2,426 research outputs found

    Topological Susceptibility from Slabs

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    In quantum field theories with topological sectors, a non-perturbative quantity of interest is the topological susceptibility chi_t. In principle it seems straightforward to measure chi_t by means of Monte Carlo simulations. However, for local update algorithms and fine lattice spacings, this tends to be difficult, since the Monte Carlo history rarely changes the topological sector. Here we test a method to measure chi_t even if data from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as slabs. Assuming a Gaussian distribution of these charges, this method enables the evaluation of chi_t, as we demonstrate with numerical results for non-linear sigma-models.Comment: 23 pages, 8 figures, 6 table

    Advancement in Conceptualizing Cross-Border Daily Mobility: the Benelux Context in the European Union

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    Based on specific characteristics of mobility, the cross-border commuter status still has some ambiguities, whether in legal, geographic, economic or more generally in social or cultural terms. This paper aims at providing theoretical advancement to this specific cross-border mobility, especially through the transfer of a theoretical model using a cross-scale analysis based on two complementary concepts. The first corresponds to ‘border confirming’ and is measured at the macro level, including the economic differentials on both sides of the border. The second concept is called ‘border transcending’ and focuses on the individual level. It is based on the assessment of the psychosocial barriers that may fade as the daily practices of the border rise. This exploratory approach is tested within the European context of Benelux. The results, although they cannot be generalised due to a lack of comparable data, offer research perspectives. So far, the existence of a cross-border catchment area, tested on the Belgian cross-border commuters working in Luxembourg, is a reality for many

    An Approach for spatial and temporal data analysis: application for mobility modeling of workers in Luxembourg and its bordering areas

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    In this paper, we propose a general visual analytic approach to synthesis very large spatial data and discover interesting knowledge and unknown patterns from complex data based on Origin-Destination (OD) matrices. The research studies of Tobler constitute a good basis in this topic. This paper is interested in the proposal of 2 methods entitled respectively ?Weighted Linear Directional Mean: WLDM? and ?DS-WLDM?. The latter incorporates the Dempster-Shafer theory of evidence with WLDM. Both of the developed methods are an extension of ?Linear Directional Mean: LDM? for mobility modeling. With classical techniques such as LDM among others, the results of data mapping are not intelligible and easy to interpret. However with both WLDM and DS-WLDM methods it is easy to discover knowledge without losing a lot of information which is one of the interests of this paper. This proposal is generic and it intends to be applied for data mapping such as for geographical presentation of social and demographic information (e.g. mobility of people, goods and information) according to multiple spatial scales (e.g. locality, district, municipality). It could be applied also in transportation field (e.g. traffic flow). For the application, administrative data is used in order to evaluate spatial and temporal aspects of the daily and the residential mobility of workers in Luxembourg and its bordering areas.Mobility modeling; data mapping; spatial mobility; geographic knowledge discovery; location uncertainty; daily and residential mobility

    Impacts de la mobilité résidentielle transfrontaliÚre sur les espaces de la vie quotidienne d'individus actifs du Luxembourg.

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    À partir d'une enquĂȘte effectuĂ©e par le CEPS/INSTEAD et la fondation Forum Europa, cet article analyse le phĂ©nomĂšne de mobilitĂ© rĂ©sidentielle transfrontaliĂšre et son impact sur les dĂ©placements quotidiens. RĂ©alisĂ©e au printemps 2008, cette enquĂȘte porte sur les actifs occupĂ©s rĂ©sidant initialement au Luxembourg qui se sont installĂ©s dans un pays frontalier entre 2001 et 2007, tout en conservant leur emploi au Grand-DuchĂ©. Pour un grand nombre d'entre eux, le dĂ©mĂ©nagement transfrontalier a permis d'accĂ©der Ă  un logement plus grand, voire d'en devenir propriĂ©taire. NĂ©anmoins, l'analyse des dĂ©placements quotidiens montre que la plupart de ces personnes a dĂ» consentir Ă  de nombreuses concessions en termes de mobilitĂ© pour accĂ©der au logement souhaitĂ©. Cela se ressent particuliĂšrement pour le trajet domicile/travail dont la distance moyenne a doublĂ©, ce qui a renforcĂ© la dĂ©pendance Ă  l'automobile des personnes concernĂ©es . En dehors mĂȘme du travail, la localisation des autres activitĂ©s quotidiennes se trouve modifiĂ©e Ă  la suite du dĂ©mĂ©nagement. Des indicateurs synthĂ©tiques issus de la gĂ©ostatistique permettent d'analyser la reconfiguration des lieux de ces activitĂ©s. MalgrĂ© la relocalisation de beaucoup d'entre elles autour du nouveau lieu de rĂ©sidence, une certaine inertie des comportements se traduit par le maintien de prĂšs d'une activitĂ© sur trois au Luxembourg. DĂšs lors, la dispersion des espaces d'activitĂ©s augmente pour certains enquĂȘtĂ©s. Elle est liĂ©e Ă  la part des activitĂ©s transfĂ©rĂ©es vers le pays de rĂ©sidence, varie fortement selon la nationalitĂ© ; elle est plus forte pour les Luxembourgeois et les Portugais. Les personnes originaires des rĂ©gions frontaliĂšres, qui retournent dans leur pays d'origine, gardent Ă©galement prĂšs d'un quart de leurs activitĂ©s au Grand-DuchĂ© : cela tĂ©moigne de l'importance du lieu de travail dans la structuration des espaces de vie quotidienne et d'un capital spatial dĂ©jĂ  mis en Ă©vidence dans le cas d'actifs rĂ©sidant au Luxembourg

    The Slab Method to Measure the Topological Susceptibility

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    In simulations of a model with topological sectors, algorithms which proceed in small update steps tend to get stuck in one sector, especially on fine lattices. This distorts the numerical results; in particular it is not straightforward to measure the topological susceptibility chi_t. We test a method to measure chi_t even if configurations from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as "slab". This enables the evaluation of chi_t, as we demonstrate with numerical results for non-linear sigma-models and for 2-flavour QCD. In the latter case, the gradient flow is applied for the smoothing of the gauge configurations, and the slab method results for chi_t are stable over a broad range of flow times.Comment: 7 pages, 7 figures, talk presented at the 34th International Symposium on Lattice Field Theory, 24-30 July 2016, Southampton, UK. Minor corrections, references added, Fig. 5 replace

    Cartographier une enquĂȘte Ă  l'Ă©chelle intra-urbaine: bien-ĂȘtre et personnes ĂągĂ©es de la ville de Luxembourg

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    Cet article a pour objectif d’exposer une dĂ©marche mĂ©thodologique originale. Elle vise, Ă  partir d’un Ă©chantillon stratifiĂ© spatialement d’une population enquĂȘtĂ©e, Ă  reconstituer la population totale et de la projeter dans l’espace urbain de la ville Ă  une Ă©chelle plus petite. Cela permet de donner une dimension gĂ©ographique intra-urbaine aux informations contenues dans les rĂ©sultats d’enquĂȘte. Pour cela, nous nous basons sur l’exemple de l’enquĂȘte « Personnes ÂgĂ©es Ville de Luxembourg », effectuĂ©e en 2002, qui avait pour but d’apprĂ©cier les besoins de ces personnes vivant Ă  leur domicile.GIS ; Mapping ; Survey ; Elderly ; Wellbeing

    Topology in the 2d Heisenberg Model under Gradient Flow

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    The 2d Heisenberg model --- or 2d O(3) model --- is popular in condensed matter physics, and in particle physics as a toy model for QCD. Along with other analogies, it shares with 4d Yang-Mills theories, and with QCD, the property that the configurations are divided in topological sectors. In the lattice regularisation the topological charge QQ can still be defined such that Q∈ZQ \in \mathbb{Z}. It has generally been observed, however, that the topological susceptibility χt=⟹Q2⟩/V\chi_{\rm t} = \langle Q^2 \rangle / V does not scale properly in the continuum limit, i.e. that the quantity χtΟ2\chi_{\rm t} \xi^2 diverges for Ο→∞\xi \to \infty (where Ο\xi is the correlation length in lattice units). Here we address the question whether or not this divergence persists after the application of the Gradient Flow.Comment: 10 pages, LaTex, 7 figures, 2 tables, talk presented at the XXXI Reuni\'on Anual de la Divisi\'on de Part\'iculas y Campos de la Sociedad Mexicana de F\'isica (CINVESTAV, Mexico City

    Simulation of land use changes using cellular automata and artificial neural network

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    This paper presents a method integrating artificial neural network (ANN) in cellular automata (CA) to simulate land use changes in Luxembourg and the areas adjacent to its borders. The ANN is used as a base of CA model transition rule. The proposed method shows promising results for prediction of land use over time. The ANN is validated using cross-validation technique and Receiver Operating Characteristic (ROC) curve analysis, and compared with logit model and a support vector machine approach. The application described in this paper highlights the interest of integrating ANNs in CA based model for land use dynamic simulation.Artificial neural network; Cellular automata; Modelling; Land use changes; Spatial planning and dynamics

    Pour une approche normative de l’amĂ©nagement. Simulation de scĂ©narios de dĂ©veloppement rĂ©sidentiel au Luxembourg

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    National audienceL’objectif de cette communication est de prĂ©senter les rĂ©sultats obtenus dans le cadre d’un travail de thĂšse (projet COSMELUX, financĂ© par le Fond National de la Recherche du Luxembourg, 2010-2014) dont l’objectif est de proposer et d’évaluer diffĂ©rents scĂ©narios de croissance rĂ©sidentielle sur le Grand-DuchĂ© du Luxembourg Ă  l’horizon 2030. Les simulations de dĂ©veloppement rĂ©sidentiel ont Ă©tĂ© rĂ©alisĂ©es avec l’application MUP-City (Tannier et al., 2012). Les scĂ©narios simulĂ©s ont d’abord Ă©tĂ© Ă©valuĂ©s au moyen de mesures d’accessibilitĂ© spatiale (distance minimale pour atteindre l’amĂ©nitĂ© la plus proche, nombre d’amĂ©nitĂ©s Ă  une distance donnĂ©e, indicateurs de diversitĂ© de l’offre en amĂ©nitĂ©s) calculĂ©es avec MUP-City
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