The Narrow Theta(1543)--A QCD Dilemma: Tube or Not Tube?

We argue that a width of less than MeV of the new Theta resonance is inconsistent with the observed ratio of resonance and background events in the various photon initiated experiments if the latter can be described by K, K*, etc., exchange. An evaluation of the Feynman diagrams which were believed to be relevant is presented and supports the general claim in the one case where a cross section has been given by the experimental group. More detailed arguments based on the flux tube model explaining the narrow widths and the apparent conflict with the production rates are presented. We predict narrow Tetra-quarks at mass ~ O(1-1.2 GeV) which the analysis of LEAR may have missed.Comment: 9 pages, 2 figures Please note that Nussinov has previously submitted entries to the ArXives through assistance of other individuals. The submitter of this paper ([email protected]) is L. Robinette, administrative assistant to the Maryland TQHN Group; comments should be addressed to [email protected]

Diasporas and International Relations Theory

In this article, we incorporate the study of diasporas into international relations (IR) theory by focusing on diasporas as independent actors who actively influence their homeland (kin-state) foreign policies. We argue that diasporic influences can best be understood by situating them in the theoretical space shared by constructivism and liberalism; two approaches that acknowledge the impact of identity and domestic politics on international behavior. We also maintain that the exploration of diasporic activities can enrich both constructivism and liberalism. First, diasporas identity-based motivations should be an integral part of the constructivist effort to explain the formation of national identities. Second, diasporic activities and influences in their homelands expand the meaning of the term domestic politics to include not only politics inside the state but also inside the people. For the liberal approach, this is a new fact in the Lakatosian sense of the word. We theorize that the extent of diasporic influence on homeland foreign policy is determined by three components that make up the balance of power between homelands and diasporas. We then test this theory by delving into the interaction between the newly established state of Armenia and its powerful diaspora, and by comparing this case with examples taken from the relations between Israel and diaspora Jews.We would like to thank the editor and the reviewers for their detailed and insightful comments on earlier drafts of the manuscript. Andrew Benett, Aharon Kleiman, Robert Lieber, and Tamara Wittes have contributed greatly to the shaping of our arguments. Barry Bristman and Julie Weise made valuable remarks on content and style. Finally, we thank Khachig T l lyan for sharing with us his unparalleled insights into the Armenian experience.

Sparse models for Computer Vision

International audienceThe representation of images in the brain is known to be sparse. That is, as neural activity is recorded in a visual area ---for instance the primary visual cortex of primates--- only a few neurons are active at a given time with respect to the whole population. It is believed that such a property reflects the efficient match of the representation with the statistics of natural scenes. Applying such a paradigm to computer vision therefore seems a promising approach towards more biomimetic algorithms. Herein, we will describe a biologically-inspired approach to this problem. First, we will describe an unsupervised learning paradigm which is particularly adapted to the efficient coding of image patches. Then, we will outline a complete multi-scale framework ---SparseLets--- implementing a biologically inspired sparse representation of natural images. Finally, we will propose novel methods for integrating prior information into these algorithms and provide some preliminary experimental results. We will conclude by giving some perspective on applying such algorithms to computer vision. More specifically, we will propose that bio-inspired approaches may be applied to computer vision using predictive coding schemes, sparse models being one simple and efficient instance of such schemes