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  2. Momentum operator - Wikipedia

    en.wikipedia.org/wiki/Momentum_operator

    The derivation in three dimensions is the same, except the gradient operator del is used instead of one partial derivative. In three dimensions, the plane wave solution to Schrödinger's equation is: = and the gradient is = + + = (+ +) = where e x, e y, and e z are the unit vectors for the three spatial dimensions, hence ^ =

  3. Notation in probability and statistics - Wikipedia

    en.wikipedia.org/wiki/Notation_in_probability...

    Greek letters (e.g. θ, β) are commonly used to denote unknown parameters (population parameters). [3]A tilde (~) denotes "has the probability distribution of". Placing a hat, or caret (also known as a circumflex), over a true parameter denotes an estimator of it, e.g., ^ is an estimator for .

  4. Projection matrix - Wikipedia

    en.wikipedia.org/wiki/Projection_matrix

    A matrix, has its column space depicted as the green line. The projection of some vector onto the column space of is the vector . From the figure, it is clear that the closest point from the vector onto the column space of , is , and is one where we can draw a line orthogonal to the column space of .

  5. Canonical commutation relation - Wikipedia

    en.wikipedia.org/wiki/Canonical_commutation_relation

    According to the correspondence principle, in certain limits the quantum equations of states must approach Hamilton's equations of motion.The latter state the following relation between the generalized coordinate q (e.g. position) and the generalized momentum p: {˙ = = {,}; ˙ = = {,}.

  6. Vector fields in cylindrical and spherical coordinates

    en.wikipedia.org/wiki/Vector_fields_in...

    Vectors are defined in cylindrical coordinates by (ρ, φ, z), where . ρ is the length of the vector projected onto the xy-plane,; φ is the angle between the projection of the vector onto the xy-plane (i.e. ρ) and the positive x-axis (0 ≤ φ < 2π),

  7. p-value - Wikipedia

    en.wikipedia.org/wiki/P-value

    In null-hypothesis significance testing, the p-value [note 1] is the probability of obtaining test results at least as extreme as the result actually observed, under the assumption that the null hypothesis is correct. [2] [3] A very small p-value means that such an extreme observed outcome would be very unlikely under the null hypothesis.

  8. Position operator - Wikipedia

    en.wikipedia.org/wiki/Position_operator

    In literature, more or less explicitly, we find essentially three main directions to address this issue. The position operator is defined on the subspace D X {\displaystyle D_{X}} of L 2 {\displaystyle L^{2}} formed by those equivalence classes ψ {\displaystyle \psi } whose product by the embedding x {\displaystyle \mathrm {x} } lives in the ...

  9. Unit vector - Wikipedia

    en.wikipedia.org/wiki/Unit_vector

    The notations (î, ĵ, k̂), (x̂ 1, x̂ 2, x̂ 3), (ê x, ê y, ê z), or (ê 1, ê 2, ê 3), with or without hat, are also used, [1] particularly in contexts where i, j, k might lead to confusion with another quantity (for instance with index symbols such as i, j, k, which are used to identify an element of a set or array or sequence of ...