Finite temperature phase transition, adjoint Polyakov loop and topology in SU(2) LGT

We investigate the phase structure of pure SU(2) LGT at finite temperature in the mixed fundamental and adjoint representation modified with a Z2 monopole chemical potential. The decoupling of the finite temperature phase transition from unphysical zero temperature bulk phase transitions is analyzed with special emphasis on the continuum limit. The possible relation of the adjoint Polyakov loop to an order parameter for the finite temperature phase transition and to the topological structure of the theory is discussed.Comment: 3 pages, 3 figures LaTeX file. Uses espcrc2 style and amssymb package. Talk given at Lattice2001, Berli

Two-loop critical mass for Wilson fermions

We have redone a recent two-loop computation of the critical mass for Wilson fermions in lattice QCD by evaluating Feynman integrals with the coordinate-space method. We present the results for different types of infrared regularization. We confirm both the previous numerical estimates and the power of the coordinate-space method whenever high accuracy is needed.Comment: 13 LaTeX2e pages, 2 ps figures include

Explicit characterization of the identity configuration in an Abelian Sandpile Model

Since the work of Creutz, identifying the group identities for the Abelian Sandpile Model (ASM) on a given lattice is a puzzling issue: on rectangular portions of Z^2 complex quasi-self-similar structures arise. We study the ASM on the square lattice, in different geometries, and a variant with directed edges. Cylinders, through their extra symmetry, allow an easy determination of the identity, which is a homogeneous function. The directed variant on square geometry shows a remarkable exact structure, asymptotically self-similar.Comment: 11 pages, 8 figure

New Universality Classes for Two-Dimensional σ\sigma-Models

We argue that the two-dimensional $O(N)$-invariant lattice $\sigma$-model with mixed isovector/isotensor action has a one-parameter family of nontrivial continuum limits, only one of which is the continuum $\sigma$-model constructed by conventional perturbation theory. We test the proposed scenario with a high-precision Monte Carlo simulation for $N=3,4$ on lattices up to $512 \times 512$, using a Wolff-type embedding algorithm. [CPU time $\approx$ 7 years IBM RS-6000/320H] The finite-size-scaling data confirm the existence of the predicted new family of continuum limits. In particular, the $RP^{N-1}$ and $N$-vector models do not lie in the same universality class.Comment: 10 pages (includes 2 figures), 211176 bytes Postscript, NYU-TH-93/07/03, IFUP-TH 34/9

Multi-Grid Monte Carlo via XYXY Embedding. II. Two-Dimensional SU(3)SU(3) Principal Chiral Model

We carry out a high-precision simulation of the two-dimensional $SU(3)$ principal chiral model at correlation lengths $\xi$ up to $\sim 4 \times 10^5$, using a multi-grid Monte Carlo (MGMC) algorithm and approximately one year of Cray C-90 CPU time. We extrapolate the finite-volume Monte Carlo data to infinite volume using finite-size-scaling theory, and we discuss carefully the systematic and statistical errors in this extrapolation. We then compare the extrapolated data to the renormalization-group predictions. The deviation from asymptotic scaling, which is $\approx 12$ at $\xi \sim 25$, decreases to $\approx 2$ at $\xi \sim 4 \times 10^5$. We also analyze the dynamic critical behavior of the MGMC algorithm using lattices up to $256 \times 256$, finding the dynamic critical exponent $z_{int,{\cal M}^2} \approx 0.45 \pm 0.02$ (subjective 68% confidence interval). Thus, for this asymptotically free model, critical slowing-down is greatly reduced compared to local algorithms, but not completely eliminated.Comment: self-unpacking archive including .tex, .sty and .ps files; 126 pages including all figure

Polarity, cell division, and out-of-equilibrium dynamics control the growth of epithelial structures

The growth of a well-formed epithelial structure is governed by mechanical constraints, cellular apico-basal polarity, and spatially controlled cell division. Here we compared the predictions of a mathematical model of epithelial growth with the morphological analysis of 3D epithelial structures. In both in vitro cyst models and in developing epithelial structures in vivo, epithelial growth could take place close to or far from mechanical equilibrium, and was determined by the hierarchy of time-scales of cell division, cell-cell rearrangements, and lumen dynamics. Equilibrium properties could be inferred by the analysis of cell-cell contact topologies, and the nonequilibrium phenotype was altered by inhibiting ROCK activity. The occurrence of an aberrant multilumen phenotype was linked to fast nonequilibrium growth, even when geometric control of cell division was correctly enforced. We predicted and verified experimentally that slowing down cell division partially rescued a multilumen phenotype induced by altered polarity. These results improve our understanding of the development of epithelial organs and, ultimately, of carcinogenesi

Conceptual export and theory mobilities: exploring the reception and development of the “creative city thesis” in the post-socialist urban realm

This paper addresses the limited contribution of scholarship from within/on the post-socialist urban arena to global urban studies, a phenomenon attributed to the influence of a hegemonic Anglo-American academic complex. We seek to present a more nuanced account by considering scholarship on the “creative city” in a post-socialist context. A numerical analysis of English language publications confirms the lack of impact of scholarship from/on post-socialist areas, though we do identify literature which may be “theory exporting” and emphasize the temporal dimension of the development of scholarship. We then consider the interaction of three global mobilities to present a more nuanced account of this pattern – the “creative city” thesis as globally mobile urban policy, the neoliberalization of universities as a globally mobile restructuring of the context in which these inequalities in knowledge-production are produced, and urban studies theorizing itself as a set of globally mobile concepts and practices. We therefore explore the dynamic interaction of a particular urban phenomenon (“creative city” policy) with academic knowledge production. Adopting this perspective allows us to emphasize other factors such as path dependencies within post-socialist areas and to give due emphasis to agency within the region and how these interact with global processes of neoliberalizing academia

Twisted mass lattice QCD

I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed.Comment: v2. 143 pages, 28 figures. Sect. 2 now split in two sections. Several improvements for better readability. Typos corrected. Added 2 figures. Added references. Clarifications on few points. Conclusions and results unchanged. Version published on Physics Repor

Swop projects

Swop Projects (2003–2007) was a long-term art and research project that functioned as a platform for the production and dissemination of material and ideas dealing with contemporary political, economic and social debate.   We initiated the project as an attempt to cross national and academic boundaries and collect a variety of voices and opinions with the intention of visualizing models that linked economic and environmental concerns. Together with professionals with a similar focus we wanted to analyse inequalities regarding the uneven access to power, to global flows of resources and information and to explore models that challenge these conditions. We initiated a dialogue on informal economies and systems based on open source and participatory thinking in a space we occupied at the time – a storefront at Frederiksberg, Copenhagen. The programme comprised a series of open talks and discussions featuring artists, economists and activists. As a result of these encounters, we established a research archive at our premises and online that contained interviews with the people we had met, i.e. groups and individuals whose work is based on ideas of generosity, local currencies and ways of organising sustainable systems. Swop Projects has since developed into a number of initiatives that include an experimental alternative exchange currency in the Hidden Flow Exchange Project; the distribution of the free newspaper Gratis; the Give Away Shop, which highlights gift economies; and Give Away in Circulation, a project that collects and disseminates ideas about circulation and open source systems. The Swop Archive continued to develop throughout the Swop Projects period. It now consists of interviews made in various contexts, some excerpts of which are reproduced in this book. The projects are presented in a chronological order, starting with a number of works that became the starting point of Swop Projects and that were carried out prior to the launch. Several of the projects are concerned with a reaction to the fact that the public sphere, perceived as an open arena for cultural exchange, is shrinking. The attempts that have been made over the last few years to transform cultural products into “private property” cannot only be associated with the material dimensions of public spaces; cultural products can easily be exchanged and distributed via the Internet. Paradoxically, these possibilities have been made more difficult due to increased regulation and copyright control. Our work with Swop Projects reflects an interest in developing non-commercial methods for the distribution of goods and services and the exchange of information. In line with the project’s notions on Open Source and of recycling, we also chose to reproduce texts that were previously published within the scope of the project. The objective of this book is to present Swop Projects and some of the initiatives and projects we conducted within this framework. Apart from the material, documentation and concrete output, the book also includes three texts commissioned from authors to give an idea of the contexts in which the various projects operated. As a backdrop, we chose to include a text by writer and researcher Kolya Abramsky, which outlines the political and economical climate. We asked Emily Pethick, director of CASCO at the time, to contribute a text on how to build relationships around an art institution by collaborating with artists. We also asked freelance curator Katarina Stenbeck to contextualize the project from a contemporary art perspective. To us, the work of developing alternative strategies and micro-models is a collective effort involving individuals from various groups and local communities. In order to understand local contexts and, not least, to be able to imagine alternative destinations, we have operated within an international network. We started in Copenhagen and around Denmark. The project then brought us further afield to cities in Europe and beyond. We met people and visited local communities whose relationship to contemporary culture is based on ideas of co-operation, collectivism and social diversity in the local environment. During the years we spent on Swop Projects we learned a lot, both personally and professionally, through meeting people who inspired us, presented us with ideas and who generously shared their knowledge and experience. We hope that we, through this book, can communicate the views of a political and artistic sphere as well as share some of the critical and diverse ideas that we have had the privilege to come across during the course of our work. We hope to inspire others and to arouse the readers’ curiosity in the same way as our own curiosity was kindled