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

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22 views

Hold assumption in Simplify [on hold]

If you type this into Mathematica, PrimeQ[x] It will return False. However, ...
0
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1answer
51 views

Simplify assuming $x$ is small [closed]

I would like to assume that $x$ is small so that values of the order $x^2$ (and higher orders) are negligible. For example, I would like Mathematica to return $1-2m$ when I ask it to simplify ...
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0answers
28 views
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0answers
40 views

Impose conditions on differential equations

This is my first post in Mathematica Stack Exchange, so thanks for your help and sorry for any rookie mistakes. I am solving the Einstein equations for two vectorial pertubations h_Alpha and v_Alpha ...
1
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1answer
34 views

How to specify assumptions without typing out functions

So I want to add assumptions in carrying out integration. I know I could use the Integrate function: Integrate[V Exp[-x/a] ,{x,0,10}, Assumptions->a>0] but ...
1
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0answers
54 views

Assumptions aren't working in this sum

I have a sum that should be real: FullSimplify@Sum[1/(α n^4 + β), {n, 1, ∞}, Assumptions -> α > 0 && β > 0] But the result have involved even ...
5
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3answers
240 views

Assumptions for RotationMatrix

I'm making C++ program, and in my program I need a rotation matrix around any vector. I wanted to extract RotationMatrix[fi,{x,y,z}] output and put it in my ...
1
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0answers
60 views

Limit not evaluated [closed]

I hope this question ha not been asked since the limit is evaluated in 1 not at 0 or infinity. I do not know how to ask Mathematica to find the limit as n -> 1 of the following function: ...
0
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0answers
28 views

Finding parameters that give constrained eigenvalues of matrix

I want to obtain the eigenvalues $x_1,x_2,x_3$ of a hermitian, off-diagonal matrix, {{0, Conjugate[d], Conjugate[g]}, {d, 0, Conjugate[h]}, {g, h, 0}}, under the ...
1
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2answers
69 views

Minimization of a function with non-numeric parameters?

I have the following problem (in Mathematica) I want to calculate the following expressions: ...
7
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0answers
67 views

Need explanation on strange behavior of Simplify under given assumption

This is quite surprising to me. Simplify[a == b, {a == {1}, b == {1}}] a == b does not evaluate the equality, while ...
2
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1answer
81 views

Getting wrong result when Integrating under an assumption [duplicate]

The simple integral $$\int_0^b \cos\left(\frac{2\pi m(y-\eta)}{b}\right) \cos\left(\frac{2\pi \eta}{b}\right)\mathrm{d}\eta$$ can be easily evaluated by Mathematica as, ...
0
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1answer
110 views

Understanding the symbolic solutions of a system of differential equations

I'm trying to solve a simple system of differential equations but get outputs i just cant grasp, they seem way overkill. Someone said it might be because mathematica interprits the constants as ...
1
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1answer
70 views

The assumption in integration does not work?

I am new to mathematica. Here is the question. I try to do the following integration with the assumption that k1<0, k2<0 and k1,k2 are real number. However, the result includes \sqrt{k1}? ...
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1answer
52 views

Same integral gives different results with assumption

b = 1 k = 12560 r = 500 res = Integrate[Exp[I*k*x*Sin[o]]/(r + x*Sin[o]), {x, -b/2, b/2}] resab = Abs[res]^2 Plot[resab, {o, -Pi/20, Pi/20}, PlotRange -> Full] ...
3
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1answer
46 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?
4
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1answer
38 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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1answer
62 views
0
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1answer
88 views

How to impose Assumptions for a list of variables?

I've got an $Assumptions variable that I'd like to apply to my whole notebook, looking like so at the moment: ...
3
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1answer
56 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: ...
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
49 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
votes
1answer
48 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 ...
1
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1answer
170 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: ...
2
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1answer
66 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] ...
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3answers
133 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: ...
2
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3answers
116 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
148 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
48 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? ...
3
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1answer
134 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? ...
10
votes
1answer
333 views

Limit of sequence of functions behaving strange

I'm trying to determine the limit of the sequence of functions $$f_n(x)=\left(\frac{1}{\pi}\arctan(n x) + 1/2\right)^n. $$ I define ...
8
votes
1answer
95 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? ...
4
votes
0answers
116 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] ...
20
votes
2answers
2k views

Usage of Assuming for Integration

For some reason, when I enter the following integration in Mathematica Assuming[{k ∈ Integers}, Integrate[ Exp[ I k t], {t, -π, π}]] the result turns out to be ...
5
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0answers
52 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. ...
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0answers
91 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) \, ...
2
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2answers
79 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: ...
5
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1answer
306 views

Integrate wrong for absolute value of trig function

I was trying to get $\int_0^1 \lvert \cos(2 \pi k x) \rvert \,\mathrm{d}x$ for $k \in \mathbb{Z}$, and was surprised by the result (using Mathematica 10.0.1.0): ...
7
votes
1answer
109 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
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1answer
82 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 \\ ...
2
votes
0answers
685 views

I can't solve this set of equations

I am having trouble solving a set of equations using Mathematica 8. I do not get any errors, but I don't get any solutions either. My parameters and variables are real and non-negative. ...
4
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0answers
103 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
101 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 ...
11
votes
1answer
235 views

What exactly does GenerateConditions do?

Consider for example this strange behavior: Integrate[1/x, {x, 0, Infinity}, GenerateConditions -> False] (*0*) I'd also like to know the difference between ...
2
votes
1answer
70 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
votes
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 ...
26
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1answer
464 views

Are greek symbols causing different evaluation?

I've updated today to Mathematica 9.0.1.0 from version 8 and found something that absolutely confuses me. Let us define a piecewise function: ...
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
134 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
184 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: ...