Is quantum gravity unpredictable

摘要: An investigation of Hawking's proposal that the inclusion to topologically non-trivial manifolds in functional integral quantum gravity leads loss coherence is carried out. We discuss some problems associated with $-matrix theory, including breakdown connection between symmetry principles and conservation laws. It proposed use Kaluza-Klein theories study this issue, since these contain well-defined euclidean instantons. These can be used perform explicit semiclassical calculations effects space-time foam. A general method presented for constructing instantons based on solutions ordinary Yang-Mills theory. argued none will lead a mechanics. The physical foam are discussed detail using four-dimensional