Riuji Mochizuki

ETERNALLY ACCELERATING SPACELIKE BRANEWORLD COSMOLOGIES

We construct an eternally inflating spacelike brane world model. If the space dimension of the brane is three (SM2) or six (SM5) for M theory or four (SD3) for superstring theory, a time-dependent n-form field would supply a constant energy density and cause exponentially expansion of the spacelike brane. In these cases, the hyperbolic space perpendicular to the brane would not vary in size. In the other cases, however, the extra space would vary in size.We construct an eternally inflating spacelike brane world model. If the space dimension of the brane is three (SM2) or six (SM5) for M theory or four (SD3) for superstring theory, a time-dependent n-form field would supply a constant energy density and cause exponentially expansion of the spacelike brane. In these cases, the hyperbolic space perpendicular to the brane would keep its scale factor constant. In the other cases, however, the extra space would vary in size.

Recoil of Rotating Detector

The question of why rotating detectors may respond even in the appropriate vacuum defined via canonical quantization has been a puzzle. We solve this puzzle by taking the recoil of the detector into account. The influence of the recoil, even in the limit of an infinite mass detector, appears in the response function. This enables the detector to respond in the vacuum if it is rotating, though in linear uniform motion it never responds in the vacuum, � � , � � � ,

ETERNALLY INFLATING COSMOLOGIES FROM INTERSECTING SPACELIKE BRANES

Intersecting spacelike braneworld cosmologies are investigated. The time axis is set on the scale parameter of extra space, which may include more than one timelike metric. We obtain the eternally inflating (i.e. undergoing late-time inflation) Robertson–Walker spacetime and extra space with a constant scale factor. In the case of multibrane solutions, some dimensions are static or shrink. The fact that the largest supersymmetry algebra contains 32 supercharges in four dimensions imposes a restriction on the geometry of extra space.

STABILITY OF S-BRANE SINGULAR SOLUTIONS AND EXPANSION OF THE UNIVERSE

We investigate stability of single S-brane singular solutions obtained in our previous papers. A stable perturbative solution exists for each of them, while an unstable one exists only if the dilaton field does not depend on time. We apply these perturbative solutions to inflation and late-time acceleration of expansion of the universe.

QUANTUM EFFECT AND OPERATOR ORDERING IN STOCHASTIC HAMILTONIAN

We investigate the operator ordering in the stochastic Hamiltonian in a generalized stochastic calculation method. It is uniquely determined in the continuum limit and yields the Fokker-Planck equation without dependence on the calculation method.

STOCHASTIC CALCULUS AND COVARIANT AND ROTATION-INVARIANT LANGEVIN EQUATION FOR GRAVITY

We investigate the relations among the Langevin equation, the Fokker-Planck equation, and the stochastic action, both in the sense of Ito and of Stratonovich. In the latter case we suggest a somewhat modified Langevin equation which is covariant and rotation-invariant.

Understanding Weak Values Without New Probability Theory

The physical meaning of weak values and measurements can be completely understood with Born rule and the general probability theory. It is known that the weak value of an observable Â

Weak value as an indicator of back-action

\hat {A}

Simultaneous Measurability of Error and Disturbance

with post-selection 〈F| may be out of the eigenvalue range of Â

Establishment and Current Status of Patient Community at Tokyo Dental College

\hat {A}