Ernst Zermelo was a German mathematician known primarily for his foundational work in set theory. He was born on December 27, 1871, and died on May 21, 1953. Zermelo is most famous for developing the Zermelo-Fraenkel set theory (ZF), which is one of the most commonly used axiomatic set theories in mathematics.

Erwin Madelung is a significant figure in the field of physics, particularly known for his contributions to quantum mechanics and the development of the Madelung equations. These equations describe the motion of particles under the influence of a potential in a way that incorporates wave-like properties, reflecting the quantum nature of particles. The Madelung equations allow for a formulation of quantum mechanics that can be expressed in terms of hydrodynamic variables, linking quantum mechanics to classical fluid dynamics.

An **essential singularity** is a type of singular point in complex analysis that has specific properties. In a complex function \( f(z) \), a point \( z_0 \) is considered an essential singularity if the function behaves in a particularly wild manner as \( z \) approaches \( z_0 \). To understand this concept better, it's helpful to refer to the classification of singularities for complex functions.

An étale group scheme is a concept from algebraic geometry and the theory of group schemes. It can be understood in the context of scheme theory, which is a branch of mathematics that deals with geometric objects defined by polynomial equations, among other things. ### Group Schemes First, let's break down the term "group scheme." A group scheme is a scheme equipped with a group structure.

Eternal inflation is a concept in cosmology that arises from the theory of cosmic inflation, which posits that the universe underwent a rapid exponential expansion shortly after the Big Bang. In the traditional inflationary model, this period of inflation ends, leading to the formation of the universe as we know it. However, eternal inflation suggests a different scenario in which inflation does not end universally but continues indefinitely in some regions of space.

Ethical formalism, often associated with the philosophy of Immanuel Kant, is an ethical theory that emphasizes the importance of duty, rules, and principles in moral decision-making. Key features of ethical formalism include: 1. **Deontological Framework**: Ethical formalism is a deontological theory, meaning it focuses on the inherent rightness or wrongness of actions themselves, rather than their consequences. This approach holds that certain actions are morally obligatory regardless of the outcomes they produce.

Étienne Biéler was a Swiss painter, born on May 15, 1898, and passed away on January 23, 1987. He is known for his contributions to the Swiss art scene, particularly in the fields of painting, drawing, and printmaking. His work often reflects a blend of various styles and influences, including modernism.