Questions about the function Assuming[], the $Assumptions system variable, and the Assumptions option of functions such as Simplify[] and Integrate[].

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1
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0answers
30 views

Hidden assumption in Mathematica integration [duplicate]

If I do Integrate[Exp[I*omega*t],t], it gives me $\frac{1}{\omega} e^{i \omega t}$, as expected in most of the cases, except when $\omega$ is 0. Mathematica seems ...
0
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0answers
37 views

vector with conditions/assumptions

Probably I just don't get it and it is because it's friday morning. I want to create a systems description fSys = {{x2}, {u g[x] + h[x]}}; However, there is a ...
2
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1answer
43 views

Resolve assuming $x$ is real when $x$ is a free variable in a ForAll expression

I am using Mathematica to check whether a function is positive semidefinite. I have come upon an odd situation. Namely, when I input ...
2
votes
1answer
59 views

Constrained Sum evaluation [duplicate]

I need to sum up F[x1,x2,...] over x1,x2,... where I have a constraint: x1+x2+...=n (n=positive integer number). For example, I have F[x1,x2] and x1+x2=3, so for the sum I get F[3,0] + F[2,1] + F[1,2] ...
3
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1answer
34 views

Restrict list to reals for statistics

I get conjugates in output when running this: Clear[X]; X:={x1,x2,x3}; Assuming[{Element[X, Reals]},StandardDeviation[X]] What is wrong with the code?
3
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1answer
43 views

Why doesn't a real variable's conjugate evaluate to itself?

I have this code (it's just a snippet to exemplify my issue): Assuming[Element[a, Reals],Conjugate[a]] Which results in the output: ...
3
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1answer
27 views

Simplify With Assumptions Not Using Distributive Property Of Dot Product

Given the following expression Assuming[(n | d | t) ∈ Vectors[3, Reals] && n.t == 0, FullSimplify[(n + d).t]] Why does mathematica give me the below ...
2
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3answers
98 views

Adding more specific assumptions to Integrate

Let's say I would like to find a symbolic form for the integral $$\int_0^{2\pi}\sin^nx\,\mathrm{d}x$$with the added condition that $n$ is not only an integer, but an even one at that. Can this be ...
9
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2answers
145 views

Problem with Identifying Complex Components

I am trying to isolate out the real and complex terms in a fairly large expression. During the process, I have made several assumptions that last throughout the entire process. ...
0
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1answer
42 views

Assumption that a parameter is real [duplicate]

I'm making some calculations, where I use the command Conjugate[f[x]]. In the function f[x] appears a parameter J, which is Real. How can say mathematica that it should not take the Conjugate of J? ...
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1answer
150 views

Dealing with indicator functions

I am calculating the integral of two indicator functions with Mathematica. I'm having difficulty in imposing assumptions. What I have done so far: To define an indicator function: ...
3
votes
1answer
85 views

How to make Maximize function successfully maximize in general?

Having looked at Maximize Documentation SO: Mathematica: Commands return no output, but itself. Bug? Problem with Maximize Why won't Mathematica Solve a set of two equations for one variable? ...
4
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0answers
114 views

Puzzled by Assumptions [duplicate]

I don't know if this has already been discussed. Integrate[BesselJ[2 m + 1, x], {x, 0, ∞}, Assumptions -> m ϵ Integers] ...
8
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1answer
81 views

evaluation of the sum of KroneckerDelta

I need help. I need to know why the next code doesn't simplify in Mathematica 10 but it does in Mathematica 8. I need some similar in version 10. What can I do? ...
5
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0answers
50 views

External and internal Assumptions on `PiecewiseExpand` and `Mod`

After this question I'm intrigued about the different behaviors depending where and how the assumptions are given. ...
2
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2answers
69 views

Integration result with incomplete beta function

I'm doing some calculations (double integration) which results in the incomplete beta function occurring as an end result. My input is: ...
1
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0answers
80 views

Assumptions don't work as expected in FourierTransform

The 2D rectangular function and its Fourier Transform is $$ g_{in}(x,\,y) = rect(\frac{x}{x0}) \, rect(\frac{y}{y0}) \quad \xrightarrow{\mathscr{F}} \quad G_{in}(u,v) = x0 \, y0 \, sinc(\pi u x0) \, ...
7
votes
1answer
90 views

Is it possible to add some pattern to $Assumptions

I apologize if it is a too elementary question but I could not find the appropriate documentation so far. My goal is simple. I would like to add some assumptions that are defined in terms of ...
0
votes
1answer
79 views

How to simplify an expression with assumptions

I have a matrix of the form: Tvol // TraditionalForm $$\left( \begin{array}{ccc} 1 & \frac{\delta I_1(\kappa )}{I_0(\kappa )} & 0 \\ ...
4
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0answers
97 views

Multiple Constrained Sum

I need to perform a multiple summation, that obeys some conditions. This arises in the study of a statistical physics model. q=Exp[-β]. I would like to ask if ...
1
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1answer
95 views

How to assert that a list of variables is real in a nice and clean way

You can use the function Element to say e.g. $x,y,z\in\mathbb{R}$ via Element[x | y | z, Reals]. Now if I have a list of ...
2
votes
1answer
64 views

Mathematica does not distribute conjugation when used with Assuming sometimes?

If I input: Assuming[$x_{-} \in$ Reals, FullSimplify[Conjugate[$e^{i x_1}x_2$]]] Then the output is: $e^{-ix_1}x_2$ As it should be. And if instead I do: Assuming[$x_{-} \in$ Reals, ...
0
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1answer
71 views

How to disqualify a rule [closed]

Executing this line Assuming[x < 0, x -> 10] Expected output: False Say x -> 10 is a root of a polynomial ...
1
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3answers
117 views

Identify a scalar, a list

I have a symbolic scalar m2 and a symbolic list (representing a 3x3 matrix) A. I want a function which does something like: ...
0
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0answers
37 views

Need help with solving inequality under assumptions [duplicate]

I seriously need help for my research. I need to solve an inequality with several assumptions. I tried many times with Reduce but it did not work out properly. Sometimes the results I get are simply ...
3
votes
1answer
116 views

How to tell Mathematica that my variable is a scalar

In my calculations I have these combinations PauliMatrix[1].f PauliMatrix[2] where f is a scalar function. The result is as ...
2
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1answer
177 views

How to properly interpret a seemingly contradictory result in Mathematica?

I have a problem with interpreting the results of my notebook outputs. It is important that I do not err with the interpretation. Here is the full input: ...
-1
votes
1answer
73 views

Find a minimum value which satisfies an equation

I have to find a minimum value of "a" which makes x=-a+b+c, y=-a+b+c^2 positive where a>1, 0 ...
0
votes
1answer
91 views

Integral evaluation error

I have the following integral that I wish to evaluate using Mathematica: ...
0
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1answer
80 views

Solving differential equation with Variable constans?

How do I solve the following differential equations using Mathematica under the assumptions: If Abs[r[t]]<50 ->A=0.5;B=2; AND ...
1
vote
0answers
94 views

How can I force the assumption that a symbol is a vector of n zeros

Using $Assumptions = Element[n, Integers] && Element[a, Vectors[n, Reals]] I can assume that a is a n-dimensional vector of Reals. How can I assume that ...
0
votes
1answer
64 views

Why is zero times vector of reals not zero?

Using the following global assumptions $Assumptions = Element[n, Integers] && Element[a, Vectors[n, Reals]] && b == 0 && Element[c, Reals] ...
0
votes
1answer
66 views

Using Assumptions in Expressions that Evaluate to be Elliptic Integrals

I have the following integral that I am trying to evaluate in Mathematica: $\int \sqrt{\alpha + m g l \cos(q)} dq$. If $\alpha > m g l$, then the result is a complete elliptic integral of the ...
0
votes
1answer
57 views

Why won't the Rule work? And how to apply it to a combination of variables?

I want to convert SI to Gaussian units given vectors: ...
1
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1answer
63 views

Limits with assumptions

I have an example where Mathematica is not able to compute limits in a function restricted to assume that the input parameter is Real. I don't understand why this is so. 1. Could someone explain why ...
4
votes
2answers
209 views

Assumptions with patterns

I want that Mathematica assumes every symbol like Subscript[s,i] to be evaluate as a real and positive number. I have tried ...
3
votes
2answers
61 views

Simplify with assumption of unknown function [duplicate]

I have an unknown multivariate function entry[x,y,z], which is positive. Then how to get FALSE and entry[1,2,3] in the following evaluations? ...
4
votes
1answer
142 views

Mathematica does not help in this integral

I am trying to solve this integral with assumptions: ...
4
votes
2answers
137 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 ...
1
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2answers
937 views

Defining the domain of positive real numbers

I am trying to solve an equation by assuming that all the variables are real and strictly positive. I can use the keyword Reals for the argument ...
0
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1answer
83 views

Assumptions and Conditions in Integrate Function in Mathmatica

I was trying to Integrate the gravitational potential at r = x produced by a uniform sphere positioned at the origin. I wrote the following code: ...
1
vote
1answer
56 views

Simplify CubeRoot of meter cubes

Why Mathematica doesn't simplify CubeRoot of meter cubes to meters? r = Quantity[10, "Meters"]; v = 4/3 r^3 Pi; CubeRoot[% * 3/4 / Pi] returns ...
1
vote
2answers
96 views

Abs[Sin[4a]] not equal to 2Sin[2a]Abs[Cos[2a]] for a in [0,\pi/2]

I have a long expression which is not fully simplified because Abs[Sin[4a]] is considered different from 2Sin[2a]Abs[Cos[2a]] ...
2
votes
1answer
247 views

Is there a way to simplify a symbolic expression at assignment, once-for-all?

I have a series of symbolic function calls that could be greatly simplified using some assumptions. I think I would like for these assumptions to be used in the definition of the function so that they ...
2
votes
2answers
138 views

Simplifying expressions with Abs

I have a long expression which seems really complicated due to some Abs[] terms that should be simplified. However, even with the right assumptions, the expression ...
4
votes
1answer
91 views

Problem with Simplify, Sqrt, and Set: What's going on?

I am having some trouble getting Mathematica to simplify an expression of the form Sqrt[x]*Sqrt[1/x], where x>0. The problem is that x is assigned to some complicated form by the time Mathematica ...
1
vote
3answers
123 views

IntegerQ returning False despite setting Assumptions

Why does the following not return True? Assuming[z ∈ Integers, IntegerQ[z]] False I tried this on a fresh session of ...
1
vote
1answer
80 views

How to make strong assumptions?

Or put in another way, how to make a variable behave as it belongs to a specific domain, even outside the use of simplify or other commands alike? For example: ...
1
vote
1answer
115 views

Assuming variable is plus or minus 1

I have a long calculation that I am doing, which involves a particular variable h, which in the end, is either +1 or -1. (I would like a general result that is true for both cases.) Since h only ...
1
vote
1answer
67 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 ...