719 research outputs found
Money in Motion: Dynamic Portfolio Choice in Retirement
Retirees confront the difficult problem of how to manage their money in retirement so as to not outlive their funds while continuing to invest in capital markets. We posit a dynamic utility maximizer who makes both asset location and allocation decisions when managing her retirement financial wealth and annuities, and we prove that she can benefit from both the equity premium and longevity insurance in her retirement portfolio. Even without bequests, she will not fully annuitize; rather, her optimal stock allocation amounts initially to more than half of her financial wealth and declines with age. Welfare gains from this strategy can amount to 40 percent of financial wealth (depending on risk parameters and other resources). In practice, it turns out that many retirees will do almost as well by purchasing a variable annuity invested 60/40 in stocks/bonds.
Asset Allocation and Location over the Life Cycle with Survival-Contingent Payouts
This paper shows how lifelong survival-contingent payouts can enhance investor wellbeing in the context of a portfolio choice model which integrates uninsurable labor income and asymmetric mortality expectations. Our model generates optimal asset location patterns indicating how much to hold in liquid versus illiquid survival-contingent payouts over the lifetime, and also asset allocation paths, showing how to invest in stocks versus bonds. We conrm that the investor will gradually move money out of her liquid saving into survivalcontingent assets to retirement and beyond, thereby enhancing her welfare by as much as 50 percent. The results are also robust to the introduction of uninsurable consumption shocks in housing expenses, income flows during the worklife and retirement, sudden changes in health status, and medical expenses.
Development of algebraic techniques for the atomic open-shell MBPT(3)
The atomic third-order open-shell many-body perturbation theory is developed.
Special attention is paid to the generation and algebraic analysis of terms of
the wave operator and the effective Hamiltonian as well. Making use of
occupation-number representation and intermediate normalization, the
third-order deviations are worked out by employing a computational software
program that embodies the generalized Bloch equation. We prove that in the most
general case, the terms of effective interaction operator on the proposed
complete model space are generated by not more than eight types of the -body
() parts of the wave operator. To compose the effective Hamiltonian
matrix elements handily, the operators are written in irreducible tensor form.
We present the reduction scheme in a versatile disposition form, thus it is
suited for the coupled-cluster approach
The Hubbard model on a complete graph: Exact Analytical results
We derive the analytical expression of the ground state of the Hubbard model
with unconstrained hopping at half filling and for arbitrary lattice sites.Comment: Email:[email protected]
SIMP (Strongly Interacting Massive Particle) Search
We consider laboratory experiments that can detect stable, neutral strongly
interacting massive particles (SIMPs). We explore the SIMP annihilation cross
section from its minimum value (restricted by cosmological bounds) to the barn
range, and vary the mass values from a GeV to a TeV. We also consider the
prospects and problems of detecting such particles at the Tevatron.Comment: Latex. 7 pages, 1 eps figure. Proceedings to the 4th UCLA Symposium
on Dark Matter DM2000, Marina del Rey, CA, USA, Feb. 23-25, 200
Wind-induced ground motion: dynamic model and non-uniform structure for ground
Wind-induced ground vibrations are a source of noise in seismic surveys. In a previous study, a wind-ground coupling theory was developed to predict the power spectral density (PSD) of ground motions caused by wind perturbations on the ground surface. The prediction was developed using a superposition of the point source response of an elastic isotropic homogeneous medium deforming quasi-statically with the statistical description of the wind-induced pressure fluctuations on the ground. Model predictions and field measurements were in agreement for the normal component of the displacement but under predicted the horizontal component. In this paper, two generalizations are investigated to see if they lead to increased horizontal displacement predictions: 1. First, the dynamic point source response is calculated and incorporated in the ground displacement calculation. Measured ground responses are used to incorporate losses into the dynamic calculation. 2. The quasi-static response function for three different types of non-uniform grounds are calculated and used in the seismic wind noise superposition. The dynamic point source response and the three more realistic ground models result in larger horizontal displacements for the point source at distances on the order of 1 m or greater from the source. However, the superposition to predict the seismic wind noise is dominated by the displacements very close to the point source where the prediction is unchanged. This research indicates that the modeling of the wind-induced pressure source distribution must be improved to predict the observed equivalency of the vertical and horizontal displacements
Asset Allocation and Location over the Life Cycle with Survival-Contingent Payouts
This paper shows how lifelong survival-contingent payouts can enhance investor wellbeing in the context of a portfolio choice model which integrates uninsurable labor income and asymmetric mortality expectations. Our model generates optimal asset location patterns indicating how much to hold in liquid versus illiquid survival-contingent payouts over the lifetime, and also asset allocation paths, showing how to invest in stocks versus bonds. We confirm that the investor will gradually move money out of her liquid saving into survival-contingent assets to retirement and beyond, thereby enhancing her welfare by as much as 50 percent. The results are also robust to the introduction of uninsurable consumption shocks in housing expenses, income flows during the worklife and retirement, sudden changes in health status, and medical expenses.
New method to study stochastic growth equations: a cellular automata perspective
We introduce a new method based on cellular automata dynamics to study
stochastic growth equations. The method defines an interface growth process
which depends on height differences between neighbors. The growth rule assigns
a probability exp for a site to
receive one particle at a time and all the sites are updated
simultaneously. Here and are two parameters and
is a function which depends on height of the site and its neighbors. Its
functional form is specified through discretization of the deterministic part
of the growth equation associated to a given deposition process. In particular,
we apply this method to study two linear equations - the Edwards-Wilkinson (EW)
equation and the Mullins-Herring (MH) equation - and a non-linear one - the
Kardar-Parisi-Zhang (KPZ) equation. Through simulations and statistical
analysis of the height distributions of the profiles, we recover the values for
roughening exponents, which confirm that the processes generated by the method
are indeed in the universality classes of the original growth equations. In
addition, a crossover from Random Deposition to the associated correlated
regime is observed when the parameter is varied.Comment: 6 pages, 7 figure
Comparison of Non-human Primate versus Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Treatment of Myocardial Infarction.
Non-human primates (NHPs) can serve as a human-like model to study cell therapy using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). However, whether the efficacy of NHP and human iPSC-CMs is mechanistically similar remains unknown. To examine this, RNU rats received intramyocardial injection of 1 × 107 NHP or human iPSC-CMs or the same number of respective fibroblasts or PBS control (n = 9-14/group) at 4 days after 60-min coronary artery occlusion-reperfusion. Cardiac function and left ventricular remodeling were similarly improved in both iPSC-CM-treated groups. To mimic the ischemic environment in the infarcted heart, both cultured NHP and human iPSC-CMs underwent 24-hr hypoxia in vitro. Both cells and media were collected, and similarities in transcriptomic as well as metabolomic profiles were noted between both groups. In conclusion, both NHP and human iPSC-CMs confer similar cardioprotection in a rodent myocardial infarction model through relatively similar mechanisms via promotion of cell survival, angiogenesis, and inhibition of hypertrophy and fibrosis
Optical absorption in semiconductor quantum dots: Nonlocal effects
The optical absorption of a single spherical semiconductor quantum dot in an
electrical field is studied taking into account the nonlocal coupling between
the field of the light and the polarizability of the semiconductor. These
nonlocal effects lead to a small size anf field dependent shift and broadening
of the excitonic resonance which may be of interest in future high precision
experiments.Comment: 6 pages, 4 figure
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