accelerating universe and the scalar-tensor theory加速宇宙和标量张量理论.pdfVIP

Entropy 2012, 14, 1997-2035; doi:10.3390/ OPEN ACCESS entropy ISSN 1099-4300 /journal/entropy Article Accelerating Universe and the Scalar-Tensor Theory Yasunori Fujii Advanced Research Institute for Science and Engineering, Waseda University, Tokyo, 169-8555, Japan; E-Mail: fujii@ Received: 18 September 2012; in revised form: 11 October 2012 / Accepted: 15 October 2012 / Published: 19 October 2012 Abstract: To understand the accelerating universe discovered observationally in 1998, we develop the scalar-tensor theory of gravitation originally due to Jordan, extended only minimally. The unique role of the conformal transformation and frames is discussed particularly from a physical point of view. We show the theory to provide us with a simple and natural way of understanding the core of the measurements, Λobs ∼ t−2 for the observed 0 values of the cosmological constant and today’s age of the universe both expressed in the Planckian units. According to this scenario of a decaying cosmological constant, Λobs is this small only because we are old, not because we fine-tune the parameters. It also follows that the scalar field is simply the pseudo Nambu–Goldstone boson of broken global scale invariance, based on the way astronomers and astrophysicists measure the expansion of the universe in reference to the microscopic length units. A rather phenomenological trapping