Loop scattering in two-dimensional QCD

Using the integrability conditions that we recently obtained in QCD$_2$ with massless fermions, we arrive at a sufficient number of conservation laws to be able to fix the scattering amplitudes involving a local version of the Wilson loop operator.Comment: 6 pages, plain tex

Current Algebra of Super WZNW Models

We derive the current algebra of supersymmetric principal chiral models with a Wess-Zumino term. At the critical point one obtains two commuting super Kac-Moody algebra as expected, but in general there are intertwining fields connecting both right and left sectors, analogously to the bosonic case. Moreover, in the present supersymmetric extension we have a quadratic algebra, rather than an affine Lie algebra, due to the mixing between bosonic and fermionic fields since the purely fermionic sector displays a Lie algebra as well.Comment: 13 page

Sustainable residential districts : the residents' role in project success

Sustainable residential districts have been realized worldwide. These districts are promoted to be efficient in the use of natural materials and sustainable energy resources. Realization of sustainable residential districts can strongly contribute to achieve environmental objectives as imposed by governmental policies as well as to create good living conditions for people. Sustainable residential districts are quite complex construction projects with special focus on reduction of environmental impact in the use phase. These projects emphasize the essence of the residents’ role in achieving project objectives. A quick scan of already realized sustainable residential districts in Europe revealed that these projects are still not in the mainstream. Moreover, some districts have failed to achieve their sustainability objectives. Frequently mentioned problems are related to complexity in use, dysfunction of unproven technologies, having unrealistic objectives and mismatch with residents needs and expectations. A literature review on project success revealed that there is a lack of information regarding a comprehensive evaluation of project success from both managerial and psychological perspectives. Moreover, understanding managerial as well as psychological aspects, in addition to existing technical aspects, will create a better insight into success of sustainable residential districts. The review revealed also that there is a need to investigate success criteria for sustainable residential districts. This leads us to the first research question. Research question 1: Which project success criteria are relevant to assess success in sustainable residential district projects? Project factors are circumstances or facts which contribute to a project result. They are project specific and are related to project success criteria. The literature review revealed also that there is a need to investigate success factors for sustainable residential districts. This leads us to the second project question. Research question 2: Which managerial project factors can influence success in sustainable residential district projects? Most of the objectives of sustainable residential districts are related to decrease consumption of natural resources and to increase energy efficiency. For this aim, sustainable heating, ventilation and air conditioning systems (HVAC) have to be implemented. The way residents use sustainable HVAC systems can strongly influence their performance in the use phase. Technical specifications and design considerations of HVAC systems can strongly influence residents’ behavior. Therefore, there is a need to understand how residents act in their technological environment and what motivates them to behave in a pro-environmental way. Hence, there is also a need to understand residents’ needs, expectations, perceptions and attitudes toward sustainable HVAC systems. This leads us to the third and forth research questions. Research question 3: How can technical specifications implemented in dwellings influence residents’ behavior in sustainable residential district projects? Research question 4: How can residents-related factors influence the performance of sustainable residential district projects? To answer the first and the second questions a literature study and a case study research were used. Chapter 3 introduces an extensive literature review on both project success criteria and project success factors. This review provided better insight into leading researches and mostly used models of success criteria. The review provided a list of 22 general project success criteria. These criteria have then been ranked according to their relevance and grouped in three groups of criteria related to People, Planet and Profit. The review discussed also models of project success factors and introduced the ‘Project-specific Formal System Model’ as research model for the analysis of the case study. In Chapter 4 a case study method is used to indicate the relevance of project success criteria in relation to sustainable residential district projects. For this purpose, published reports of Six European best practice sustainable residential districts have been used. These districts are BedZED in London, England, Bo-01 in Malmö, Sweden, Eco-Viikki in Helsinki, Finland, EVA-Lanxmeer in Culemborg, Kronsberg in Hannover, Germany and Vauban in Freiburg, Germany. The results revealed that the Golden Triangle criteria (Schedule, Quality and Budget) are not sufficient to ensure success in sustainable residential district projects. The results revealed that the following criteria are relevant to assess success in sustainable residential district projects: Health, Technology Transfer, Efficient use of energy, Efficient use of water, Efficient mobility, Sourcing policy and Achieving social mix. The results revealed also that success in sustainable residential district projects can be explained by the following factors as: Technologies are accepted by the residents, Matching residents’ needs and expectations with technical specifications and design considerations, Project parties and residents are simulated, instead of forced, to work and behave in a sustainable way, Health and comfort are considered for sourcing materials instead of restricting the sourcing requirements, Creating a learning curve by realizing large-scale projects in phases, Having long term cooperation relationship among project team members. The results revealed also that residents of sustainable residential districts strongly contribute to project success. Residents’ beliefs, needs and expectations toward the use of HVAC technologies have a strong influence on project performance in the use phase. The theory of planned behavior (Fishbein & Ajzen, 2012) is used as theoretical framework to answer research questions 3 and 4. The theory of planned behavior assumes that behavior is determined by the intention to perform it. In turn, behavioral intentions are assumed to be determined by attitudes, subjective norms and perceived behavioral control. Face-to-face interviews were hold with 135 residents of De Caaien; a Dutch residential district where a heat pump system is implemented for space heating and hot water supply. The design of the questionnaire is based on a formal questionnaire and practical instructions as suggested by the theory of planned behavior. A pilot research was performed to provide behavioral elements related to automatically operating of the heating system. Automatically operating of the heating has been advised by the HVAC company as the most energy saving and environmental friendly behavior. Data analysis revealed that residents’ attitude and perceived behavioral control explained the intention toward operating the heating system automatically. Social norms had no effect on explaining residents’ behavior. On average, the intention to use the heat pump system automatically was positive. In spite of that residents quite differed in their responses. This result indicates that residents differed in their perceptions toward the operation of the system and that the system performed differently in different household conditions. Residents’ behavioral beliefs related to space heating and hot water supply are the most important beliefs to explain residents’ attitude toward operating the heating system automatically. These beliefs are related to residents’ physiological needs and are overvalued to beliefs related to environment protection and cost saving. Residents who formed positive attitude and positive perceived behavioral control toward the automatically operating of the heating system operated the heat pump system properly. This behavior resulted in lower energy consumption and lower energy bills. This research provided new insights into project success criteria and project success factors and their relevance for sustainable residential district projects. This research provided also new insights into residents’ behavioral beliefs related to the use of sustainable heating systems. This research explained also how residents interact with their sustainable heating systems and how they can influence the performance their heating system on sustainability and energy consumption. This research provided also a tested and validated questionnaire that can be used for comparable behavior researches

Interacting Dark Energy: Possible Explanation for 21-cm Absorption at Cosmic Dawn

A recent observation points to an excess in the expected 21-cm brightness temperature from cosmic dawn. In this paper, we present an alternative explanation of this phenomenon, an interaction in the dark sector. Interacting dark energy models have been extensively studied recently and there is a whole variety of such in the literature. Here we particularize to a specific model in order to make explicit the effect of an interaction.Comment: 5 pages, 2 figures. Discussion improved, new references, conclusions unchanged. Accepted in EPJ