eCosmology

What does the greek letter delta mean in the quantum mechanics equation?

What does the greek letter delta mean in the quantum mechanics equation? please explane in details, and in easy terms, or at least ad what the words mean, also anything on the acual ecation would be helpful, thanks, also what do the commas mean?

Public Comments

1. change Δx means a (non-infinitesimal) change in x. (If the change becomes infinitesimal, δ and even d are used instead. Not to be confused with the symmetric difference, written ∆, above.)
2. I believe you're talking about the "upside down" delta in front of the term before the potential in the schrodinger equation... that is actually called a nabla. This symbol is used in mathematics to denote the 3 dimensional derivative called the gradient. It is (d/dx,d/dy,d/dz) ... when taking the derivative of a scalar like the potential it is called the gradient and creates a vector. ... in the schrodinger equation it is taken twice and is called the laplacian ... it has a much more complicated formula.
3. THE SHORT ANSWER, Typically, delta means 'change in'. THE LONG ANSWER. Depending on what specific equation and depending on which type of delta, depends on how you quantify the change. - Capital delta (a triangle) is used for big changes or more inaccurate changes/general approximations. E.g. /\x / /\t , distance travelled in a time, you would approximate to x/t and calculate an average velocity over a time. - Lower case delta with the top of the 'd' straight or curving to the right means a more accurate change, E.g. dx/dt would mean change in position with time and would be quantified by taking the differential of x with respect to time. This is used for more general purposes for example if you had an equation for the position and wanted to calculate the velocity algebraically. - Lower case delta with the top of the 'd' curled to the left means a partial change. E.g. dm/dx (imagine the 'd's are curled) If in an object the mass changed in 3D depending on x, y or z but you were only interested in the change in x. You would have an equation for the mass change with respect to x, y and z and by writing the dm/dx this way it would show that x was all you were interested in and you would treat the others as constants. If this did not fully answer your question, or if you would like more information on any of the above points, please don't hesitate to contact me. Mac - Astrophysicist