Gravitational Waves (Working group 6) resonant mass detectors ...
Gravitational Waves (Working group 6) resonant mass detectors: Visco current generation terrestrial interferometers: Frolov, Brady next generation terrestrial interferometers: Adhikari, Owen science fiction terrestrial interferometers: Mavalvala Bruce Allen, UWM Gravitational waves: How are they different? Gravitational waves Couple to mass 4-current Produced by coherent motions of high density or curvature
Wavelengths > source size, like sound waves (no pictures) Propagate through everything, so you see dense centers 8/31/06 Electromagnetic waves Couple to electric 4-current Incoherent superposition of many microscopic emitters Wavelengths source size, can make pictures Stopped by matter, so beauty is skin deep WG6 summary, TEV II
2 Science Goals Direct verification of two dramatic predictions of Einsteins general relativity: gravitational waves & black holes Physics & Astronomy Detailed tests of properties of gravitational waves including speed, polarization, graviton mass, ..... Probe strong field gravity near black holes & in early universe Probe the neutron star equation of state Performing routine astronomical observations A new window on the Universe 8/31/06 WG6 summary, TEV II 3 GW Sources 50-1000 Hz
WG6 summary, TEV II 4 Present performance of resonant mass detectors Massimo Visco INAF IFSI Roma INFN Sez. Roma Tor Vergata 8/31/06 WG6 summary, TEV II 5 International Gravitational Events Collaboration ALLEGRO AURIGA ROG (EXPLORER-NAUTILUS) The oldest resonant detector EXPLORER started operations about 16 years ago. This kind of detector has reached a high level of realibilty. The duty factor is greater than 90% .
A DIRECTIONAL 4-ANTENNAE OBSERVATORY The four antennas are sensitive to the same region of the sky 8/31/06 WG6 summary, TEV II 7 SENSITIVITY OF PRESENT DETECTORS 8/31/06 WG6 summary, TEV II 8 TRIPLE COINCIDENCE DISTRIBUTION AU-EX-NA (PRELIMINARY) NO DETECTIONS
8/31/06 WG6 summary, TEV II 9 2012 - 2018 NETWORK WG6 summary, TEV II -8/31/06 slide from INFN roadmap 10 Status of LIGO Valera Frolov LIGO Lab 8/31/06 WG6 summary, TEV II
11 LIGO Observatories Hanford, WA (H1 4km, H2 2km) - Interferometers are aligned to be as close to parallel to each other as possible - Observing signals in coincidence increases the detection confidence - Determine source location on the sky, propagation speed and polarization of the gravity wave Livingston, LA (L1 4km) 8/31/06 WG6 summary, TEV II 12 Time Line
10-17 10-18 HEPI at LLO 10-20 10-21 S1 S2 at 150 Hz [Hz-1/2] 10-22 S3 Now S4 S5 Runs First
Science Data 200 6 8/31/06 WG6 summary, TEV II 13 NS-NS Inspiral Range Improvement Time progression since the start of S5 Design Goal 8/31/06 Commissioning breaks
Stuck ITMY optic at LLO WG6 summary, TEV II 14 Triple Coincidence Accumulation ~ 61% 100% ~ 45% Expect to collect one year of triple coincidence data by summer-fall 2007 8/31/06 WG6 summary, TEV II 15 LIGO Observational Results
Patrick Brady U. Wisconsin - Milwaukee 8/31/06 WG6 summary, TEV II 16 Bursts Supernovae: Neutron star birth, tumbling and/or convection Cosmic strings, black hole mergers, ..... Coincident EM observations Surprises! 8/31/06 WG6 summary, TEV II 17
Detection Efficiency Evaluate efficiency by adding simulated GW bursts to the data. S4 Detection Efficiency Example waveform Central Frequency S5 sensitivity: minimum detectable in band energy in GW EGW > 1 M @ 75 Mpc EGW > 0.05 M @ 15 Mpc (Virgo cluster)
8/31/06 WG6 summary, TEV II 18 Upper Limits No GW bursts detected through S4 set limit on rate vs signal strength. c Ex lu S1 90 CL S2 %
Lower amplitude limits 8/31/06 from lower detector d Rate Limit (events/day) de Lower rate limits from longer observation times S4 projected S5 projected WG6 summary, TEV II 19
Stochastic Background Big bang & early universe Background of gravitational wave bursts Unresolved background of contemporary sources QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. WMAP 8/31/06 WG6 summary, TEV II 20 Predictions and Limits LIGO S1: 0 < 44 0
Initial LIGO, 1 yr data Expected Sensitivity ~ 4x10-6 -8 -10 Pre-big bang model CMB -12 Inflation -14 Slow-roll -18 -16
8/31/06 -14 -12 -10 Advanced LIGO, 1 yr data EW or SUSY Expected Sensitivity Phase transition ~ 1x10-9 Cyclic model -8 WG6 -6summary, -4 -2 TEV II 0 Log (f [Hz]) 2
4 6 8 1021 Compact Binaries Black holes & neutron stars Inspiral and merger Probe internal structure, populations, & spacetime geometry 8/31/06 WG6 summary, TEV II 22 S5 Search binary neutron star
horizon distance 3 months of S5 analyzed Horizon distance over run versus mass forAverage BBH 130Mpc 1 sigma variation binary black hole horizon distance 8/31/06 WG6 summary, TEV II 23 Image: R. Powell Astrophysical sources of
gravitational waves Spinning neutron stars Isolated neutron stars with mountains or wobbles Low-mass x-ray binaries Probe internal structure and populations 8/31/06 WG6 summary, TEV II 24 Known pulsars S5 preliminary Gravitational-wave amplitude 32 known isolated, 44 in binaries, 30 in globular clusters Lowest ellipticity upper limit: PSR J2124-3358
(fgw = 405.6Hz, r = 0.25kpc) ~2x10 ellipticity = 4.0x10-7 -25 Frequency (Hz) 8/31/06 WG6 summary, TEV II 25 To participate, sign up at http://www.physics2005.org [email protected] Public distributed computing project All-sky, all-frequency search is computationally limited
S3 results: No evidence of pulsars S4 search Post-processing underway 8/31/06 WG6 summary, TEV II 26 Next Generation Interferometers Rana Adhikari Caltech 8/31/06
WG6 summary, TEV II 27 The next several years 4Q 06 4Q 05 S5 4Q 07 4Q 08 ~2 years 4Q 09
4Q 10 Adv S6 LIGO Between now and AdvLIGO, there is some time to improve 1)~Few years of hardware improvements + 1 year of observations. Factor of ~2.5 in noise, factor of ~10 in event rate. 1)3-6 interferometers running in coincidence ! 8/31/06 WG6 summary, TEV II 28 Lower Thermal
Noise Estimate 8/31/06 WG6 summary, TEV II Increased Power + Enhanced Readout 29 Advanced LIGO Design Features 40 KG FUSED SILICA TEST MASSES ACTIVE SEISMIC ISOLATION FUSED SILICA, MULTIPLE
PENDULUM SUSPENSION 180 W LASER, MODULATION SYSTEM PRM BS ITM ETM SRM PD Power Recycling Mirror Beam Splitter Input Test Mass End Test Mass Signal Recycling Mirror Photodiode 8/31/06 WG6 summary, TEV II
30 Advanced LIGO 8/31/06 WG6 summary, TEV II 31 What can gravitational waves tell us about neutron stars? Ben Owen PSU 8/31/06 WG6 summary, TEV II 32 Periodic signals:
Pulsar emission mechanism Pulse profiles in different EM bands illuminate mechanism Profiles show (phase) timing noise, mostly in young pulsars GW wont show interesting pulse profiles (only lowest harmonic detectable) Will be able to test if GW signal has timing noise or not Tells us how magnetosphere is coupled to dense interior (Does B-field structure go all the way in? Just crust? ) 8/31/06
WG6 summary, TEV II 33 Periodic signals: How solid is a neutron star? 8/31/06 NS definitely have (thin) solid crust (known from pulsar glitches) Normal nuclear crusts can only produce ellipticity < few 10-7 If ? is solid quark matter, whole star could be solid, < few 10-4
If ? is quark-baryon mixture or meson condensate, half of core could be solid, < 10-5 High ellipticity measurement means exotic state of matter Low ellipticity is inconclusive: strain, buried B-field WG6 summary, TEV II 34 Burst signals: Supernova core collapse 8/31/06
Burst from collapse and bounce Poorly modeled: different groups predict different waveforms, agree that there is no supernova explosion. Long GRBs: knowing time & location helps GW searches GRB/GW/neutrino relative delays could shed light on explosion mechanism If GW & signals are both short, result is a black hole WG6 summary, TEV II 35 Path to sub-quantum-noise limited gravitational wave interferometers Nergis Mavalvala
MIT 8/31/06 WG6 summary, TEV II 36 Optical Noise Shot Noise Uncertainty in number of photons detected h( f Higher circulating power Pbs low optical losses Frequency dependence light (GW signal) storage time in the interferometer )
1 Pbs Radiation Pressure Noise Photons impart momentum to cavity mirrors Fluctuations in number of photons Lower power, Pbs Frequency dependence response of mass to forces Optimal input power depends on frequency 8/31/06 WG6 summary, TEV II h( f ) Pbs 2 4 M f
37 A Quantum Limited Interferometer Input laser power > 100 W Q ua n tu m LIGO I Circulating power > 0.5 MW n si o en
sp l Su rma the 8/31/06 ic Seism Mirror mass 40 kg Ad LIGO WG6 summary, TEV II Tes t ther mass m al 38
Squeezed input vacuum state in Michelson Interferometer Consider GW signal in the phase quadrature Not true for all interferometer configurations Detuned signal recycled interferometer GW signal in both quadratures Laser X X++ X X+ 8/31/06 Orient squeezed state to reduce noise in
phase quadrature WG6 summary, TEV II 39 Squeezed vacuum states for GW detectors Requirements Squeezing at low frequencies (within GW band) Frequency-dependent squeeze angle Increased levels of squeezing Long-term stable operation Generation methods Non-linear optical media ((2) and (3) non-linearites) crystal-based squeezing Radiation pressure effects in interferometers
ponderomotive squeezing 8/31/06 WG6 summary, TEV II 40 Squeezed Vacuum 8/31/06 WG6 summary, TEV II 41 Noise budget 8/31/06 WG6 summary, TEV II 42
Conclusions Resonant bar detectors are operating in a stable mode but at low sensitivity compared with LIGO is currently carrying out a science run at design sensitivity. Searches for all major categories of sources are underway and will at least set upper limits. Detections are possible! Enhancements in ~ 3 years will increase the reach by a factor of 3 An upgrade (Advanced LIGO) is planned early next decade Detections are guaranteed Quantum non-demolition techniques needed to beat quantum limits (squeezed light) 8/31/06 WG6 summary, TEV II 43
Looking ahead Market making system League table Tender arrangements Uniform-price auction Length of the yield curve Number of EFN issues EFN futures market Electronic trading platform Conclusion The Hong Kong bond market has grown steadily since crisis Structure of financing...
Fourier Transform We want to understand the frequency w of our signal. So, let's reparametrize the signal by w instead of x: f(x) F(w) Fourier Transform F(w) f(x) Inverse Fourier Transform For every w from 0 to inf, F(w) holds...
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