An estimate of theta_14 independent of the reactor antineutrino flux determinations

In a previous paper [Phys. Rev. D 83, 113013 (2011)] we have shown that the solar sector data (solar and KamLAND) are sensitive to the parameter theta_14, encoding the admixture of the electron neutrino with a fourth (essentially) sterile mass eigenstate. In that work we evidenced that such data prefer a non-zero value of theta_14 and that such a preference is completely degenerate with that of non-zero theta_13. In this report we show how the evidence of theta_13 > 0, recently emerged from global neutrino data analyses, lifts such a degeneracy and disfavors the case of sterile neutrino mixing. By excluding from our analysis the total rate information coming from the reactor experiments we untie our results from any assumption on their flux normalization. In this way, we establish the robust upper bound sin^2 (theta_14) < 0.04 at the 90% C.L.Comment: 4 pages, 1 figure, minor changes, matches version accepted by PR

Astrometric Method to Break the Photometric Degeneracy between Binary-source and Planetary Microlensing Perturbations

An extra-solar planet can be detected by microlensing because the planet can perturb the smooth lensing light curve created by the primary lens. However, it was shown by Gaudi that a subset of binary-source events can produce light curves that closely resemble those produced by a significant fraction of planet/star lens systems, causing serious contamination of a sample of suspected planetary systems detected via microlensing. In this paper, we show that if a lensing event is observed astrometrically, one can unambiguously break the photometric degeneracy between binary-source and planetary lensing perturbations. This is possible because while the planet-induced perturbation in the trajectory of the lensed source image centroid shifts points away from the opening of the unperturbed elliptical trajectory, while the perturbation induced by the binary source companion points always towards the opening. Therefore, astrometric microlensing observations by using future high-precision interferometers will be important for solid confirmation of microlensing planet detections.Comment: total 5 pages, including 1 figure and no table, ApJ, submitted, better quality pdf file is avalilable at http://astroph.chungbuk.ac.kr/~cheongho/publication.htm

China and the Arctic

Much attention has been paid to China’s Arctic ambitions as of late, with many commentators warning of a forthcoming aggressive pursuit of control over Arctic resources and shipping lanes. This article reviews China’s longstanding scientific, and growing economic and political, interests in the region and concludes that China has far more to gain by cooperating with Arctic neighbors and buying energy from Arctic EEZ-based projects, than by pursuing an aggressive and confrontational exploration strategy, which could be counterproductive for China's own position regarding disputes in the South China Sea. China has been pursuing cooperative and collaborative relations in the region, and is likely to do so in the future, not least because it is in its strategic and economic interest to do so

The Snow Dragon: China’s Strategies in the Arctic

In recent years, several analyses and news media articles have predicted a resurgence of tensions in the Arctic over access to maritime space. Among the contenders involved in this potential struggle is China, whose ambitions in the region are suspected to hold a destabilising potential. Yet, as Beijing is developing its policy towards the region, it remains unclear whether it will contest the claims over maritime access of countries bordering the Arctic and forcibly take over parts of the region for resource extraction purposes

Semidefinite approximations of projections and polynomial images of semialgebraic sets

Given a compact semialgebraic set S of R^n and a polynomial map f from R^n to R^m, we consider the problem of approximating the image set F = f(S) in R^m. This includes in particular the projection of S on R^m for n greater than m. Assuming that F is included in a set B which is simple (e.g. a box or a ball), we provide two methods to compute certified outer approximations of F. Method 1 exploits the fact that F can be defined with an existential quantifier, while Method 2 computes approximations of the support of image measures.The two methods output a sequence of superlevel sets defined with a single polynomial that yield explicit outer approximations of F. Finding the coefficients of this polynomial boils down to computing an optimal solution of a convex semidefinite program. We provide guarantees of strong convergence to F in L^1 norm on B, when the degree of the polynomial approximation tends to infinity. Several examples of applications are provided, together with numerical experiments

China’s strategy in the Arctic : threatening or opportunistic?

In a context of rapid climatic change in the Arctic, the fast melting of permafrost, the decline of glaciers and the melting of sea ice created perceived strategic and economic opportunities for the littoral states. The attention of states beyond the region was also attracted. For example China, without direct access to the Arctic, displays an interest in Arctic research, natural resources, and shipping potential. However, its diplomatic, economic, political and scientific efforts in this region arouse negative reactions among western media. They often draw up a portrait of an ambitious and arrogant China, ready to push aside the sovereignty of the Arctic countries to defend its own interests in the Arctic. From this perspective, it seems relevant to analyse China's activities in the region and to try to assess Beijing's strategy, which seems more driven by opportunism than by a long-term desire to challenge the littoral states’ sovereignty

Is China's interest for the Arctic driven by Arctic shipping potential?

Interest from the Chinese government has been on the rise since about 2005, and the media have widely reported on these Chinese projects. China is often described as being very interested in both Arctic mineral resources and the opening of Arctic shipping routes, but in this characterization there is a hint of a perceived threat, as commentators are often stressing out that China’s appetite may lead Beijing into considering the Northwest Passage an international strait and resources as open up for grabs. However, the motives for this Chinese interest boils down to three points: diplomacy, access to natural resources and access to Arctic sea routes. To what extent are Chinese shipping firms really interested in developing active service along these polar waterways

A proposed search for a fourth neutrino with a PBq antineutrino source

Several observed anomalies in neutrino oscillation data can be explained by a hypothetical fourth neutrino separated from the three standard neutrinos by a squared mass difference of a few eV^2. We show that this hypothesis can be tested with a PBq (ten kilocurie scale) 144Ce or 106Ru antineutrino beta-source deployed at the center of a large low background liquid scintillator detector. In particular, the compact size of such a source could yield an energy-dependent oscillating pattern in event spatial distribution that would unabiguously determine neutrino mass differences and mixing angles.Comment: 4 pages ; 1 table ; 4 figures - Add energy spectrum shape only analysis + referee comments/suggestion