Improved Maximum Entropy Analysis with an Extended Search Space

The standard implementation of the Maximum Entropy Method (MEM) follows Bryan and deploys a Singular Value Decomposition (SVD) to limit the dimensionality of the underlying solution space apriori. Here we present arguments based on the shape of the SVD basis functions and numerical evidence from a mock data analysis, which show that the correct Bayesian solution is not in general recovered with this approach. As a remedy we propose to extend the search basis systematically, which will eventually recover the full solution space and the correct solution. In order to adequately approach problems where an exponentially damped kernel is used, we provide an open-source implementation, using the C/C++ language that utilizes high precision arithmetic adjustable at run-time. The LBFGS algorithm is included in the code in order to attack problems without the need to resort to a particular search space restriction.Comment: 18 pages, 6 figures, v3 includes several changes in text and figures, t.b.p. in Journal of Computational Physics, source code at http://www.scicode.org/ExtME

The VIA Annotation Software for Images, Audio and Video

In this paper, we introduce a simple and standalone manual annotation tool for images, audio and video: the VGG Image Annotator (VIA). This is a light weight, standalone and offline software package that does not require any installation or setup and runs solely in a web browser. The VIA software allows human annotators to define and describe spatial regions in images or video frames, and temporal segments in audio or video. These manual annotations can be exported to plain text data formats such as JSON and CSV and therefore are amenable to further processing by other software tools. VIA also supports collaborative annotation of a large dataset by a group of human annotators. The BSD open source license of this software allows it to be used in any academic project or commercial application.Comment: to appear in Proceedings of the 27th ACM International Conference on Multimedia (MM '19), October 21-25, 2019, Nice, France. ACM, New York, NY, USA, 4 page

Digital Piracy: Neutralising Piracy on the Digital Waves

Rates of digital piracy, defined by Gopal, et al. (2004: 3) as ‘the illegal act of copying digital goods for any reason other than backup, without permission from or compensation to the copyright holder’, appear to be rising despite increasingly stringent methods employed by both legislators and the industries affected to curtail it. The harm it causes the industries is also increasing; affecting everyone from producers to consumers. This study explores the aetiology of digital piracy; specifically whether students in the United Kingdom neutralise the guilt for their actions through the use of Sykes and Matza’s (1957) techniques of neutralisation. Through the data collected from an online survey (n=114) this study finds that students typically neutralise their guilt when committing piracy through an ‘appeal to higher loyalties’ and a belief that ‘everyone else does it’. The use of these specific techniques implies that piracy has become a social norm for students at university who do not see it as morally wrong. The study concludes by suggesting the policy implications of these findings and potential avenues for further research

Dracula and the Gothic Imagination of War

When Jonathan Harker first describes Castle Dracula, his journals rely on the language of war. Unable to pin down the castle’s site on an Ordnance Map, Harker is able to see instead the liminal city of Bistritz in terms of a historic siege (11). As he approaches nearer, Harker relates a companion’s (mis)quotation from Burger’s “Lenore,” a line spoken by an undead soldier, all too recently at war (17). Castle Dracula itself appears textually as a mix of military and Gothic discourses, whose “frowning walls and dark window openings” (21) serve both to situate Harker in classically Gothic space, and to describe a tactical situation “where sling, or bow, or culverin could not reach” (40). When the novel subsequently shifts ground to London, Carfax similarly appears in this dual role as Gothic and military edifice. Once “Quatre Face,” the now-estate contains massive and unbroken walls, a fine internal spring (for preserving fresh water during sieges), well-situated windows, few neighbors, and a difficult entry (28-29). As a Gothic site, Carfax becomes a typical architecture of terror, containing spatially organized secrets and suspense. Between these two architectural foci, these synecdoches of the Gothic and war, swings the balance of the novel’s plot and much of its conceptual structure, formally anchoring Dracula’s expedition and its retreat. My argument is twofold. First, Dracula draws on the Gothic genre’s persistent engagement with military discourse; second, that the novel’s representation of fortifications grounds and organizes a series of social and political issues. I will begin by sketching the military aspects of the Gothic antecedent to Stoker, then proceed to the novel, with a final glance towards the twentieth and twenty-first centuries

Testing Asymmetric-Information Asset Pricing Models

We test models of asset pricing under asymmetric information using plausibly exogenous variation in the supply of information caused by the closure or restructuring of brokerage firms’ research operations. Consistent with predictions derived from a Grossman and Stiglitz-type model, share prices and uninformed investors’ demands fall as information asymmetry increases. Cross-sectional tests support the comparative statics. Prices and uninformed demand experience larger declines, the more investors are uninformed, the larger and more variable is turnover, the more uncertain is the asset’s payoff, and the noisier is the better-informed investors’ signal. We show that prices fall because expected returns become more sensitive to a liquidity-risk factor

The Value of Research

We estimate the value added by sell-side equity research analysts and explore the links between analyst research, informational efficiency, and asset prices. We identify the value of research from exogenous changes in analyst coverage. On announcement that a stock has lost all coverage, share prices fall by around 110 basis points or $8.4 million on average. The share price reaction is attenuated the more analysts continue to cover the stock, suggesting that there are diminishing returns to coverage at the margin. The adverse effect of coverage terminations is proportional to the analyst’s reputation and experience and to the size of the broker’s retail sales force. Exogenous reductions in coverage are followed by: less efficient pricing and lower liquidity; greater earnings surprises and more volatile trading around subsequent earnings announcements; increases in required returns; and reduced return volatility. Simulations suggest investors can trade profitably on the volatility changes. Finally, retail investors sell and large institutional investors buy around coverage terminations, suggesting that different investor clienteles have different demands for analyst research

The Power of Poincar\'e: Elucidating the Hidden Symmetries in Focal Conic Domains

Focal conic domains are typically the "smoking gun" by which smectic liquid crystalline phases are identified. The geometry of the equally-spaced smectic layers is highly generic but, at the same time, difficult to work with. In this Letter we develop an approach to the study of focal sets in smectics which exploits a hidden Poincar\'e symmetry revealed only by viewing the smectic layers as projections from one-higher dimension. We use this perspective to shed light upon several classic focal conic textures, including the concentric cyclides of Dupin, polygonal textures and tilt-grain boundaries.Comment: 4 pages, 3 included figure

Testing Asymmetric-Information Asset Pricing Models

Theoretical asset pricing models routinely assume that investors have heterogeneous information. We provide direct evidence of the importance of information asymmetry for asset prices and investor demands using plausibly exogenous variation in the supply of information caused by the closure of 43 brokerage firms' research operations in the U.S. Consistent with predictions derived from a Grossman and Stiglitz-type model, share prices and uninformed investors' demands fall as information asymmetry increases. Cross-sectional tests support the comparative statics: Prices and uninformed demand experience larger declines, the more investors are uninformed, the larger and more variable is stock turnover, the more uncertain is the asset's payoff, and the noisier is the better-informed investors' signal. We show that at least part of the fall in prices is due to expected returns becoming more sensitive to liquidity risk. Our results imply that information asymmetry has a substantial effect on asset prices and that a primary channel linking asymmetry to prices is liquidity