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In particle physics, models with universal extra dimensions include one or more spatial dimensions beyond the three spatial and one temporal dimensions that are observed. These models, proposed and first studied in 2000,〔 〕 assume that all fields propagate universally in the extra dimensions; in contrast, the ADD model requires that the fields of the Standard Model are confined to a four-dimensional membrane, while only gravity propagates in the extra dimensions. The universal extra dimensions are assumed to be compactified with radii much larger than the traditional Planck length, although smaller than in the ADD model, ~10−18 m,.〔Sabine Hossenfelder, "(Extra Dimensions )", ''Backreaction'', 8 July 2006 (accessed 13 March 2009).〕 Generically, the—so far unobserved—Kaluza–Klein resonances of the Standard Model fields in such a theory would appear at an energy scale that is directly related to the inverse size ("compactification scale") of the extra dimension, The experimental bounds (based on Large Hadron Collider data) on the compactification scale of one or two universal extra dimensions are about 1 TeV.〔 〕 Other bounds come from electroweak precision measurements at the Z pole, the muon's magnetic moment, and limits on flavor changing neutral currents, and reach several hundred GeV. Using universal extra dimensions to explain dark matter yields an upper limit on the compactification scale of several TeV. ==See also== * Large extra dimensions * Kaluza–Klein theory * Randall–Sundrum model 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Universal extra dimension」の詳細全文を読む スポンサード リンク
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