标题： 作为演化自旋网络的微扰的字符串 显示英文标题

标题： Strings as perturbations of evolving spin-networks

摘要： 量子引力的非微扰公式与微扰弦理论之间的一种联系被展示出来，这是基于Markopoulou提出的非微扰动力学公式。在这个公式中，自旋网络态及其推广的动力学是用具有洛伦兹时空因果结构和多指时间离散类比的历史来描述的。这些历史的微扰被证明是用定义在离散时空中的二维类时表面上的自旋系统来描述的。当历史有一个经典极限为闵可夫斯基时空时，微扰理论的作用量在主导阶由该表面的时空面积给出，如同玻色子弦理论一样。一种将量子引力的非微扰公式与1+1维理论之间的映射推广到一大类理论，其中SU(2)群被扩展为任何量子群或超群。认为非微扰理论要有良好的经典极限的必要条件是，得到的1+1维理论定义了一个一致且稳定的微扰弦理论。 显示英文摘要

摘要： A connection between non-perturbative formulations of quantum gravity and perturbative string theory is exhibited, based on a formulation of the non-perturbative dynamics due to Markopoulou. In this formulation the dynamics of spin network states and their generalizations is described in terms of histories which have discrete analogues of the causal structure and many fingered time of Lorentzian spacetimes. Perturbations of these histories turn out to be described in terms of spin systems defined on 2-dimensional timelike surfaces embedded in the discrete spacetime. When the history has a classical limit which is Minkowski spacetime, the action of the perturbation theory is given to leading order by the spacetime area of the surface, as in bosonic string theory. This map between a non-perturbative formulation of quantum gravity and a 1+1 dimensional theory generalizes to a large class of theories in which the group SU(2) is extended to any quantum group or supergroup. It is argued that a necessary condition for the non-perturbative theory to have a good classical limit is that the resulting 1+1 dimensional theory defines a consistent and stable perturbative string theory.