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  2. Perturbation theory (quantum mechanics) - Wikipedia

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

    The first case will lead to the first theorem and the second case to the second theorem, which can be shown immediately by rearranging the terms. With the differential rules given by the Hellmann–Feynman theorems, the perturbative correction to the energies and states can be calculated systematically.

  3. Phase transition - Wikipedia

    en.wikipedia.org/wiki/Phase_transition

    First-order phase transitions exhibit a discontinuity in the first derivative of the free energy with respect to some thermodynamic variable. [6] The various solid/liquid/gas transitions are classified as first-order transitions because they involve a discontinuous change in density, which is the (inverse of the) first derivative of the free ...

  4. Cosmological phase transition - Wikipedia

    en.wikipedia.org/wiki/Cosmological_phase_transition

    This conclusion assumes the simplest scenario at the time of the transition, and first- or second-order transitions are possible in the presence of a quark, baryon or neutrino chemical potential, or strong magnetic fields. [12] [13] [14] The different possible phase transition types are summarised by the strong force phase diagram.

  5. Landau theory - Wikipedia

    en.wikipedia.org/wiki/Landau_theory

    Landau theory (also known as Ginzburg–Landau theory, despite the confusing name [1]) in physics is a theory that Lev Landau introduced in an attempt to formulate a general theory of continuous (i.e., second-order) phase transitions. [2]

  6. Second-order logic - Wikipedia

    en.wikipedia.org/wiki/Second-order_logic

    As a result, second-order logic has greater expressive power than first-order logic. For example, there is no way in first-order logic to identify the set of all cubes and tetrahedrons. But the existence of this set can be asserted in second-order logic as: ∃P ∀x (Px ↔ (Cube(x) ∨ Tet(x))). We can then assert properties of this set.

  7. Rate equation - Wikipedia

    en.wikipedia.org/wiki/Rate_equation

    The rate is first-order in one reactant (ethyl acetate), and also first-order in imidazole, which as a catalyst does not appear in the overall chemical equation. Another well-known class of second-order reactions are the S N 2 (bimolecular nucleophilic substitution) reactions, such as the reaction of n-butyl bromide with sodium iodide in acetone:

  8. Nondimensionalization - Wikipedia

    en.wikipedia.org/wiki/Nondimensionalization

    A variety of systems can be approximated as either first or second order systems. These include mechanical, electrical, fluidic, caloric, and torsional systems. This is because the fundamental physical quantities involved within each of these examples are related through first and second order derivatives.

  9. Second derivative - Wikipedia

    en.wikipedia.org/wiki/Second_derivative

    Informally, the second derivative can be phrased as "the rate of change of the rate of change"; for example, the second derivative of the position of an object with respect to time is the instantaneous acceleration of the object, or the rate at which the velocity of the object is changing with respect to