Questions tagged [computational-physics]

The bridge between theoretical and experimental physics which utilizes numerical analysis, specifically through the use of software, to solve problems in physics. This tag is NOT intended for use in solving problems on paper. 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.

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). Computational physics covers a wide range of subjects, such as , , and , among many others.
This tag should not be applied if your question is about computing a value without the use of a computer (i.e., solving a problem with pen & paper).

Types of questions we can answer here

  • We can advise on numerical methods when tied to a physical problem and not a generic PDE or ODE (e.g., What methods would one use to solve diffusion problems?)
  • We can discuss scheme quality/limitations (e.g. What makes the original Murman-Cole scheme not conservative in transonic potential flows?)
  • We can discuss scheme design (e.g., How does one determine if a scheme is conservative?)

Types of questions we cannot answer here

  • We cannot answer programming questions (e.g., How does one implement X method for Y equation?)
  • We cannot debug code (e.g. I programmed Crank-Nicolson, but it's not working; what did I do wrong?)
  • We cannot optimize code (My matrix inversion routine used for Crank-Nicolson is running slow; how can I speed it up?)
  • We cannot advise on libraries/languages/compilers/etc. (e.g. Should I use PETSc or Trilinos for my code? or Is Fortran better for scientific programming?)
  • We cannot provide help for using software (e.g., How can I modify the cross-sections in Geant4?)1
  • We cannot recommend software (e.g., What software can solve the diffusion equation?)

In general, if your question is about writing, compiling, debugging or optimizing a piece of code or is about a specific language or library, then it is off topic on Physics but may be on-topic on programming-oriented Stack Exchange sites such as Computational Science, Code Review or StackOverflow.


1. In many cases, software developers provide a user forum that would be appropriate for such types of questions.

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Is it necessary to consume energy to perform computation?

As far as I know, today most of the computers are made from semiconductor devices, so the energy consumed all turns into the heat emitted into space. But I wonder, is it necessary to consume energy to perform computation? If so, is there a…
jiakai
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Can we infer the existence of periodic solutions to the three-body problem from numerical evidence?

I recently found out about the discovery of 13 beautiful periodic solutions to the three-body problem, described in the paper Three Classes of Newtonian Three-Body Planar Periodic Orbits. Milovan Šuvakov and V. Dmitrašinović. Phys. Rev. Lett. 110…
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Can lightning be used to solve NP-complete problems?

I'm a MS/BS computer science guy who is wondering about why lightning can't (or can?) be used to solve NP complete problems efficiently, but I don't understand the physics behind lightning, so I'm posting here. What seems peculiar to me about…
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Intuition for when the replica trick should work and why it works

I am a graduate student in mathematics working in probability (without a very good background in physics honestly) and I've started to see arguments based on computations derived from the replica trick. I understand that it is non-rigorous but it…
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How were the Navier-Stokes equations found in the first place if we can't solve them?

I was reading up on the Clay Institute's Millenium prizes in mathematics. And I noticed the Navier-Stokes equations were described as minimally understood. As far as I was taught in physics a few weeks ago(SCQF Level 6), they are used but solutions…
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Software for calculating Feynman Diagrams

Is there a software (open source preferred) where I would input something like "Ingoing: a fermion $(p1, s1)$ and a photon $(p2, s2)$. Output: A fermion $(k1, r1)$ and a photon $(k2, r2)$" and I would could then get each diagram (that is, each term…
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Is there any aspect of an explosion resulting from a nuclear weapon test that cannot be simulated using super computers?

This Washington Post news article states that with the advent of computer simulation of nuclear tests, live tests are no longer needed. Generally speaking there are 3 aspects of an explosion resulting from a nuclear weapon test that are…
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How does a particle know how to behave?

How does a particle know it should behave in such and such manner? As a person, I can set mass is so and so, charge is so and so - then set up equation to solve its equation of motion but who computes that equation of motion for a particle in real…
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How do computers "solve" the three-body-problem?

I've done a bit of research, and have learned that computers "solve" the three-body-problem by using "Numerical methods for ordinary differential equations", but I can't really find anything about it other then Wikipedia. Does anyone have any good…
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Programming in physics

How important is programming in physics? I am studying physics at university and these first years there is actually no approach (as it is understandable) to what working in physics is like. Now, I know programming is actually important (I've read…
Klopmint
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Home-made lattice calculation?

The topic of Lattice QCD or Lattice gauge theory or even Lattice field theory is quite old now. And the main reason for the interest in the topic is the ability to calculate nonperturbative stuff on a computer. It seems that to do research with…
Kostya
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How can one obtain the metric tensor numerically?

I am self-studying General Relativity. Is there a method for obtaining the metric tensor exterior to a specified mass distribution numerically? In the simplest case of a spherical mass this should yield the Schwarzschild exterior geometry. I am…
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How efficient is a desktop computer?

As I understand it (and admittedly it's a weak grasp), a computer processes information irreversibly (AND gates, for example), and therefore has some minimum entropy increase associated with its computations. The true entropy increase is much…
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How many qubits are needed for useful computation?

Seeing the news about 14 entangled states today @ Innsbruck: I haven't found a clear guide online to how many qubits we are aiming for a first practical quantum computer, e.g. Factorization, Search or re-implementing large scale computing…
velniukas
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What do theoretical physicists need from computer scientists?

I recently co-authored a paper (not online yet unfortunately) with some chemists that essentially provided answers to the question, "What do chemists need from computer scientists?" This included the solution of theoretical problems, like…
Aaron Sterling
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