![]() These models are discussed in the extensive review of strong dynamical theories of Hill and Simmons. These schemes also anticipate "partial compositeness". Is most easily seen via dimensional deconstruction (the latter approach does away with the technical details of the geometry of the extra spatial dimension and gives a renomalizable D-4 field theory). ![]() Top Seesaw models have a nice geometric interpretation in theories of extra dimensions, which A more recent version of the Top Seesaw model of Dobrescu and Cheng has an acceptable To remedy the fine tuning problem, Chivukula, Dobrescu, Georgi and Hill introduced the "Top See-Saw" model in which the composite scale is reduced to the several TeV (trillion electron volts, the energy scale of the LHC). While these ideas are still compelling, they suffer from a "naturalness problem", a large degree of fine-tuning. Who connected the theory to the renormalization group and improved its predictions. This was described by Yoichiro Nambu and subsequently developed by Miransky, Tanabashi, and Yamawaki This formed the basis of top quark condensation theories of electroweak symmetry breaking in which the Higgs boson is composite at extremely short distance scales, composed of a pair of top and anti-top quarks. In parallel, early composite Higgs models arose from the heavy top quark and its renormalization group infrared fixed point, which implies a strong coupling of the Higgs to top quarks at high energies. These are forerunners of Little Higgs theories. These ideas were introduced by Georgi and Kaplan as a clever variation on technicolor theories to allow for the presence of a physical low mass Higgs boson. These typically engineer the Higgs boson as a naturally light pseudo-Goldstone boson or Nambu-Goldstone field, in analogy to the pion (or more precisely, like the K-mesons) in QCD. Often referred to as "natural" composite Higgs models, CHMs are constructions that attempt to alleviate fine-tuning or "naturalness" problem of the Standard Model. ![]() Microscopically the composite Higgs will be made of smaller constituents in the same way as nuclei are made of protons and neutrons. This dimension may be related to the Fermi scale (100 GeV) that determines the strength of the weak interactions such as in β-decay, but it could be significantly smaller. In all composite Higgs models the recently discovered Higgs boson is not an elementary particle (or point-like) but has finite size, perhaps around 10 −18 meters. These scenarios are models for physics beyond the SM presently tested at the Large Hadron Collider (LHC) in Geneva. In particle physics, composite Higgs models (CHM) are speculative extensions of the Standard Model (SM) where the Higgs boson is a bound state of new strong interactions. ![]()
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