Gravitational wave detection experiments; Current status ...home.kias.re.kr/MKG/upload/Joint...
Transcript of Gravitational wave detection experiments; Current status ...home.kias.re.kr/MKG/upload/Joint...
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Gravitational wave detection experiments; Current status and Korean activities
Gungwon Kang (KISTI)
Jan. 30, 2015 at Joint Winter Conference on Particle, String and Cosmology in High1, Korea
Gungwon Kang (KISTI)
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OutlineI. IntroductionII. Detection experiments for GWsIII. Korean activitiesIV. Conclusion
I. IntroductionII. Detection experiments for GWsIII. Korean activitiesIV. Conclusion
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I. Introduction1. Gravitational waves:
– Ripples in the spacetime curvature that propagate with the speed of light
– Emitted by “accelerated” matter as in the case of EM waves by an accelerated charge
1. Gravitational waves:– Ripples in the spacetime curvature that
propagate with the speed of light– Emitted by “accelerated” matter as in the
case of EM waves by an accelerated charge
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– In weak gravitational fields, one may have
the linearized Einstein gravity gives
– Defining with the Lorenz guage ,
è Wave eq.: Massless, propagating at the speed of light, spin-2 fields, only two-degrees of freedom, etc.
è Wave eq.: Massless, propagating at the speed of light, spin-2 fields, only two-degrees of freedom, etc.
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– Plane waves propagating in the z-direction, in TT (Transverse-Traceless) gauge,:
“Plus” (+) polarization“Plus” (+) polarization
“Cross” (x) polarization
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– In a more general context, e.g., GWs propagating through curved ST,
Isaacson (‘68)
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– GWs carry energy, angular momentum and momentum:
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2. GW sources:
So, extremely weak for most cases!
• Laboratory generation of GWs:
Ex). A rotating dumbbell consisting of two masses (1ton, 2m & 1kHz) produces
R ~ λ = 300km èR ~ λ = 300km è
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Ex). From particle accelerators, e.g., LHC,
where
for
In the LHC, v~0.999999991 and 10^11 protons per bunch è h ~ 10^-43 !!
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• Astrophysical sources of GWs, e.g., binary,:
~ 4km (~ ),
r ~ 200km & R ~ 200Mpc è h ~
Ex). Neutron star binary
Ex). Black hole binary
è
Ex). Black hole binary
( ≫ ~10^-40)
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L ~ L0 +1/2 h L0
ΔL ~ h L0 ~ 10^-21 x 6400km x 2 ~ 10^-14m ~ size of nucleon
Much better, but still extremely hard to detect even for ASs!!
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Credit courtesy: Patrick Brady
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• Bandwidths and significances of sources: (Cutler & Thorne ‘02)
- Extremely Low Freq. band (ELF, 10^-15~10^-18Hz):- Primordial GWs- Imprint on the polarization of CMB radiations- Quantum origin at big bang subsequently amplified by inflation- Great potential for probing the physics of inflation
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- VLF band (10^-7~10^-9Hz):- Emitted by pulsars (e.g., Hulse-Taylor ‘75)- via pulsar timing array, or indirectly by pulses at earth- Extremely massive BH binary or violent processes in 0.1 second of
the early universe
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- LF band (10^-4~0.1Hz):- From massive (10^5~10^7M⊙) BH binaries out to cosmological
distances (CD)- From small BHs, NSs and WDs spiraling into massive BHs out to
CDs- From orbital motions of WDB, NSB, and stellar-mass BHB in our
own galaxy- And possibly from violent processes in the very early universe- To be observed by the space-based detector, LISA
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- HF band (10~10^3Hz):- From a spinning slightly deformed NS in our Milky Way galaxy- From a variety of sources in the more distance:
- Final inspiral and collisions of NSB and stellar-mass BHB (up to ~100M⊙)
- Tearing apart of a NS by a companion BH- Supernovae, Triggers of GRBs, etc.
- To be measured by earth-based detectors such as LIGO, Virgo, KAGRA, and resonant-mass bar
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II. Detection experiments for GWs1. Brief history:
– GW is predicted even before the full formulation of GR.– It was J. Weber (‘63) who tried for the first time the detection
experiment by using a resonant-mass cylindrical bar at 1660Hz.– It was very sensitive h~10^-16, but still far from ~10^-22.
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– To overcome this gap (~10^6) interferometric detectors have been developed since ‘70.
– LIGO (Laser Interferometer Gravitational-wave Observatory) performed its first operation, S1, in 2002, and achieved its designed sensitivity at S6 in 2010.
– Other GW detectors: Virgo, GEO, KAGRA (in construction), InLIGO(in plan).
– There has been no GW signal detected so far.– LIGO has been upgraded to have a better sensitivity of ~10 times,
and this advanced one (aLIGO) will be in operation in 2015.
– To overcome this gap (~10^6) interferometric detectors have been developed since ‘70.
– LIGO (Laser Interferometer Gravitational-wave Observatory) performed its first operation, S1, in 2002, and achieved its designed sensitivity at S6 in 2010.
– Other GW detectors: Virgo, GEO, KAGRA (in construction), InLIGO(in plan).
– There has been no GW signal detected so far.– LIGO has been upgraded to have a better sensitivity of ~10 times,
and this advanced one (aLIGO) will be in operation in 2015.
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2. Indirect detections:– Ex) Period change in a binary pulsar
Ø P ~ 8hr and e ~ 0.6
Ø Effect of Gravitational Wave Radiation
Ø 1993 Nobel Prize
PSR1913+16 Hulse & Taylor (1974)
Ø P ~ 8hr and e ~ 0.6
Ø Effect of Gravitational Wave Radiation
Ø 1993 Nobel Prize
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– Ex) Imprints of primordial GWs
BICEP2 (2014)
“PRL (’14)”
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3. Interferometric detector:
• Principles:- Measure the change of lengths by using a
Michelson-type interferometer:
è
- Isn’t the light itself stretched as well due to passages of GWs?è Co-expansion of the arms and of the light wave!è The interferometer really works?
• Principles:- Measure the change of lengths by using a
Michelson-type interferometer:
è
- Isn’t the light itself stretched as well due to passages of GWs?è Co-expansion of the arms and of the light wave!è The interferometer really works?
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- In the TT gauge and geometric optics,
: slowly varying amplitude, : rapidly varying phase
Note that mirrors and BS do not move!
- How does light interact with GWs?
è
w/
è
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- The solutions for the outwards and backwards from the beam splitter are, respectively,
ü Therefore, we see an intensity modulation directly proportional to the GW perturbation!!
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• Detector networks: LIGO, Virgo, GEO, KAGRA, InLIGO
4km
LIGO Livingston Obs. (LLO)
- The initial LIGO performed 6 science runs: S1 (2002) ~ S6 (2010)- It has been upgraded since then: Advanced LIGO (aLIGO)- aLIGO will have 10 times better sensitivity, and start to run in 2015 or 2016.
LIGO Livingston Obs. (LLO)
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• Sensitivities and event rates :
- Achieved the designed sensitivity in S5, 2009
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- Event rate of the initial LIGO: ~ 1 per 100 years for NS binaries
Credit courtesy: Patrick Brady
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• Current status of aLIGO:
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Commissioning focus for the first Observational Run
q Target sensitivityØ Binary neutron star coalescence range of 40-80 Mpc, each
detectorØ Important frequency band: 20—300 HzØ Input laser power: 25 W
q Nominal durationØ 3 months
q Run startØ Some time in 2015, perhaps mid-2015
G1401078-v1 28
q Target sensitivityØ Binary neutron star coalescence range of 40-80 Mpc, each
detectorØ Important frequency band: 20—300 HzØ Input laser power: 25 W
q Nominal durationØ 3 months
q Run startØ Some time in 2015, perhaps mid-2015
Credit courtesy: Peter Fritschel, Stanford LVC (2014.08.27)
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Credit courtesy: Patrick Brady
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LOSC S5 data release§ The LIGO S5 strain data is now in public release : losc.ligo.org§ LOSC = LIGO Open Science Center
A. Weinstein at LVC Stanford Meeting on Aug 28, 2014
G1400828 - LOSC for LSC ExecComm 30
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III. Korean activities on GW physics• Brief history:
– Some activities such as workshops and summer schools on numerical relativity and GWs starting from 2003
– 2008.09: Korean Gravitational Wave Group (KGWG) founded– 2009: Visit to LSU and UWM and series of meetings– 2010: Joined LSC (LIGO Scientific Collaboration)– 2012: Collaborations with KAGRA began– 2013: Bidding to host 11th Amaldi Conference on GWs approved
(2015.06.21~26 at Gwangju). 1st paper and 1st PhD in GW data analysis appeared
• Brief history:– Some activities such as workshops and summer schools on
numerical relativity and GWs starting from 2003 – 2008.09: Korean Gravitational Wave Group (KGWG) founded– 2009: Visit to LSU and UWM and series of meetings– 2010: Joined LSC (LIGO Scientific Collaboration)– 2012: Collaborations with KAGRA began– 2013: Bidding to host 11th Amaldi Conference on GWs approved
(2015.06.21~26 at Gwangju). 1st paper and 1st PhD in GW data analysis appeared
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• KGWG organization:- Members from 2 National insts and 9 Universities- LIGO: Four (6) faculty/staff, 3 postdocs, 4 PhD students,
5 technical staff, and supporting members. - KAGRA: ~17 members (7 co-members of LSC)- Group leader: Hyung Mok Lee at SNU
KGWG
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• KGWG activities:- LIGO: Data analyses. KAGRA: Data analysis + Instrumentation- CBC, AuxMVC, PE (Markov-Chain Monte Carlo Analysis of GW
signals), G-ray burst search, ANN, etc- Teleconferences per week and F2F meetings per month- Summer school on NR and GWs
And several more papers
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• KISTI GSDC LDG (LIGO Data Grid):- Computing environment for GW data analyses- KISTI established a Tier 3 center for it.- 35 nodes (420CPUs) and 152TBs- LIGO & Virgo data stored and analysis pipeline softwares
installed- 124TBs of LIGO/Virgo data stored
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- System architecture of KISTI LDG T3
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- Configuration of computing resources in the KISTI LDG T3
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- Descriptions of data stored
0
200
400
600
800
1000
1200
1400
1월 2월 3월 4월 5월 6월 7월 8월 9월 10월
2014 LIGO Job Count
월별
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• Numerical relativity in Korea:- Topics: black holes, Neutron stars, Equilibrium stars and
perturbations, Scalar field dark matter model, Core collapse, etc.- Members: G. Kang, J. Hansen (KISTI), C. Park (KAIST & KISTI), Y.
Bae (SNU & KISTI), H. Kim (SNU), M. Wan (APCTP), J. Kim (Notre Dame U.), S. Lim (KNU), D. Park (APCTP), C. Cho (KASI)
- Collaborators: P. Diener, F. Loeffler (LSU), M. Shibata (YITP), ……
bmax
bmax
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IV. Conclusion• Summary
– I have reviewed a definition of GWs, GW spectrum,astronomical sources, physical significances, detectionexperiment, its principle, etc.
– Current status of aLIGO and Korean activities are reportedbriefly.
– First direct detection of GWs is anticipated in (very) soon!
EM waves• Theory: Maxwell (1864)
• Detection: H. Hertz (1886)
Gravitational waves• Theory: Einstein (1915)
• Detection: Not yet
Hulse & Taylor
(1975)
Weber (1960)
LIGO (?)
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• Prospects– Rich sciences to investigate through GWs; A
new window to our universe; “GW astronomy”
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?Gravitational wave (LIGO)Gravitational wave (LIGO)
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• Prospects– Next generation detectors: Other freq. band, Lab-
size detector, Use of quantum effect, etc.
– Hint at quantum gravity– Urgent request: Human and monetary resources– Pay your attention to this new frontier!