Shape-univ December 2002

shape-univ@cosmo.torun.pl

5 participants
4 discussions

Re: military masking net
by szajtan odwieczny 16 Dec '02

16 Dec '02

> As Michaウ said, it's true that the deviations from homogeneity are > small on scales anything much bigger than the Schwarzschild horizon of > a SMBH http://adjani.astro.uni.torun.pl:9673/zwicky/SuperMBH > > Another problem is that in the 2D balloon, the positive fluctuations > (the net) are connected in a continuous network, while the negative > fluctuations (lowest density) are unconnected, separated from one > another. Why do you consider that as a problem. That's just what we observe, isn't it. Those great cosmic scale filaments extending for hundredths of Mpcs. > > In the standard (3D) model, at early times the + and - fluctuations > are typically of the same typical sizes (e.g. from the hypothesis of > "gaussian fluctuations"), and the 2D topology of contours of constant > density ("genus analysis") is connected both for + and - fluctns. agreed but in time the curvature evolves, like everything else in this Universe. In time, because of gravity, matter tends to gather in a strings or clumps of higher density, and thus the curvature changes. > > If you consider all matter more dense than some value, > - a low density value gives a "gruyere (ser) topology" > - a critical density values gives a "sponge topology" what is the difference between these two ? is it only about the thickness of strings ? > - a high density gives a "meatball topology" > > This is impossible to do with a balloon, which is 2D, since the > topology of constant density "1-surfaces" is 1D. Let's consider a cross section of a large part of the universe with a plain. Then we take a pencil and draw all the contours of a constant matter density (= constant curvature) on that plane. We make a little step back to see the picture. We will see some distinctive pattern similar to the one observed for clusters of galaxies. This is the analogy to that net on the balloon. But strings of the net are not 1D but 2D (they have width) and in reality 3D, so for the fishing net we should sometimes even fill up some gaps not allowing the balloon the out stand. This I should call now a military masking net. The constraint of 2D balloon is as you mentioned that - fluctuations are separated. That's right but this is only because that on 2d surface a circle splits it into two regions. So in general this is not a good model. In 3D we can easily jump from one loop into another, unless there are walls (also those from that masking net :) but in 3D) - like The Great Wall. na razie bartek. --------------r-e-k-l-a-m-a----------------- Masz dosc placenia prowizji bankowi ? mBank - zaloz konto http://epieniadze.onet.pl/mbank

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fishing net
by szajtan odwieczny 13 Dec '02

13 Dec '02

hello everybody. Got an idea to share. Once upon a time I thought about such a thing. What was observed are the great voids (of size about 100 Mly in diameter or even bigger) separated by some cosmic great scale structures so it altogether looks like a soap foam. Assuming that the voids are empty, than the curvature of out local part of the Universe would look like - example in 2d: as we were pumping the balloon but confined by a fishing net which doesn't allow the surface of the balloon for free expansion, and in the end the balloon is quizzed by the strings of the net but it out stands in the holes of the net between the strings. In 3d this would be little more complicated to imagine but what do you thing about this ? with best holiday greetings Bartek --------------r-e-k-l-a-m-a----------------- Masz dość płacenia prowizji bankowi ? mBank - załóż konto http://epieniadze.onet.pl/mbank

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andrzej: wyklad jest 12:40-14:40 poniedz.
by Boud Roukema 11 Dec '02

11 Dec '02

Cze�� Andzrej, This semester it's a bit late anyway, but you can see the correct time of the wyk�ad monographiczny here: http://www.astro.uni.torun.pl/sympa/shape-univ/ Sorry about the misunderstanding. pozdrawiam boud

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zwicky pages (so far)
by Boud Roukema 02 Dec '02

02 Dec '02

Cześć wszystkim, (1) How to write in latin-2 on emacs: (1a) With a fairly new emacs (e.g. 20.7 or later): - M-x set-language-environment latin-2 - M-x set-input-method latin-2-prefix (also C-x <ret> C-\) - then can toggle input method with: C-\ Examples: `a`e`l's'c'o`z'z'n ąęłśćóżźń to stop ' being used, use, e.g., a space: ' a -> 'a (1b) You can put the following in your ~/.emacs file (custom-set-variables ;; custom-set-variables was added by Custom -- don't edit or cut/paste it! ;; Your init file should contain only one such instance. '(case-fold-search t) '(current-language-environment "latin-2") '(default-input-method "latin-2-prefix")) (2) The zwicky pages at the moment have a verrrrrrrrrry long URL: http://adjani.astro.uni.torun.pl:9673/zwicky/ Please see Tomek (czosnek) or me to create an account. pozd boud

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Shape-univ December 2002