118960383
Reheating after quintessential inflation and gravitational waves
We investigate the dependence of the gravitational wave spectrum from quintessential inflation on the reheating process. We consider two extreme reheating processes. One is the gravitational reheating by particle creation in the expanding universe in which the beginning of the radiation-dominated epoch is delayed because of the domination of the kinetic energy of inflaton (kination). The other is the instant preheating considered by Felder et al in which the universe becomes radiation dominated soon after the end of inflation. We find that the spectrum of gravitational waves at ~100 MHz is quite sensitive to the reheating process. This result is not limited to quintessential inflation but applicable to various inflation models. Conversely, the detection or non-detection of primordial gravitational waves at ~100 MHz would provide useful information regarding the reheating process in inflation.
17177650
Dynamical D4-D8 and D3-D7 branes in supergravity
We present a class of dynamical solutions for intersecting D4-D8 and D3-D7 brane systems in ten-dimensional type IIA and IIB supergravity. We discuss if these solutions can be recovered in lower-dimensional effective theories for the warped compactification of a general p-brane system. It is found that an effective p+1-dimensional description is not possible in general due to the entanglement of the transverse coordinates and the p+1-dimensional coordinates in the metric components. For the D4-D8 brane system, the dynamical solutions reduces to a static warped AdS{sub 6}xS{sup 4} geometry in a certain spacetime region. For the D3-D7 brane system, we find a dynamical solution whose metric form is similar to that of a D3-brane solution. The main difference is the existence of a nontrivial dilaton configuration in the D3-D7 solution. Then we discuss cosmology of these solutions. We find that they behave like a Kasner-type cosmological solution at {tau}{yields}{infinity}, while it reduces to a warped static solution at {tau}{yields}0, where {tau} is the cosmic time.
118157237
Approach to gravitational wave physics via the Regge - Wheeler - Teukolsky equations.
119366337
A general proof of the conservation of the curvature perturbation
Without invoking a perturbative expansion, we define the cosmological curvature perturbation, and consider its behaviour assuming that the universe is smooth over a sufficiently large comoving scale. The equations are simple, resembling closely the first-order equations, and they lead to results which generalize those already proven in linear perturbation theory and (in part) in second-order perturbation theory. In particular, the curvature perturbation is conserved provided that the pressure is a unique function of the energy density.
119276954
Squeezed primordial bispectrum from a general vacuum state
We study the general relation between the power spectrum and the squeezed limit of the bispectrum of the comoving curvature perturbation produced during single-field slow-roll inflation when the initial state is a general vacuum. Assuming the scale invariance of the power spectrum, we derive a formula for the squeezed limit of the bispectrum, represented by the parameter fNL, which is not slow-roll suppressed and is found to contain a single free parameter for a given amplitude of the power spectrum. Then, we derive the conditions for achieving a scale-invariant fNL and discuss a few examples.
121738347
Gravitational Radiation from a Kerr Black Hole. I. Formulation and a Method for Numerical Analysis
120440980
All-sky survey high resolution air-shower detector (Ashra)
21928235
Development of a 16-inch UV-ray image intensifier tube
We have developed a 16-inch ultraviolet-ray image intensifier (UVII) tube to form the spherical focal surface of the All-sky Survey High Resolution Air-shower Detector (Ashra) telescope, a new air fluorescence and Cerenkov detector to observe TeV gamma rays, very high energy neutrinos, and extremely high energy cosmic rays. The UVII has a very large effective photocathode area of 16-inch diameter and reduces an image size to 1-inch diameter using the electric lens effect. This enables us to use a solid-state imager to take focal surface images in the Ashra telescope. Thus, UVII is a key technology for the Ashra experiment to realize a much lower pixel cost in comparison with other experiments using photomultiplier arrays at the focal surface. The UVII achieves a high resolution of 3.4 Lp/mm at the input window. The output screen of the UVII is made of a fiber optic plate (FOP) with a concave shape to optimize the electric lens configuration under the fixed curvature of input window. This results in an almost uniform resolution over the whole sensitive area. We have adopted a P47 phosphor screen with a 10% decay time of /spl sim/100 ns and have obtained an amplification factor of about 100. In this paper we present the design, construction, and performance of the 16-inch UVII.
119251015
Performance of a 20-in. photoelectric lens image intensifier tube
Abstract We have evaluated a 20-in. photoelectric lens image intensifier tube (PLI) to be mounted on the spherical focal surface of the Ashra light collectors, where Ashra stands for All-sky Survey High Resolution Air-shower Detector, an unconventional optical collector complex that images air showers produced by very high energy cosmic-ray particles in a 42°-diameter field of view with a resolution of a few arcminutes. The PLI, the worlds largest image intensifier, has a very large effective photocathode area of 20-in. diameter and reduces an image size to less than 1-in. diameter using the electric lens effect. This enables us to use a solid-state imager to take focal surface images in the Ashra light collector. Thus, PLI is a key technology for the Ashra experiment to realize a much lower pixel cost in comparison with other experiments using photomultiplier arrays at the focal surface. In this paper we present the design and performance of the 20-in. PLI.
125208242
All-SKY SURVEY HIGH RESOLUTION AIR-SHOWER DETECTOR (ASHRA)