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- Alberto Carlini, Akio Hosoya, Tatsuhiko Koike, Yosuke Okudaira
- Physical review letters
- 2006

We present a general framework for finding the time-optimal evolution and the optimal Hamiltonian for a quantum system with a given set of initial and final states. Our formulation is based on the… (More)

- Akio Hosoya, Thomas Buchert, Masaaki Morita
- Physical review letters
- 2004

The effective evolution of an inhomogeneous cosmological model may be described in terms of spatially averaged variables. We point out that in this context, quite naturally, a measure arises which is… (More)

To probe naked spacetime singularities with waves rather than with particles we study the well-posedness of initial value problems for test scalar fields with finite energy so that the natural… (More)

Penrose conjectured a connection between entropy and Weyl curvature of the Universe. This is plausible, as the almost homogeneous and isotropic Universe at the onset of structure formation has… (More)

Extending our previous work on time optimal quantum state evolution, we formulate a variational principle for the time optimal unitary operation, which has direct relevance to quantum computation. We… (More)

A thorough classification of the topologies of compact homogeneous universes is given except for the hyperbolic spaces, and their global degrees of freedom are completely worked out. To obtain… (More)

In the context of averaging an inhomogeneous cosmological m odel, we propose a natural measure identical to the Kullback-Leibler relative information entropy, which expresses the distinguishability… (More)

A complete description of dynamics of compact locally homogeneous universes is given, which, in particular, includes explicit calculations of Teichmüller deformations and careful counting of… (More)