Equivalence principleIn the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference. History of gravitational theory Something like the equivalence principle emerged in the early 17th century, when Galileo expressed experimentally that the acceleration of a test mass due to gravitation is independent of the amount of mass being accelerated.
Music of the United StatesThe United States' multi-ethnic population is reflected through a diverse array of styles of music. It is a mixture of music influenced by the music of Europe, Indigenous peoples, West Africa, Latin America, Middle East, North Africa, amongst many other places. The country's most internationally renowned genres are traditional pop, jazz, blues, country, bluegrass, rock, rock and roll, R&B, pop, hip-hop/rap, soul, funk, religious, disco, house, techno, ragtime, doo-wop, folk, americana, boogaloo, tejano, reggaeton, surf, and salsa, amongst many others.
Edwardian musical comedyEdwardian musical comedy was a form of British musical theatre that extended beyond the reign of King Edward VII in both directions, beginning in the early 1890s, when the Gilbert and Sullivan operas' dominance had ended, until the rise of the American musicals by Jerome Kern, Rodgers and Hart, George Gershwin and Cole Porter following the First World War. Between In Town in 1892 and The Maid of the Mountains, premiering in 1917, this new style of musical theatre became dominant on the musical stage in Britain and the rest of the English-speaking world.
R-treeR-trees are tree data structures used for spatial access methods, i.e., for indexing multi-dimensional information such as geographical coordinates, rectangles or polygons. The R-tree was proposed by Antonin Guttman in 1984 and has found significant use in both theoretical and applied contexts. A common real-world usage for an R-tree might be to store spatial objects such as restaurant locations or the polygons that typical maps are made of: streets, buildings, outlines of lakes, coastlines, etc.
Conceptual graphA conceptual graph (CG) is a formalism for knowledge representation. In the first published paper on CGs, John F. Sowa used them to represent the conceptual schemas used in database systems. The first book on CGs applied them to a wide range of topics in artificial intelligence, computer science, and cognitive science. Since 1984, the model has been developed along three main directions: a graphical interface for first-order logic, a diagrammatic calculus of logics, and a graph-based knowledge representation and reasoning model.
Universal enveloping algebraIn mathematics, the universal enveloping algebra of a Lie algebra is the unital associative algebra whose representations correspond precisely to the representations of that Lie algebra. Universal enveloping algebras are used in the representation theory of Lie groups and Lie algebras. For example, Verma modules can be constructed as quotients of the universal enveloping algebra. In addition, the enveloping algebra gives a precise definition for the Casimir operators.
Hierarchical database modelA hierarchical database model is a data model in which the data are organized into a tree-like structure. The data are stored as records which are connected to one another through links. A record is a collection of fields, with each field containing only one value. The type of a record defines which fields the record contains. The hierarchical database model mandates that each child record has only one parent, whereas each parent record can have one or more child records.
Mach's principleIn theoretical physics, particularly in discussions of , Mach's principle (or Mach's conjecture) is the name given by Albert Einstein to an imprecise hypothesis often credited to the physicist and philosopher Ernst Mach. The hypothesis attempted to explain how rotating objects, such as gyroscopes and spinning celestial bodies, maintain a frame of reference. The proposition is that the existence of absolute rotation (the distinction of local inertial frames vs.
Relational grammarIn linguistics, relational grammar (RG) is a syntactic theory which argues that primitive grammatical relations provide the ideal means to state syntactic rules in universal terms. Relational grammar began as an alternative to transformational grammar. In relational grammar, constituents that serve as the arguments to predicates are numbered in what is called the grammatical relations (GR) hierarchy. This numbering system corresponds loosely to the notions of subject, direct object and indirect object.
General covarianceIn theoretical physics, general covariance, also known as diffeomorphism covariance or general invariance, consists of the invariance of the form of physical laws under arbitrary differentiable coordinate transformations. The essential idea is that coordinates do not exist a priori in nature, but are only artifices used in describing nature, and hence should play no role in the formulation of fundamental physical laws. While this concept is exhibited by general relativity, which describes the dynamics of spacetime, one should not expect it to hold in less fundamental theories.
