Lebrun manifold
The Lebrun manifold, also known as the Lebrun-Simpson manifold, is an important example in the study of Riemannian geometry and in the context of \(4\)-manifolds. It is a complex manifold that can be described as a Kähler surface. Specifically, it is notable for being a non-Kähler symplectic manifold, and it can be constructed as a particular type of complex algebraic surface.
HABU equivalent
The term "HABU" can refer to different things in different contexts, but it is most commonly associated with a type of venomous snake found in Southeast Asia, particularly the "Habus" of Japan, such as the Okinawa habu (Protobothrops flavoviridis).
Bent's rule
Bent's rule is a principle in chemistry that pertains to the hybridization of atomic orbitals in heteroatomic molecules, particularly those containing a central atom bonded to different substituents. Formulated by Linus Pauling and named after the chemist Robert S. Bent, the rule states that: "In a molecule, the more electronegative atoms will tend to occupy positions that allow for greater p-character in the hybrid orbitals formed by the central atom.
Vicinal (chemistry)
In chemistry, the term "vicinal" typically refers to two functional groups or substituents that are located on adjacent carbon atoms in a molecule. The term is often used in the context of vicinal diols, where two hydroxyl (-OH) groups are attached to two adjacent carbon atoms.
Bond softening
Bond softening refers to a phenomenon observed in the context of materials science and solid-state physics, particularly in the study of mechanical properties of materials. It denotes a reduction in the strength of atomic or molecular bonds in a material, which can lead to a decrease in its overall mechanical strength and stiffness.
Gaussian orbital
A Gaussian orbital is a type of mathematical function used to represent atomic orbitals in quantum chemistry and computational chemistry.
Center of mass
The center of mass (COM) is a point in a system of particles or a continuous mass distribution where the total mass of the system can be considered to be concentrated for the purpose of analyzing motion. It is the balance point of the mass distribution, meaning that if a system were to be suspended at this point, it would remain in equilibrium.
Empedocles
Empedocles was a pre-Socratic Greek philosopher who lived around 495-435 BCE. He is best known for his work in philosophy and natural science, particularly for introducing the idea that all matter is composed of four fundamental elements: earth, water, air, and fire. He proposed that these elements are in constant motion and interact through two opposing forces he called Love (philia), which brings things together, and Strife (neikos), which separates them.
Clairaut's relation, also known as Clairaut's theorem, is a fundamental result in differential geometry that relates the curvature of a surface to the derivatives of the surface's height function. Specifically, it applies to surfaces of revolution, which are surfaces generated by rotating a curve about an axis.
Differentiable stack
A **differentiable stack** is a concept arising from the fields of differential geometry, algebraic topology, and category theory, particularly in the context of homotopy theory and advanced mathematical frameworks like derived algebraic geometry. In general, a **stack** is a categorical structure that allows for the systematic handling of "parametrized" objects, facilitating the study of moduli problems in algebraic geometry and related fields.
Diffiety
As of my last update in October 2023, "Diffiety" does not appear to be a widely recognized term in academic or popular culture. It's possible that it could be a misspelling, a new concept, or a niche term that has emerged after my last update.
Dirac structure
Dirac structure refers to a mathematical framework used in the context of quantum mechanics and quantum field theory, particularly within the realm of Dirac's formulation of quantum mechanics. It is associated with the treatment of spinor fields, which are essential for describing particles with spin, such as electrons.
Double tangent bundle
The double tangent bundle is a mathematical construction in differential geometry that generalizes the notion of tangent bundles. To understand the double tangent bundle, we first need to comprehend what a tangent bundle is. ### Tangent Bundle For a smooth manifold \( M \), the tangent bundle \( TM \) is a vector bundle that consists of all tangent vectors at every point on the manifold.
Lie algebroid
A Lie algebroid is a mathematical structure that generalizes the concepts of Lie algebras and tangent bundles in differential geometry. It arises in various fields such as Poisson geometry, the study of foliations, and in the theory of dynamical systems. Lie algebroids provide a way to describe the infinitesimal symmetry of a manifold in a coherent algebraic framework.
Shape of the universe
The shape of the universe is a complex topic in cosmology and depends on several factors, including its overall geometry, curvature, and topology. Here are the primary concepts regarding the shape of the universe: 1. **Geometry**: - **Flat**: In a flat universe, the geometry follows the rules of Euclidean space. Parallel lines remain parallel, and the angles of a triangle sum to 180 degrees.
Siegel upper half-space
The Siegel upper half-space, typically denoted as \( \mathcal{H}_g \), is a concept from several complex variables and algebraic geometry. It is a generalization of the upper half-plane concept found in one complex variable and is an important object in the study of several complex variables, algebraic curves, and arithmetic geometry.
Theorema Egregium
Theorema Egregium, which is Latin for "Remarkable Theorem," is a fundamental result in differential geometry, particularly in the study of surfaces. It was formulated by the mathematician Carl Friedrich Gauss in 1827. The theorem states that the Gaussian curvature of a surface is an intrinsic property, meaning it can be determined entirely by measurements made within the surface itself, without reference to the surrounding space.
Warped geometry
Warped geometry refers to a concept in geometry and theoretical physics where the structure of space is not uniform but instead distorted or "warped" in a way that can affect the behavior of objects within that space. This idea often arises in contexts involving general relativity, string theory, and higher-dimensional theories. In general relativity, gravity is interpreted as the curvature of spacetime caused by mass and energy.
Bateman transform
The Bateman transform, named after the mathematician H. Bateman, is a mathematical technique used in the context of solving certain types of integral transforms and differential equations. It is particularly useful in simplifying the computation of integrals that involve exponentials, polynomials, and special functions. The Bateman transform can be applied to the analysis of systems in physics, engineering, and applied mathematics, especially in areas such as signal processing and control theory.
In Riemannian geometry, the exponential map is a crucial concept that connects the local geometric properties of a Riemannian manifold to its global structure. Specifically, it describes how to move along geodesics (the generalization of straight lines to curved spaces) starting from a given point on the manifold.