On sign changes of cusp forms and the halting of an algorithm to construct a supersingular elliptic curve with a given endomorphism ring

Chevyrev and Galbraith recently devised an algorithm which inputs a maximal order of the quaternion algebra ramified at one prime and infinity and constructs a supersingular elliptic curve whose endomorphism ring is precisely this maximal order. They proved that their algorithm is correct whenever it halts, but did not show that it always terminates. They did however prove that the algorithm halts under a reasonable assumption which they conjectured to be true. It is the purpose of this paper to verify their conjecture and in turn prove that their algorithm always halts. More precisely, Chevyrev and Galbraith investigated the theta series associated with the norm maps from primitive elements of two maximal orders. They conjectured that if one of these theta series "dominated" the other in the sense that the $n$th (Fourier) coefficient of one was always larger than or equal to the $n$th coefficient of the other, then the maximal orders are actually the same. We prove that this is the case.Comment: 12 page

The Effect of Exchange Rate Movements on Heterogeneous Plants: A Quantile Regression Analysis

In this paper, we examine how the effect of movements in the real exchange rate on manufacturing plants depends on the plant’s placement within the productivity distribution. Appreciations of the local currency expose domestic plants to more competition from abroad as export opportunities shrink and import competition intensifies. As a result, smaller less productive plants are forced from the market, which truncates the lower end of the productivity distribution. For surviving plants, appreciations can lead to a reduction in plant size, which, in the presence of scale economies, can lower productivity. We examine these mechanisms using quantile regression, which allows for the study of the conditional distribution of industry productivity. Using plant-level data that covers the entire Canadian manufacturing sector from 1984 to 1997, we find that many industries exhibit a downward sloping quantile regression curve, meaning that movements in the exchange rate do, indeed, have distributional effects on productivity.Productivity; Exchange rates; Market structure and pricing

Modelling Financial Channels for Monetary Policy Analysis

The Bank of Canada considers a wide range of information and analysis before making a monetary policy decision and uses carefully articulated models to produce economic projections and to examine alternative scenarios. This article describes an ongoing research agenda at the Bank to develop models in which financial variables play an active role in the transmission of monetary policy actions to economic activity. Such models can help to analyze information from the financial side of the economy and to provide an overall view of the implications of financial developments for the current economic outlook. The authors also explain how this research can help address other issues relevant to the objectives of monetary policy, including how asset-price movements should be taken into account in the monetary policy framework.

SUSTAINABILITYAND GROWTH OFONLINE KNOWLEDGE COMMUNITIES: EXAMINING THE IMPORTANCE OFPERCEIVED COMMUNITYSUPPORTAND PERCEIVED LEADER SUPPORT

Voluntary behaviors (i.e., knowledge contribution and word of mouth) are important to the sustainability and growth of online knowledge communities. Although previous studies have identified various factors leading to knowledge contribution and related behaviors, the underlying psychological processes have rarely been examined. In particular, previous studies have not examined how characteristics of online knowledge communities influence voluntary behaviors through support perception. This study aims to fill the gap in the literature by developing and testing a model to explain voluntary behaviors in online knowledge communities. To develop the research model, we drew on theories of justice, organizational support, and citizenship behavior to explain the influence of characteristics of online knowledge communities on individuals\u27 voluntary behaviors through their perceptions of support from the community and the leader. The research model was tested on survey data collected from 214 online knowledge community users. The results largely supported our model. In particular, we found that pro-sharing norm and information need fulfillment affect perceived community support. Perceived recognition from leader and perceived co-presence of leader affect perceived leader support. Additionally, perceived community support was found to be important in shaping knowledge contribution and word of mouth. Perceived leader support was found to influence individuals\u27 knowledge contribution behavior. Theoretical and Practical implications are discussed

Tell me, show me, involve me: Supercharging Collaborative Diagnosis with Augmented Reality

Augmented reality has been broadly employed to help remote individuals communicate and coordinate. In this study, we develop and test a model that explains how augmented reality can facilitate collaborative diagnosis on an unexpected technical breakdown involving two complete strangers. Drawing on the affordance theory, we integrate the dual-task interference literature to reveal frustration valence and arousal as the underlying mechanisms. We tested our hypothesis in a laboratory experiment involving a custom-built augmented reality environment and physiological measurements. Overall, this study contributes to information system literature, human-computer interaction literature, and dual-task interference research by unearthing the effects of augmented reality characteristics on enhancing collaborative diagnosis performance

Swimming, Feeding and Inversion of Multicellular Choanoflagellate Sheets

The recent discovery of the striking sheet-like multicellular choanoflagellate species $Choanoeca~flexa$ that dynamically interconverts between two hemispherical forms of opposite orientation raises fundamental questions in cell and evolutionary biology, as choanoflagellates are the closest living relatives of animals. It similarly motivates questions in fluid and solid mechanics concerning the differential swimming speeds in the two states and the mechanism of curvature inversion triggered by changes in the geometry of microvilli emanating from each cell. Here we develop fluid dynamical and mechanical models to address these observations and show that they capture the main features of the swimming, feeding, and inversion of $C.~flexa$ colonies.Comment: 5 pages, 3 figures + Supplementary Material (videos on request from REG

Quantum key distribution with delayed privacy amplification and its application to security proof of a two-way deterministic protocol

Privacy amplification (PA) is an essential post-processing step in quantum key distribution (QKD) for removing any information an eavesdropper may have on the final secret key. In this paper, we consider delaying PA of the final key after its use in one-time pad encryption and prove its security. We prove that the security and the key generation rate are not affected by delaying PA. Delaying PA has two applications: it serves as a tool for significantly simplifying the security proof of QKD with a two-way quantum channel, and also it is useful in QKD networks with trusted relays. To illustrate the power of the delayed PA idea, we use it to prove the security of a qubit-based two-way deterministic QKD protocol which uses four states and four encoding operations.Comment: 11 pages, 3 figure