A Dedicated M-Dwarf Planet Search Using The Hobby-Eberly Telescope

We present first results of our planet search program using the 9.2 meter Hobby-Eberly Telescope (HET) at McDonald Observatory to detect planets around M-type dwarf stars via high-precision radial velocity (RV) measurements. Although more than 100 extrasolar planets have been found around solar-type stars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosse et al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetary system. With the current incompleteness of Doppler surveys with respect to M-dwarfs, it is not yet possible to decide whether this is due to a fundamental difference in the formation history and overall frequency of planetary systems in the low-mass regime of the Hertzsprung-Russell diagram, or simply an observational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in the next 3 to 4 years with the primary goal to answer this question. Here we present the results from the first year of the survey which show that our routine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 are binary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveal a high RV-scatter and represent candidates for having short-periodic planetary companions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtained follow-up observations but no periodic signal is present in the RV-data.Comment: 12 pages, 14 figures, accepted for publication in the Astronomical Journa

Definition of the stimulated emission threshold in high-β\beta nanoscale lasers through phase-space reconstruction

Nanoscale lasers sustain few optical modes so that the fraction of spontaneous emission $\beta$ funnelled into the useful (lasing) mode is high (of the order of few 10$^{-1}$) and the threshold, which traditionally corresponds to an abrupt kink in the light in- light out curve, becomes ill-defined. We propose an alternative definition of the threshold, based on the dynamical response of the laser, which is valid even for $\beta=1$ lasers. The laser dynamics is analyzed through a reconstruction of its phase-space trajectory for pulsed excitation. Crossing the threshold brings about a change in the shape of the trajectory and in the area contained in it. An unambiguous definition of the threshold in terms of this change is shown theoretically and illustrated experimentally in a photonic crystal laser

An m sin i = 24 Earth Mass Planetary Companion To The Nearby M Dwarf GJ 176

We report the detection of a planetary companion with a minimum mass of m sin i = 0.0771 M_Jup = 24.5 M_Earth to the nearby (d = 9.4 pc) M2.5V star GJ 176. The star was observed as part of our M dwarf planet search at the Hobby-Eberly Telescope (HET). The detection is based on 5 years of high-precision differential radial velocity (RV) measurements using the High-Resolution-Spectrograph (HRS). The orbital period of the planet is 10.24 d. GJ 176 thus joins the small (but increasing) sample of M dwarfs hosting short-periodic planets with minimum masses in the Neptune-mass range. Low mass planets could be relatively common around M dwarfs and the current detections might represent the tip of a rocky planet population.Comment: 13 pages preprint, 3 figures, submitted to Ap

Higher-Loop Corrections to the Infrared Evolution of a Gauge Theory with Fermions

We consider a vectorial, asymptotically free gauge theory and analyze the effect of higher-loop corrections to the beta function on the evolution of the theory from the ultraviolet to the infrared. We study the case in which the theory contains $N_f$ copies of a fermion transforming according to the fundamental representation and several higher-dimensional representations of the gauge group. We also calculate higher-loop values of the anomalous dimension of the mass, $\gamma_m$ of $\bar\psi\psi$ at the infrared zero of the beta function. We find that for a given theory, the values of $\gamma_m$ calculated to three- and four-loop order, and evaluated at the infrared zero computed to the same order, tend to be somewhat smaller than the value calculated to two-loop order. The results are compared with recent lattice simulations.Comment: 22 pages, latex, matches Phys. Rev. D publicatio

Real-time price discovery in stock, bond and foreign exchange markets

We characterize the response of U.S., German and British stock, bond and foreign exchange markets to real-time U.S. macroeconomic news. Our analysis is based on a unique data set of high-frequency futures returns for each of the markets. We find that news surprises produce conditional mean jumps; hence high-frequency stock, bond and exchange rate dynamics are linked to fundamentals. The details of the linkages are particularly intriguing as regards equity markets. We show that equity markets react differently to the same news depending on the state of the economy, with bad news having a positive impact during expansions and the traditionally-expected negative impact during recessions. We rationalize this by temporal variation in the competing "cash flow" and "discount rate" effects for equity valuation. This finding helps explain the time-varying correlation between stock and bond returns, and the relatively small equity market news effect when averaged across expansions and recessions. Lastly, relying on the pronounced heteroskedasticity in the high-frequency data, we document important contemporaneous linkages across all markets and countries over-and-above the direct news announcement effects. JEL Klassifikation: F3, F4, G1, C

Nitrous oxide emission from highland winter wheat field after long-term fertilization

Nitrous oxide (N<sub>2</sub>O) is an important greenhouse gas. N<sub>2</sub>O emissions from soils vary with fertilization and cropping practices. The response of N<sub>2</sub>O emission to fertilization of agricultural soils plays an important role in global N<sub>2</sub>O emission. The objective of this study was to assess the seasonal pattern of N<sub>2</sub>O fluxes and the annual N<sub>2</sub>O emissions from a rain-fed winter wheat (<i>Triticum aestivum</i> L.) field in the Loess Plateau of China. A static flux chamber method was used to measure soil N<sub>2</sub>O fluxes from 2006 to 2008. The study included 5 treatments with 3 replications in a randomized complete block design. Prior to initiating N<sub>2</sub>O measurements the treatments had received the same fertilization for 22 years. The fertilizer treatments were unfertilized control (CK), manure (M), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + manure (NPM). Soil N<sub>2</sub>O fluxes in the highland winter wheat field were highly variable temporally and thus were fertilization dependent. The highest fluxes occurred in the warmer and wetter seasons. Relative to CK, m slightly increased N<sub>2</sub>O flux while N, NP and NPM treatments significantly increased N<sub>2</sub>O fluxes. The fertilizer induced increase in N<sub>2</sub>O flux occurred mainly in the first 30 days after fertilization. The increases were smaller in the relatively warm and dry year than in the cold and wet year. Combining phosphorous and/or manure with mineral N fertilizer partly offset the nitrogen fertilizer induced increase in N<sub>2</sub>O flux. N<sub>2</sub>O fluxes at the seedling stage were mainly controlled by nitrogen fertilization, while fluxes at other plant growth stages were influenced by plant and environmental conditions. The cumulative N<sub>2</sub>O emissions were always higher in the fertilized treatments than in the non-fertilized treatment (CK). Mineral and manure nitrogen fertilizer enhanced N<sub>2</sub>O emissions in wetter years compared to dryer years. Phosphorous fertilizer offset 0.50 and 1.26 kg N<sub>2</sub>O-N ha<sup>−1</sup> increases, while manure + phosphorous offset 0.43 and 1.04 kg N<sub>2</sub>O-N ha<sup>−1</sup> increases by N fertilizer for the two observation years. Our results suggested that the contribution of single N fertilizer on N<sub>2</sub>O emission was larger than that of NP and NPM and that manure and phosphorous had important roles in offsetting mineral N fertilizer induced N<sub>2</sub>O emissions. Relative to agricultural production and N<sub>2</sub>O emission, manure fertilization (M) should be recommended while single N fertilization (N) should be avoided for the highland winter wheat due to the higher biomass and grain yield and lower N<sub>2</sub>O flux and annual emission in m than in N