Notes from the Einstein Telescope meeting by John Veitch

NIKHEF, Amsterdam 25/9/2008

Noise Curve:

Noise curve presented was not an extrapolation of current technology 
but a desired goal.  An analytical fit to the curve is available. 
(Chris van den Broeck) Inspiral horizon could be as great as z=5 for 
100-100 Msol, z=2 for BNS.

Andreas Friese will come up with tentative noise curve model, next few 
weeks.

Not so important at the moment, what we should do is look at second 
generation detectors and ask what gains we would like for the third 
generation?  Also, what locations of detectors and orientation?
Chris will upload analytical fit to WP4 work area.  
[ https://workarea.et-gw.eu/et/WG4-Astrophysics ]

It will be difficult to predict whether the low or high frequency 
parts of the curve will be realistic in the future, we want to know 
the scientific impact of changes in parts of the curve, or tradeoffs 
between low and high frequency optimisation for example.  We have a 
reference curve to begin with.

Also need to examine the effect of changing the low frequency cutoff 
( 1 Hz - 5 Hz? ) Changing the low frequency cutoff has a large effect 
on the long term observation of inspirals, through the rotation/orbit 
of the Earth. Above 5 Hz that is not available.

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Review of Science Goals:

Sathya's presentation from LSC has a list of deliverable science goals, 
and also more speculative science goals.  Comments on the contents of the list:

Fundamental Physics
Looking to future we might want the support of HE theorists as well 
as astronomers.  Weakest of entries is test for massive gravitons. 
Not well motivated but would be possible to check.  Black hole 
spectroscopy / no hair theorem can be included with other tests of GR.

Cosmology
This area overlaps with LISA. Do we want to include these things as 
primary goals?  Additional point: Mapping stellar mass black hole masses 
over cosmological history, unique for ET?

Being able to see to great distance allows us to establish gravitational 
markers to examine large scale structure 
Costas: Why not include stochastic BG? Sathya: We will not reach inflation, 
so should not be a primary goal.  EM observations will reach these levels of 
observations earlier than the ET.

Benoit: We should study what LISA can do and ET cannot and vice versa, not 
necessarily to publicise but simply to understand.  Should look at the 
level of confusion noise.  Should also not dismiss possibilities from 
HEP (extra dimensions etc etc) but if they are to make it into the
study document need to be based on solid figures.

Astrophysics
GRBs may already be understood by the time of the ET. 
Observations of NSs down to e=10^-11 should allow studies of the 
equation of state. if we see nothing at that level we kill a lot 
of theories. This would be a good science driver. Unique to the ET.

Supernovae would at best be visible to 10s of Mpc, but this is not 
completely known. The early collapse may not be visible but the 
formation of the neutron star would likely produce excitations of modes.
What causes magnetar flares may be a target for multi messenger 
astronomy, but it may also be resolved before ET so could be a 
secondary goal.

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Data Analysis goals:

Computational resources. We should maintain an estimate of what will 
be possible computationally in the timeframe of ET.
Leone: We should contact the groups who predict the state of computing.
Specialised hardware does not generally pay off.
We should design analysis to be highly parallel as processors will 
increasingly move in this direction. GFX cards also present massively 
parallel design.

We also need to coordinate groups who can disentangle source 
confusion / simultaneous source identification and global analysis to 
see the effect of the galactic neutron star background. Will it wash 
out the inspiral signals, we need to know this for the science case.

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Sub groups:

As described in the document, there is 5 sub projects. Would be good 
to have one person to help flesh out each section alongside Sathya. 
Document will be updated with each person.

Multi messenger astronomy will be a selling point which will be handled 
by people within each science topic, but there will be an overall 
coordinator.


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Organisation of meetings:

Initially, one telecon per month while we are preparing the science 
goals report and working with the noise curve.  We need to report our 
status once per six months.

Goal for meeting on 24th November is to have a more expanded and 
polished document on the science potential. This will include at 
least back of the envelope calculations on what will be possible 
with the noise curve.

We will try to meet face to face once per six months in Europe.