Endogenous Sampling in Duration Models

This paper considers the problem of endogenous sampling in the duration model. This is an important problem in the duration analysis of bank failures and loan defaults because it is common for the researchers in these areas to use only the default sample or non-default sample or both at a certain ratio, rather than using a random sample. The properties of endogenous sampling have been considered in various models, notably in qualitative response models, but not in duration models as far as I am aware. In this paper, I obtain the asymptotic distribution of the endogenous sampling maximum likelihood estimator and compare it with that of the random sampling maximum likelihood estimator and indicate when efficiency gain may result. I also show that the random sampling maximum likelihood estimator is inconsistent if the data are collected by endogenous sampling.

Quark Confinement Physics in Quantum Chromodynamics

We study abelian dominance and monopole condensation for the quark confinement physics using the lattice QCD simulations in the MA gauge. These phenomena are closely related to the dual superconductor picture of the QCD vacuum, and enable us to construct the dual Ginzburg-Landau (DGL) theory as an useful effective theory of nonperturbative QCD. We then apply the DGL theory to the studies of the low-lying hadron structure and the scalar glueball properties.Comment: Talk given at 15th International Conference on Particle and Nuclei (PANIC 99), Uppsala, Sweden, 10-16 Jun 1999, 4 page

Endogenous Sampling and Matching Method in Duration Models

Endogenous sampling with matching (also called gmixed samplingh) occurs when the statistician samples from the non-right- censored subset at a predetermined proportion and matches on one or more exogenous variables when sampling from the right-censored subset. This is widely applied in the duration analysis of firm failures, loan defaults, insurer insolvencies, and so on, due to the low frequency of observing non-right-censored samples (bankrupt, default, and insolvent observations in respective examples). However, the common practice of using estimation procedures intended for random sampling or for the qualitative response model will yield either an inconsistent or inefficient estimator. This paper proposes a consistent and efficient estimator and investigates its asymptotic properties. In addition, this paper evaluates the magnitude of asymptotic bias when the model is estimated as if it were a random sample or an endogenous sample without matching. This paper also compares the relative efficiency of other commonly used estimators and provides a general guideline for optimally choosing sample designs. The Monte Carlo study with a simple example shows that random sampling yields an estimator of poor finite sample properties when the population is extremely unbalanced in terms of default and non-default cases while endogenous sampling and mixed sampling are robust in this situation.Duration models; Endogenous sampling with matching; Maximum likelihood estimator; Manski-Lerman estimator; Asymptotic distribution

D3-brane from D-instantons in the hybrid formalism of superstring

A Dp-brane can be regarded as a configuration of infinitely many D(p-2k)-branes in bosonic string. We will show this property of D-branes in the superstring case using the hybrid formalism. It is convenient to study the boundary state for such D-branes to study such property between D-branes. We show that the boundary state for a D3-brane in a constant self-dual gauge field background can be expressed in terms of the boundary state for D-instantons in the hybrid formalism.Comment: 10 pages, minor corrections, reference adde

Magnetization Losses in Multifilament Coated Superconductors

We report the results of a study of the magnetization losses in experimental multifilament, as well as control (uniform), coated superconductors exposed to time-varying magnetic field of various frequencies. Both the hysteresis loss, proportional to the sweep rate of the applied magnetic field, and the coupling loss, proportional to the square of the sweep rate, have been observed. A scaling is found that allows us to quantify each of these contributions and extrapolate the results of the experiment beyond the envelope of accessible field amplitude and frequency. The combined loss in the multifilament conductor is reduced by about 90% in comparison with the uniform conductor at full field penetration at sweep rate as high as 3T/s