Supernova neutrinos: Flavor-dependent fluxes and spectra

Transporting nu_mu and nu_tau in a supernova (SN) core involves several processes that have been neglected in traditional simulations. Based on a Monte Carlo study we find that the flavor-dependent spectral differences are much smaller than is often stated in the literature. A full-scale SN simulation using a Boltzmann solver and including all relevant neutrino reactions confirms these results. The flavor-dependent flux differences are largest during the initial accretion phase.Comment: Proceedings NOON 03, Kanazawa, 10-14 Feb 200

XMM-Newton observation of the ULIRG NGC 6240: The physical nature of the complex Fe K line emission

We report on an XMM-Newton observation of the ultraluminous infrared galaxy NGC 6240. The 0.3-10 keV spectrum can be successfully modelled with: (i) three collisionally ionized plasma components with temperatures of about 0.7, 1.4, and 5.5 keV; (ii) a highly absorbed direct power-law component; and (iii) a neutral Fe K_alpha and K_beta line. We detect a significant neutral column density gradient which is correlated with the temperature of the three plasma components. Combining the XMM-Newton spectral model with the high spatial resolution Chandra image we find that the temperatures and the column densities increase towards the center. With high significance, the Fe K line complex is resolved into three distinct narrow lines: (i) the neutral Fe K_alpha line at 6.4 keV; (ii) an ionized line at about 6.7 keV; and (iii) a higher ionized line at 7.0 keV (a blend of the Fe XXVI and the Fe K_beta line). While the neutral Fe K line is most probably due to reflection from optically thick material, the Fe XXV and Fe XXVI emission arises from the highest temperature ionized plasma component. We have compared the plasma parameters of the ultraluminous infrared galaxy NGC 6240 with those found in the local starburst galaxy NGC 253. We find a striking similarity in the plasma temperatures and column density gradients, suggesting a similar underlying physical process at work in both galaxies.Comment: 8 pages including 9 figures. Accepted for publication in A&

Numerical Toy-Model Calculation of the Nucleon Spin Autocorrelation Function in a Supernova Core

We develop a simple model for the evolution of a nucleon spin in a hot and dense nuclear medium. A given nucleon is limited to one-dimensional motion in a distribution of external, spin-dependent scattering potentials. We calculate the nucleon spin autocorrelation function numerically for a variety of potential densities and distributions which are meant to bracket realistic conditions in a supernova core. For all plausible configurations the width of the spin-density structure function is found to be less than the temperature. This is in contrast with a naive perturbative calculation based on the one-pion exchange potential which overestimates the width and thus suggests a large suppression of the neutrino opacities by nucleon spin fluctuations. Our results suggest that it may be justified to neglect the collisional broadening of the spin-density structure function for the purpose of estimating the neutrino opacities in the deep inner core of a supernova. On the other hand, we find no indication that processes such as axion or neutrino pair emission, which depend on nucleon spin fluctuations, are substantially suppressed beyond the multiple-scattering effect already discussed in the literature. Aside from these practical conclusions, our model reveals a number of interesting and unexpected insights. For example, the spin-relaxation rate saturates with increasing potential strength only if bound states are not allowed to form by including a repulsive core. There is no saturation with increasing density of scattering potentials until localized eigenstates of energy begin to form.Comment: 14 latex pages in two-column format, 15 postscript figures included, uses revtex.sty and epsf.sty. Submitted to Physical Review

Nucleon Spin Fluctuations and the Supernova Emission of Neutrinos and Axions

In the hot and dense medium of a supernova (SN) core, the nucleon spins fluctuate so fast that the axial-vector neutrino opacity and the axion emissivity are expected to be significantly modified. Axions with m_a\alt10^{-2}\,{\rm eV} are not excluded by SN~1987A. A substantial transfer of energy in neutrino-nucleon ($\nu N$) collisions is enabled which may alter the spectra of SN neutrinos relative to calculations where energy-conserving $\nu N$ collisions had been assumed near the neutrinosphere.Comment: 8 pages. REVTeX. 2 postscript figures, can be included with epsf. Small modifications of the text, a new "Note Added", and three new references. To be published in Phys. Rev. Let

Development of a network for the on-farm conservation of crop genetic resources: First results of a pilot project for the re-introduction of old Lactuca varieties to the market

In a pilot project, we examined the chance of maintaining plant genetic resources by commercial utilization of old varieties using Lactuca sativa as a model plant. Nine market gardens in the region of Berlin and Brandenburg cultivated 18 old varieties during four cultivation periods to test field performance. They supplied the products to the market in their customary manner to analyse marketing success. Seven of the market gardens practice organic horticulture. In a complementary field trial at Humboldt-Universität zu Berlin, we established data concerning the field performance of the varieties, analysed dry matter contents, nitrate and phenol concentrations, and observed shelf life for two days under simulated retail conditions (18°C, 80% rel. air humidity). Generally, yield was acceptable for market purposes. However, cultivation in autumn failed because of the cold climate. Biotic and abiotic factors like slugs or hail caused non-specific damages. Specific problems of particular varieties were less important. Based on the results of 2007, the varieties can be put preliminarily into three categories: suitable for on-farm conservation, suitable for home gardens, and varieties with contrasting results depending on the respective market garden.The nitrate concentrations of all varieties were clearly below the EU acceptable limit of 2500 mg/kg fresh weight of lettuce grown in the field. The phenol concentrations varied from 3.3 to 17.2 mg GAE/g dry weight. Generally, the cultivars had a reasonable shelf life of one to two days, however three varieties showed a better storability whereas four other cultivars deteriorated rapidly. Marketing success was good in Berlin City but poor in the countryside of Brandenburg. The regular customers of the market gardens in Berlin who prefer organic food are a promising target group for further stimulation of interest to buy rare crop varieties. The on-farm conservation of old varieties in market gardens requires relatively large quantities of seeds of good quality. However there might arise problems in seed supply as the VERN e.V. was confronted with bottleneck problems. Therefore, we organised a network of interested market gardens who take on maintenance and propagation of individual varieties. The network will be developed in co-operation with the VERN e.V. who will also process the seed as well as organise the exchange of the various varieties within the network. Further, the network will deal with problems concerning maintenance breeding and seed quality

Monte Carlo Study of Supernova Neutrino Spectra Formation

The neutrino flux and spectra formation in a supernova core is studied by using a Monte Carlo code. The dominant opacity contribution for nu_mu and nu_tau is elastic scattering on nucleons. In addition we switch on or off a variety of processes which allow for the exchange of energy or the creation and destruction of neutrino pairs, notably nucleon bremsstrahlung, the e^+ e^- pair annihilation process and nu_e-bar nu_e -> nu_{mu,tau} nu_{mu,tau}-bar, recoil and weak magnetism in elastic nucleon scattering, elastic scattering on electrons and positrons and elastic scattering on electron neutrinos and anti-neutrinos. The least important processes are neutrino-neutrino scattering and e^+ e^- annihilation. The formation of the spectra and fluxes of nu_mu is dominated by the nucleonic processes, i.e. bremsstrahlung and elastic scattering with recoil, but also nu_e nu_e-bar annihilation and nu_mu e^\pm scattering contribute significantly. When all processes are included, the spectral shape of the emitted neutrino flux is always ``pinched,'' i.e. the width of the spectrum is smaller than that of a thermal spectrum with the same average energy. In all of our cases we find that the average nu_mu-bar energy exceeds the average nu_e-bar energy by only a small amount, 10% being a typical number. Weak magnetism effects cause the opacity of nu_mu to differ slightly from that of nu_mu-bar, translating into differences of the luminosities and average energies of a few percent. Depending on the density, temperature, and composition profile, the flavor-dependent luminosities L_{nu_e}$, L_{nu_e-bar}, and L_{nu_mu} can mutually differ from each other by up to a factor of two in either direction.Comment: 33 pages, 16 eps-figs, submitted to ApJ. Sections added: weak magnetism, discussion of different analytic fits to the spectra and detailed spectral shap

Impact histories of Vesta and Vestoids inferred from howardites, eucrites and diogenites

The parent body of the howardites, eucrites and diogenites (HEDs) is thought to be asteroid (4) Vesta [1]. However, several eucrites have now been recognized, like NWA 011 and Ibitira, with major element compositions and mineralogy like normal eucrites but with different oxygen isotope compositions and minor element concentrations suggesting they are not from the same body [2, 3]. The discoveries of abnormal eucrites and V-type asteroids that are probably not from Vesta [see 4] raise the question whether the HEDs with normal oxygen isotopes are coming from Vesta [3]. To address this issue and understand more about the evolution of Vesta in preparation for the arrival of the Dawn spacecraft, we integrate fresh insights from Ar-Ar dating and oxygen isotope analyses of HEDs, radiometric dating of differentiated meteorites, as well as dynamical and astronomical studies of Vesta, the Vesta asteroid family (i.e., the Vestoids), and other V-type asteroids

Trapping cold atoms using surface-grown carbon nanotubes

We present a feasibility study for loading cold atomic clouds into magnetic traps created by single-wall carbon nanotubes grown directly onto dielectric surfaces. We show that atoms may be captured for experimentally sustainable nanotube currents, generating trapped clouds whose densities and lifetimes are sufficient to enable detection by simple imaging methods. This opens the way for a novel type of conductor to be used in atomchips, enabling atom trapping at sub-micron distances, with implications for both fundamental studies and for technological applications

Entomology in Ecuador : recent developments and future challenges

We review and analyze the recent development and future challenges facing entomology as a science in Ecuador, a country with limited financial and human resources and numerous environmental problems. Taxonomic studies of the Ecuadorian insect fauna have been well developed for only a few groups (e.g. Papilionoidea, Carabidae) and remains in its infancy for most insect orders. This is due to the huge diversity of species living in a great diversity of habitats and the difficulty to identify most species. There is a lack of published basic biological information and to a high rate of endemism of many groups, especially in the Andes. The development of ecological entomology as a formal discipline in Ecuador is a very recent phenomenon, and has been mostly limited to descriptive studies of the environmental factors that govern insect diversity and abundance. We outline a set of research challenges regarding the impact of global environmental changes on insect communities and habitats they live in and propose potential strategies for the development of entomology in Ecuador. Both basic and applied research will be important in this context as well as international collaboration to strengthen the role of entomological science in decision making processes in the country