Questions tagged [operators]

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

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2
votes
4answers
129 views

define an operator

How is it possible to define the operator $(x+\frac{d}{dx})^n$ as a function of $n$? I use op[x_] = (x + D[#, x]) &; with the action on, for example, $\cos(...
2
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2answers
313 views

=== not working properly [closed]

I've been trying to check the identity using wolfram Mathematica and I've found the following ...
2
votes
2answers
574 views

Replacing values of a function

I have recently starting using Mathematica and have recently come to what seems as an impasse in my understanding of the language. If this is too "tell me how to do it" I would certainly understand. ...
2
votes
2answers
121 views

Column Operation - Subtract part of nested list from part of another nested list [duplicate]

I have two lists with x- and y-coordinates with different z-coordinates of the form {{x0, y0, z0_1}, {x1, y1, z1_1}, ..., {xn, yn, zn_1}} and ...
2
votes
2answers
115 views

Why is the square of a differential operator not evaluated automatically?

I defined an operator: py[f_[x, y]] := (I*h*D[f[x, y], y] - x) // Expand (not important, but it represents a simplified component of a quantum momentum in a ...
2
votes
1answer
40 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 ...
2
votes
1answer
610 views

Not commuting operator calculation

I am working on some operator calculation; I do not want the commutation relation. so xy ≠ yx. I found the mathematica code from https://reference.wolfram.com/language/ref/NonCommutativeMultiply....
2
votes
1answer
422 views

Operator operation

There are two basic operators r={x,y,z} and p=-I*h*{D[#,x] , D[#,y], D[#,z]} &. The angular momentum operator is defined as $...
2
votes
2answers
59 views

How can I concisely define a matrix-form partial derivative operator?

I have a vector $\boldsymbol{u}(x,y) = \begin{bmatrix} u_x(x,y) \\ u_y(x,y) \\ \end{bmatrix}.$ I would like to get $\boldsymbol{\sigma}(x,y) = \begin{bmatrix} \sigma_x \\ \sigma_y \\ \tau_{xy}...
2
votes
2answers
43 views

Defining a differential operator that acts on a non-commutative basis

Given a non-commutative basis ${x_0,x_1,x_2}$ I'd like to define a differential operator that acts as so $$ \Delta_i (\sum_{n=0}^\infty c_n x_i^n) = \sum_{n=1}^\infty c_n x_i^{n-1}, \quad \Delta_i ...
2
votes
3answers
138 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 ...
2
votes
1answer
433 views

Linearity of a function in Mathematica

I have a function which has something like myFunc[q,a state[c,d]] a could be anything, and I want to tell Mathematica that ...
2
votes
1answer
106 views

Distribute operator

I have an operator defined by \[ScriptCapitalN] and want to Expand a term and then use ...
2
votes
1answer
115 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 ...
2
votes
1answer
8k views

Difference between = and := [duplicate]

I wanted to know the difference between two operators: = and := I couldn't find the ":=" operator on the list at https://reference.wolfram.com/language/tutorial/Operators.html Can someone help? ...
2
votes
1answer
189 views

How to solve an operator form of an integral equation by iteration method? [closed]

How I can obtain the $n^{th}$ approximation of the following Operator form integral equation? $F(t)=A(t)+\int_0^tds B(s)F(s)$, where $A(t)=\bigg{(}\begin{matrix}t&0\\Cos(t)&1 \end{matrix}\...
2
votes
1answer
51 views

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 ...
2
votes
1answer
109 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 ...
2
votes
1answer
166 views

Expand a product of operators

Lets suppose I have a family of operators $f_i$, and unknown c-numbers $a,b,c$. I want to expand such products: $(f_1+f_2+c)(f_3+f_2+b)$ into $b c+b f_2+b f_1+c f_2+c f_3+f_2^2+f_1 f_2+f_2 f_3+f_1 f_3$...
2
votes
1answer
167 views

Operator product

I have this problem: I define the gradient operator as: gradiente = {D[#, x] &, D[#, y] &, D[#, z] &} Now, if I want to apply the operator on a ...
2
votes
1answer
204 views

Linear operator algebra: How to distinguish scalars and operators?

In the book "A Physicist' s Guide to Mathematica" Patrick Tam introduces symbolic rules for an algebra of linear operators. Mathematically the rules are as follows, where upper (lower) case letters ...
2
votes
0answers
62 views

Defining the Distributive Depth of an Operator

I am working on defining the relations between Bras and Kets in Mathematica, and I am using the CircleDot operator to represent multiplication. I seem to have some trouble defining how operations on ...
1
vote
1answer
277 views

Shorthand for operations?

Mathematica has a large number of built-in symbols, and I am unsure when there is a shorthand for the operation I am trying to perform. Question 1: Is there a shorthand for the function ...
1
vote
2answers
81 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 ...
1
vote
1answer
83 views

Reduction of differential operators

Suppose my code outputs the expression $$\frac{f^{(0,2)}(r,\phi )+r \left(f^{(1,0)}(r,\phi )+r f^{(2,0)}(r,\phi )\right)}{r^2}$$ This is simply the Laplacian $\nabla^2f(r, \phi)$. Is there a way ...
1
vote
1answer
164 views

How to do matrix operation if the first matrix is an operator? [duplicate]

Suppose I have: mM = {{D[#, x]&, D[#, y]&}, {D[#, y]&, D[#, z]&}} v = {f[x, y, z], g[x, y, z]} I want to get $u=mMv=\{\frac{\partial f}{\partial ...
1
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1answer
88 views

How to get Burgers hierarchy for any value of n

The Burgers hierarchy is defined by D[u[t, x], t] + α D[((∂/∂x) + u[t, x])^n u[t, x], x] How can I get the equation for the value of ...
1
vote
1answer
87 views

A program for finding the summation of an analytical expression

Consider the Baker-Hausdorff formula for two operators $A$ and $B$: $$e^BA e^{-B} =A+[B,A]+\frac{1}{2!}[B,[B,A]]+\frac{1}{3!}[B,[B,[B,A]]]+....,$$ where $[A,B]=AB-BA$. In the case of my problem, $[B,...
1
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1answer
179 views

Raising, lowering and number operators for Dirac notation

Starting from this very interesting post Defining quantum-mechanical Bra and Ket operations, i would like to implement raising, lowering and number operators, taking into account that they might be ...
1
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2answers
120 views

Defining an operator: Partially evaluate a Pure Function

I would like to define an operator that takes some parameters as input and returns a function. Here is an example: ...
1
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1answer
85 views

What are rules in Mathematica and what are its uses? [closed]

I'm new to Mathematica. I have been going through the official reference and came across this article on rules to which I was led by a Google search on how to ...
1
vote
1answer
60 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 ...
1
vote
1answer
237 views

Efficient way to give symbolic elements symmetry

I have a symbolic expression that represents a set of operators. These operators have quite a bit of symmetry to simplify expressions: ...
1
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0answers
56 views

Distribute && over a list [duplicate]

I cannot find an operator "RO" so that given a list, say {a,b,c}, RO[&&,{a,b,c}] produces a && b && c
1
vote
0answers
22 views

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 ...
1
vote
0answers
51 views

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 ...
1
vote
0answers
37 views

Del as a Differential Operator: (Matrix times Del) cross vector [duplicate]

I tried to reply to this answer, but don't have enough reputation points yet. Basically the poster constructed Del (i.e. $\nabla = \left( \frac{\partial}{\partial x}, \frac{\partial}{\partial y}, \...
1
vote
1answer
55 views

Finding a pattern in sum of products of two or more variables with subscripts

I am trying (so far unsuccessfully) to isolate terms in an expression which are product of variables with a specific subscript pattern (the b_,_'s). I want only terms for which the first subscript ...
1
vote
0answers
68 views

Superposition of the differential operators

My problem can be easily solved without Mathematica, however, I am curious how to do it in Mathematica. Moreover, I can be stuck with a similar, but more cumbersome problems in the future. Following ...
1
vote
0answers
55 views

Operator on a multivariable function in a sum

I need to define an operator that does as follow for any function $h_m$. $\qquad O[h_m](k,M,b,l_{max})=\sum_{l\neq (0,m)}^{l_{max}}il \left (h_l(k,M,b,l_{max}) b_{m-l}(k)- c_l\partial_k h_{m-l}(k,M,...
1
vote
0answers
69 views

How can I realize operator $\frac{D}{e^D-1}$ in Mathematica?

Especially if it is applied to an integral of a function. So, I need for a given function f[t] the following: $\frac{D}{e^D-1} \int_0^t f(t)dt |_{t=\omega}$
1
vote
2answers
131 views

Problem with Distribute and Composition

I'm having trouble with the following. When I try to expand an expression like Through[Distribute[g@*(f@*g + g@*f), Plus]@x] I get what I would expect. That is, ...
1
vote
0answers
99 views

Construct a univariate function pertaining to the space of $2 \times 2$ real matrices [closed]

Consider the space of uniformly distributed $2 \times 2$ real matrices \begin{equation} \left( \begin{array}{cc} a & b \\ c & d \\ \end{array} \right), \end{equation} with the restriction ...
1
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0answers
51 views

Operator Splitting and Taylore series

I am not a user of mathematica so I am not sure if what I want to do is possible. Imagine I have the following cauchy problem: $$\frac{dw}{dt} = F(t, w(t)) = f1(w(t), t) + f2(w(t), t)$$ where I have ...
1
vote
0answers
135 views

Is there any way to define a new binary operator? [duplicate]

I am looking to define a new operator that would work similarly to the + or - operator. My end goal is to make a dice operator for calculating random distributions in the normal d20 fashion (e.g. 5d6 ...
1
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0answers
78 views

custom precedence for custom infix operator with InfixNotation [duplicate]

I am trying to define several custom operators with custom precedence to implement geometric algebra. Loading the notation package << Notation` I can ...
1
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0answers
97 views

Define an operator without Built-in Meanings containing a Power function [duplicate]

I would like to define the following operator: $$ \left[T^{(j_{1})}\otimes U^{(j_{2})}\right]_{m}^{(j)}=\sum_{m_{1},m_{2}}\left\langle j_{1},m_{1};j_{2},m_{2}\big|j,m\right\rangle T_{m_{1}}^{j_{1}}U_{...
1
vote
0answers
216 views

Defining an operator

Let s be a positive integer and let DifferenceDelta be this function with step = 1. Define <...
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0answers
79 views

Parallelizing an associative binary operation

I have an associative binary operation '.', which I often use in this sort of way: result = expr1 . expr2 . expr3 . expr4 The ...
1
vote
0answers
75 views

Definition of differential operators [duplicate]

I am curious how differential operators are defined in Mathematica. More specifically, if the Laplacian function wasn't available, how would one go on to define such a function in Mathematica directly ...