Ergodic Effects in Token Circulation

International audienceWe consider a dynamical process in a network which distributes all particles (tokens) located at a node among its neighbors, in a round-robin manner.We show that in the recurrent state of this dynamics (i.e., disregarding a polynomially long initialization phase of the system), the number of particles located on a given edge, averaged over an interval of time, is tightly concentrated around the average particle density in the system. Formally, for a system of $k$ particles in a graph of $m$ edges, during any interval of length $T$, this time-averaged value is $k/m \pm \widetilde O(1/T)$, whenever $gcd(m,k) = \widetilde O(1)$ (and so, e.g., whenever $m$ is a prime number). To achieve these bounds, we link the behavior of the studied dynamics to ergodic properties of traversals based on Eulerian circuits on a symmetric directed graph. These results are proved through sum set methods and are likely to be of independent interest.As a corollary, we also obtain bounds on the \emph{idleness} of the studied dynamics, i.e., on the longest possible time between two consecutive appearances of a token on an edge, taken over all edges. Designing trajectories for $k$ tokens in a way which minimizes idleness is fundamental to the study of the patrolling problem in networks. Our results immediately imply a bound of $\widetilde O(m/k)$ on the idleness of the studied process, showing that it is a distributed $\widetilde O(1)$-competitive solution to the patrolling task, for all of the covered cases. Our work also provides some further insights that may be interesting in load-balancing applications

Semiclassical theory of weak antilocalization and spin relaxation in ballistic quantum dots

We develop a semiclassical theory for spin-dependent quantum transport in ballistic quantum dots. The theory is based on the semiclassical Landauer formula, that we generalize to include spin-orbit and Zeeman interaction. Within this approach, the orbital degrees of freedom are treated semiclassically, while the spin dynamics is computed quantum mechanically. Employing this method, we calculate the quantum correction to the conductance in quantum dots with Rashba and Dresselhaus spin-orbit interaction. We find a strong sensitivity of the quantum correction to the underlying classical dynamics of the system. In particular, a suppression of weak antilocalization in integrable systems is observed. These results are attributed to the qualitatively different types of spin relaxation in integrable and chaotic quantum cavities.Comment: 20 page

The riskiness of corporate bonds

When the riskiness of an asset increases, then, arguably, some risk-averse agents that were previously willing to hold on to the asset are no longer willing to do so. Aumann and Serrano (2008) have recently proposed an index of riskiness that helps to make this intuition rigorous. We use their index to analyze the riskiness of corporate bonds and how this can change over time and across rating classes and how it compares to the riskiness of other financial instruments. We find statistically significant evidence that a number of financial and macroeconomic variables can predict time-variation in the riskiness of corporate bonds, including in ways one might not expect. For example, a higher yield-to-maturity lowers riskiness by reducing the frequency and the magnitude of negative holding-period returns.riskiness, corporate bonds, predictability

Translation as Experimentalism

This Element argues for a perspective on literary translation based around ludification, using concrete poetry as a test case. It questions assumptions about translatability and opens up the discursive space of literary writing to transgressive articulation and multimodal performance. This title is also available as Open Access on Cambridge Core

New Game Plus: A Study of Video Game Narratives

New Game Plus: A Study of Video Game Narratives is a scholarly thesis that examines three dominant narrative forms in video games, namely, linear, branching, and rhizomatic. These narrative forms help contextualize this study’s consideration of the history of video games which reveals the increasing sophistication of the medium as a form of storytelling. This thesis examines two different video games in each of the three categories and traces how more recent video games tend to use player interactivity to explore and reflect players’ morality. Common threads in the examined video games include moral dilemmas, socio-political issues, remediations of earlier narrative forms, game mechanics, and the effects of player agency on video game narratives

Innovation driven sectoral shocks and aggregate city cycles

This paper formalizes one mechanism through which diversification in the production of research & development across firms located in a city dampens volatility in the local labor market, improves the incentives to perform research & development and smooths the aggregate business cycle fluctuations of a city. This is done by adapting the standard multi-sector quality ladder model (Grossman and Helpman 1991) in order to allow for heterogeneity across firms, thus taking into account knowledge spillovers across heterogenous sectors, knowledge accumulation, pecuniary externalities and segmented labor markets. As a result, according to the local degree of diversification in research & development, sectoral technological shocks have an influence on the current choice of research & development and the location of production, and in turn on local business cycles and the life cycle of the city: diversification in research & development allows innovations in different sectors of the city to arrive at different points in time, thus avoiding to put pressure on the local labor markets and keeping wage discipline. This permits firms located in the city to perform enough research & development and possibly beat outside competition in discovering and manufacturing new products, thus growing -at the aggregate city level-through less volatile cycles.quality ladder with heterogeneity across firms, labor pooling economies, knowledge spillovers, diversification, schumpeterian growth in the city

Remote sensing of floe size distribution and surface topography

Floe size can be measured by several properties p- for instance, area or mean caliper diameter. Two definitions of floe size distribution seem particularly useful. F(p), the fraction of area covered by floes no smaller than p; and N(p), the number of floes per unit area no smaller than p. Several summertime distributions measured are a graph, their slopes range from -1.7 to -2.5. The variance of an estimate is also calculated