4,641 research outputs found

    Loop corrections and a new test of inflation

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    Inflation is the leading paradigm for explaining the origin of primordial density perturbations and the observed temperature fluctuations of the cosmic microwave background. However many open questions remain, in particular whether one or more scalar fields were present during inflation and how they contributed to the primordial density perturbation. We propose a new observational test of whether multiple fields, or only one (not necessarily the inflaton) generated the perturbations. We show that our test, relating the bispectrum and trispectrum, is protected against loop corrections at all orders, unlike previous relations.Comment: 6 pages; v2: references added, minor changes; v3: Extended discussion, including the role of gravitational corrections. References added. Version accepted for publication in PR

    Quantum dot behavior in graphene nanoconstrictions

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    Graphene nanoribbons display an imperfectly understood transport gap. We measure transport through nanoribbon devices of several lengths. In nanoribbons of length greater than or equal to 250 nm we observe transport through multiple quantum dots in series, while shorter constrictions of length less than or equal to 60 nm display behavior characteristic of single and double quantum dots. Dot size scales with constriction width. We propose a model where transport occurs through quantum dots that are nucleated by background disorder potentials in the presence of a confinement gap.Comment: published version: 24 pages, 9 figures (includes supplementary information

    Energy in the Eastern Mediterranean: promise or peril? Egmont Paper No. 65, May 2014

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    From the Introduction. In order to address the different challenges and opportunities on energy cooperation in the Eastern Mediterranean Region and Levant Basin, EGMONT – The Royal Institute for International Relations of Belgium – together with the Atlantic Council, and supported by H. E. Belgian Minister for Foreign Affairs Didier Reynders, opened an expert dialogue in 2013 in order to look at how the management of the new energy resources could act as a vector of cooperation instead of conflict between the concerned countries. The activities have targeted finding new possibilities for cooperation on political and security challenges, energy infrastructure development, the regulatory and legal framework, environmental concerns, and bilateral and regional structures, in a manner that enhances stability and security in the region, increases European energy security, contributes to rather than hinders a comprehensive Cyprus settlement, and promotes wider regional cooperation

    The Struggle for Palestinian Hearts and Minds: Violence and Public Opinion in the Second Intifada

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    This paper examines how violence in the Second Intifada influences Palestinian public opinion. Using micro data from a series of opinion polls linked to data on fatalities, we find that Israeli violence against Palestinians leads them to support more radical factions and more radical attitudes towards the conflict. This effect is temporary, however, and vanishes completely within 90 days. We also find some evidence that Palestinian fatalities lead to the polarization of the population and to increased disaffection and a lack of support for any faction. Geographically proximate Palestinian fatalities have a larger effect than those that are distant, while Palestinian fatalities in targeted killings have a smaller effect relative to other fatalities. Although overall Israeli fatalities do not seem to affect Palestinian public opinion, when we divide those fatalities by the different factions claiming responsibility for them, we find some evidence that increased Israeli fatalities are effective in increasing support for the faction that claimed them.Israeli-Palestinian conflict, fatalities, public opinion

    Π^1_1 Borel Sets

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    The results in this paper were motivated by the following question of Sacks. Suppose T is a recursive theory with countably many countable models. What can you say about the least ordinal ɑ such that all models of T have Scott rank below ɑ? If Martin's conjecture is true for T then ɑ ≀ ω·2
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