Fundamental Physics, Astrophysics and Cosmology …martin/gws/sathya.pdf · Fundamental Physics,...

Fundamental Physics,

Astrophysics and

Cosmology with ETB.S. Sathyaprakash (CU) and Bernard Schutz (CU, AEI)

based on a Living Review article with a similar title (in preparation)

Fundamental Physics, Astrophysics and Cosmology with ET

p2

ET Science Summary

Fundamental physics

What are the different polarization states of gravitational

waves?

Are gravitons massless?

Black hole spectroscopy and the no-hair theorem?

Is general relativity the correct description of strong gravity?

Cosmology

Independent and accurate measurement of Hubble constant

What is the nature of dark energy?

How is matter organized on very large scales?

What were the physical conditions in the early Universe?


p3

ET Science Summary

Astrophysics

What is the origin of gamma ray bursts and what are the

different populations?

Are ULX sources IMBH? How and when did they form?

How asymmetric are neutron stars and what is their equation-of-

state?

What is the end state of gravitational collapse?

Fundamental physics


p5

Counting the Polarization States

Cross polarizationPlus polarization

Only two states in GR: h+ and hx


p6

Polarization States in a

Scalar-Tensor TheoryCliff Will


p7

Speed of Gravitational Waves

Coincident observation of an electromagnetic event and the

associated gravitational radiation can be used to constrain the

speed of gravitational waves to a fantastic degree:

If ∆t is the time difference in the arrival times of GW and

optical radiation and D is the distance to the source then the

fractional difference in the speeds is

Should be possible with coincident observation of gamma-ray

bursts up to very high red-shifts


p8

Dispersion of the waves and binary

black hole Spectroscopy

Massive gravitons suffer dispersion which will be imprint in the phasing of the waves

Waveform currently known to 3.5 PN (i.e. to order v7/c7) in phase and 2.5 in amplitude (up to seven harmonics of the orbital frequency)

Should allow better tests of general relativity

Harmonics PN corrections

Blanchet et al (2002, 2004, 2005); Van Den Broeck and Sengupta (2006, 2007)

Black Hole Spectroscopy


p10

Black Hole Quasi-Normal Modes


p11

QNM Frequency and Damping Time

(Echeverria, 1989)


p12

Black Hole Spectroscopy

Berti, Cardoso and Will


p13

Quality Factor of BH QNMs

Berti, Cardoso and Will


p14

Testing the No-Hair Theorem

By measuring a single (say l=2, m=2) quasi-normal mode’s

frequency and damping time one can determine the mass

and spin of the black hole

No-hair theorem: Frequencies and damping times of other

modes also depend on the mass and spin of the BH

If it is possible to measure the other modes then we would

be basically testing the no-hair theorem

Strong-gravity GR Tests


p16

Testing the tail effect

Gravitational wave tails Testing the presence of tails

Blanchet and Schaefer

Blanchet, Sathyaprakash


p17

Strong Field Tests of GR

Arun et al


p18

From inspiral and ring

down signals

measure M and J before

and after merger: test

Hawking area theorem

Is J/M2 less than 1?

Consistent with a BH or

Naked singularity or

Soliton/Boson stars?

Fundamental questions on strong gravity

and the nature of space-time


p19

Testing the merger dynamics


p20

Adv LIGO Sensitivity to Inspirals


p21

Strong field tests of gravity

Jones and BSS

Cosmology


p23

Binaries are Standard Sirens

Frequency f = √ρρρρ

Dynamical frequency in the

system: e.g., in a binary

twice the orb. freq.

Binary chirp rate

Many sources chirp during

observation: chirp rate

depends only on the chirp

mass:

M = (m1m2)3/5 (m1+m2)

-1/5

Chirping sources are

standard sirens

Luminosity L = (Asymm.) v10

Luminosity is a strong function

of velocity: A black hole binary

source brightens up a million

times during merger

Amplitude

h = (Asymm.) (M/R) (M/r)

The amplitude gives strain

caused in space as the wave

propagates h = dL/L

Schutz


p24

Need coincident EM-GW observation for

Cosmology

Amplitude of gravitational waves depends on the

combination of Chirp-mass/Effective-Distance

Effective-Distance depends on the luminosity distance, source

location and polarization

Gravitational wave observations can independently

measure the amplitude and the chirp-mass

Therefore, binary inspirals are standard sirens: from the apparent

luminosity (the strain) we can conclude the luminosity distance

However, chirp-mass and luminosity distance both scale as

(1+z) so GW observations alone cannot determine the red-

shift

Joint GW (for luminosity distance) and optical observations (for

red-shift) can facilitate a new cosmological tool

Schutz


p25

Cosmology with inspirals

If a binary inspiral is associated with an EM event

Knowledge of the direction to the source and the time of the event

can be used to greatly improve the accuracy of the estimation of

luminosity distance

Can measure the Hubble constant to a good accuracy, as also other

cosmological parameters

Exploring the large-scale distribution of matter in the

Universe

A population of inspirals will act as markers with known luminosity

distance and red-shift

Will allow detailed study of dark matter distribution in the

Universe via gravitational lensing.


p26

*

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**

*

*

* *

*

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Image: WMAP

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*


p27

Massive Black Hole Merger Rates

The rates depend on the

specific scenario by which

black hole seeds formed

The rates would be 10’s

per year if small black

holes were the seeds

The rates would be several

100’s per year if the seeds

were in the region of 104

to 106 solar masses

Observed merger rates

will test models of

formation of black hole

seeds

Sesana, Volonteri, Haardt, 2007


p28

Astrophysics


p29

Information carried:

Masses (a few %), spins (few %),

distance (~10%), location on sky

(~10’s of degrees)

Astrophysics From Binary Coalescences

NS/NS NS/BH BH/BH

Search for EM counterpart, e.g. γ-burst. If found:Learn the nature of the trigger for that γ-burst

Deduce relative speed of light and GW’s to ~ 1 sec / 3x109 yrs ~

10-17

Measure Neutron Star radius to 15% and deduce equation of

state

Relativistic effects are very strong, e.g.

Frame dragging by spins ⇒ precession ⇒ modulation


p30

Neutron Star-Black Hole

Inspiral and NS Tidal Disruption

Merger involves general relativistic non-linearities,

relativistic hydrodynamics, large magnetic fields,

tidal disruption, etc., dictated by unknown physics at

nuclear densities

1.4Msun / 10 Msun NS/BH Binaries


p31

What I haven’t talked about

Burst sources and multi-messenger astronomy

Szabi Marka (this afternoon)

Stochastic background of gravitational waves

Marco Bruni (Thursday)

Continuous waves from neutron stars

A lot of microphysics to be learnt but much needs to be

understood in terms of strengths of sources


p32

Slide by: P Shellard

Fundamental Physics, Astrophysics and Cosmology …martin/gws/sathya.pdf · Fundamental Physics,...

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