Inhomogeneous tachyon dynamics and the zipper

We study the process of inhomogeneous tachyon condensation in an intersecting D1- and anti-D1-brane system using an effective tachyon DBI action. By switching to the Hamiltonian formalism, we numerically solve for the dynamical evolution of the system at a small intersection angle. We find that the decay proceeds indefinitely and resembles the action of two zippers moving away from the intersection point at the speed of light, zipping the branes together and leaving inhomogeneous tachyon matter behind. We also discuss the range of validity of our analysis and discuss the relation of the D1-anti-D1 description of the system to one in terms of an intersecting D1-D1-brane pair.Comment: 23 pages, 12 figures. v2: added references; v3: more references, published versio

Erityisalojen hankintalain mukainen yhteishankinta avoimella menettelyllä

Tiivistelmä. Työn tavoitteena on tuoda yhteen avoimella menettelyllä toteutettavassa Erityisalojen hankintalain mukaisessa yhteishankinnassa huomioitavat hankintamenettelyyn vaikuttavat seikat. Työssä käydään läpi julkisen hankinnan tunnuspiirteet, sovellettavan hankintalain määräytyminen, kynnysarvot, yhteishankinnan vaikutus sovellettaviin säännöksiin kuin myös avoimen hankintamenettelyn ilmoitus- ja toteutusprosessi. Noudatettavien säännösten ja prosessikulun jäljille päästiin perehtymällä nykyisiin hankintalakeihin sekä aihetta käsittelevään viimeaikaiseen kirjallisuuteen. Työssä havaittiin, että hankintaa määrittävät ominaisuudet vaikuttavat vähäisesti hankinnan läpiviemisen prosessiin kokonaisuutena, mutta oleellisesti yksittäisten tekijöiden oikeaan valikoitumiseen. Työn tuloksena muodostui helposti hahmotettavia prosessikaavioita, joita kuka tahansa hankintojen kanssa toimiva tai aiheeseen perehtyvä voi hyödyntää.Joint procurement with open procedure applying The Utilities Contracts Regulation. Abstract. The aim of the thesis is to bring together the circumstances that affect to joint procurement with open procedure applying The Utilities Contracts Regulation. In this work, features of the public procurement, selection procedure of applicable law, national and EU threshold values, impact of joint procurement as well as open procedure’s announcement and implementation process were discussed. Means of the selection procedure of applicable law and implementation processes were studied from current procurement laws and by using latest literature considering the issue. It was discovered that the circumstances that determine the procurement only affected little to the procurement procedure itself, but essentially to important individual factors and how they are determined correctly. As a result, process charts, that are easily understandable, were made to exploit by anyone who is either working among procurement or just curious about the matter

New results for the SQCD Hilbert series

We derive new explicit results for the Hilbert series of N=1 supersymmetric QCD with U(N_c) and SU(N_c) color symmetry. We use two methods which have previously been applied to similar computational problems in the analysis of decay of unstable D-branes: expansions using Schur polynomials, and the log-gas approach related to random matrix theory.Comment: 33 pages, 2 figures; v2: references and comments on the 3rd order phase transition added; v3: refs. correcte

Adaptive Development of a Regional Spatial Data Infrastructure Facing Local Prospects and Socio-Technological Trends

The regional Lounaispaikka-SDI (Spatial Data Infrastructure) in south-west Finland is being developed by a dynamic assembly of the region’s geospatial expertise and its networking, spatial data and geoportal services. Emerging as a data-centric constellation that supported the region’s geographical information professionals, this assembly has developed into a geospatial service with more broadly-focused public information on the region. This development has had five adaptive phases, each as a response to changing local needs and fast-evolving trends in information and communication technologies. Alongside these processes, the Lounaispaikka-SDI has also reinforced the region’s geospatial competencies with benefits offered to academia, public sector institutions, and companies.</p

Diversity and distribution of freshwater amphipod species in Switzerland (Crustacea: Amphipoda).

Amphipods are key organisms in many freshwater systems and contribute substantially to the diversity and functioning of macroinvertebrate communities. Furthermore, they are commonly used as bioindicators and for ecotoxicological tests. For many areas, however, diversity and distribution of amphipods is inadequately known, which limits their use in ecological and ecotoxicological studies and handicaps conservation initiatives. We studied the diversity and distribution of amphipods in Switzerland (Central Europe), covering four major drainage basins, an altitudinal gradient of>2,500 m, and various habitats (rivers, streams, lakes and groundwater). We provide the first provisional checklist and detailed information on the distribution and diversity of all amphipod species from Switzerland. In total, we found 29 amphipod species. This includes 16 native and 13 non-native species, one of the latter (Orchestia cavimana) reported here for the first time for Switzerland. The diversity is compared to neighboring countries. We specifically discuss species of the genus Niphargus, which are often receiving less attention. We also found evidence of an even higher level of hidden diversity, and the potential occurrence of further cryptic species. This diversity reflects the biogeographic past of Switzerland, and suggests that amphipods are ideally suited to address questions on endemism and adaptive radiations, post-glaciation re-colonization and invasion dynamics as well as biodiversity-ecosystem functioning relationships in aquatic systems

Agile user stories enriched with usability

Usability is a critical quality factor. Therefore, like traditional software teams, agile teams have to address usability to properly catch their users experience. There exists an interesting debate in the agile and usability communities about how to achieve this integration. Our aim is to contribute to this debate by discussing the incorporation of particular usability recommendations into user stories, one of the most popular artifacts for communicating agile requirements. In this paper, we explore the implications of usability for both the structure of and the process for defining user stories. We discuss what changes the incorporation of particular usability issues may introduce in a user story. Although our findings require more empirical validation, we think that they are a good starting point for further research on this line

On the origin of thermal string gas

We investigate decaying D-branes as the origin of the thermal string gas of string gas cosmology. We consider initial configurations of low-dimensional branes and argue that they can time evolve to thermal string gas. We find that there is a range in the weak string coupling and fast brane decay time regimes, where the initial configuration could drive the evolution of the dilaton to values, where exactly three spacelike directions grow large.Comment: 16 pages, 4 figures, v2: references adde

Winding effects on brane/anti-brane pairs

We study a brane/anti-brane configuration which is separated along a compact direction by constructing a tachyon effective action which takes into account transverse scalars. Such an action is relevant in the study of HQCD model of Sakai and Sugimoto of chiral symmetry breaking, where the size of the compact circle sets the confinement scale. Our approach is motivated by string theory orbifold constructions and gives a route to model inhomogeneous tachyon decay. We illustrate the techniques involved with a relatively simple example of a harmonic oscillator on a circle. We will then repeat the analysis for the Sakai-Sugimoto model and show that by integrating out the winding modes will provide us with a renormalized action with a lower energy than that of truncating to zero winding sector.Comment: 21 pages, 3 figures. v3: discussion and references added, published versio

Quantum Hall Effect in a Holographic Model

We consider a holographic description of a system of strongly coupled fermions in 2+1 dimensions based on a D7-brane probe in the background of D3-branes, and construct stable embeddings by turning on worldvolume fluxes. We study the system at finite temperature and charge density, and in the presence of a background magnetic field. We show that Minkowski-like embeddings that terminate above the horizon describe a family of quantum Hall states with filling fractions that are parameterized by a single discrete parameter. The quantization of the Hall conductivity is a direct consequence of the topological quantization of the fluxes. When the magnetic field is varied relative to the charge density away from these discrete filling fractions, the embeddings deform continuously into black-hole-like embeddings that enter the horizon and that describe metallic states. We also study the thermodynamics of this system and show that there is a first order phase transition at a critical temperature from the quantum Hall state to the metallic state.Comment: v2: 27 pages, 12 figures. There is a major revision in the quantitative analysis. The qualitative results and conclusions are unchanged, with one exception: we show that the quantum Hall state embeddings, which exist for discrete values of the filling fraction, deform continuously into metallic state embeddings away from these filling fraction

Holographic two dimensional QCD and Chern-Simons term

We present a holographic realization of large Nc massless QCD in two dimensions using a D2/D8 brane construction. The flavor axial anomaly is dual to a three dimensional Chern-Simons term which turns out to be of leading order, and it affects the meson spectrum and holographic renormalization in crucial ways. The massless flavor bosons that exist in the spectrum are found to decouple from the heavier mesons, in agreement with the general lore of non-Abelian bosonization. We also show that an external dynamical photon acquires a mass through the three dimensional Chern-Simons term as expected from the Schwinger mechanism. Massless two dimensional QCD at large Nc exhibits anti-vector-meson dominance due to the axial anomaly.Comment: 22 page