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Semi-classical Music
Semiclassical may refer to: * Semiclassical gravity, an approximation to the theory of quantum gravity * Semiclassical physics, a theory in which one part of a system is described quantum-mechanically whereas the other is treated classically * Beautiful music, a radio format * Semi-classical music, a style of music of the Indian subcontinent {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiclassical Gravity
Semiclassical gravity is an approximation to the theory of quantum gravity in which one treats matter and energy fields as being quantum and the gravitational field as being classical. In semiclassical gravity, matter is represented by quantum matter fields that propagate according to the theory of quantum fields in curved spacetime. The spacetime in which the fields propagate is classical but dynamical. The dynamics of the theory is described by the ''semiclassical Einstein equations'', which relate the curvature of spacetime that is encoded by the Einstein tensor G_ to the expectation value of the energy–momentum tensor \hat T_ (a quantum field theory operator) of the matter fields, i.e. : G_ = \frac \left\langle \hat T_ \right\rangle_\psi, where ''G'' is the gravitational constant, and \psi indicates the quantum state of the matter fields. Energy–momentum tensor There is some ambiguity in regulating the energy–momentum tensor, and this depends upon the curvatu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiclassical Physics
In physics, semiclassical refers to a theory in which one part of a system is described quantum mechanically, whereas the other is treated classically. For example, external fields will be constant, or when changing will be classically described. In general, it incorporates a development in powers of the Planck constant, resulting in the classical physics of power 0, and the first nontrivial approximation to the power of (−1). In this case, there is a clear link between the quantum-mechanical system and the associated semi-classical and classical approximations, as it is similar in appearance to the transition from physical optics to geometric optics. History Max Planck was the first to introduce the idea of quanta of energy in 1900 while studying black-body radiation. In 1906, he was also the first to write that quantum theory should replicate classical mechanics at some limit, particularly if the Planck constant ''h'' were infinitesimal. With this idea he showed tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |