Hiroyuki Nakano
Address:	Center for Computational Relativity and Gravitation School of Mathematical Sciences Rochester Institute of Technology 78 Lomb Memorial Drive Rochester, New York 14623, USA
Telephone:	(+1) 585-475-4994
Fax:	(+1) 585-475-7340
Office:	70-3621
E-mail:	nakano_at_astro.rit.edu
Private Website:	Hiroyuki Nakano's Home Page (English) Hiroyuki Nakano's Home Page (Japanese)

Research

Gravitational wave astronomy is one of the central theme of astrophysics in this century, and gravitational waves are the last frontier to observe our universe. Thanks to the recent technological advance, we have almost come to the stage that gravitational waves are detectable. But, gravitational waves are very weak signal. In order to obtain the information from gravitational wave observations, it is absolutely imperative to make an accurate prediction about the theoretical gravitational waveform radiated from astrophysical sources and to build up methods of the analysis.

Gravitational Self-Force (Extreme Mass Ratio Inspiral):

LISA will detect the gravitational waves from a solar-mass compact object orbiting a supermassive black hole at galactic centers. Our final goal in this study is to derive the gravitational reaction force to a compact object orbiting a supermassive black hole, and to construct the precise theoretical templates of gravitational waves which is needed for the gravitational wave astronomy. It has, however, not been attained due to various technical as well as conceptual problems. Please see THIS presented by Eric Poisson as a plenary lecture presented at GR17.

Theoretical and Data Analysis for Black Hole Ringing:

We have developed a search method for gravitational ringing of black holes. The gravitational ringing is due to complex frequency modes called the quasi-normal modes that are excited when a black hole geometry is perturbed. The detection of it will be a direct confirmation of the existence of a black hole. When we use the matched filtering method, the data analysis with a lot of templates required. Here we have to ensure a proper match between the filter as a template and the real wave. It is necessary to keep the detection efficiency as high as possible under limited computational costs.

Acoustic Black Holes at Low Temperature:

We have investigated a condensed matter ``black hole'' analogue, taking the Gross-Pitaevskii (GP) equation as a starting point. The linearized GP equation corresponds to a wave equation on a black hole background, giving quasinormal modes under some appropriate conditions. We suggest that we can know the detailed characters and corresponding geometrical information about the acoustic black hole by observing quasinormal ringdown waves in the low temperature condensed matters. This study is not only an examination of the analogue, but also useful to discuss the data analysis for gravitational ringing.

Black String:

The brane world scenario is a new approach to resolve the problem on how to compactify the higher dimensional spacetime to our 4-dimensional world. One of the remarkable features of this scenario is the higher dimensional effects in classical gravitational interactions at short distances. Due to this feature, there are black string solutions in our 4-dimensional world. Assuming the simplest model of complex minimally coupled scalar field with the local U(1) symmetry, we can show a possibility of black-string formation by merging processes of type I long cosmic strings in our 4-dimensional world. No fine tuning for the parameters in the model might be necessary. The strings will radiate a characteristic gravitational wave.

Publications