Many-site coherence revivals in the extended Bose-Hubbard model and the Gutzwiller approximation

We investigate the collapse and revival of first-order coherence in deep optical lattices when long-range interactions are turned on, and find that the first few revival peaks are strongly attenuated already for moderate values of the nearest-neighbor interaction coupling. It is shown that the conventionally employed Gutzwiller wavefunction, with only onsite-number dependence of the variational amplitudes, leads to incorrect predictions for the collapse and revival oscillations. We provide a modified variant of the Gutzwiller ansatz, reproducing the analytically calculated time dependence of first-order coherence in the limit of zero tunneling.Comment: 8+\epsilon{} pages of RevTex4-1, 4 figures; with an appendix added, has been published in Physical Review

Im2Flow: Motion Hallucination from Static Images for Action Recognition

Existing methods to recognize actions in static images take the images at their face value, learning the appearances---objects, scenes, and body poses---that distinguish each action class. However, such models are deprived of the rich dynamic structure and motions that also define human activity. We propose an approach that hallucinates the unobserved future motion implied by a single snapshot to help static-image action recognition. The key idea is to learn a prior over short-term dynamics from thousands of unlabeled videos, infer the anticipated optical flow on novel static images, and then train discriminative models that exploit both streams of information. Our main contributions are twofold. First, we devise an encoder-decoder convolutional neural network and a novel optical flow encoding that can translate a static image into an accurate flow map. Second, we show the power of hallucinated flow for recognition, successfully transferring the learned motion into a standard two-stream network for activity recognition. On seven datasets, we demonstrate the power of the approach. It not only achieves state-of-the-art accuracy for dense optical flow prediction, but also consistently enhances recognition of actions and dynamic scenes.Comment: Published in CVPR 2018, project page: http://vision.cs.utexas.edu/projects/im2flow

Disentangling the Demand-enhancing Effect and Trade-cost Effect of Technical Measures in Agricultural Trade among OECD countries

Domestic technical measures such as SPS and TBTs can enhance import demand via information disclosure and quality improvement, or hamper foreign export supply via imposing sizeable compliance costs, or both. The traditional gravity equation model estimates the net effect of these measures on international trade with a loss of useful inference on separate effects. We stipulate a generalized gravity equation model to disentangle the two effects. We apply the augmented approach to agricultural trade among OECD countries in 2004. We find that technical measures in agriculture often jointly enhance import demand and hinder export supply with the net effect of promoting the propensity to trade. Further disaggregated data analysis reveals heterogeneity across sectors in terms of net effects of technical measures, despite common demand-enhancing and supply-hindering effects. These measures in the net decrease the probability of intra-OECD trade in dairy products, whereas they increase that of intra-OECD trade in cereal preparations.sanitary and phytosanitary, SPS, technical measures, NTM, TBT, standards, gravity equation, protectionism, OECD, International Relations/Trade,

Does European Aflatoxin Regulation Hurt Groundnut Exporters from Africa?

We provide an ex-post econometric examination of the harmonization and tightening of the EU Maximum Residues Limit (MRL) on aflatoxins in 2002, and its impact on African exports of groundnut products. We show that the MRL set by the EU has no significant trade impact on groundnut exports from Africa across various methods of estimation. African domestic supply plays an important role in the determination of the volumes of trade and the propensity to trade. Our findings suggest that the trade potential of African groundnut exporters is more constrained by domestic supply issues rather than by limited market access.food safety; standards; aflatoxin; MRL; groundnut; Africa; EU; market access

Aflatoxin Redux: Does European Aflatoxin Regulation Hurt Groundnut Exporters from Africa?

Replaced with revised version of paper 07/02/10.food safety, standards, aflatoxin, Maximum Residues Limit, groundnut, gravity equation, Africa, market access, EU, Agricultural and Food Policy, Community/Rural/Urban Development, Crop Production/Industries, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Development, International Relations/Trade, Q17, F13,