Charge Density Wave Ratchet

We propose to operate a locally-gated charge density wave as an electron pump. Applying an oscillating gate potential with frequency $f$ causes equally spaced plateaux in the sliding charge density wave current separated by $\Delta I=2eNf,$ where $N$ is the number of parallel chains. The effects of thermal noise are investigated.Comment: To be published in Applied Physics Letter

Paths to prosperity: knowledge is key for Fourth District states

Even as per capita income has increased across the United States, differences among states’ incomes remain. What are the sources of these remaining differences? This Commentary identifies and analyzes the key factors—patents, educational attainment, and industry structure—that influence income-growth rates and thus per capita incomes. It also explores where the Fourth District falls in relation to other states and the country as a whole.Economic development ; Income ; Education - Economic aspects

Normative characterization in biological and cognitive explanations

Normative characterization is a commonplace feature of biological and cognitive explanation. Such language seems to commit the biological and cognitive sciences to the existence of natural norms, but it is also difficult to understand how such normativity fits into a natural world of physical causes and forces. Existing models for how such language can have a legitimate causal-explanatory role in the sciences are, I think, unsatisfactory.  I suggest an alternative model in which normativity is mapped onto systems stabilized by counteractive constraints. Such a mapping, I propose, explains normativity’s causal-explanatory role in biological and cognitive inquiry. ; La caracterización normativa es un rasgo común de las explicaciones biológicas y cognitivas. Ese lenguaje parece comprometer a las ciencias biológicas y cognitivas con la existencia de normas naturales, pero es difícil entender cómo dicha normatividad encaja en un mundo natural de fuerzas y causas físicas. Propongo representar la normatividad en sistemas estabilizados mediante condicionamientos opuestos. Esta representación, en mi opinión, puede explicar el rol explicativo-causal de la normatividad en la investigación biológica y cognitiva. Lo usual en la literatura sobre el tema consiste en derivar una explicación de la normatividad natural a partir de una teoría particular sobre la noción de función. Esquivaré este planteamiento e intentaré abordar directamente el tipo de sistemas físicos que podrían satisfacer criterios naturalizadores de la normatividad. Esto tiene las ventajas, pienso, de que permite una explicación de la normatividad sin tener que decidir primero la teoría correcta de la función, y en segundo lugar, queda abierta la posibilidad teórica de que la explicación normativa y funcional puedan tratarse separadamente dentro de la explicación empírica

Normative Characterization in Biological and Cognitive Explanations

Normative characterization is a commonplace feature of biological and cognitive explanation. Such lan- guage seems to commit the biological and cognitive sciences to the existence of natural norms, but it is also difficult to understand how such normativity fits into a natural world of physical causes and forces. I propose to map normativity onto systems stabilized by counteractive constraints. Such a mapping, I believe, can explain normativity’s causal-explanatory role in biological and cognitive inquiry. The common approach in the literature is to derive an account of natural normativity by way of a particular theory of function. I avoid that approach here and attempt to address directly the sort of physical systems that might satisfy naturalizing criteria for normativity. This has the advantages, I think, of allowing an account of normativity without first having to decide the correct theory of function as well as allowing for the theoretical possibility that normative and functional explanation might come apart within empirical explanation

State growth empirics: the long-run determinants of state income growth

Real average U.S. per capita personal income growth over the last 65 years exceeded a remarkable 400 percent. Also notable over this period is that the stark income differences across states have narrowed considerably: In 1939 the highest income state’s per capita personal income was 4.5 times the lowest, but by 1976 this ratio had fallen to less than 2 times. Since 1976, the standard deviation of per capita incomes at the state level has actually risen, as some higher-income states have seen their income levels rise relative to the median of the states. A better understanding of the sources of these relative growth performances should help to characterize more effective economic development strategies, if income growth differences are predictable. In this paper, we look for statistically and economically significant growth factors by estimating an augmented growth model using a panel of the 48 contiguous states from 1939 to 2004. Specifically, we control for factors that previous researchers have argued were important: tax burdens, public infrastructure, size of private financial markets, rates of business failure, industry structure, climate, and knowledge stocks. Our results, which are robust to a wide variety of perturbations to the model, are easily summarized: A state’s knowledge stocks (as measured by its stock of patents and its high school and college attainment rates) are the main factors explaining a state’s relative per capita personal income.Economic development ; Income ; Education - Economic aspects