Optimal sampling strategies for multiscale stochastic processes

In this paper, we determine which non-random sampling of fixed size gives the best linear predictor of the sum of a finite spatial population. We employ different multiscale superpopulation models and use the minimum mean-squared error as our optimality criterion. In multiscale superpopulation tree models, the leaves represent the units of the population, interior nodes represent partial sums of the population, and the root node represents the total sum of the population. We prove that the optimal sampling pattern varies dramatically with the correlation structure of the tree nodes. While uniform sampling is optimal for trees with ``positive correlation progression'', it provides the worst possible sampling with ``negative correlation progression.'' As an analysis tool, we introduce and study a class of independent innovations trees that are of interest in their own right. We derive a fast water-filling algorithm to determine the optimal sampling of the leaves to estimate the root of an independent innovations tree.Comment: Published at http://dx.doi.org/10.1214/074921706000000509 in the IMS Lecture Notes--Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

The Relative Power of Employment-to-Employment Reallocation and Unemployment Exits in Predicting Wage Growth

We study the cyclical comovement nominal wage growth (either monthly earnings or hourly wage rate) and labor market flows. We use microdata from the Survey of Income and Program Participation over 1996-2013 to purge composition effects in worker and job characteristics and to isolate the reallocative effect of Employer-to-Employer (EE) transitions. We find an "EE wage Phillips curve": wage inflation comoves positively with EE as strongly as with the employment rate. This correlation holds for job stayers; we interpret the EE rate as a measure of labor demand. We find no analogous evidence for the job-finding rate from unemployment

Wage Posting and Business Cycles

The canonical framework of Burdett and Mortensen (1998) derives wage dispersion as the unique equilibrium outcome in a stationary environment with meeting frictions and random search. Firms derive monopsony power from search frictions and commit to wage offers. Workers earn rents: wages are not compressed to the opportunity cost of work, owing to the ability of employed workers to receive additional offers and quit directly from one job into another, without experiencing unemployment. In previous work (Moscarini and Postel-Vinay 2016), we explored the implications of this job ladder for the aggregate dynamics of unemployment, wages, and the firm size distribution at business cycle frequencies. The model establishes a natural connection between the average wage growth in the economy and the pace of Employer-to-Employer (EE) transitions, through two channels. First, a composition effect: workers typically quit a job when they receive a better offer, hence the faster these transitions the higher the pace of reallocation toward high wages, and the higher average wage growth. Second, a strategic effect: the more opportunities workers have to quit, the more aggressive are their employers with their wage responses, to try and retain them. The first effect benefits only job movers, the second both movers and stayers. Therefore, we expect wage growth to be positively related to the pace of EE reallocation for all workers, but especially for movers. We verify this empirically with longitudinal micro data from the Survey of Income and Program Participation (SIPP)

Decoherence without dissipation?

In a recent article, Ford, Lewis and O'Connell (PRA 64, 032101 (2001)) discuss a thought experiment in which a Brownian particle is subjected to a double-slit measurement. Analyzing the decay of the emerging interference pattern, they derive a decoherence rate that is much faster than previous results and even persists in the limit of vanishing dissipation. This result is based on the definition of a certain attenuation factor, which they analyze for short times. In this note, we point out that this attenuation factor captures the physics of decoherence only for times larger than a certain time t_mix, which is the time it takes until the two emerging wave packets begin to overlap. Therefore, the strategy of Ford et al of extracting the decoherence time from the regime t < t_mix is in our opinion not meaningful. If one analyzes the attenuation factor for t > t_mix, one recovers familiar behaviour for the decoherence time; in particular, no decoherence is seen in the absence of dissipation. The latter conclusion is confirmed with a simple calculation of the off-diagonal elements of the reduced density matrix.Comment: 8 pages, 4 figure

Induction of Off-Season Flowering in Custard Apple (Annona squamosa L.) Cv. Balanagar

Pruning and defoliation are essential operations for inducing off-season flowering and fruiting to yield better quality and quantity of fruits in custard apple. Trees were subjected to two levels of pruning (25% and 50%) combined with use of chemical defoliants (urea 5%, Ethrel 2000ppm, potassium iodide 1%, or ortho-phosphoric acid 1%) besides the Control, with each treatment replicated thrice. Early initiation of flowering and better vegetative growth was seen in pruned (25%) and defoliated trees than in the Control or other treatments. Maximum off-season yield (10.33kg/ plant) was obtained in T4&nbsp;(25% pruning, combined with 5% urea spray as defoliant) and T6&nbsp;(25% pruning, combined with 1% potassium iodide-spray as defoliant). Findings of this investigation helped standardize pruning and defoliation practices on a scientific basis for off-season production of custard apple fruits

Viscoelastic Properties of Dynamically Asymmetric Binary Fluids Under Shear Flow

We study theoretically the viscoelastic properties of sheared binary fluids that have strong dynamical asymmetry between the two components. The dynamical asymmetry arises due to asymmetry between the viscoelastic stresses, particularly the bulk stress. Our calculations are based on the two-fluid model that incorporates the asymmetric stress distribution. We simulate the phase separation process under an externally imposed shear and compare the asymmetric case with the usual phase separation under a shear flow without viscoelastic effects. We also simulate the behavior of phase separated stable morphologies under applied shear and compute the stress relaxation.Comment: 10 pages text, 9 figure