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  2. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    The delta function was introduced by physicist Paul Dirac, and has since been applied routinely in physics and engineering to model point masses and instantaneous impulses. It is called the delta function because it is a continuous analogue of the Kronecker delta function, which is usually defined on a discrete domain and takes values 0 and 1.

  3. Delta potential - Wikipedia

    en.wikipedia.org/wiki/Delta_potential

    The delta potential is the potential = (), where δ(x) is the Dirac delta function. It is called a delta potential well if λ is negative, and a delta potential barrier if λ is positive. The delta has been defined to occur at the origin for simplicity; a shift in the delta function's argument does not change any of the following results.

  4. Delta rule - Wikipedia

    en.wikipedia.org/wiki/Delta_rule

    While the delta rule is similar to the perceptron's update rule, the derivation is different. The perceptron uses the Heaviside step function as the activation function g ( h ) {\\displaystyle g(h)} , and that means that g ′ ( h ) {\\displaystyle g'(h)} does not exist at zero, and is equal to zero elsewhere, which makes the direct application ...

  5. Lagrangian mechanics - Wikipedia

    en.wikipedia.org/wiki/Lagrangian_mechanics

    This procedure does increase the number of equations to solve compared to Newton's laws, from 3N to 3N + C, because there are 3N coupled second-order differential equations in the position coordinates and multipliers, plus C constraint equations. However, when solved alongside the position coordinates of the particles, the multipliers can yield ...

  6. Delta-v - Wikipedia

    en.wikipedia.org/wiki/Delta-v

    Delta-v (also known as "change in velocity"), symbolized as and pronounced /dɛltə viː/, as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver.

  7. Dirac equation - Wikipedia

    en.wikipedia.org/wiki/Dirac_equation

    In particle physics, the Dirac equation is a relativistic wave equation derived by British physicist Paul Dirac in 1928. In its free form, or including electromagnetic interactions, it describes all spin-1/2 massive particles, called "Dirac particles", such as electrons and quarks for which parity is a symmetry.

  8. Kronecker delta - Wikipedia

    en.wikipedia.org/wiki/Kronecker_delta

    The generalized Kronecker delta or multi-index Kronecker delta of order is a type (,) tensor that is completely antisymmetric in its upper indices, and also in its lower indices. Two definitions that differ by a factor of p ! {\displaystyle p!} are in use.

  9. Equations of motion - Wikipedia

    en.wikipedia.org/wiki/Equations_of_motion

    There are two main descriptions of motion: dynamics and kinematics.Dynamics is general, since the momenta, forces and energy of the particles are taken into account. In this instance, sometimes the term dynamics refers to the differential equations that the system satisfies (e.g., Newton's second law or Euler–Lagrange equations), and sometimes to the solutions to those equations.