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Nesting blochspheres in tikzpictures using the blochsphere package [migrated]

I am using the blochsphere package (see 1) and I want to nest it in another tikzpicture, to work with several blochspheres. The manual tells one to put "nested=true" in the settings for <...
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1 answer
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Stopping too soon [closed]

I have an object going $1000\frac ms$, $vi$, that I want to slow down to $250 \frac ms$, $vf$. I want it to slow down in $10000m$, $d$. I want to know how much deceleration is necessary, and how long ...
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1 answer
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Problem in code for Monte Carlo method for frustrated Ising model

I'm studying Monte Carlo method (it's related to my school project). The code I'm using I got from a paper by Jacques Kotze (https://arxiv.org/abs/0803.0217). In his paper, he uses the Monte Carlo ...
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Why Hartree-Fock (HF) calculation in periodic system so weird? [closed]

I am doing some Hartree Fock calculation for periodic system using PySCF python package, but it gives me strange results. ...
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1 answer
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Astropy Package - Defining new dark energy parametrization

I was looking through astropy, and I wonder is it possible to define a new dark energy parametrization instead of using the pre-defined ones..? I couldn't see the reference but maybe I missed it. ...
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How to plot off-equatorial orbits in Kerr metric?

I am trying to plot the time-like trajectories in Kerr metric. I have taken the equations from here. I am trying to reproduce the off-equatorial trajectories from Chandrasekhar's textbook, e.g., the ...
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How to normalize cartesian gaussian type basis sets?

I am currently working on my graduation paper each high school student in Switzerland has to write. I chose quantum mechanics. To be more specific Hartree-Fock-Theory. I understand all the theory ...
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Getting top-of-atmosphere (TOA) irradiance from Bird solar model

I'm just getting acquainted with the Bird solar irradiance model after finding via pvlib-python. From skimming the references, it looks like the Bird model does generate spectral atmospheric ...
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1 vote
1 answer
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Problem solving (numerically) the Tolman-Oppenheimer-Volkov (TOV) equations for any equation of state [closed]

I've been working on a code to solve the TOV equations for a while and recently I've got it right but only for one specific equation of state, the bag model, wich is not what I need since it should ...
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1 answer
32 views

Equivariance and Wigner $D$ matrices for Spherical harmonic rotations

I am trying to understand equivariance in machine learning, specially as discussed in the following paper. Claim is that equivariance is when Group symmetry operation, such as rotation, commutes with ...
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1 answer
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How to set mask size when apply inverse-FFT to the power spectrum of HAADF-STEM image?

Hello everyone, I want to characterize dislocation in my FIB sample using Titan electron transmission microscopy and I want to use FFT filter to process my HAADF-STEM image with DigitalMicrograph (...
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How to Model Chirp in Laser Pulse

I'm trying to model a chirped pulse with Python using the following form: $$ E(z,t) = cos \left( \omega_0 \cdot (t-z/c) + \beta (t-z/c)^2 \right) \cdot exp \left[ - \alpha t^2 \right] $$ From ...
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Modeling ferromagnetic materials in a primitive python FEA

I am working on a primitive 2D DIY magnetic "FEA" solver for a class project. It's really just a big NumPy array where each element in the array can be one of the following: Air Current ...
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1 answer
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Writing a potential energy matrix in two dimensions with python

I am using the finite difference method to solve the time-independent Schrödinger equation. To use the method we need to make everything discrete so the potential $V(x)$ becomes a $N\times N$ matrix $\...
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How to calculate the orbital character for fatbands in Quantum Espresso?

we are calculating a fatbands structure using QE pw.x. When We get the projections by weight. There are orbitals missing in the projection file. Is there a way to get contribution about outermost ...
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7 votes
3 answers
443 views

Simulator for trajectories of charged particles in electric fields?

I am looking for a numerical simulation program which computes the trajectory of a charged particle moving in an electric field. The electric field should be numerically determined by determining a ...
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1 answer
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Orbital animation

I'm no longer able to follow the differentials and derivation of orbital mechanics. Given a heavy star like mass W located at (x1, y1, z1) and a small mass at (x2, y2, z2) with a motion/velocity of (...
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1 answer
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Program to generate graph of spring-mass-damper system

For a school project, I've been researching mass-spring-damper systems. For this I did an experiment in which I basically filmed a spring with a mass attached to it that went up and down and ...
3 votes
1 answer
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Numerical package for backreaction in general relativity

I am looking for numerical packages (Python/Matlab or some common languages) that can simulate the backreaction of the matter on the Kerr black hole geometry: i.e. assume I have a given initial ...
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1 answer
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Software recommendation for a tensor calculation

What is the best software/package to calculate $$2R_{\alpha\mu\beta\nu}R^{\mu\nu}-\nabla_\alpha\nabla_\beta R + \Box R_{\alpha\beta}-\frac12g_{\alpha\beta}\Big(R_{\mu\nu}R^{\mu\nu}-\Box R\Big)$$ for a ...
1 vote
1 answer
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Using finite difference to solve Cahn-Hilliard Equation in 2D using Octave

I am trying to use the finite difference method to solve the Cahn-Hilliard equation in 2D to study phase separation in metallic glasses. The equation is given as follows. $$\frac{\partial c}{\partial ...
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Overlap of Matrix Product States (Python)

I'd like to implement the TEBD (finite, real time evolution) by hand (in python) and want to compute the overlap of a reference MPS with the time evolved MPS. I want to regard a simple Ising Chain. ...
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1 answer
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Boundary conditions and normalization of wavefunction in time-dependent Schrodinger equation

I came across this confusion when trying to numerically solve the time-dependent Schrodinger equation. The short version of my question is: when solving for time-dependent wavefunctions $\psi(t,x)$ on ...
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1 vote
0 answers
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Numerical solution of Bethe ansatz equation

In this paper https://arxiv.org/abs/2003.14202, the authors plot the solution of coupled non-linear algebraic equation (Bethe Ansatz Equations): \begin{equation} k_j L=2\pi I_j -\sum_{\beta=1}^M \...
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How to visualize Kinematics or Classical Physics?

Is there a software or a website to visualize Kinematics? For example, I want to visualize different problems on pulley system. Is there a simulation app?
2 votes
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Self-Consistent gap equation: numerical solution

I'm trying to calculate the simple self-consistent gap equation in Python. $$\Delta = \lambda \int_{-Ec}^{Ec} \Delta \frac{\tanh\left(\frac {\sqrt{\xi^2 + |\Delta|^2}}{2K_{b}T}\right)}{2\sqrt{\xi^2 + ...
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0 votes
2 answers
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Graphing the motion of a driven damped pendulum

$ \ddot{\phi}+2 \beta \dot{\phi}+\omega_{0}^{2} \sin \phi=\gamma \omega_{0}^{2} \cos \omega t$ The equation of movement is written above. I´m trying to plot the value of $\phi$ for different values of ...
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How do I visualize a stepwise rotation on the Bloch Sphere using $SO(3)$ and $SU(2)$?

Searching for an implementation (that helps me to understand how $SO(3)$ and $SU(2)$ relate to each other) I came across this interesting question Visual interpretation, on the Bloch sphere, when ...
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Uncertainty of frequency from tone generator app on phone

If I were to download a tone generation app (sonic) on my phone (Iphone 13) and use it to generate a sine-wave of a certain frequency, what would the uncertainty of the frequency be? How can it be ...
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1 vote
1 answer
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Determine position, velocity, and acceleration from video tracking software

I'm working with some video tracking software, and I'm interested in determining the position, velocity, and acceleration as a function of time of the object of a video. For simplicity, let the motion ...
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1 vote
1 answer
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Numerical solutions to 1D Schrodinger equation suggest degenerate energy eigenvalues, though this is supposedly disallowed

I am working on solving the time-independent Schrodinger equation using the method of finite differences. This approach has been discussed previously on this site (here, for instance). My code is ...
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Comparing the variance of the position of particles of a sample of matter with the sample's temperature

As the title suggests i have attempted comparing the variance of the position of particles of a sample of matter with the sample's temperature. Now firstly we need to clarify the basics: method for ...
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Lie Symmetry method for solving perfect fluid SEM Tensor Einstein Equations

Suppose that we have the field equations $$G_{\mu\nu}=\kappa T_{\mu\nu},$$ with $\kappa=\frac{8 \pi G}{c^4}$ and $G_{\mu\nu}=R_{\mu\nu}-\frac12Rg_{\mu\nu}$. We assume that our matter distribution ...
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-1 votes
2 answers
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Solution techniques to the Einstein Field Equations

Consider the EFEs $$R_{\mu\nu}-\frac12Rg_{\mu\nu}=\kappa T_{\mu\nu} \implies G_{\mu\nu}=\kappa T_{\mu\nu}.$$ The Einstein Field Equations are a set of highly couples non-linear hyperbolic PDEs, which ...
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How to compute a function of two tensors?

I am working with the de Sitter metric which takes the form $$g=\tau^{-2}\left(-\left(\Lambda / 3-\tau^{2}\right)^{-1} d \tau^{2}+\left(\Lambda / 3-\tau^{2}\right) d t^{2}+g_{\mathbb{S}^{2}}\right)$$ ...
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Automated symbolic commutator tool

Is there a software tool (perhaps Mathematica extension?) designed to help with doing algebraic manipulations of non-commutative objects? Specifically, what I'm after is an interface along the lines ...
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Except for COMSOL Multiphysics, what is the dedicated simulation tool (free version) that can simulate arrayed acoustics?

Using units and horns, we now have individual replicas. I'm trying to calculate the sound pressure level by arranging hundreds of these in a simulation 1m in front, but when I do it with COMSOL ...
4 votes
1 answer
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Drawing night sky of planets other than Earth (invariable plane ambiguity)

I'm writing an application that draws maps of night sky that can be visible from other planets (ultimately they are to be exoplanets). Mostly I do it out of curiosity :). I's thinking a lot where I ...
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Displacement distribution Molecular Dynamics

I have a file "traj.dat" with the trajectory of $N$ particles for $M$ frames separated by $\Delta M$ steps (with a time-step $\Delta t$). I often compute Mean Square Displacement (MSD) of ...
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What is the reason that in DPD (LAMMPS) we can define a protein (or any material with a flexible geometry) without the material loosing its shape?

I am new to LAMMPS/DPD (Dissipative particle dynamics), but as I read through DPD model which is a coarse graining model, there are only three main forces between beads (beads are the spheres ...
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LAMMPS: How to enter a simple potential for Dissipative Particle Dynamics (DPD)?

I apologize if this is off-topic and if so would be grateful for someone to point me to a relevant source of information. Dissipative Particle Dynamics (DPD) is a quick simulation technique that ...
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24 views

Is it possible to create a model with multiple axes using 2D modeling in COMSOL Multiphysics?

I am trying to simulate the sound field strength created by a loudspeaker array with COMSOL. The simulation of individual loudspeakers (oscillator + trumpet) was effectively calculated using the 2D ...
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Calculating Lyapunov exponent (LE) for pendulum using ellipsoid growth - code yields negative LEs

Per my advisor, I have read the textbook Chaos, an introduction to dynamical systems by Alligood, Sauer, and Yorke. (side not, I have really enjoyed this book). In chapter 5, the numerical calculation ...
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Are the Euler-Lagrange equations used in modern physics engines for computer graphics?

We learn in graduate school about how Newton's equations can be generalized to form the Euler-Lagrange Equations. I've been told that the Euler-Lagrange equations are more practical to work with for ...
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99 views

Dirac Delta function in Brillouin zone - Python Coding Problem

I am confused with the expression of Dirac delta function in the 1st Brillouin zone in python. Suppose we are dealing with a 1D chain with period boundary condition which have 10 sites for instance. ...
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1 answer
175 views

How do I convert a .FITS into a numpy array (or a file that can be used in Python)? [closed]

I'm trying to train an AI algorithm to determine photometric redshifts of galaxies, and to do so I have a .FITS file which contains the training data. I need to convert this .FITS file into a format ...
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Obtaining XYZ from spectrometer CCT?

This is kind of a practical question - but I cannot make ends meet because I lack theoretical background, so I hope it's OK to post here: I hope that I'll get enough theoretical pointers, so I can ...
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1 vote
0 answers
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How to measure physical luminance just with regular camera? [closed]

Maybe there is some software for that task? Theoretically, it's able to realize. I guess it's may work somehow like bracketing in photography (making HDR shots from several shots with different ...
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0 votes
1 answer
47 views

What are eigenfrequencies of guided electromagnetic waves?

I am using a commercial software (COMSOL) to find modes in dielectric waveguides. Each mode is associated with an eigenfrequency. In this context, what is an eigenfrequency?
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2 votes
2 answers
162 views

Solve the stationary Schrödinger equation with the finite difference method [closed]

I am trying to solve the stationary Schrödinger equation for a double-level well potential through the finite difference method. Here is the shape of the potential I would like to solve it for where ...
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