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  2. Universal approximation theorem - Wikipedia

    en.wikipedia.org/wiki/Universal_approximation...

    Also, certain non-continuous activation functions can be used to approximate a sigmoid function, which then allows the above theorem to apply to those functions. For example, the step function works. In particular, this shows that a perceptron network with a single infinitely wide hidden layer can approximate arbitrary functions.

  3. Noether's second theorem - Wikipedia

    en.wikipedia.org/wiki/Noether's_second_theorem

    Specifically, the theorem says that if the action has an infinite-dimensional Lie algebra of infinitesimal symmetries parameterized linearly by k arbitrary functions and their derivatives up to order m, then the functional derivatives of L satisfy a system of k differential equations. Noether's second theorem is sometimes used in gauge theory.

  4. Free will theorem - Wikipedia

    en.wikipedia.org/wiki/Free_will_theorem

    The free will theorem of John H. Conway and Simon B. Kochen states that if we have a free will in the sense that our choices are not a function of the past, then, subject to certain assumptions, so must some elementary particles. Conway and Kochen's paper was published in Foundations of Physics in 2006. [1]

  5. Partition function (quantum field theory) - Wikipedia

    en.wikipedia.org/wiki/Partition_function...

    In quantum field theory, partition functions are generating functionals for correlation functions, making them key objects of study in the path integral formalism. They are the imaginary time versions of statistical mechanics partition functions , giving rise to a close connection between these two areas of physics.

  6. Gauge fixing - Wikipedia

    en.wikipedia.org/wiki/Gauge_fixing

    A particular choice of the scalar and vector potentials is a gauge (more precisely, gauge potential) and a scalar function ψ used to change the gauge is called a gauge function. [citation needed] The existence of arbitrary numbers of gauge functions ψ(r, t) corresponds to the U(1) gauge freedom of this theory. Gauge fixing can be done in many ...

  7. Uncertainty principle - Wikipedia

    en.wikipedia.org/wiki/Uncertainty_principle

    where = is the reduced Planck constant.. The quintessentially quantum mechanical uncertainty principle comes in many forms other than position–momentum. The energy–time relationship is widely used to relate quantum state lifetime to measured energy widths but its formal derivation is fraught with confusing issues about the nature of time.

  8. Variational method (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Variational_method...

    = if and only if is exactly equal to the wave function of the ground state of the studied system. The variational principle formulated above is the basis of the variational method used in quantum mechanics and quantum chemistry to find approximations to the ground state.

  9. General covariance - Wikipedia

    en.wikipedia.org/wiki/General_covariance

    Einstein recognized that the general principle of relativity should also apply to accelerated relative motions, and he used the newly developed tool of tensor calculus to extend the special theory's global Lorentz covariance (applying only to inertial frames) to the more general local Lorentz covariance (which applies to all frames), eventually ...