ABOUT Pavel Kroupa

Avatar of Pavel Kroupa

I am a Czech-born Australian citizen teaching and researching at the University of Bonn on dynamics and stellar populations. After studying physics at The University of Western Australia, Perth, I obtained my PhD from Cambridge University, UK, as an Isaac Newton Scholar at Trinity College. After spending eight years in Heidelberg I habilitated at the University of Kiel, Germany. I then took up a Heisenberg Fellowship and later accepted the position as a professor at Bonn University in 2004. I was awarded a Leverhulme Trust Visiting Professorship (2007, Sheffield, UK) and a Swinburne Visiting Professorship (2007, Melbourne, Australia). My web-page: http://www.astro.uni-bonn.de/~pavel/
Pure innovative science can only truly thrive in non-hierarchical societies in which competition for resources is not extreme. Therefore I see the need for the German academic system to modernise (away from its hierarchies) and warn of academic systems that are based on an extreme competition for resources (USA), as these stifle the experimentation with new ideas.

 

Pavel Kroupa: All Posts

 
 

The Planck Results on the Cosmic Microwave Background

Posted 22 April 2013 by Pavel Kroupa

Guest contribution by Behnam Javanmardi Prologue by Pavel Kroupa: The much awaited Planck results on the CMB have been published recently. The results are consistent with those arrived at by using Wilkinson Microwave Anisotropy Probe (WMAP) measurements. This agreement is excellent news, because it means that the two missions are consistent and thus the Planck data enhance our confidence in what we know about the CMB. But, what do the results mean in terms of our physical understanding of the... Read more

A filament of dark matter between two clusters of galaxies: dark matter detected

Posted 5 July 2012 by Pavel Kroupa

We briefly comment on the paper by Dietrich, Werner, Clowe et al. on "A filament of dark matter between two clusters of galaxies " which is now in press with Nature.  The media have it that this may be a direct detection of dark matter.  The abstract of this paper reads "It is a firm prediction of the concordance Cold Dark Matter (CDM) cosmological model that galaxy clusters live at the intersection of large-scale structure filaments. The thread-like structure of... Read more

Question D: What about the Bullet cluster? And what about the Train-Wreck cluster Abell 520?

Posted 15 April 2012 by Pavel Kroupa

Summary: One result is very definite by now: neither the Bullet nor the Train Wreck clusters support (nor do they prove) the existence of cold or warm dark matter. And, they certainly do not disprove MOND. Quite on the contrary, according to current knowledge, they falsify the concordance cosmological (or LCDM) model. The Bullet cluster consists of two clusters of galaxies that have penetrated each other leaving behind a slab of gas while the now seperating clusters retain matter as... Read more

Question C.III: Fundamental theoretical problems

Posted 31 March 2012 by Pavel Kroupa

Rather than being posted "soon after" II: MOND works far too well ! (published on the 21.03.2011), a delay caused by internal university issues arose. We are back though, for the time being, with the originally advertised "Question C.III: Fundamental theoretical problems" (this contribution). To re-iterate: what is the purpose of this series on SciLogs? We are aiming to document, within the time we have for such matters, the already noticeable paradigm shift away from a dark-matter dominated Einsteinian inflationary... Read more

Question C.II: MOND works far too well !

Posted 21 March 2011 by Pavel Kroupa

Summary: First try: Using only Solar System constraints, Newton and then Einstein developed the universal theory of gravitation. This Theory of General Relativity (GR) is then applied to model the universe. In order for it to fit the observational cosmological constraints, inflation, dark matter and dark energy need to be postulated to exist. Tests on scales of 10Mpc and less show this top-down modelling to fail despite major fine-tuning attempts.  Second try: Using Solar System and galactic constraints Milgrom and... Read more

Question C.I: What are the three best reasons for the failure of the LCDM model? I: Incompatibility with observations

Posted 8 March 2011 by Pavel Kroupa

Summary: The development of the concordance cosmological model (CCM) over the past 40 years is based on the addition of at least three unknown ("dark") physical phenomena (inflation, cold dark matter, dark energy), in an attempt to make Einstein's field equation account for the distribution of matter on galactic and larger scales. None of these are understood nor experimentaly verified today. While these may constitute true discoveries of new physics, much as in the spirit of the past when for example... Read more

Question B2: What is a galaxy? (Addendum on the relaxation time)

Posted 23 January 2011 by Pavel Kroupa

Background: As introduced in the previous contribution to The Dark Matter Crisis, Question A: Galaxies do not work in LCDM, sociology and majority views, PK was recently contacted by a few people, and here are excerpts from some of the questions asked and the replies. These help to illustrate some of the issues at hand. The questions are A) So the LCDM model fails on scales smaller than about 8 Mpc? B1) What is a galaxy? B2) What is a galaxy?... Read more

Question B1: What is a galaxy?

Posted 19 January 2011 by Pavel Kroupa

Question B1: "What is a galaxy?  - vote here!"   Answer: The astronomical object we commonly call a "galaxy" has no formal definition yet. This issue is now raised to a more formal problem by Forbes & Kroupa (2011)(F&K). Here is the associated press release. Science and New Scientist also report on this question. Your vote is of interest: Being motivated by the vote at the General Assembly of the International Astronomical Union in Prague in the year 2006 on... Read more

Question A: Galaxies do not work in LCDM, sociology and majority views

Posted 17 January 2011 by Pavel Kroupa

Independently of any dark-matter detections or the success or failure of dark-matter searches (it is notable that the originally favoured dark matter particles have long ago been excluded through direct searches, as summarised by Prof. Stacy McGaugh), it is a well known problem that galaxies cannot be reproduced in the standard cosmological (i.e. the LCDM) scenario. In the LCDM model, the mass of the universe consists to about 4 % out of normal (baryonic) matter which we observe, while 96%... Read more

Another reaction to the Dark Matter Debate

Posted 8 December 2010 by Pavel Kroupa

During the past months there was quite some activity in the German media on the issue of cosmology and the existence of dark matter. Starting with our German paper "The standard cosmological model being tested" (German: Das kosmologische Standardmodell auf dem Pruefstand"), which appeared in the August issue of  Spektrum der Wissenschaft,  some of the leading experts are beginning to re-position themselves, it seems. In a major German article about himself "Perhaps we are seeking a phantom" (in German: "Vielleicht... Read more