The performance implications of innovation in small and medium-sized enterprises (SMEs) have attracted considerable interest among academics and practitioners. However, empirical research on the innovation–performance relationship in SMEs shows controversial results. This meta-analysis synthesizes empirical findings in order to obtain evidence whether and especially under which circumstances smaller, resource-scarce firms benefit from innovation. We find that innovation–performance relationship is context dependent. Factors such as the age of the firm, the type of innovation, and the cultural context affect the impact of innovation on firm performance to a large extent

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The evolution of the so-called "41 meV resonance" in the magnetic response of YBCO cuprates is studied with slave-boson theory for the t-t ′ -J-model. The resonance appears as a collective spin fluctuation in the d-wave superconducting (SC) state. It is undamped at optimal doping due to a threshold in the excitation energies of particle-hole pairs with relative wave vector (π, π) . When hole filling is reduced, the resonance moves to lower energies and broadens. Below the resonance energy we find a crossover to an incommensurate response in agreement with a recent experiment on YBa2Cu3O6.6 . We show that dynamic nesting in the d-wave SC state causes this effect.PACS numbers: 71.10. Fd, 74.25.Ha, 74.72.Bk, 75.20.Hr One of the puzzling phenomena in copper-oxide superconductors is the so-called "41 meV resonance" observed in inelastic neutron-scattering (INS) experiments on optimally doped Y Ba 2 Cu 3 O 6+y (YBCO) compounds in the superconducting (SC) phase [1][2][3][4][5] . The magnetic susceptibility χ ′′ (q, ω) shows a peak at the antiferromagnetic (AF) wave vector (π, π) and an energy ω 0 =41 meV . The peak appears to be resolution limited, i.e., almost undamped, and vanishes above T c . In underdoped YBCO the peak shifts to lower energies ω 0 < 41 meV [6][7][8] and develops some damping. It is also visible in the spingap regime above T c . Several theoretical approaches to the magnetic excitations have been proposed [9][10][11][12][13][14][15] . In most cases [9][10][11][12][13][14] the resonance at optimal doping is identified as a collective spin fluctuation, which is stabilized through the suppression of quasi-particle damping in the SC state, and vanishes in the normal phase. The question arises how this mode evolves with decreasing doping. In particular it is unclear how the finite damping at intermediate doping levels can be obtained, since the peak is expected to narrow and become a spin-wave (Bragg) peak at zero energy when the Néel state is reached. There is also experimental evidence [2,16] that the magnetic response in YBCO at energies somewhat below ω 0 is incommensurate. It is dominated by four peaks at q = (π, π±δ) and q = (π ± δ, π) , a pattern previously known only for the La 2−x Sr x CuO 4+y family of compounds. In view of the new experimental data, we re-investigate the spin response in slave-boson mean-field theory [9-11] , focusing on the evolution of the resonance with hole filling (doping) and the crossover commensurate-incommensurate with variation of energy.We start from the t-t'-J-model for a single CuO 2 -layer. Results specific to the bi-layer structure of YBCO will be presented elsewhere. The model readsSums include nearest neighbor (i, j) or next n.n. (i, j) ′ Cu-sites on a 2D square lattice. Physical operators c iσ = The magnetic susceptibility is calculated in ladder approximation,with J(q) = J[cos(q x )+cos(q y )] and α = 1 . Fig. 1 shows χ 0 (q, ω) , which is built of fermion bubbles with a vertex function to include all ladder diagrams. Boson excitations do not appear in l...

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With regards to the ongoing impact of the COVID-19 pandemic in the domain of entrepreneurship, we offer research-based evidence and associated insights focused on three perspectives (i.e., business planning, frugality, and emotional support) regarding entrepreneurial action under an exogenous shock. Beyond the initial emergency response that countries around the world have taken, we argue that it is time to revise entrepreneurial action guidance in such a context. Our aim is to highlight ways that entrepreneurs can take action in light of the current COVID-19 pandemic. We position our insights to be relevant to both researchers and practitioners coping with an unprecedented situation that has catastrophic consequences both economically and socially. 1. Research context The COVID-19 outbreak began with the first reporting of an unknown virus in December 2019. Within months, the outbreak had become a global crisis affecting the world both economically and socially. By March 2020, the World Health Organization (WHO) had declared the COVID-19 outbreak a pandemic. The absence of short-term medical responses to the virus (either as vaccines or treatments) has necessitated the use of lockdowns and social distancing restrictions as government tools to reduce the transmission of the virus across the population. However, the lockdowns (including, in some cases, the introduction of border controls and/or travel bans) have triggered an economic activity disruption that does not resemble any such prior demand or supply crisis. Beyond the temporal freeze of activity, there are growing concerns about the long-term effects originating with the need for lockdown protocol extensions (increasing its total duration and impact), as well as on the need to sustain behavioral rules such as social distancing to reduce the risk of new contagions. While the crisis affects all types of economic activity, the public support programs tend to prioritize and protect established organizations. And, unfortunately, the priority for the public institutions seems to be to reduce the risk of bankruptcies and destruction of * Corresponding author.

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The magnetic excitation spectrum of the t-t ′ -J-model is studied in mean-field theory and compared to inelastic neutron-scattering (INS) experiments on YBa2Cu3O6+y (YBCO) and Bi2Sr2CaCu2O 8+δ (BSCCO) superconductors. Within the slave-particle formulation the dynamical spin response is calculated from a renormalized Fermi liquid with an effective interaction ∼ J in the magnetic particle-hole channel. We obtain the so-called "41 meV resonance" at wave vector (π, π) as a collective spin-1 excitation in the d-wave superconducting state. It appears sharp (undamped), if the underlying Fermi surface is hole-like with a sufficient next-nearest-neighbor hopping t ′ < 0 . The double-layer structure of YBCO or BSCCO is not important for the resonance to form. The resonance energy ωres and spectral weight at optimal doping come out comparable to experiment. The observed qualitative behavior of ωres with hole filling is reproduced in the underdoped as well as overdoped regime. A second, much broader peak becomes visible in the magnetic excitation spectrum if the 2D wave-vector is integrated over. It is caused by excitations across the maximum gap, and in contrast to the resonance its energy is almost independent of doping. At energies above or below ωres the commensurate resonance splits into incommensurate peaks, located off (π, π) . Below ωres the intensity pattern is of "parallel" type and the dispersion relation of incommensurate peaks has a negative curvature. This is in accordance with recent INS experiments on YBCO .

This article draws on the resource-based view to analyze the role founding teams' financial management competencies play for firm growth. Prior research stressed the importance of acquiring external financial resources. In this study, we broaden the understanding of financial management in new firms. We explore the relevance of strategic financial planning competence, external financing competence, competence in financing from cash flow, and controlling competence of entrepreneurial teams for the growth of new technology-based firms. A total of 212 founding teams provided self-assessments of their financial management competencies at start-up. We apply the partial least squares approach to determine the effects of the different financial management competencies on firm growth.