66,918 research outputs found

    "Back to the Future" in Philosophical Dialogue: A Plea for Changing P4C Teacher Education

    Get PDF
    While making P4C much more easily disseminated, short-term weekend and weeklong P4C training programs not only dilute the potential laudatory impact of P4C, they can actually be dangerous. As well, lack of worldwide standards precludes the possibility of engaging in sufficiently high quality research of the sort that would allow the collection of empirical data in support the efficacy of worldwide P4C adoption. For all these reasons, the authors suggest that P4C advocates ought to insist that programs of a minimum of five philosophy courses be accepted as the recognized standard for any teacher to legitimately claim that she is teaching Philosophy for Children

    Nucleon-nucleon potentials in phase-space representation

    Get PDF
    A phase-space representation of nuclear interactions, which depends on the distance r⃗\vec{r} and relative momentum p⃗\vec{p} of the nucleons, is presented. A method is developed that permits to extract the interaction V(r⃗,p⃗)V(\vec{r},\vec{p}) from antisymmetrized matrix elements given in a spherical basis with angular momentum quantum numbers, either in momentum or coordinate space representation. This representation visualizes in an intuitive way the non-local behavior introduced by cutoffs in momentum space or renormalization procedures that are used to adapt the interaction to low momentum many-body Hilbert spaces, as done in the unitary correlation operator method or with the similarity renormalization group. It allows to develop intuition about the various interactions and illustrates how the softened interactions reduce the short-range repulsion in favor of non-locality or momentum dependence while keeping the scattering phase shifts invariant. It also reveals that these effective interactions can have undesired complicated momentum dependencies at momenta around and above the Fermi momentum. Properties, similarities and differences of the phase-space representations of the Argonne and the N3LO chiral potential, and their UCOM and SRG derivatives are discussed

    Robotic observations of the most eccentric spectroscopic binary in the sky

    Full text link
    The visual A component of the Gliese 586AB system is a double-lined spectroscopic binary consisting of two cool stars with the exceptional orbital eccentricity of 0.976. Such an extremely eccentric system may be important for our understanding of low-mass binary formation. We present a total of 598 high-resolution echelle spectra from our robotic facility STELLA from 2006-2012 which we used to compute orbital elements of unprecedented accuracy. The orbit constrains the eccentricity to 0.97608+/-0.00004 and the orbital period to 889.8195+/-0.0003d. The masses of the two components are 0.87+/-0.05 Msun and 0.58+/-0.03 Msun if the inclination is 5+/-1.5degr as determined from adaptive-optics images, that is good to only 6% due to the error of the inclination although the minimum masses reached a precision of 0.3%. The flux ratio Aa:Ab in the optical is betwee n 30:1 in Johnson-B and 11:1 in I. Radial velocities of the visual B-component (K0-1V) appear constant to within 130 m/s over six years. Sinusoidal modulations of Teff of Aa with an amplitude of apprx 55 K are seen with the orbital period. Component Aa appears warmest at periastron and coolest at apastron, indicating atmospheric changes induced by the high orbital eccentricity. No light variations larger than approximately 4 mmag are detected for A, while a photometric period of 8.5+/-0.2 d with an amplitude of 7 mmag is discovered for the active star B, which we interpret to be its rotation period. We estimate an orbital period of approx 50,000 yr for the AB system. The most likely age of the AB system is >=2 Gyr, while the activity of the B component, if it were a single star, would imply 0.5 Gyr. Both Aa and B are matched with single-star evolutionary tracks of their respective mass

    From nucleon-nucleon interaction matrix elements in momentum space to an operator representation

    Full text link
    Starting from the matrix elements of the nucleon-nucleon interaction in momentum space we present a method to derive an operator representation with a minimal set of operators that is required to provide an optimal description of the partial waves with low angular momentum. As a first application we use this method to obtain an operator representation for the Argonne potential transformed by means of the unitary correlation operator method and discuss the necessity of including momentum dependent operators. The resulting operator representation leads to the same results as the original momentum space matrix elements when applied to the two-nucleon system and various light nuclei. For applications in fermionic and antisymmetrized molecular dynamics, where an operator representation of a soft but realistic effective interaction is indispensable, a simplified version using a reduced set of operators is given

    A program to evaluate dye lasers as high power, pulsed, visible light sources

    Get PDF
    Spectral emission of visible from Q switched dye laser
    • 

    corecore