Pointlike electric charge in gravitational field theory

The existence of charged elementary 'point particles' still is a basically unsolved puzzle in theoretical physics. The present work takes a fresh look at the problem by including gravity---without resorting to string theory. Using Einstein's equations for the gravitational fields in a general static isotropic metric with the full energy-momentum tensor (for the charged material mass and the electromagnetic fields) as the source term, a novel exact solution with a well-defined characteristic radius emerges where mass and charge accumulate: $r_{\rm c}{=}\sqrt{r_{\rm e}r_o/2}$---with $r_{\rm e}{=}Q^2\!/4\pi\epsilon_omc^2$ being the 'classical' radius associated with the total charge $Q$ and where $r_o{=}2mG/c^2$ is the Schwarzschild radius belonging to the observable mass $m$ (for the electron one has $r_{\rm e}{\approx}10^{-15}$m and $r_o{\approx}\,10^{-57}$m). The resulting 'Einstein-Maxwell' gravitational electron radius can also be written as $r_{\rm c}{=}\ell_{\rm P}\sqrt{\alpha_{\rm e}}$, where $\ell_{\rm P}{=}\sqrt{\hbar G/c^3}{\approx}10^{-35}$m is the fundamental Planck length and $\alpha_{\rm e}{=}e^2\!/4\pi\epsilon_o\hbar c{\approx}1/137$ the fine-structure constant, which yields $r_{\rm c}^{\rm electron}{=}1.38063{\times}10^{-36}$m.Comment: 13 pages, 2 figure

Synchronisation Properties of Trees in the Kuramoto Model

We consider the Kuramoto model of coupled oscillators, specifically the case of tree networks, for which we prove a simple closed-form expression for the critical coupling. For several classes of tree, and for both uniform and Gaussian vertex frequency distributions, we provide tight closed form bounds and empirical expressions for the expected value of the critical coupling. We also provide several bounds on the expected value of the critical coupling for all trees. Finally, we show that for a given set of vertex frequencies, there is a rearrangement of oscillator frequencies for which the critical coupling is bounded by the spread of frequencies.Comment: 21 pages, 19 Figure

Temperature relaxation and the Kapitza boundary resistance paradox

The calculation of the Kapitza boundary resistance between dissimilar harmonic solids has since long (Little [Can. J. Phys. 37, 334 (1959)]) suffered from a paradox: this resistance erroneously tends to a finite value in the limit of identical solids. We resolve this paradox by calculating temperature differences in the final heat-transporting state, rather than with respect to the initial state of local equilibrium. For a one-dimensional model we thus derive an exact, paradox-free formula for the boundary resistance. The analogy to ballistic electron transport is explained.Comment: 10 p., REVTeX 3.0 with LaTeX 2.09, ITFA-94-2

Atomic force microscopy shows that vaccinia topoisomerase IB generates filaments on DNA in a cooperative fashion

Type IB DNA topoisomerases cleave and rejoin one strand of the DNA duplex, allowing for the removal of supercoils generated during replication and transcription. In addition, electron microscopy of cellular and viral TopIB–DNA complexes has suggested that the enzyme promotes long-range DNA–DNA crossovers and synapses. Here, we have used the atomic force microscope to visualize and quantify the interaction between vaccinia topoisomerase IB (vTopIB) and DNA. vTopIB was found to form filaments on nicked-circular DNA by intramolecular synapsis of two segments of a single DNA molecule. Measuring the filament length as a function of protein concentration showed that synapsis is a highly cooperative process. At high protein:DNA ratios, synapses between distinct DNA molecules were observed, which led to the formation of large vTopIB-induced DNA clusters. These clusters were observed in the presence of Mg(2+), Ca(2+) or Mn(2+), suggesting that the formation of intermolecular vTopIB-mediated DNA synapsis is favored by screening of the DNA charge

Flexible Labor and Innovation Performance: Evidence from Longitudinal Firm-Level Data

Firms with high shares of workers on fixed-term contracts have significantly higher sales of imitative new products but perform significantly worse on sales of inno¬va¬tive new products (“first on the marketâ€). High functional flexibility in “insider-outsider†la¬bor markets enhances a firm’s new product sales, as do training efforts and highly edu¬ca¬¬ted personnel. We find weak evidence that larger and older firms have higher new pro¬duct sales than do younger and smaller firms. Our findings should be food for thought to eco-nomists making unqualified pleas for the deregulation of labor markets.J5;M5;O15;O31;OSA longitudinal dataset;SMEs;innovation performance;new product sales;numerical flexibility

Flexible labor and innovation performance: Evidence from longitudinal firm-level data

Firms with high shares of workers on fixed-term contracts have significantly higher sales of imitative new products but perform significantly worse on sales of innovative new products (“first on the market”). High functional flexibility in “insider-outsider” labor markets enhances a firm’s new product sales, as do training efforts and highly educated personnel. We find weak evidence that larger and older firms have higher new product sales than do younger and smaller firms. Our findings should be food for thought to economists making unqualified pleas for the deregulation of labor markets.Innovation performance; new product sales; numerical flexibility; functional flexibility; SMEs; OSA longitudinal data

Exactly solvable path integral for open cavities in terms of quasinormal modes

We evaluate the finite-temperature Euclidean phase-space path integral for the generating functional of a scalar field inside a leaky cavity. Provided the source is confined to the cavity, one can first of all integrate out the fields on the outside to obtain an effective action for the cavity alone. Subsequently, one uses an expansion of the cavity field in terms of its quasinormal modes (QNMs)-the exact, exponentially damped eigenstates of the classical evolution operator, which previously have been shown to be complete for a large class of models. Dissipation causes the effective cavity action to be nondiagonal in the QNM basis. The inversion of this action matrix inherent in the Gaussian path integral to obtain the generating functional is therefore nontrivial, but can be accomplished by invoking a novel QNM sum rule. The results are consistent with those obtained previously using canonical quantization.Comment: REVTeX, 26 pages, submitted to Phys. Rev.

Elliptical flux vortices in YBa2Cu3O7

The most energetically favorable vortex in YBa2Cu3O7 forms perpendicular to an anisotropic plane. This vortex is elliptical in shape and is distinguished by an effective interchange of London penetration depths from one axis of the ellipse to another. By generalizing qualitatively from the isotropic to the anisotropic case, we suggest that the flux flow resistivity for the vortex that forms perpendicular to an anistropic plane should have a preferred direction. Similar reasoning indicates that the Kosterlitz-Thouless transition temperature for a vortex mediated transition should be lower if the vortex is elliptical in shape

Electronic Transport Spectroscopy of Carbon Nanotubes in a Magnetic Field

We report magnetic field spectroscopy measurements in carbon nanotube quantum dots exhibiting four-fold shell structure in the energy level spectrum. The magnetic field induces a large splitting between the two orbital states of each shell, demonstrating their opposite magnetic moment and determining transitions in the spin and orbital configuration of the quantum dot ground state. We use inelastic cotunneling spectroscopy to accurately resolve the spin and orbital contributions to the magnetic moment. A small coupling is found between orbitals with opposite magnetic moment leading to anticrossing behavior at zero field.Comment: 7 pages, 4 figure