Subdiscipline of theoretical physics which consists in the study of physics problems using numerical algorithms. PLEASE NOTE that questions about computational methods and/or programming are OFF-TOPIC on Physics.SE.

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385 views

Does the universe follow a general physical and computational principle of evolution?

Evolution is a principle in biology, whereby organisms evolve their ability to replicate and multiply in numbers over successive generations. From a computational point of view, the organisms employ a ...
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41 views

Creating a realistic simulation [on hold]

I've recently read an article from I believe it was Cambridge or something, where they created an extremely detailed simulation of bubble interaction. I've come here to ask what are some common ...
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1answer
45 views

Using the Fourier transform to find the natural frequencies of coupled oscillators

How can I find the natural frequencies of a system consisting of a pair of coupled oscillators using Fourier transforms? The System consists of two masses and three springs. One of the springs ...
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259 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 ...
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20 views

Introduction material for lattice field simulation

I am looking for introductory material of lattice field theory simulation. It is better start from simple example (e.g. \phi^4) and include some source code. Is there any on-line or book which is ...
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2answers
388 views

How do you simulate chiral gauge theories on a computer?

David Tong and Lubos Motl have argued that our universe can't possibly be a digital computer simulation because chiral gauge theories can't be discretized, and the Standard Model is a chiral gauge ...
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14 views

Ising Model 2D Correlation Length

I'm using Metropolis and Wolff Clustering algorithms to estimate the spin-spin correlation function $$<s_os_r>$$ I know that this is related to the correlation length but how do we determine ...
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1answer
67 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? ...
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37 views

Ising model Monte Carlo simulations in 4D and 5D

I'm going to be simulating the Ising Model in 4D and above to calculate spin-spin correlations and critical exponents and am wondering how to tackle this algorithmically. For example, in 1D, use an ...
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1answer
191 views

Position based dynamics constraint scaling factor

Reading through Müller et al., Position Based Dynamics, 2007 I got lost when passing from equation (5) $$\Delta p = \frac{C(p)}{|\nabla_pC(p)|^2}\nabla_pC(p)$$ to equation (6) (and applying the ...
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177 views

My python trajectory calculator for a small mass in a gravitational field - why is energy conservation violated?

I wrote this thing to calculate the next position of a small mass, given its current position and velocity, and a vector field determines acceleration. It sort of works - except I can never get the ...
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34 views

Probability density function of a particle for computation [closed]

I'm writing a program, part of which relies on a particle being able to change location similar to a how a real particle would behave (pardon my physics). For example, on a grid of 100x100, a ...
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37 views

Why are functional representations of systems important in physics or computational physics?

This was an addendum to a previous question I asked, but I figured I should make it it's own discussion. Assuming I am able derive a functional representation for any dynamical system (dissipative, ...
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159 views

Problems while numerically computing band structure using k.p theory

I want to use k.p theory to numerically compute the band structure of a bulk semiconductor. The band I like to include are the lowest conduction band (cb), the heavy-hole (hh), the light-hole (lh) and ...
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1answer
54 views

Leapfrog method in Particle-in-cell

Recently I wanted to write a 3D electromagnetic Particle-in-cell code with c++.I know that I should use leapfrog method.For example,when I calculates the position and velocity of particles,i should ...
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1answer
31k views

How does force relate to velocity

I had originally asked this question on math overflow and it was suggested that I ask it here. So I know that a force will change the magnitude of velocity if it is at an angle other that 90 degrees. ...
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3answers
76 views
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30 views

Hard processes in particle collisions

This is in reference to a MC generator called Pythia, but has wider applicability because the phrases are used widely in particle phyiscs, even though I have not managed to find a clear, ...
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22 views

Cellular automata and time T

Reading around about various CA models I saw that there are even those who are following the track to provide a single mechanicist model of the universe. For example Gerard van 't Hooft claims that ...
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3answers
105 views

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.
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57 views

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 ...
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1answer
21 views

How do we define capillary number in 2D (two dimensions)

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 ...
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1answer
77 views

Why is the objective function used in Nudged Elastic Band method reasonable?

In Nudged Elastic Band (NEB) method, which is used to find reaction pathways when both initial and final states are know, an objective function is first constructed and then minimized to find reaction ...
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17 views

Why breakdown voltage decreases with increasing FWHM of an asperity?

I am running a simulation for a dielectric breakdown. I am getting breakdown voltage decreases with FWHM, which does not make sense as field enhancement is higher for a small width. Simulations solve ...
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1answer
25 views

Effects of terrain on outdoor sound propagation?

I'm looking for a computationally fast model for capturing the effects of varying terrain topology in far-field outdoor acoustic propagation, and was wondering if anyone had any insight or could point ...
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106 views

How to compute matsubara frequency summation over computer?

Matsubara frequency sum usually takes the following form: $S_\eta = \frac{1}{\beta}\sum_{i\omega_n} g(i\omega_n).$ But in my problem, $g(i\omega_n)$ is a lengthy expression, which can not be ...
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30 views

2D room with electron-point-charges (stability)

Is there a fast way to find out stable #"point charges" & constellation for this kind of Simulation. The 2D repeating itselve in each direction till infinity, so i've a kind of symetrie here. ...
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26 views

How can the fictitious mass in the Car-Parrinello method reproduce the “real” dynamics?

In the Car-Parrinello method, to solve simultaneously the classical equations of motion for the atoms and the Kohn-Sham equations for the electrons, the following effective Lagrangian is used: $$ ...
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29 views

Molecular dynamics and detailed balance

In developing methods to perform Monte Carlo simulations one sufficient condition to preserve the stationarity of the target probability distribution is to impose detailed balance i.e. [Gardiner page ...
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1answer
61 views

Possibility of simulating quantum physics and relativity [closed]

I must be clear; this is not a 'specific' question, but rather a hypothetical one. As of now, computer physics simulations are becoming more and more advanced, and I am programming one now. I was ...
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3answers
158 views

Do algorithms have an intrinsic time direction?

This article says There is no intrinsic time direction in Newton's mechanics nor in the differential equations of the new physics. My question is, do other types of mathematics, say a cellular ...
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1answer
127 views

reversible cellular automata

Let's suppose a cellular automaton has a value $b(r,t)$ belongs to $Q$ at site $r$ and time $t$, where $Q$ is the set of possible states at each site. Let $N(r, t)$ be the values of the states of all ...
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54 views

black body simulation

black body radiation is typically understood from Planck's argument of light resonance in a box, from which the density of states is computed. Now, suppose I want to simulate a black body ...
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77 views

The use of Artificial Intelligence in physics resarch

I have been reading about a machine that observed a double pendulum and created equations that both described its motion and associated conservation laws. The authors claims: We have developed a ...
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1answer
113 views

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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30 views

Mass scaling in molecular dynamics

I've noticed some authors scale the mass of particles in molecular dynamics simulations while leaving the force field parameters the same in order to achieve materials of different densities. Does ...
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1answer
41 views

Thermal conduction through 1D rod with changing thermal diffusivity?

I've been working with solving partial differential equations in 1D numerically using the finite difference scheme. My case is for example this: I've got a rod that's insulated around the sides such ...
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1answer
98 views

How close to the critical point is sufficient close for measuring critical exponents?

I am learning Monte Carlo and just manage to simulate a phase transition by computing the heat capacity or the susceptibility. I wish I can also compute critical exponents.To this purpose, I have read ...
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1answer
156 views

Why is the ground state energy of the Heisenberg XXZ Model unbounded for some values of $J$?

At the moment, I'm looking at numerically studying the Heisenberg XXZ model. The Hamiltonian is given below: $$ H=\sum_{j=1}^{N-1}\left(J S_j^z ...
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1answer
53 views

FDM versus fdtd for computational electromagnetics

Every article I've seen on computational electromagnetics uses the Yee fdtd algorithm, and I'm wondering if would be possible to do the same analyses using out of the box FDM with more data points, ...
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1answer
117 views

Monte carlo simulation for continuous spin model (e.g. XY or Heisenberg model)

Unlike the Ising model, the XY model and the Heisenberg model have a continuous spectrum. So one need discretize them for a numerical simulation. But how to make sure the discretization procedure ...
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1answer
41 views

Ideas for physics-related simulations to code up as weekend (or monthly) projects [closed]

What are some good ideas for simulations that I could try to implement/code in my spare time just for educational purposes? I'm thinking that it would be a good way for me to delve into the underlying ...
4
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1answer
435 views

Philae lander simulation off by factor of ~3

I'm trying to simulate the Philae landing by writing a program to compute the position of the lander vs time. According to various mission websites, the orbiter will match its orbit to the rotation of ...
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3answers
834 views

Calculate kinematics of body movement from the set of spatial coordinates

Short intro I have a set of 3D (x,y,z) spatial coordinates of arm movement obtained using motion capture system. The example set of such coordinates looks like this (rounded up): ...
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1answer
811 views

Calculating semi-major axis of binary stars from velocity, position and mass [closed]

I'm trying to calculate the 'instantaneous' semi-major axis of a binary system with two equal (known) mass stars for an $N$-body simulation. I know their velocities and positions at a given time, but ...
4
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1answer
154 views

Good source for numerical simulations of Wigner function?

I'm interested in simulating the time evolution of a Wigner function for a harmonic oscillator (and possibly some other potentials) and I can't seem to find a good resource for that. My background in ...
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22 views

Optimize locations of vertices and edge length using physics without simulation

I have a directed graph with set of vertices and edges. Each vertices don't have a position coordinate to be displayed on 2D computer screen. I want to add unique position coordinate to each vertices ...
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1answer
204 views

Ray tracing in General Relativity

I would like to find out what one would see at the Schwarzschild radius of a massive non-rotating black hole, if the black hole is surrounded by a bright ring. For that, I would place the observer at ...
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1answer
47 views

Software for calculating the trajectory of a body in a coordinate system

I'm looking for a program, which would simulate the path of motion of a body in a coordinate system, given the force acting upon the body. I'd type in the initial conditions such as the velocity, ...
5
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1answer
81 views

Least action principle — numerical simulation strangeness

I'm trying to get some experience with the least action principle, and for this I chose a simple 1-dimensional problem of a particle moving in some field. The least action principle would then look ...