A tractable model of buffer stock saving

We present a tractable model of the effects of nonfinancial risk on intertemporal choice. Our purpose is to provide a simple framework that can be adopted in fields like representative-agent macroeconomics, corporate finance, or political economy, where most modelers have chosen not to incorporate serious nonfinancial risk because available methods were too complex to yield transparent insights. Our model produces an intuitive analytical formula for target assets, and we show how to analyze transition dynamics using a familiar Ramsey-style phase diagram. Despite its starkness, our model captures most of the key implications of nonfinancial risk for intertemporal choice

Life events and acute cardiovascular reactions to mental stress: a cohort study

Objective: This study addressed the issue of whether frequent exposure to life events is associated with aggravation or blunting of cardiovascular reactions to acute mental stress. Methods: In a substantial cohort of 585 healthy young adults, systolic and diastolic blood pressure and pulse rate were recorded at rest and in response to a mental arithmetic stress task. Participants indicated, from a list of 50 events, those they had experienced in the last year. Results: There was an overall association between life events and blunted cardiovascular reactivity that was driven by variations in the frequency of exposure to desirable events. The total number of events and the number of personal events were negatively associated with systolic blood pressure and pulse rate reactions to acute stress, whereas the number of work-related events was negatively associated with diastolic blood pressure and pulse rate reactivity. The negative association between total events and systolic blood pressure reactivity was stronger for women than men, whereas men exposed to frequent undesirable events showed enhanced diastolic blood pressure reactivity. The blunting of pulse rate reactivity associated with frequent personal life events was evident particularly for those who had a relatively large number of close friends. Conclusions: The nature and extent of the association between life events exposure and stress reactivity in young adults depends on the valence of the events together with the sex of the individual and their social network size

Koontz v. St. Johns River Water Management District: Can Environmental Impact Analysis Preserve Sustainable Development from the New Reach of the Supreme Court\u27s Exactions Jurisprudence?

The United States Supreme Court has raised the legal standard for a municipality to use land use exactions for sustainable development. Land use exactions frequent local government affairs and occur when a government demands a dedication of land or money in exchange for a municipal approval, such as a permit. Koontz v. St. Johns River Water Management District found certain proposed government exactions for land use permits as “demands” on the applicant and required a “‘nexus\u27 and ‘rough proportionality’ between the property that the government demands and the social costs of the applicant\u27s proposal,” regardless of whether the exaction was a condition precedent or a condition subsequent. Even without incurring a “takings” for purposes of the Fifth and Fourteenth Amendments to the United States Constitution, if government-imposed exactions are found to be “[e]xtortionate demand[s],” this would still “run afoul of the Takings Clause not because they take property but because they impermissibly burden the right not to have property taken without just compensation.” Thus, if there is no “essential nexus” and “rough proportionality,” the exaction is an actionable “unconstitutional condition.” After Koontz, this standard now applies even if an applicant has only been asked to make payments to improve public land. However, this comment argues that municipalities can use environmental impact review to shield themselves from the threat of uncertain, broad, and costly litigation during negotiations with developers. Part II of this paper discusses the import of municipal exactions to environmental stewardship and sustainable development. Part III provides an overview of the Unconstitutional Conditions Doctrine, which played a decisive role in the Koontz case. Part IV centers around the majority and dissenting opinions in Koontz, as well as the issues settled, and those now raised, by the Court\u27s ruling. Part V analyzes the New York State Environmental Quality Review Act (SEQRA) and focuses on its procedural and substantive requirements. Comparative treatment is also given to the environmental review statutes in the States of California and Washington. Part VI concentrates on case illustrations that reveal how these statutes satisfy the Unconstitutional Conditions Doctrine, as extended by Koontz. This Part focuses chiefly on SEQRA, but also explores possible outcomes under its analogous state counterparts. Part VII concludes with potential ramifications for local environmental law and sustainable development

Yang-Mills Instantons with Lorentz Violation

An analysis is performed of instanton configurations in pure Euclidean Yang-Mills theory containing small Lorentz-violating perturbations that maintain gauge invariance. Conventional topological arguments are used to show that the general classification of instanton solutions involving the topological charge is the same as in the standard case. Explicit solutions are constructed for general gauge invariant corrections to the action that are quadratic in the curvature. The value of the action is found to be unperturbed to lowest order in the Lorentz-violating parameters.Comment: 16 page

High-fidelity single-shot readout for a spin qubit via an enhanced latching mechanism

The readout of semiconductor spin qubits based on spin blockade is fast but suffers from a small charge signal. Previous work suggested large benefits from additional charge mapping processes, however uncertainties remain about the underlying mechanisms and achievable fidelity. In this work, we study the single-shot fidelity and limiting mechanisms for two variations of an enhanced latching readout. We achieve average single-shot readout fidelities > 99.3% and > 99.86% for the conventional and enhanced readout respectively, the latter being the highest to date for spin blockade. The signal amplitude is enhanced to a full one-electron signal while preserving the readout speed. Furthermore, layout constraints are relaxed because the charge sensor signal is no longer dependent on being aligned with the conventional (2, 0) - (1, 1) charge dipole. Silicon donor-quantum-dot qubits are used for this study, for which the dipole insensitivity substantially relaxes donor placement requirements. One of the readout variations also benefits from a parametric lifetime enhancement by replacing the spin-relaxation process with a charge-metastable one. This provides opportunities to further increase the fidelity. The relaxation mechanisms in the different regimes are investigated. This work demonstrates a readout that is fast, has one-electron signal and results in higher fidelity. It further predicts that going beyond 99.9% fidelity in a few microseconds of measurement time is within reach.Comment: Supplementary information is included with the pape

Fragment properties at the catastrophic disruption threshold: The effect of the parent body's internal structure

Numerical simulations of asteroid break-ups, including both the fragmentation of the parent body and the gravitational interactions between the fragments, have allowed us to reproduce successfully the main properties of asteroid families formed in different regimes of impact energy, starting from a non-porous parent body. In this paper, using the same approach, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by Q*D, which results in the escape of half of the target's mass. Thanks to our recent implementation of a model of fragmentation of porous materials, we can characterize Q*D for both porous and non-porous targets with a wide range of diameters. We can then analyze the potential influence of porosity on the value of Q*D, and by computing the gravitational phase of the collision in the gravity regime, we can characterize the collisional outcome in terms of the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. We also check the dependency of Q*D on the impact speed of the projectile. In the strength regime, which corresponds to target sizes below a few hundreds of meters, we find that porous targets are more difficult to disrupt than non-porous ones. In the gravity regime, the outcome is controlled purely by gravity and porosity in the case of porous targets. In the case of non-porous targets, the outcome also depends on strength. We then propose some power-law relationships between Q*D and both target's size and impact speed that can be used in collisional evolution models.Comment: 18 pages, 19 Figures. Accepted for publication in Icaru

The geometry of thermodynamic control

A deeper understanding of nonequilibrium phenomena is needed to reveal the principles governing natural and synthetic molecular machines. Recent work has shown that when a thermodynamic system is driven from equilibrium then, in the linear response regime, the space of controllable parameters has a Riemannian geometry induced by a generalized friction tensor. We exploit this geometric insight to construct closed-form expressions for minimal-dissipation protocols for a particle diffusing in a one dimensional harmonic potential, where the spring constant, inverse temperature, and trap location are adjusted simultaneously. These optimal protocols are geodesics on the Riemannian manifold, and reveal that this simple model has a surprisingly rich geometry. We test these optimal protocols via a numerical implementation of the Fokker-Planck equation and demonstrate that the friction tensor arises naturally from a first order expansion in temporal derivatives of the control parameters, without appealing directly to linear response theory

The Stone Fireplaces of Denendeh

Stone fireplaces and chimneys have been documented in nineteenth century Indigenous settlement sites in the Northwest Territories. The cabin and chimney designs were adapted by Dene craftsmen based on examples they encountered when engaging with Euro-Canadian traders and explorers. The Indigenous cabins and chimneys were built during a period of transition in Dene culture, at a time when they began the process of integrating into a fur trade economy. The chimneys and cabins are elements of Euro-Canadian vernacular architecture adapted by Indigenous people in the north. The Indigenous cabins and chimneys are an example of cultural diffusion and, in some instances, might have also been expressions of social status. Together, the Indigenous stone chimneys and the extant chimney features at Fort Confidence and Fort Reliance in the Northwest Territories are part of a shared architectural heritage.