# 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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### Textbook recommendation for computational physics

Can anyone recommend some good textbooks for undergraduate level computational physics course? I am using numerical recipe but find it not a very good textbook.
2k views

### Physics of simple collisions

I'm building a physics simulator for a graphics course, and so far I have it implementing gravitational and Coulomb forces. I want to add collisions next, but I'm not exactly sure how to go about ...
293 views

### Distribution of orbital velocities in a disk galaxy for N-body simulation?

I'd like to write an N-body simulation in which I collide two disk galaxies. To give you an idea of the accuracy I'm trying to achieve, I'm aiming to make this my screensaver at 30fps on my work ...
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I have calculated formulas with 1 dimensional trajectory motion (free-fall) including quadratic drag, and have created the following equations. These equations of motion are not of much use on its ...
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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 ...
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### Superconducting gap, temperature dependence: how to calculate this integral?

Tinkham (page 63) states that the temperature dependence of the gap energy of a superconductor $\Delta(T)$ can be calculated using the following integral: How can this actually be carried out? I am ...
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### Binary Black Hole Solution of General Relativity?

This is rather a technical question for experts in General Relativity. An accessible link would be an accepable answer, although any additional discussion is welcome. GR has well known solutions ...
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### The hanging chain problem (catenary), numerically [closed]

I am supossed to solve the hanging chain in constant homogeneus gravity field: The chain of length $L_0$ is divided into $N$ parts which are homogenous with length $l$ and mass $m$ and connected by ...
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### How to determine velocity vector direction with respect to acceleration.

I'm currently writing a program that attempts to simulate particle movement in a gravitational field with more than one object exerting a force on it. I decided that I'd have the particle move by ...
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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 ...
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### How to solve the heat equation for compound materials with different heat conductivities numerically?

I'm solving the heat equation with time dependent boundary conditions numerically in a 2D system using the ADI scheme. For the purpose of this question, let's assume a constant heat conductivity and ...
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### Do mechanical stresses propagate in time as EM waves do?

If someone may, I expect a mathematical comparison of the governing equations "Maxwell Equations" for wave propagation and "Conservation of momenta & equilibrium equations" for stress and ...
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### Is limited computational capacity a fundamental obstacle?

Statistical physics books often motivate the necessity of statistical/thermodynamic description by impossibility of calculating the trajectories of all the molecules (I speak of "trajectories&...
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### Solving the two body problem numerically

I'm trying to solve the two body problem numerically, setting up $G$, $m1$ and $m2$ to be equal to 1. then I located each mass on positions -5 and 5 respectively along the $x$ axis and gave them both ...
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### How do I set up the tridiagonal matrix for a heat diffusion with layers of different thermal diffusivity?

I have Scala code that recreates the Crank-Nicolson solutions for the diffusion equations, and matches 'Excel for Scientists and Engineers' (Joe Billo, Wiley). However, I would like to be able to ...
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### Can we simulate the whole universe in computer? [closed]

Here is an idea: As human kind we discovered many laws, formulas, events, etc. in our surrounding environment.here is a way to discover the unknowns : Now if we simulate a virtual world with our ...
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### Euler Equations, Sod shock tube & conservation

Conservation of momentum? I am considering the Euler equations in conservative form and solving the Sod shock tube problem I have written a Godunov finite volume type solver. It solves for density ρ, ...
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In 3D the capillary number $Ca$ is defined as: $$Ca=\frac{\nu \rho U}{\gamma}$$ where $\nu$ is the kinematic viscosity ($m^2/s$), $U$ is the velocity ($m/s$)and $\gamma$ is the interfacial tension ($N/... 2answers 6k views ### Is it necessary to consume energy to perform computation? As far as I know, today most of the computers are made from semiconductor devices, so the energy consumed all turns into the heat emitted into space. But I wonder, is it necessary to consume energy ... 1answer 2k views ### Can lightning be used to solve NP-complete problems? I'm a MS/BS computer science guy who is wondering about why lightning can't (or can?) be used to solve NP complete problems efficiently, but I don't understand the physics behind lightning, so I'm ... 3answers 2k views ### Can we fully simulate molecular physics? Is our knowledge of physics complete enough to achieve fully natural simulations of molecular interactions in a computer simulation? How far off are we? Reason for question: I wonder how far we are ... 1answer 8k views ### Software for calculating Feynman Diagrams Is there a software (open source preferred) where I would input something like "Ingoing: a fermion$(p1, s1)$and a photon$(p2, s2)$. Output: A fermion$(k1, r1)$and a photon$(k2, r2)$" and I would ... 4answers 2k views ### Church-Turing hypothesis as a fundamental law of physics The Church-Turing hypothesis says one can not build a computing device which has more computing power (in terms of computability) than the abstract model of Turing machine. So, there is something in ... 1answer 3k views ### Is there an algorithm for N body simulations in General Relativity [duplicate] I am new to general relativity but have a background in computer science. Why is it so hard to do n-body simulations in GR? For example, there could be a program which takes the properties (mass, ... 1answer 689 views ### Gravitational field of thin 2D ring - numerical simulation I'm aware of Newton's Shell Theorem, which states that inside of a thin ring of uniform density, the gravitational force exerted on a point mass should be zero. I wrote a quick field simulation to ... 3answers 2k views ### Multiple colliding balls I have written an algoritm to resolve a collision between two balls with conservation of momentum. It looks to work exactly as expected in my simulations. Here is the code: ... 1answer 186 views ### Calculating distribution of force in a N-body system of balls With three balls placed in a pyramid on a static ground and under the influence of gravity, how will the force of gravity be distributed? The balls have different radius and mass. The initial velocity ... 1answer 519 views ### Hartree Fock equations I don't understand how the Hartree Fock equations define an iterative method! For this discussion, I am referring to the HF equations as described here: click me! Basically if you guess a bunch of ... 1answer 230 views ### Validity of finite difference method I am using the Finite Difference Method to solve Poisson's equation $$\frac{\partial \phi}{\partial z^2} = \frac{\rho}{\epsilon}$$ To do it is discretized according to the Finite Difference ... 1answer 844 views ### Explanation of relaxation method for Laplace's equation? Currently reading through Introduction to Electrodynamics (4th Edition) by Griffiths. I'm trying to wrap my head around Laplace's Equation, here are a couple quotes that I'd like to understand a bit ... 2answers 353 views ### Simulate the universe? Alright, Lets assume that I have a computer with limited calculation speed (1-4GHz) but unlimited parallel processing capability and unlimited memory capacity to go with it. Under this assumption ... 3answers 836 views ### Computerised Solar System Simulation [closed] In school I am doing a project where using python I simulate the solar system The physics I know so far is newtons laws and Kepler’s laws and I have done a lot of research but there appears to be ... 2answers 172 views ### Solving Keplerian two-body problem numerically? I'm trying to solve the two-body problem numerically, setting up G, m1 and m2 =1.0. The masses are placed at the positions -10 and 10 respectively along the x-axis and gave them both 0 on the y-axis. ... 2answers 16k views ### Numerical solution to Schrödinger equation - eigenvalues This is my first question on here. I'm trying to numerically solve the Schrödinger equation for the Woods-Saxon Potential and find the energy eigenvalues and eigenfunctions but I am confused about how ... 2answers 1k views ### 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 ... 12answers 3k views ### Is there an equivalent of computation of physical processes in nature? [closed] I was watching a waterfall in the Austrian Alps. There were thousands of water droplets falling down, splattering on the stones below. I thought - how does nature find out so quickly where each ... 1answer 5k views ### How to measure the spin-spin correlation in a Monte Carlo simulation of the Ising model? I'm simulating the Ising Model in 2D up to 5D and I want to calculate the spin-spin correlation, correlation length, and critical exponent of the system. What is a good way to go about doing this? ... 1answer 222 views ### Do black hole merger simulations include regions inside event horizons? Inspired by this question, I would like to ask the following specific point. In numerical simulations of general relativity that involve black holes, like the ones used to understand the black-hole ... 1answer 205 views ### Numerical relativity resources - Adaptive Mesh Refinement I have, in the past few months, been studying numerical relativity, specifically the problem of spherical collapse of a scalar field as studied by Choptuik. I have also taken a look at some books that ... 2answers 2k views ### Rotation matrix of Euler's equations of rotation relative to inertial reference frame I was playing with simulation of Euler's equations of rotation in MATLAB, $$I_1\dot{\omega}_1 + (I_3 - I_2)\omega_2\omega_3 = M_1,$$ $$I_2\dot{\omega}_2 + (I_1 - I_3)\omega_3\omega_1 = M_2,$$$$... 1answer 983 views ### Update velocity or position first in computation? I am trying to make a simulation of a vibrating string. The string is divided into$n$points, and each point along the string is acted upon by a force due to the positioning of its neighbors. I ... 2answers 4k views ### How do I integrate the Poisson equation to determine the electric potential along a particular direction (e.g.,$z\$)?

This question is a sequel of sorts to my earlier (resolved) question about a recent paper. In the paper, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, ...
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### Is it wasteful to use a heating element, instead of doing useful work?

Consider a computer CPU consuming electrical energy to perform calculations and consequently emitting heat. Assumption: That a CPU consuming x Watts of power, emits the same amount of heat as an ...
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### Feynman's infinite amount of logic for one tiny bit of space

Watching one of Feynman's lectures, I came across something that puzzled me. What was Feynman referring to when he said the following? What goes on in no matter how tiny a region of space and no ...
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### Numerical schemes, time integration algorithms and energy conservation

What does it mean when someone says a numerical scheme or a time integration algorithm is "energy conserving". How can a numerical scheme "gain" or "lose" or "conserve" energy apart from the numerical ...
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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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### Calculate Euler equations of fluid dynamics without division?

I'm working on the calculation of the Euler equations with the finite volume method. Unfortunately I'm not allowed to do a division. So I'm wondering if there's a form which does not need a division. ...
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### Calculating a two-dimensional orbital path with infinite granularity (non-Euler integration)

For a game I am making, I am trying to calculate the position of an orbiting object around one or more bodies. I have successfully implemented this gravity simulation by calculating the force, then ...