Questions tagged [physics]
Questions related to the application of Mathematica to problems in physics.
944
questions
7
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Numerically solving radial Schrödinger equation with Yukawa potential
I am trying to solve the radial Schrödinger equation using NDEigensystem but I am running into some issues. There are posts about doing this (see here for example), ...
- 195
0
votes
0
answers
27
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Manual updating of function in Do loop
Previously I had asked a question about solving Maxwells equations with boundary conditions, here Machine overflow when defining boundary conditions.
I have managed to successfully run the code ...
- 21
0
votes
0
answers
39
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ReplacePart will not accept coordinates [closed]
So, curiously I get an error claiming that entries like {40,80}, {41,80}... will not work as a valid positional input. I'm making these from creating a table. So, I tried manually entering these ...
- 1
-1
votes
0
answers
27
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Specify a tensor or a function with a specific form in xCoba [closed]
Suppose, in the Schwarzschild geometry with the standard coordinates, I wanted to specify an electromagnetic tensor F with the (six) components all being functions of r: A(r), B(r), C(r), D(r), G(r), ...
0
votes
1
answer
66
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A code to calculate Einstein tensor [duplicate]
I use the following MA code to calculate Einstein’s tensor. I’m asking about the zero component of the Einstein’s tensor, is it correct?
Because I think $G_{00}$ should contains the terms in the zero ...
- 213
0
votes
0
answers
50
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Calculating and collecting the terms of the zero component of the Einstein’s tensor
I try to calculate the $G_{00}$ of the Einstein tensor
$G_{\mu\nu}= R_{\mu\nu} -\frac{1}{2} g_{\mu\nu} R$
for the metric:
$g_{00}=-a^2(\tau)\left( 1+2 \phi^{(n)}\right),$
$g_{0i} = a^2(\tau)\left( \...
- 213
4
votes
3
answers
367
views
1
vote
1
answer
76
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Value of a function over permutations of two lists
I want to do the sum (in Ising lattice gauge theory)
...
- 185
1
vote
1
answer
47
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Sum on a lattice where variables can only take two values (Ising lattice gauge theory)
I want to study the Ising Gauge Theory which has the Hamiltonian
\begin{equation}
\mathcal{H} = -J \sum_{n,\mu,\nu} \sigma_3(n,\mu)\sigma_3(n+\mu,\nu)\sigma_3(n+\mu+\nu, -\mu)\sigma_3(n+\nu, -\nu)
\...
- 185
0
votes
0
answers
62
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How to calculate Einstein tensor components for this metric?
I try to calculate the Einstein tensor compenents from the eqution:
$
G_{\alpha\beta} = \frac{\nabla_\beta (\partial_\alpha \phi)}{\phi} - \frac{1}{2\phi^2} \left[ \frac{\partial_4 \phi \partial_4 g_{\...
- 213
1
vote
1
answer
100
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Plot after applying NIntegrate
I'm trying to integrate and graph $I$ vs $b$ the following integral (eq. 24 in this paper) in wolfram mathematica
$$ I = \int_{2}^{\infty} \frac{g_i^3 \mathcal{K}_t \mathrm{~d} r}{r^2\left|\mathcal{K}...
- 95
2
votes
1
answer
138
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Numerical ground state wavefunction of Schrödinger equation with a Coulomb potential in 2D from NDEigensystem
I want to numerically solve the ground state wave function of the hydrogen atom with the Coulomb potential using the NDEigensystem. Here is the code to get the ground state wave function from the ...
- 21
1
vote
1
answer
116
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Animating a double spring spherical pendulum
I want to make an animation of a double spring spherical pendulum. The first mass is connected to the ceiling with a spring, and the second mass is attached to the first one with a spring too. The ...
0
votes
1
answer
93
views
Change of variable of a numerically solved integral
I have the following function that numerically integrates a function on the interval $\left[ 2, 100 \right]$
...
- 95
1
vote
1
answer
90
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Writing a function that sorts by low powers while ignoring higher powers of various variables
I'm writing a Mathematica code with the aim of automating operator mixing calculations in QCD (at least at one-loop order). So far, it can generate Feynman rules and all graphs, assign the rules, call ...
- 21
1
vote
0
answers
81
views
Intensity pattern [closed]
I'm trying to get the following intensity pattern from this paper
In the Newtonian case, the equations for the intensity (eq. 9 and 10 in the article), I put them in Mathematica with the change $b^2 =...
- 95
0
votes
0
answers
67
views
How do you create a program to calculate the spectrum of a pulse of arbitrary shape?
Develop a program designed to compute the spectrum of a pulse with an arbitrary shape. My current program might not suitable for solving this problem.
...
1
vote
1
answer
150
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Animation of double pendulum with a spring (3DOF)
I've got a problem with animating a double pendulum where the first mass is connected with a ceiling with a bar and the second mass is connected with the first one with a spring. Below is my code ...
1
vote
1
answer
257
views
Plot solution of an integral with parameter
In this article, they solve the following integral
$$ \mathcal{I}_{o b s}\left(\nu_0\right)=\int_{\gamma_i} \frac{(A(r))^{3 / 2}}{r^2} \sqrt{\frac{1}{A(r)}+r^2\left(\frac{d \varphi}{d r}\right)^2} d r ...
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4
votes
1
answer
316
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Animation of a spring pendulum
I would like to animate a spring pendulum. Below is my piece of code. The Lagrangian and equations are correct, in which I am sure, but the animation looks terrible and non-realistic.
Could someone ...
1
vote
2
answers
141
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Making the timestep of Euler method integration a variable
I am fairly new to Mathematica, and I've been trying to implement the Euler method of integration for a fluid velocity field. I can't work out how to make the timestep a variable of my Euler method ...
- 13
3
votes
4
answers
167
views
NDSolve over derivatives of Heaviside function
I am trying to numerically solve for the strain of a Maxwell material in response to a step stress. The governing equations are $$\dot{\sigma} + \sigma = \dot{\varepsilon}$$ and I want to find $\...
- 335
13
votes
1
answer
299
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Lens on a map. Realistic imitation of magnifying glass on images with text and other small features
UPDATE: Code from this post was used for video generation here:
Cinematically moving a lens over images: magnifying glass effect in videos
I am trying to create a magnifying glass effect for images ...
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0
votes
1
answer
88
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Speed Up Plotting of Mathieu Equations
I am trying to plot Mathieu Functions, running for an hour without a result. Here is my code:
First define the relevant physical constant:
...
0
votes
0
answers
79
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Metric pertubation in xAct
I start to learn xAct. Following this thread:
expanding-the-riemann-tensor-perturbation I noticed that xAct set a default perturbation to the metric by:
...
- 213
0
votes
0
answers
133
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Simplifying the Einstein tensor in case of a perturbed FRW metric
I use the code in this thread's answer:
(Calculating Einstein tensor components in Kaluza-Klein model)
to get the Einstein tensor components of a four-dimensional Kaluza Klein model.
But instead of ...
- 213
3
votes
1
answer
136
views
Creating a plot for a summation function
I have this potential function which I believe is representative of a grounded cube in a 3D plane. I'm not entirely sure if this is it, but here is the general solution of the function:
v(x,y,z) = G(...
0
votes
1
answer
88
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Tracking сode performance with the conservation of energy
I am working with the Momentum Principle as defined by Chabay and Sherweood in their text Matter and Interactions (pf = pi+Fnet dt). The following code has been created to automate the process of ...
- 1,165
1
vote
1
answer
138
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Calculating Einstein tensor components in Kaluza-Klein model
I try to calculate the Einstein tensor of Kaluza-Klein model from this paper. It is given by Equation (55)
$
G_{\alpha\beta} = \frac{\nabla_\beta (\partial_\alpha \phi)}{\phi} - \frac{1}{2\phi^2} \...
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0
votes
1
answer
67
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Evaluate the time average of Mathieu functions
I defined a function composed of Mathieu's periodic functions:
...
1
vote
0
answers
127
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Modelling projectile with lift and drag forces
I am trying to model a projectile motion with lift and drag forces.
I have written the code below, solved for $y$ and $x$, and tried to plot it.
However, I don't know how to implement the fact that ...
- 11
0
votes
1
answer
46
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About using series function
I am using Series function on (1/z)(-k^2)^z. Up to z^0, the function gives me 1/z + Log[-k^2]. But in the standard textbook on QFT, it turns out the expansion should give 1/z + Log[k^2/mu^2] -i*pi up ...
- 29
0
votes
0
answers
57
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How can I use Gaussian elimination for finding QNMs in this code?
I am reading the article Scalar-gravitational perturbations and quasinormal modes in the five dimensional Schwarzschild black hole. I want to reproduce the value of the quasinormal frequency with $l=2,...
- 31
2
votes
0
answers
413
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How can I solve unintegrated Boltzmann equation fast and robustly?
Consider the following integro-differential equations (the unintegrated Boltzmann equations for ultrarelativistic particles in the expanding Universe):
$$
\left(\frac{\partial}{\partial t} - H p \frac{...
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0
answers
180
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Visualizing General Relativity Using Mathematica
There is an old layman method of visualizing General Relativity in which you assume the massive body to be placed on the top of large space-time fabric and the bending describes the effects of gravity,...
- 899
1
vote
3
answers
271
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Solving Geodesics from Christoffel Symbols
I am somewhat new to using Mathematica and I am facing difficulties with a specific problem related to the geodesics of Einstein's field equation in a vacuum.
The metric I am working with is derived ...
- 11
1
vote
0
answers
25
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Finding the coefficients of a decomposition of complicated expression into products of special functions
I have the following expression which arises while studying minimal models in CFT. The 4-point amplitude of scalars is given by
$$G(z,\overline{z}) = ((1-z)(1-\overline{z}))^{\frac{m-1}{m+1}}\mathcal{...
- 185
3
votes
1
answer
160
views
Thermodynamics of the 2D Ising model
I want to study the thermodynamics of the 2D Nearest Neighbour Ising model (calculate the average energy, susceptibility, etc.). I have the Hamiltonian
$$\mathcal{H} = J\sum_{\langle i j \rangle} s_i ...
- 185
2
votes
2
answers
166
views
How to numerically solve symmetric top with fixed point motion equations with Mathematica?
I am trying to numerically solve the equations associated with the motion of a symmetric top with a fixed point. Details about this system can be found in Goldstein's Classical Mechanics book (3rd ...
- 953
1
vote
1
answer
88
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Plot wavefronts of Laguerre-Gaussian modes
I am trying to plot wavefronts of Laguerre-Gaussian modes, and want to show the changing number of twists with the change in l values. If anyone has the code or any insights. Kindly help me about it. ...
- 23
1
vote
0
answers
48
views
Stiffness problem which abruptly stops the evaluation
We have a Lagrangian and we found the EOM. We need to solve the EOM and find the Phase-space plot. However, we are facing a stiffness problem which abruptly stops the evaluation (...
- 1,554
14
votes
1
answer
1k
views
Visualizing gravity warping the fabric of spacetime
What is a stable way of creating a set of points that are attracted to a single moving point? I have tried the following:
...
- 8,172
4
votes
1
answer
335
views
What are some Mathematica packages used for general relativity?
Could you suggest any Mathematica packages that are used for General relativity calculations? Id like to write code to solve the Schwarzchild Lagrangian equation.
2
votes
1
answer
216
views
Solving Schrödinger equation for Dirac comb potential (kicked rotor)
I need to solve the Schrödinger equation for a Dirac delta potential. I could not find the correct way to write the time-dependent potential and how to solve the time-dependent equation for it.
The ...
- 1,554
1
vote
1
answer
82
views
Proving an expression from Mathematica which is clearly visible from Plots
I have the following Mathematica code:
...
- 899
1
vote
1
answer
91
views
Vector 3d Plotting with New Mathematica Version
Hi Used to use the old version of Mathematica back in 2020. Now the new version is updated and I am trying to run the old code in the new version. My vector plots are very different. I wonder what I ...
- 151
5
votes
1
answer
183
views
Numerically finding a curve that satisfies an underdetermined set of equations
I am trying to determine a phase diagram along the lines of Fig 3. or Fig 4. of this pubilcation.
The curves plotted are binodals and are determined by the conditions of equality of chemical ...
- 357
0
votes
1
answer
103
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Calculate the 1st Brillouin zone with given lattice basis vectors
Given two basis vectors in the 2-dimensional momentum space b1, b2, I want to write a function that returns the 1st Brillouin zone:
...
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2
votes
1
answer
91
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Eigenfunction condition of time-independent Schrödinger equation
I'm trying to get the eigenfunctions and eigenvalues of the following one-dimensional Schrodinger equation: $$ -\frac{1}{2}\frac{d^2}{dx^2}\psi(x)+V(x)\psi(x)=E\psi(x)\,,$$ where the external ...
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-3
votes
1
answer
109
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Pade' approximation [closed]
Do you know how to enter this equation in Mathematica? It is Pade approximation, Values of p(2,..,7) are also given.
Is it just simply writing this in Mathematica? or should I do something else?
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