4,568 research outputs found
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
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
- …