gravitational antennae for probing the dark side of the...
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Gravitational Antennae for Probing the Dark Side of the Universe
Rana X Adhikari (Caltech)
Gravitational Waves
Einstein’s Equations:When matter moves, or changes its configuration, its gravitational
field changes. This change propagates outward asa ripple in the curvature of space-time: a gravitational wave.
“Mass tells space-time how to curve,and space-time tells mass how to move.”
--- John Wheeler
NASA/Dana Berry, Sky Works Digital
Gµ⌫ = 8⇡G
c4Tµ⌫
10�43
q Gravitational Waves = “Ripples in space-time”q Two transverse polarizations - quadrupolar: + and x
Gravitational Waves:
GW amplitude is a strain: ∆L / L ∆L = strain x L
we need a large L !
q Compact binary inspirals: “chirp”Ø NS-NS waveforms are well described. R ~ 300 Mpc Ø inspiral is a standard candle.Ø BH-BH merger simulations exist! R ~ 1500 Mpc
q Supernovae / Mergers: “burst” Ø Short signals. Waveforms not well known.Ø Search in coincidence between two or more interferometers and possibly
with electromagnetic and/or neutrinos signals. R ~ 0.03 Mpc
q Spinning NS: “continuous”Ø search for signals from observed pulsars R ~ 0.1 Mpc Ø all-sky search computing challenging R ~ 0.01 Mpc
q Cosmic Background: “stochastic”Ø Metric fluctuations amplified by inflation, phase transitions in early universe,
topological defects too weak to measure (on the earth)Ø Unresolved background sources (BH/BH mergers)
GW Sources in LIGO Band 10 - 5000
Caltech/Cornell - SXS
Adam Burrows
Timeline of the GW Field1. GR 1915 2. Einstein 1916 3. Einstein 1918 4. Chapel Hill (1957) 5. Pirani 6. Gertenstein & Pustovit 7. PPN Formalism 8. Thorne 1968 - 2014 9. Chandrasekhar &
Detweiler (1975) 10.Pretorius (2005)
1. Michelson (1881) 2. Weber (1965) 3. Weiss 1971 4. 1987 LIGO Proposal 5. MIT 1-5m 1982-1998 6. CIT 40m 1981-> 7. iLIGO 1997 - 2007 8. eLIGO 2007 - 2010 9. aLIGO 2010 -> 10.First lock 5/2014 11.O1 start 9/2015 12. GW150914
How the Michelson Interferometer Works:
Mirror motion -> Optical Phase -> Light Power
The Michelson Interferometer
Anti-Symmetric (Dark) Port
Ly
LxReflected Port
P ∝ PBS x sin2(ϕ)
dP/dϕ ∝ PBS x sin(ϕ)cos(ϕ)
ϕ = 2π (δLy - δLx) / λdϕ/dh ∝ L
Laser
Phase Shift ∝ Length
Signal ∝ BS Power
BS
dP ∝ sqrt(P)Shot Noise
Poisson Statistics...
200 WLASER
!m
EndTestMass
T = 5 ppm
InputTestMass
T = 1.4%PowerRecycling
MirrorT = 3%
Beam-Splitter Pcav = 800 kW
3995 mSignalRecycling
MirrorT = 20%
100 kW
22 W
T = 30%
Photodetector
BeamSplitter
Power Recycling
Laser
Source100 kW Circulating Power
b)
a)
Signal Recycling
Test Mass
Test Mass
Test Mass
Test Mass
Lx = 4 km
20 W
H1
L1
10 ms light
travel time
L y =
4 k
m
c
c
cw
wp
p
p
p
p
w
Sep. 14 th
LIGO Hanford Control Room
Phys. Rev. Lett. 116, 061102
shifted by 7.3 ms
Numerical Sim of the merger on a bright background
SXS collaboration
More Quantitative Simulation
What do the colors and arrows represent?
Detweiler & Chandrasekhar
(1975)
fring ' 32 kHz
✓M�M
◆h1� 0.63(1� a)3/10
i
Qring ' 2p1� a
GW150914 Baseball Cardm1= 36; m2 = 29
mfinal = 62; spin = 0.67
distance = 410 Mpc; z ~ 0.09
EGW = 3 M; Lpeak ~ 3x1049 W (1023 suns)
Public data release: https://losc.ligo.org/events/GW150914/
Christmas Night
KAGRA..
LIGO India
some interesting topicsthe next decade of LIGO upgrades
Quantum Revolution ‘15
mirrors with “no” thermal noise
new Indian LIGO
Mystery Noise ?
Deep Learning for technical noise regression
direct dark matter detection with LIGO
tests of emergent gravity
short, space interferometer for cosmography (in prep.)
https://arxiv.org/abs/1605.01103
https://arxiv.org/abs/1504.02545
What’s next for LIGO?2016: increase laser power, reduce low frequency noise
take ~6 months of data
2017: install squeezed light system
2019: improved mirrors
2025: Cryogenic silicon mirrors
~2030-2035: New (40 km) Facility
Vacuum Fluctuationsof EM Field
Radiation Pressure -- Photon Fluctuations
Residual Gas➢ random phase fluctuations
ThermodynamicMirror SurfaceFluctuations
Seismic/Gravitational
Vibrations
GW Readout
Laser
Shot Noise --Photon Fluctuations
Calculated LIGO Noise Anatomy
Newtonian gravity noise (a.k.a. Gravity Gradients)
Filtered Seismic
Glass Suspension Thermal Noise
Mirror Coating Thermal Noise
Quantum Noise: Radiation Pressure / Shot Noise
initial LIGO (2007)
Advanced LIGO
estimated Noise Budget (Louisiana, Feb. 2016)
“mystery” noise
Where do we come from?What are we?Where are we going? -- Paul Gauguin
How can we eat?Why do we eat?Where shall we have lunch? -- Douglas Adams
Ira Thorpe
What’s next for LIGO?2016: increase laser power, reduce low frequency noise
take ~6 months of data
2017: install squeezed light system
2019: improved mirrors
2025: Cryogenic silicon mirrors
~2030-2035: New (40 km) Facility
Frequency [Hz]10
110
210
3
Str
ain
[1/
Hz]
10-24
10-23
10-22
cre
ate
d u
sin
g g
win
c.m
on
31-J
an
-2016 b
y r
an
a o
n S
ilver7
80.lo
cal
Adv LIGO
A+
Quantum: Pin = 145 W; ζsqz = 10 dBSeismic: aLIGONewtonian Gravity: 10x subtractionSusp Thermal: 123 K Si blades and ribbonsCoat Brown: α− Si : SiO2 Φcoat = 6.5e-05Coating ThermoOptic: ωbeam = 5.9 8.4 cmSub Brown: Si mirror (T = 123 K, mmirror = 204 kg)Residual Gas: 3 nTorr of H2
Sub Thermo-RefractiveCarrier Density: 1013/cm3
Total
Sep 2015
Total Mass (M⊙)101 102 103
Redshift
10-1
100
101
Redshift v. Black Hole mass for LIGO Voyager
Cryo LIGOAdv LIGO
Our view of the Universe (circa 1998)
Fermi / 1 GeV (2012)
PlanckHFI/LFI (2010)
– James T. Kirk
“Space, the Final Frontier”
Why Space?
Earth based detectors limited by seismic / gravity noise below ~5 Hz. Enormous challenges going to 1 Hz or below (cf. MANGO report: http://arxiv.org/abs/1308.2074)
Strain Sensitivity ~1/Larm. Hard to beat 100 km on Earth (cf. LUNGO report http://arxiv.org/abs/1410.0612)
Different astrophysical signals at low frequencies: massive black holes, white dwarf binaries (cf. numerous LISA science case reports, as well as BBO & DECIGO)
[1] C. Cutler and D. E. Holz, Physical Review D 80, 104009 (2009) [2] L. Randall and G. Servant, arXiv hep-ph, (2006). [3] K. Yagi and T. Tanaka, arXiv gr-qc, (2009).
Why NOT Space?Its expensive: 1000-2000 M$ for LISA. ~5000 M$ for JWST.
There’s no parts replacement in space: if the suspensions or lasers break, its game over.
It takes FOREVER: LISA concept started ~1975. As of 2014, the earliest launch would be in 2034.
except: Hubble mirror spherical aberration
Space Detectors
LISA, NGO, eLISA, SGO
BBO
DECIGO
AGIS
LAGRANGE(s)
OMEGA
http://pcos.gsfc.nasa.gov/studies/gravitational-wave-mission.phpRFI in 2011, Workshop in early 2012
10−4
10−3
10−2
10−1
100
101
10−25
10−24
10−23
10−22
10−21
10−20
10−19
10−18
10−17
Frequency [Hz]
Str
ain
[1
/√H
z]
Adv LIGOEinstein TelescopeDECIGOLISABasic AGISBBO
Recent Workshop
J. Harms, D. Shaddock, R. Adhikari, M. Ando, L. Barsotti, Y. Chen, H. Müller (Nov 5-9)
Explore geosynchronous, heliocentric, squeezing, cavities, HP lasers, corner cubes, etc.
Aim for the 0.01 - 10 Hz band (between LISA and LIGO)
10−4
10−3
10−2
10−1
100
101
10−25
10−24
10−23
10−22
10−21
10−20
10−19
10−18
10−17
Frequency [Hz]
Str
ain [
1/√
Hz]
Adv LIGOEinstein Telescope (D)DECIGOLISABasic AGISBBOUNOGO
⌦GW=2⇥
10 �15
Compare Space Detectors
DECIGO / BBOL = 1000 km
dmirror = 1 m
mmirror = 100 kg
Laser: 10 W, 532 nm
Finesse = 10
Noise: 5 x 10-19 (m/s2)/rHz
DECIGO Pathfinder not selected in JAXA down-select
Try something else…
Simple Michelson: Plaser = 5 W, wavelength = 532 nm
L = 100 km, m = 10 kg, dmirror = 0.35 m
no transponders(?) in remote satellites
Technical laser noise cancellation
Squeezed Light: 2x reduction of quantum noise
Orbits
NGO/eLISA orbit (NGO “Yellow Book”, http://lisa.nasa.gov/documentation.html)
• Hughes, S. P., & Bauer, F. H. (2002). Preliminary optimal orbit design for the laser interferometer space antenna (LISA)
• NGO “Yellow Book”, http://lisa.nasa.gov/documentation.html• Y. Xia, G. Y. Li, G. Heinzel, A. Rüdiger, and Y. J. Luo, “Orbit design for the Laser Interferometer Space Antenna”, Science China Physics (2010)
• Helio ETO very stable. ~kW of solar energy.• For short baseline and high acc noise reqs, can place orbit closer to Earth• Does the relative velocity of SCs require remote transponders?• How much $ savings by closer orbit? Lower initial velocities?
LISA Noise BudgetingAcceleration Noise: 10�16(m/s2)/
pHz
“Current error estimates for LISA spurious accelerations”Stebbins, Bender, Hanson, Hoyle, Schumaker, & Vitale, CQG, (2004)
Frequency [Hz]10-3 10-2 10-1 100 101 102 103
Str
ain
[1
/H
z]
10-24
10-23
10-22
10-21
10-20
10-19
10-18UNGO Noise Budget
Total noiseMagneticCosmic raysResidual gasLaser RPRadiometerThermal RPNewtonianThrusterLocal Sensor Backaction
LIGO
ConclusionsNeed more serious noise analysis (SC thermal, Doppler effects with realistic orbits, beam jitter,…)
Science case: how to exploit 6 decades of frequency space
Possible to get launch, rocket costs from JAXA/ISRO?
What is the real cost savings on payload?
Quantum!Mechanical Limits
Heisenberg!Uncertainty!Principle!
Electric!Field!of Empty Space
Carl%Caves,%PhD%‘79%
Yanbei%Chen%PhD%‘03%
Kip%Thorne%BS%’62%
Vladimir%Braginsky%