Cosmo-torun

cosmo-torun@cosmo.torun.pl

328 discussions

11:00 Mon 28 May 2012: Narlikar - Highlights of an alternative cosmology
by Boud Roukema 16 Apr '12

16 Apr '12

hi cosmo-torun, Here are the details of Jayant's seminar: Title: Highlights of an alternative cosmology Speaker: Jayant Narlikar [1] Abstract: (tbd) Time/date: 11:00 Monday 28 May 2012 Place: KRA, Torun Centre for Astronomy [2] [1] http://www.iucaa.ernet.in/~jvn [2] http://www.astro.umk.pl/?lang=en cheers boud

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ok
by ostjan＠stud.umk.pl 22 Mar '12

22 Mar '12

fine with me

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cosmo books [was: Re: Fw: Kosmos]
by Boud Roukema 22 Mar '12

22 Mar '12

witam cosmo-torun On Thu, 22 Mar 2012, Biblioteka CA UMK wrote: > Mam prosbe o popatrzenie na zalacznik - czy taka ksiazka-album o Kosmosie > znajdzie wsrod Panstwa czytelnikow. ... >> W nawiazaniu do rozmowy telefonicznej przesyłam w załączniku dodatkowe >> informacje na temat wspaniałego albumu Gilesa Sparrowa - KOSMOS. >> Zapraszam na www.kmktychy.pl Talking about the "edge of space" in an abstract to a popular astronomy+cosmology book http://www.amazon.com/Cosmos-Giles-Sparrow/dp/1905204299 seems like a bad pedagogical strategy to me. We need to understand the observer's point of view, but our standard model is based on an underlying spacetime (pseudo-4-manifold + metric that solve the Einstein equations), not just a past time cone. It might be nice as a "coffee table book" - it's motivational to see big beautiful pictures. On the other hand with a small (zero) budget, i would tend to go for research/teaching-level books. At the moment we have three books listed on our wiki - please anyone update the wiki page: http://cosmo.torun.pl/foswiki/bin/view/Cosmo/BibliotekaCosmo what we want * Padmanabhan, 1993 Structure Formation in the Universe * Schilpp 1949 Albert Einstein: philosopher-scientist * Bolejko et al 2009 Structures in the Universe by Exact Methods Schilpp 1949 has the Infeld cosmic topology comment about electromagnetism - apparently the first person to talk about physical "effects" of cosmic topology. pozdr boud

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kashlinsky large-scale flow
by Boud Roukema 16 Mar '12

16 Mar '12

hi cosmo-torun, During today's Sprawozdanie, Bronek asked about the Kashlinsky large-scale high-velocity flow. You'll find Kashlinky's work referred to in the paper below, which is an interesting observational analysis according to which the flow is due to using an incorrect choice of the comoving coordinate reference frame. Wiltshire et al's argument is based on Wiltshire's approach to modelling the Universe in a more relativistically correct way than the FLRW ("standard") metric, i.e. one of the "inhomogeneous" approaches to cosmology (according to which the Earth is assumed to exist). http://arxiv.org/abs/1201.5371 Hubble flow variance and the cosmic rest frame Authors: David L. Wiltshire, Peter R. Smale, Teppo Mattsson, Richard Watkins pozdr boud

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cosmo workshop Fri 2 March @15.00 @KRA: Jan Ostrowski on Cactus: numerical relativity
by Boud Roukema 02 Mar '12

02 Mar '12

hi cosmo-torun Cactus: numerical relativity cosmo workshop Fri 2 March @15.00 @KRA Jan Ostrowski Jan is doing very interesting work in finding out how to do numerical relativity. One way of saying it is the following: "Normal" cosmological N-body simulations consist of *Newtonian* gravity simulated on a highly simplified (perfectly homogeneous) relativistic "background". In formal scientific language, this is called a "heuristic" approach; in informal language, it's called "a fudge" - it's a mathematical shortcut that seems like it should work and lets us quickly compare some sort of "model" to observations instead of waiting 50 years for the mathematics to be solved. In principle, every scientist using the heuristic/fudge is aware of this. Pure theory is very difficult to apply to the real world. Relativistic cosmological simulations should be "directly" relativistic, consistent with the Einstein equations, without using the heuristic/fudge of adding "perturbations" that obey Newtonian gravity to a relativistic "background". So these simulations can be called "background-free". How can we do background-free cosmology simulations? Jan will present a discussion on this. pozdr boud

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grey extinction
by Boud Roukema 27 Feb '12

27 Feb '12

Witam After this morning's seminar, here seem to be a few articles on grey extinction and the \ddot{a}/a > 0 interpretation of the SNe Ia experiments: http://arxiv.org/abs/0909.0231 Grey Milky Way Extinction from SDSS Stellar Photometry Authors: Evgeny Gorbikov, Noah Brosch http://arxiv.org/abs/astro-ph/0701259 Redshift-distance relations from type Ia supernova observations. New constraints on grey dust models Authors: A.R. Robaina, J. Cepa http://arxiv.org/abs/astro-ph/0603833 The Impact of Cosmic Dust on Supernova Cosmology Authors: Pier Stefano Corasaniti http://arxiv.org/abs/astro-ph/0505446 No evidence of "gray" dust from composite quasar spectra Authors: Chris J. Willott http://arxiv.org/abs/astro-ph/0410501 Limiting the dimming of distant type Ia supernovae Authors: Linda Ostman, Edvard Mortsell http://arxiv.org/abs/astro-ph/0306459 Extinction by grey dust in the intergalactic medium Authors: Ernst Fischer pozdr boud

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Maciej Bilicki 2MASS talk Thurs 10.00 g @CAMK
by Boud Roukema 24 Jan '12

24 Jan '12

hi cosmo-torun, i don't if everyone got this: http://www.ncac.torun.pl/?lang=pl&branch=world&id=3#najblizsze 2012-01-26 mgr Maciej Bilicki (CAMK Warszawa) Kosmologia z przeglądem 2MASS Seminaria Czwartkowe mają miejsce w kamieniczce Centrum Astronomicznego im. M. Kopernika PAN w Toruniu (ul. Rabiańska 8), w sali seminaryjnej. Rozpoczynają się o godzinie 10:15. Seminaria odbywają się w języku polskim bądź angielskim i trwają około 45 minut. Zagadnienia poruszane obejmują szeroki zakres astronomii, astrofizyki, kosmologii oraz fizyki. Z tego względu, Seminaria Czwartkowe są polecane m.in. studentom astronomii i fizyki. Kawa, herbata i pączki są serwowane o godz. 10:00. pozdr boud

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Higgs boson excluded at 2 sigma by ATLAS: arXiv:1112.2577
by Boud Roukema 13 Dec '11

13 Dec '11

hi cosmo-torun The mainstream media say that a seminar will take place this afternoon at CERN for the ATLAS and CMS groups. This seems to be the ATLAS paper. Can anyone find the CMS paper? http://arxiv.org/abs/1112.2577 Search for the Higgs boson in the H->WW(*)->lvlv decay channel in pp collisions at sqrt{s} = 7 TeV with the ATLAS detector Authors: ATLAS Collaboration (Submitted on 12 Dec 2011) Abstract: A search for the Higgs boson has been performed in the H->WW->lvlv channel (l=e/mu) with an integrated luminosity of 2.05/fb of pp collisions at sqrt{s} = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110<mH<300 GeV. The observations exclude the presence of a Standard Model Higgs boson with a mass 145<mH<206 GeV at 95% confidence level. pozdr boud

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cosmic topology workshop 14-15.00 Fri 9 Dec: Zbyszek Bulinski
by Boud Roukema 09 Dec '11

09 Dec '11

witam cosmo-torun Cosmic topology workshop 14-15.00 Fri 9 Dec @KRA: Zbyszek Bulinski. Since this list is public, i won't give details of Zbyszek's topic - this work is so far unpublished ;). This is meant to be informal, interactive, it may become a practical "do stuff" workshop - we'll see. Sebastian's "young students" are visiting KRA this week and Marian apparently has a lecture/pracownia on Friday afternoon, so i don't yet know if we'll have the main seminar room or the one next to the guest rooms. Hoping to see many of the cosmology group together on Friday. :) pozdr boud

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festiwal nauki i sztuki april 2012 - deadline Mon 21 nov
by Boud Roukema 18 Nov '11

18 Nov '11

hi everyone, If anyone other than Tomek and Jan are interested, please add your name and edit and improve the proposal: http://cosmo.torun.pl/foswiki/bin/view/Cosmo/FestiwalNauki2012 pozdr boud

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NVSS velocity dipole 4 times bigger than CMB velocity dipole, but same direction
by Boud Roukema 31 Oct '11

31 Oct '11

hi cosmo-torun There's a very interesting paper by Ashok Singal from Ahmedabad: Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources Authors: Ashok K. Singal http://arxiv.org/abs/1110.6260 The principle and method are essentially straightforward, the data set is public and the analysis looks simple. The result is that the NVSS velocity dipole for faint radio sources is 4 times bigger than the CMB velocity dipole, but in about the same direction. My speculation is that somewhere there was a multiplication by two instead of dividing by two, but i didn't find it from a quick browse through the paper. If there is no error, then this sounds like a rather huge, large-scale bulk velocity. pozdr boud

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invisible Invisible Universe proceedings...
by Boud Roukema 21 Sep '11

21 Sep '11

hi cosmo-torun, Does someone have my physical copy of the Invisible Universe conference (UNESCO/Paris) proceedings? I seem to remember that someone borrowed it but i don't remember who. The Invisible Universe has become... invisible. :P Please let me know if you have it. pozdr boud

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Lustrzany dwunasto'scian foremny jako analogia przestrzeni dwunasto'sciennej Poincar'e
by Boud Roukema 26 Aug '11

26 Aug '11

Witam Złączany jest propozycja grupa kosmo dla visiting centre, w formacie odt i pdf. Dodawałem nazwe ludzi, którze dali konkretne pomysły i poprawki. pozdr boud

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visiting centre cosmo proposal
by Boud Roukema 24 Aug '11

24 Aug '11

hi cosmo-torun, We have just two and a half days left to propose a cosmology hands-on project for the proposed TCfA visiting centre. IMHO a mirror-lined dodecahedron is a relatively easy to construct possibility and gives visitors something of a concrete intuitive example of a multiply connected space (despite the problems in the analogy): Please update the wiki directly: http://cosmo.torun.pl/foswiki/bin/view/Cosmo/TCfAVisitingCentre pozdr boud

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admin: iuventus-plus for people <= 35 yrs old
by Boud Roukema 26 Jul '11

26 Jul '11

witam For people <= 35 yrs old, there's a funding program called "iuventus-plus": http://www.nauka.gov.pl/ministerstwo/inicjatywy-ministerstwa/programy-minis… Can someone see where the deadline for applying is? Please reply *publicly* if you do, since it's useful info for most of the young Torun cosmologists. More grant info (update if needed): http://cosmo.torun.pl/Cosmo/AdminGranty pozdr boud

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CAMK workshop this week: 12-17 lipca 2011: Cosmic web morphology and topology
by Boud Roukema 11 Jul '11

11 Jul '11

hi cosmo-torun, There's a CAMK workshop *this* week: 12-17 July 2011: Cosmic web morphology and topology http://users.camk.edu.pl/pchela/workshop/ Here, "topology" means 2D topology of constant density surfaces embeded in 3D space, not 3D topology of 3D spaces. This is about the cosmic web, meaning the filaments and knots of mostly dark matter and some baryonic matter on scales of about 10-100 Mpc. Most of you have seen the animation of a simulation of this that i show fairly often. Observations of the cosmic web include clusters at the "knots" of the web (e.g. observed by OCRA through the SZ effect) and the Lyman-alpha forest - clouds of neutral hydrogen that absorb background quasars. i don't expect any problem with informal participation, but send an email to Wojtek Hellwing (see the website) to briefly introduce yourself. You can make a day trip to Warsaw - leave early morning and return e.g. with the 18.45+(n>1 * 10 minutes) train - or stay overnight at a friend's place and see several days of talks. The talks look mostly (but not only) theoretical to me, and based on the FLRW model + perturbations, not the inhomogeneous approach. This is an easy opportunity to meet some international extragalacticians/cosmologists. pozdr boud

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n-body review 1106.1082v1, correction by Adrian Melott 1105.1774
by Boud Roukema 11 May '11

11 May '11

hi cosmo-torun, These two articles may be useful especially for Zbyszek and Bartek: * n-body review http://arxiv.org/abs/1106.1082v1 Dehnen and Read * correction by Adrian Melott http://arxiv.org/abs/1105.1774 i'm not sure if there's anything especially new in 1106.1082, but figs 5 and 6 look nice, and reading a review paper you can often find something you didn't know before. pozdr boud

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kpc-scale triple AGN: arXiv:1104.3391 Liu, Shen, Strauss
by Boud Roukema 22 Apr '11

22 Apr '11

witam cosmo-torun This should be interesting especially for AGN people: http://arxiv.org/abs/1104.3391 Cosmic Train Wreck by Massive Black Holes: Discovery of a kpc-Scale Triple Active Galactic Nucleus Authors: Xin Liu, Yue Shen, Michael A. Strauss pozdr boud

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fitting LT models to data: new Bolejko et al paper arXiv:1102.3370
by Boud Roukema 22 Feb '11

22 Feb '11

hi cosmo-torun http://arxiv.org/abs/1102.3370 The Metric of the Cosmos from Luminosity and Age Data Krzysztof Bolejko, Charles Hellaby, Alnadhief H. A. Alfedeel This is an algorithm for using LT models to construct a metric from apparent magnitude and maximum stellar age data (as an alternative to forcing an FLRW model onto the data). Graphs of estimates of Omega_m(r) and t_Bang(r) are in Figs 7 and 8. pozdr boud

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Bolejko arxiv:1101.3338
by Boud Roukema 19 Jan '11

19 Jan '11

hi everyone, A different problem in using a more accurate metric than the FLRW metric is how we interpret the CMB. The following seems to be the first paper on this. Since "real" calculations are difficult, the approach seems to be to test various toy model calculations that at least show how much things could change compared to FLRW + Concordance parameter values. The answer in this case is not Omega_Lambda = 0, but since these are toy models, i don't think this is a claim that Omega_Lambda != 0. What Krzysztof does argue is that \Delta \Omega_\Lambda_{\mathrm{sys}} \gg 0.01. The effect of inhomogeneities on the distance to the last scattering surface and the accuracy of the CMB analysis - Krzysztof Bolejko http://arxiv.org/abs/1101.3338 pozdr boud

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the Universe is old and old age caught up with Allan Sandage :(
by Boud Roukema 19 Nov '10

19 Nov '10

hi everyone, I think I heard at least one conference talk by Sandage. Some of the more senior people here may have known him better. I'll just quote the Wikipedia summary for the younger people among us: Allan Rex Sandage (born June 18, 1926 in Iowa City, Iowa, died November 13, 2010) was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe. http://en.wikipedia.org/wiki/Allan_Sandage pozdr boud

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a fourth neutrino (sterile neutrino)?
by Boud Roukema 05 Nov '10

05 Nov '10

hi everyone, Even if the electron, tau and muon neutrinos are usually considered to be of too low mass to be relevant for non-baryonic dark matter, it looks like there are several hints that a fourth, "sterile" neutrino exists: http://cosmocoffee.info/viewtopic.php?p=4864 It's not clear to me what this could/would imply for the sterile neutrino's mass... pozdr boud

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highest spectroscopically confirmed redshift: z = 8.6 Lehnert et al. 1010.4312
by Boud Roukema 25 Oct '10

25 Oct '10

hi everyone, We're still a long way from galaxy/qso redshifts of 20 to 30, but we're getting towards 10: Spectroscopic confirmation of a galaxy at redshift z=8.6 Lehnert et al. http://arxiv.org/abs/1010.4312 By comparing to other high z galaxies, the stellar age is suggested to be in the range 0.01 to 0.1 Gyr. pozdr boud

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arXiv:1010.1634 neural-network removal of WMAP foregrounds
by Boud Roukema 11 Oct '10

11 Oct '10

hi cosmo-torun, Foreground removal from WMAP 5yr temperature maps using an MLP neural network Authors: H. U. Norgaard - Nielsen http://arxiv.org/abs/1010.1634 This looks cool! i've just read it very briefly... My initial understanding is that it's like an ILC map but without the arbitrary definition of "regions". pozdr boud

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14.00 Fri 8.10.10 cosmo group web pages workshop
by Boud Roukema 06 Oct '10

06 Oct '10

hi everyone, Cosmo workshop! This Friday: When, where: 14.00 Fri 8.10.2010, @KRA. Topic: cosmology group web pages. i'll try to set up a switch so that people with laptops can edit simultaneously, but anybody is still welcome to participate without a laptop. Just by seeing people edit "live" may help you get the basic idea. At 15.00, following the wiki workshop and a short break, there'll be a cosmic topology workshop. pozdr boud

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