cssi/SciSciGPT-SciSciNet huggingface dataset:
A geometric interpretation of the permutation p-value and its application in eQTL studies

Permutation p-values have been widely used to assess the significance of linkage or association in genetic studies. However, the application in large-scale studies is hindered by a heavy computational burden. We propose a geometric interpretation of permutation p-values, and based on this geometric interpretation, we develop an efficient permutation p-value estimation method in the context of regression with binary predictors. An application to a study of gene expression quantitative trait loci (eQTL) shows that our method provides reliable estimates of permutation p-values while requiring less than 5% of the computational time compared with direct permutations. In fact, our method takes a constant time to estimate permutation p-values, no matter how small the p-value. Our method enables a study of the relationship between nominal p-values and permutation p-values in a wide range, and provides a geometric perspective on the effective number of independent tests.
Eynard–Mehta Theorem, Schur Process, and their Pfaffian Analogs

We give simple linear algebraic proofs of the Eynard–Mehta theorem, the Okounkov-Reshetikhin formula for the correlation kernel of the Schur process, and Pfaffian analogs of these results. We also discuss certain general properties of the spaces of all determinantal and Pfaffian processes on a given finite set.
Compact wavefunctions from compressed imaginary time evolution

Simulation of quantum systems promises to deliver physical and chemical predictions for the frontiers of technology. In this work, we introduce a general and efficient black box method for many-body quantum systems using technology from compressed sensing to find compact wavefunctions without detailed knowledge of the system. No knowledge is assumed in the structure of the problem other than correct particle statistics. As an application, we use this technique to compute ground state electronic wavefunctions of hydrogen fluoride and recover 98% of the basis set correlation energy or equivalently 99.996% of the total energy with 50 configurations out of a possible 107.
Pandeia: a multi-mission exposure time calculator for JWST and WFIRST

Pandeia is the exposure time calculator (ETC) system developed for the James Webb Space Telescope (JWST) that will be used for creating JWST proposals. It includes a simulation-hybrid Python engine that calculates the two-dimensional pixel-by-pixel signal and noise properties of the JWST instruments. This allows for appropriate handling of realistic point spread functions, MULTIACCUM detector readouts, correlated detector readnoise, and multiple photometric and spectral extraction strategies. Pandeia includes support for all the JWST observing modes, including imaging, slitted/slitless spectroscopy, integral field spectroscopy, and coronagraphy. Its highly modular, data-driven design makes it easily adaptable to other observatories. An implementation for use with WFIRST is also available.
Fourier Response of a Memristor: Generation of High Harmonics With Increasing Weights

We investigate the Fourier transform (FT) of the current through a memristor with an alternating-current voltage whose frequency is smaller than the characteristic memristor frequency. When the resultant hysteresis curve in the current-voltage plane is “smooth,” the current transform has weights at odd and even harmonics that decay rapidly and monotonically with the order of the harmonic. We find that, when the hysteresis curve is “sharp,” the FT is significantly broad, with increasing weights at high harmonics. We present a simple model that shows that this qualitative change in the Fourier spectrum is solely driven by the saturation of memristance during a voltage cycle and not independently by various system parameters, such as applied or memristor frequencies, or the nonlinear dopant drift. Our model predicts that maximal-weight higher harmonics occur most easily in a memristor with a sine voltage and positive polarity.
A characterization of superreflexivity through embeddings of lamplighter groups

We prove that finite lamplighter groups $\{\mathbb{Z}_2\wr\mathbb{Z}_n\}_{n\ge 2}$ with a standard set of generators embed with uniformly bounded distortions into any non-superreflexive Banach space, and therefore form a set of test-spaces for superreflexivity. Our proof is inspired by the well known identification of Cayley graphs of infinite lamplighter groups with the horocyclic product of trees. We cover $\mathbb{Z}_2\wr\mathbb{Z}_n$ by three sets with a structure similar to a horocyclic product of trees, which enables us to construct well-controlled embeddings.
Diffusion in translucent media

Diffusion is the result of repeated random scattering. It governs a wide range of phenomena from Brownian motion, to heat flow through window panes, neutron flux in fuel rods, dispersion of light in human tissue, and electronic conduction. It is universally acknowledged that the diffusion approach to describing wave transport fails in translucent samples thinner than the distance between scattering events such as are encountered in meteorology, astronomy, biomedicine, and communications. Here we show in optical measurements and numerical simulations that the scaling of transmission and the intensity profiles of transmission eigenchannels have the same form in translucent as in opaque media. Paradoxically, the similarities in transport across translucent and opaque samples explain the puzzling observations of suppressed optical and ultrasonic delay times relative to predictions of diffusion theory well into the diffusive regime.
The low lying zeros of a GL(4) and a GL(6) family of $L$-functions

We investigate the large weight (, where they find evidence of orthogonal and symplectic symmetry, respectively. The present examples suggest a relation between the symmetry type of a family and that of its twistings, which will be further studied in a subsequent paper. Both the GL(4) and the GL(6) families above have all even functional equations, and neither is naturally split from an orthogonal family. A folklore conjecture states that such families must be symplectic, which is true for the first family but false for the second. Thus, the theory of low lying zeros is more than just a theory of signs of functional equations. An analysis of these families suggest that it is the second moment of the Satake parameters that determines the symmetry group.
A “Short” Distance to the Large Magellanic Cloud With the Hipparcos Calibrated Red Clump Stars

Following an approach developed by Paczynski & Stanek, we derive a distance to the Large Magellanic Cloud (LMC) by comparing red clump stars from the Hipparcos catalog with the red clump stars observed in two fields in the LMC that were selected from the ongoing photometric survey of the Magellanic Clouds to lie in low-extinction regions. The use of red clump stars allows a single step determination of the distance modulus to the LMC, μ0, LMC=18.065 ± 0.031 ± 0.09 mag (statistical plus systematic error), and the corresponding distance, RLMC=41.02 ± 0.59 ± 1.74 kpc. This measurement is in excellent agreement with the recent determination by Udalski et al., also based on the red clump stars, but is ~0.4 mag smaller than the generally accepted value of μ0, LMC=18.50 ± 0.15 mag. We discuss possible reasons for this discrepancy and how it can be resolved.
Introduction to molecular dynamics simulations

We provide an introduction to molecular dynamics simulations in the context of the Kob–Andersen model of a glass. We introduce a complete set of tools for doing and analyzing the results of simulations at fixed NVE and NVT. The modular format of the paper allows readers to select sections that meet their needs. We start with an introduction to molecular dynamics independent of the programming language, followed by introductions to an implementation using python and then the freely available open source software package lammps. We also describe analysis tools for the quick testing of the program during its development and compute the radial distribution function and the mean square displacement using both python and lammps.
Level truncation and the tachyon in open bosonic string field theory

Abstract The tachyonic instability of the open bosonic string is analyzed using the level truncation approach to string field theory. We have calculated all terms in the cubic action of the string field theory describing zero-momentum interactions of up to level 20 between scalars of level 10 or less. These results are used to study the tachyon effective potential and the nonperturbative stable vacuum. We find that the energy gap between the unstable and stable vacua converges much more quickly than the coefficients of the effective tachyon potential. By including fields up to level 10, 99.91% of the energy from the bosonic D-brane tension is cancelled in the nonperturbative stable vacuum. It appears that the perturbative expansion of the effective tachyon potential around the unstable vacuum has a small but finite radius of convergence. We find evidence for a critical point in the tachyon effective potential at a small negative value of the tachyon field corresponding to this radius of convergence. We study the branch structure of the effective potential in the vicinity of this point and speculate that the tachyon effective potential is globally non-negative.
Bootstrapping in convergence groups

We prove a true bootstrapping result for convergence groups acting on a Peano continuum. We give an example of a Kleinian group H which is the amalgamation of two closed hyperbolic surface groups along a simple closed curve. The limit setH is the closure of a "tree of circles" (adjacent circles meeting in pairs of points). We alter the action of H on its limit set such that H no longer acts as a convergence group, but the stabilizers of the circles remain unchanged, as does the action of a circle stabilizer on said circle. This is done by first separating the circles and then gluing them together backwards. AMS Classification 20F32; 57N10
Spectroscopy and Time Variability of Absorption Lines in the Direction of the Vela Supernova Remnant

We present high-resolution (R ≈ 75,000), high signal-to-noise (S/N ≈ 100) Ca II λ3933.663 and Na I λλ5889.951, 5895.924 spectra of 68 stars in the direction of the Vela supernova remnant. The spectra comprise the most complete high-resolution, high S/N optical survey of early-type stars in this region of the sky. A subset of the sight lines has been observed at multiple epochs, 1993/1994 and 1996. Of the 13 stars observed twice, seven have spectra revealing changes in the equivalent width and/or velocity structure of lines, most of which arise from remnant gas. Such time variability has been reported previously for the sight lines toward HD 72089 and HD 72997 by Danks & Sembach and for HD 72127 by Hobbs and coworkers. We have confirmed the ongoing time variability of these spectra and present new evidence of variability in the spectra of HD 73658, HD 74455, HD 75309, and HD 75821. We have tabulated Na I and Ca II absorption-line information for the sight lines in our sample to serve as a benchmark for further investigations of the dynamics and evolution of the Vela SNR.
Evaluating the dynamical stability of outer solar system objects in the presence of planet nine

We evaluate the dynamical stability of a selection of outer solar system objects in the presence of the proposed new solar system member Planet Nine. We use a Monte Carlo suite of numerical N-body integrations to construct a variety of orbital elements of the new planet and evaluate the dynamical stability of eight trans-Neptunian objects (TNOs) in the presence of Planet Nine. These simulations show that some combinations of orbital elements () result in Planet Nine acting as a stabilizing influence on the TNOs, which can otherwise be destabilized by interactions with Neptune. These simulations also suggest that some TNOs transition between several different mean-motion resonances during their lifetimes while still retaining approximate apsidal antialignment with Planet Nine. This behavior suggests that remaining in one particular orbit is not a requirement for orbital stability. As one product of our simulations, we present an a posteriori probability distribution for the semimajor axis and eccentricity of the proposed Planet Nine based on TNO stability. This result thus provides additional evidence that supports the existence of this proposed planet. We also predict that TNOs can be grouped into multiple populations of objects that interact with Planet Nine in different ways: one population may contain objects like Sedna and 2012 VP113, which do not migrate significantly in semimajor axis in the presence of Planet Nine and tend to stay in the same resonance; another population may contain objects like 2007 TG422 and 2013 RF98, which may both migrate and transition between different resonances.
WHY THE xE DISTRIBUTION TRIGGERED BY A LEADING PARTICLE DOES NOT MEASURE THE FRAGMENTATION FUNCTION BUT DOES MEASURE THE RATIO OF THE TRANSVERSE MOMENTA OF THE AWAY-SIDE JET TO THE TRIGGER-SIDE JET

Hard-scattering of point-like constituents (or partons) in p-p collisions was discovered at the CERN-ISR1 in 1972 by measurements utilizing inclusive single or pairs of hadrons with large transverse momentum (pT). Due to the steeply falling power-law pT spectrum of the hard-scattered partons, the inclusive single particle (e.g. π0) pTt spectrum from parton fragmentation to a jet is dominated by trigger fragments with large zt ~ 0.7–0.8, where zt = pTt/pTjet is the fragmentation variable. It was generally assumed, following Feynman, Field and Fox,2 as shown by data from the CERN-ISR experiments, that the pTa distribution of away side hadrons from a single particle trigger [with pTt], corrected for zt, would be the same as that from a jet-trigger and follow the same fragmentation function as observed in e+e− or DIS. PHENIX3 attempted to measure the fragmentation function from the away side xE ~ PTa/pTt distribution of charged particles triggered by a π0 in p−p collisions at RHIC and showed by explicit calculation that the xE distribution is actually quite insensitive to the fragmentation function. Illustrations of the original arguments and ISR results will be presented. Then the lack of sensitivity to the fragmentation function will be explained, and an analytic formula for the xE distribution given, in terms of incomplete Gamma functions, for the case where the fragmentation function is exponential. The away-side distribution in this formulation has the nice property that it both exhibits xE scaling and is directly sensitive to the ratio of the away jet to that of the trigger jet, , and thus can be used, for example, to measure the relative energy loss of the two jets from a hard-scattering which escape from the medium in A+A collisions. Comparisons of the analytical formula to RHIC measurements will be presented, including data from STAR4,5 and PHENIX,3,6 leading to some interesting conclusions.
On the Asymptotic Behavior of the Kernel Function in the Generalized Langevin Equation: A One-Dimensional Lattice Model

We present some estimates for the memory kernel function in the generalized Langevin equation, derived using the Mori–Zwanzig formalism from a one-dimensional lattice model, in which the particles interactions are through nearest and second nearest neighbors. The kernel function can be explicitly expressed in a matrix form. The analysis focuses on the decay properties, both spatially and temporally, revealing a power-law behavior in both cases. The dependence on the level of coarse-graining is also studied.
Nonparametric estimation of multivariate convex-transformed densities

We study estimation of multivariate densities p of the form p(x)=h(g(x)) for x∈ℝd and for a fixed monotone function h and an unknown convex function g. The canonical example is h(y)=e−y for y∈ℝ;; in this case, the resulting class of densities $$\mathcal {P}(e^{-y})=\{p=\exp(-g): g\mbox{ is convex}\} $$ is well known as the class of log-concave densities. Other functions h allow for classes of densities with heavier tails than the log-concave class. We first investigate when the maximum likelihood estimator p exists for the class $\mathcal {P}(h)$ for various choices of monotone transformations h, including decreasing and increasing functions h. The resulting models for increasing transformations h extend the classes of log-convex densities studied previously in the econometrics literature, corresponding to h(y)=exp(y). We then establish consistency of the maximum likelihood estimator for fairly general functions h, including the log-concave class $\mathcal {P}(e^{-y})$ and many others. In a final section, we provide asymptotic minimax lower bounds for the estimation of p and its vector of derivatives at a fixed point x0 under natural smoothness hypotheses on h and g. The proofs rely heavily on results from convex analysis.
Delay minimizing user association in cellular networks via hierarchically well-separated trees

We study downlink delay minimization within the context of cellular user association policies that map mobile users to base stations. We note the delay minimum user association problem fits within a broader class of network utility maximization and can be posed as a non-convex quadratic program. This non-convexity motivates a split quadratic objective function that captures the original problem's inherent tradeoff: association with a station that provides the highest signal-to-interference-plus-noise ratio (SINR) vs. a station that is least congested. We find the split-term formulation is amenable to linearization by embedding the base stations in a hierarchically well-separated tree (HST), which offers a linear approximation with constant distortion. We provide a numerical comparison of several problem formulations and find that with appropriate optimization parameter selection, the quadratic reformulation produces association policies with sum delays that are close to that of the original network utility maximization. We also comment on the more difficult problem when idle base stations (those without associated users) are deactivated.
Applying Recent Innovations from NLP to MOOC Student Course Trajectory Modeling.

This paper presents several strategies that can improve neural network-based predictive methods for MOOC student course trajectory modeling, applying multiple ideas previously applied to tackle NLP (Natural Language Processing) tasks. In particular, this paper investigates LSTM networks enhanced with two forms of regularization, along with the more recently introduced Transformer architecture.
Resolvent near zero energy on Riemannian scattering (asymptotically conic) spaces, a Lagrangian approach

We use a Lagrangian regularity perspective to discuss resolvent estimates near zero energy on Riemannian scattering, i.e. asymptotically conic, spaces, and their generalizations. In addition to the...
Recognizing algebraic surfaces from their outlines

The outline in a single picture of a generic algebraic surface of degree three or greater completely determines the projective geometry of the surface. The result holds for a generic perspective view of a generic algebraic surface, where the camera calibration parameters and the focal point are unknown. Known camera calibration appears not to reduce the projective ambiguity. The result is constructive.
Large molasses-like cooling forces for molecules using polychromatic optical fields: A theoretical description

The authors propose using polychromatic laser radiation as a mechanism for laser cooling of atoms and molecules with complex level structures.
An $\tilde{O}(n^{5/4})$ Time $\varepsilon$-Approximation Algorithm for RMS Matching in a Plane

The 2-Wasserstein distance (or RMS distance) is a useful measure of similarity between probability distributions that has exciting applications in machine learning. For discrete distributions, the problem of computing this distance can be expressed in terms of finding a minimum-cost perfect matching on a complete bipartite graph given by two multisets of points $A,B \subset \mathbb{R}^2$, with $|A|=|B|=n$, where the ground distance between any two points is the squared Euclidean distance between them. Although there is a near-linear time relative $\varepsilon$-approximation algorithm for the case where the ground distance is Euclidean (Sharathkumar and Agarwal, JACM 2020), all existing relative $\varepsilon$-approximation algorithms for the RMS distance take $\Omega(n^{3/2})$ time. This is primarily because, unlike Euclidean distance, squared Euclidean distance is not a metric. In this paper, for the RMS distance, we present a new $\varepsilon$-approximation algorithm that runs in $O(n^{5/4}\mathrm{poly}\{\log n,1/\varepsilon\})$ time. Our algorithm is inspired by a recent approach for finding a minimum-cost perfect matching in bipartite planar graphs (Asathulla et al., TALG 2020). Their algorithm depends heavily on the existence of sub-linear sized vertex separators as well as shortest path data structures that require planarity. Surprisingly, we are able to design a similar algorithm for a complete geometric graph that is far from planar and does not have any vertex separators. Central components of our algorithm include a quadtree-based distance that approximates the squared Euclidean distance and a data structure that supports both Hungarian search and augmentation in sub-linear time.
Bio-Inspired Energy Distribution for Programmable Matter

In systems of active programmable matter, individual modules require a constant supply of energy to participate in the system’s collective behavior. These systems are often powered by an external energy source accessible by at least one module and rely on module-to-module power transfer to distribute energy throughout the system. While much effort has gone into addressing challenging aspects of power management in programmable matter hardware, algorithmic theory for programmable matter has largely ignored the impact of energy usage and distribution on algorithm feasibility and efficiency. In this work, we present an algorithm for energy distribution in the amoebot model that is loosely inspired by the growth behavior of Bacillus subtilis bacterial biofilms. These bacteria use chemical signaling to communicate their metabolic states and regulate nutrient consumption throughout the biofilm, ensuring that all bacteria receive the nutrients they need. Our algorithm similarly uses communication to inhibit energy usage when there are starving modules, enabling all modules to receive sufficient energy to meet their demands. As a supporting but independent result, we extend the amoebot model’s well-established spanning forest primitive so that it self-stabilizes in the presence of crash failures. We conclude by showing how this self-stabilizing primitive can be leveraged to compose our energy distribution algorithm with existing amoebot model algorithms, effectively generalizing previous work to also consider energy constraints.
Rapid whole genome sequence typing reveals multiple waves of SARS-CoV-2 spread

Background: As the pandemic SARS-CoV-2 virus has spread globally its genome has diversified and distinct clones can now be recognized, tracked, and traced Identifying clonal groups allows for assessment of geographic spread, transmission events, and identification of more virulent or transmissible emerging strains Methods: All SARS-CoV-2 genomes (n=17,504) that are complete and high coverage were downloaded from GISAID on May 17th 2020 We developed a GNU-based Virus IDentification (GNUVID) tool that implements a whole genome multilocus sequence typing (wgMLST) scheme composed of all ten ORFs in the SARS-CoV-2 genome The 10,422 genomes that passed our quality check were fed to the GNUVID tool, which assigned a ST profile to each genome Global optimum eBURST was then used to cluster the STs in clonal complexes (CCs) Results: Our ST/CC analysis uncovered strong associations of ST/CCs with certain geographical regions but also dynamic local changes in ST/CC prevalence We also identified several unexpected putative global transmission events (e g , from the US to the Middle East and reintroduction to China later in the pandemic) We have made our tool (GNUVID) available so that new WG sequences can be rapidly assigned to an ST/CC (https://github com/ahmedmagds/GNUVID) Conclusion: Our sequence typing system uncovered previously unappreciated transmission events and waves of expansion and replacement of SARS-CoV-2 STs and CCs in different geographical locations, suggesting complex dynamics in viral populations that previously seemed monomorphic Because, our tool can be rapidly updated with new sequencing data it can track emerging clones and identifying new hotspots
The importance of marginal cost electricity pricing to the success of greenhouse gas reduction programs

The efficient reduction of GHG emissions requires appropriate retail pricing of off-peak electricity. However, off-peak electricity for residential consumers is priced at 331% above its marginal cost in the United States as a whole (June 2009). Even for the 1% of residences that are on some form of time-of-use (TOU) rate schedule, the off-peak rate is almost three times higher than the marginal cost. A barrier to marginal-cost based TOU rates is that less than 9% of U.S. households have the “smart” meters in place that can measure and record the time of consumption. Policies should be put in place to achieve full deployment. Another important barrier is consumer concern about TOU rate design. Two TOU rate designs (baseline and two-part tariff) are described that utilize marginal-cost based rates, ensure appropriate cost recovery, and minimize bill changes from current rate structures. A final barrier is to get residences on to these rates. Should a marginal-cost based TOU rate design remain an alternative for which residences could “opt-in,” or become the default choice, or become mandatory? Time-invariant rates are a historical anachronism that subsidize very costly peak-period consumption and penalize off-peak usage to our environmental detriment. They should be phased out.
On Legal Education and Reform: One View Formed from Diverse Perspectives

This Symposium is part of a broader, national dialogue on the reform of legal education. In many ways, American legal education is fine. But it is not perfect. I identify two interconnected problems. First, legal education and practice are more disconnected than they should be, a reality distinguishing law schools from other professional schools. Second, law school imposes large direct and opportunity costs on its students. Additionally, a deficiency in academic training and postgraduation financing of additional training impose a
Endogenous Money and David Hume

impressive achievement for one essay! Without wishing to diminish the possible genius that is able to generate opposite theories within a few pages while remaining consistent, this paper presents an alternative way of reading Hume's essay on money. While modern interpretations of Hume attribute to his work modern and conflicting monetary theories,3 1 attribute to Hume's work pre-modern monetary theories, making him consistent instead. A common assumption in modern monetary theory is that money is exogenous.4 The supply of money is often modeled as being determined by a central agent, such as a central bank, in a more or less arbitrary way. The equilibrium in the money market is achieved by adjustment in the quantity of money demanded and in the price level. Changes in money supply would be responsible for either changes in aggregate output, in the price level, or a combination of both, depending on the rigidity assumptions and on the time horizon considered. However, in pre-modern times, money is often thought of as endogenous,5 as the quantity of money supplied would adjust to its demand. Indeed, the quantity of money in a country is often considered a function of domestic industry, and domestic industry a function of the domestic and foreign demand for domestic goods. Changes in the economy would therefore be due to changes in demand rather than in money supply. I claim that this discrepancy in assumptions is what makes the difference in reading Hume. Reading Hume's essays in this premodern framework, which reflects Hume's own knowledge and education, presents a strong and consistent picture of a demand-driven and endogenous money.6 It is when Hume's background and knowledge of money are ignored that his positions lose clarity, leaving him neither consistent nor original. If my interpretation is sound, it may bring some new (or old?) insights on monetary policy and monetary theory. In my reading, Hume thinks that money demand is dependent on consumer tastes, which depend on commerce. The endogenation process is achieved through commerce, international trade, as well as hoarding, rather than through the banking system, of which Hume was very critical.7 He presents a view of money that not only differs from contemporary exogenous money theories, but also, partially, from modern endogenous theories. Today's emphasis on monetary policies may be tempered, if, as Hume claims, consumers would absorb changes in
Constrained Optimization Approaches to Estimation of Structural Models

Maximum likelihood estimation of structural models is regarded as computationally di-cult. This impression is due to a focus on the Nested Fixed-Point approach. We present a direct optimization approach to the problem and show that it is signiflcantly faster than the NFXP approach when applied to the canonical Zurcher bus repair model. The NFXP approach is inappropriate for estimating games since it requires flnding all Nash equilibria of a game for each parameter vector considered, a generally intractable computational problem. We reformulate the problem of maximum likelihood estimation of games so into an optimization problem that is qualitatively no more di-cult to solve than standard problems. The direct optimization approach is also applicable to other structural estimation problems such as auctions and RBC models, and also to other estimation strategies, such as the methods of moments. It is also easily implemented on standard software.
Internationalist Oilmen, the Middle East, and the Remaking of American Liberalism, 1945–1953

The ways in which business–government relations influenced postwar liberalism in the American encounter with the Middle East are examined through the use of group biography. The linked careers of five internationalist oilmen who helped to formulate Harry S. Truman's domestic and foreign policies are tracked during and after World War II. Partly through the efforts of these influential men, the Middle East's vast oil resources became an important component of controversies about the direction of the New Deal. One conclusion to emerge from the study is that instead of simply studying liberal ideals in order to understand the American impulse to reform the world, historians also need to consider how global factors intruded into domestic reform debates.
Why firms’ exploitation of consumer myopia may benefit myopic consumers

Myopic consumers underestimate the likelihood with which they will require follow-on services for products they purchase. Firms have an incentive to exploit this behavioral bias by skewing their price structure toward high add-on charges. Inadvertently, this skewed price structure provides myopic consumers with a monetary incentive mechanism that tends to inhibit, rather than propel, inefficient consumption decisions.
Why Sex (Offending) Is Different

The central premise is that a significant amount of sex offending stems from unusual or inappropriate sexual preferences that appear in early adolescence, are relatively stable, and immutable. In those ways, they are like more ordinary sexual preferences, generating sexual impulses that are insistent. Individuals are strongly tempted to act on them, alternatives to satisfying them are unfulfilling, and complete long-term control of such impulses is unlikely. Yet, since individuals with sexual preferences for inappropriate objects or activities are neither morally nor legally permitted to act on them, they find themselves in a terrific bind. The public is, to some extent, correct to not trust the individuals with such preferences and to attempt to monitor or control them. However, most such efforts appear ineffective and counterproductive. Recidivist sex offenders are particularly worrisome. The possibility of voluntary castration for such offenders, in lieu of preventive detention or other more restrictiv...
Characteristics of Exemplary Programs in Preparing Graduate Assistants to Teach Economics

Recent research by Walstad and Becker (2010) and McCoy and Milkman (2010) indicate that the vast majority of economics graduate programs perform an inadequate job of training their Ph.D. students t...
Discussion of “Accounting standards and debt covenants: Has the “Balance Sheet Approach” led to a decline in the use of balance sheet covenants?”

Abstract Demerjian (this issue) argues that a shift by U.S. standard setters towards the balance sheet approach reduces the usefulness of balance sheet numbers for contracting. Consistent with this argument, he provides evidence of a decline in the use of balance sheet-based covenants in debt contracts, a useful finding. Nevertheless, I argue that the evolution of standard-setting is more complex than this argument implies, and evaluate the economic basis of Demerjian's arguments for how debt contracts respond to changes in accounting rules. One conclusion that emerges is that there are still some important open issues regarding the economic determinants of debt contracts.
Emergency Response: A Systemic Approach to Diaper Rash, Chest Pain, and Medicaid in the ED

I an effort to rein in health care costs, states have focused on non–emergent use of the Emergency Department (ED)2 by people with Medicaid coverage. This focus has some merit. Although non–emergent ED use is by no means just a Medicaid issue,3 it imposes added costs and undermines care continuity. It is better for all patients to receive routine medical care in a primary care setting. And as more people gain insurance coverage by virtue of Affordable Care Act (ACA)4 provisions, it will be particularly important to provide the right care in the right location. Any attempt to address non–emergent ED use should be guided by two principles. First, as is reinforced by federal and state law, people should not be dissuaded from seeking needed emergency care. Second, as a matter of system sustainability, solutions should target the root causes of the problem. These principles support a system–based approach that views ED overutilization as less a reflection of poor judgment on the part of patients and more a consequence of poor access to primary care and poor systems for managing the complex non–medical problems of high utilizers.5 A systemic
Hydrodynamics in lattice models with continuous non-Abelian symmetries

We develop a systematic effective field theory of hydrodynamics for many-body systems on the lattice with global continuous non-Abelian symmetries. Models with continuous non-Abelian symmetries are ubiquitous in physics, arising in diverse settings ranging from hot nuclear matter to cold atomic gases and quantum spin chains. In every dimension and for every flavor symmetry group, the low energy theory is a set of coupled noisy diffusion equations. Independence of the physics on the choice of canonical or microcanonical ensemble is manifest in our hydrodynamic expansion, even though the ensemble choice causes an apparent shift in quasinormal mode spectra. We use our formalism to explain why flavor symmetry is qualitatively different from hydrodynamics with other non-Abelian conservation laws, including angular momentum and charge multipoles. As a significant application of our framework, we study spin and energy diffusion in classical one-dimensional SU(2)-invariant spin chains, including the Heisenberg model along with multiple generalizations. We argue based on both numerical simulations and our effective field theory framework that non-integrable spin chains on a lattice exhibit conventional spin diffusion, in contrast to some recent predictions that diffusion constants grow logarithmically at late times. We show that the apparent enhancement of diffusion is due to slow equilibration caused by (non-Abelian) hydrodynamic fluctuations.
An Equilibrium Model of Investment Under Uncertainty

This paper analyzes the optimal investment decisions of heterogeneous Þrms in a competitive, uncertain environment. We characterize Þrms’ optimal investment strategy explicitly, and derive a closed form solution for Þrm value. We show that in the strategic equilibrium real option premia are signiÞcant. As a result Þrms delay investment, choosing optimally not to undertake some positive NPV projects. The model predicts that Þrm returns vary over the business cycle, with returns negatively skewed during expansions but positively skewed in recessions.
Sustaining a global recovery

Recovery from the global economic crisis has begun, but the crisis has most likely caused a drop in potential output. The higher-than-normal growth that follows most recessions should not be expected this time. Sustaining the recovery will require two delicate rebalancing acts. First, countries will have to rebalance from public to private spending. Second, aggregate demand will have to be rebalanced across counties, with a shift from domestic to foreign demand in the United States and a reverse shift from foreign to domestic demand in the rest of the world, especially Asia.
Geography and Economic Development

Location and climate have large effects on income levels and income growth through their effects on transport costs, disease burdens, and agricultural productivity, among other channels. Geography also seems to affect economic policy choices. Many geographic regions that have not been conducive to modern economic growth have high population densities and are experiencing rapid increases in population. At particular disadvantage are regions located far from coasts and ocean-navigable rivers, for which the transport costs of international trade are high, and tropical regions, which bear a heavy burden of disease. Moreover, a large portion of population growth over the next thirty years is expected to occur in these geographically disadvantaged regions.
Minimum Distance Estimation of Nonstationary Time Series Models

This paper analyzes the limit distribution of minimum distance (MD) estimators for nonstationary time series models that involve nonlinear parameter restrictions. A rotation for the restricted parameter space is constructed to separate the components of the MD estimator that converge at different rates. We derive regularity conditions for the restriction function that are easier to verify than the stochastic equicontinuity conditions that arise from direct estimation of the restricted parameters. The sequence of matrices that is used to weigh the discrepancy between the unrestricted estimates and the restriction function is allowed to have a stochastic limit. For MD estimators based on unrestricted estimators with a mixed normal asymptotic distribution the optimal weight matrix is derived and a goodness-of-fit test is proposed. Our estimation theory is illustrated in the context of a permanent-income model and a present-value model.
The diagnosis is anencephaly and the parents ask about organ donation: now what? A guide for hospital counsel and ethics committees.

PROLOGUE: CASE STUDy-THE MSI After a period of infertility treatments, Mr. and Mrs. M learned that they were going to have triplets. Mrs. M, shortly there­ after, developed a fear that something was wrong with one of the babies whom she had named Avery. An ultrasound, at seventeen weeks, confirmed Mrs. M's fear. Avery was missing her upper skull. She had anencephaly.2 After telling the Ms the result of the ultrasound, the maternal-fetal medicine doctor informed the Ms
International Contagion through Leveraged Financial Institutions

Abstract The 2008 –2009 financial crises, while originating in the United States, witnessed a drop in asset prices and output that was at least as large in the rest of the world. We investigate, in the context of a simple two-country model, whether this could have been the result of transmission through leveraged financial institutions. The paper highlights what the various transmission mechanisms associated with balance sheet losses are. For realistic parameters we find that the model cannot account for the global nature of the crisis, both in terms of the size of the impact and the extent of transmission. (JEL E32, E44, F44, G01, G21)
Research fraud as tort.

In their Policy Forum “Self-correction in science at work” (26 June, p. [1420][1]), B. Alberts et al. propose that “incentives should be changed so that scholars are rewarded for publishing well rather than often.” They recommend, for example, replacing the word “retraction” with alternate phrasing, such as “voluntary withdrawal” and “withdrawal for cause,” depending on the absence or presence of fraud or other research misconduct. In addition to reforming the reward structure of scientific publishing—a worthy goal—we would also draw attention to the possibility of legal liability for research fraud. Beyond the possibility of a mere retraction (or as Alberts et al. propose, a “withdrawal for cause”), scientific researchers should be held to the same legal standards as any individual or business. By way of example, we propose extending the well-established tort of fraudulent misrepresentation to fraudulent research published in journals based in the United States. Proving fraudulent misrepresentation is not easy. In the context of research fraud, the duped journal would have to prove that the fraudulent researcher intended to deceive the journal, that his or her misrepresentations were material—i.e., essential for being accepted for publication—and that the journal was justified in relying on the researcher's misrepresentations in making the decision to publish ([ 1 ][2]). By making scientific researchers who publish in U.S. journals liable in tort for their acts of fraud, we would expect to deter the incidence of fraud before it occurs. If we wish to promote integrity in science, let's not forget to use sticks as well as carrots. 1. [↵][3]Legal Information Institute, Fraudulent Misrepresentation ([www.law.cornell.edu/wex/fraudulent_misrepresentation][4]). [1]: /lookup/doi/10.1126/science.aab3847 [2]: #ref-1 [3]: #xref-ref-1-1 "View reference 1 in text" [4]: http://www.law.cornell.edu/wex/fraudulent_misrepresentation
Economic tracking portfolios

An economic tracking portfolio is a portfolio of assets with returns that track an economic variable. Monthly returns on stocks and bonds help forecast post-war US output, consumption, labor income, inflation, stock returns, bond returns, and Treasury bill returns. These forecasting relationships define portfolios that track market expectations about future economic variables. Out-of-sample results show that tracking portfolios, despite forecast deterioration, can be useful in forecasting macroeconomic variables.
Full-frequency GW without frequency

Efficient computer implementations of the GW approximation must approximate a numerically challenging frequency integral; the integral can be performed analytically, but doing so leads to an expensive implementation whose computational cost scales as O(N6), where N is the size of the system. Here, we introduce a new formulation of the full-frequency GW approximation by exactly recasting it as an eigenvalue problem in an expanded space. This new formulation (1) avoids the use of time or frequency grids, (2) naturally obviates the need for the common “diagonal” approximation, (3) enables common iterative eigensolvers that reduce the canonical scaling to O(N5), and (4) enables a density-fitted implementation that reduces the scaling to O(N4). We numerically verify these scaling behaviors and test a variety of approximations that are motivated by this new formulation. The new formulation is found to be competitive with conventional O(N4) methods based on analytic continuation or contour deformation. In this new formulation, the relation of the GW approximation to configuration interaction, coupled-cluster theory, and the algebraic diagrammatic construction is made especially apparent, providing a new direction for improvements to the GW approximation.
Complex Tax Legislation in the TurboTax Era

When tax returns were prepared with pencil and paper—in an era now gone forever—Congress did not impose income tax provisions of great computational complexity on large numbers of taxpayers, in the belief that it was unreasonable to require average taxpayers (or their paid preparers) to struggle with computationally complex provisions. As return preparation software gradually replaced the pencil in recent decades, the complexity constraint weakened and eventually disappeared. Congress has responded by imposing unprecedented computational complexity on large numbers of taxpayers—primarily through the expanded scope of the alternative minimum tax and the proliferation of phase outs of credits, deductions, and exclusions. This response would not be problematic, if the only objection to computational complexity were the difficulty of performing the calculations—a difficulty overcome by the widespread adoption of software. Unfortunately, computationally complex provisions generally constitute bad tax policy, even apart from computational concerns. For taxpayers faced with a welter of computationally complex provisions, the income tax is a black box, the inner workings of which are beyond their comprehension. This undermines both the political legitimacy of the tax system and the ability of taxpayers to engage in informed tax planning. In response to the demise of the complexity constraint, argues this Essay, Congress should develop a self-imposed constraint against the enactment (or survival) of computationally complex provisions of widespread applicability.
Measuring systematic monetary policy

The 1970s and early 1980s witnessed two main approaches to the analysis of monetary policy. The first is the early new classical approach of Lucas, based on the assumptions of rational expectations and market clearing. The second is the a theoretical econometrics of Sims’s VAR program. Both have developed: the new classical approach has been enriched through various accounts of price stickiness, cost of adjustment or alternative expectational schemes; the original VAR program has developed into the structural VAR program. This paper clarifies the relationship between these two programs. Based on work of Cochrane (1998), it shows that the typical method of evaluating unanticipated, unsystematic monetary policy is correct only if the conditions necessary for Lucas’s policy-ineffectiveness proposition hold, while recent methods for evaluating systematic monetary policy violate Lucas’s policy-noninvariance proposition (“the Lucas critique”). The paper shows how to construct and estimate (using regime changes) a model in which some agents form rational-expectations and others follow rules of thumb. In such a model, monetary policy actions can be validly decomposed into systematic and unsystematic components and valid counterfactual experiments on alternative systematic monetary-policy rules can be evaluated. (This abstract was borrowed from another version of this item.)
Sell-Side Information Production in Financial Markets

We study decisions to sell nonexcludable private information in the presence of a trading opportunity. Sell-side agents heighten competition among agents who buy their signals to combine with their own for proprietary trading purposes and thereby promote financial market efficiency. This result holds even when the sell-side production technology is not unique. But sell-side information is subject to underinvestment if producers do not internalize the benefits. The model suggests that fee-based compensation for corporate advisory services diminishes this problem and that market efficiency is undermined by forces steering investment-banking resources toward proprietary trading.