Computational models in systemic design

Some of the most significant challenges of sustainability can be traced back to the complexity of social and ecological phenomena and the difficulty to connect these with design decisions made at the level of products and business models. Such complex systems are especially difficult to assess and influence as they do not lend themselves to simple causality relations and prediction (Boulton et al, 2015; Jones et al. 2014). A few schools of thought in design are explicitly embracing complexity, such as systemic design (Jones et al. 2014) and transition design (Irwin 2018). Building upon insights from complexity science, they encompass a wide range of design methodologies, such as giga- mapping (Sevaldson 2011), system maps (Irwin 2018), or co-creation (e.g. Sanders and Stappers 2008). The vast majority of methods described in systemic and transition design literature are qualitative in nature. This is in stark contrast with the methods used in complexity science – or complex systems science. This interdisciplinary field of science has been built predominantly upon the use of quantitative, computational models, a number of which have been applied to social phenomena, e.g. Network theory enables the modelling of a set of elements interacting with each other, such as people in a social group, employees in a company, or companies in a supply chain (Newman 2010). This type of approach has delivered numerous insights, e.g. on the structure of social networks (Scott, 2017), the organisational needs of engineering projects (Sosa et al, 2004), and the robustness of the internet and the web (Réka et al. 2000), as well as to sustainability questions (e.g. Bodin and Tengö 2012) System dynamics can be used to model a system of interconnected stocks and flows and their evolution over time. This method has been used to assess scenarios of global ecological challenges (Meadows et al. 1972), as well as to inform business model design (Cosenz 2017), conservation initiatives (Johnson et al. 2012) and pathways towards sustainable development (Hjorth and Bagheri 2006). Agent-based models provide a way to simulate the dynamics of social systems by placing explicit emphasis on how they emerge from the behaviours of individuals (the ‘agents’) (Van Dam et al. 2012). Their applications include the dynamics of segregation (Schelling 1978, Wilensky 1997), policy analysis (Lempert 2002, Nikolic and Dijkema 2010), and industrial ecology (Axtell et al. 2001). Systems of differential equations can be used to represent certain phenomena at aggregated levels, e.g. to give a mathematical representation of the response of societies to societal problems (Scheffer et al. 2003). Such computational models could provide key insights for design for complex systems. Table 1 lists examples of computational models from literature that can be easily connected to a design activity. If computational models have such a potential for design, why haven’t such methods been promoted in the literature on systemic and transition design? We explore the potential causes of this reluctance through three key questions, and deduct lessons for the development of computational methods in design for complex systems, and therefore design for sustainability. 1. Can humans be modelled? It is fair to ask whether mathematics can usefully describe social phenomena. Supporting this concern, the field of economics has in the past heavily underplayed the complexity of human behaviours, using drastically simplified assumptions to enable mathematical description (Arthur 1999). The response to this concern is 2-fold. First, models of human behaviours have greatly improved over the past decades, e.g. through behavioural economics. These improved hypotheses however still need to be made explicit in research, as they often reflect certain values and worldviews. Second, today’s online tools have given rise to unprecedented data about human behaviours, through the field of computational social science (Conte et al. 2012). The applications to design are worth considering (Lettieri 2016). Recent research (Moat et al. 2014) demonstrates the growing ability of modern techniques to predict social behaviors and, if this weren’t enough warning, recent news headlines highlight the implied risk that this be used to manipulate people. The ethical considerations of modelling humans should thus always be considered carefully. 2. Are design and modelling practices compatible? Developing a computational model requires strong critical thinking and rigour. It can thus be more conducive to removing ideas than to creating new ones. Could it stifle the generative, creative thinking that is central to design? Two approaches to avoiding this shortcoming are to carefully think of the phase in which to integrate the use of a model and to leverage intuition and ideas from the designers and stakeholders as inputs into the model. Data analysis and modelling can be time consuming and require specialised skills, so they can be cost intensive. Budget or planning may therefore motivate their exclusion. What may address this issue is the development of interfaces and platforms enabling the adaptation of existing models to new situations. As an illustration of such solutions, the platform Kumu offers a user-friendly interface for network analysis. Finally, designers often question whether such models would support the engagement of stakeholders, as they can come across as dry and complicated. Participatory modelling experiments demonstrate that stakeholder engagement can be an integral part of the modelling process (Schmitt Olabisi et al. 2010), as long as the process is developed with this intent from the start. 3. Can you model with limited data? Finally, some powerful computational models rely on very large datasets from online use, such as Facebook or Twitter data (Conte et al. 2012). A design problem however does not start with a dataset, but with a problem to solve. As a result, not every systemic problem will possess such a dataset. Design by definition takes place at an early stage of intervention, before the project itself has delivered data. Are computational models still relevant in these contexts? Here are a few responses to this concern. First, many designers may underestimate the amount of data available today, when leveraging online media and advanced data analysis techniques (e.g. natural language processing), which can turn large volumes of unstructured documents into structured datasets (Conte et al. 2012). Second, much can already be learnt form models based on limited data, complemented with plausible assumptions. Uncertain data can also be treated as the source of multiple scenarios (Kwakkel 2013). Finally, there is an opportunity to approach models in a lean, iterative manner: a first model is built based on theory and hypotheses, which can already help to explore and refine the assumptions of the stakeholders and designers; such a model will in turn inform which data to gather throughout the project, so that more and more refined versions can be developed iteratively. As the discussion above suggests, there is an opportunity in expanding current design methods with computational models, provided the following considerations: • Making assumptions explicit and addressing ethics questions, • Leveraging data from online tools and big data analysis methods, • Developing simulation interfaces for designers and stakeholders, • Leveraging designers and stakeholders’ intuition as input into the model, • Adopting an iterative approach to model building. The next steps in demonstrating this potential is to build case studies of design projects leveraging computational models. Adequate cases would concern issues affected by social complexity, which means that the interactions between individuals play a key a role in outcomes. Ideally, data sets should be available, either from the start of the project or through its development. Finally, such projects will require stakeholders that are curious and willing to experiment with new approaches. This paper showed that despite the fact that much of complexity science is based on quantitative, computational models, the literature on design concerned with complex systems refers nearly exclusively to qualitative approaches. It explored some of the key questions that may be motivating this reluctance to leverage computational models of social systems, deducted a set of guiding principles for their introduction in design for sustainability, and proposed next steps to this endeavour. Given the urgency to address some of today’s societal questions, no stone should be left unturned. Computational models have repeatedly proved their power to shed light on complex social dynamics of importance to sustainability. It is time to explore their application to the field of a design to enable the transition towards sustainable societies

On the E10/Massive Type IIA Supergravity Correspondence

In this paper we investigate in detail the correspondence between E10 and Romans' massive deformation of type IIA supergravity. We analyse the dynamics of a non-linear sigma model for a spinning particle on the coset space E10/K(E10) and show that it reproduces the dynamics of the bosonic as well as the fermionic sector of the massive IIA theory, within the standard truncation. The mass deformation parameter corresponds to a generator of E10 outside the realm of the generators entering the usual D=11 analysis, and is naturally included without any deformation of the coset model for E10/K(E10). Our analysis thus provides a dynamical unification of the massless and massive versions of type IIA supergravity inside E10. We discuss a number of additional and general features of relevance in the analysis of any deformed supergravity in the correspondence to Kac-Moody algebras, including recently studied deformations where the trombone symmetry is gauged.Comment: 68 pages, including 5 appendices, 5 figures. v2: Typos corrected, published version. v3:Title correcte

Integrability of Five Dimensional Minimal Supergravity and Charged Rotating Black Holes

We explore the integrability of five-dimensional minimal supergravity in the presence of three commuting Killing vectors. We argue that to see the integrability structure of the theory one necessarily has to perform an Ehlers reduction to two dimensions. A direct dimensional reduction to two dimensions does not allow us to see the integrability of the theory in an easy way. This situation is in contrast with vacuum five-dimensional gravity. We derive the Belinski-Zakharov (BZ) Lax pair for minimal supergravity based on a symmetric 7x7 coset representative matrix for the coset G2/(SL(2,R) x SL(2,R)). We elucidate the relationship between our BZ Lax pair and the group theoretic Lax pair previously known in the literature. The BZ Lax pair allows us to generalize the well-known BZ dressing method to five-dimensional minimal supergravity. We show that the action of the three-dimensional hidden symmetry transformations on the BZ dressing method is simply the group action on the BZ vectors. As an illustration of our formalism, we obtain the doubly spinning five-dimensional Myers-Perry black hole by applying solitonic transformations on the Schwarzschild black hole. We also derive the Cvetic-Youm black hole by applying solitonic transformations on the Reissner-Nordstrom black hole.Comment: 44 pages, 4 figure

Leveraging Tensions in Systemic Design

Complex systems do not lend themselves to simplification. Systemic designers have no choice but to embrace complexity, and in doing so, embrace opposing concepts and the resulting paradoxes. It is at the interplay of these ideas that they find the most fruitful regions of exploration. Within the field of systemic design, we find tensions between the positions that different practitioners and scholars take and the methods, practices and ideas they promote. Rather than viewing these differences as problems that need resolving, we see those tensions and differences in perspectives and ideas as opportunities to develop the field. Examples of tensions are: - Humanizing systems versus technical systems solutions - The do-ers/ entrepreneurs versus the thinkers/ philosophers in systemic design - Bottom-up system innovation versus top-down system innovation - The need for predictability and structure versus the need for surprise and emergence - Western ways of systems thinking versus indigenous, Eastern and other ways of systems thinking The goal of this workshop is to explore the tensions that exist in the field of systemic design and the ways they can be leveraged to develop the field

G2 Dualities in D=5 Supergravity and Black Strings

Five dimensional minimal supergravity dimensionally reduced on two commuting Killing directions gives rise to a G2 coset model. The symmetry group of the coset model can be used to generate new solutions by applying group transformations on a seed solution. We show that on a general solution the generators belonging to the Cartan and nilpotent subalgebras of G2 act as scaling and gauge transformations, respectively. The remaining generators of G2 form a sl(2,R)+sl(2,R) subalgebra that can be used to generate non-trivial charges. We use these generators to generalize the five dimensional Kerr string in a number of ways. In particular, we construct the spinning electric and spinning magnetic black strings of five dimensional minimal supergravity. We analyze physical properties of these black strings and study their thermodynamics. We also explore their relation to black rings.Comment: typos corrected (26 pages + appendices, 2 figures

A Note on Conserved Charges of Asymptotically Flat and Anti-de Sitter Spaces in Arbitrary Dimensions

The calculation of conserved charges of black holes is a rich problem, for which many methods are known. Until recently, there was some controversy on the proper definition of conserved charges in asymptotically anti-de Sitter (AdS) spaces in arbitrary dimensions. This paper provides a systematic and explicit Hamiltonian derivation of the energy and the angular momenta of both asymptotically flat and asymptotically AdS spacetimes in any dimension D bigger or equal to 4. This requires as a first step a precise determination of the asymptotic conditions of the metric and of its conjugate momentum. These conditions happen to be achieved in ellipsoidal coordinates adapted to the rotating solutions.The asymptotic symmetry algebra is found to be isomorphic either to the Poincare algebra or to the so(D-1, 2) algebra, as expected. In the asymptotically flat case, the boundary conditions involve a generalization of the parity conditions, introduced by Regge and Teitelboim, which are necessary to make the angular momenta finite. The charges are explicitly computed for Kerr and Kerr-AdS black holes for arbitrary D and they are shown to be in agreement with thermodynamical arguments.Comment: 27 pages; v2 : references added, minor corrections; v3 : replaced to match published version forthcoming in General Relativity and Gravitatio

Symétries cachées et trous noirs en supergravité

Upon dimensional reduction, certain supergravity theories exhibit symmetries otherwise undetected, called hidden symmetries. Not only do these symmetries teach us about the structure of the corresponding theories but moreover they provide methods to construct black hole solutions. In this thesis, we study the hidden symmetries of supergravity theories of particular interest and how these help constructing black hole solutions in dimensions D>4. We focus on three representative cases that are the symmetries appearing upon dimensional reduction to three, two and one dimensions. They are respectively described by finite, affine and hyperbolic algebras. In the first two cases, we develop and apply solution generating techniques.The first part of this thesis introduces the background concepts. We start with an introduction to black holes and other black objects in dimensions D>4. We present their subtleties, the known solutions and the conjectured ones. We insist on stationary axisymmetric solutions of vacuum and to the corresponding solution generating technique.The next chapter gives an introduction to Kac-Moody algebras. These indeed play a central role in this thesis as the symmetries appearing in three, two and one dimensions are described by three types of Kac-Moody algebras called respectively finite, affine and hyperbolic.In the second part, we first review the notion of dimensional reductions and how the hidden symmetries can be uncovered. The rest of the thesis contains three applications of these hidden symmetries.The first two concern five-dimensional minimal supergravity. Upon dimensional reduction to three dimensions, this theory exhibits a symmetry under the exceptional finite Kac-Moody algebra g2. This 14-dimensional algebra is the smallest exceptional finite Kac-Moody algebra. We use this duality to generate solutions while focussing mainly on black strings. After reduction to two dimensions, the symmetry becomes infinite-dimensional and is described by the affine extension of g2. Moreover, the two-dimensional theory is integrable, which allows us to develop another type of solution generating technique, hitherto applied only to vacuum gravity. In this work we generalize it to a case with matter fields.Finally, the notion of dimensional reduction to one dimension provides the necessary intuition for the conjecture of an algebraic formulation of M-theory, candidate to the unification of all interactions, based on the hyperbolic Kac-Moody algebra e10. In the last chapter of this thesis, we study an aspect of this correspondence, namely the e10 symmetry of massive type IIA supergravity in ten dimensions./On sait depuis longtemps que par un processus appelé réduction dimensionnelle, on peut faire apparaître dans certaines théories de gravitation des symétries autrement indétectées. On les appelle des symétries cachées. La mise en évidence de ces symétries non seulement nous informe sur la structure de ces théories, mais de plus elle permet d'élaborer des méthodes de construction de solutions de trous noirs. Dans cette thèse, nous étudions les symétries cachées de certaines théories de supergravité en dimensions supérieures à quatre. Nous nous concentrons sur trois cas représentatifs que sont les symétries apparaissant après réduction à trois, deux et une dimensions. Dans les cas des symétries apparaissant à trois et à deux dimensions nous développons et appliquons des méthodes de construction de solutions. La première partie introduit les concepts préliminaires. Nous commençons par une introduction aux trous noirs et autres objets noirs en dimensions supérieures à quatre. Nous en présentons les subtilités, les solutions connues à ce jour et celles qui ne sont encore que conjecturées. Nous insistons particulièrement sur les solutions stationnaires à symétrie axiale dans le vide et à la méthode de construction de solutions correspondante.Le chapitre suivant présente une introduction aux algèbres de Kac-Moody. Celles-ci jouent en effet un rôle central dans cette thèse puisque les symétries apparaissant à trois, deux et une dimensions sont décrites par trois types d'algèbres de Kac-Moody appelées respectivement finies, affines et hyperboliques. Dans la deuxième partie, nous rentrons dans le vif du sujet, en commençant par rappeler le principe des réductions dimensionnelles et la mise en évidence des différents types de symétries cachées. Les trois derniers chapitres contiennent ensuite trois applications de ces symétries cachées. Dans deux d'entre eux, nous nous concentrons sur la théorie de supergravité minimale à cinq dimensions. Après réduction à trois dimensions, cette théorie présente un symétrie cachée sous le groupe G2 qui, avec quatorze dimensions, est le plus petit des groupes de Lie exceptionnels. Nous utilisons cette dualité pour engendrer des solutions, en nous focalisant essentiellement sur les solutions de cordes noires. A deux dimensions, la symétrie est décrite par l'extension affine de G2. De plus, la théorie est alors complètement intégrable. Cela conduit à un autre type de méthode de construction de solutions, jusqu'alors uniquement appliquée à des théories dans le vide. Dans ce travail, nous la généralisons donc à un cas avec champs de matière. Enfin, la notion de réduction à une dimension fournit l'intuition d'une conjecture selon laquelle la théorie M, candidate à l'unification de toutes les interactions, pourrait être reformulée en une théorie basée sur l'algèbre de Kac-Moody hyperbolique e10. Dans le dernier chapitre de cette thèse, nous étudions un aspect de cette correspondance, à savoir, la symétrie sous e10 de la supergravité massive de type IIA à dix dimensions.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

On conserved charges of asymptotically flat and anti-de sitter spacetimes in arbitrary dimensions

Energy, and more generally conserved charges, is a subtle issue in general relativity and it is subject to controversy. Indeed, there are many different definitions in the literature and in some cases they do not all give the same charges. For example, as emphasized by Gibbons, et al. (2005), not even in four dimensions do all authors obtain the same expression for the energy of Kerr-AdS black holes and some of these expressions are in disagreement with the first law of black hole thermodynamics. I adopted in [arXiv:0705.0484] the method formulated by Regge & Teitelboim (1974). Based on the Hamiltonian formulation of gravitation, it associates to each asymptotic Killing vector a conserved charge without having to make any arbitrary choice. The charge is then expressed as a surface integral over a -sphere at spatial infinity. I investigate here conserved charges and asymptotic symmetries in both asymptotically flat and AdS spaces in arbitrary spacetime dimensions. The study is presented in general coordinates, including the ellipsoidal coordinates that are well adapted to the Kerr solution. © 2008 EAS EDP Sciences.SCOPUS: ar.kinfo:eu-repo/semantics/publishe

Symétries cachées et trous noirs en supergravité

Upon dimensional reduction, certain supergravity theories exhibit symmetries otherwise undetected, called hidden symmetries. Not only do these symmetries teach us about the structure of the corresponding theories but moreover they provide methods to construct black hole solutions. In this thesis, we study the hidden symmetries of supergravity theories of particular interest and how these help constructing black hole solutions in dimensions D>4. We focus on three representative cases that are the symmetries appearing upon dimensional reduction to three, two and one dimensions. They are respectively described by finite, affine and hyperbolic algebras. In the first two cases, we develop and apply solution generating techniques.The first part of this thesis introduces the background concepts. We start with an introduction to black holes and other black objects in dimensions D>4. We present their subtleties, the known solutions and the conjectured ones. We insist on stationary axisymmetric solutions of vacuum and to the corresponding solution generating technique.The next chapter gives an introduction to Kac-Moody algebras. These indeed play a central role in this thesis as the symmetries appearing in three, two and one dimensions are described by three types of Kac-Moody algebras called respectively finite, affine and hyperbolic.In the second part, we first review the notion of dimensional reductions and how the hidden symmetries can be uncovered. The rest of the thesis contains three applications of these hidden symmetries.The first two concern five-dimensional minimal supergravity. Upon dimensional reduction to three dimensions, this theory exhibits a symmetry under the exceptional finite Kac-Moody algebra g2. This 14-dimensional algebra is the smallest exceptional finite Kac-Moody algebra. We use this duality to generate solutions while focussing mainly on black strings. After reduction to two dimensions, the symmetry becomes infinite-dimensional and is described by the affine extension of g2. Moreover, the two-dimensional theory is integrable, which allows us to develop another type of solution generating technique, hitherto applied only to vacuum gravity. In this work we generalize it to a case with matter fields.Finally, the notion of dimensional reduction to one dimension provides the necessary intuition for the conjecture of an algebraic formulation of M-theory, candidate to the unification of all interactions, based on the hyperbolic Kac-Moody algebra e10. In the last chapter of this thesis, we study an aspect of this correspondence, namely the e10 symmetry of massive type IIA supergravity in ten dimensions./On sait depuis longtemps que par un processus appelé réduction dimensionnelle, on peut faire apparaître dans certaines théories de gravitation des symétries autrement indétectées. On les appelle des symétries cachées. La mise en évidence de ces symétries non seulement nous informe sur la structure de ces théories, mais de plus elle permet d'élaborer des méthodes de construction de solutions de trous noirs. Dans cette thèse, nous étudions les symétries cachées de certaines théories de supergravité en dimensions supérieures à quatre. Nous nous concentrons sur trois cas représentatifs que sont les symétries apparaissant après réduction à trois, deux et une dimensions. Dans les cas des symétries apparaissant à trois et à deux dimensions nous développons et appliquons des méthodes de construction de solutions. La première partie introduit les concepts préliminaires. Nous commençons par une introduction aux trous noirs et autres objets noirs en dimensions supérieures à quatre. Nous en présentons les subtilités, les solutions connues à ce jour et celles qui ne sont encore que conjecturées. Nous insistons particulièrement sur les solutions stationnaires à symétrie axiale dans le vide et à la méthode de construction de solutions correspondante.Le chapitre suivant présente une introduction aux algèbres de Kac-Moody. Celles-ci jouent en effet un rôle central dans cette thèse puisque les symétries apparaissant à trois, deux et une dimensions sont décrites par trois types d'algèbres de Kac-Moody appelées respectivement finies, affines et hyperboliques. Dans la deuxième partie, nous rentrons dans le vif du sujet, en commençant par rappeler le principe des réductions dimensionnelles et la mise en évidence des différents types de symétries cachées. Les trois derniers chapitres contiennent ensuite trois applications de ces symétries cachées. Dans deux d'entre eux, nous nous concentrons sur la théorie de supergravité minimale à cinq dimensions. Après réduction à trois dimensions, cette théorie présente un symétrie cachée sous le groupe G2 qui, avec quatorze dimensions, est le plus petit des groupes de Lie exceptionnels. Nous utilisons cette dualité pour engendrer des solutions, en nous focalisant essentiellement sur les solutions de cordes noires. A deux dimensions, la symétrie est décrite par l'extension affine de G2. De plus, la théorie est alors complètement intégrable. Cela conduit à un autre type de méthode de construction de solutions, jusqu'alors uniquement appliquée à des théories dans le vide. Dans ce travail, nous la généralisons donc à un cas avec champs de matière. Enfin, la notion de réduction à une dimension fournit l'intuition d'une conjecture selon laquelle la théorie M, candidate à l'unification de toutes les interactions, pourrait être reformulée en une théorie basée sur l'algèbre de Kac-Moody hyperbolique e10. Dans le dernier chapitre de cette thèse, nous étudions un aspect de cette correspondance, à savoir, la symétrie sous e10 de la supergravité massive de type IIA à dix dimensions.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe