Further Evidence for a Gravitational Fixed Point

A theory of gravity with a generic action functional and minimally coupled to N matter fields has a nontrivial fixed point in the leading large N approximation. At this fixed point, the cosmological constant and Newton's constant are nonzero and UV relevant; the curvature squared terms are asymptotically free with marginal behaviour; all higher order terms are irrelevant and can be set to zero by a suitable choice of cutoff function.Comment: LaTEX, 4 pages. Relative to the published paper, a sign has been corrected in equations (17) and (18

Mapping Prices into Productivity in Multisector Growth Models

Two issues related to mapping a multi-sector model into a reduced-form value-added model are often neglected: the composition of intermediate goods, and the distinction between value added productivity and gross output productivity. We demonstrate their quantitative significance for the case of the well known model of Greenwood, Hercowitz and Krusell (1997), who find that about 60% of economic growth can be attributed to investment-specific technical change (ISTC). When we recalibrate their model to allow for even a small equipment share of intermediates, we find that ISTC accounts for almost the entirety of postwar US growth.Intermediate goods, investment-specific technical change, growth accounting, gross output, multisector growth models

Identifying Social Norms Using Coordination Games: Why Does Dictator Game Sharing Vary?

We explore the influence of social norms on behavior. To do so, we introduce a method for identifying norms, based on the property that social norms reflect social consensus regarding the appropriateness of different possible behaviors. We demonstrate that the norms we elicit, along with a simple model combining concern for norm-compliance with utility for money, predict changes in behavior across several variants of the dictator game in which behavior changes substantially following the introduction of minor contextual variations. Our findings indicate that people care not just about monetary payoffs but also care about the social appropriateness of any action they take. Our work also suggests that a social norm is not always a single action that should or should not be taken, but rather a profile of varying degrees of social appropriateness for different available actions.norms, matching games, dictator games

An R&D-Based Model of Multi-Sector Growth

We develop a multi-sector general equilibrium model in which productivity growth is driven by the production of sector-specific knowledge. In the model, we find that long run differences in total factor productivity growth across sectors are independent of the parameters of the knowledge production function except for one, which we term the fertility of knowledge. Differences in R&D intensity are also independent of most other parameters. The fertility of knowledge in the capital sector is central to the growth properties of the model economy.Endogenous technical change, multisector growth, fertility of knowledge, total factor productivity, R&D intensity, investment-specific technical change

Accounting for Research and Productivity Growth Across Industries

What factors underlie industry differences in research intensity and productivity growth? We develop a multi-sector endogenous growth model allowing for industry specific parameters in the production functions for output and knowledge, and in consumer preferences. We find that industry differences in both productivity growth and R&D intensity mainly reflect differences in "technological opportunities", interpreted as parameters of knowledge production. These include the capital intensity of R&D, knowledge spillovers, and diminishing returns to R&D. Among these parameters, we find that the degree of diminishing returns to R&D is the dominant factor when the model is calibrated to account for crossindustry differences in the US.Multisector growth, total factor productivity, R&D intensity, technological opportunity

The impulsive phase of magnetar giant flares: assessing linear tearing as the trigger mechanism

Giant $\gamma$-ray flares comprise the most extreme radiation events observed from magnetars. Developing on (sub)millisecond timescales and generating vast amounts of energy within a fraction of a second, the initial phase of these extraordinary bursts present a significant challenge for candidate trigger mechanisms. Here we assess and critically analyse the linear growth of the relativistic tearing instability in a globally twisted magnetosphere as the trigger mechanism for giant $\gamma$-ray flares. Our main constraints are given by the observed emission timescales, the energy output of the giant flare spike, and inferred dipolar magnetic field strengths. We find that the minimum growth time of the linear mode is comparable to the $e$-folding rise time, i.e. $\sim10^{-1}$ ms. With this result we constrain basic geometric parameters of the current sheet. We also discuss the validity of the presumption that the $e$-folding emission timescale may be equated with the growth time of an MHD instability.Comment: 15 pages, 4 figures, MNRAS in pres