Towards Neural Machine Translation with Latent Tree Attention

Building models that take advantage of the hierarchical structure of language without a priori annotation is a longstanding goal in natural language processing. We introduce such a model for the task of machine translation, pairing a recurrent neural network grammar encoder with a novel attentional RNNG decoder and applying policy gradient reinforcement learning to induce unsupervised tree structures on both the source and target. When trained on character-level datasets with no explicit segmentation or parse annotation, the model learns a plausible segmentation and shallow parse, obtaining performance close to an attentional baseline.Comment: Presented at SPNLP 201

U.S. East Coast Trough Indices at 500 hPa and New England Winter Climate Variability

Using monthly gridded 500-hPa data, two synoptic indices are defined to better understand the principle mechanisms controlling intraseasonal to multiannual winter climate variability in NewEngland (NE). The “trough axis index” (TAI) is created to quantify the mean longitudinal position of the common East Coast pressure trough, and the “trough intensity index” (TII) is calculated to estimate the relative amplitude of this trough at 42.5°N. The TAI and TII are then compared with records for NE regional winter precipitation, temperature, and snowfall with the goal of understanding physical mechanisms linking NE winter climate with regional sea surface temperatures (SST), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) teleconnection pattern. The TAI correlates most significantly with winter precipitation at inland sites, such that a western (eastern)trough axis position is associated with greater (lower) average monthly precipitation. Also, significant correlations between the TAI and both NE regional SSTs and the NAO suggest that longitudinal shifting of the trough is one possible mechanism linking the North Atlantic with NE regional winterclimate variability. The NE winter temperature is significantly correlated with the TII, regional SSTs, and the NAO. While the PNA also correlates with the TII, NE winter climate variables are apparently unrelated to the PNA index

Revenge of the Realtors: The Procompetitive Case for Consolidating Multiple Listing Services

To say residential real estate is an important part of our nation\u27s economy is an understatement. Home ownership is either an asset or an aspiration for millions of Americans, and one needs only rewind the clock a decade for evidence of the financial ruin possible from buying and selling homes. But residential real estate transactions do not materialize out of thin air. Rather, the parties involved in a typical sale-buyers, sellers, agents, brokerages, online portals-all rely on critical infrastructure known as a multiple listing service (MLS) to get deals done. Simply put, an MLS is a platform that serves as a comprehensive database for information about the residential properties for sale within a specific geographic market at any given time. MLSs exist to facilitate connections between folks on opposite sides of the transaction by increasing listing exposure for sellers and by reducing search costs for buyers. While MLSs have existed for over a hundred years, they are currently undergoing a swift transformation in form, if not function. Where, as recently as fifteen years ago, there were more than one thousand MLSs across the country, there are now fewer than 650. But individual MLSs are not going away. No, they are being consolidated-merging with one another to expand territorial footprints, create operational efficiencies, and achieve the scale necessary to bargain effectively with disruptive new entrants. In our age of mega-mergers, these MLS consolidations may appear insignificant, but where there is consolidation there is the possibility of competitive harm under federal antitrust laws. Given the importance of MLSs to the market for residential real estate, any anticompetitive practices that attend a merger of MLSs could have devastating consequences. This Comment addresses that concern head-on. It contends that MLS mergers, on balance, enhance competition in the residential real estate industry and should survive the searching scrutiny of antitrust regulators