1,161,740 research outputs found

    Low- and intermediate-energy nucleon-nucleon interactions and the analysis of deuteron photodisintegration within the dispersion relation technique

    Full text link
    The nucleon-nucleon interaction in the region of the nucleon kinetic energy up to 1000 MeV is analysed together with the reaction γd→pn\gamma d \to pn in the photon energy range Eγ=0−400E_{\gamma}=0-400 MeV. Nine nucleon-nucleon ss-channel partial amplitudes are reconstructed in the dispersion relation N/DN/D method: 1S0^1S_0, 3S1−3D1^3S_1-^3D_1, 3P0^3P_0, 1P1^1P_1, 3P1^3P_1, 3P2^3P_2, 1D2^1D_2, 3D2^3D_2 and 3F3^3F_3. Correspondingly, the dispersive representation of partial amplitudes NΔ→pnN\Delta \to pn, NN∗→pnNN^* \to pn and NNπ→pnNN\pi \to pn is given. Basing on that, we have performed parameter-free calculation of the amplitude γd→pn\gamma d \to pn, taking into account: (i)(i) pole diagram, (ii)(ii) nucleon-nucleon final-state rescattering γd→pn→pn\gamma d \to pn \to pn, and (iii)(iii) inelastic final-state rescatterings γd→NΔ(1232)→pn\gamma d \to N\Delta(1232) \to pn, γd→NN∗(1400)→pn\gamma d \to NN^*(1400) \to pn and γd→NNπ→pn\gamma d \to NN\pi \to pn. The γd→pn\gamma d \to pn partial amplitudes for nine above-mentioned channels are found. It is shown that the process γd→pn→pn\gamma d \to pn \to pn is significant for the waves 1S0^1S_0, 3P0^3P_0, 3P1^3P_1, at Eγ=50−100E_{\gamma} =50 -100 MeV, while γd→NΔ→pn\gamma d \to N\Delta \to pn for the waves 3P2^3P_2, 1D2^1D_2,3F3^3F_3 dominates at Eγ>300E_{\gamma} > 300 MeV. Meson exchange current contributions into the deuteron disintegration are estimated: they are significant at Eγ=100−400E_\gamma =100-400 MeV.Comment: 22 pages, LaTeX, epsfig.sty, tabl

    Gluonic effects in eta and eta-prime physics

    Full text link
    We review the theory and phenomenology of the axial U(1) problem with emphasis on the role of gluonic degrees of freedom in eta and eta' production processes, especially the low-energy pN -> pN eta and pN -> pN eta' reactions.Comment: 20 pages, 2 figures, Invited talk at the WASA Workshop on Eta Physics, October 2001, Uppsala, Swede

    Planetary Nebulae: Observational Properties, Mimics, and Diagnostics

    Full text link
    The total number of true, likely and possible planetary nebulae (PN) now known in the Milky Way is nearly 3000, double the number known a decade ago. The new discoveries are a legacy of the recent availability of wide field, narrowband imaging surveys, primarily in the light of H-alpha. In this paper, we summarise the various PN discovery techniques, and give an overview of the many types of objects which mimic PN and which appear as contaminants in both Galactic and extragalactic samples. Much improved discrimination of classical PN from their mimics is now possible based on the wide variety of high-quality multiwavelength data sets that are now available. We offer improved taxonomic and observational definitions for the PN phenomenon based on evaluation of these better diagnostic capabilities. However, we note that evidence is increasing that the PN phenomenon is heterogeneous, and PN are likely to be formed from multiple evolutionary scenarios. In particular, the relationships between some collimated symbiotic outflows and bipolar PN remain uncertain.Comment: 25 pages, 6 figures; presentation at the workshop on the Legacies of the Macquarie/AAO/Strasbourg H-alpha Planetary Nebula project, accepted by the Publications of the Astronomical Society of Australia (PASA

    Planetary Nebula Surveys: Past, Present and Future

    Full text link
    In this review we cover the detection, identification and astrophysical importance of planetary nebulae (PN). The legacy of the historic Perek & Kohoutek and Acker et al. catalogues is briefly covered before highlighting the more recent but significant progress in PN discoveries in our Galaxy and the Magellanic Clouds. We place particular emphasis on the major MASH and the IPHAS catalogues, which, over the last decade alone, have essentially doubled Galactic and LMC PN numbers. We then discuss the increasing role and importance that multi-wavelength data is playing in both the detection of candidate PN and the elimination of PN mimics that have seriously biased previous PN compilations. The prospects for future surveys and current efforts and prospects for PN detections in external galaxies are briefly discussed due to their value both as cosmic distance indicators and as kinematical probes of galaxies and dark matter properties.Comment: 8 pages, 1 figure, Proceedings of the Asymmetric Planetary Nebula V Conference (Invited Review, Lake District, England, June 2010

    Comparing Post-Newtonian and Numerical-Relativity Precession Dynamics

    Get PDF
    Binary black-hole systems are expected to be important sources of gravitational waves for upcoming gravitational-wave detectors. If the spins are not colinear with each other or with the orbital angular momentum, these systems exhibit complicated precession dynamics that are imprinted on the gravitational waveform. We develop a new procedure to match the precession dynamics computed by post-Newtonian (PN) theory to those of numerical binary black-hole simulations in full general relativity. For numerical relativity NR) simulations lasting approximately two precession cycles, we find that the PN and NR predictions for the directions of the orbital angular momentum and the spins agree to better than ∼1∘\sim 1^{\circ} with NR during the inspiral, increasing to 5∘5^{\circ} near merger. Nutation of the orbital plane on the orbital time-scale agrees well between NR and PN, whereas nutation of the spin direction shows qualitatively different behavior in PN and NR. We also examine how the PN equations for precession and orbital-phase evolution converge with PN order, and we quantify the impact of various choices for handling partially known PN terms
    • …
    corecore