# Questions tagged [computational-physics]

Questions with this tag should be about computational physics, which is the study of physical situations with the use of software (commercial or in-house). Please note that details of writing and/or debugging code is OFF-TOPIC and should be asked at either Computational Science, Code Review or Stack Overflow.

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### Why does this appear in my program when running it? [closed]

I am making a plasmon simulation program using the Meep library, when I run the code everything goes well until it stops running and kills comes out. I do not understand, why.
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### Is $φ_P$ equal to $φ_E$ with no diffusion and only convection in the discretisation scheme?

I'm now studying the transportiveness of discretisation schemes using An introduction to Computational Fluid Dynamics: The finite Volume Method; HK Versteeg & W Malalasekera; 1995. In Page 144 it ...
73 views

### Is there a fundamental limit to the precision of calculations?

For daily applications, it is accepted that there are limitations to the precision of our calculations when we want to compute quantities that are rational multiples of irrational numbers. Then ...
56 views

### Good Calculators for small numbers [closed]

I know this is probably a stupid question, but I honestly cannot find one I am looking for online. Does anyone know of any calculators that can handle multiple calculations at very small numbers (on ...
1 vote
60 views

### How to correct for collision in $N$-dimensional bounded motion of a particle? [closed]

I want to numerically simulate the motion of a particle (unit mass) in $N$-dimensional space according to the force $f(\vec{x})$ and bounded by a set of linear constraints (equalities as well as ...
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### Winding Number with periodic boundary conditions (PBC)?

Imagine we have a SC with a vortex of winding number 1 (one flux quanta) described by: $\theta(x,y)$. If we look at a BdG-Hamiltonian with periodic boundary conditions (PBC), it is easy to write down ...
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1 vote
113 views

### How do you solve any partial differential equation using equivalent circuits? How is this possible?

Here's the quote from this wiki: In 1945 Kron suggested an approach to Schrödinger's equation with networks. The same year he used equivalent circuits to solve differential equations. So I've been ...
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### Plot Nusselt number between two plates [closed]

I have a free convection system between two walls (hot, and cold). And I have the temperature distribution between them, solved numerically. Now I need to plot the Nusselt number between walls. This ...
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### Simulating Arbitrary Superpositions of Quantum Dot Wave Functions

I'm looking for a relatively easy-to-use software like this or this that allows me to calculate and visualize the shape of arbitrary position-space wave functions in a quantum dot/quantum well. I like ...
107 views

### Methods in Numerical Relativity

I have been reading the book of Masaru Shibata Numerical Relativity to grasp some ideas on the methods used. I see that at the heart of the method the system of differential equations is "...
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### Calculating entanglement negativity without constructing density matrix

There are two procedures that I know of for finding the von Neumann entanglement entropy of a bipartite system split between $A$ and $B$ - a bad way and a better way. I have in mind computationally ...
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### Sensor Array Position Calibration in Anisotropic Media

Problem. I have a sensor array consisting of $n \gg 4$ receivers at unknown locations $\langle x_n, y_n, z_n\rangle$ embedded in an anisotropic medium whose index of refraction varies as a known ...
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### Does the resolution of a timeseries affect the estimate of the power-spectrum?

I have been trying to estimate the power spectrum of a timeseries using fourier transform. I noticed that by downsampling my timeseries I get a different spectrum as shown below Here you can see ...
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### How to numerically simulate random quantum circuit?

Recent years, measurement induced phase transition has been widely studied with random quantum circuit model https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.031016 . I know little about ...
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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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### Question about the MATLAB gravity models

There is a graph showing the gravity values as a function of latitudes for point mass, zonal harmonic, and wgs84 gravity models at Comparing Zonal Harmonic Gravity Model to Other Gravity Models. The ...
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### Why is my simple RK4 failing to capture adequate spring deformation?

I am setting up a very simple physical model for two colliding particles modeled as elastic spring's obeying Hooke's law. I have set up a numerical model for the collision and while the end stages of ...
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### The use of Principal Component Analysis (PCA) in Spectroscopy [closed]

Greetings there fellow users. I am to prepare and give a seminar on Principal Component Analysis (PCA) in the subject of Laser Spectroscopy (aka solid state spectroscopy). Now i am quite comfortable ...
1 vote
103 views

### 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 ...
48 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 vote
50 views

### 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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1 vote
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### How to apply a Stokes-law type drag correlation to simulate particle transport?

I am implementing a model to simulate the (two-way coupled) transport of particles in a fluid. The flow field is being solved by a numerical solver for the Navier-Stokes equations (in this case using ...
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### Reshaping $U$ and $V^\dagger$ matrices resulting from an SVD into rank-3 tensors
Let's say, that we have a $6 \times 6$ matrix $M$. By conducting an SVD of $M$ we obtain $USV^\dagger$ matrices, where $U$ is of size $6 \times 6$ and is left-normalized, $S$ is diagonal with 6 ...