On the electric conductivity of highly ordered monolayers of monodisperse metal nanoparticles

Monolayers of colloidally synthesized cobalt-platinum nanoparticles of different diameters characterized by TEM (transmission electron microscopy) were deposited on structured silicon oxide substrates and characterized by SEM (scanning electron microscopy), GISAXS (grazing incidence x-ray scattering), and electric transport measurements. The highly ordered nanoparticle films show a thermally activated electron hopping between spatially adjacent particles at room temperature and Coulomb blockade at low temperatures. We present a novel approach to experimentally determine the particles charging energies giving values of 6.7-25.4 meV dependent on the particles size and independent of the interparticle distance. These observations are supported by FEM (finite element method) calculations showing the self-capacitance to be the determining value which only depends on the permittivity constant of the surrounding space and the particles radius.Comment: 6 pages, 5 figure

Energetics and phasing of nonprecessing spinning coalescing black hole binaries

We present an improved numerical relativity (NR) calibration of the new effective-one-body (EOB) model for coalescing non precessing spinning black hole binaries recently introduced by Damour and Nagar [Physical Review D 90, 044018 (2014)]. We do so by comparing the EOB predictions to both the phasing and the energetics provided by two independent sets of NR data covering mass ratios $1\leq q \leq 9.989$ and dimensionless spin range $-0.95\leq \chi\leq +0.994$. One set of data is a subset of the Simulating eXtreme Spacetimes (SXS) catalog of public waveforms; the other set consists of new simulations obtained with the Llama code plus Cauchy Characteristic Evolution. We present the first systematic computation of the gauge-invariant relation between the binding energy and the total angular momentum, $E_{b}(j)$, for a large sample of, spin-aligned, SXS and Llama data. The dynamics of the EOB model presented here involves only two free functional parameters, one ($a_6^c(\nu)$) entering the non spinning sector, as a 5PN effective correction to the interaction potential, and one ($c_3(\tilde{a}_1,\tilde{a}_2,\nu))$ in the spinning sector, as an effective next-to-next-to-next-to-leading order correction to the spin-orbit coupling. These parameters are determined (together with a third functional parameter $\Delta t_{\rm NQC}(\chi)$ entering the waveform) by comparing the EOB phasing with the SXS phasing, the consistency of the energetics being checked afterwards. The quality of the analytical model for gravitational wave data analysis purposes is assessed by computing the EOB/NR faithfulness. Over the NR data sample and when varying the total mass between 20 and 200~$M_\odot$ the EOB/NR unfaithfulness (integrated over the NR frequency range) is found to vary between $99.493\%$ and $99.984\%$ with a median value of $99.944\%$.Comment: 26 pages, 27 figures, results improved with respect to first versio

Accruals, Cash-Flows and Tobin’s q : An Investment Perspective on Firm Accruals

Following Zhang (Accounting Review, 2007) we cast firm accruals in terms of short-term investment. Since many studies consider accruals as a smoothed measure of cash flows, we first adopt Zhang specification and augment the standard Jones model with a cash-flow variable. Second, if accruals are indeed a form of short-term investment they should also be influenced by firm’s performance as measured by Tobin’s q. Consequently we propose a new version of the accrual model including a proxy for Tobin’s q. Given that accounting data and Tobin’s q are generally measured with errors, we also introduce a new estimation method based on a modified version of the Hausman artificial regression, featuring an optimal weighting matrix composed of higher moments instrumental variable estimators. Our results suggest that all the key parameters of the accrual models are indeed systematically biased with measurement errors. More importantly, our findings largely qualify Zhang’s conjecture on accruals, as both cash-flows and Tobin’s q are found strongly significant regressors of firm accruals. Relatedly we find that the Tobin’s q augmented model better isolate discretionary accruals so that the residuals of the equation are particularly well-suited to forecast stock returns.Discretionary accruals; Earnings management; Investment; Measurement errors; Higher moments; Instrumental variable estimators.

Solving linear parabolic rough partial differential equations

We study linear rough partial differential equations in the setting of [Friz and Hairer, Springer, 2014, Chapter 12]. More precisely, we consider a linear parabolic partial differential equation driven by a deterministic rough path $\mathbf{W}$ of H\"older regularity $\alpha$ with $1/3 < \alpha \le 1/2$. Based on a stochastic representation of the solution of the rough partial differential equation, we propose a regression Monte Carlo algorithm for spatio-temporal approximation of the solution. We provide a full convergence analysis of the proposed approximation method which essentially relies on the new bounds for the higher order derivatives of the solution in space. Finally, a comprehensive simulation study showing the applicability of the proposed algorithm is presented

Accruals, Investment and Errors-in-Variables

We formulate well-known discretionary accruals models in an investment setting. Given that accruals basically consist of short-term investment, we introduce, (i) cash-flows, as a proxy for financial constraints and other financial markets imperfections, and (ii) Tobin’s q as a measure of capital return. Accounting data and Tobin’s q being measured with errors, we propose an econometric method based on a modified version of the Hausman artificial regression which features an optimal weighting matrix of higher moments instrumental variable estimators. The empirical results suggest that all the key parameters of the discretionary accruals models studied are biased systematically with measurement errors.Discretionary accruals; Earnings management; Investment; Measurement errors; Higher moments; Instrumental variable estimators.

Peller's problem concerning Koplienko-Neidhardt trace formulae: the unitary case

We prove the existence of a complex valued $C^2$-function on the unit circle, a unitary operator U and a self-adjoint operator Z in the Hilbert-Schmidt class $S^2$, such that the perturbated operator $$f(e^{iZ}U)-f(U) -\frac{d}{dt}\bigl(f(e^{itZ}U)\bigr)_{\vert t=0}$$ does not belong to the space $S^1$ of trace class operators. This resolves a problem of Peller concerning the validity of the Koplienko-Neidhardt trace formula for unitaries