For questions about symbolic computation, as opposed to numerical computations.

learn more… | top users | synonyms

4
votes
0answers
69 views

Integral formula for the inverse Laplace transform doesn't work?

The direct implementation of the definition of the inverse Laplace transform using Integrate fails in the following case: ...
1
vote
1answer
60 views

how to calculate the covariance of sample central moments

$\bar{x}= \sum_{i=1} ^{n} \frac{1}{n}x_{i}$ $m_1=\sum _{i=1} ^{n} \frac{1}{n} (x_{i}-\bar{x})$ $m_2=\sum _{i=1} ^{n} \frac{1}{n} (x_{i}-\bar{x})^2 $ $m_3=\sum _{i=1} ^{n} ...
1
vote
0answers
39 views

Calculating perturbative expansion in qft

Is there an easy way to use mathematica to take functional derivatives to do perturbation theory in qft? I know there is a package for functional derivatives, but can I get an example of how to use it ...
3
votes
2answers
49 views

Using LeviCivitaTensor

I have 2 questions about using LeviCivitaTensor, based on the following session: The signs for the cross product seems to come out "opposite" of what I expected. Why is that? Did I miss anything? ...
0
votes
1answer
36 views

Root: Simplifying symbolic expression

I'm doing calculations with a lot of symbols, which don't always gives nice expressions. Now I have a solution with a Root-expression, where the coefficients are symbolic, e.g. ...
2
votes
1answer
70 views

How to implement symbolic Ramanujan's summation in Mathematica?

How to implement Ramanujan's summation in symbolic form in Mathematica? For instance, I want as input the function $f(x)=x$, as output $-1/12$, as input $f(x)=1/x$, as output $\gamma$ (Euler's ...
18
votes
1answer
436 views

Analogue for Maple's dchange - change of variables in differential expressions

Maple owns an interesting function called dchange which can change the variables of differential equations, but there seems to be no such function in Mathematica. ...
5
votes
1answer
45 views

How do I perform exact unit conversions with irrational conversion factors?

Suppose I want to express $3h$ in units of $\hbar$ (where $h$ and $\hbar$ are the Planck constant and reduced Planck constant, respectively). By definition, $h = 2\pi\hbar$, but when I attempt this ...
4
votes
1answer
88 views

Checking if a symbolic matrix is positive semi-definite

As far as I can tell, there is no way to tell the builtin PositiveSemidefiniteQ about assumptions on symbols. For example, the matrix ...
0
votes
1answer
43 views

Is there a function or option to collect factors under one radical sign?

One of the things that frustrates me most about Mathematica's symbolic manipulations is the fact that output is often presented quite differently than most humans would write it. This is especially ...
1
vote
0answers
28 views

How can I get symbolic orthonormal eigenvectors for 3 by 3 hermitian matrix?

Using the following syntax, I can obtain the symbolic eigenvalues and eigenvectors of the following Hermitian matrix (a,b,c,d are all real parameters): ...
2
votes
1answer
109 views

Can Mathematica solve this type of recurrence?

I have the following recursively defined equation: ...
0
votes
1answer
27 views

How to get the modulus of following complex number

I want to get the modulus of following (1+(x+I*y)/2+(x+I*y)^2/12)/(1-(x+I*y)/2+(x+I*y)^2/12) I use ...
0
votes
0answers
24 views

Find out domain after change of variable in integral of d dimensions

Is there a way to tell Mathematica the change of variable you want to do and getting back the corresponding domain? The specific problem I am trying to solve is $\quad \quad\int_{-1}^0 ...
4
votes
2answers
120 views

Well-defined symbolic integral leading to ConditionalExpression

I would like to determine a closed-form expression for the following symbolic integral $$ \int_{-1/2}^{1/2} \!\!\!\! \mathrm{d} x \int_{-1/2}^{1/2} \!\!\!\! \mathrm{d} y \, \frac{1 + b x + c y}{1 + e ...
5
votes
1answer
56 views

Rearrange an algebraic expression so that each variable appears only once

Mathematica gave me a solution to an equation in this form: ans1 = (b c)/(a - a c + b c) $\text{ans1} = \frac{b c}{a - a c + b c}$ From solving the same equation ...
1
vote
1answer
73 views

Working with derivative of conjugate of a complex number

I have a complex function, lets say $g(x)$. I want to take its and its conjugate's derivative. I need the solution of derivative which must be symbolically and computationally efficient. Lets take an ...
3
votes
3answers
89 views

How to Integrate trivial products of DiracDelta

A long while ago I was able to integrate with Mathematica: $$\int_0^1 \delta(1-x)\delta(x) f(x) \,dx = 0$$ using ...
4
votes
1answer
48 views

Simplify complex answer given by DSolve[]

I tried the technique in this question, but that did not work for the solution given by the MWE: DSolve[{f'[t] + f[t]*g[t] == h[t], f[0] == f0}, {f[t]}, t] How ...
2
votes
1answer
88 views

simplifying integrals for multiple exponentials

This is somewhat related to this question, but applied to products of Exp[]. For example, I have a symbolic expression containing terms like $Exp[\int_0^1 ...
0
votes
1answer
39 views

Working with symbolic values in Quantities [duplicate]

I have the following expression: x Quantity[y, ("Milliwatts"*"Seconds"^2)/"Joules"] If I try to convert this to the SI unit, I would expect to get ...
5
votes
1answer
103 views

Slow-down encountered when using NMinimize with a compiled function

I'm minimizing a large function. Evaluating the function is very slow symbolically but using Compile I can get ~100x speed-up on this step. However, despite this, the NMinimize process is only ...
0
votes
1answer
77 views

How to make Mathematica show intermediate steps in integral [duplicate]

I want to know how Mathematica evaluates this integral: $PV \int _ {0} ^ {i \infty} d \tau \, \frac{e^{-\frac{\tau^2}{2 M^2}}(b^2 - 3 τ^2)^2 (|b^2+\tau^2|-(b^2-\tau^2))}{\tau (\tau^2 - b^2)}$, where ...
0
votes
1answer
35 views

Using Coefficient to pick combinations of parameters in an expression

I have the expression $$ c \partial_{\chi} u = \mu u - \nu v - (u + \beta v)|A|^2 + (\partial_{\chi}^2 u - \alpha \partial_{\chi}^2 v) + \gamma u \\ c \partial_{\chi} v = \mu v + \nu u - (v - \beta ...
0
votes
0answers
151 views

Solving Symbolically Equations with Vectors and Matrices

I want to solve equations with vector variables and vector/matrix parameters symbolically. As a basic example I would like to be able to solve something like $[I-aG]x=b$ where $a,b \in \mathbb{R}^l$ ...
0
votes
0answers
40 views

Minimize doesn't solve a problem with many symbols

I am trying to solve a simple constrained optimization problem. I am running the code ...
1
vote
1answer
64 views

SymbolicC Simplified Displayed

How might I display a simplified SymbolicC below. For example in the following example ...
10
votes
2answers
496 views

Is there a way to identify a symbolic fraction?

Is there a way to use Head to detect a symbolic fraction? In particular I find, Head[a/b] Head[1/5] Times Rational ...
0
votes
0answers
34 views

Substitute all known values in matrix [duplicate]

There is probably a very simple way of doing the following, but I cannot find it. I have a an array of symbolic variables: coefficients = Array[c, 3] I then ...
1
vote
1answer
56 views

Defining a matrix with the symmetry Transpose[A(q)]=A(-q)

I am trying to construct a symbolic matrix with the following property- $$ \left(D_{3\times3}(q)\right)^T = D_{3\times3}(-q) $$ Note that for $q\in \mathbb{R}$, $D(q)$ would be hermitian. So far i ...
3
votes
3answers
115 views

Differential equation with a Heavisidetheta function running for ever

So I'm trying to get the solution of the following differential equation: ...
1
vote
1answer
82 views

Strange timings of integrals involving Hermite's polynomials

I have used Mathematica to calculate tunneling for quantum harmonic oscillator. The code is simple: ...
2
votes
2answers
94 views

Let mathematica combine integral limits

Is there a way to teach mathematica to combine integral limits according to $\int_a^b f dx+\int_b^c f dx=\int_a^cf dx$ to simplify expressions like $\int_0^1 f[t] dt+\int_1^x (1+f[t]) dt$ to $\int_0^t ...
2
votes
1answer
114 views

Symbolic quadratic constrained maximization with non-negativity constraints?

Dear Mathematica users, I attempted to maximize the below quadratic function K, subject to x1+x2<=A, and a series of ...
0
votes
1answer
63 views

Issue with integration from 0 to infinity with constants [closed]

I am trying to take the integration for $\int_0^{+\infty}e^{-\alpha t}sin(\beta t)d t$. Here is a screen shot of what I did: The solution to this integeation should be ...
1
vote
1answer
34 views

hold specific pattern in symbolic calculation

I encounter some questions when I try to simplify a symbolic expression using Mathematica. For example, I got an intermediate expression ...
11
votes
1answer
201 views

What does f_[whoCalled]^:=f really mean?

I came across the following post by John Doty in this Google Groups discussion: On Friday, January 11, 2013 8:23:16 PM UTC-7, amzoti wrote: It is clear the Mathematica uses Lisp as one ...
0
votes
0answers
74 views

Is it possible to get a symbolic expression from FindRoot?

I need to have an expression where the solution from FindRoot (or another solver) depends on one or more parameters. Let's say I have a polynomial of second ...
3
votes
2answers
208 views

Help at speeding up simplification/nested symbolic integration

I have the following problem: I want to compute an integral of the form $$\int\limits_0^{t_g}\mathrm{d}t_2\int\limits_0^{t_2}\mathrm{d}t_1\left[A(t_1),A(t_2)\right],$$where $\left[B,C\right]=BC-CB$ is ...
3
votes
2answers
109 views

Eigenvectors of large symbolic matrix

I have large symbolic matrix of order 32 x 32 given as ...
2
votes
0answers
67 views

Integrate with Subscript: does this crash your kernel too?

I encountered some strange behaviour running v10.0.1 on a Mac Pro, while working with Integrate and Subscript. Starting from a ...
2
votes
3answers
109 views

Symbolic integration conditional bug?

I just ran across this: Assuming[x > 0, Integrate[1/t^2, {t, 1, x}]] gives the output ...
2
votes
1answer
74 views

How to define the symbolic expression $V = \frac{1}{N} \sum_{i=1}^N ( y_i(g) - z_i)^2$ in Mathematica?

I want to define this expression symbolically: $V = \frac{1}{N} \sum_{i=1}^N ( y_i(g) - z_i)^2$ in which $\{y_i(g)\}_{i=1}^N$ is to be understood as a symbolic sequence that depends on a vector $g$. ...
0
votes
1answer
45 views

Taking function output as shown, and processing it regardless of its history

I am making some symbolical calculations for my quantum chemistry class. I am supposed to build a wave function composed of multiple other functions, each of which is also composite of some lower ...
1
vote
0answers
80 views

Summing the probability distribution to 1 to convince myself

I have worked out a probability distribution and want to check its sum which is necessarily 1. First we write $$ r \triangleq \frac{(2 \lambda + \mu)^2}{2(\mu + \lambda)^2}, \quad s \triangleq ...
1
vote
1answer
123 views

Why do expressions with D and Derivative giving so different results for me?

I tried to express with Derivative the same I expressed earlier by D, but failed: ...
2
votes
0answers
80 views

How does Mathematica resolve symbolic systems of inequalities?

Before getting into my (probably annoying) question, let me provide some context: I recently started using Mathematica to automatically perform stability analyses that I previously did by hand. A ...
5
votes
3answers
288 views

Comparison of Dispatch objects ureliable in Mathematica 10

In 2008 I wrote a group theory package. I've recently started using it again, and I found that one (at least) of my functions is broken in Mathematica 10. The problem is complicated to describe, but ...
1
vote
2answers
140 views

DSolve bvlim error due to Boundary condition at infinity

I am solving an Ode using Mathematica that has boundary condition at infinity which is why Mathematica is showing error message. Please help to tackle this problem. ...
2
votes
1answer
106 views

How to get a more compact form of this probability calculation?

Inspired by the probability calculation here, I am trying to solve a little general one: $$\mathbb{P} (\sum_{i=1}^{m-1} A_i + \sum_{i=1}^{m} S_i < L < \sum_{i=1}^{m} A_i + \sum_{i=1}^{m+1} ...