Pair-distribution functions of two-temperature two-mass systems: Comparison of MD, HNC, CHNC, QMC and Kohn-Sham calculations for dense hydrogen

Two-temperature, two-mass quasi-equilibrium plasmas may occur in electron-ion plasmas,nuclear-matter, as well as in electron-hole condensed-matter systems. Dense two-temperature hydrogen plasmas straddle the difficult partially - degenerate regime of electron densities and temperatures which are important in astrophysics, in inertial-confinement fusion research, and other areas of warm dense matter physics. Results from Kohn-Sham calculations and QMC are used to benchmark the procedures used in classical molecular-dynamics simulations, HNC and CHNC methods to derive electron-electron and electron-proton pair - distribution functions. Then, nonequilibrium molecular dynamics for two -temperature, two-mass plasmas are used to obtain the pair distribution. Using these results, the correct HNC and CHNC procedures for the evaluation of pair-distribution functions in two-temperature two-mass two-component charged fluids are established. Results for a mass ratio of 1:5, typical of electron-hole fluids, as well as for compressed hydrogen are presented. PACS Numbers: 52.25.Kn, 52.25Gj, 71.10.-w, 52.27.Gr, 26.30.+kComment: 17 pages, four figure

Non-hermitian approach to decaying ultracold bosonic systems

A paradigm model of modern atom optics is studied, strongly interacting ultracold bosons in an optical lattice. This many-body system can be artificially opened in a controlled manner by modern experimental techniques. We present results based on a non-hermitian effective Hamiltonian whose quantum spectrum is analyzed. The direct access to the spectrum of the metastable many-body system allows us to easily identify relatively stable quantum states, corresponding to previously predicted solitonic many-body structures

Corporate Financial and Investment Policies when Future Financing is not Frictionless

Much of corporate finance is concerned with the impact of financing constraints on firms. However, the literature on financing constraints largely ignores the intertemporal implications of those constraints; in particular, how future financing constraints affect current investment decisions. We present a model in which future financing constraints lead firms to have a current preference for investments with shorter payback periods, investments with less risk, and investments that utilize more liquid/pledgeable assets. The model has a host of implications in different areas of corporate finance, including firms' capital budgeting rules, risk-taking behavior, capital structure choices, hedging strategies, and cash management policies. We show how a number of patterns reported in the empirical literature can be reconciled and interpreted in light of the intertemporal optimization problem firms solve when they face costly external financing. For example, contrary to Jensen and Meckling (1976), we show that firms may reduce rather than increase risk when leverage increases exogenously. Furthermore, firms in economies with less developed financial markets will not only take different quantities of investment, but will also take different kinds of investment (safer, short-term projects that are potentially less profitable). We also point out to several predictions that have not been empirically examined. For example, our model predicts that investment safety and liquidity are complementary: constrained firms are specially likely to distort the risk profile of their most liquid investments.

Corporate Demand for Liquidity

This paper proposes a theory of corporate liquidity demand and provides new evidence on corporate cash policies. Firms have access to valuable investment opportunities, but potentially cannot fund them with the use of external finance. Firms that are financially unconstrained can undertake all positive NPV projects regardless of their cash position, so their cash positions are irrelevant. In contrast, firms facing financial constraints have an optimal cash position determined by the value of today's investments relative to the expected value of future investments. The model predicts that constrained firms will save a positive fraction of incremental cash flows, while unconstrained firms will not. We also consider the impact of Jensen (1986) style overinvestment on the model's equilibrium, and derive conditions under which overinvestment affects corporate cash policies. We test the model's implications on a large sample of publicly-traded manufacturing firms over the 1981-2000 period, and find that firms classified as financially constrained save a positive fraction of their cash flows, while firms classified as unconstrained do not. Moreover, constrained firms save a higher fraction of cash inflows during recessions. These results are robust to the use of alternative proxies for financial constraints, and to several changes in the empirical specification. We also find weak evidence consistent with our agency-based model of corporate liquidity.

Legal Legitimacy of Tax Recommendations Delivered by the IMF in the Context of 'Article IV Consultations'

This contribution examines the legal legitimacy of 'Article IV Consultations' performed by the IMF as part of its responsibility for surveillance under Article IV of its Articles of Agreement. The analysis focuses on tax recommendations given by the Fund to its member countries in the context of Consultations. This paper determines that these tax recommendations derive from a broad interpretation of the powers and obligations that have been agreed to in the Fund’s Articles of Agreement. Such an interpretation leads to a legitimacy deficit, as member countries of the Fund have not given their state consent to receive recommendations as to which should be the tax policies it should adopt

Patterns of interstate migration in the United States from the survey of income and program participation

The authors describe the Survey of Income and Program Participation (SIPP) as a data source for migration studies. The SIPP is a panel dataset that provides information on income, employment outcomes, and participation in government programs. Survey participants are interviewed for up to four years even if they move to a new household or that household migrates within the United States. This unique longitudinal design gives the survey a strong advantage over traditional data sources. The authors illustrate differences in the propensity for interstate migration among different demographic groups over the 12-year period from 1996 to 2008. They also analyze the relationship between migration choices and life-changing events, such as becoming jobless or dissolution of a marriage. Their findings suggest that future research should consider the migration choices of individuals near retirement age.Demography ; Income ; Emigration and immigration