# 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.

541 questions with no upvoted or accepted answers
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### Interpretation of Stiffness Matrix and Mass Matrix in Finite Element Method

I would like to have a general interpretation of the coefficients of the stiffness matrix that appears in FEM. For instance if we are solving a linear elasticity problem and we modelize the relation ...
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### An explanation for the Landauer's principle

Has anyone understood the Landauer's principle? What is the current status? In specific, is there a theoretical derivation of the Landauer's Principle?(not the heuristic one based on Salizard's ...
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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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### Numerically calculating the berry curvature for graphene

i'm trying to reproduce this density plot for the Berry curvature in the Brillouin zone of graphene from this website. In order to do this I am attempting to use this equation for the berry curvature ...
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### Do these Lagrange equations of 1st kind exhibit numerical instabilities?

I followed the lead of "Theoretische Physik", 1e, 2015 by Bartelmann et al. (pp. 171 - 174) to form the set of constituting Lagrange equations of the 1st kind for the double pendulum: eight ...
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### Quartz crystal resonance frequency simulation

Is there an open source/scientific software package that would allow to simulate Quartz crystal resonance frequency for specific cut angle, crystal geometry and temperature? How would one approach ...
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### Large-scale rotational invariance in lattice space

It is often claimed among physicists that rotational invariance can emerge at large scales in lattice space. Let's focus on quantum mechanics for now. I interpret this claim as follows (I am a ...
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### No sign problem in quantum Monte carlo simulations of 1D systems?

I've heard many times people saying that there is no sign problem in the quantum Monte Carlo simulations of 1D locally interacting quantum systems. I think this means, for any 1D locally-interacting ...
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### Light by light cross section using equivalent photon approximation (EPA)

I'm trying to understand how to do a numerical calculation of the light by light cross section utilizing the Equivalent photon approximation (EPA). I'm considering two incoming electron beams of ...
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### What is the maximum amount of computation that can be performed in the future lifespan of the universe?

The ultimate question I have been trying to answer is the maximum universal population allowed by physical limits. Making some transhumanist assumptions I am perfectly happy with, I am equating this ...
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### What is the correct way to perform numerical integration over Brillouin zone?

Let us have an integral $I$ over the first Brillouin zone (BZ) of a 2D lattice. $$I = \int\int \Omega(k_x,k_y) dk_x dk_y$$ where $\Omega(k_x,k_y)$ is some function (let's say it's Berry curvature). ...
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### Using Runge-Kutta method with measurements of acceleration (what to do with half-steps?)

I'd like to perform a short-time motion estimation based on measurements from an Inertial Measurement Unit. If I use the Runge-Kutta method, I will need to compute the k values at half-time steps (Ref)...
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### Refocusing light field images via Fourier Slice Photograph theorem

I am trying to refocus images from a microlens array light field using Ren Ng's Fourier Slice photograph theorem found in his thesis chapter 5, equation 5.7, which is available at https://stanford.edu/...
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### Can quantum computing solve the curse of dimensionality?

The curse of dimensionality is ubiquitous in machine learning (ML) modeling, stochastic control and reinforcement learning, arising in a probabilistic sense, with strong connections to quantum ...
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### Implications of thermodynamic inconsistency in CFD calculations

During my PhD work I had to use tabulated values of thermodynamic properties of gases in some Computational Fluid Dynamics (CFD in short) simulations. CFD simulations consist in the numerical solution ...
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### Magnetic susceptibility

Currently I'm doing the simulation of Ising Model with Monte Carlo method. I got a curve which the magnetic susceptibility diverge (precisely due to finite size effect, it is not diverge but show the ...
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### Combined effects of strain and doping on the electronic structure of semiconductors

I've read papers in DFT studies on band gap tuning in semiconductors and the usually studied methods are either through doping or application of external strain. But its always just one or the other. ...
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### Simulation of plasma in tokamak

I am reading some papers on numerical algorithms for simulation of plasma in the context of nuclear fusion in a tokamak. I am getting a little lost as there is a huge number of references, and it is ...
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### The definition of fidelity for fermion

The definition of fidelity for two mixed ensembles is $F=Tr\sqrt{\sqrt{\rho_1}\rho_2\sqrt{\rho_1}}$. Now I came across a problem in numerical calculation, Systems A,B are identical, but attached to ...
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### How are boundary consitions implemented correctly in time dependent hydrodynamics?

I posted this question more than one year ago and got an answer recently. This answer looks good to me, but indicates that something is wrong in my original approach to the problem. Can someone tell ...
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### Open-source code for computing response functions

Summing Feynman diagrams to compute the response functions of a microscopic model is common in many areas of physics. While conceptually straightforward, the task can be computationally intensive. ...
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### How to calculate dispersion relation from a Finite Difference (FD) wave simulation

I have a python code that calculates the solution of the inhomogeneous acoustic wave equation for a 2D medium with any velocity and source configuration. It was implemented using Finite Differences ...
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I have a question that I believe is relatively easy to answer, I am working on an $N$-body simulation of a fictional star system and am having trouble finding the velocity of moons so that they will ...