超弦理论与宇宙学详解.pptVIP

超弦理论与宇宙学 李淼 中国科学院理论物理研究所 String Theory and Cosmology Miao Li Institute of Theoretical Physics Chinese Academy of Sciences String theory is widely believed to be a theory of quantum gravity. As such, it is usually formulated in a fixed background using the definition of scattering amplitudes More precisely, we can study string theory in a time-independent background that has asymptotic geometry of either Minkowski or (b) Anti-de Sitter String theory used to have many different guises: Open String, Closed String, Heterotic String, Different compactifications. It is now understood that they are manifestations of a single grand theory, M theory Different string theories are connected by duality relations, the prototype of this transformations is the relation between a electric charge and a magnetic charge: However, it has proven very difficult to study string theory in a time-varying background. The most used approach to cosmology in string theory is to use adiabatic approximation. In such an approach, one uses a collection of fields {F(t)} to describe the background at any given time t, F(t) can be a scalar field, or the geometry parameter. By adiabaticity, we mean that the physics of {F(t)} is simply that of a fixed background with the same values of these fields for all times. However, this conservative, poor man’s approach must miss some of most important ingredients of a theory of quantum gravity. One such ingredient is the so-called holography, motivated by quantum physics of black holes. A quantitative statement is that the entropy in a region is bounded by the area of the surface surrounding this region. Bekenstein-Hawking formula: This formula implies that, the physics of quantum gravity can be utterly non-local and even a-causal. In the context of cosmology