Cosmo-torun

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328 discussions

OCRA - mass function of haloes
by Boud Roukema 29 Mar '02

29 Mar '02

Hi everyone, Inoue & Nagashima have a paper http://de.arXiv.org/abs/astro-ph/0110503 about the mass function of dark matter haloes, in other words, the frequency of how many objects of different masses (high or low) form at a given epoch during the collapse of matter due to gravity. I think this could be an important paper for modelling what statistical constraints on Omega_m & Omega_Lambda (or eventually w_Q) could be obtained from OCRA. Boud

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European Pdoc? (M Curie-Skl)
by Boud Roukema 21 Mar '02

21 Mar '02

Questionnaire for research institutions in Poland interested to host Marie Curie-Sk�odowska postdoctoral fellowships to be sent to ph3(a)npk.gov.pl Institution: Uniwersytet Mikolaja Kopernika Institute: Toru� Centre for Astronomy Address: ul. Gagarina, 11, PL-87-100, Toru� Homepage: http://www.astro.uni.torun.pl/sympa/ Contact person: Dr Boud Roukema Phone/fax: +48 56 611 3039/+48 56 611 3009 Email: boud(a)astro.uni.torun.pl Research field: observational cosmology Working languages: English, French, Polish Description of research topic/subject: The postdoctoral fellow would be expected to carry out original, independent research in any field of observational cosmology, and to stimulate discussion of observational cosmology among faculty and students. Fields presently being developed or likely to be developed at the Toru� Centre for Astronomy include constraints on local cosmological parameters such as the matter density parameter, the cosmological constant and the effective quintessence parameter, using public archival data; attempts to measure global parameters via topological lensing, using radio-loud AGNs, clusters and the cosmic microwave background; and galaxy formation and evolution. Candidates in other fields of observational cosmology are welcome to apply: excellence and originality of research will be the primary criteria for making a selection. >>>>>>>>>>>>>>>> cut here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< [Comment to cosmo-torun group: This is an administrative request to see if we can get some money for a European postdoc. Andrzej M, Andrzej K and I thought it best to keep the subject open to any theme in observational cosmology. I think we have till Monday before Wydzia� Fizyka meets to discuss the proposals, so please make any comments, criticisms, complaints, suggestions quickly!]

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Wiesci Jodrell Bank
by Marcin Gawronski 11 Mar '02

11 Mar '02

Hello .. Przyjade na Wielkanoc do Polski i bede przez pewien czas w Toruniu. W zwiazku z tym chcialbym Wam opowiedziec o mojej pracy w Jodrell, ktora dotyczy ewolucji kosmologicznej AGN'ow. Chcialbym przedstawic swoje pierwsze wyniki i omowic obecne problemy w tym temacie. Udalo mi sie tez zbudowac model nieba radiowego na czestosci 30 GHz, czyli to co powinnismy widziec za pomoca OCRY. W Toruniu bede obecny przez tydzien tuz przed Swietami.. cheers MPG

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Conference Announcement (fwd)
by Boud Roukema 08 Mar '02

08 Mar '02

An important topic! ---------- Forwarded message ---------- > Date: Thu, 07 Mar 2002 19:01:49 -0500 (EST) > From: Thomas Reiprich <thr4f(a)virginia.edu> > To: "Conference, Cooling Flows": ; > Subject: Conference Announcement Dear colleague, March 5, 2002 this is the First Announcement of the Conference on ******************************************************************** * * * The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies * * * * which will take place at the * * * * Omni Hotel, Charlottesville, VA, USA * * from May 31 through June 4, 2003 * * * ******************************************************************** Note that future announcements will ONLY be sent to people who pre-registered through http://www.astro.virginia.edu/coolflow/preg.php Recent observations have significantly broadened our view on cooling flows in galaxies and clusters of galaxies. The wealth of new information through observations has led to a flourishing development in theoretical modelling. The purpose of this conference is to summarize relevant observational results at all wavelengths, to compare the predictions of models and simulations to these observations, and to assess the impact of processes in cluster cores on the application of galaxy clusters as cosmological probes. All further relevant information has been posted at the conference web page ******************************************* * http://www.astro.virginia.edu/coolflow/ * ******************************************* If you are potentially interested please take a short moment to fill in the pre-registration form to ensure receiving future announcements. We apologize if you received this Announcement more than once. This Announcement was originally sent on March 5 but due to a mailing problem a very large fraction of the recipients did not receive this mail. Sincerely, Thomas Reiprich If you don't have access to the WWW you may contact Thomas Reiprich by phone: +1-434-924-4904, fax: +1-434-924-3104, or snail mail: Department of Astronomy University of Virginia PO Box 3818 530 McCormick Road Charlottesville, VA 22903-0818 USA -- You can find my address at: http://www.reiprich.net/

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cosmo TCfA mailing lists - Witamy!
by Boud Roukema 19 Feb '02

19 Feb '02

Dear Anna, Magdalena, Nazywam si� Boud Roukema. I am about to start a job at TCfA to help organise a cosmology/extragalactic research group. Sebastian just told me that you are TCfA PhD students spending some time in JBO. To help organise discussion about research projects and techniques among us, Andrzej Marecki and I have started to create some email discussion lists, which are archived on the web. If you look at the pages: http://www.astro.uni.torun.pl/sympa/ you'll see that there are several lists which might interest you. Since you are at JBO on a long time scale, probably the cosmo-torun list would be the one most useful for you right now - but, of course, you're free to subscribe to any of the lists. The list cosmo-pl would probably interest you too - for the moment there are no messages - it will evolve depending on how people want it to evolve! (I m�j po polsku nie jeszcze jest wystarczy dobry dla dobrze dyskutowa� w tej listy mejla...) So I've subscribed you both to cosmo-torun and cosmo-pl (using your astro.torun addresses - you can still send mail to the lists from a JBO address, but it requires an authentification key to avoid spam). Of course you may unsubscribe if you think there are too many uninteresting messages... A very useful function is the archive - but since research ideas may be discussed *before* they are published, there is (moderately) limited access to the http://www.astro.uni.torun.pl/sympa/cosmo-torun/ archive. If you two and Motylek could tell me or Andrzej M (on-list or off-list) the IP numbers of computer(s) at JBO you are likely to use to access the site, then we would open up access to these IP #s. (The other existing lists have unrestricted access.) Pozdrawiam Boud

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Re: favoured topology of Universe candidates
by Boud Roukema 14 Feb '02

14 Feb '02

Hi again Ken & Ali, On Thu, 14 Feb 2002 Kengrimes123(a)aol.com wrote: > Thanks for that. We were rather shamefully going for the following 'quick > fix.' What do you think: The problem is that a spherical or hyperbolic, small universe would be just as exciting as a flat, small universe. The former might be more difficult to imagine, and there's more chance that Cornish et al would make errors or miss the real signal or take longer to find the result for a spherical or hyperbolic small universe than for a small, flat universe, but to me that's a secondary issue. (Using the circles principle in the most general way, the infinities of possibilities are not a problem for detection, however paradoxical that might seem!) Nevertheless, if what you really want to say is that a flat, small universe is in some ways "nicer" or "simpler" than a spherical or hyperbolic, small universe, then that is valid (and certainly defendable), but should probably be worded a bit more carefully. It would not really be that much more "hidden" from the measurement point of view, it would be more hidden simply because it's more complicated. I think the following is correct, clear and probably close to what you want to say: Replace: > 'So the universe may indeed be finite and bounded, and yet too vast to yield > to us the secret of its shape. Alternatively, the universe may possess > spherical or hyperbolic curvature, and so hide its secret shape among > limitless possibilities. Such thoughts are met with quiet stoicism by the > new wave of cosmologists: "The universe is however it is," Roukema > acknowledges, "Not how I would like it to be." by % 'So the universe may indeed be finite, bounded and flat, % and yet too vast to yield % to us the secret of its shape. Alternatively, the universe may be % small but possess % spherical or hyperbolic curvature, and so hide its secret shape among % limitless possibilities difficult for ordinary mortals to imagine % and challenging for professional % cosmologists to extract from the MAP data. Such thoughts ... And then the 2nd paragraph is fine unchanged: > But there remains the tantalising third possibility - that the universe is > relatively small, and possesses flat curvature. In that case, within a few > months of reading this article, we might well know whether Homer's donut is > truly the shape of things to come.' Cheers Boud

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Re: favoured topology of Universe candidates
by Boud Roukema 14 Feb '02

14 Feb '02

Hi again Ken & Ali, On Thu, 14 Feb 2002 Kengrimes123(a)aol.com wrote: > Thanks once again for the prompt feedback, which we would like to say was a > model in how to suggest quick and concrete improvements (if only more > contributors could do that!) We have gone for the simple expedient of > incorporating all of them. Great! Well, I've stoically ;-) learnt that careful, precise criticism tends to yield better results than general rants! > Please find below our proposed ending (featuring once more your good self - > and if you don't like the phrase 'quiet stoicism' we can go for 'cheerful > resignation' instead). We'd be very grateful if you could check this quickly, > as I think it probably repeats the 'howler' you picked out in your Point 5: > ' ... "If the universe is relatively large compared to its age,' > Levin observes, "I.e if it is significantly bigger than about 15 > billion light years across, then light from our ghost images will > not have time to reach us before the death of this planet." OK. > So the universe may indeed be finite and bounded, and yet too vast to yield > to us the secret of its shape. OK. > Alternatively, the universe may possess > hyperbolic curvature, and so hide its secret shape among limitless > possibilities. Hmm. Even though there are limitless possibilities for both the spherical and hyperbolic cases, as far as analysis of MAP data is concerned, the difference between them and the flat cases is "just" a question of calculation techniques and computer speeds. ("just" means a lot of hard work...) As you said in your article, Cornish et al. will calculate the easier cases first, simply because they're easier. The "limitless" or difficult classification of hyperbolic spaces just means it's much harder to analyse the data - the matched circles principle of Cornish, Spergel & Starkman is still perfectly valid. Just a reminder: the smallest "size" of the Universe could be: i) smaller than the horizon size (distance to last scattering surface) ii) about the same as the horizon (still maybe detectable) iii) much bigger than the horizon iv) infinite (There are in fact several "sizes" of the Universe which could be defined, the smallest one is the smallest distance between two images of the same object.) the curvature of the Universe can be: a) "slightly" spherical (like the Earth is "slightly" spherical) b) flat c) "slightly" hyperbolic There *is* some link between the two, [ a) => maximum size of Universe; b) => minimum size of Universe] but I think it's too subtle to include in your article, certainly too subtle for a conclusion. I think probably the closest correct thing to what you want to say is to compare the three possibilities: i) + ii) (put together) iii) iv) ---------------------------------------------------------------------- So here's my suggestion, to replace: > Alternatively, the universe may possess > hyperbolic curvature, and so hide its secret shape among limitless > possibilities. by % Alternatively, the universe may really be infinite and unbounded, % leaving us without the merest hope of being able to distinguish % between the two cases. ---------------------------------------------------------------------- > Such thoughts are met with quiet stoicism by the new wave of > cosmologists: "The universe is however it is," Roukema acknowledges, > "Not how I would like it to be." "quiet stoicism" and your quote are fine. :-) ---------------------------------------------------------------------- > But there remains the tantalising third possibility - that the universe is > neither vast nor hyperbolic. In that case, within a few months of reading To match the above correction: % neither vast nor infinite. In that case, within a few months of reading ---------------------------------------------------------------------- > this article, we might well know whether Homer's donut is truly the shape of > things to come.' Cheers Boud

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MAP time scale, courtesy Ken & Ali
by Boud Roukema 14 Feb '02

14 Feb '02

Dear friends, For copyright reasons I probably shouldn't post Ken & Ali's full article here, but here are a couple of paragraphs which are pretty important: > But how can we spot these circles? From 1989-93, NASA's Cosmic > Background Explorer (COBE) mapped the microwave sky, and found that > it's not a perfect 3 Kelvin everywhere - there are slight fluctuations > in its temperature. Cornish, along with his collaborators David > Spergel of Princeton University and Glenn Starkman of Case Western > Reserve University in Cleveland, Ohio, thinks that searching for > patterns in these fluctuations may be the key to finding out the > universe's shape. > > The team hopes to trace out different temperature patterns along > circles, and then find the same pattern along another circle elsewhere > in the sky. Patterns of temperature around one circle should be > identical to another, says Cornish. The precise pattern of circles > will indicate the fundamental polyhedron's shape. > > COBE's achievement in making the first map of the microwave sky was > impressive. But the map wasn't quite detailed enough for > pattern-spotting. NASA's Microwave Anisotropy Probe (MAP), launched > last year, will map the microwave sky in unprecedented detail, > providing the data that Cornish, Spergel and Starkman need for their !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! > search. MAP will complete its first complete scan in March and then we > can begin our analysis, says Spergel. We hope to have the results by > the end of the year. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Of course, it's quite possible that they'll make too many simplifying assumptions or that the integrated Sachs-Wolfe effect (between us and the last scattering surface) or "foregrounds" will cause too much confusion and lead to a false exclusion (more likely than a false detection), so Planck might still have a chance. But Archeops data would clearly be the best competitor for MAP: 25% of the sky is not that far off from 67% of the sky... Cze�� Boud

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Re: favoured topology of Universe candidates
by Boud Roukema 14 Feb '02

14 Feb '02

Hi Ken & Ali, On Wed, 13 Feb 2002 Kengrimes123(a)aol.com wrote: > Please find attached as requested our latest draft of the article, which we > will be forwarding to our editor this Friday. Great! > We fear you may be somewhat disappointed with the finished product, since, as > you can see, we have not managed to cover the 'psychological crutch' aspect > of the 4th dimension. Although we found this discussion most interesting, we > simply found it impossible to fit into a popular account with a strict word > limit which had to cover so much other material. Our apologies. On the contrary, my general opinion of your article is that you've done a good job of making a simple as possible introduction to the subject and of covering the variety of research done in Europe/North America, given a non-expert background and a finite ;-) amount of time to learn the subject. (Including the several Brazilians and one Japanese researcher would have been fair, but would have required more time and reading and would have been difficult within the word limit.) I think there are several small changes that can be made in order to be correct about the "psychological crutch" aspect, which I've listed below as (1). These would only add a dozen or so words. Since I'm convinced that you've made an effort to try to understand the question - but probably without (yet) succeeding (it might happen sometime when you're in the shower or on summer holidays and daydreaming or whatever - and you'll suddenly say, of course!), I certainly won't hold it against you if you prefer not to make these changes. After all, only you two are signing it, not me! But I think it would be both in readers' and researchers' interests if if you did consider my suggested changes... There are also a few other corrections I've suggested. > We would, of course, still be most interested in any comments you might like > to offer (especially if we've made any howlers!) In the meantime, we would > like to take the opportunity to thank you for the time, interest and support > you have given us on this project. The most fun part of science is understanding the Universe, and helping others to understand the same things. Your help in transmitting this to others is definitely worth it. It's been a pleasure to work together. :-) All the best Boud ---------------------------------------------------------------------- (1) The "psychological crutch" aspect of the 4th dimension. (2) What are "photons"? (3) topological images of galaxies, not stars (4) Recent constraints show Universe flat like continents are flat (5) Infinitely many spherical spaces ---------------------------------------------------------------------- > This hard-to-visualise fourth dimension is particularly intriguing to > cosmologists because, if it exists, then the universe might be curved > within it. An immediate critique of this idea is that, to the best of (1) I would put: ... % cosmologists because it could be used to help imagine how the universe % might be closed. An immediate critique of this idea is that, % to the best of ---------------------------------------------------------------------- > joined to each other simultaneously [EXAMPLE AT ABOVE URL, PAGE 2]. If > this `cube' were the entire space of our three-dimensional universe, > then the bending operation, possible only in a fourth dimension, would (1) I would put: ... % then the bending operation, which can be imagined by using % a fourth dimension, would ---------------------------------------------------------------------- > began. The same would be true for our closed, curved, > higher-dimensional universe. Like an Asteroids-type starship, any (1) I would put: % began. The same would be true for our closed % universe. Like an Asteroids-type starship, any or % began. The same would be true for our closed % universe thought of inside a higher-dimensional artificial universe. Like an % Asteroids-type starship, any ---------------------------------------------------------------------- > The term any object includes, of course, photons. (2) I think that there are probably 10-100 times more people who have some notion of both "light" and "particles" but haven't the foggiest about "photons", so why not help enlighten them: % The term any object includes, of course, photons (particles of light). ---------------------------------------------------------------------- > In a closed, curved universe, (1) I would put: % In a closed universe (which could sort of be thought of as curved) ---------------------------------------------------------------------- > light itself would describe a curved path, eventually (1) I would put: % light itself could sort of be thought of describing a curved path, % eventually ---------------------------------------------------------------------- > The implications for contemporary cosmology are truly staggering. When > we look up at the night sky, it is possible that what we are seeing is > not a single, vast or infinite number of stars, but the same finite > set of stars repeated throughout the sky, like torchlights in a hall (3) You probably know that you're making an error here, with the goal of simplicity. We are certain that the size of the Universe is much bigger than our Galaxy - none of the stars we see with the naked eye are repeated, topological images of one another. (Unfortunately!) What solutions are possible to try to be correct without sacrificing understandability to the ordinary reader? Replacing "stars" by "astrophysical objects" would be correct but sound heavy and academic. In French you could use the word "astre" which is short and snappy and means an arbitrary object in the sky. But you're not writing in French. ;-) How about: % The implications for contemporary cosmology are truly staggering. When % we look up at distant galaxies in the night sky, % it is possible that what we are seeing is % not a single, vast or infinite number of galaxies, but the same finite % set of galaxies repeated throughout the sky, like torchlights in a hall ---------------------------------------------------------------------- > observations suggest that the universe is flat. (4) More accurate would be: % observations suggest that the universe is pretty close to flat, like % any continent on the Earth is pretty close to flat. ---------------------------------------------------------------------- > The number of contenders for shapes which could tile a flat or > spherical universe is limited, but a hyperbolic universe offers (5) A "howler", at least from the mathematical point of view! ;-) The number of shapes (in 3D) for both the spherical and hyperbolic cases is infinite [in mathematical jargon, these are both countable infinities, i.e. the same type of infinity as that of the ordinary counting numbers: 1,2,3,4,5, ...]. I made the *error* (published, I think) of repeating the claim by someone else (who I won't name) who said that the number of hyperbolic spaces is a bigger sort of infinity than the infinity of the spherical spaces. From Jeff Weeks' explanation, I accepted that this is wrong. It is true (as far as I understand) that the hyperbolic spaces are not yet completely classified by mathematicians, and their families are certainly more complicated in certain ways, while the spherical spaces are completely classified and form relatively simple families. But both numbers of spaces are infinite. I suggest: % The number of contenders for shapes which could tile a flat % universe is limited, but a spherical or hyperbolic universe would offer ----------------------------------------------------------------------

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Re: favoured topology of Universe candidates
by Boud Roukema 11 Feb '02

11 Feb '02

On Sat, 9 Feb 2002 Kengrimes123(a)aol.com wrote: > Could you please confirm your title and institution for the Astronomy > article? Dear Ken & Alison, Title: Dr Institution (full name): Torun Centre for Astronomy, Nicholas Copernicus University International linguistic trivium: The "n" in Torun should have a "grave accent" on top, i.e. a forward slanting accent, like the accent on top of "e" in "�t�" ('et'e, = "summer" in French). > Date: Fri, 25 Jan 2002 16:51:33 EST > From: Kengrimes123(a)aol.com > To: boud(a)astro.uni.torun.pl > Subject: Re: favoured topology of Universe candidates > > Sorry for the hiatus. We thought, 'We'll get back to Boud as soon as we've > got our heads round this.' Still trying! Did you get anywhere with this? I admit that in my case it took many years between learning about the existence of non-Euclidean geometry and developing an intuition in which I was satisfied that this was possible without needing an extra dimension. (The latter time happened to be when I attended a course on algebraic topology.) During the intervening time, I accepted that people were probably correct in their claims, but it was rather unsatisfying. My hope is that with proper explanation, the period of years could be replaced by the space of an hour or so..., or, at least, an hour or so of initial reading followed by a week of deep thought and playing with idea in one's mind... I'm sure that playing with the games on Jeff Weeks' site that I referred you to should help. Don't be embarrassed to play games - understanding is not a matter just of cold logic, it also requires intuition via the chaotic process of a neural network. Playing games is what mathematicians do most of the time. Since you're both journalists, probably the word games that Jeff has provided would sink deepest into the cores of your minds. E.g. try the games http://humber.northnet.org/weeks/TorusGames/html/WordSearch.html http://humber.northnet.org/weeks/TorusGames/html/Crossword.html with Java and auto-image-load enabled (this is probably the case by default). And try them with the "Klein bottle" setting! Try to "unlearn" what you thought you knew about physics, just have fun playing the games instead. Imagine you're really living in the WordSearch.html, like a good movie. And then, chances are a moment will occur when, all of a sudden, you'll realise that a multiply connected flat space makes perfect sense without needing an extra dimension... > Thanks, Ken & Alison. BTW, would you be able to run the final version of the draft text by me, at least the part of the text regarding our discussions? You would of course be free to ignore or follow my comments as you wish, but it would be good that I have the chance to at least make my suggestions. Cheers Boud

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