On the Number of Circuit-cocircuit Reversal Classes of an Oriented Matroid

The first author introduced the circuit-cocircuit reversal system of an oriented matroid, and showed that when the underlying matroid is regular, the cardinalities of such system and its variations are equal to special evaluations of the Tutte polynomial (e.g., the total number of circuit-cocircuit reversal classes equals $t(M;1,1)$, the number of bases of the matroid). By relating these classes to activity classes studied by the first author and Las Vergnas, we give an alternative proof of the above results and a proof of the converse statements that these equalities fail whenever the underlying matroid is not regular. Hence we extend the above results to an equivalence of matroidal properties, thereby giving a new characterization of regular matroids.Comment: 7 pages. v2: simplified proof, with new statements concerning other special evaluations of the Tutte polynomia

Findings From an Accelerated _In Vivo_ Corrosion Model of Magnesium

In this article, we are presenting some findings of magnesium corrosion in an _in vivo_ model. While there is consensus that subcutaneous bubbles will occur, it was found in our corrosion-accelerated model that magnesium corrosion is more severe in areas under the gas bubbles. This finding may bring insights to novel methods in reducing the uneven corrosion

The "New Keynesian" Phillips Curve: Closed Economy vs. Open Economy

The paper extends Woodford's (2000) analysis of the closed economy Phillips curve to an open economy with both commodity trade and capital mobility. We show that consumption smoothing, which comes with the opening of the capital market, raises the degree of strategic complementarity among monopolistically competitive suppliers, thus rendering prices more sticky and magnifying output responses to nominal GDP shocks.

A Dynamic General Equilibrium Framework of Investment with Financing Constraint

In this paper, we provide a dynamic general equilibrium framework with an explicit investment-financing constraint. The constraint is intended as a reduced form to capture the balance sheet effects that have been widely regarded as an important determinant of financial crises. We derive a link between the value of the firm and social welfare. We find that the value of the firm can be greater with the constraint. Our model also sheds light on how the effects of productivity shocks and investors' misperception of productivity shocks may be amplified by the financing constraint.Investment Constraint, Value of the Firm

Understanding the "Problem of Economic Development": The Role of Factor Mobility and International Taxation

The problem of economic development, as Lucas (1988) states it, is the problem of accounting for the observed diversity in levels and rates of growth of per capita income across countries and across time. We study conditions under which capital mobility and labor mobility (two seemingly income-equalizing forces) may interact with cross-country differences in income tax rates and income tax principles (two seemingly income-diverging forces) to generate such diversity. As a corollary, we also examine when countries with different initial endowments may finally converge in their income levels.

A Dynamic General Equilibrium Framework of Investment with Financing Constraint

In this paper, we provide a dynamic general equilibrium framework with an explicit investment-financing constraint. The constraint is intended as a reduced form to capture the balance sheet effects that have been widely regarded as an important determinant of financial crises. We derive a link between the value of a firm and social welfare. Using this link, we show the somewhat surprising possibility that the value of a firm can be greater with the constraint. Our model also sheds light on how the effects of productivity shocks and investors' misperception of productivity shocks may be amplified by the financing constraint. Copyright 2003, International Monetary Fund

Capital Income Taxation and Long Run Growth: New Perspectives

We study the effects of capital income taxation on long run growth in an endogenous growth framework with two distinguishing features: endogenous population and international capital mobility. Endogenizing population growth introduces a new channel for taxes to affect economic growth and enables us to discriminate the effects of taxes on total versus per capita income growth. Allowing for capital mobility in the open economy, we show how the effects of taxes on population growth and income growth across countries will vary in specific ways, depending on the international income tax regimes and the relative preference bias of people towards the 'quantity' and 'quality' of children. The numerical results based on our calibrated model for the G-7 also indicate that, although the effects of liberalizing capital flows on long run growth may not be very sizable, the growth effects of changes in capital income tax rates can be tremendously magnified by cross-border capital flows and cross-border spillovers of policy effects.

The dimension of an amoeba

Answering a question by Nisse and Sottile, we derive a formula for the dimension of the amoeba of an irreducible algebraic variety.Comment: 8 pages, several small improvements, final versio