1

Determination of the equation of state of the universe using 0.1Hz

Gravitational Wave Antenna

Takashi Nakamura 　 and Ryuichi Takahashi

Dept. Phys. Kyoto Univ

Dec.15.GWDAW9

Prog.Theor.Phys in press

2

Dark energy is the most important and most difficult problem in physics in the 21st century so that many independent observations and experiments are indispensable.

At first the optical astronomy took part in the gameusing the type Ia supernova

Then CMB took part in the game by WMAP

Very recently GRB has taken part in the game.

In future why not gravitational wave!!

3

Ghirlanda et al (2004)

?

Peak energy of the spectra to total jet gamma ray energy relation

4

5

GRBs with known z

6

Swift was launched 2004 Nov 20 →more data will be available

7

In 2001 we considered what we can do using 0.1 hertz laser inter

ferometer ( Seto, Kawamura and TN : PRL

87 221103)

8

Our Point and Strategy

• Consider the ultimate possible detector in the sprit of necessity is the mother of the invention

• We call the detector

DECIGO( DECi hertz laser Interferometer Gravitational wave Observatory)

Consider the coalescing binary neutron stars at z=1 . Observe them one year before the final merging

9

Time delay of chirp signal due to the accelerationof the universe can be measured

10

Matched Filter Analysis Using Ultimate DECIGO

11

Punch Point of Ultimate DECIGOa) 100,000 Mass of neutron stars, Black Hole will give us

mass function of NS and BHb) Direct measurement of Acceleration of the universe; In

dependent measurement of the curvature of the universe, independent information of EOS of the universe Today we discuss more details.

c) Background gw predicted by inflation model up to can be measured. Completely independent information from MAP and P

LANCK d) If the fundamental scale is Tev, then the redshifted GW

at T=Tev is just 0.1Hz Band. We may see something.e) For near source , accurate time(0.01sec) and spatial pos

ition(10arcsec) of the coalescing binary neutron stars a week before the final merging (Takahashi and Nakamura at GWDAW8 and ApJ 596 (2003) 231)

12

• discovery of new binary pulsar PSR J0737-3039

• Coalescence rate 180/Myr/Galaxy although corrected factor 2 in 2004.

13

S/N will increase

Expected event rate as a function of z

14

Accuracy of determinationof Hubble parameter as afunction of z.

15

Dependence of the accuracy on the observing time

16

Dependence of the accuracy on the mass of the binary

17

Equation of the state of the dark energy

The angular position of the source is determinedwithin a few arc seconds so that the host galaxy will be identified. Then the red shift z will be obtained.

18

The estimation error of cosmological parametersfor general non-flat universe

19

The estimation error of cosmological parametersfor flat universe

20

The estimation error of cosmological parametersfor SNAP satellite case

21

22

Conclusion1) We showed that the ultimate DECIGO can determine the cosmological parameters comparable or better than SNAP.

2) This is completely independent determination of the property of the dark energy.

3) To determine more than 100,000 wave signals is a challenge for data analysis.

4) What we can do by 1000 times less sensitive practical DECIGO with ten years observations.

23

24

25

• After subtracting these binaries and possible other sources from the row data, we might observe

• the primordial gw background even if