We develop the geometric theory of equivariant quasisymmetry via a new “quasisymmetric flag variety.” This is a toric complex in the flag variety whose fixed point set is the set of (algebraic) noncrossing partitions, and whose cohomology ring is the ring of quasisymmetric coinvariants.

This study examined the influence of personality and negative life events during adolescence on depression in young adulthood, and the extent to which common genetic and environmental influences contributed to these associations. The data come from a Norwegian population based twin sample (N = 3,394). Depression was predicted by higher neuroticism and loneliness, as well as lower sense of coherence, self-efficacy, and resilience. Additionally, weak positive associations were found between negative life events and depression. Common genetic influences accounted for most of the phenotypic associations between depression and both personality and negative life events. The findings emphasize the importance of assessing personality characteristics early in adolescence, as they may serve as vulnerabilities for the development of depression later in life.

Private currencies can facilitate intertemporal exchange under limited commitment but exhibit excessive volatility when backed by productive assets subject to news shocks. I develop a model where banks issue deposits backed by firms’ output as collateral, with deposits circulating as currency. Adverse news about firm productivity—even when socially uninformative—induces binding debt constraints and deposit volatility, creating liquidity shortages that depress economic activity. With household heterogeneity, deposits are priced at a premium in liquidity-constrained economies. Interest-bearing central bank money provides an additional policy tool beyond traditional money growth. The interest rate influences asset prices through an investment channel: banks hold interest-bearing reserves as insurance against productivity shocks. This enables welfare-improving policies requiring positive inflation and nominal interest rates—departing from the Friedman rule. Calibrating the model to the US economy, I find that interest-bearing money generates a welfare gain of 2.54%, with the welfare cost of departing from the Friedman rule being roughly an order of magnitude smaller than the cost of operating with a suboptimal transfer. As an extension, I examine private information about consumer preferences, showing that illiquid bonds become essential for achieving efficiency. Cash-in-advance constraints on deposits can improve welfare by preventing destabilizing arbitrage, enabling coexistence of government and private currencies.

Our commentary aims to enrich Singh’s subjective selection framework in two fundamental ways. First, language is necessary for coordinating on shared instrumental goals. Without it, the explanatory burden rests largely on evolved psychology. Second, goals themselves are culturally constructed, socially transmitted, and cumulatively evolving over time. This co-evolutionary dynamic between problems and solutions exceeds what fixed psychological hierarchies can explain.

It is known that for a uniform morphic sequence $\boldsymbol u = \langle u_n\rangle _{n=0}^\infty $ and an algebraic number $\beta $ such that $|\beta |>1$, the number $[\![ \boldsymbol {u} ]\!] _\beta :=\sum _{n=0}^\infty ({u_n}/{\beta ^n})$ either lies in $\mathbb Q(\beta )$ or is transcendental. In this paper, we show a similar rational–transcendental dichotomy for sequences defined by irreducible Pisot morphisms on binary alphabets. Subject to the Pisot conjecture (an irreducible Pisot morphism has pure discrete spectrum), we generalise the latter result to arbitrary finite alphabets. In certain cases, we are able to show transcendence of $[\![ \boldsymbol {u}]\!] _{\beta }$ outright. In particular, for $k\geq 2$, if $\boldsymbol u$ is the k-Bonacci word, then $[\![ \boldsymbol {u}]\!] _{\beta }$ is transcendental.

Reviving Gould and Lewontin’s critique of adaptationism, Singh’s subjective selection favors truth over useful simplification. Nonetheless, while psychologically plausible, its explanatory power remains limited. Moreover, by treating evolved psychology as fixed, it neglects gene-culture coevolution. The result is a vision of cultural evolution whose expansiveness risks outpacing its scientific utility.

Singh’s framework of subjective selection compellingly links individual cognition to cultural convergence. My commentary emphasizes that subjective selection is hierarchically mediated: not all individuals have equal capacity to shape or transmit their evaluations. Hierarchies of influence, authority, and interdependence determine whose perceptions are amplified into cultural traditions. Accounting for inequality and social power clarifies how the cultural manifold reflects both shared psychology and the unequal distribution of influence within human societies.

This commentary welcomes Singh’s shift from dual inheritance to individual psychology but argues that his model remains incomplete without evolutionary foundations. Cultural variants are not adopted merely because they appear useful – they appeal to evolved motivational systems shaped by natural selection. Integrating adaptive goals, producer–consumer dynamics, and ecological variation transforms subjective selection into a genuinely evolutionary-ecological framework.

Singh compellingly describes some psychological factors that shape selection of cultural variants, but his approach gives insufficient attention to how culture shapes psychology. We argue the subjective selection account needs to pay greater attention to the psychological nuances of goal pursuit, cultural shaping of both perceived and “actual” effectiveness, and importance of social consensus cues.

Citizens do not directly observe democratic backsliding and, as a result, may hesitate to respond to subversion. We develop a model of third-party oversight bodies, such as the media or courts, that detect and assess actions that may be subversive to democracy and inform citizens. Oversight deters subversion, disciplines incumbents, and enables corrective actions by providing credible information about ambiguous incumbent behavior to citizens. However, when the oversight body is contested, citizens may doubt the intent behind its criticisms. When the oversight body is cautious in its criticisms, it elicits negative inferences about its intentions, what we term a fake news effect. The consequences are severe, undermining oversight and enabling backsliding. Democratic accountability depends on reliable sources of information and elected officials’ commitment to upholding norms of conduct.

Building on Beilinson’s work, ‘constructible sheaves are holonomic’, we introduce the notion of holonomicity for étale sheaves, without assuming a priori constructibility. We establish the converse of Beilinson’s result, showing that holonomic sheaves are indeed constructible. This can be seen as an étale analogue of Kashiwara’s theorem on holonomic ${\mathcal D}_X$-modules.

We study the identification of individual-level associations when only aggregate data are available. We characterize the biases of, and relationships among, canonical ecological inference (EI) estimators. We use these results to develop a partial identification approach: monotone EI. The approach exploits information about one or both of the following conditional associations: (1) outcome differences between groups within the same neighborhood and (2) outcome differences within the same group between neighborhoods with different group compositions. We show how assumptions about the sign of these conditional associations, whether individually or in relation to one another, can yield informative sharp bounds. We illustrate our results using county-level data to study differences in COVID-19 vaccination rates among Republicans and Democrats in the United States.

In this work, the life cycle of Gnathostoma turgidum was studied both in natural temporary water bodies and under experimental conditions, with materials collected from the municipality of San Francisco Ixhuatán, Oaxaca. Adult nematodes inhabit the interstitial layers of the stomach in the definitive host (Didelphis virginiana) and release their eggs into the environment via faeces, typically in a dry environment. Under these conditions, the eggs remain quiescent until the onset of the rainy season. Development of early third-stage larvae occurs in cyclopoid copepods. Fry acts as transport and/or intermediate hosts, while frogs (Lithobates forreri) serve as obligatory intermediate hosts for advanced third-stage larvae, ultimately transmitting the parasites to the definitive host. Notably, the precocity phenomenon, typical of larval development in intermediate hosts, occurs in this species within the definitive host. Precocity is likely a response to host behaviour or other ecological factors that restrict transmission to narrow spatial and temporal windows. Adults die at the end of the rainy season. The marked seasonality of this species is mainly attributed to the combination of two factors: (i) the seasonal predation of frogs by the definitive host, and (ii) expulsion of adult stages as immune-mediated ‘self-cure’. This study represents the first documentation of birds acting as paratenic hosts for this nematode.