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Delta (/ ˈ d ɛ l t ə /; [1] uppercase Δ, lowercase δ; Greek: δέλτα, délta, ) [2] is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter dalet 𐤃. [ 3 ]
In mathematical analysis, the Dirac delta function (or δ distribution), also known as the unit impulse, [1] is a generalized function on the real numbers, whose value is zero everywhere except at zero, and whose integral over the entire real line is equal to one. [2] [3] [4] Thus it can be represented heuristically as
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.
Unlike the Kronecker delta function and the unit sample function [], the Dirac delta function () does not have an integer index, it has a single continuous non-integer value t. To confuse matters more, the unit impulse function is sometimes used to refer to either the Dirac delta function δ ( t ) {\displaystyle \delta (t)} , or the unit sample ...
In statistics, the delta method is a method of deriving the asymptotic distribution of a random variable. It is applicable when the random variable being considered can be defined as a differentiable function of a random variable which is asymptotically Gaussian .
Delta is a function of S, strike price, and time to expiry. [2] Therefore, if a position is delta neutral (or, instantaneously delta-hedged) its instantaneous change in value, for an infinitesimal change in the value of the underlying security, will be zero; see Hedge (finance).
In electrical engineering, dielectric loss quantifies a dielectric material's inherent dissipation of electromagnetic energy (e.g. heat). [1] It can be parameterized in terms of either the loss angle δ or the corresponding loss tangent tan(δ).
For the first term, ε ⁄ π (x 2 + ε 2) is a nascent delta function, and therefore approaches a Dirac delta function in the limit. Therefore, the first term equals ∓i π f(0). For the second term, the factor x 2 ⁄ (x 2 + ε 2) approaches 1 for |x| ≫ ε, approaches 0 for |x| ≪ ε, and is exactly symmetric about 0.