17,464 research outputs found
Coarse coherence of metric spaces and groups and its permanence properties
We introduce properties of metric spaces and, specifically, finitely
generated groups with word metrics which we call coarse coherence and coarse
regular coherence. They are geometric counterparts of the classical algebraic
notion of coherence and the regular coherence property of groups defined and
studied by F. Waldhausen. The new properties can be defined in the general
context of coarse metric geometry and are coarse invariants. In particular,
they are quasi-isometry invariants of spaces and groups. We show that coarse
regular coherence implies weak regular coherence, a weakening of regular
coherence by G. Carlsson and the first author. The latter was introduced with
the same goal as Waldhausen's, in order to perform computations of algebraic
K-theory of group rings. However, all groups known to be weakly regular
coherent are also coarsely regular coherent. The new framework allows us to
prove structural results by developing permanence properties, including the
particularly important fibering permanence property, for coarse regular
coherence.Comment: 11 page
The Senate and Supreme Court Nominations: Some Reflections
Sammanfattning Vad Ă€r en transformation, och vad den kan vara? Hur kan en strategi för hur man kan förhĂ„lla sig till transformationsprojekt se ut? Jag har definierat det som att en transformation handlar om att ta en befintlig byggnad och införa ett nytt program som skapar en ny verklighet. Det kan finnas flera anledningar till att göra en transformation istĂ€llet för att bygga nytt. Den viktigaste anledningen som jag har valt att arbeta med handlar om att fĂ„nga upp de vĂ€rden som finns i en byggnad och fĂ„ med sig dem och bygga vidare pĂ„ dem istĂ€llet för att skapa helt andra vĂ€rden. VĂ€rden Ă€r saker som yta, volym, rumshöjd, ljusförhĂ„llanden, material och detaljer. Det Ă€r saker som de gjutna betongtrapporna och de speciella fönsterpartierna i byggnaden. För mig Ă€r det detta som Ă€r sjĂ€lva idĂ©n och meningen med en transformation. För vĂ€rdena som bevaras knyter an till historien och bĂ€r och bevarar minnen och identiteter. De skapar en kontinuitet i byggnadens berĂ€ttelse. I en transformation uppkommer en mĂ€ngd stora konflikter eftersom det nya programmet efterfrĂ„gar vĂ€rden som byggnaden saknar. Hur man vĂ€ljer att lösa dessa konflikter Ă€r det mest kritiska och svĂ„raste i en transformation. Jag gör transformationen i tvĂ„ steg. Det första steget gĂ„r ut pĂ„ att definiera sĂ„ mycket vĂ€rden som möjligt och försöka fĂ„ med dem in i det nya programmet samtidigt som jag bortser nĂ„got frĂ„n helheten. Boendena fanns dĂ€r sedan tidigare, för mig handlade det bara om att isolera vĂ€rdena och föra med dem in i det nya programmet. Jag har behĂ„llit sĂ„ mycket av det befintliga som möjligt för att hĂ„lla vĂ€rdena intakta och bara lagt till vĂ€ggar för att avgrĂ€nsa lĂ€genheterna. Det jag dĂ„ fĂ„r Ă€r vĂ€ldigt speciella boenden, mĂ„nga har egna ingĂ„ngar, breder ut sig i tvĂ„ plan och har ljusinslĂ€pp frĂ„n tvĂ„ hĂ„ll. Det hĂ€r Ă€r ett sĂ€kert och relativt enkelt sĂ€tt att bevara vĂ€rden. NĂ€r dessa bevarade boenden Ă€r definierade uppkommer de svĂ„ra konflikterna som ocksĂ„ gör transformationen sĂ„ pass intressant. Ytorna som Ă€r kvar efter att jag lagt ut dessa behĂ„llna boenden Ă€r svĂ„ra att skapa bra boenden ifrĂ„n. Jag tror att det Ă€r viktigt att tillĂ€ggen som mĂ„ste till i en transformation anknyter till byggnaden som var. Annars Ă€r risken stor att vĂ€rdena som fanns förstörs. Anknytning handlar för mig om att det nya tar upp saker som rumsliga koncept, formmĂ€ssiga, materialmĂ€ssiga eller strukturella koncept. InnergĂ„rdarna som finns dĂ€r idag anvĂ€nds dĂ„ligt. Egentligen Ă€r innergĂ„rdar nĂ„got fantastiskt. De drar inte bara in solljus utan Ă€ven skugga, regn, snö, ljud, vĂ€xtlighet, insekter och fĂ„glar djupt in i en byggnadsvolym. DĂ€rför har jag valt att utveckla de innergĂ„rdar som redan finns genom att lĂ€gga till nĂ„gra fler. I och runt kring skolan finns ocksĂ„ flera platsgjutna betongtrappor. För att skapa förbindelser har jag lagt till nya liknande trappor. En bra transformation skapar förutsĂ€ttningar för ett nytt behov samtidigt som den behĂ„ller de viktigaste vĂ€rdena i en byggnad och bygger vidare pĂ„ identiteten istĂ€llet för att förstöra den. Min strategi för transformationer i tvĂ„ steg handlar om att först fĂ„ med sig vissa speciella vĂ€rden in i ett nytt program utan att ta hĂ€nsyn till byggnaden som helhet. DĂ€refter skapas ett tillĂ€gg som relaterar till det befintliga men samtidigt löser de konflikter som alltid uppkommer vid en transformation. Resultatet i det hĂ€r fallet Ă€r boenden som Ă€r vĂ€ldigt speciella jĂ€mfört med boenden som normalt byggs idag. Det Ă€r inga typlĂ€genheter utan boendena som skapas har ytor, volymer, detaljer och andra egenskaper som nybyggda boenden sĂ€llan har.  Abstract What is a transformation, and what could it be? How could a strategy for how to approach a transformation project look? I have defined a transformation as the act of taking an existing building and inserting a new program that creates a new reality. There can be many reasons to do a transformation instead of building something new. The most important reason that I have chosen to work with is about capturing the qualities or values that exists in a building and bring them into the new reality and build on them instead of creating whole different values. Values in this case are things like surface area, volumes, height, light conditions, material and details. It is things like the cast concrete stairs and the very special windows in some parts of the building. To me this is the core idea and purpose of any transformation. Because the values that are kept ties the present to the history, and carries and keeps memories and identities. They create continuity in the story of the building. In a transformation a number of mayor conflicts arise because the new program demands values that the existing building lacks. How you chose to solve these conflicts is the most critical and most difficult aspect of any transformation. My transformation is done two steps. The first step is about identifying as much values as possible and trying to bring them into the new program while overlooking the whole. The dwelling was there already, all I had to do was isolate the values and bring them in to the new program. I have kept as much of the existing material as possible to keep the values intact and only added walls to define the new apartments. The result is very particular dwellings; a lot of them have their own entrances, they are spreading out both horizontally and vertically and have sunlight from two directions. This is a safe and rather easy way of keeping values. When these kept dwellings are defined the more difficult conflicts arises that makes the transformation so interesting. The surface areas that remain after I have laid out these kept dwellings are hard to create good dwellings from. I think itâs important that the additions that has to be made in a transformation relates to the building that used to be. Otherwise thereÂŽs a great risk that the existing values are destroyed. Relation for me is about picking up things like spatial concepts and concepts relating to form, material or structure. The courtyards that exist today are rarely in use. Courtyards are actually something amazing. They donât only retract sunlight but also shadow, rain, snow, sounds, foliage, bugs and birds deep into a building. Therefore I have chosen to develop the courtyards that already exists by adding some more. In and around the school there are also several stairs in cast concrete. To create connections Iâve added new similar stairs.  A good transformation creates the conditions needed for a new demand, while keeping the most important values in a building and adds to the identity instead of destroying it.  My strategy for transformations in two steps is about first bringing certain special values into a new program without considering the building as a whole. Afterwards an addition is created which relates to the existing while solving the conflicts that always arise when doing a transformation. The result in this case is dwellings that are very particular compared to the dwellings which are usually built today. They are not standard flats but dwellings with surface areas, volumes, details and other characteristics that newly built dwellings rarely has
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