On the other hand, the dynamical symmetry breaking mechanism of QCD at low energies [39] reflects the color confinement of the gluons and quarks. The light scalar and pseudoscalar mesons as the bound states of the confined quarks and antiquarks were shown to behave as composite Higgs bosons [40]. Such a color confining feature forms stringlike degrees of freedom, i.e., the so-called QCD strings. Inspired by the QCD strings, a string object was motivated to be taken as a basic building block of nature as opposed to a point-like elementary particle. A consistent string theory was found to be realized either in 26-dimensional spacetime for a bosonic string [41] or in ten-dimensional spacetime for a superstring [42,43]. Some interesting string models that are promising to realize the SM at low energies include the perturbative heterotic string models [46] and the mysterious M-theory [47]. It was shown that the six small extra dimensions in superstring theory need to be compactified [48] on the Calabi–Yau manifold [49, 50] in order to obtain the N = 1 supersymmetry. Subsequently, string perturbation theory was found to be divergent [51]. The theory was also demonstrated to require the inclusion of higher-dimensional objects called D-branes, which were identified with the black-hole solutions of supergravity [52]. Practically, a full holographic description of M-theory by using IIA D0 branes was formulated as a matrix theory [53]. Furthermore, the anti-de Sitter/conformal field theory (AdS/CFT) correspondence was proposed to formulate string theory and study some interesting properties [54–56], which provides a new insight into the mathematical structures of string theory. Nevertheless, the basic vacuum solution of string theory remains unknown as there are 10500 possible solutions fitting the constraints of the theory [57,58]. Therefore, it is necessary to explore further how string theory can truly be realized as a theory of everything.
一、QCD 的膠子、夸克行爲有如弦般的自由度。這是 meson 是弦的 hint,不是證據。
二、QCD 弦(第一次聽到)是非點狀(零維)的萬物基礎,這在弦論早有闡述,不意外。
三、超弦論時空十度,M 理論十一度。這屬已知。
四、多餘的空間維度必已蜷曲進卡拉比.邱流形內,以是無法察覺。Understood。
五、M 弦論的全像宇宙描述叫做 matrix 論(這我第一次聽說,不知和電影Matrix 有無關係?)
六、10500 也是多重宇宙論裡可能存在的宇宙約略總數。Paul Davies 寫過的。
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