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In special relativity, electromagnetism and wave theory, the d'Alembert operator (denoted by a box: ), also called the d'Alembertian, wave operator, box operator or sometimes quabla operator [1] (cf. nabla symbol ) is the Laplace operator of Minkowski space .
The classical definition of angular momentum is =.The quantum-mechanical counterparts of these objects share the same relationship: = where r is the quantum position operator, p is the quantum momentum operator, × is cross product, and L is the orbital angular momentum operator.
In linear algebra (and its application to quantum mechanics), a raising or lowering operator (collectively known as ladder operators) is an operator that increases or decreases the eigenvalue of another operator. In quantum mechanics, the raising operator is sometimes called the creation operator, and the lowering operator the annihilation ...
The telephone played a major communications role in American history from the 1876 publication of its first patent by Alexander Graham Bell onward. In the 20th century the American Telephone and Telegraph Company (AT&T) dominated the telecommunication market as the at times largest company in the world, until it was broken up and replaced by a system of competitors.
There are many companies operating trains in the United Kingdom, including the operators of franchised passenger services, officially referred to as train operating companies (TOCs), as distinct from freight operating companies.
There were 578 A350 aircraft in service with 44 operators as of December 24, 2023. [1] The largest operators are Singapore Airlines (63), Qatar Airways (53), Cathay Pacific (42), Delta Air Lines (30), Air China (27), Thai Airways International (23) and Lufthansa (21).
[1] [2] [a] Such operators often preserve properties, such as continuity. For example, differentiation and indefinite integration are linear operators; operators that are built from them are called differential operators, integral operators or integro-differential operators. Operator is also used for denoting the symbol of a mathematical operation.
The Eurofighter Typhoon is a European multinational twin-engine, supersonic, canard delta wing, multirole fighter. [3] [4] The Typhoon was designed originally as an air-superiority fighter [5] and is manufactured by a consortium of Airbus, BAE Systems and Leonardo that conducts the majority of the project through a joint holding company, Eurofighter Jagdflugzeug GmbH.