- #101
mitchell porter
Gold Member
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Via Peter Woit, a talk by Joseph Lykken reviewing a number of non-susy approaches to explaining the tunedness of the Higgs mass. (Woit also links to a more theoretical talk by Nathan Seiberg about the hierarchy problem, that is also worth reading.)
It seems that causal explanations of the tuned Higgs, like Shaposhnikov-Wetterich and Nicolai-Meissner, are beginning to be recognized as a distinct class of theory, alongside "unnatural" and/or anthropic finetuning (Arkani-Hamed) and new versions of SUSY which restore naturalness (numerous authors). This is heartening, and it's especially gratifying to see Lykken at the fore of this, since it was his soundbite about the metastability of the universe, and the flurry of media it generated, which prompted my dismay in comment #92.
In fact, Lykken not only reviews several possibilities, but he devotes the most attention to a model in which dark matter plays a role in a Nicolai-Meissner-like mechanism. That is, he combines "radiative electroweak symmetry breaking" - in which the destabilizing Mexican-hat self-interaction of the Higgs field (that is responsible for a ground state with a nonzero VEV, and thus for the Higgs mechanism) is induced by virtual effects - with high-energy boundary conditions that tune the resulting Higgs mass. In this model, the new particle which induces radiative EWSB is also the dark matter!
So not only are causal models of Higgs tuning beginning to be recognized, but they are being combined with BSM facts from elsewhere in physics. Perhaps this will even become a popular topic while we wait for the LHC to be switched on again...
edit: What would really be dramatic, is a model of a "causally tuned Higgs" which also explains the observation that the mass of the Higgs is half the sum of the Z, W+, and W- masses. Like the tuning of the Higgs mass, this isn't just something that was noticed after the discovery, it was actually used to predict the correct value. Unfortunately, the "theory" which produced that formula is nonsensical, so the formula really needs some other justification.
Also, like the Koide relation, it's a relation between low-energy masses which shouldn't have simple relations, because of renormalization group running. (This may be contrasted with theories like Shaposhnikov-Wetterich, where the low-energy Higgs mass acquires its value from a simple boundary condition at high energies.) So most physicists will dismiss it as numerology and a coincidence. But as Lykken says in his talk (slide 20), "dismissing striking features of the data as coincidence has historically not been a winning strategy..."
It seems that causal explanations of the tuned Higgs, like Shaposhnikov-Wetterich and Nicolai-Meissner, are beginning to be recognized as a distinct class of theory, alongside "unnatural" and/or anthropic finetuning (Arkani-Hamed) and new versions of SUSY which restore naturalness (numerous authors). This is heartening, and it's especially gratifying to see Lykken at the fore of this, since it was his soundbite about the metastability of the universe, and the flurry of media it generated, which prompted my dismay in comment #92.
In fact, Lykken not only reviews several possibilities, but he devotes the most attention to a model in which dark matter plays a role in a Nicolai-Meissner-like mechanism. That is, he combines "radiative electroweak symmetry breaking" - in which the destabilizing Mexican-hat self-interaction of the Higgs field (that is responsible for a ground state with a nonzero VEV, and thus for the Higgs mechanism) is induced by virtual effects - with high-energy boundary conditions that tune the resulting Higgs mass. In this model, the new particle which induces radiative EWSB is also the dark matter!
So not only are causal models of Higgs tuning beginning to be recognized, but they are being combined with BSM facts from elsewhere in physics. Perhaps this will even become a popular topic while we wait for the LHC to be switched on again...
edit: What would really be dramatic, is a model of a "causally tuned Higgs" which also explains the observation that the mass of the Higgs is half the sum of the Z, W+, and W- masses. Like the tuning of the Higgs mass, this isn't just something that was noticed after the discovery, it was actually used to predict the correct value. Unfortunately, the "theory" which produced that formula is nonsensical, so the formula really needs some other justification.
Also, like the Koide relation, it's a relation between low-energy masses which shouldn't have simple relations, because of renormalization group running. (This may be contrasted with theories like Shaposhnikov-Wetterich, where the low-energy Higgs mass acquires its value from a simple boundary condition at high energies.) So most physicists will dismiss it as numerology and a coincidence. But as Lykken says in his talk (slide 20), "dismissing striking features of the data as coincidence has historically not been a winning strategy..."
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