Computational Science Stack Exchange
Computational Science Stack Exchange

Questions tagged [computational-physics]

Computational physics is the study and implementation of numerical algorithms to solve problems in physics for which a quantitative theory already exists.

461 questions
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Quality of linear congruential generators for random numbers

I'm doing some simulations of the Langevin equation, for various external forces. Being told that C's rand() from stdlib.h can introduce bias in my results, I'm using a Mersenne Twister. Nevertheless, I would like to know (and see) exactly what kind…
RedPointyJackson
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Why is it not computationally possible to accurately predict the weather that would occur after 14 days?

As per wikipedia, scientists have not been successful to accurately predict the whether which is 2 weeks ahead. Here is the excerpt: The atmosphere is a chaotic system, as a result, small changes to one part of the system can grow to have large…
Muhammad Maqsoodur Rehman
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Do there exist "frameworks" as to how computational scientific experiments claim validity? Scientific method for computed science?

Do there exist "frameworks" as to how computational scientific experiments claim validity? Like "scientific method for computed science"?
mavavilj
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Numerical scheme with energy conservation?

I have a set of equations to integrate something in time $t$. At each time step I compute a scalar field $\phi(t)$ and a potential $V(\phi)$. I should also control the conservation of energy with an equation:…
Vincent
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How to properly compute a differential cross section?

I'm currently in the process of computing a differential cross-section for the scattering of a 420 MeV electron by an O-16 nucleus (with a Wood-Saxon charge distribution). The problem is that the resulting graphs don't look anything like they…
Athkor
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Simple model of Saturn's rings

I’m trying to figure out how to model the rings of Saturn using a particle system for a gravity simulator that I’m making. Using the code below, I’ve managed to create a, if not perfect, decent ring that rotates around Saturn under the force of the…
Happy Koala
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How to avoid negative roots with a Newton's method?

I'm currently trying to solve a system of (3) nonlinear equations of (3) variables which are the baryonic density, the isospin asymmetry and and the density of a fluid with the Broyden's method (a quasi-Newton method) included in the GSL. The…
T. Auerrac
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Method for calculating the stopping distance using only integers

I am trying to find how much an engine would turn until it stops accelerating with an acceleration of $a = A \sin^2(x)$. Acceleration Integrating the acceleration I get velocity $v = A(x/2 - \sin(2x)/4) $ Integrating the velocity, I get the…
HYK
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Scattering of waves in a symmetrical potential (using python)

I'm looking at scattering of waves in a symmetrical potential as part of a research project. If a plane wave $e^{(ikr)}$ is incident on a spherically symmetric potential $V(r)$ the scattered wave is given by $S(r,\theta) = \frac{f(\theta)e^{(ikr)}}{…
user35752
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Radial Hartree and exchange-correlation potentials

According to [1] the one-dimensional Kohn-Sham equation is given by $$ \left( -\frac{1}{2} \frac{d^2}{dr^2} + \frac{l(l+1)}{2r^2} + V[\rho;r]\right) rR_{nl}(r) = \varepsilon_{nl} rR_{nl}(r) $$ where $$ V[\rho;r] = -\frac{Z}{r} +…
tohoyn
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Huge accelerations in plasma simulation

I'm trying to make a numerical simulation of pulsar magnetosphere using FDTD on a log-spherical Yee lattice for fields and PIC for plasma particles. Field part is working like charm but issue arises when adding the plasma. To simulate the dynamics…
Tajimura
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Does radioisotope decay affect computer systems?

It is known that there exist a number of radioisotopes of elements commonly used in computer systems. Is the decay of these materials known to affect device performance over time, or is its impact so small as to be immeasurable? This question…
user26339
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Is this the correct way to calculate the Madelung constant?

I'm trying to compute the Madelung constant of the ZnS lattice. The method is as follows: The lattice is a face-centered-cubic with basis $S^-: (0,0,0)$ and $Zn^+: (1/4,1/4,1/4)$. The Madelung constant is $$\alpha=\sum_j \frac{q_j}{r_j}$$ where…
jinawee
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How to calculate collision force with no future knowledge

For a personal project, I am attempting to write a fairly realistic collision simulator (for relatively large objects, not quantum stuff). As I was consulting my physics textbook and various online resources such as this hyperphysics article, or…
NanoWizard
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Trigonometric equation (Lagrange) for the double pendulum

I want to model a fishing rod and received a suggestion. I therefore try to follow the mathematics (Lagrange) of the double pendulum. I do not understand how to proceed in the step that Wikipedia calls "Substituting the coordinates above and…
cvr
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