Factorizations,Localizations, and the Orthogonal Subcategory Problem

In this paper factorization structures of an abstract category are considered, depending on a class ?? of morphisms which is not necessarily closed under composition; as soon as it is one obtains the usual factorization systems defined by the diagonal-fill-in property. General existence criteria for those factorization structures are proved, in particular for monotone-light factorizations which are defined for abstract categories and which are considered in more detail. Finally, sufficient conditions for a positive solution of the Orthogonal Subcategory Problem are derived from the existence of certain factorization structures.     

Conversion coefficient for internal pair creation

The conversion coefficient for internal electron-positron pair formation is calculated for arbitrary electric and magnetic multipolarity. Analytical expressions for the differential conversion coefficientdβ/dE _p can be derived in the range 0≦Z≦118, if one employs relativistic Coulomb wave functions according to pointlike nuclei for the electron. Especially forML-transitions in the high-Z-region we found large deviations from results obtained within the Born approximation.     

Measurements of temperatures and OH-concentrations in a lean methane-air flame using high-resolution laser-absorption spectroscopy

Line profile measurements of selected spectral lines in the 1-0 band of the A²Σ⁺-X²π system of OH near 2830 Å, using a tunable, frequency-doubled dye laser, have been made to determine simultaneously the translational temperature and hydroxyl concentration in a laminar, flat methane-air flame. The rotational temperature was determined from the ratio of two line-absorption coefficients. The rotational degree of freedom was found to be in equilibrium with the translational degree of freedom. Values deduced for the collision broadening parameter in the 1-0 band depend on OH-concentration, ground state rotational quantum number and, possibly, on the vibrational quantum number.     

Stability and decay of the Dirac vacuum in external gauge fields

We consider various gauge fields coupled to the free Dirac equation according to symmetry principles. The gauge fields are treated as classical, unquantized fields. Sufficiently strong time-independent fields may give rise to spontaneous particle creation and to the decay of the symmetric Dirac vacuum into a new ground state with broken symmetry. The vacuum stability of the Dirac field is studied for the cases of external electromagnetic (U(1)), gravitational (Poincaré group including torsion) and Yang-Mills (SU(2)) potentials.     

Messung der komplexen Dielektrizitätskonstanten von Seignette-Salz bei 10 GHz in Abhängigkeit von der Temperatur

We determined the complex dielectric constant of Rochelle Salt at 9.61·10⁹ Hz and its temperature dependence using a microwave interferometer. In thex-direction of the crystal which becomes its ferroelectric axis between ?18°C and +24°C, the real part of the dielectric constant shows distinct minima at the transition points according to our measurements. We find agreement with results ofJäckle but discrepancies to older measurements. Neither the humidity of the surrounding atmosphere nor the position of the sample in the growing crystal proved to have an effect. In they- andz-directions, we observed no anomaly of the dielectric constant.     

A differential technique which is independent of initial conditions for calculating the rate constant of a second-order reaction

It has been shown that experimental errors of the initial conditions of a second-order reaction can cause erroneous results with the rate constant calculated directly from the differential or integrated rate expression. By means of a computer method, a differential technique has been developed so that precise initial reactant conditions are not necessary for calculating a second-order rate constant if continuous measurements of a single reaction variable are available. The technique has been successfully applied to the data of Kistiakowsky and Lacher on the condensation of acrolein and butadiene.