# Questions tagged [operators]

Questions about using or composing operators--functional mappings from one state or vector space to another.

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### Implicit definition of a coordinate in differential equation [duplicate]

I would like to solve the following differential equation $\frac{d^2 \psi(r_*)}{dr^2_*} + (\omega^2 - V(r)) \psi(r_*)=0$ and the boundary conditions are $\psi(\inf) = \psi(-inf) = 0$. The problem is ...
0answers
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1answer
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### Problem with defining a simple linear operator

I need to define a linear operator, which should have very simple linearity: myOp[Plus[f_, g_]] := myOp[f] + myOp[g] myOp[a_ f_[x_, t_]] := a myOp[f[x, t]] where ...
2answers
72 views

### Simplify differential expressions

One can differentiate a two dimensional vector like this, ClearAll["Global`*"] u[x_, y_] := {f[x, y], g[x, y]} Div[u[x, y], {x, y}] with output ...
1answer
37 views

### Define different actions for the same operator depending on the nature of its arguments

I am working with terms of the form A**B1**B2 where A, B1, and ...
1answer
99 views

### Defining an operator with given properties

In symbolic derivations with Mathematica, one often needs to define an operator with some desired properties, which will be used to stand for a general function or transform. For example, I would ...
1answer
54 views

### Define custom operator and specific application

I want to define a specific operator that will act in generic functions that depend, say, in the variable z. My problem is that I want when a specific function is ...
1answer
83 views

2answers
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### A list of operators in the For cycle

I'm pretty sure that analogous questions have been asked here a zillion of times, but... I think it is pretty straightforward from the code what I expect it to give: ...
0answers
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### Operator valued functions [duplicate]

For some parts of physics it is useful to define an operator valued function Take for example R[K_] := Sum[K[[j]] D[#, K[[j]]], {j, 1, 4}] It is supposed to be ...
3answers
130 views

### Noncommutative Expand into power series

I am new to Mathematica and am trying to apply it to quantum mechanics problems. The practice project I am dealing with now is considering quantum harmonic oscillator and ladder operator algebra ...
1answer
61 views

### Operator form for Histogram of multiple datasets?

I would like to plot a histogram for multiple datasets in a dataset query, but can't quite seem to make it work in operator notation: ...
1answer
142 views

### Associativity of upvalue

how can I ensure the following definition to be associative? Unprotect[Times]; a_ f[x_] + b_ f[y_] ^:= f[a x + b y] Protect[Times]; gives me ...
1answer
95 views

### Distribute operator

I have an operator defined by \[ScriptCapitalN] and want to Expand a term and then use ...
0answers
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### Add operator symbols to matrices in Wolfram [closed]

I am working with the matrices of the form $u = \begin{pmatrix}Y &y\\0 & Y\end{pmatrix}$, and I have an operator $a$ such that $au=\begin{pmatrix}Y & ay\\0 & Y\end{pmatrix}$. Since y ...
1answer
95 views

### Indefinite order of differential operator

In the latest version of Mathematica, D can compute derivatives of symbolic order, that is, the $n^{\text{th}}$ (partial) derivative, returning an expression ...
1answer
154 views

### Wick's theorem for Gaussian stochastic variables

I wonder whether there exists a clever way to implement Wick's theorem for Gaussian stochastic variables $\eta_{j_{i}}$ (with $\langle \eta_{j_{i}}\rangle=0$ for $\forall i$) which in general states: ...
1answer
100 views

### Commutator of block matrices

How to implement a commutator of matrices composed of operators? Background: Let $\hat A_{ij}$, $\hat B_{kl}$ be some sets of some operators. $\hat I$ is the identity operator. Their commutators are ...
0answers
36 views