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19 discussions

Helio Fagundes
by Boud Roukema 01 Aug '19

01 Aug '19

hi cos-top For those who haven't heard the news yet, Helio Fagundes passed away on 30 July. For those not fully familiar with his pioneering work in pushing for cosmic topology as an observational field within cosmology/extragalactic astronomy, here is the ADS list of his work: https://ui.adsabs.harvard.edu/search/q=%20author%3A%22fagundes%2C%20h%22&so… His first paper with a closed hyperbolic spatial section and an urge to make observational tests with quasars seems to be his 1982 paper: https://ui.adsabs.harvard.edu/abs/1982LMaPh...6..417F Boud

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hyperbolic 3D spaces with cubical FDs?
by Boud Roukema 04 Mar '19

04 Mar '19

hi cos-top Do there exist any hyperbolic multiply connected constant-curvature compact spaces for which the fundamental domain is a cube (with flat faces, of course) for some points in the space? Or is there a proof that this is impossible? We know that there are (at least) two such spherical spaces, that Peter Kramer calls C_2 and C_3: Kramer09: https://ui.adsabs.harvard.edu/#abs/2009PhyS...80b5902K/ Are there any hyperbolic ones? Cheers Boud [Reminder - this is an opt-in list - you can get info at http://cosmo.torun.pl/mailman/listinfo/cos-top for unsubscribing or subscribing; information should be included in this email for doing these or other operations via email.]

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Please post: Royal Astronomical Society Specialist Discussion meeting on topology Dec 13
by Glenn Starkman 05 Nov '13

05 Nov '13

Date: 13 Dec 2013 Time: 10:30am Location: Burlington House, London < http://www.ras.org.uk/about-the-ras/burlington-house> We are pleased to announce a Royal Astronomical Society Specialist Discussion meeting on topology. General relativity connects the local geometry of spacetime to the energy contents, but the topology of space is unconstrained. Moreover, it is expected that any theory linking quantum mechanics and relativity is likely to exhibit topology change at scales that may have become cosmologically relevant. Cosmological observations have shown that the Universe is very nearly flat, and that the topology is trivial nearly out to the last scattering surface, but we have no direct measurement of its topology on scales larger than that. This discussion meeting will give an overview of current research in mathematical topology, its application to cosmology and particle physics, and a discussion of recent observations from Planck and other missions. Confirmed keynote speakers include Jeff Weeks (independent) and Philip Candelas (Oxford).

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eight cosmic topology papers for first semester 2013
by Boud Roukema 23 Jun '13

23 Jun '13

hi cos-top, Cosmic topology seems to be turning into a hot topic: we have at least eight papers - a mix of observational and theoretical papers - listed by the ADS for 2013. Feel free to reply to add any missing papers to this list! http://cdsads.u-strasbg.fr/abs/2013arXiv1306.2737F A search for nontoroidal topological lensing in the Sloan Digital Sky Survey quasar catalog Authors: Fujii, Hirokazu; Yoshii, Yuzuru http://cdsads.u-strasbg.fr/abs/2013arXiv1305.5576B Solving the Einstein constraints in periodic spaces with a multigrid approach Authors: Bentivegna, Eloisa http://cdsads.u-strasbg.fr/abs/2013arXiv1304.1811A The Topology and Size of the Universe from CMB Temperature and Polarization Data Authors: Aslanyan, Grigor; Manohar, Aneesh V.; Yadav, Amit P. S. http://cdsads.u-strasbg.fr/abs/2013arXiv1303.5086P Planck 2013 results. XXVI. Background geometry and topology of the Universe Authors: Planck Collaboration http://cdsads.u-strasbg.fr/abs/2013arXiv1303.4226A A search for cosmic topology in the final WMAP data Authors: Aurich, Ralf; Lustig, Sven http://cdsads.u-strasbg.fr/abs/2013arXiv1302.6537B Wave computation on the Poincar\'e dodecahedral space Authors: Bachelot-Motet, Agnes http://cdsads.u-strasbg.fr/abs/2013arXiv1302.4425R Deep redshift topological lensing: strategies for the T^3 candidate Authors: Roukema, Boudewijn F.; France, Martin J.; Kazimierczak, Tomasz A.; Buchert, Thomas http://cdsads.u-strasbg.fr/abs/2013PhRvD..87d3521R Topological implications of inhomogeneity Authors: Roukema, Boudewijn F.; Blanloeil, Vincent; Ostrowski, Jan J. Cheers Boud

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half-turn space analysis; new spherical 3-manifolds ?
by Boud Roukema 11 May '12

11 May '12

hi cosmic topologists, Today we have *two* cosmic topology articles on arXiv on the same day! (1) http://arxiv.org/abs/1009.5880 Cosmic microwave anisotropies in an inhomogeneous compact flat universe Authors: R. Aurich, S. Lustig This shows that the half-turn space E_2 also seems to provide a nice fit, at least with the S_60deg statistic, to the WMAP 7yr data, and it even seems to be a bit better than T^3. (2) http://arxiv.org/abs/1009.5825 Multipole analysis in cosmic topology Authors: Peter Kramer This seems to claim that the author has found 3 new spherical 3-manifolds, "N8, N9, N10". It's not clear to me if he claims that they can be given constant curvature, but maybe it's obvious to someone who knows the mathematics a bit better. i had thought that the constant curvature spherical 3-manifolds were already completely classified. Are N8, N9, and N10 new constant-curvature spherical 3-manifolds, in addition to those in Gausmann et al. 2001 http://arxiv.org/abs/gr-qc/0106033 ? cheers boud

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recent cosmic topology work
by Boud Roukema 07 Apr '09

07 Apr '09

hi everyone on cos-top, The Ulm group continue to work on T^3 models - here's a nice new paper: http://arXiv.org/abs/0903.3133 Other news: there's an observational signature of cosmic topology which occurs for flat compact models but not for curved compact models (assuming standard physical components of the Universe in both cases). The good news for cosmic topology in general: this observational signature has been detected to extremely high significance! :) The bad news for the Poincare space: this observational signature has been detected to extremely high significance! :( Details: http://arxiv.org/abs/0904.0975 A Poincare space is certainly not excluded by the argument, but it would require an exotic explanation for the observational signature rather than a simple explanation. Occam's razor suggests that we may have to accept T^3 (or another flat compact space). Anyway, see the paper to find out what this observational signature is. cheers boud

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the Poincare dodecahedral space is better balanced than other spaces
by Boud Roukema 20 Feb '09

20 Feb '09

Dear cos-top friends, It seems that not only is there at least some interaction between cosmic topology and gravity - the residual gravity acceleration effect as derived heuristically for the 1-torus and 3-torus[1], but the effect distinguishes 3 well-proportioned spaces (T^3, S^3/T^*, S^3/O^*) as special in that the effect cancels to third order in the Taylor expansion, and even more interesting, the Poincare dodecahedral space cancels even better than these other three well-proportioned spaces. The effect in S^3/I^* cancels down to fifth order in the Taylor expansion![2] In this sense, it's better balanced than the other spaces. Maybe we could say that the former three spaces are well-proportioned and "well-balanced", while the Poincare space is well-proportioned and "super-well-balanced"? This dynamical/geometrical/topological result is independent of the empirical arguments in favour of the Poincare space. Enjoy! :) boud PS: There'll be a cosmic topology session at the 12-th Marcel Grossmann Meeting in Paris, 12-18 July 2009. http://www.icra.it/MG/mg12/en/ Contact Marek Demianski and register if you're interested. [1] RBBSJ, 2007, http://arxiv.org/abs/astro-ph/0602159 Astron.Astrophys.463:861 [2] RR 2009, http://arxiv.org/abs/0902.3402, subm A&A

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draft of a response to Steven Weinberg's "Cosmology" page 9
by Boud Roukema 08 Jun '08

08 Jun '08

Dear Marcelo, everyone, The topic of Steven Weinberg's rather not-fully-accurate page 9 of his new book is IMHO rather well-suited to discussing on our public mailing list rather than privately - this has nothing to do with revealing unpublished results that we're still working on, it's about correcting some inaccurate statements regarding cosmic topology. i also think it would be worth it that the effort we spend in explaining things to Steven Weinberg can potentially help educate others directly, i.e. those who may read the mailing list archives or get pointed there by Big Brother Google Inc. An alternative (and reasonable) place to discuss this IMHO would be http://cosmocoffee.info, which is a phpBB based forum for cosmology research in general, while this mailing list is a mailman mailing list specifically for cosmic topology. Anyway, to people who do not have a copy of the book "Cosmology" published by Steven Weinberg a few days/weeks ago, just email one of us in private and we can send you a scan of page 9 ("for educational and research purposes only", to avoid any problems with copyright etc.). My general opinion: Yes, i think it would be a good idea to send a message to Steven, and a consensus message signed by several of us would be a good idea. However, it would require a bit of work, since ideally it should be: * clear * complete * well-referenced * but also... reasonably short This is not so easy, especially keeping it short while satisfying the first three criteria... i've posted a suggested draft on our wiki: http://cosmo.torun.pl/Cosmo/SWeinbergCosmologyPage9Response and i'm also posting the same initial draft text below here. Personally, i don't see that there's a huge hurry - i don't imagine OUP issuing a second edition on a time scale of days or weeks - so i haven't suggested any time scale. My suggestion is we give people a week or so to update/correct/ complain. If we wait too long, it will soon by the northern summer break and not much point expecting anyone to respond quickly. If you want to correct/edit my suggested text and/or sign it, please speak up! i've tried to be complete in the reference list while limiting to the precise problems in Steven's text. cheers boud suggested text, openly editable at http://cosmo.torun.pl/Cosmo/SWeinbergCosmologyPage9Response ---------------------------------------------------------------------- Dear Steven, We are glad that your cosmology text published by Oxford University Press a few months ago (March 2008) is, to the best of our knowledge, the first graduate level type cosmology text in which it is clearly stated that there are many more than three possible shapes for the spatial section of our Universe, assuming that the Friedmann-Lemaitre-Robertson-Walker metric is correct apart from density perturbations. Nevertheless, some of the statements on page 9 of your book are probably not as accurate as they could be. Here are some suggestions which should hopefully clarify these issues. 1. "There is no sign of [the same patterns of the distribution of matter and radiation in opposite directions] in the observed distribution of galaxies or cosmic microwave background fluctuations, so any periodicity lengths such as |L_i| must be larger than about 10^10 light years." * It is correct that based on cosmic microwave background constraints (WMAP), it is clear that the in-diameter of the Universe (see e.g. Fig. 10 of Luminet & Roukema 1999 for various definitions of the comoving size of the Universe) is greater than 2 h^-1 Gpc. * However, on a scale of about 12-15 h^-1 Gpc, a large number of papers have been recently published which suggest that, in particular, a Poincare dodecahedral space (for K=+1) or an equi-length 3-torus model (for K=0) better fit the WMAP data than an infinite K=0 model. There is not yet any clear consensus on what the data tell us - some papers argue that the infinite K=0 model cannot be significantly rejected based on the WMAP data. Please see the reference list below for the main papers in this series. 2. "[Most 3-manifolds] ... seem ill-motivated. In imposing conditions of periodicity we give up the rotation (though not translation) symmetry that led to the Robertson-Walker metric in the first place, so there seems little reason to impose these periodicity conditions while limiting the local spacetime geometry to that described by the Robertson-Walker metric." * This is a little unclear. If by "symmetry" you mean the existence of isometries in the covering space, then there are no global translation symmetries at all for K=-1 or K=+1. Translations only exist for K=0. (Clifford translations exist for some K=+1 spaces, but that's a separate issue.) If you want to retain translational isometries in 3-space, then only K=0 is possible, and your words would seem to describe both K=-1 and K=+1 simply connected spaces as "ill-motivated". * More importantly, the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric only requires local homogeneity and isotropy, not global homogeneity and isotropy. The FLRW metric is intrinsically local, it's about the limit of what happens towards a point. To write this in terms of practical observational cosmology statistics, consider a more realistic model of the Universe, i.e. with a perturbed FLRW metric rather than a perfectly homogeneous one. In this model, "local homogeneity and isotropy" means that various n-point auto-correlation functions of structure tracers within a "neighbourhood" of a Gpc or so should give identical results to within observational uncertainties. This is what is observed, but it does not constrain global homogeneity and isotropy. So it is unclear why a multiply connected 3-manifold with an FLRW metric is in any way "limited" or "ill-motivated". * We are only aware of one paper so far showing that global topology could have an effect (albeit small) on the FLRW metric through the addition of an additional acceleration effect (Roukema et al. 2007). Best regards, Boud Roukema, ... References o "size of the Universe": + Luminet, J.-P., Roukema, B. F., 1999, Topology of the Universe: Theory and Observation, NATO ASIC Proc. 541: Theoretical and Observational Cosmology , 117, http://cdsads.u-strasbg.fr/abs/1999toc..conf..117L o WMAP: PDS and 3-torus models (and other spherical models) vs K=0 infinite model: + Aurich, R., Lustig, S., Steiner, F., 2005, CMB anisotropy of spherical spaces, Classical and Quantum Gravity, 22, 3443, http://cdsads.u-strasbg.fr/abs/2005CQGra..22.3443A + Aurich, R., Lustig, S., Steiner, F., 2005, CMB anisotropy of the PoincarĂŠ dodecahedron, Classical and Quantum Gravity, 22, 2061, http://cdsads.u-strasbg.fr/abs/2005CQGra..22.2061A + Aurich, R., Lustig, S., Steiner, F., 2006, The circles-in-the-sky signature for three spherical universes, Monthly Notices of the Royal Astronomical Society, 369, 240, http://cdsads.u-strasbg.fr/abs/2006MNRAS.369..240A + Caillerie, S., LachiĂ¨ze-Rey, M., Luminet, J.-P., Lehoucq, R., Riazuelo, A., Weeks, J., 2007, A new analysis of the PoincarĂŠ dodecahedral space model, Astronomy and Astrophysics, 476, 691, http://cdsads.u-strasbg.fr/abs/2007A%26A...476..691C + Gundermann, J., 2005, Predicting the CMB power spectrum for binary polyhedral spaces, ArXiv Astrophysics e-prints, arXiv:astro-ph/0503014, http://cdsads.u-strasbg.fr/abs/2005astro.ph..3014G + Key, J. S., Cornish, N. J., Spergel, D. N., Starkman, G. D., 2007, Extending the WMAP bound on the size of the Universe, Physical Review D, 75, 084034, http://cdsads.u-strasbg.fr/abs/2007PhRvD..75h4034K + Lew, B., Roukema, B., 2008, A test of the PoincarĂŠ dodecahedral space topology hypothesis with the WMAP CMB data, Astronomy and Astrophysics, 482, 747, http://cdsads.u-strasbg.fr/abs/2008A%26A...482..747L + Luminet, J.-P., Weeks, J. R., Riazuelo, A., Lehoucq, R., Uzan, J.-P., 2003, Dodecahedral space topology as an explanation for weak wide-angle temperature correlations in the cosmic microwave background, Nature, 425, 593, http://cdsads.u-strasbg.fr/abs/2003Natur.425..593L + Niarchou, A., Jaffe, A., 2007, Imprints of Spherical Nontrivial Topologies on the Cosmic Microwave Background, Physical Review Letters, 99, 081302, http://cdsads.u-strasbg.fr/abs/2007PhRvL..99h1302N + Riazuelo, A., Weeks, J., Uzan, J.-P., Lehoucq, R., Luminet, J.-P., 2004, Cosmic microwave background anisotropies in multiconnected flat spaces, Physical Review D, 69, 103518, http://cdsads.u-strasbg.fr/abs/2004PhRvD..69j3518R + Roukema, B. F., Bulinski, Z., Szaniewska, A., Gaudin, N. E., 2008, The optimal phase of the generalised Poincare dodecahedral space hypothesis implied by the spatial cross-correlation function of the WMAP sky maps, Astronomy and Astrophysics, in press, arXiv:0801.0006, http://cdsads.u-strasbg.fr/abs/2008arXiv0801.0006R + Roukema, B. F., Lew, B., Cechowska, M., Marecki, A., Bajtlik, S., 2004, A hint of PoincarĂŠ dodecahedral topology in the WMAP first year sky map, Astronomy and Astrophysics, 423, 821, http://cdsads.u-strasbg.fr/abs/2004A%26A...423..821R o effect of global topology on the metric: + Roukema, B. F., Bajtlik, S., Biesiada, M., Szaniewska, A., Jurkiewicz, H., 2007, A weak acceleration effect due to residual gravity in a multiply connected universe, Astronomy and Astrophysics, 463, 861, http://cdsads.u-strasbg.fr/abs/2007A%26A...463..861R ----------------------------------------------------------------------

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Benasque meeting, anyone?
by Boud Roukema 04 Apr '08

04 Apr '08

hi everyone on the cos-top mailing list, There are at least two cosmology workshop-type meetings this northern summer at which cosmic topology is likely to be discussed: * Pune, Maharashtra (India, monsoon time but the monsoon in Pune is mild (not strong) ;) "Cosmology with CMB and LSS" 21 July - 31 Aug (full = 6 weeks = 3 * 2-week sessions, but can stay for a shorter time) http://icts.tifr.res.in/sites/cmb/index * Benasque, Pyrenees (mountains on spanish/french border) "Modern Cosmology" 27 July - 14 August 2008 http://benasque.ecm.ub.es/2008cosmology/2008cosmology.htm http://cosmocoffee.info/viewtopic.php?t=1093 Tarun Souradeep is one of the main organisers of the Pune meeting and cosmic topology is listed for the third two-week part of the full session; Glenn Starkman and Dominik Schwarz are listed as participants for the Benasque meeting. i'm thinking of going to the Benasque meeting (leaving a day or two before the end). Is anyone thinking of going to one of these meetings? i can't imagine that i'll be over two weeks together with Glenn and Dominik without having any useful discussions on cosmic topology, and it would probably make sense that more of us are together than less. Both the Pune and Benasque meetings sound like they'll be as much workshops where real work will get done rather than just standard conference presentations. The deadlines for both are 15 April. cheers boud

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Happy New +36 degree Year!
by Boud Roukema 08 Jan '08

08 Jan '08

hi everyone, i guess maybe only Marcelo on this list is feeling +36 degrees or so Celsius right now, but PDS +36 degrees seems now to at least qualitatively agree with Ralf, Frank and Sven's work and the Caillerie et al. paper. http://arXiv.org/abs/0801.0006 In other words, we managed to kill off our previous "hint" candidate, but another one better agreeing with other people's work has turned up. Are we converging? Enjoy :). Best wishes for the New Year boud

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