New half supersymmetric solutions of the heterotic string

We describe all supersymmetric solutions of the heterotic string which preserve 8 supersymmetries and show that are distinguished by the holonomy, ${\rm hol}(\hat\nabla)$, of the connection, $\hat\nabla$, with skew-symmetric torsion. The ${\rm hol}(\hat\nabla) \subseteq SU(2)$ solutions are principal bundles over a 4-dimensional hyper-K\"ahler manifold equipped with a anti-self-dual connection and fibre group $G$ which has Lie algebra, {\mathfrak Lie} (G)=\bR^{5,1}, \mathfrak{sl}(2,\bR)\oplus \mathfrak{su}(2) or $\mathfrak{cw}_6$. Some of the solutions have the interpretation as 5-branes wrapped on $G$ with transverse space any hyper-K\"ahler 4-dimensional manifold. We construct new solutions for {\mathfrak Lie} (G)=\mathfrak{sl}(2,\bR)\oplus \mathfrak{su}(2) and show that are characterized by 3 integers and have continuous moduli. There is also a smooth family in this class with one asymptotic region and the dilaton is bounded everywhere on the spacetime. We also demonstrate that the worldvolume theory of the backgrounds with holonomy SU(2) can be understood in terms of gauged WZW models for which the gauge fields are composite. The {\rm hol}(\hat\nabla) \subseteq\bR^8 solutions are superpositions of fundamental strings and pp-waves in flat space, which may also include a null rotation. The ${\rm hol}(\hat\nabla)=\{1\}$ heterotic string backgrounds which preserve 8 supersymmetries are Lorentzian group manifolds.Comment: 31 pages, minor corrections, analysis improved and more references adde

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Artisanal fish fences pose broad and unexpected threats to the tropical coastal seascape

Gear restrictions are an important management tool in small-scale tropical fisheries, improving sustainability and building resilience to climate change. Yet to identify the management challenges and complete footprint of individual gears, a broader systems approach is required that integrates ecological, economic and social sciences. Here we apply this approach to artisanal fish fences, intensively used across three oceans, to identify a previously underrecognized gear requiring urgent management attention. A longitudinal case study shows increased effort matched with large declines in catch success and corresponding reef fish abundance. We find fish fences to disrupt vital ecological connectivity, exploit > 500 species with high juvenile removal, and directly damage seagrass ecosystems with cascading impacts on connected coral reefs and mangroves. As semi-permanent structures in otherwise open-access fisheries, they create social conflict by assuming unofficial and unregulated property rights, while their unique high-investment-low-effort nature removes traditional economic and social barriers to overfishing

Tissue Distribution and Uptake of Endogenous Lipoprotein Triglycerides in the Rat

Circulating free fatty acids (FFA) are in part taken up by the liver and released again as fatty acid esters transported in the blood as lipopro-teins (1-5). The first of these esters to appear is triglycerides, which are followed in turn by cho-lesterol esters and phospholipids (6). The liver is the principal source of the circulating triglycer-ides formed from plasma FFA; other tissues con-tribute minimally if at all to the process (5, 7). When serum containing these labeled triglycerides is reinjected, they are to a large extent quickly taken up by the liver, and a rapid exchange be-tween plasma and liver triglycerides apparently takes place (3). Recently, Havel, Felts, and Van Duyne have evaluated the fate of reinjected endogenously formed circulating labeled triglycerides associated with lipoproteins of density (D) < 1.006 (8). They found that radioactivity appeared in most tissues and that the tissue distribution of the label seemed to be the same as that found after in-jection of chylomicrons. Our investigation provides data, in the rat, on 1) the serum lipoprotein distribution of triglycer-ides formed after injection of radioactive palmi-tate, 2) the tissue distribution of the reinjected * Submitted for publication March 23, 1963; accepte