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"Universality"
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The Galerkin-truncated Burgers equation
The one-dimensional Galerkin-truncated Burgers equation, with both dissipation and noise terms included, is studied using spectral methods. When the truncation-scale Reynolds number R
min is varied, from very small values to order 1 values, the scale-dependent correlation time τ (k) is shown to follow the expected crossover from the short-distance τ (k) ∼ k
−2 Edwards–Wilkinson scaling to the universal long-distance Kardar–Parisi–Zhang scaling τ (k) ∼ k
−3/2. In the inviscid limit, R
min → ∞, we show that the system displays another crossover to the Galerkin-truncated inviscid-Burgers regime that admits thermalized solutions with τ (k) ∼ k
−1. The scaling forms of the time-correlation functions are shown to follow the known analytical laws and the skewness and excess kurtosis of the interface increments distributions are characterized.
This article is part of the theme issue ‘Scaling the turbulence edifice (part 2)’.
Journal Article
Universality Reconsidered: Diversity in Making Meaning of Facial Expressions
It has long been claimed that certain facial movements are universally perceived as emotional expressions. The critical tests of this universality thesis were conducted between 1969 and 1975 in small-scale societies in the Pacific using confirmation-based research methods. New studies conducted since 2008 have examined a wider sample of small-scale societies, including on the African and South American continents. They used more discovery-based research methods, providing an important opportunity for reevaluating the universality thesis. These new studies reveal diversity, rather than uniformity, in how perceivers make sense of facial movements, calling the universality thesis into doubt. Instead, they support a perceiver-constructed account of emotion perception that is consistent with the broader literature on perception.
Journal Article
Islam in retrospect : recovering the message
Renewing our understanding of Islam in today's world. Islam, in many of its current guises, no longer resembles its original Message. In a world of intractable conflicts plagued by political Islam and Islamophobiaand where other forms of fundamentalism within the major religious creeds are on the rise, as wellthis book serves as a reminder. It aims to recover and reaffirm Islams underlying and guiding principles. Setting out to distinguish the divine from the human in order to elucidate the pristine nature of the divine Message, Mahmassani reasserts Islams universal, secular, and progressive character.
Book
TRACY-WIDOM DISTRIBUTION FOR THE LARGEST EIGENVALUE OF REAL SAMPLE COVARIANCE MATRICES WITH GENERAL POPULATION
We consider sample covariance matrices of the form Q = (∑½X)(∑½X)*, where the sample X is an M × N random matrix whose entries are real independent random variables with variance 1/N and where ∑ is an M × M positive-definite deterministic matrix. We analyze the asymptotic fluctuations of the largest rescaled eigenvalue of Q when both M and N tend to infinity with N/M → d ϵ (0, ∞). For a large class of populations ∑ in the sub-critical regime, we show that the distribution of the largest rescaled eigenvalue of Q is given by the type-1 Tracy-Widom distribution under the additional assumptions that (1) either the entries of X are i.i.d. Gaussians or (2) that ∑ is diagonal and that the entries of X have a sub-exponential decay.
Journal Article
Matrix concentration inequalities and free probability
A central tool in the study of nonhomogeneous random matrices, the noncommutative Khintchine inequality, yields a nonasymptotic bound on the spectral norm of general Gaussian random matrices X=∑igiAi where gi are independent standard Gaussian variables and Ai are matrix coefficients. This bound exhibits a logarithmic dependence on dimension that is sharp when the matrices Ai commute, but often proves to be suboptimal in the presence of noncommutativity. In this paper, we develop nonasymptotic bounds on the spectrum of arbitrary Gaussian random matrices that can capture noncommutativity. These bounds quantify the degree to which the spectrum of X is captured by that of a noncommutative model Xfree that arises from free probability theory. This “intrinsic freeness” phenomenon provides a powerful tool for the study of various questions that are outside the reach of classical methods of random matrix theory. Our nonasymptotic bounds are easily applicable in concrete situations, and yield sharp results in examples where the noncommutative Khintchine inequality is suboptimal. When combined with a linearization argument, our bounds imply strong asymptotic freeness for a remarkably general class of Gaussian random matrix models that may be very sparse, have dependent entries, and lack any special symmetries. When combined with a universality principle, our bounds extend beyond the Gaussian setting to general sums of independent random matrices.
Journal Article
Are we there yet? Academies, scientific organisations, and gender
Is the representation of women in academies and scientific organisations improving, globally? A major new study shows that among the academies, representation of women in membership has risen from 13% (for academies surveyed in 2015) to 16% (for all academies surveyed in 2020).1 The progress is good: the level of representation is shocking. In the words of Daya Reddy, past President of the International Science Council, ‘… Societies expect more diverse gender representation in science.’ This report, however, is a goldmine of information on gender in leading scientific organisations. The study explores the dimensions of differences across disciplines and regional variation, and provides 10 clear recommendations.
Journal Article
What Scientists Who Study Emotion Agree About
In recent years, the field of emotion has grown enormously—recently, nearly 250 scientists were identified who are studying emotion. In this article, I report a survey of the field, which revealed high agreement about the evidence regarding the nature of emotion, supporting some of both Darwin's and Wundt's 19th century proposals. Topics where disagreements remain were also exposed.
Journal Article
Situational factors shape moral judgements in the trolley dilemma in Eastern, Southern and Western countries in a culturally diverse sample
The study of moral judgements often centres on moral dilemmas in which options consistent with deontological perspectives (that is, emphasizing rules, individual rights and duties) are in conflict with options consistent with utilitarian judgements (that is, following the greater good based on consequences). Greene et al. (2009) showed that psychological and situational factors (for example, the intent of the agent or the presence of physical contact between the agent and the victim) can play an important role in moral dilemma judgements (for example, the trolley problem). Our knowledge is limited concerning both the universality of these effects outside the United States and the impact of culture on the situational and psychological factors affecting moral judgements. Thus, we empirically tested the universality of the effects of intent and personal force on moral dilemma judgements by replicating the experiments of Greene et al. in 45 countries from all inhabited continents. We found that personal force and its interaction with intention exert influence on moral judgements in the US and Western cultural clusters, replicating and expanding the original findings. Moreover, the personal force effect was present in all cultural clusters, suggesting it is culturally universal. The evidence for the cultural universality of the interaction effect was inconclusive in the Eastern and Southern cultural clusters (depending on exclusion criteria). We found no strong association between collectivism/individualism and moral dilemma judgements.Including participants from 45 countries, Bago et al. find that the situational factors that affect moral reasoning are shared across countries, with diminished observed cultural variation.
Journal Article