Boot diskA boot disk is a removable digital data storage medium from which a computer can load and run (boot) an operating system or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting certain standards. While almost all modern computers can boot from a hard drive containing the operating system and other software, they would not normally be called boot disks (because they are not removable media).
Ladder operatorIn 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 operator. Well-known applications of ladder operators in quantum mechanics are in the formalisms of the quantum harmonic oscillator and angular momentum.
Rotation operator (quantum mechanics)This article concerns the rotation operator, as it appears in quantum mechanics. With every physical rotation , we postulate a quantum mechanical rotation operator which rotates quantum mechanical states. In terms of the generators of rotation, where is rotation axis, is angular momentum, and is the reduced Planck constant. Translation operator (quantum mechanics) The rotation operator , with the first argument indicating the rotation axis and the second the rotation angle, can operate through the translation operator for infinitesimal rotations as explained below.
Casimir elementIn mathematics, a Casimir element (also known as a Casimir invariant or Casimir operator) is a distinguished element of the center of the universal enveloping algebra of a Lie algebra. A prototypical example is the squared angular momentum operator, which is a Casimir element of the three-dimensional rotation group. More generally, Casimir elements can be used to refer to any element of the center of the universal enveloping algebra. The algebra of these elements is known to be isomorphic to a polynomial algebra through the Harish-Chandra isomorphism.
