# 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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### Kirchhoff Diffraction for backwards wave propagation

Classic Kirchhoff Diffraction integral for a monochromatic wave is formulated with a restriction that it's only applicable to a point that's outside of the volume enclosed by the integration surface ...
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### Problems with Sun-Earth-Moon simulations in vPython

I'm trying to simulate the Sun-Earth-Moon system using the Verlet algorithm with vpython. I'm using natural units and a cartesian coordinate system, and am having trouble working out the physics. I ...
1answer
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### Determining Characteristics of Spatial Light Modulator (SLM)

im quite lost somehow. I know this is a really basic thing and I know I should be able to do it, but something is going on with me and I tend to have problems with everything these days. Anyway: I ...
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### How to calculate a volume integral from a data file containing $x$, $y$ and $z$ coordinates and electric field value at each $(x,y,z)$? [migrated]

I have a data file from a simulation that contains $E$-field values at different coordinates $(x,y,z)$. I want to calculate the integral $\int E^{2} dV$ over a cylindrical volume in Python or MATLAB. ...
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### Why does this Non-Standard FDTD implementation lead to infinite increase in the magnitude of an EM pulse?

I have been working on a Particle-In-Cell Framework in Python and have noticed an issue where the magnitude of a Gaussian Wave Packet increasing infinitely as the simulation updates. Currently, I am ...
1answer
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### Resampling step of population annealing

I am trying to have a better understanding of the population annealing algorithm. In the section POPULATION ANNEALING, the steps of the algorithms are described. In Step 2 (Resampling (Split/Remove) ...
0answers
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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 ...
1answer
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### Programming Languages for Theoretical and Mathematical Physics [closed]

I am a physics major and will be specializing in both physics and mathematics. I mainly have interests in Mathematical Aspects of Quantum Field Theory, Topological Phenomena in Condensed Matter ...
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### What do we exactly mean when we say that a problem has an analytical solution?

What do we actually mean when we say that a certain problem has or does not have an analytical solution? I ask this because some systems that are said to have an analytical solution actually are no ...
1answer
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1answer
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### Gauss law for positive charge densities

I am trying to write a PIC (Particle In Cell) code to simulate plasma physics. I am starting with the simplest case, which is a 1D system with a longitudinal field $E = E(x)$. I am using this article ...
1answer
532 views

### Why use Crank-Nicolson over Matrix Exponential when solving Schrödinger's equation?

For Schrödinger's equation, $$\psi(x,t+\Delta t)=e^{-i H\Delta t}\psi(x,t)\approx\frac{1-\frac{1}{2}i H\Delta t}{1+\frac{1}{2}i H\Delta t}\psi(x,t).$$ The right-most expression is the Crank-Nicolson ...
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### Can anyone expound this Projectile Motion computation please?

I have this formula for projectile motion that I'm using in Unity game engine for getting the low or high Velocity of a projectile depending on how close or distant the target is (as long as it is ...