Constraints, Adjunctions and (Co)algebras

AbstractThe connection between constraints and universal algebra has been looked at in, e.g., Jeavons, Cohen and Pearson, 1998, and has given interesting results. Since the connection between universal algebra and category theory is so obvious, we will in this paper investigate if the usage of category theory has any impact on the results and/or reasoning and if anything can be gained from this approach.We construct categories of problem instances and of solutions to these, and, via an adjunction between these categories, note that the algebras give us a way of describing 'minimality of a problem,' while the coalgebras give a criterion for deciding if a given set of solutions can be expressed by a constraint problem of a given arity.Another pair of categories, of sets of relations and of sets of operations on a fixed set, is defined, and this time the algebras we get give an indication of the 'expressive power' of a set of constraint types, while the coalgebras tell us about the computational complexity of the corresponding constraint problem

Multigrid solver for axisymmetrical 2D fluid equations

We have developed an efficient algorithm for steady axisymmetrical 2D fluid equations. The algorithm employs multigrid method as well as standard implicit discretization schemes for systems of partial differential equations. Linearity of the multigrid method with respect to the number of grid points allowed us to use $256\times 256$ grid, where we could achieve solutions in several minutes. Time limitations due to nonlinearity of the system are partially avoided by using multi level grids(the initial solution on $256\times 256$ grid was extrapolated steady solution from $128\times 128$ grid which allowed using "long" integration time steps). The fluid solver may be used as the basis for hybrid codes for DC discharges.Comment: preliminary version; presented at 28 ICPIG, July 15-20, 2007, Prague, Czech Republi

Variable and value elimination in binary constraint satisfaction via forbidden patterns

Variable or value elimination in a constraint satisfaction problem (CSP) can be used in preprocessing or during search to reduce search space size. A variable elimination rule (value elimination rule) allows the polynomial-time identification of certain variables (domain elements) whose elimination, without the introduction of extra compensatory constraints, does not affect the satisfiability of an instance. We show that there are essentially just four variable elimination rules and three value elimination rules defined by forbidding generic sub-instances, known as irreducible existential patterns, in arc-consistent CSP instances. One of the variable elimination rules is the already-known Broken Triangle Property, whereas the other three are novel. The three value elimination rules can all be seen as strict generalisations of neighbourhood substitution.Comment: A full version of an IJCAI'13 paper to appear in Journal of Computer and System Sciences (JCSS

Technical Interoperability for Machine Connectivity on the Shop Floor

This paper presents a generic technical solution that can increase Industry 4.0 maturity by collecting data from sensors and control systems on the shop floor. Within the research project “5G-Enabled Manufacturing”, an LTE (Long-Term Evolution) network with 5G technologies was deployed on the shop floor to enable fast and scalable connectivity. This network was used to connect a grinding machine to a remote private cloud where data was stored and streamed to a data analytics center. This enabled visibility and transparency of the production data, which is the basis for Industry 4.0 and smart manufacturing. The solution is described with a focus on high-level communication technologies above wireless communication standards. These technologies are discussed regarding technical interoperability, focusing on the system layout, communication standards, and open systems. From the discussion, it can be derived that generic solutions such as this are possible, but manufacturing end-users must expand and further internalize knowledge of future information and communication technologies to reduce their dependency on equipment and technology providers

The upgrade of the ALICE TPC with GEMs and continuous readout

The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020.publishedVersio

Xi Production in pp Collisions at Different Multiplicity and Spherocity

The protons and neutrons that make up the atoms in our Universe are part of a larger group of particles called hadrons. Hadrons have an inner structure consisting of the elementary particles called quarks. The interaction of the quarks is described by the quantum field theory quantum chromodynamics. Quantum chromodynamics predicts a confinement of the quarks within the hadrons, but at large temperatures and/or energy densities there will be a phase transition from hadrons into a deconfined state called quark gluon plasma. The study of these two regimes in quantum chromodynamics have, to a large extent, been separate. The deconfined QGP regime has mainly been considered in large systems (heavy-ion collisions). The formation of a possible medium or significant final state interactions have not been considered in small systems. The two different branches of research are now starting to overlap after similar quark gluon plasma-like signatures have been observed in both small and large systems. In this thesis, signatures of the quark gluon plasma has been studied in small systems. The goal was to show that the event estimator transverse spherocity could discriminate between the confined and deconfined regime of quantum chromodynamics. Transverse spherocity looks at the produced particle distribution to quantify the topology of the event. Events were most of the momentum is distributed along an axis (called jetty) indicates that there has been a hard parton-parton (a parton is either a quark or a gluon) interaction, and so it is presumably less likely that a quark gluon plasma was formed. If the momentum is instead isotropically distributed it would suggest an event with several soft parton interactions, where it seems more likely that a medium could be formed. This thesis uses the $\Xi^-$ hadron to control the hypothesis that transverse spherocity can select events where the quark gluon plasma-like effects are more or less pronounced. $\Xi^-$ was chosen since it is sensitive to a signature of the quark gluon plasma called strangeness enhancement. Strangeness enhancement is multiplicity dependent, and the data shows a larger production of $\Xi^{\mp}$ compared to charged particles in high multiplicity events with respect to minimum bias events. The data is compared to the monte carlo generator PYTHIA, which does not include any mechanism for strangeness enhancement, and the generated data does not show any strangeness enhancement. Comparison between the two transverse spherocity selections shows a larger $\Xi^{\mp}$ production compared to non-strange hadrons in isotropic events than in jetty events. However, there is also an observed bias of the spherocity selection which leads to a separation of isotropic and jetty events. Because of this it is not possible to conclude that transverse spherocity is able to discriminate between the quark gluon plasma regime and the confined regime.Det ultimata målet med partikelfysik är en förståelse av de (väldigt små) byggstenar som bygger upp vårt universum. Djur, planeter och solsystem är alla uppbyggda av atomer, vars inre kärna består av protoner och neutroner. Dessa protoner och neutroner har även de en inre struktur, och är uppbyggda av partiklar som heter kvarkar. Kvarkarna kommunicerar genom att skicka partiklar som heter gluoner mellan varandra. Dessa gluoner binder ihop kvarkarna så att de inte kan lämna protonerna och neutronerna. Vid väldigt höga temperaturer kan protonerna och neutronerna lösas upp till en soppa av kvarkar och gluoner. Denna soppa heter kvark-gluonplasman, och i den kan kvarkarna nu röra sig fritt. Historiskt sett har fysiker trott att endast kollisioner mellan tunga atomer kan komma upp i tillräckligt höga temperaturer för att skapa soppan. I sådana experiment används atomer som består av 208 protoner och neutroner och det skapas därför väldigt mycket energi när de två atomerna slår i varandra. För två år sen så hittades bevis som tyder på att kvark-gluonplasman även skapas i kollisioner mellan två protoner. Tidigare har kollisioner mellan tunga atomer och protonkollisioner jämförts, och de effekter som inte syntes i protonkollisioner antog man var unika egenskaper av kvark-gluonplasman. Nu när det finns bevis för att kvark-gluonplasman kan bildas i protonkollisioner försvåras forskningen om kvark-gluonplasman eftersom det inte längre finns något att jämföra med. Därför söker forskare nu efter andra sätt att studera kvark-gluonplasmans specifika egenskaper. I detta examensarbete så har vi undersökt om formerna på kollisionerna kan användas som ett sätt att hitta de kollisioner där kvark-gluon plasman har bildats. Proton kollisioner som bildat en soppa har väldigt sannolikt en sfärisk form. Hypotesen var att om man väljer ut kollisioner som är väldigt sfäriska så har man valt de kollisioner som har bildat en soppa. På samma sätt kan man välja kollisioner som inte sprider ut sig sfäriskt, dessa är då troligen kollisioner där soppan inte kunde bildas. Resultaten visar en tydlig skillnad mellan de sfäriska och icke-sfäriska kollisionerna. Dock så har det faktum att man väljer mellan sfäriska och icke-sfäriska kollisioner också en effekt på resultatet. Detta betyder att den observerade skillnaden inte enbart beror på om det har (eller inte har) skapats en plasma i kollisionen. Våra resultat antyder att man med hjälp av formen på kollisionen kan skilja på kollisioner där soppan skapades eller icke-skapades, men det går för närvarande inte att säga med säkerhet

[Insert popcultural reference here] : Popular Culture in the Curriculum and Textbooks for Religious Education at Swedish Upper Secondary School

Popular culture is a phenomenon of growing importance in the society today. Children and teenagers are increasingly using popular culture in their everyday life to reflect and answer questions about their identities and the meaning of life. Swedish primary and upper secondary schools are expected to prepare their students for adulthood and to provide them with tools to explain understand and problematize contemporary society. From this perspective it is relevant to question whether the schools achieve this and whether the instruction given there represents the contemporary society. For the purpose of knowing more about how popular culture is perceived and dealt with in the Swedish education system, this study examines how eight textbooks in Religious Education (RE) and the national curriculum for upper secondary school discuss and treat popular culture.  The study focuses on when and in what ways the textbooks mention popular culture and if the curriculum provides any supportive base for including popular culture in religious education. The textual analysis of the RE textbooks illustrates that popular culture is seldom mentioned in the books and rarely discussed or reflected upon. The most common instances of popular culture in the textbooks are small references outside of the main text. The authors of the textbooks have thus not integrated thorough discussion about popular culture but rather added in some popular cultured references where they thought it would fit in the texts. With regard to the national curriculum for Religious Education, there is some recognition of how to use and discuss popular culture and its importance for students is acknowledged. However, this recognition is only explained in the comments to the curriculum and not in the document itself.   The apparent lack of popular culture in RE textbooks is in this study discussed from the perspective of power relations and popular culture perceived as a culture form with low status. As historians have asserted, cultural forms that have historically been called and perceived as low culture have also been used as objects for the exercise of power. While popular culture today has taken over functions that traditionally belong to the established religions, and while in some cases popular culture can be perceived as a form of religion, popular culture is still commonly viewed as a lower form of culture for the masses and consequently a cultural form with lower status.  This exercise of power has usually been downward in the social hierarchy, from middle class towards working class, to today’s groups of adults towards youth. It may be this trend that emerges when this study shows the lack of popular culture in RE textbooks. It is adults who write the curriculum, it is adults who write the textbooks and it is adults who teach in schools. Popular culture is said to belong to the young and therefore it does not have sufficiently high status to be brought in to the classroom.