Abstracts of theses and related literature indicating current trends in arithmetic for the academically talented elementary school child written between 1957 and 1961

Thesis (Ed.M.)--Boston Universit

Evolution of the Globular Cluster System in a Triaxial Galaxy

Dynamical friction and tidal disruption are effective mechanisms of evolution of globular cluster systems, especially in non-axysimmetric galaxies with a central compact nucleus. With a semi-analytical approach based on the knowledge of the dependence of the dynamical friction and tidal disruption effects on the relevant parameters, we are able to follow the time evolution of the globular cluster system in a model of a triaxial galaxy and give its observable properties to compare with observational data. An important result is that the flatter distribution of the globular cluster system relatively to that of the stellar bulge, as observed in many galaxies, can be explained by the evolution of the globular cluster system, starting from the same density profile.Comment: 9 pages, including 7 eps figures; latex file using standard MNRAS style file. Paper submitted to MNRA

Globular cluster system erosion and nucleus formation in elliptical galaxies

The radial distribution of globular clusters in galaxies is always less peaked to the centre than the halo stars'. Extending previous work to a sample of HST globular cluster systems in ellipticals, we evaluate the number of clusters lost to the galactic centre as the integrals of the difference between the observed globular cluster system distribution and the underlying halo light profile. It results that the initial populations of globular clusters were from 25% to 50% richer than now. This significant number of missing globular clusters supports the hypothesis that a large quantity of globular cluster mass in form of globular clusters decayed and destroyed has been lost to the galactic centres, where plausibly contributed to formation and feeding of a mas sive object therein. It is relevant noting that the observed correlation between the core radius of the globular cluster system and the parent galaxy luminosity can be interpreted as a result of evolution.Comment: Latex file + 2 figures as postscript files; it needs standard MNRAS style file and epsf macro for figures. Paper submitted to MNRA

Merging of globular clusters within inner galactic regions. II. The Nuclear Star Cluster formation

In this paper we present the results of two detailed N-body simulations of the interaction of a sample of four massive globular clusters in the inner region of a triaxial galaxy. A full merging of the clusters takes place, leading to a slowly evolving cluster which is quite similar to observed Nuclear Clusters. Actually, both the density and the velocity dispersion profiles match qualitatively, and quantitatively after scaling, with observed features of many nucleated galaxies. In the case of dense initial clusters, the merger remnant shows a density profile more concentrated than that of the progenitors, with a central density higher than the sum of the central progenitors central densities. These findings support the idea that a massive Nuclear Cluster may have formed in early phases of the mother galaxy evolution and lead to the formation of a nucleus, which, in many galaxies, has indeed a luminosity profile similar to that of an extended King model. A correlation with galactic nuclear activity is suggested.Comment: 18 pages, 10 figures, 3 tables. Submitted to ApJ, main journa

NBSymple, a double parallel, symplectic N-body code running on Graphic Processing Units

We present and discuss the characteristics and performances, both in term of computational speed and precision, of a numerical code which numerically integrates the equation of motions of N 'particles' interacting via Newtonian gravitation and move in an external galactic smooth field. The force evaluation on every particle is done by mean of direct summation of the contribution of all the other system's particle, avoiding truncation error. The time integration is done with second-order and sixth-order symplectic schemes. The code, NBSymple, has been parallelized twice, by mean of the Computer Unified Device Architecture to make the all-pair force evaluation as fast as possible on high-performance Graphic Processing Units NVIDIA TESLA C 1060, while the O(N) computations are distributed on various CPUs by mean of OpenMP Application Program. The code works both in single precision floating point arithmetics or in double precision. The use of single precision allows the use at best of the GPU performances but, of course, limits the precision of simulation in some critical situations. We find a good compromise in using a software reconstruction of double precision for those variables that are most critical for the overall precision of the code. The code is available on the web site astrowww.phys.uniroma1.it/dolcetta/nbsymple.htmlComment: Paper composed by 29 pages, including 9 figures. Submitted to New Astronomy

High performance astrophysics computing

The application of high end computing to astrophysical problems, mainly in the galactic environment, is under development since many years at the Dep. of Physics of Sapienza Univ. of Roma. The main scientific topic is the physics of self gravitating systems, whose specific subtopics are: i) celestial mechanics and interplanetary probe transfers in the solar system; ii) dynamics of globular clusters and of globular cluster systems in their parent galaxies; iii) nuclear clusters formation and evolution; iv) massive black hole formation and evolution; v) young star cluster early evolution. In this poster we describe the software and hardware computational resources available in our group and how we are developing both software and hardware to reach the scientific aims above itemized.Comment: 2 pages paper presented at the Conference "Advances in Computational Astrophysics: methods, tools and outcomes", to be published in the ASP Conference Series, 2012, vol. 453, R. Capuzzo-Dolcetta, M. Limongi and A. Tornambe' ed

Gravitational clustering in N-body simulations

In this talk we discuss some of the main theoretical problems in the understanding of the statistical properties of gravity. By means of N-body simulations we approach the problem of understanding the r\^ole of gravity in the clustering of a finite set of N-interacting particles which samples a portion of an infinite system. Through the use of the conditional average density, we study the evolution of the clustering for the system putting in evidence some interesting and not yet understood features of the process.Comment: 5 pages, 1 figur