Questions tagged [operators]
Questions about using or composing operators--functional mappings from one state or vector space to another.
284 questions
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Allow all functions to "commute" with custom operator except for differentiation
I'm trying to implement expected value angle brackets with all the rules of expected values built in, so that I can symbolically manipulate complicated expressions involving expected values, but I'm ...
2
votes
2
answers
150
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Securing the function definition containing CircleTimes
I'm trying to create a function that handles operators. The only thing left to do is implement the commutator. The minimal working example of func is
...
- 499
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1
answer
128
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Programmatic construction of a differential operator
I am trying to construct a linear differential operator programmatically. My approach is based on the worked-out example in the NonCommutativeMultiply documentation....
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763
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What is the precedence of logical operators in Wolfram Language?
I'm taking the enjoyable (but very high-level) Wolfram U course in Discrete Mathematics. That course gives the logical operator precedence as ...
- 667
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226
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Issue with Applying Derivative Operators in Matrix Multiplication in Mathematica [closed]
I am working on a matrix multiplication problem where I have two matrices, MatA and MatB. ...
- 115
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119
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Constructing operator $E_1 \otimes E_2 \otimes \cdots $
I am working with the Bose-Hubbard model and I want to construct the following operator as described below.
I have $L$ lattice sites where I want to construct this operator $e^{i*\phi*N_{R1}}$ where $...
- 127
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64
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1
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1
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125
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How to Compute the Hermitian Conjugate of Non-Commutative Products Symbolically in Mathematica?
I am working on symbolic quantum mechanics calculations in Mathematica, where I need to compute the Hermitian conjugate of expressions involving non-commutative operators. For instance, I have ...
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38
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How to Expand and Simplify a Complex Hamiltonian in Mathematica?
I am working on a quantum system and need to expand and simplify a Hamiltonian in Mathematica. The Hamiltonian is given as:
$$
H_{I} = \hbar \frac{\chi}{2} a_{1}^{\dagger 2} a_{1}^{2} + \left(i\hbar \...
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102
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Properties of conjugate transpose
I need to define the properties of conjugate transpose in mathematica:
Properties of Conjugate Transpose:
...
3
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2
answers
306
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Repeated partial derivatives
Big Mathematica novice here, hopefully this isn't too trivial?
I would like to define a function in Mathematica that takes $f$ as an input and produces repeated applications of the operator $\Theta_\...
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0
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189
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Variable-Size Matrix
How can I let Mathematica tell me that trace(Identity matrix)=n for n by n identity matrix? It's easy for human but what would a Mathematica code be?
A harder task: How can I let Mathematica tell me ...
- 101
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2
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169
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Problems with defining a R(c)-linear operator
My objective is to define an opeartor op such that for every rational function $f(c)$ of a fixed symbol c, $op(f(c) x)=f(c) op(x)$. What is a good way to implement ...
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145
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Clebsch–Gordan coefficient calculation for L-S basis in system of three particles
I am trying to calculate eq (A3)
...
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2
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1
answer
119
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General solution of a differential equation
I'm a beginner in Mathematica and I'm learning about dealing with differential equations but I'm stuck in this problem
What I tried to do is I observed that I have the same differential operator ...
10
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1
answer
215
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List[...] + Association[...], or Association[...] + List[...], when does the order matter?
Values of a list can be added to an association's values like so,
...
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1
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125
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How to define a composition of operators?
If I define P[x]=D[#,x]& (derivative operator)
How can I define another operator $Q$ such that $Q(f(x))=Pf(x)+a$ (for example)?
Thanks.
- 213
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93
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0
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58
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Taking sums of differential operators
If I define a differential operator:
T[i_] := D[#, x[i]] &
I am able to apply it multiple times to a function without any issues:
...
3
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3
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269
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Finite Differences:
I am having difficulty implementing finite differences in the correct columns of my code.
...
2
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1
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139
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Defining custom operators for indexed objects [closed]
I have some symbolic indexed objects $A_i$, $B_{ij}$, $C_{ijk}$, $D_{ijkl}$, etc.
I want to define a symbolic differential operator $\partial_{xy}$ that acts on these indexed objects in the following ...
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6
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686
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Applying several functions to the same argument
Is there a more concise way of achieving the following result (possibly without d |->)?
...
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2
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82
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How to define the square root of an operator [duplicate]
How can I define the operator $\sqrt{m^2-\frac{\partial^2}{\partial x^2}}$, such that it acts on the function $\psi(x)$ as follows: \begin{eqnarray*}
\sqrt{m^2-\frac{\partial^2}{\partial x^2}}\...
- 41
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3
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373
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Apply central difference formula to a variable twice
I am working with finite difference methods analytically and I would like to be able to perform operations on subscripted variables.
I would like to generate the following expression by applying a ...
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3
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370
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How can I construct a determinant-type differential operator?
How can I construct a determinant-type differential operator, where the multiplication of elements in the determinant represents the composition of multiple differential operators?
\begin{align*}
\...
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89
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Nested RowBox in MakeExpression reports error when I define my own curl operator, but the single RowBox in MakeExpression works well
I want to define my own vector notation so that the input \[Del] \[Cross] a outputs curl[a] while the ...
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2
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2
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352
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Doing algebra with differential operators
I'm doing some work on stochastic processes, where I use random functions which are defined by their properties over averages, i.e $$\langle f(t) \rangle =0 \\ \langle f(t) f(t')\rangle = \alpha(x,y) ...
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Could Mathematica analytically work with operators (such as $\nabla$) and vectors?
I have the following expression: $$(\nabla+\vec{P})^2$$
where $P=(r\cos\theta sin\phi,r^4\sin\theta,r\cos^3\phi)$
I would like to open the brackets and simplify the expression.
Are there in ...
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3
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197
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Is it possible to prevent two functions from commuting?
I have an expression of the following type:
x f[a] g[b]
where x is a number but f[a] and <...
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7
answers
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Can I use == to compare two list element wise?
I have the following lists Y and EY with actual and estimated outcomes.
...
- 333
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1
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187
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How to define an operator like ⊕？
For example, I define the circle plus as
a_\[CirclePlus]b_ := a + b^2;
a__\[CirclePlus]b_ := (a[[1 ;;-2]]\[CirclePlus]a[[-1]])\[CirclePlus]b;
But when I try
...
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1
answer
81
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How can I define an operator and plot its iterates?
I am trying to define a function (an operator) that "integrates then translates" a function. More specifically, for an input f[x], I want to integrate it as \int_0^x f[t] dt, then translate ...
- 113
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342
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How to define momentum operator for use with creation and annihilation operators in quantum mechanics
I am having trouble writing the momentum operator in the differential form to complete a piece of code shown here so that I can show a commutator [P,Q] = I .
Here is what I have done so far, and I ...
- 165
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2
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257
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Replace with non-commutative product
I'm trying to evaluate some scattering amplitudes terms in Mathematica using the spinor helicity formalism. For that, I need to turn products like $\epsilon_i\cdot k_j$ into spinor product which can ...
- 319
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282
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How to make a function with two patterns listable?
Suppose that I have a function that has two patterns:
disksConstantRadius[radius_][points_] := Disk[#, radius] & /@ points
(noting that this would be better---...
- 7,554
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0
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159
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How to define a vector operator?
I know how to define a single-variable differential operator like
Clear[Op]
Op[x_] := a D[#, {x, 1}] &
and I can do operations like
...
- 199
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What does the operation Map[({...}=#;{...})&, ] do?
With reference to the answer by @Bill to the question posted here, I am trying to understand the following three lines
...
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What's wrong with or? [closed]
Consider
Clear[x];
x = 2;
x < 2.9 || x > 3.1
This yields
True
So, everything is o. k. (interesting)
But when you replace ...
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1
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251
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How do I make an operator that acts on a function with the function's argument explicitly given?
I am trying to make a finite difference operator such that it would behave similar to the partial derivative $\partial_{x}f[x]$.
$\delta_n[f[n],m] := \frac{f[n+m]-f[n]}{m}\ .$
I couldn't find a way to ...
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1
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104
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Using Through function with vectors
I have the vectors defined as follows:
v1={x1,y1,z1};
v2={x2,y2,z2};
v12=v2-v1;
v21=v1-v2;
I am passing an integer function for iteration purpose as follows:
...
- 893
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1
answer
194
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How to give a property to a list of functions?
For example, I have defined a bunch of binary functions Sum1, Sum2, Prod1, ...
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1
answer
130
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Visualizing order of operations
TreeForm[HoldForm[ (9-2^2+10 8)/9]]
produces this:
Is there a way to use Divide instead of ...
- 540
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2
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171
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Product of different differential operators
I need to define a multivariable differential equation of the type
$$
\mathcal{D}=\Theta_1^2-z_1(-\Theta_1+\Theta_2+\Theta_3+\Theta_4)(1+\Theta_1+\Theta_2+\Theta_3+\Theta_4)\\
\;\;\;\;\;\;\;\;\;\;\;\;\...
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1
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77
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Confusing abnormalities observed when counting a specific operator in an expression [duplicate]
Recently I have met with some confusing abnormalities when trying to determine if there is a specific operator (usually Plus[] ) in an expression by programming. ...
- 493
2
votes
1
answer
115
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How to convert an expression of several variables into an operator
Given the expression
How can I define the following operator like
g[u_, v_] := eq1
The correct definition is
- 121
3
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2
answers
217
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How to subtract a list from certain sublists of a list? [closed]
I have a problem in doing an operation on this vector
{{2,3},{3,4},{5,6}}-{1,1}
I want to minus this to get the result
...
- 369
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190
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Second order differential operator in Mathematica
I am trying to write the code for the following expression in Mathematica:
$$\partial_{x} e^{-g x}=-g e^{-g x}+e^{-g x} \partial_{x}\,.$$
I was able to do so with the help of the following links with ...
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88
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How to write the expression for first order differential operator in Mathematica?
How to write the expression for first order differential operator in Mathematica?
What I mean to say that I want to evaluate
$$\frac{\partial}{\partial x}f(x)=f'(x)+f(x)\frac{\partial}{\partial x}.$$
...
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3
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1
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133
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Define an operator for long equations
I'm trying to workout a long expression with derivations, the thing is I can't seem to transfer this problem to code.
What I need is a operator $D = l^\mu \frac{\partial}{\partial x^\mu} $ where $l^\...
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What operator is this?
I was looking at some sample code in a YouTube video and saw an "operator" (not sure this is the right term) consisting of a horizontal bar with circles on the ends. I searched through the ...
