# Tagged Questions

Questions related to the application of Mathematica to problems in physics.

41 views

### How to combine two matrices.? [duplicate]

let A, B are any 4 by 2 Matrices , i want to know whether it is possible to obtain a 4 by 4 matrix by using equation A=B Thanks in advance
43 views

### Polarization sum in FeynCalc

I think I know how to sum over final state fermion spins (FermionSpinSum[...]?) but what is the analog expression (in FeynCalc) if you have two or more polarization ...
68 views

### Calculating the normalization constant for a wavefunction

How can I compute the normalization constant for a quantum mechanics wave-function, like $\Psi(x) = N \exp(-\lambda x^2/2)$ by using Mathematica? (The normalization constant is $N$).
33 views

### How to combine similar terms in a density matrix expression? [Ref: Quantum Computing]

I tried the following : Simplify, FullSimplify, and Expand. Due to this problem, I am not ...
84 views

### Divergence of $1/r^2$: Mathematica yields 0, while the correct answer is a DiracDelta

In spherical coordinates, the divergence of a point charge is $4 \pi \delta (r)$, the three-dimensional Dirac delta function. In ...
170 views

### Help with NonLinearModelFit

I have a question about fitting data with a model. I have a quite complicated model, based on Arctans, modified Bessel functions, etc, that I want to fit to my data, a table of couples (minimal ...
161 views

### Attempting to use NDSolve to plot harmonic oscillator solutions

NDSolve[{ (-y''[r]/1880) + (470 (0.04077)^2 r^2 - 48 + 1/(1880 r^2)) y[r] == 0, y[0] = 0, y'[0] = 0}, y, {r, -4, 4}] I use this but get errors and am ...
80 views

### Singularity while solving PDE

I have to solve a PDE (in the context of the functional renormalization group in physics). I have a function of two variables, $U(l,p)$. I know $U(0,p)=U_0(p)$ and then I have an equation (eq925) that ...
113 views

### A 1D numerical integral Mathematica cannot compute, from physics

A well know result in theoretical physics is that a sum over Matsubara fermionic frequencies, i.e.: $$S = \sum_{n=-\infty}^{\infty} h(\omega_n) \hspace{32pt} \omega_n=(2n+1)\frac{\pi}{\beta}$$ can ...
42 views

### Plotting a parameterized vector in the x-y plane

I am trying to plot the trajectory of a parachutist descending at a constant vertical rate of 8 m/s while a south wind also blows at a rate of 8 m/s. He initially jumps from a height of 300 m. I am ...
364 views

### Plotting 2-D Electron Density Carbon Atoms

I need to create a 2-D electron energy density plot in Mathematica to compare with my STM experimental results in my lab class. This would be done by plotting the sum of the symmetric and ...
188 views

### Boson commutation relations

I have tried to adapt this answer to my problem of calculating some bosonic commutation relations, but there are still some issues. The way I'm implementing the commutator is straightforward: ...
99 views

### How to reduce an expression into user-defined variables?

In the following code, I define a set of matrices. Then, I define a function that calculates the commutation relation relation between these matrices ...
291 views

### Time evolution/dynamics of circular plate with hole (Biharmonic equation and stiffness)

On this Mathematica.SE form, there exists information on how to use Mathematica to demonstrate the vibration of a circular membrane and the deflection of an orifice plate (the latter I had raised ...
389 views

### Time evolution of a bispinor [duplicate]

The effective Hamiltonian for polariton graphene is given by: ...
142 views

### Interfacing Red Pitaya board with Mathematica [closed]

I just discovered the Red Pitaya board and borrowed a unit to play during this weekend. Surprisingly I did not find any reference to Mathematica on the Red Pitaya forum, nor did I find any reference ...
127 views

### Help nedeed for understanding NDSolve architecture -Vacuum Heating Simulation

I am a beginner in mathematica and I am facing a problem that is way bigger than my knowledge.. I am tryng to simulate a semplificated version of Brunel Effect, wich is a Laser-Plasma interaction ...
117 views

### Equal flow boundary conditions

I'm having the following issue that can not find a solution , by using this boundary condition v[0, t] == u[1, t] that Mathematica does not understand, someone ...
62 views

### Slater Koster parameters generated using Mathematica

Here is a link where people describe how one can generate the entries of the Slater Koster parameter table seen here as Table of interatomic matrix elements. The ...
275 views

### FEM Solution desired for “Plate with orifice” deflection: Application of Boundary Conditions and use of Regions

I found the deflection of an orifice plate (circular plate with a hole) subject to uniform pressure using Mathematica's NDSolve functionality. The plate is fixed at its outer circumference and is ...
191 views

### Potential flow over cylinder with FEM: Pressure field is flipped

Much in the fashion of a few problems already answered on Mathematica.SE (1, 2), I am trying to solve the Laplace equation in velocity potential $\phi$ to simulate irrotational, inviscid flow over a ...
89 views

### How to obtain the magnetic field of the following set up [closed]

This is the experimental set up: A ferromagnetic cylindrical disk (of irrelevant dimensions) has either sides set at different electric potentials (left side at 0 volts and right side at 1 volt). A ...
118 views

### Alternatives to Mathematica that are not computer algebra systems [closed]

Are there alternatives to Mathematica that are not computer algebra systems? I know there have been questions on this, but I am focusing on oprn source projects and instead of focusing on computer ...
76 views

### Solving 4 coupled differential equation for modelling boson star

I'm trying to study about modelling star from a journal. To get the characteristics of the star, I have to solve 4 differential equations which are coupled each other. I want to use Mathematica 9 to ...
77 views

### Find all degenerate eigenvalues of a cubic equation

I have an equation that is cubic in w. The three solutions correspond to bands in a bandstructure, and are a function of wavevector ...
153 views

I am trying to simulate a bar/link element under axial tensile load. The link is of unit thickness and I may use a plane stress model. A plane stress model is an approximation that may be used for ...
207 views

### Finding the conditions for degenerate solutions to a cubic equation

I have a cubic equation (corresponding to the band structure of a physical system) given by w in the code below. ...
83 views

### Eigenvalues function not producing expected results?

I'm running into a strange issue when trying to compute eigenvalues of a 2x2 matrix for graphene. If I "manually diagonalise" by multiplying the two off-diagonal terms together and taking the square ...
92 views

### FullSimplify not giving me a physically useful answer for Mott scattering

I am using Mathematica to find the cross-section for Mott scattering over an extended target. I evaluated ...
179 views

### Modeling a stellar atmosphere

I'm trying to model a stellar atmosphere using Mathematica. Basically I'm working in a physical and chemical model which combined should give me a profile of the chemical abundance in the atmosphere. ...
767 views

### How to plot an emission spectrum?

If I have a list of data with various wavelengths in nanometers, how would I plot them on a graph so it looks like this: So far I have managed to plot a spectrum in ...
120 views

### Van der Waals Isotherms [closed]

I have the following code: ...
209 views

### Solving coupled first-order autonomous differential equations

I am trying to run a simulation of a circuit to observe chaotic behavior, and have obtained a set of differential equations from an analysis of the circuit. I thought perhaps I could produce a plot ...
50 views

### how to make one plot for each line of a table of 127 datas (127 plots) , or one plot with 127 curves onto it?

Good evening, I encounter a difficult problem. I have 127 lines of data, with for each line, 9 columns. I imported from a txt file : ...
274 views

### Mimic a procedural, recursive clustering algorithm for site percolation using functional programming

Sorry in advance for my logorrhea: I just want to make sure all of the information is here. Context and Question I am investigating site percolation on a square lattice. I have a working, ...
108 views

### Animating a parametric plot

I am attempting to animate my parametric plot, but am having difficulties. I tried simply wrapping the plot code with an Animate[expression,{t,0,5}], but that ...
536 views

### Defining quantum-mechanical Bra and Ket operations

I have the following ket in the Fock basis: $\vert3, 0 ,1\rangle$, where each entry defines the number of photons in a particular mode and can take any one of the following numbers: 0, 1, 2, 3. As a ...
143 views

I'm trying to reproduce the following plots: As described by this blog entry: Synchrotron radiation As you can see in the linked article, the task is essentially to make a ...
117 views

### How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
83 views

### Diff eqs can be solved?

I'm trying to solve a pair of coupled differential equations, but am having trouble making DSolve evaluate my equations. ...
105 views

### Plot ParametricNDSolve

I am trying to plot the probability of a molecule being in a certain state via the numerical solution of the SchrÃ¶dinger's equation of molecule in an oscillating electric field (in a rotating system). ...
118 views

### Fundamental question about capabilities of Mathematica to represent abstract mathematics [closed]

I have an fundamental question about what Mathematica can and cannot do. I have a book which presents a certain physical theory in an axiomatic manner. The axioms make heavy use of mathematics. Some ...
32 views

### How to solve coupled first-order ODE with vectors?

m * v'[t] = q * (E + v x B) using the following: B = (0,0,B0), E=(Eperp,0,Ez). How would I find the general solution of ...
53 views

### Tracking solutions over a Brillouin zone

Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
76 views

### Difficulty solving an equation involving a couple of different powers

I have this semi-complicated equation to which I want to find an analytical solution for $\epsilon$. The equation is a s following: a^2 (2 b k \epsilon \sqrt{1 - \epsilon^2/b^2} - 2 c k ...
397 views

### Integrating a function over a surface integral

From a first principles bandstructure calculation I get an energy scalar field in three dimensions $E(x,y,z)$. It's now easy to plot a constant energy (contour)-surface for dedicated values ...
57 views

### How to implement time dependence in the DoFun package?

DoFun is a very usefull mathematica package that helps to write Dyson-Schwinger and FRG flow equations when these are to complex to write down by hand. You can download it here and read it's manual ...
126 views

### Eigen energies of 2D time independent Schrödinger equation

Firstly, I am aware that a similar question of this type was asked, but it was not helpful as it was only one dimensional (so please don't mark my question as a duplicate) The trouble I am having is ...