[Cosmo-torun] ODP: [Cosmo-pl] ESO-ESA working group on fundamental cosmology: report

Marek Biesiada m.biesiada w IMP.sosnowiec.pl
Wto, 3 Paź 2006, 23:12:23 CEST

Dear Boud,
I've had troubles with the server so  I was not able to e-mail earlier. Also I've tried to phone you on a stationary 
phone number you gave me this summer -- without success. My wife's guess was that perhaps new family duties 
keep you out of reach ... 
By the way: is it son or daughter ? Congratulations in any case !
I have ready a new manuscript carefully and 
I have the following remarks concerning the latest version of our paper.
1. Numerical examples should go to the discussion chapter after Chptr. 4.4
Motivation: in the examples we refer to the comoving distance \chi which 
has been introduced only  in Chapter 4.1. 
Placing numerics in the place it is now, could look a bit confusing to the reader. 
2. Figure captions for Figs.1-8 are hard to follow. It is not clear for a reader 
which cases they cover. It would be much more transparent to say which figs illustrate 
self-gravity of a large cluster and which illustrstes effect relative to cosmic web.
3. When you say T^2 it is really a T^1 case (2 images = 2^1) 
T^3 is OK (8 images = 2^3) 
4. In 4.5 two subsequent paragraphs (2nd and 3rd) are written somewhat unclear.
When you say "In infinite simply connected Euclid. space there is no meaningful way 
to calculate gravitational interactions if only a single point-like body is present"
you really mean that 
there is no way to calculate a self-interaction for a single massive body 
(Of course stricty speaking you're right - if there is no other bodies ... even test 
massess ... then there is no interaction But original formulation could be confusing
in my opinion)
Think of appropriate reformulating this. 
5. Finally, the section 4.2 "SPeculation regarding the early Universe" I got your point
and personally I think that its a good idea to follow 
However I agree with the referee 
that present formulation is naive. 
If we speak of inflation then there were no 
dominating massive bodies - it was rather a Quantum Field Theoretical regime ... 
I think that alternating the axes is somewhat reminiscent of mixmaster 
model - of course mixmaster is Bianchi IX not FRLW ......
but there is another problem here which we should better understand : 
what is the relation 
between  the scale factors (in the metric - these are dynamic according to GR) 
and topological lengths of the fundamental domain  (thier change should be governed by laws making topology
dynamic ... and we do not know such laws, besides  hints that they could be quantum - gravitational whatever 
it means)
In conclusion I think that this idea should be better elaborated even before it's
barely mentioned. I would propose to delete this section. 

Best Regards,


Od: cosmo-pl-bounces w cosmo.torun.pl w imieniu Boud Roukema
Wysłano: Pn 2006-09-25 16:17
Do: cosmo-torun w cosmo.torun.pl
DW: cosmo-pl w cosmo.torun.pl
Temat: [Cosmo-pl] ESO-ESA working group on fundamental cosmology: report


ESA-ESO WG on Fundamental Cosmology

Working Group Members:

George Efstathiou
John Ellis
Bruno Leibundgut
Simon Lilly
Yannick Mellier
John Peacock (chair)
Peter Schneider (co-chair)

Abstract of final report

In September 2003, the executives of ESO and ESA agreed to establish a
number of working groups to explore possible synergies between these
two major European astronomical institutions on key scientific
issues. The first two working group reports (on Extrasolar Planets and
the Herschel--ALMA Synergies) were released in 2005 and 2006, and this
third report covers the area of Fundamental Cosmology.

The Working Group's mandate was to concentrate on fundamental issues
in cosmology, as exemplified by the following questions:

     * What are the essential questions in fundamental cosmology?

     * Which of these questions can be tackled, perhaps exclusively,
       with astronomical techniques?

     * What are the appropriate methods with which these key questions
       can be answered?

     * Which of these methods appear promising for realization within
       Europe, or with strong European participation, over the next ~15

     * Which of these methods has a broad range of applications and a
       high degree of versatility even outside the field of fundamental

>From the critical point of view of synergy between ESA and ESO, one
major resulting recommendation concerns the provision of new
generations of imaging survey, where the image quality and near-IR
sensitivity that can be attained only in space are naturally matched
by ground-based imaging and spectroscopy to yield massive datasets
with well-understood photometric redshifts (photo-z's). Such
information is essential for a range of new cosmological tests using
gravitational lensing, large-scale structure, clusters of galaxies,
and supernovae. All these methods can in principle deliver high
accuracy, but a multiplicity of approaches is essential in order that
potential systematics can be diagnosed -- or the possible need for new
physics revealed. Great scope in future cosmology also exists for ELT
studies of the intergalactic medium and space-based studies of the CMB
and gravitational waves; here the synergy is less direct, but these
areas will remain of the highest mutual interest to the agencies. All
these recommended facilities will produce vast datasets of general
applicability, which will have a tremendous impact on broad areas of

Full report (2.4Mb pdf):

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