usefulness depends on more than the energy of the colliding particles. It also depends on things like how many particles are in the colliding beams (the intensity).

Kane also does a nice job of explaining - at the beginning of the book - the hierarchy among models and theories, though he brings (of course) a distinct theoretical-physicist point of view.

Kane's book is totally qualitative, and intended for the general public. That's not necessarily a bad thing. Generally I enjoy books that address cutting-edge research at the 50,000-foot level where you don't have to be an "expert" to follow the mathematics. Such books make me feel like I'm still using my time wisely, even though the book is "easy reading."

Unfortunately, I think Kane's book is a bit too qualitative. I realize that a subject like supersymmetry is very complicated, and that a 200-page book with no equations can hardly hope to give the subject justice, but this level was just a tad bit too general for me. There just isn't that much solid and clear information that I could grab hold of here, and I came away feeling (unfortunately) like I hadn't learned as much as I'd hoped to.

The book definitely has its good side. Kane is a talented writer, and he does a good job of explaining concepts about theories and models in physics. What he does explain is - for the most part - clear and easy to follow and understand.

For example, Kane points out that the superpartners predicted by supersymmetry could help to explain the missing mass of the universe (mass that is known to exist from the gravitational maps produced by the measuring the motions of stars, but not visibly detected). These superpartners interact through fields that don't act on normal matter - except for the Higgs boson (which is responsible for giving particles mass). It was not clear for me, though, why this has to be so. That's part of the problem. Kane provides a fair amount of information, but much of it takes the form of simple statements thrown out, without the ability to see how these things are required as part of the theory. For every explanation, it seems, I found myself with a dozen more questions.

Some of the side discussions in this book are quite interesting, like the discussion about the search for the Higgs boson, some of the commentary about the origin of the universe, and the missing mass (already mentioned above). I got the feeling that the book was written at a level appropriate for (and possibly intended for) politicians and administrators responsible for funding the colliders necessary to search for the superpartners. Indeed, one of the most interesting parts of the book was the discussion about Fermilab and CERN, and how each is engaged in research in modern physics.

Some of the most interesting stuff is actually in the appendices, which you will definitely want to read. There is also a useful glossary and adequate index.