Galactic consequences of clustered star formation

If all stars form in clusters and both the stars and the clusters follow a power law distribution which favours the creation of low mass objects, then the numerous low mass clusters will be deficient in high mass stars. Therefore, the mass function of stars, integrated over the whole galaxy (the Integrated Galactic Initial Mass Function, IGIMF) will be steeper at the high mass end than the underlying IMF of the stars. We show how the steepness of the IGIMF depends on the sampling method and on the assumptions made for the star cluster mass function. We also investigate the O-star content, integrated photometry and chemical enrichment of galaxies that result from several IGIMFs, as compared to more standard IMFs.Comment: 4 pages, 2 figures, to appear in online version of Proceedings of IAU S266, a two page version will appear in the Proceedings of IAU S26

Staggered Fermion Actions with Improved Rotational Invariance

We introduce a class of improved actions for staggered fermions which to O(p^4) and O(p^6), respectively, lead to rotationally invariant propagators. We discuss the resulting reduction of flavour symmetry breaking in the meson spectrum and comment on the improvement in the calculation of thermodynamic observables.Comment: 3 pages and 4 figures, Contribution to Lattice 97 (Poster Session), late

Vielfalt wahrnehmen durch diagnostische Interviews 1 - Interview und neuseeländisches Lernentwicklungsmodell Numeracy

„Significant changes in teacher attitudes and beliefs happen when they use new practices effectively and see changes in student learning.” (Guskey, 1986, S. 7). Dieser Satz steht für die Grundidee des Numeracy Professional Development Projects (NDP), mit dem Neuseeland auf das unbefriedigende Abschneiden bei der TIMS-Studie 1995 reagiert hat. Konzeptelemente sowie ins Deutsche übertragene Projektmaterialien werden – u.a. von der Autorengruppe – in deutschen Schulen und in der Lehrerbildung erprobt. Dieser Beitrag gibt Informationen zu zentralen Elementen von NDP und berichtet über erste Erfahrungen aus der Arbeit mit Fachberatungen in Rheinland-Pfalz. Im Beitrag „Vielfalt wahrnehmen ... 2“ wird ein Kooperationsprojekt aus Bremen (Schule, Landesinstitut, Universität)vorgestell

Vielfalt wahrnehmen durch diagnostische Interviews 2

Zentrales Anliegen des neuseeländischen Numeracy Development Project (NDP) ist es, Schülerleistungen durch die Professionalisierung von Lehrkräften zu verbessern. Professionalität wird dabei sowohl in fachlicher als auch in diagnostischer Hinsicht verstanden: „The effective teacher of mathematics and statistics has a thorough and deep understanding of the subject matter to be taught, how students are likely to learn it, and the difficulties and misunderstandings they are likely to encounter” (Ministry of Education 2008a, S. i). In einem Kooperationsprojekt der Gesamtschule Bremen-Mitte (GSM), der Universität Bremen und des Landesinstituts für Schule in Bremen sind das diagnostische Interview und einige Lerneinheiten des NDP überarbeitet und durch Studierende in der Lehramtsausbildung erprobt worden. Erfahrungen dieses Projekts werden im Folgenden vorgestellt. Mit dem Fokus auf der Frage: „Was passiert eigentlich nach den Interviews?“ schließt dieser Beitrag direkt an den Beitrag „Vielfalt wahrnehmen durch diagnostische Interviews 1“ von Katzenbach et al. (in diesem Band) an

The role of E+A and post-starburst galaxies – II. Spectral energy distributions and comparison with observations

‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.15036.xIn a previous paper, we have shown that the classical definition of E+A galaxies excludes a significant number of post-starburst galaxies. We suggested that analysing broad-band spectral energy distributions (SEDs) is a more comprehensive method to select and distinguish post-starburst galaxies than the classical definition of measuring equivalent widths of (Hδ) and [O ii] lines. In this paper, we will carefully investigate this new method and evaluate it by comparing our model grid of post-starburst galaxies to observed E+A galaxies from the MORPHS catalogue. In the first part, we investigate the UV-optical-NIR (near-infrared) SEDs of a large variety in terms of progenitor galaxies, burst strengths and time-scales of post-starburst models and compare them to undisturbed spiral, S0 and E galaxies as well as to galaxies in their starburst phase. In the second part, we compare our post-starburst models with the observed E+A galaxies in terms of Lick indices, luminosities and colours. We then use the new method of comparing the model SEDs with SEDs of the observed E+A galaxies. We find that the post-starburst models can be distinguished from undisturbed spiral, S0 and E galaxies and galaxies in their starburst phase on the basis of their SEDs. It is even possible to distinguish most of the different post-starbursts by their SEDs. From the comparison with observations, we find that all observed E+A galaxies from the MORPHS catalogue can be matched by our models. However, only models with short decline time-scales for the star formation rate are possible scenarios for the observed E+A galaxies in agreement with our results from the first paper.Peer reviewe

Dense subsets of products of finite trees

We prove a "uniform" version of the finite density Halpern-L\"{a}uchli Theorem. Specifically, we say that a tree $T$ is homogeneous if it is uniquely rooted and there is an integer $b\geq 2$, called the branching number of $T$, such that every $t\in T$ has exactly $b$ immediate successors. We show the following. For every integer $d\geq 1$, every $b_1,...,b_d\in\mathbb{N}$ with $b_i\geq 2$ for all $i\in\{1,...,d\}$, every integer k\meg 1 and every real $0<\epsilon\leq 1$ there exists an integer $N$ with the following property. If $(T_1,...,T_d)$ are homogeneous trees such that the branching number of $T_i$ is $b_i$ for all $i\in\{1,...,d\}$, $L$ is a finite subset of $\mathbb{N}$ of cardinality at least $N$ and $D$ is a subset of the level product of $(T_1,...,T_d)$ satisfying $$|D\cap \big(T_1(n)\times ...\times T_d(n)\big)| \geq \epsilon |T_1(n)\times ...\times T_d(n)|$$ for every $n\in L$, then there exist strong subtrees $(S_1,...,S_d)$ of $(T_1,...,T_d)$ of height $k$ and with common level set such that the level product of $(S_1,...,S_d)$ is contained in $D$. The least integer $N$ with this property will be denoted by $UDHL(b_1,...,b_d|k,\epsilon)$. The main point is that the result is independent of the position of the finite set $L$. The proof is based on a density increment strategy and gives explicit upper bounds for the numbers $UDHL(b_1,...,b_d|k,\epsilon)$.Comment: 36 pages, no figures; International Mathematics Research Notices, to appea