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  2. Perturbation theory (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Perturbation_theory...

    Perturbation theory is an important tool for describing real quantum systems, as it turns out to be very difficult to find exact solutions to the Schrödinger equation for Hamiltonians of even moderate complexity.

  3. Kubo formula - Wikipedia

    en.wikipedia.org/wiki/Kubo_formula

    The brackets mean an equilibrium average with respect to the Hamiltonian . Therefore, although the result is of first order in the perturbation, it involves only the zeroth-order eigenfunctions, which is usually the case in perturbation theory and moves away all complications which otherwise might arise for >.

  4. Kinetics (physics) - Wikipedia

    en.wikipedia.org/wiki/Kinetics_(physics)

    In physics and engineering, kinetics is the branch of classical mechanics that is concerned with the relationship between the motion and its causes, specifically, forces and torques. [ 1 ] [ 2 ] [ 3 ] Since the mid-20th century, the term " dynamics " (or " analytical dynamics ") has largely superseded "kinetics" in physics textbooks, [ 4 ...

  5. Order of approximation - Wikipedia

    en.wikipedia.org/wiki/Order_of_approximation

    The zero of "zeroth-order" represents the fact that even the only number given, "a few", is itself loosely defined. A zeroth-order approximation of a function (that is, mathematically determining a formula to fit multiple data points) will be constant, or a flat line with no slope: a polynomial of degree 0. For example,

  6. Zero-point energy - Wikipedia

    en.wikipedia.org/wiki/Zero-point_energy

    In ordinary atomic physics, the zero-point energy is the energy associated with the ground state of the system. The professional physics literature tends to measure frequency, as denoted by ν above, using angular frequency, denoted with ω and defined by ω = 2πν.

  7. Zero order - Wikipedia

    en.wikipedia.org/wiki/Zero_order

    Zero order reaction. Zero-order process (statistics), a sequence of random variables, each independent of the previous ones; Zero order process (chemistry), a chemical reaction in which the rate of change of concentration is independent of the concentrations; Zeroth-order approximation, an approximation of a function by a constant

  8. Glossary of physics - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_physics

    A branch of physics dealing with physical phenomena at microscopic scales, where the action is on the order of the Planck constant. Quantum mechanics departs from classical mechanics at atomic and subatomic length scales, and provides a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy ...

  9. Quantum thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Quantum_thermodynamics

    By making precise the definition of thermal operations, the laws of thermodynamics take on a form with the first law defining the class of thermal operations, the zeroth law emerging as a unique condition ensuring the theory is nontrivial, and the remaining laws being a monotonicity property of generalised free energies. [31] [32]