REPORT ON THE TMR MEETING ON NUMERICAL SIMULATIONS DURHAM FRIDAY MAY/2 -- SATURDAY MAY/3 The meeting had two main purposes: (1) to familiarize people with work being done on simulations across the network institutions, as a prelude to exploring possible areas of common interest and potential collaborations; (2) to make progress on existing collaborators. To achieve these goals, we had a mixture of short presentations and informal discussions, allowing enough time for small group interactions. The list of oral presentations, a (very incomplete) list of the topics discussed at the meeting and a list of participants follows: I. TALKS FRIDAY MORNING 10:00 to 12:30 Short talks (about 20 minutes each) Cole: The Formation Paths of Dark Matter Haloes: Analytic Merger History Trees versus N-body Simulations Tormen: The dynamics of satellites in galaxy clusters Ghigna: Dark matter substructure in clusters SPH: Governato: The history of star formation in spirals Pearce: The reliability of SPH simulations Carraro: Elliptical Galaxies: formation and evolution FRIDAY AFTERNOON 14:00 -- 16:00 Discussion Topics N-bodies Common Software Mock Catalogues FRIDAY AFTERNOON 16:00 -- 18:00 Discussion Small group discussions SATURDAY MORNING 10:00 to 12:00 Short talks (about 20 minutes each) N-body: larger scales Jenkins: The large-scale distribution of dark matter Colberg: Semianalytic galaxy formation in high resolution simulations Springel: Simulations of merging disk galaxies with GRAPE SATURDAY MORNING/AFTERNOON 12:00 to 13:00 and 14:00 to 18:00 DISCUSSION AND INTERACTION. ---------------------------------------------------------------------------- II. DISCUSSIONS: Notes 1) Discussion on collisionless systems (chairman S. White) a) Is the NFW formula for halo profiles valid? Moore, Ghigna and Governato are extensively testing it with much higher resolution than previously available. b) There is general agreement between the results produced by different codes once resolution is correctly taken into account. c) The pros and cons of starting from a grid or a "glass" for the initial particle distribution were debated. The starting redshift of a simulation is still under debate though. d) Both Munich and the Durham groups are testing the validity of the Press and Schechter theory for the growth of cosmological structures. 2) Discussion on hydrodynamical simulations (chairman G. Evrard) a) Frenk presented preliminary results from a comparison between several codes. A cluster simulation (not including cooling effects) has been carried out by 12 groups around the world. There is good agreement between the results produced with different codes. Governato presented a smaller test (a galaxy forming in a cosmological context, including cooling) between the TREESPH developed by Hernquist Katz and Weinberg and the one developed by Navarro and then modified by Gelato. Again good agreement between the two codes is found. b) There is general agreement that the number of neighbors used in SPH simulations should be no less than 32 and possibly higher. Unwanted numerical effects due to poor treatment of pressure gradients were pointed out by several participants. c) The inclusion of star formation in N-body/gasdynamic simulations is still an open problem. Several groups are working on this. Hopefully a set of tests between different codes (both numerical and semianalytical) will be set up shortly. 3) Discussion on Large Scale Structure simulations (chairman C. Frenk) New projects were presented and the different roles of semianalitical models and simulations were debated. Several groups are including merger trees obtained from numerical simulations of big cosmological volumes into semianalytical models of galaxy formation. ------------------------------------------------------------------- III. LIST OF PARTICIPANTS Baugh Branchini Carraro Colberg Cole Evrard Frenk Ghigna Governato Jenkins Kay MacFarland Ninin Pearce Springel Tormen White