Shape-univ

shape-univ@cosmo.torun.pl

176 discussions

cosmo books
by Boud Roukema 14 Oct '02

14 Oct '02

message with some discussion of cosmo textbooks: http://www.astro.uni.torun.pl/sympa/shape-univ/2002-05/msg00014.html Since then, some more books have been bought for TCfA and have arrived. To start from the beginning, if you can't find this in the library you can probably just buy it - 7 funt (UK) -> roughly 40 zloty Liddle in po polsku! pozdrawiam boud

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wikipedia & twin paradox
by Boud Roukema 07 Oct '02

07 Oct '02

Cze�� wszystkim, I've put a rough draft of the first lecture here: http://www.wikipedia.org/w/wiki.phtml?title=Shape_of_the_universe but I have to catch the bus now.. Staszek: you'll see the answer to the Twin Paradox stuff in the arXiv reference at the bottom of the page. Please write a wikipedia entry (Polish or English) so that non-specialists can follow this too.... pozd boud

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day/date??
by Boud Roukema 03 Oct '02

03 Oct '02

Hi everyone, I've had two responses so far for choice of afternoon (Monday vs Thursday vs Friday): 1 person in favour of Friday and 1/week - > I think, that friday afternoon, will be just fine, and frequency of a > 1/week will be good ,too. I'm the second/third year student:) 1 person strongly against Friday, but Thursday OK. Since lectures are supposed to start this week, we need to make a quick decision. Is there anyone who wants to attend the course and *cannot* attend Thursday 14h-16h? pozd boud

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day and frequency of shape-univ monog course?
by Boud Roukema 25 Sep '02

25 Sep '02

Cze�� wszystkim, Could students (np IV, V or III rok) interested in the "Shape of the Universe" monograph course this semester please send an email with their preferred day and frequency for the course to: cosmo-spotka(a)astro.uni.torun.pl day: At the moment, Monday, Thursday and Friday afternoons seem to be free. (but III r students are *not* free Thurs afternoon - they have "lektoraty") freqency: 1/week or 1/fortnight? A general description of the course is here: http://www.astro.uni.torun.pl/sympa/shape-univ/ but the details, whether it's introductory or more detailed, etc., will depend on who is interested. Remember that there is a page to help communication among students, and between students and faculty, on cosmology-related courses, here: http://www.astro.uni.torun.pl/sympa/cosmo-intro/index.html pozdrawiam boud

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urlop 29/07 - 02/08
by Boud Roukema 27 Jul '02

27 Jul '02

Cze�� wszystkim, B�dzi� w urlopu 29/07 - 02/08, w Hajn�wce przez �ubr�w... Na ra�e Boud

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xi(r) from Hoyle's P(k)
by Gary Mamon 01 Jul '02

01 Jul '02

Dear all, I finally computed the correlation function extpected from Hoyle etal.'s P(k) obtained from their analysis of the 2QZ-10k quasar sample. I used the final part of eq. (21.40) of Peebles (1993) book to convert P(k) to xi(r). I now understand that last equation as resulting from the integral over angles of the previsou integral (which is in fact triple: dk dtheta dphi). I extended the P(k) beyond the values of Hoyle et al in two ways: 1) I used the theoretical BBKS (Bardeen et al. 84, appendix) P(k) (black & white plot). Notice that Hoyle's points are about a factor of 10000 too high so the P(k) is highly discontinuous. 2) I moved up the BBKS P(k) on each side of the Hoyle range so as to make the whole P(k) continuous. 3) Same as 2) with a step in log k decreased from 0.075 (Hoyle et al.'s step) to 0.01. (see 4th attached file). The three xi(r) plots are attached. The calculation were done with Omega = 0.3, h = 0.7, Omegab = 0.04. Even though Hoyle's peak is at 2 pi h / 89 Mpc, the 1st plot shows xi(r) with peaks at 67, 127 and 255 h-1 Mpc, close to what we (Boud really) gave in RMB02. This gives us some confidence that Boud's calculations are not completely wrong :-) and that there is no simple relation such as peak in xi at 2 pi / k_peak, where k_peak is the peak in P(k). However, in the 2nd plot, the peaks are very narrow and marginally significant at 90.6, 107.6, 109.3, 127.8, 180.6 and 255.0 h-1 Mpc. Finally, in the 3rd plot, it is hard to distinguish anything! However, with some imagination, one can guess excess broad power around 140 h-1 Mpc and a finer excess around 255 h-1 Mpc... Let me know what you think. all the best Gary

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smoothed xi(r)
by Gary Mamon 30 Jun '02

30 Jun '02

Hi again, Attached you will find the same xi(r) as case 3 of the previous e-mail with, in red, it's smoothing by a 15 h-1 Mpc gaussian. I must admit that I worked avery quickly and there may be errors... cheers Gary

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xi(r) from P(k)
by Gary Mamon 13 Jun '02

13 Jun '02

Hi everyone, For my talk at the IAP colloquium on July 2, it would be nice if I could show the xi(r) expected from the 2dFGRS and 2QZ P(k)'s (that are quite similar). I want to see how strong and where will the wiggles be in the xi(r) derived from the P(k). Does anyone have time to do this? By the way, I don't understand the formulation given in Peebles's book (1993, PoPC), eq. 21-40 (p. 509). If P(k) = <|delta(k)|^2>, then shouldn't the right-hand-side of the 2nd line in eq. 21-40 be sin(kr) instead of sin(kr/(kr)? cheers Gary P.S. I agree with Boud that doing ML estimation or chi2 estimation on xi(r)s is dangerous because the separation bins are not truly independent.

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seminar at Mt Stromlo
by Gary Mamon 04 Jun '02

04 Jun '02

Dear all, My talk at Mt Stromlo went very well. Brian Schmidt of supernovae fame made a good remark. Instead of looking for peaks, which could simply require that the xi(r)'s in different z bins are similar (he thought of using a maximum likelihood technique). He was referring to Alcock & Paczynski... Matthew Colless mentioned that both 2dF galaxies (2dFGRS) and quasars (2QZ) show a feature in P(k) at 2pi/89 h Mpc-1. Matthew's postdoc, Roberto de Propris, showed me a plot of the correlation function of the superposition of many pencil beams drawn through the 2dFGRS. He has access to the full 250k sample, and avoided computing a complete xi(r) using all 30 billion separations. There is a feature around 250 Mpc, but there are also stronger features elsewhere, but not at 130 h-1 Mpc. It thus appears that Broadhurst et al. were lucky back in 1990. cheers Gary

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comments from Brian Boyle
by Gary Mamon 03 Jun '02

03 Jun '02

Dear all, Brian Boyle (PI of 2dF quasar survey) came to my talk at Macquarie University. He seemed to like our analysis. His main comment was: "Have you tried repeating your correlation function analysis by replacing the scambled redshifts with a smoothed redshift distribution?" This is what I gathered you (Boud) have done these last few days (extrapolating from Boud's often cryptic messages). I answered that we are in the process of doing just that, and our *** preliminary *** result is that the 125 h-1 Mpc feature comes out strongly in the 1st z-bin, but that we did not have yet any conclusion on Omega,Lambda. cheers Gary

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Shape-univ