Fertility trends by social status

This article discusses how fertility relates to social status with the use of a new dataset, several times larger than the ones used so far. The status-fertility relation is investigated over several centuries, across world regions and by the type of status-measure. The study reveals that as fertility declines, there is a general shift from a positive to a negative or neutral status-fertility relation. Those with high income/wealth or high occupation/social class switch from having relatively many to fewer or the same number of children as others. Education, however, depresses fertility for as long as this relation is observed (from early in the 20th century).education, fertility, income, occupation, social class, status, wealth

Population Ageing Negatively Affects Productivity

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Kan subdivision and products of simplicial sets

The canonical map from the Kan subdivision of a product of finite simplicial sets to the product of the Kan subdivisions is a simple map, in the sense that its geometric realization has contractible point inverses

Deep reinforcement learning for robust quantum optimization

Machine learning techniques based on artificial neural networks have been successfully applied to solve many problems in science. One of the most interesting domains of machine learning, reinforcement learning, has natural applicability for optimization problems in physics. In this work we use deep reinforcement learning and Chopped Random Basis optimization, to solve an optimization problem based on the insertion of an off-center barrier in a quantum Szilard engine. We show that using designed protocols for the time dependence of the barrier strength, we can achieve an equal splitting of the wave function (1/2 probability to find the particle on either side of the barrier) even for an asymmetric Szilard engine in such a way that no information is lost when measuring which side the particle is found. This implies that the asymmetric non-adiabatic Szilard engine can operate with the same efficiency as the traditional Szilard engine, with adiabatic insertion of a central barrier. We compare the two optimization methods, and demonstrate the advantage of reinforcement learning when it comes to constructing robust and noise-resistant protocols.Comment: 9 pages, 8 figure

Employee referral, social proximity and worker discipline

We study ex-post hiring risks in low income countries with limited legal and regulatory frameworks. In our theory of employee referral, the new recruit internalises the rewards and punishments of the in-house referee meted out by the hiring firm. This social mechanism makes it cheaper for the firm to induce worker discipline. The degree of internalization depends on the unobserved strength of the endogenous social tie between the referee and the recruit. When the referee's utility is increasing in the strength of ties, referee workplace incentives do not matter and referee and employer incentives are aligned: in this case industries and jobs with high costs of opportunism and where dense kinship networks can match the skill requirements of employers will have clusters of close family and friends, they will show a high incidence of referrals rather than anonymous hiring and will show a wage premium to referred workers matched by their higher productivity. This no longer applies if the referee's utility is decreasing in the strength of ties: referrals are then more costly for firms, they will be used less frequently by employers and will require higher referee wages (or status). We illustrate how these insights add to our understanding of South-Asian labour markets

Dynamic wettability alteration in immiscible two-phase flow in porous media: Effect on transport properties and critical slowing down

The change in contact angles due to the injection of low salinity water or any other wettability altering agent in an oil-rich porous medium is modeled by a network model of disordered pores transporting two immiscible fluids. We introduce a dynamic wettability altering mechanism, where the time dependent wetting property of each pore is determined by the cumulative flow of water through it. Simulations are performed to reach steady-state for different possible alterations in the wetting angle ($\theta$). We find that deviation from oil-wet conditions re-mobilizes the stuck clusters and increases the oil fractional flow. However, the rate of increase in the fractional flow depends strongly on $\theta$ and as $\theta\to 90^\circ$, a critical angle, the system shows critical slowing down which is characterized by two dynamic critical exponents.Comment: 8 pages, 9 figure

Network mechanisms and social ties in markets for low- and unskilled jobs: (theory and) evidence from North-India

Abstract: Workplace referrals may resolve incentive problems that arise due to incomplete contracts. We use an in-depth primary data set covering low- and unskilled migrants from Western Uttar Pradesh (India), to examine this and alternative explanations for referral-based recruitment. We find little evidence of referral screening for unobservable worker traits, but some support for a hypothesis of referral as a mechanism to enforce workforce discipline. Two observations back this conjecture: the high prevalence of strong kinship ties between referees and new recruits and that those who recruit are in more ‘prestigious’ jobs and therefore have higher stakes vis-à-vis their employer. These main findings are exposed to robustness checks to rule out rival explanations: that entry through a workplace insider merely reflects privileged access to job vacancy information; that workplace clustering results from preferences for working together or that the higher prevalence of referral for very young migrants that we observe may reflect that referral has an insurance dimension.Work Migration; Social Networks; Screening; Moral Hazard

Describing synchronization and topological excitations in arrays of magnetic spin torque oscillators through the Kuramoto model

The collective dynamics in populations of magnetic spin torque oscillators (STO) is an intensely studied topic in modern magnetism. Here, we show that arrays of STO coupled via dipolar fields can be modeled using a variant of the Kuramoto model, a well-known mathematical model in non-linear dynamics. By investigating the collective dynamics in arrays of STO we find that the synchronization in such systems is a finite size effect and show that the critical coupling-for a complete synchronized state-scales with the number of oscillators. Using realistic values of the dipolar coupling strength between STO we show that this imposes an upper limit for the maximum number of oscillators that can be synchronized. Further, we show that the lack of long range order is associated with the formation of topological defects in the phase field similar to the two-dimensional XY model of ferromagnetism. Our results shed new light on the synchronization of STO, where controlling the mutual synchronization of several oscillators is considered crucial for applications.Comment: Accepted for publication in Scientific Reports. Corrected typo in Eq.(9) from previous versio