Stability and the Gauge Problem in Non-Perturbative Cosmology

In this paper, we describe the first steps towards fully non-perturbative cosmology. We explain why the conventional methods used by cosmologists based on the ADM formulation are generally inadequate for this purpose and why it is advantageous instead to adapt the harmonic formulation pioneered and utilized in mathematical and numerical relativity. Here we focus on using this approach to evaluating the linear mode stability in homogeneous and nearly homogeneous backgrounds and devising a valid scheme and diagnostics for numerical computation. We also briefly touch on the relevance of these methods for extracting cosmological observables from non-perturbative simulations.Comment: 43 page

A topological approach for segmenting human body shape

Segmentation of a 3D human body, is a very challenging problem in applications exploiting human scan data. To tackle this problem, the paper proposes a topological approach based on the discrete Reeb graph (DRG) which is an extension of the classical Reeb graph to handle unorganized clouds of 3D points. The essence of the approach concerns detecting critical nodes in the DRG, thereby permitting the extraction of branches that represent parts of the body. Because the human body shape representation is built upon global topological features that are preserved so long as the whole structure of the human body does not change, our approach is quite robust against noise, holes, irregular sampling, frame change and posture variation. Experimental results performed on real scan data demonstrate the validity of our method

The prevalent theory of construction is a hindrance for innovation

It is argued that construction innovation is significantly hindered by the prevalent theory of construction, which is implicit and deficient. There are three main mechanisms through which this hindrance is being caused. Firstly, because production theories in general, as well as construction theories specifically, have been implicit, it has not been possible to transfer such radical managerial innovation as mass production or lean production from manufacturing to construction. Direct application of these production templates in construction has been limited due to different context in construction in correspondence to manufacturing. On the other hand, without explicit theories, it has not been possible to access core ideas of concepts and methods of these templates, and to recreate them in construction environment. In consequence, theory and practice of construction has not progressed as in manufacturing. Secondly, it is argued that the underlying, even if implicit, theoretical model of construction is the transformation model of production. There are two first principles in the transformation model. First, the total transformation can be achieved only by realising all parts of it. Thus, we decompose the total transformation into parts, finally into tasks, ensure that all inputs are available and assign these tasks to operatives or workstations. Second, minimising the cost of each task, i.e. each decomposed transformation, minimises the cost of production. It is argued that these principles, in which uncertainty and time are abstracted away, are counterproductive, and lead to myopic control and inflated variability. Practical examples show that these deficiencies and related practical constraints hinder the top-down implementation of innovations. Thirdly, empirical research shows that also bottom-up innovation - systematic learning and problem solving - is hindered by this deficient theory. Thus, the advancement of construction innovation requires that a new, explicit and valid theory of construction is created, and business models and control methods based on it are developed