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Kazuhiro Yamamoto

Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut)Institut fuer Gravitationsphysik, Leibniz Universitaet Hannover

Gravitational wave and detectors

6 May 2010 @Università degli Studi di Trento, Trento, Italy

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6 May 2010 (Afternoon)

Gravitational wave and detectors

7 May 2010 (Morning)

Fundamental noise of interferometric gravitational wave detectors

0.Abstract

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I would like to explain …

(1) What is the gravitational wave ?

(2) Why do we want to detect gravitational wave directly ?

(3) How can we detect gravitational wave ?

(4) What kinds of detector are there ?

Did they provide scientific results ?

(5) What kinds of detector will there be ?

Will they be able to detect gravitational wave ?

Contents

1. Gravitational wave

2. Aims of detection

3. Outlines of detectors

4. Recent results in observation

5. Summary

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1.Gravitational wave What is the gravitational wave ?

1915 A. Einstein : General theory of Relativity

“Gravitation is curvature of space-time.”

1916 A. Einstein : Prediction of gravitational wave

　　　　　 “ Gravitational wave is ripple of space-time.”

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Wikipedia (A. Einstein, English)

A. Einstein, S. B. Preuss. Akad. Wiss. (1916) 688.

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http://spacefiles.blogspot.com

Gravitational wave

Speed is the same as that of light.

Transverse wave and two polarizations

1.Gravitational wave

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1.Gravitational wave Interaction of gravitational wave is too weak !

Artificial generation is impossible !

No experiment which corresponds to

Hertz experiment for electromagnetic wave

Astronomical events

Strain [(Change of length)/(Length)] : h ~ 10-21

(Hydrogen atom)/(Distance between Sun and Earth)

No direct detection until now

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1. Gravitational wave Indirect detection of gravitational wave

Binary pulsar

(R.A. Hulse and J.H. Taylor,

Astrophysical Journal 195 (1975) L51.)

Generation of gravitational wave

Energy emission

Change of period of binary

Observed change of period agrees with theoretical

prediction by radiation formula of gravitational wave.

J.H. Taylor et al., Nature 277 (1979) 437.

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1.Gravitational wave Recent result

J.M. Weisberg and J.H. Taylor, ASP Conference Series, 328 (2005) 25 (arXiv:astro-ph/0407149).

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1.Gravitational wave

Web site of Nobel foundation

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What is the motivation ?

Physics : Experimental tests for theory of gravitation

Astronomy : New window for astronomical observation

2.Aims of detection

No direct detection until now

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Physics : Experimental tests for theory of gravitation

(1) Speed : Alternative theories of gravitation predict the difference of speed between gravitational wave and light.

2.Aims of detection

C.M. Will, “Theory and experiment in gravitational physics”(1993) Cambridge University Press.

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2.Aims of detection (2) Polarization : Alternative theories of gravitation predict the 6 kinds of polarizations (General relativity : 2).

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2.Aims of detectionAstronomy : New window for observation

Gravitational wave astronomy

Gravitational wave sources

(1) Burst source

(2) Periodic source

(3) Stochastic source

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2.Aims of detection(1) Burst source : Supernova

Mechanism of the core-collapse SNe still unclear

Shock Revival mechanism(s) after the core bounce.

GWs generated by a SNe should bring information from the inner massive part of the process and could constrains on the core-collapse mechanisms.

M. Punturo, GWDAW Rome 2010

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2.Aims of detection(1) Burst source : Compact binary coalescence

Neutron star, Black hole

msec

chirp signalcoalescence

quasi-modeoscillation

-300Hz -1kHz

K. Kuroda Fujihara seminar (2009)

New standard candle for measurement of distance

Equation of state at high density, formation black hole

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2.Aims of detection(2) Periodic source : Pulsar

M. Punturo, GWDAW Rome 2010

Asymmetry of shape

Structure of interior

Rotating neutron star

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2.Aims of detection(3) Stochastic source (Background)

(a) Astronomical sources

Compact binary

(b) Cosmological sources (Early universe)

Cosmic Gravitational wave Background ?

Quantum fluctuation in inflation

Phase transition at early universe

(Grand Unified Theory(cosmic string), Electroweak, QCD, …)

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3.Outlines of detectorsThere are a lot of kinds of detectors !

Resonant detector

Interferometer (on Earth)

Interferometer (Space)

Doppler tracking

Pulsar timing

Polarization of cosmic microwave background

and so on …

Frequency range : 10-18 Hz – 108 Hz

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3.Outlines of detectorsResonant detector Gravitational wave excites resonant motion of elastic body.

Weber bar (most popular one)

Diameter : several tens cmLength : a few metersResonant frequency : about 1 kHz

“300 years of gravitation”(1987) Cambridge University PressFig. 9.8

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3.Outlines of detectorsJoseph Weber (1919-2000) Pioneer of gravitational wave detection

He is one of persons who proposed the concept of laser.

Other persons (C.H. Townes, N.G. Basov, A.M. Prokhorov) won Nobel prize in Physics (1964).

He started development of resonant detector. J. Weber, Physical Review 117 (1960) 306.

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3.Outlines of detectorsWeber event J. Weber, Physical Review Letters 22 (1969) 1302. “Evidence for discovery of gravitational radiation”

Coincidence between two detectors (Distance is 1000 km)

Direction of sources : Center of our galaxy

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3.Outlines of detectorsHowever, …

No experimentalists could confirm Weber event

even if they used detectors with better sensitivity !

We do not know what caused Weber event,

but gravitational wave did not.

Theorists pointed out that our galaxy disappears in

short period if center of galaxy emits so large energy.

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3.Outlines of detectorsFirst generation (room temperature)

University of Maryland (U.S.A.) …

Second generation (4 K)

Explorer (Italy, CERN), Allegro (U.S.A.),

Niobe (Australia), Crab (Japan) …

Third generation (< 100 mK)

Nautilus (Italy), Auriga (Italy),

Mini-Grail (Netherlands),

Mario Schenberg (Brazil) …

This is not a perfect list !

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3.Outlines of detectorsFirst generation (room temperature)

University of Maryland (U.S.A.) …

Second generation (4 K)

Explorer (Italy, CERN), Allegro (U.S.A.),

Niobe (Australia), Crab (Japan) …

Third generation (< 100 mK)

Nautilus (Italy), Auriga (Italy),

Mini-Grail (Netherlands),

Mario Schenberg (Brazil) …

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Exploler

G. Pizzella, ET first general meeting (2008)

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NAUTILUSINFN - LNF

G. Pizzella, ET first general meeting (2008)

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AURIGAPadova

3.Outlines of detectors

G. Pizzella, ET first general meeting (2008)

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3.Outlines of detectorsMario Schenberg

O.D. Aguiar et al., Classical and Quantum Gravity 25 (2008) 114042.

Mini-Grail

http://www.minigrail.nl/

About 3 kHz

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Old but original resonators in Japan (Not bar and sphere)

One of examples : Torsion detector (60 Hz)

Best upper limit of continuous gravitational wave from Crab pulsar h<2*10-22 (Until 2008)T. Suzuki, “Gravitational Wave Experiments”World Scientific p115 (1995).

3.Outlines of detectors

S. Kimura et al., Physics Letters A81 (1981) 302.

“Gravitational wave detection”Kyoto University Press (1998)Fig. 5-6. (Japanese)

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Interferometer (on Earth)Gravitational wave changes length difference of two arms.

3.Outlines of detectors

Frequency : 10 Hz – 10 kHz

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Brief early history of interferometer“300 years of gravitation”(1987) Cambridge University Press

Idea or suggestion F.A.E. Pirani (1956), Gertsenshtein and Pustovoit (1962), J. Weber (mid-1960’s)

Detailed design and feasibility study R. Weiss (1972)

First interferometric detector G.E. Moss, L.R. Miller, R.L. Forward, Applied Optics 10 (1971) 2495.

3.Outlines of detectors

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3.Outlines of detectors

All current interferometers have Fabry-Perot cavities.

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3.Outlines of detectorsFirst generation (Current)

LIGO (U.S.A.), VIRGO (Italy and France),

GEO (Germany and U.K.), TAMA (Japan), CLIO (Japan)

Second generation (Future)

Advanced LIGO, Advanced VIRGO,

AIGO(Australia), LCGT (Japan)

Third generation (Future)

Einstein Telescope (Europe)

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3.Outlines of detectorsSensitivity of interferometer

1st generation (LIGO,VIRGO)

2nd generation

3rd generation

10 times

10 times ?

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3.Outlines of detectorsLIGO (U.S.A.)

4 km, Hanford and Livingston (3000 km distance) (U.S.A.) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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VIRGO (Italy and France)

3.Outlines of detectors

3 km, Pisa (Italy) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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3.Outlines of detectorsGEO (Germany and U.K.)

600 m, Hannover (Germany) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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3.Outlines of detectorsTAMA (Japan)

300 m, Tokyo (Japan) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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3.Outlines of detectors

100 m, Kamioka (Japan) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

CLIO (Japan)

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3.Outlines of detectorsWhat will happen in future ?Before second generation …

GEO-HF (High Frequency)Upgrade of GEO600Observation : 2011-2015

Injection of squeezed light(smaller quantum vacuum fluctuation of light)

H. Lueck et al.,Journal of Physics: Conference Series Coming soon (arXiv:1004.0339).

Henning Vahlbruch et al.,Classical and Quantum Gravity 27 (2010) 084027.(GWIC thesis prize in 2008)

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3.Outlines of detectorsSecond generation Observation : 2015 ? – We can expect first detection !

Advanced LIGO, Advanced VIRGO

Upgrade of LIGO and VIRGO

AIGO (Australia)

Similar to Advanced LIGO

LCGT (Japan)

Cryogenic technique

Underground site (small seismic motion)

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3.Outlines of detectorsAIGO (Australia)

8 km, Perth (Australia) S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

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Location of LCGTLCGT is planed to be built underground at Kamioka, where the prototype CLIO detector is placed.

By K. Kuroda (2009 May Fujihara seminar)

3 km, Kamioka (Japan)

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3.Outlines of detectors

Prototype for LCGT (cryogenic technique, same underground site)

S. Kawamura, Classical and Quantum Gravity 27 (2010) 084001.

CLIO (Japan)

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3.Outlines of detectorsEinstein Telescope (Europe)

30 km vacuum tube in total

Cryogenic technique Underground site (small seismic motion)

Third generation Observation : 2025 ? –

World wide network for GW astronomy

Adv. LIGO (under construction since 2008 ）TAMA/CLIO

LCGT, Budget request

LIGO(I) Hanford

LIGO(I) Livingston

GEO 600

Virgo

AIGO (budget request)

Adv. Virgo (design)

ET (planed)

A network of detectors is indispensable to position the source.

LCGT

By K. Kuroda (2009 May Fujihara seminar)

GEO HF

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3.Outlines of detectors

M. Punturo et al., Classical and Quantum Gravity 27 (2010) 084007.

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4.Recent results in observation

Future interferometers can detect gravitational wave.Current interferometers have never detected !

However, current interferometers have already provided scientific results in astronomy and cosmology.

(1) Gamma ray burst

(2) Crab pulsar

(3) Stochastic background

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4.Recent results in observation

(1) Gamma ray burst

Gamma ray flashes with huge energy

1963 : Vela satellite (U.S.A.) found gamma ray burst.

R. Klebesadel et al., Astrophysical Journal 182 (1973) L85.

Nobody knows what they are and how much distances from Earth are.

Gamma ray bursts appear suddenly and disappear soon.

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4.Recent results in observation

(1) Gamma ray burst

Revolutions in 1997

BeppoSAX (Italy, Netherlands)Wikipedia, English

Identification of optical counterpartMeasurement of distance(order of billion light years !)

J. van Paradijs et al., Nature 386 (1997) 686.D.E. Reichart, Astrophysical Journal 495 (1998) L99.

However, central engine is still unknown.

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4.Recent results in observation

(1) Gamma ray burst

There are two categories.

Long gamma ray burst (more than 2 sec) Short gamma ray burst (less than 2 sec)

Central engine of short gamma ray burst

Compact binary coalescence ?

Neutron star – Neutron star, Black hole – Neutron star

If so, short gamma ray bursts generate gravitational wave !

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4.Recent results in observation

(1) Gamma ray burst

GRB070201 (1 February 2007) Direction : Andromeda galaxy (M31) 0.77Mpc (about 2 million light years)

Only LIGO interferometers were in operation.

B. Abbott et al., Astrophysical Journal 681 (2008) 1419.

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4.Recent results in observation

(1) Gamma ray burst

No signal was found !

This conclusion does not exclude current model in M31.However, some parameter regions are excluded.

If GRB070201 is in M31,

1 solar mass < m1 < 3 solar mass1 solar mass < m2 < 40 solar mass

This parameter region is excludedat >99% confidence.

B. Abbott et al., Astrophysical Journal 681 (2008) 1419.

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4.Recent results in observation

(2) Crab pulsar

Crab nebulaWikipedia, English

Rotating neutron star in Crab nebula (Supernova in 1054)

Spin down : Loss of rotation kinetic energyUpper limit of gravitational wave

Asymmetry of pulsar generates gravitational wave.

h<1.4*10-24

One of the largest upper limits in pulsars

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4.Recent results in observation

(2) Crab pulsar

Crab nebulaWikipedia, English

LIGO interferometers9 months data(Nov. 2005 - Aug. 2006)

h<2.7*10-25

No signal was found !

Upper limit of gravitational wave

Loss due to gravitational wave is less than 4% of total loss.

5 times smaller upper limit than that of spin-down

B. Abbott et al., Astrophysical Journal 683 (2008) L45.

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4.Recent results in observation

(3) Stochastic background

Cosmological stochastic background gravitational wavecould be generated in early universe.

After that, D, He, Li were generated (in first three minutesof universe). We can observe quantity of generated these elements. Their quantities depend on the speed of universe expansion.

If energy density of stochastic background gravitational wave was too much, speed of universe expansion was different from our expectation.

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4.Recent results in observation

(3) Stochastic background

So, energy density of stochastic gravitational wave background (around 100 Hz) must be 1.1*10-5 times smaller than average density of universe.

Big Bang nucleosynthesis

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4.Recent results in observation

(3) Stochastic background

LIGO interferometers : about 2 years data(Nov. 2005 - Sep. 2007)Correlation between 2 interferometers

No correlation was found !

So, energy density of stochastic gravitational wave background (around 100 Hz) must be 6.9*10-6 times smaller than average density of universe.

1.6 times smaller upper limit than that of Big Bang nucleosynthesisSome models of early universe are ruled out.

B.P. Abbott et al., Nature 460 (2009) 990.

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5.Summary Nobody has detected gravitational wave directly.

There are two kinds of motivation for direct detection;

physics and astronomy.

Resonant and interferometric detectors were constructed on Earth and are operated for observation.

Some scientific null results have already been obtained.

In near future, gravitational wave will be detected directly !

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Thank you for your attention !

Vi ringrazio molto per la vostra attenzione !