dipartimento the detection of gravitational waves universe ... · the ligo observatories ! adapted...
TRANSCRIPT
![Page 1: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/1.jpg)
U
niverse observation through
gravitational waves
the detection of gravitational w
aves.
Fulvio Ricci
Dipartim
ento di Fisica, Università di Rom
a Sapienza
&
INFN
Sezione di Roma
![Page 2: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/2.jpg)
Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7.
The start of the GW
astronomy
![Page 3: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/3.jpg)
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7.
The start of the GW
astronomy
![Page 4: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/4.jpg)
!
Linearized Einstein eqs. (far from big m
asses) admit w
ave solutions (perturbations to the background geom
etry)
!
GW
: transverse space-time distortions
propagating at the speed of light,
2 independent polarization
!
Dynam
ical part of gravity, filling the space
Ripples in the C
osmic S
ea
01
1 w
ith 2 2
22
=! !" #
$ $% &
∂ ∂−
∇⇒
<<+
=µν
µνη
ht
ch
hg
! ! ! ! !" #
$ $ $ $ $% &
−=
+×
×+
−
00
00
00
00
00
00
),
()
(
hh
hh
etz
kzt
iω
h
TG
4
8c Gπ=
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Coupling constants
!
In SN collapse ν w
ithstand 103 interactions before leaving the star,
GW
leave the core undisturbed
!
Decoupling after Big Bang
– GW
∼ 10-43 s (T ∼ 10
19 GeV)
– ν ∼ 1 s (T ∼ 1 MeV)
– e.m. ∼ 10
12 s (T ∼ 0.2 eV)
strong e.m
. weak
gravity
0.1 1/137
10-5
10-39
Ideal information carrier,
Universe transparent to G
W all the w
ay back to the Big B
ang!!
GGWW
eemmiissssiioonn:: vveerryy eenneerrggeettiicc eevveennttss bbuutt aallmm
oosstt nnoo iinntteerraaccttiioonn
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!
Luminosity:
!
Amplitude:
Target G
W am
plitude
42
1
Gh
Qc
rµν
µν=
⋅!!
62
5
55
!" #$% &
!" #$% &
⋅>≈
<=
c vR R
G cQ
Qc G
PS
ijij
ε!!!
!!!Com
pactness C 1 for BH
0.3 for N
S 10
-4 for WD
1059 erg/s
h ~ 10
-21
Target am
plitu
de:
coalescing NS/N
S in the Virgo cluster (r ~10 M
pc)
Efficient sources of GW
must be
compact
and fast
GW
detectors are sensitive to aplitude h : 1/r attenuation!
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Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7.
The start of the GW
astronomy
![Page 8: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/8.jpg)
The
The G
ravitational Wave S
pectrum
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CB
C
!
Compact stars (N
S/NS, N
S/BH, BH
/BH)
!
Inspiral signal accurately predictable
– New
tonian dynamics
– Post-New
tonian corrections (3PN, (v/
c) 11/2) [L.Blanchet et al., 1996] !
Recent big progress in merger 3D
sim
ulation [Baker et al 2006, Praetorious 2006]
chirp
[Cam
panelli et al., PR
L, 2006]
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Supernovae
!
Collapse dynamics and w
aveform badly predictable
!
Estimated rate: several /yr in the VIRG
O cluster, but the efficiency of G
W
emission is strongly m
odel dependent
!
Simulations suggest E
GW ~
10-6 M
ʘ c2, but N
S kick velocities suggest possible strong asym
metries
GW
emitted
secs
hrs
[Zw
erger, Muller]
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More on neutron stars
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Relic S
tochastic Background
!
Imprinting of the early expansion of the universe
!
Correlation of two interferom
eters needed for detection
Relic neutrinos
CM
BR
R
elic gravitons
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Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7.
The start of the GW
astronomy
![Page 14: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/14.jpg)
Detection
Need to m
easure: ΔL ~
10-18 m
Target h ~
10-21
(NS
/NS
@V
irgo Cluster)
Great challenge for experim
entalists!
Feasible L ~
103 m
12L
hLΔ
≈
GW
induce space-time
deformation
Measure space-tim
e
Strain using light
Interference fringes
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Pout depends also on P
in , λ, L.
ITF sensitive to power and frequency fluctuations, displacem
ent noises, …
4gw
Lh
πφ
λ=
⋅
20
cos(
)out
ingw
PP
φφ
=+
A sim
ple detector
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Increasing the optical path
Effe
ctive le
ngth
:
!
Fabry-Pe
rot cav
ities: am
plify the length-to-phase transduction
!
High
er fin
esse ="
higher df/dL !
Draw
back: works only at
resonance
2'
FL
Lπ
=⋅
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!
Power fluctuations lim
it the phase sensitivity. Ultim
ate power
fluctuations associated to the quantum nature of light
!
Shot noise (assuming P,λ stable):
!
L = 100 km, P = 1 kW
!
Lengthen the detector to 100 km.
Increase the light power m
ore than 1 kW.
HO
W?
Optical R
eadout Noise
23
21
310
/H
z
10shot
shot
hh
−
−
≈⋅
≈
!
21
shotshot
ch
PL
Pω
λφ
π=
⇒=
⋅!
!"
"
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kWatts pow
er injected!
Interferometer Ecology: recycle the w
asted light!
!
Peff = Recycling factor ·P
in " 50 x 20 W
= 1 kW
!
Shot noise reduced by a factor ~ 7
!
One m
ore cavity to be controlled !
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A real detector schem
e
Laser 20 W
Output M
ode Cleaner
3 km long Fabry-Perot cavities:
to lengthen the optical path to 100 km
Input Mode C
leaner
Power recycling m
irror: to increase the light pow
er to 1 kW
Virgo optical schem
e
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Free falling test m
asses
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ITF
Operation C
onditions
!
Keep the FP cavities in resonance – M
aximize the phase response
!
Keep the PR cavity in resonance – M
inimize the shot noise
!
Keep the output on the dark fringe
– R
educe the dependence on power
fluctuations
Keep the armlength constant w
ithin 10
-12 m !
ACTIVE CO
NTRO
LS NEED
ED!
L OCKING
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Interferometer control
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Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo
5. LIGO
-Virgo joint observation 6. The discovery 7.
The start of the GW
astronomy
![Page 24: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/24.jpg)
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25
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! Participated by scientists from
Italy and France (form
er founders of Virgo), The N
etherlands, Poland, Hungary and Spain
THE
VIR
GO
C
OLLA
BO
RATIO
N:
6 European countries
20 labs A
PC
Paris
AR
TEM
IS N
ice E
GO
Cascina
INFN
Firenze-Urbino
INFN
Genova
INFN
Napoli
INFN
Perugia
INFN
Pisa
INFN
Rom
a La Sapienza
INFN
Rom
a Tor Vergata IN
FN Trento-P
adova LA
L Orsay – E
SP
CI P
aris LA
PP A
nnecy LK
B P
aris LM
A Lyon N
IKH
EF A
msterdam
P
OLG
RAW
(Poland)
RA
DB
OU
D U
ni. Nijm
egen R
MK
I Budapest
VALE
NC
IA University
.
Total num
ber 350 mem
bers 68%
Physicists and E
ngineers 16%
Consultants
16% P
hD S
tudents
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Ad V
irgo in a nutshell
heavier'mirrors'
(42'kg)'
high'finesse''(≈1000)'larger'beam
'waist'
DC'detec>on'
signal'recycling'
new'IP'
>lt'control'
new'payload'
fused'silica'suspensions'
high'power'SSL'
(200'W)'
Larger central vacuum links
Large cryotraps
28
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29
The adV m
irrors
Substrate: SiO2
Mirror: 42 kg, 35 cm
diameter, 20 cm
thick
Beam
Splitter: 50 cm
diameter, 10 cm
thick
Hom
ogenity < 5 x 10-7
Surface uniform
ity< 1 10 -9 m EG
O C
ou
ncil, D
ec 11, 2015
G L
osu
rdo
- Ad
V P
roject L
eader
17
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30 T
he payload
The central area
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31
Seismic noise attenuation
The vacuum to reduce
the diffusion of the light
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Electronic control of the
super attenuator
Superattenuator
Sensors Coil
Drivers
Motors
Sensors
Sensors
Coil
Drivers
Coil
Drivers
Position &
D
ampin
g
Acc. Sens: - 10
-9 m/s 2
- 0 – 100Hz
- f.s. 1g D
rivers
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Plan of the T
alk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-V
irgo joint observation 6. The discovery 7.
The start of the GW
astronomy
![Page 34: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/34.jpg)
The “single m
achine”
MO
U to be signed betw
een LIGO
Scientific Collaboration and Virgo: – Full exchange of data, joint analysis – Coordinate science runs, com
missioning and shutdow
ns – Joint publications
4 detectors to operate as a SSIINN
GGLLEE
MMAA
CCHH
IINNEE
G
reat scientific value added
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Triangulation allows to
pin
poin
t the so
urce
The network allow
s to deconvolve detector response and signal w
aveform #
measu
re
signal p
aramete
rs
The benefits of a netw
ork
False alarm
reje
ction
requires coincidence
Longer obse
rvation tim
e, better sk
y cove
rage
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The LIG
O O
bservatories
! Adapted from
“The Blue Marble: Land Surface, O
cean Color and Sea Ice” at visibleearth.nasa.gov ! N
ASA Goddard Space Flight Center Im
age by Reto Stöckli (land surface, shallow w
ater, clouds). Enhancements by Robert Sim
mon (ocean color, com
positing, 3D globes, anim
ation). Data
and technical support: MO
DIS Land G
roup; MO
DIS Science D
ata Support Team; M
OD
IS Atmosphere G
roup; MO
DIS O
cean Group Additional data: U
SGS ERO
S Data Center (topography); U
SGS
Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); D
efense Meteorological Satellite Program
(city lights).
LIGO
Hanford O
bservatory (LHO
) H
1 : 4 km arm
s H
2 : 2 km arm
s
LIGO
Livingston Observatory (LLO
) L1 : 4 km
arms
Credit: P.Shaw
an
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Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7.
The start of the GW
astronomy
![Page 38: Dipartimento the detection of gravitational waves Universe ... · The LIGO Observatories ! Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov](https://reader034.vdocuments.net/reader034/viewer/2022042222/5ec9195b77aaaf6b67455164/html5/thumbnails/38.jpg)
H1- H
anford – Washington state
L1- Livingston – Louisiana state
LIGO
upgrade
concluded
The A
dvanced LIGO
dedication cerem
ony w
as held at Hanford on
May 19, 2015
VIR
GO
will end
the upgrade in 2016
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strain amplitude evolution in tim
e and frequency
Residual noise after w
aveform
subtraction
35 – 350 Hz bandpassed strain tim
e series
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C
ombined S
NR
= 23.6 , F
AR
= 1/203,000 years "
5.1 σ
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Param
eter Estim
ation
One of the m
ost energetic astronomical event ever
observed: P
ower em
itted ~~ 220000 MM
//ss E
nergy emitted ~
11004499 JJ ""
33 MM cc
22
50 times brighter of the entire visible universe
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How
the signal might look like
This source:
Binary system
Produces this waveform
:
Embedded in this noise
stream:
matched filtering or excess
power
h
Tim
e to coalescence (sec)
Signal (t)SNR
(t)
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Assum
ing that the signal is C
BC
like: m
atched filter search
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Com
pact Binary C
oalescence: W
aveforms
m1 =
m2 =
10 M
s1,z =
s2,z =
0.99 s1,z =
0.99, s2,z =
-0.99 s
1,z = s
2,z = -0.99
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GW
150914 "
Signal/Noise =24
GW
151226 "
Signal/Noise = 13
+
LVT
151012 "Signal/N
oise =9.7
While w
e are not so confident to tag this as a detection, it is m
ore likely to be a gravitational w
ave signal than not
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GW151226'
GW150914''''''''
LVT'151012'
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Final m
ass 62 times that of the sun
Final m
ass 35 times that of the sun
Final m
ass 21 times that of the sun
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Plan of the talk
1. GW
research motivations
2. Sources 3. Principles of interferom
etric detection 4. W
hat is Virgo 5. LIG
O-Virgo joint observation
6. The discovery 7. The start of the G
W astronom
y
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Sky Locations of G
ravitational-wave E
vents G
W150914, G
W151226 and C
andidate LVT
151012
Sky localizations
90% credible areas of about
620 deg
2 GW
150914
1600 deg2 LV
T15012
1000 deg
2 GW
151226
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Sim
ulated Sky Locations of O
1 Events and
Candidate Including the V
irgo Interferometer
Sky localizations
90% credible areas of about
10-20 deg
2 GW
150914
1000 deg2 LV
T15012
600 deg
2 GW
151226
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LIGO
Livingston
US
A
LIGO
H
anford U
SA
Virgo
Italy
KA
GR
A
Japan
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Source Localization of the N
etwork
Credit: S. Fairhurst
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How
to improve the
sensitivity W
here and how can w
e reduce further the detector noise?
Seismic
Thermal
Shot H
igh power laser
Better optics
New
optical configuration
QN
D techniques
New
materials
Cryogenic interferometers
Underground detectors
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56 Lecce -2013 – F
ulvio R
icci
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Conclusion
GW
will help to go beyond E
instein by testing of com
peting theories of gravity
GW
will probe the status of the m
atter in the extreme condition
Deviation from
the prediction of the classical physics can be the clue of a super unification phenom
enon
GW
, predicted by A. E
instein 100 years ago, have been detected directly for the first tim
e
GW