Cosmo-torun October 2003

cosmo-torun@cosmo.torun.pl

10 participants
10 discussions

Re: prosba o komentarz
by szajtan odwieczny 29 Oct '03

29 Oct '03

> > On Tue, 28 Oct 2003, szajtan odwieczny wrote: > > > What I think we can say for sure is that, although we're not sure about > > the actual curvature of our obserwable universe, and thus we're not sure > > if the space go on and on to infinity, it seems that it's quite sure that > > our universe is accelerating (q<0), and from this point of view we can say > > that if we send out a probe into the space even at the velocity of light, > > it's likely that it will never return regardelss of the the curvature > > of the universe, because it just won't overpass the expantion rate of the > > universe unless there is some nontrivial topology involved. The Big Crunch > > never happens in area where q<0 on Omega_l, Omega_m plane. So from our > > point of view we can say the spacetime is infinite if we're thinking in a > > We can't say "the spacetime is infinite". What you mean is why not ? event horizon accounts for all evolution of expantion according to assumed model. if it's less than the curent curvature radius then we won't see the probe, if it's bigger we mae but not must see it, for the curvature radius is changing in time. > "the http://www.wikipedia.org/wiki/Event_horizon is less than > 2 \pi times the radius of curvature even if comoving space is a hypersphere". last time I checked the page expired so don't know what was there, but did anyone said something about the relation of the event horizon to the curvature ratius.? (this should be calculated) > > This is true even when \Omega_\Lambda = 0 - the Big Crunch happens > before we can see the back of our head. > even better - another reason for which we will never see the sent signal (probe), but with CDM=.3 and DE=.7 or anything close to it we have no big crunch at all. > > way of traveling in it. If we think just of a space as a slice in some > > moment of time the quiestion is still open, but what is use of thinking > > i think you mean here "in some spatial section at constant cosmological time". yes > > about space this way - it just cannot be separated from time right ? > > It's the fundamental nature of the model, so we ought to think about it. the fundamental nature of the model is that going in space we also move in time. eg. Imagine that that space is closed, and expands slow enough that a photon emited from your flashlight can round it, but as the time passes expansion rate mae grow up, event horizon falls, (say cosmological constant starts dominate) and the photon won't make it eventually. > > If you can think of an alternative model which only models our past > time cone, fine. btw. if the accurate model predict things in the past, I see no reason why it should not predict also things in the future. below this this point I don't follow ;) > But personally this reminds me of the Christian > fundamentalist cosmology model where the Unvierse is only 6000 years > old, as written in the Bible. > > It's a model which perfectly fits all cosmological observations, > including those of WMAP. ;) The Universe in this model is the inside gash, does it says about CMB fluctuations ? meaybe I should review the bible instead of Peebles, etc :) > of a sphere of radius 6000 light-years, on which EM radiation of all > sorts of wavelengths (and we could add other particles) was generated > 6000 years ago on this surface, emitted in the direction of the Sun > (and it continues to be generated) in such a way to reproduce a > "naive" model that makes it (more or less) easy for human beings to > interpret these in terms of simple laws of physics. The being "God/Bóg" > which generates the emission wants human beings to have an easily > interpretable Universe, he/she/it is extremely intelligent and able > to generate such complex emission patterns of radiation. Just like > he/she/it set up species of animals 6000 years ago in a way that > makes biologists think there must have been lots of evolution... > > Personally i find the model ridiculous, but it perfectly fits all the > observations and avoids "extrapolation" into times with which we have > no written contact (prehistorical), and the Universe is only 6000 > years old. pozdrawiam bartek.

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Re: prosba o komentarz
by szajtan odwieczny 28 Oct '03

28 Oct '03

What I think we can say for sure is that, although we're not sure about the actual curvature of our obserwable universe, and thus we're not sure if the space go on and on to infinity, it seems that it's quite sure that our universe is accelerating (q<0), and from this point of view we can say that if we send out a probe into the space even at the velocity of light, it's likely that it will never return regardelss of the the curvature of the universe, because it just won't overpass the expantion rate of the universe unless there is some nontrivial topology involved. The Big Crunch never happens in area where q<0 on Omega_l, Omega_m plane. So from our point of view we can say the spacetime is infinite if we're thinking in a way of traveling in it. If we think just of a space as a slice in some moment of time the quiestion is still open, but what is use of thinking about space this way - it just cannot be separated from time right ? bart.

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multipole vectors - another hint for topology?
by Boud Roukema 21 Oct '03

21 Oct '03

http://de.arxiv.org/abs/astro-ph/0310511 ...We find that the result from comparing the oriented area of planes defined by these vectors between multipole pairs 2 <= l1 != l2 <= 8 is inconsistent with the isotropic Gaussian hypothesis at the 98.8% level for the ILC map and at 99.6% level for the cleaned map of Tegmark et al. A particular correlation is suggested between the l=3 and l=8 multipoles, as well as several other pairs. This effect is entirely different from the now familiar planarity and alignment of the quadrupole and octupole: while the aforementioned is fairly unlikely, the multipole vectors indicate correlations not expected in Gaussian random skies that make them unusually likely. ... If it's not topology, it's something else weird (politically incorrect ;) that happened on near-horizon scales... pozd boud

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by joseph mobutu 20 Oct '03

20 Oct '03

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Re: ksztalt Wszechswiata i media kontrolowane
by Andrzej Kus 16 Oct '03

16 Oct '03

Boud, Please ask someone from the group to correct polish in the > http://adjani.astro.uni.torun.pl/cgi-bin/twiki/view/Cosmo/OswiadczeniePraso… Some parts, as it is for the press, are not clear, perhaps Andrzej Marecki can do the job. This is very interesting and important development ! Cheers Andrzej K.

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prosba o komentarz (fwd)
by Boud Roukema 16 Oct '03

16 Oct '03

hi everyone, i definitely think we should respond to this - but i would prefer it to be a collective response - there's no reason why only my name should be cited - e.g., we could at least have the official "team" who was on the grant (amr + motyl + magda + bartek + sebastian + me), but if someone else wants to participate (i guess we can call this an official "press release" (oświadczenie prasowe)) that would be good, especially someone from CAMK to show that we work together despite the bureaucratic difference between CA-UMK and CAMK. As i understand it, Łukasz is in a hurry - he'll ring back at 15.00 - so i'll try to get a draft to the list within the next half hour or so. pozd boud > ---------- Forwarded message ---------- > Date: Tue, 14 Oct 2003 12:07:10 +0200 > From: Lukasz Kaniewski <l.kaniewski at rzeczpospolita.pl> > To: boud at astro.uni.torun.pl > Subject: prosba o komentarz > > Szanowny Panie doktorze! W zeszlym tygodniu w "Nature" ukazaly sie > wyniki badan dotyczacych ksztaltu i rozmiaru Wszechswiata. > > http://www.eurekalert.org/pub_releases/2003-10/ns-dtu100803.php > > Czy moglby Pan wyslac mi swaja opinie na temat tych wynikow? Prosze o > kilka lub kilkanascie zdan - mailem, bylbym wdzieczny za szybka > odpowiedz. > Sprobuje zadzwonic jeszcze do Pan okolo trzeciej. > Dziekuje - Lukasz Kaniewski, dziennik "Rzeczpospolita". >

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Re: prosba o komentarz
by Boud Roukema 16 Oct '03

16 Oct '03

Dear Łukasz, We have a draft version of a text here: http://adjani.astro.uni.torun.pl/cgi-bin/twiki/view/Cosmo/OswiadczeniePraso… but clearly the po polsku is not yet correct. It would probably be better that one of us corrects the po polsku in order to avoid introducing scientific errors, but it is unlikely that this will be ready by 18.00 today. If you can wait till later in the evening, then maybe we will have a better version ready for you. Alternatively, you could just click on "Register" on that page and make yourself your own username + password, then return to the page and click on Edit. Make the language corrections, click Preview and Save when you're happy. I (and maybe some of the others) will check later this evening to see if the scientific meaning is still correct after the corrections, but I'll be offline for the next few hours. Feel free to reply directly to our mailing list (cosmo-torun at astro.uni.torun.pl). *** Please keep the URLs (http links), at least you may shift them as references to the end of the article if you don't like them in the middle of the sentence - the aim of an article about cosmology in a major newspaper should not only be to "inform" readers, but also to give the power to readers to *inform themselves*. By including URLs - even in the paper version - some fraction (10-20%) of the readers will be able to explore further and will have some independence both from Rzeczpospolita editors/writers and from CA-UMK/CAMK scientists. Maybe only 1% will really do this, but the principle of giving maximum power to the reader is a fundamental part of intellectual freedom. pozdrawiam boud On Tue, 14 Oct 2003, Lukasz Kaniewski wrote: > Szanowny Panie doktorze! W zeszlym tygodniu w "Nature" ukazaly sie > wyniki badan dotyczacych ksztaltu i rozmiaru Wszechswiata. > > http://www.eurekalert.org/pub_releases/2003-10/ns-dtu100803.php > > Czy moglby Pan wyslac mi swaja opinie na temat tych wynikow? Prosze o > kilka lub kilkanascie zdan - mailem, bylbym wdzieczny za szybka > odpowiedz. > Sprobuje zadzwonic jeszcze do Pan okolo trzeciej. > Dziekuje - Lukasz Kaniewski, dziennik "Rzeczpospolita".

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Dodecahedral space topology
by Andrzej Marecki 10 Oct '03

10 Oct '03

----- Forwarded message from NatureAlert ----- [...] Dodecahedral space topology as an explanation for weak wide-angle temperature correlations in the cosmic microwave background JEAN-PIERRE LUMINET, JEFFREY R. WEEKS, ALAIN RIAZUELO, ROLAND LEHOUCQ & JEAN-PHILIPPE UZAN http://info.nature.com/cgi-bin24/DM/y/eMJG0BfWLH0Ch0EeW0Ay [...] ----- End of forwarded message from NatureAlert ----- Nature's politics require embargo for articles before they are in the current issue on Nature so the authors couldn't post it on astro-ph but hope they'll do so. ;-) A.M.

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No topological signal detected in WMAP data
by Andrzej Marecki 10 Oct '03

10 Oct '03

Paper: astro-ph/0310233 From: Neil J. Cornish <cornish(a)physics.montana.edu> Date: Wed, 8 Oct 2003 20:27:22 GMT (16kb) Title: Constraining the Topology of the Universe Authors: Neil J. Cornish, David N. Spergel, Glenn D. Starkman and Eiichiro Komatsu Comments: Submitted to PRL \\ The first year data from the Wilkinson Microwave Anisotropy Probe are used to place stringent constraints on the topology of the Universe. We search for pairs of circles on the sky with similar temperature patterns along each circle. We restrict the search to back-to-back circle pairs, and to nearly back-to-back circle pairs, as this covers the majority of the topologies that one might hope to detect in a nearly flat universe. We do not find any matched circles with radius greater than 25 degrees. For a wide class of models, the non-detection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc. ------------------------------------------------------------------------------

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double double-lobed FR IIs
by Boud Roukema 03 Oct '03

03 Oct '03

http://arxiv.org/abs/astro-ph/0310045 Double-double radio galaxies: remnants of merger of supermassive binary black holes Sounds like a model from what andrzej presented yesterday.

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Cosmo-torun October 2003