Biblioteca Digital

This article considers teacher knowledge in managing mathematically critical situations and the role of what can be termed a mathematical summary in the analysis of a teaching episode, viewed from the perspective of Mathematical Knowledge for Teaching (MKT). The analysis is based on an episode of content review, from a perspective which aims to understand the teacher???s logic rather than merely identify gaps in their knowledge. We discuss the importance of approaching mathematically critical situations in order to contribute to eradicating mathematical innumeracy (statistics) and to promote a kind of practice which is ???mathematically demanding??? as well as ???pedagogically exciting???.; Este art??culo considera el conocimiento del profesor al gestionar situaciones matem??ticamente cr??ticas y el papel de lo que puede denominarse un resumen matem??tico en el an??lisis de un episodio de ense??anza, visto desde la perspectiva del conocimiento matem??tico para la ense??anza. El an??lisis se basa en un episodio de revisi??n del contenido, desde una perspectiva que trata de comprender la l??gica del profesor en vez de simplemente identificar lagunas en su conocimiento. Discutimos la importancia de abordar las situaciones matem??ticamente cr??ticas con el fin de contribuir a erradicar la incompetencia en matem??ticas (estad??stica) y promover un tipo de pr??ctica que sea ???matem??ticamente exigente??? as?? como ???pedag??gicamente interesante???.

Face to critical contingence situations, the System Operator can require wind farms output reductions. The zonal Delegated Dispatches can act as interface between the System Operator and the producers, allowing a faster and accurate answer. Three probable approaches are mathematically formulated and analyzed in the paper, separately considering the controllability and the possibility of disconnecting the wind farms. The methods are testedand compared by using a realistic test network, extracted from the Spanish national network.

Nos últimos anos o conhecimento do professor tem vindo a ser reconhecido como um dos aspetos nucleares no, e para o, desenvolvimento do conhecimento matemático dos alunos. Atendendo a essa centralidade, a formação deverá focar-se onde é, efetivamente, necessária, de modo a potenciar um incremento do conhecimento dos alunos, pelo conhecimento (e práticas) dos professores. Sendo os números racionais um dos tópicos problemáticos para os alunos, é fundamental identificar quais as situações matematicamente (mais) críticas para os professores de modo que, pela formação facultada, possam deixar de o ser. Neste artigo, tendo por foco o conhecimento matemático do professor e as suas especificidades, discutimos alguns aspetos desse conhecimento de futuros professores sobre números racionais, em concreto o sentido de número racional, identificando as suas componentes mais problemáticas e equacionando alguns dos porquês em que se sustentam. Terminamos com algumas considerações sobre implicações para a formação de professores e responsabilidade dos seus formadores.; Abstract: In recent years, teachers’ knowledge has come to be recognized as one of the core aspects in and for the development of students’ mathematical knowledge. This being the case...

This paper reviews recent results on hybrid inverse problems, which are also called coupled-physics inverse problems of multi-wave inverse problems. Inverse problems tend to be most useful in, e.g., medical and geophysical imaging, when they combine high contrast with high resolution. In some settings, a single modality displays either high contrast or high resolution but not both. In favorable situations, physical effects couple one modality with high contrast with another modality with high resolution. The mathematical analysis of such couplings forms the class of hybrid inverse problems. Hybrid inverse problems typically involve two steps. In a first step, a well-posed problem involving the high-resolution low-contrast modality is solved from knowledge of boundary measurements. In a second step, a quantitative reconstruction of the parameters of interest is performed from knowledge of the point-wise, internal, functionals of the parameters reconstructed during the first step. This paper reviews mathematical techniques that have been developed in recent years to address the second step. Mathematically, many hybrid inverse problems find interpretations in terms of linear and nonlinear (systems of) equations. In the analysis of such equations...

We consider a polymer, with monomer locations modeled by the trajectory of a Markov chain, in the presence of a potential that interacts with the polymer when it visits a particular site 0. Disorder is introduced by, for example, having the interaction vary from one monomer to another, as a constant $u$ plus i.i.d. mean-0 randomness. There is a critical value of $u$ above which the polymer is pinned, placing a positive fraction of its monomers at 0 with high probability. This critical point may differ for the quenched, annealed and deterministic cases. We show that self-averaging occurs, meaning that the quenched free energy and critical point are nonrandom, off a null set. We evaluate the critical point for a deterministic interaction ($u$ without added randomness) and establish our main result that the critical point in the quenched case is strictly smaller. We show that, for every fixed $u\in\mathbb{R}$, pinning occurs at sufficiently low temperatures. If the excursion length distribution has polynomial tails and the interaction does not have a finite exponential moment, then pinning occurs for all $u\in\mathbb{R}$ at arbitrary temperature. Our results apply to other mathematically similar situations as well, such as a directed polymer that interacts with a random potential located in a one-dimensional defect...

Critical String Theory is by definition an $S$-matrix theory. In this sense, (quantum) gravity situations where a unitary $S$-matrix may not be a well-defined concept, as a consequence of the existence of macroscopic (global) or microscopic (local) gravitational fluctuations with event horizons, present a challenge to string theory. In this article, we take some modest steps in suggesting alternative treatments of such cases via non-critical (Liouville) strings,which do not have a well-defined S matrix, but for which a superscattering \$ matrix is mathematically consistent. After a brief review of the underlying mathematical formalism, we consider a specific stringy model of induced non-criticality, with dynamical formation of horizons, associated with the recoil of a D-particle defect, embedded in our four-dimensional space time, during its scattering with a (macroscopic) number of closed string states. We study in detail the associated spacetime distortion in the neighbourhood of the defect, which has the form of a finite-radius curved `bubble', matched with a Minkowskian space-time in the exterior. As a consequence of the non-criticality of the underlying sigma-model, the space time is unstable, and has non-trivial stochastic properties: thermal properties due to its ``Rindler accelerating nature''...