From Einstein to Gravitational Waves and Beyond Barry C Barish - - PowerPoint PPT Presentation

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From Einstein to Gravitational Waves and Beyond Barry C Barish - - PowerPoint PPT Presentation

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From Einstein to Gravitational Waves and Beyond Barry C Barish Caltech Workshop on Kamioka Underground Physics Okayama University 23-May-2017 LIGO-G1700695 for the LIGO Scientific Collaboration and Virgo Collaboration 100 Years Ago

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LIGO-G1700695

From Einstein to Gravitational Waves and Beyond …

Barry C Barish Caltech

Workshop on Kamioka Underground Physics Okayama University 23-May-2017

for the LIGO Scientific Collaboration and Virgo Collaboration

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LIGO-G1700695

100 Years Ago -- 1916

Einstein Predicted Gravitational Waves

  • 1st publication indicating the existence of gravitational

waves by Einstein in 1916

  • Contained errors relating wave amplitude to source motions
  • 1918 paper corrected earlier errors (factor of 2), and it contains the

quadrupole formula for radiating source

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BUT, the effect is incredibly small

  • Consider ~30 solar mass

binary Merging Black Holes – M = 30 M R = 100 km f = 100 Hz r = 3 1024 m (500 Mpc)

Credit: T. Strohmayer and D. Berry

21 4 2 2 2

10 ~ 4 /

    h r c f GMR L L h

  • rb

23-May-2017 Workshop on Kamioka Underground Physics 3

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Emission of Gravitational Waves

23-May-2017 Workshop on Kamioka Underground Physics 4

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SLIDE 5

23-May-2017 Workshop on Kamioka Underground Physics 5

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6

Compact Binary Collisions

– Neutron Star – Neutron Star

  • waveforms are well described

– Black Hole – Black Hole

  • Numerical Relativity waveforms

– Search: matched templates

“chirps”

23-May-2017 Workshop on Kamioka Underground Physics

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SLIDE 7

hg

September 14, 2015 Observed Signals – Sept 14, 2015

7 23-May-2017 Workshop on Kamioka Underground Physics

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SLIDE 8

8

Einstein’s Theory of Gravitation

Gravitational Waves

) 1 (

2 2 2 2

    



h t c

  • Using Minkowski metric, the information about space-

time curvature is contained in the metric as an added term, h. In the weak field limit, the equation can be described with linear equations. If the choice of gauge is the transverse traceless gauge the formulation becomes a familiar wave equation

) / ( ) / ( c z t h c z t h h

x

   

 

  • The strain h takes the form of a plane wave

propagating at the speed of light (c).

  • Since gravity is spin 2, the waves have two

components, but rotated by 450 instead of 900 from each other.

23-May-2017 Workshop on Kamioka Underground Physics

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Gravitational waves

  • Predicted by Einstein’s theory of

General Relativity

  • Ripples of spacetime that stretch and

compress spacetime itself

  • The amplitude of the wave is h ≈ 10-21
  • Change the distance between masses

that are free to move by ΔL = h x L

  • Spacetime is “stiff” so changes in

distance are very small

L Δ L

23-May-2017 9 Workshop on Kamioka Underground Physics

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Suspended Mass Interferometry

23-May-2017 10 Workshop on Kamioka Underground Physics

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Siting LIGO

LIGO Sites

23-May-2017 11 Workshop on Kamioka Underground Physics

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LIGO Construction Began in 1994

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Hanford, WA Livingston, LA

LIGO Interferometers

23-May-2017 Workshop on Kamioka Underground Physics 13

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LIGO

LIGO Infrastructure beam tube

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SLIDE 15

23-May-2017 Workshop on Kamioka Underground Physics 15

LIGO Interferometer Infrastructure

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Interferometer Noise Limits

Thermal (Brownian) Noise

LASER test mass (mirror) Beam splitter

Residual gas scattering

Wavelength & amplitude fluctuations

photodiode

Seismic Noise Quantum Noise "Shot" noise Radiation pressure 23-May-2017 16 Workshop on Kamioka Underground Physics

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  • What Limits

LIGO Sensitivity?

  • Seismic noise limits low

frequencies

  • Thermal Noise limits middle

frequencies

  • Quantum nature of light

(Shot Noise) limits high frequencies

  • Technical issues - alignment,

electronics, acoustics, etc limit us before we reach these design goals

23-May-2017 Workshop on Kamioka Underground Physics 17

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Evolution of LIGO Sensitivity

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Initial LIGO Performance (Final)

23-May-2017 19 Workshop on Kamioka Underground Physics

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LIGO-G1700695

Better seismic isolation Higher power laser Better test masses and suspension

Advanced LIGO GOALS GO G

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  • 21

How to obtain a x10 sensitivity improvement?

EO M

Laser

Parameter Initial LIGO Advanced LIGO Input Laser Power 10 W (10 kW arm) 180 W (>700 kW arm) Mirror Mass 10 kg 40 kg Interferometer Topology Power-recycled Fabry-Perot arm cavity Michelson Dual-recycled Fabry-Perot arm cavity Michelson (stable recycling cavities) GW Readout Method RF heterodyne DC homodyne Optimal Strain Sensitivity 3 x 10-23 / rHz Tunable, better than 5 x 10-24 / rHz in broadband Seismic Isolation Performance flow ~ 50 Hz flow ~ 13 Hz Mirror Suspensions Single Pendulum Quadruple pendulum

23-May-2017 Workshop on Kamioka Underground Physics

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  • Mechanical requirements: bulk and coating

thermal noise, high resonant frequency

  • Optical requirements: figure, scatter,

homogeneity, bulk and coating absorption

Mirror / Test Masses

Test Masses: 34cm  x 20cm 40 kg 40 kg BS: 37cm  x 6cm ITM T = 1.4% Round-trip

  • ptical loss: 75

ppm max Compensation plates: 34cm  x 10cm

Workshop on Kamioka Underground Physics 22 23-May-2017

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23-May-2017

Seismic Isolation

suspension system

  • support structure is welded tubular

stainless steel

  • suspension wire is 0.31 mm

diameter steel music wire

  • fundamental violin mode frequency
  • f 340 Hz

suspension assembly for a core optic

23 Workshop on Kamioka Underground Physics

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Optics Table Interface (Seismic Isolation System) Damping Controls Electrostatic Actuation Hierarchical Global Controls

Test Mass Quadruple Pendulum Suspension

Final elements All Fused silica

23-May-2017 24 Workshop on Kamioka Underground Physics

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Constrained Layer damped spring

23-May-2017

Passive Seismic Isolation

Initial ILIGO

25 Workshop on Kamioka Underground Physics

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SLIDE 26

23-May-2017 26

Virgo Seismic Performance

Workshop on Kamioka Underground Physics

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Seismic Isolation Passive / Active Multi-Stage

Workshop on Kamioka Underground Physics 27 23-May-2017

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200W Nd:YAG laser

Designed and contributed by Max Planck Albert Einstein Institute

  • Stabilized in power and frequency
  • Uses a monolithic master oscillator

followed by injection-locked rod amplifier

23-May-2017 Workshop on Kamioka Underground Physics 28

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Sensitivity for first Observing run

Initial LIGO O1 aLIGO Design aLIGO

Broadband, Factor ~3 improvement At ~40 Hz, Factor ~100 improvement

23-May-2017 Workshop on Kamioka Underground Physics 29

  • Phys. Rev. D 93, 112004 (2016
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Gravitational Wave Event

GW150914

Data bandpass filtered between 35 Hz and 350 Hz Time difference 6.9 ms with Livingston first Second row – calculated GW strain using Numerical Relativity Waveforms for quoted parameters compared to reconstructed waveforms (Shaded) Third Row –residuals bottom row – time frequency plot showing frequency increases with time (chirp)

23-May-2017

  • Phys. Rev. Lett. 116, 061102 (2016)

30 Workshop on Kamioka Underground Physics

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GW151226 GW150914

23-May-2017 31 Workshop on Kamioka Underground Physics

Black Hole Merger Events and Low Frequency Sensitivity

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Sensitivity of Initial LIGO-Virgo

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Astrophys.J. 760 (2012) 12 arXiv:1205.2216 [astro-ph.HE] LIGO-P1000121

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Statistical Significance of GW150914

Binary Coalescence Search

23-May-2017 Workshop on Kamioka Underground Physics

  • Phys. Rev. Lett. 116, 061102 (2016)

33

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Black Hole Merger: GW150914

Full bandwidth waveforms without filtering. Numerical relativity models of black hole horizons during coalescence Effective black hole separation in units of Schwarzschild radius (Rs=2GMf / c2); and effective relative velocities given by post- Newtonian parameter v/c = (GMf f/c3)1/3

23-May-2017

  • Phys. Rev. Lett. 116, 061102 (2016)

34 Workshop on Kamioka Underground Physics

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Measuring the parameters

  • Orbits decay due to emission of gravitational waves

– Leading order determined by “chirp mass” – Next orders allow for measurement of mass ratio and spins – We directly measure the red-shifted masses (1+z) m – Amplitude inversely proportional to luminosity distance

  • Orbital precession occurs when spins are misaligned with orbital

angular momentum – no evidence for precession.

  • Sky location, distance, binary orientation information extracted from

time-delays and differences in observed amplitude and phase in the detectors

23-May-2017 Workshop on Kamioka Underground Physics 35

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  • Use numerical simulations fits of black hole

merger to determine parameters; determine total energy radiated in gravitational waves is 3.0±0.5 Mo c2 . The system reached a peak ~3.6 x1056 ergs, and the spin of the final black hole < 0.7 (not maximal spin)

Black Hole Merger Parameters for GW150914

23-May-2017

  • Phys. Rev. Lett. 116, 061102 (2016)
  • Phys. Rev. Lett. 116, 241102 (2016)

36 Workshop on Kamioka Underground Physics

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More Events?

Image credit: LIGO 37 23-May-2017 Workshop on Kamioka Underground Physics

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Finding a weak signal in noise

  • “Matched filtering” lets us find a weak signal

submerged in noise.

  • For calculated signal waveforms, multiply the

waveform by the data

  • Find signal from cumulative signal/noise

38

  • PHYS. REV. X 6,041015 (2016)
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GW151226 – Matched Filter

23-May-2017 39 Workshop on Kamioka Underground Physics

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Second Event, Plus another Candidate

Sept 2015 – Jan 2016 (4 months) 23-May-2017 40

  • PHYS. REV. X 6,041015 (2016)

Workshop on Kamioka Underground Physics

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Sensitivity

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Lessons from LIGO O1

  • Steep drop in false alarm

rate versus size means edge

  • f observable space is very

sharp

» Very far out on tail of noise due to need to overcome trials factor O1 BBH Search

23-May-2017 Workshop on Kamioka Underground Physics

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“Second Event” Inspiral and Merger GW151226

  • Phys. Rev. Lett. 116, 241103 (2016)

23-May-2017 42 Workshop on Kamioka Underground Physics

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Final Black Hole Masses, Spins and Distance

23-May-2017 Workshop on Kamioka Underground Physics 43

  • PHYS. REV. X 6,041015 (2016)
  • PHYS. REV. X 6,041015 (2016)
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New Astrophysics

  • Stellar binary black holes

exist

  • They form into binary

pairs

  • They merge within the

lifetime of the universe

  • The masses (M > 20 M☉) are

much larger than what was known about stellar mass Black Holes.

23-May-2017 Image credit: LIGO 44 Workshop on Kamioka Underground Physics

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Testing General Relativity

  • We examined the detailed waveform of GW150914 in several ways to see

whether there is any deviation from the GR predictions

– Known through post-Newtonian (analytical expansion)and numerical relativity

  • Inspiral / merger / ringdown consistency test

– Compare estimates of mass and spin from before vs. after merger

  • Pure ringdown of final BH?

– Not clear in data, but consistent

PRL 116, 221101 (2016)

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Testing General Relativity – Both Events

23-May-2017 46 Workshop on Kamioka Underground Physics

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Testing General Relativity

graviton mass

If v GW < c , gravitational waves then have a modified dispersion relation. There is no evidence of a modified inspiral

LIMIT 90% Confidence

  • Phys. Rev. Lett. 116, 221102 (2016)

47 23-May-2017 Workshop on Kamioka Underground Physics

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LIGO O2 Observational Run Underway

23-May-2017 Workshop on Kamioka Underground Physics 48

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LIGO-Virgo Observing Plans

Workshop on Kamioka Underground Physics

LIGO Virgo

49

Living Rev. Relativity 19 (2016), 1

23-May-2017

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Black Hole Binary Rate expectations

future running

Black Hole Binaries Probability of observing

  • N > 10
  • N > 35
  • N > 70 events
  • highly significant

events, as a function

  • f surveyed time-

volume.

2016-17 2015

23-May-2017 50

  • Phys. Rev. X 6, 041015 (2016)

Workshop on Kamioka Underground Physics

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  • Left – Comparison of BNS merger rates and O1 low spin exclusion region (blue)
  • Right – Comparison of NSBH merger rates and O1 exclusion regions for 10-1.4 Solar masses (blues)

51

Predicted Rates BNS and NSBH merger

arXiv:1607.07456

23-May-2017 Workshop on Kamioka Underground Physics

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Workshop on Kamioka Underground Physics

52

  • LIGO detectors are nearly omni-

directional

– Individually they provide almost no directional information

  • Array working together can

determine source location

– Analogous to “aperture synthesis” in radio astronomy

Source Localization Using Time-of-flight

D t = (D cos q)/c

1

q

22

  • Accuracy tied to diffraction limit

23-May-2017

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Comparing time of arrival and amplitude

GW150914: Signal arrived 6.9 milliseconds earlier in LIGO Livingston, LA than LIGO Hanford, WA

23-May-2017 Image credit: LIGO/Axel Mellinger 53 Workshop on Kamioka Underground Physics

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54

GW detector network: 2015-2025

GEO600 (HF) 2011 Advanced LIGO Hanford 2015 Advanced LIGO Livingston 2015 Advanced Virgo 2016 LIGO-India 2022 KAGRA 2017

23-May-2017 Workshop on Kamioka Underground Physics 54

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Improving Localization

2016-17 2017- 18 2019+ 2024

23-May-2017 Workshop on Kamioka Underground Physics 55 LIGO-P1200087-v32 (Public)

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Thanks!

23-May-2017 Workshop on Kamioka Underground Physics 56