Quantum supergroups V. Braid group action

We construct a braid group action on quantum covering groups. We further use this action to construct a PBW basis for the positive half in finite type which is pairwise-orthogonal under the inner product. This braid group action is induced by operators on the integrable modules; however, these operators satisfy spin braid relations.Comment: v1. 31 pages v2. minor revisions, updated references, to appear in CM

Defining 'democracy': Are we staying on topic?

Political scientists' failure to pay careful attention to the content (as opposed to the operationalization) of their chosen definition of 'democracy' can make them liable to draw invalid inferences from their empirical research. With this problem in mind, we argue for the following proposition: if one wishes to conduct empirical research that contributes to an existing conversation about democracy, then one must choose a definition of 'democracy' that picks out the topic of that conversation as opposed to some other (perhaps nearby) topic of conversation. We show that, as a practical matter, one of the most effective methods for preserving "topic continuity" is to choose a definition of `democracy' that concurs with prevailing judgments about how to classify particular regimes, emphasizing the superiority (in this regard) of judgments about stylized hypothetical scenarios as opposed to judgments about the actual regimes we observe in our datasets

Optimal universal and categorical benefits with classification errors and imperfect enforcement

We determine the optimal combination of a universal benefit, B, and categorical benefit, C, for an economy in which individuals differ in both their ability to work – modelled as an exogenous zero quantity constraint on labour supply – and, conditional on being able to work, their productivity at work. C is targeted at those unable to work, and is conditioned in two dimensions: ex-ante an individual must be unable to work to be awarded the benefit , whilst ex-post a recipient must not subsequently work. However, the ex-ante conditionality may be imperfectly enforced due to Type I(false rejection) and Type II (false award) classification errors, whilst, in addition, the ex post conditionality may be imperfectly enforced. If there are no classification errors – and thus no enforcement issues – it is always optimal to set C>0, whilst B=0 only if the benefit budget is sufficiently small. However, when classification errors occur, B=0 only if there are no Type I errors and the benefit budget is sufficiently small, while the conditions under which C>0 depend on the enforcement of the ex-post conditionality. We consider two discrete alternatives. Under No Enforcement C>0 only if the test administering C has some discriminatory power. In addition, social welfare is decreasing in the propensity to make each type of error. However, under Full Enforcement C>0 for all levels of discriminatory power, including that of no discriminatory power. Furthermore, whilst social welfare is decreasing in the propensity to make Type I errors, there are certain conditions under which it is increasing in the propensity to make Type II errors. This implies that there may be conditions under which it would be welfare enhancing to lower the chosen eligibility threshold – supporting the suggestion by Goodin (1985) to “err on the side of kindness”.Postprin

Preserving The Sounds of the South

The Centre for Broadcasting History Research in the Media School at Bournemouth University, and the Wesse3x Film and Sound Archive at the Hampshire Record Office undertook a joint project to digitise audio from early commercial radio, held in the WFSA stock. This paper explores the project, which operated between 2006 and 2009

myExperiment: An ontology for e-Research

myExperiment describes itself as a "Social Virtual Research Environment" that provides the ability to share Research Objects (ROs) over a social infrastructure to facilitate actioning of research. The myExperiment Ontology is a logical representation of the data model used by this environment, allowing its data to be published in a standard RDF format, whilst providing a generic extensible framework that can be reused by similar projects. ROs are data structures designed to semantically enhance research publications by capturing and preserving the research method so that it can be reproduced in the future. This paper provides some motivation for an RO specification and briefly considers how existing domain-specifific ontologies might be integrated. It concludes by discussing the future direction of the myExperiment Ontology and how it will best support these ROs

Black Box Variational Inference

Variational inference has become a widely used method to approximate posteriors in complex latent variables models. However, deriving a variational inference algorithm generally requires significant model-specific analysis, and these efforts can hinder and deter us from quickly developing and exploring a variety of models for a problem at hand. In this paper, we present a "black box" variational inference algorithm, one that can be quickly applied to many models with little additional derivation. Our method is based on a stochastic optimization of the variational objective where the noisy gradient is computed from Monte Carlo samples from the variational distribution. We develop a number of methods to reduce the variance of the gradient, always maintaining the criterion that we want to avoid difficult model-based derivations. We evaluate our method against the corresponding black box sampling based methods. We find that our method reaches better predictive likelihoods much faster than sampling methods. Finally, we demonstrate that Black Box Variational Inference lets us easily explore a wide space of models by quickly constructing and evaluating several models of longitudinal healthcare data