448 research outputs found
Picard - an electrostatic particle in cell simulation code
No full textThis is a particle-in-cell plasma code 'picard' that was developed
by Jesper Lindkvist and Herbert Gunell with start in 2016 using
resources provided by the Swedish National Infrastructure for
Computing (SNIC) at the High Performance Computing Center North
(HPC2N), Umeå University, Sweden. Jesper Lindkvist was funded by
the Swedish National Space Board (SNSB project 201/15) and
Herbert Gunell by the Swedish National Space Agency (SNSA
project 108/18).
A paper based on the first version was published in A&A .
The present version has been updated to include ionisation as a source of cometary ions, and hdf5 files are used for writing the output. The changes in this version were made by Herbert Gunell.
The files included are:
picard.tgz Package containing all source file, some matlab m-files
that can be used for plotting of the results, and an input
file that was used for a simulation that will be used in an
upcoming publication by Herbert Gunell and Charlotte Götz.
fig-cur.mp4 Videoclip showing results from the simulation defined by the input file, specifically
three-dimensional current paths from different angles.
@author : Jesper Lindkvist
Email : [email protected]
@author : Herbert Gunell
Email : [email protected]
Type Theory Unchained: Extending Agda with User-Defined Rewrite Rules
No full textDependently typed languages such as Coq and Agda can statically guarantee the correctness of our proofs and programs. To provide this guarantee, they restrict users to certain schemes a- such as strictly positive datatypes, complete case analysis, and well-founded induction a- that are known to be safe. However, these restrictions can be too strict, making programs and proofs harder to write than necessary. On a higher level, they also prevent us from imagining the different ways the language could be extended. In this paper I show how to extend a dependently typed language with user-defined higher-order non-linear rewrite rules. Rewrite rules are a form of equality reflection that is applied automatically by the typechecker. I have implemented rewrite rules as an extension to Agda, and I give six examples how to use them both to make proofs easier and to experiment with extensions of type theory. I also show how to make rewrite rules interact well with other features of Agda such as-equality, implicit arguments, data and record types, irrelevance, and universe level polymorphism. Thus rewrite rules break the chains on computation and put its power back into the hands of its rightful owner: Yours.Programming Language
Half-maximal supergravity in three dimensions: supergeometry, differential forms and algebraic structure
No full textThe half-maximal supergravity theories in three dimensions, which have local SO(8) x SO(n) and rigid SO(8, n) symmetries, are discussed in a superspace setting starting from the superconformal theory. The on-shell theory is obtained by imposing further constraints; it is essentially a non-linear sigma model that induces a Poincare supergeometry. The deformations of the geometry due to gauging are briefly discussed. The possible p-form field strengths are studied using supersymmetry and SO(8, n) symmetry. The set of such forms obeying consistent Bianchi identities constitutes a Lie super co-algebra while the demand that these identities admit solutions places a further constraint on the possible representations of SO(8, n) that the forms transform under which can be easily understood using superspace cohomology. The dual Lie superalgebra can then be identified as the positive sector of a Borcherds superalgebra that extends the Lie algebra of the duality group. In addition to the known p = 2, 3, 4 forms, which we construct explicitly, there are five-forms that can be non-zero in supergravity, while all forms with p > 5 vanish. It is shown that some six-forms can have non-trivial contributions at order alpha'.</p
35 frågor och svar inför en edering av Jesper Swedbergs Swensk Ordabok
No full textIn this paper, the author accounts for his work on editing an early 18th centurydictionary manuscript, bishop Jesper Swedberg’s Swensk Ordabok. A similar project– i.e. editing an old, hitherto unpublished dictionary manuscript – has beenperformed in Sweden only once before. This means that there is no tradition onwhich the solution of many problems concerning the edition of Swedberg'sdictionary could be based. For instance, there are no less than five manuscriptversions. Which of them should be selected as the basis manuscript of the edition,and to what extent should the differences between the manuscripts be accounted forin the edition? As argued by the author, none of the manuscripts written bySwedberg himself can serve as the basis manuscript, since they are all incomplete.Also, a relatively restricted account of the differences between the manuscripts issuggested; otherwise, the readability of the edition would be too low
Exploration and reflection in interactive art: Glass pond
No full textGlass Pond is an interactive artwork designed to engender exploration and reflection through an intuitive, tangible interface and a simulation agent. It is being developed using iterative methods. A study has been conducted with the aim of illuminating user experience, interface, design, and performance issues.The paper describes the study methodology and process of data analysis including coding schemes for cognitive states and movements. Analysis reveals that exploration and reflection occurred as well as composing behaviours (unexpected). Results also show that participants interacted to varying degrees. Design discussion includes the artwork's (novel) interface and configuration. Copyright the author(s) and CHISIG
Real Estate Agent as a profession : A study regarding the occupation´s professional categorization
No full textTitel: Fastighetsmäklare som profession - En studie om yrkets professionskategorisering Nivå: Kandidatuppsats i ämnet Fastighetsvetenskap Författare: Jesper Arnshed Handledare: Karin Staffansson Pauli Datum: Maj 2021 Syfte: Med utgångspunkt i de fördelar som tillkommer av att nå en högre profession, är syftet med denna studie att undersöka fastighetsmäklarbranschens syn på kategoriseringen av mäklarprofessionen Metod: Denna studie har applicerat en kvalitativ forskningsmetodik. Med hjälp av semistrukturerade intervjuer har empirisk data kopplats till den teoretiska bakgrunden, om de bakomliggande aspekterna som bidrar till fastighetsmäklarens professionskategorisering. Resultat & Slutsats: Resultatet visar att mäklarens strävan mot högre profession delvis försvåras till följd av glappet mellan teori och praktik, samt de odefinierade regel- och ramverk som mäklare har att förhålla sig till. Om den nya lagändringen istället hade varit förankrad i de reella utmaningar och faktorer som påverkar förtroendet och yrkesintegriteten för mäklaren, finns där stora möjligheter för yrkesgruppen att nå en högre profession. Uppsatsens bidrag till ämnet: Studien har bidragit med ytterligare förståelse för mäklarens profession och vad som förhindrar en högre kategorisering. Förslag till framtida forskning: Efterhand som lagändringen har blivit implementerad vore det intressant att studera vilka förändringar som fått genomslag i branschen och för mäklaren.Title: Real Estate Agent as a profession - A study about the occupation´s professional categorization Level: Bachelor's thesis within Real Estate Science Author: Jesper Arnshed Supervisor: Karin Staffansson Pauli Date: May 2021 Aim: Based on the benefits of reaching a higher profession, the aim of this study is to examine the real estate industry's view on the categorization of the broker´s profession. Method: This study has applied a qualitative research methodology. With the help of semi-structured interviews, additional dimensions have supplemented the theoretical background, about the underlying aspects that are derived from the real estate agent's professional classification. Result & Conclusions: The result shows that the brokers´ aim towards a higher profession is partly prevented due to the gap between theory and practice, and the undefined rules and regulations that brokers must deal with. If the new law change had instead been rooted in the real challenges and aspects that affect the trust and professional integrity among brokers, there are great opportunities for the occupational group to reach a higher profession. Contribution of the thesis: The study contributed with additional understanding to the broker´s profession and what prevents a higher categorization. Suggestions for future research: As the changes in the law are implemented, it would be interesting to study what changes have had an impact in the industry and for the broker.
Topologically gauged superconformal Chern-Simons matter theories.
No full textAbstract: By coupling N = 8 superconformal matter to N = 8 superconformal Chern- Simons gravity in three dimensions we obtain theories with novel terms in the scalar po- tential leading to AdS3 solutions and superconformal symmetry breaking. If we start from the theory derived by Bagger, Lambert and Gustavsson, our coupled theory either inherits the SO(4) gauge group or reduces it to SO(3). If the construction is instead based on a free matter theory we find that the gravitational topological gauging also requires the in- troduction of a Chern-Simons gauge sector resulting in a consistent theory for any SO(N) gauge group
Dependently Typed Languages in Statix
No full textStatic type systems can greatly enhance the quality of programs, but implementing a type checker that is both expressive and user-friendly is challenging and error-prone. The Statix meta-language (part of the Spoofax language workbench) aims to make this task easier by automatically deriving a type checker from a declarative specification of a type system. However, so far Statix has not been used to implement dependent types, which is a class of type systems which require evaluation of terms during type checking. In this paper, we present an implementation of a simple dependently typed language in Statix, and discuss how to extend it with several common features such as inductive data types, universes, and inference of implicit arguments. While we encountered some challenges in the implementation, our conclusion is that Statix is already usable as a tool for implementing dependent types
The tensor hierarchy simplified
No full textA compact formulation of the field-strengths, Bianchi identities and gauge transformations for tensor hierarchies in gauged maximal supergravity theories is given. A key role in the construction is played by the recently-introduced tensor hierarchy algebra.</p
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