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.

learn more… | top users | synonyms

4
votes
1answer
153 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 ...
4
votes
1answer
417 views

Numeric method to calculate the charge distribution on a conducting surface?

If I have an arbitrary (closed?) conducting surface and a nearby charge density, is there a simple numeric way of computing the induced charge distribution on the surface?
4
votes
1answer
432 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 ...
4
votes
1answer
139 views

How to find positions of $n$ masses in Newton mechanics?

I ran into a problem while doing research. The problem can be described as: consider the original $n$-body problem, and if we fix the position of them(unknowns), no interaction among them, they don't ...
4
votes
1answer
249 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 ...
4
votes
0answers
98 views

Nature as a calculator [closed]

I wondered whether physical experiments can find the outcome of otherwise intractable mathematical problems. For example, solitons or other non-perturbative effects in QFT cannot be seen at any ...
4
votes
2answers
214 views

Can computers accurately model all of the details (to the subatomic level) of macro objects in collisions?

Frequently when trying to solve cosmology questions physicists turn to computer simulations of the universe (albeit massively simplified) in order to verify or disprove their hypotheses. This got me ...
3
votes
3answers
372 views

Can a wavefunction be solved to any arbitrary precision, given enough computer time?

I learned that the wavefunction for the hydrogen atom can be solved analytically (we did the derivation in class), but that for more complicated atoms it is "impossible" to solve and that only ...
3
votes
1answer
102 views

buiding circuits from color superconductors

caveat: the sort of exotic matter engineering in here is currently beyond the reach of our technology, but, that having been said: Has their been any research on building models of these sorts of ...
3
votes
2answers
343 views

Mixed conductive and convective heat transfer

I want to make a finite element analysis of a cold airflow through warmer pipes. In particular I want to see how the pipes cool down and the air heats up, as it travels through the pipes. Wich are the ...
3
votes
1answer
143 views

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, ...
3
votes
2answers
160 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 ...
3
votes
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. ...
3
votes
2answers
190 views

Boundary Element Method or Boundary Integral Method Computational Aspects

I have to solve a Helmholtz equation inside a simply connected domain. I know that in general the boundary integral can be written as, $$\phi(x)=\int_V G(x,x') \rho(x')\ d^3x'+\int_S ...
3
votes
1answer
76 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 ...
3
votes
2answers
657 views

Can I use imaginary time propagation for many-body problems?

There are various ways to numerically find the ground state energy and wavefunction of a many-body Hamiltonian. You can diagonalize the Hamiltonian and pick out the lowest eigenstate, or you use ...
3
votes
3answers
479 views

Adding rotation to internal coordinates

I'm optimizing the geometry of a system composed of several interacting masses (a molecule). The energy of the system depends on the relative position of the masses, and all velocities are zero. In a ...
3
votes
1answer
567 views

Numerical computation of the Rayleigh-Lamb curves

The Rayleigh-Lamb equations: $$\frac{\tan (pd)}{\tan (qd)}=-\left[\frac{4k^2pq}{\left(k^2-q^2\right)^2}\right]^{\pm 1}$$ (two equations, one with the +1 exponent and the other with the -1 exponent) ...
3
votes
1answer
56 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 ...
3
votes
1answer
126 views

Looking for a good introductory-level review of pseudopotential methods

I'm looking for a good introductory-level review of pseudopotential methods. In particular, I'd like to understand how the self-consistent pseudopotential methods work.
3
votes
1answer
75 views

Complex semi-definite programming

I'm doing some calculations and I want to simulate them in python or matlab (or whatever). However I use hermitian matrices and I don't really manage to find a library which enables me to calculate ...
3
votes
1answer
179 views

Epsilon Tensor in FeynCalc

A few days ago I started to use the Mathematica package FeynCalc and one thing confuses me: Assume we have a four-vector $p_\mu$ and we contract it with the epsilon tensor. FeynCalc produces ...
3
votes
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 ...
3
votes
1answer
201 views

confusion in discrete transform to solve kronig penney matrix equation in fourier space

I have a periodic potential $$V(x) =\sum_{K}e^{iKx}V_{K} =\sum_{n}e^{\iota2\pi nx/a}V_{n} $$ where $K =\frac{2\pi n}a$ is the reciprocal lattice vector and $a$ is the lattice constant and $n =\pm ...
3
votes
1answer
127 views

How to determine predicted CP violation for a given SUSY point?

I'm currently studying at the spectra of some supersymmetric models, and would like to know whether the parameter points I'm looking at are ruled out due to excessive CP violation. I am using SPheno, ...
3
votes
1answer
226 views

Using Relaxation Method to Model Negative Dielectrics in an electric field?

How can you use the relaxation method to model negative dielectrics? The relaxation method is usually used to model electrostatics problems but negative dielectrics are only see in dynamic systems. ...
3
votes
0answers
53 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 ...
3
votes
0answers
171 views

What is the probability of quantum tunneling occurring in this CPU?

You may have noticed over the last few years that Moore's law is no longer applying to the real world. This observation states that over the history of computing hardware, the number of transistors on ...
3
votes
0answers
194 views

Comparison between Cadabra and other Symbolic Computer Algebra software [closed]

Does anyone has some experience about working with Cadabra and it's (dis)advantage in comparison to other Symbolic Computer Algebra software such as Maple and Mathematica (physics package) in the ...
3
votes
0answers
696 views

Numerical problem in solving the Bogoliubov de Gennes equations- methods to solve?

I am trying to solve an assignment on solving the Bogoliubov de Gennes equations self-consistently in Matlab. BdG equations in 1-Dimension are as follows:- $$\left(\begin{array}{cc} ...
3
votes
0answers
130 views

Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model

In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
3
votes
0answers
587 views

Comparison of different ab-initio codes

One may find on the web a lot of different computational packages to perform "ab-initio" calculations of electron structure of the solids. Usually, the documentation is not quite transparent about the ...
2
votes
4answers
267 views

Computer Science Modeling of Physical World

I am curious what efforts have been made to date to define virtual computer worlds based on the physics we know in the real world? I think it would be awesome to say start off with an atom defining ...
2
votes
3answers
74 views

Is it possible to reconstruct the wavefunction of a molecule from a collection of spectra?

Spectra of a molecule can be calculated if the wavefunction is known. Is it possible to do the opposite?
2
votes
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 ...
2
votes
2answers
115 views

Modeling a potential well

I attempted to simulate the interaction of a moving particle and a potential well in Mathematica. The particle should experience a force of -$1/r^2$, if the equation for the potential well is -$1/r$. ...
2
votes
2answers
112 views

Sampling a distribution (from a galaxy model)

I am reading the following article: http://www.kof.zcu.cz/st/dis/schwarzmeier/galaxy_models.html and am currently at section 5.6 (positions of bodies in a galaxy). I am trying to redo the simulations ...
2
votes
1answer
76 views

Question about Metropolis Monte Carlo in the case of equal energies

If configuration A is equal to configuration B in a Metropolis Monte Carlo method, do you still do the attempted update?
2
votes
2answers
321 views

Computational Science involve programming? [closed]

I read what is computational science in Wikipedia but the explanation and understanding are not very clear. So, I could you please give a simple example computational science project and what all ...
2
votes
2answers
172 views

Why are Markov chains better than naive algorithm for Random picking?

I have a question about the problem of coming up with a random distribution of non-overlapping coins in a given two dimensional space. I don't understand why using the random sequential adsorption ...
2
votes
1answer
517 views

How is acceleration computed in the leap-frog algorithm in computer simulations of particles?

I am reading the book Computer Simulation of Liquids by Allen and Tildesley (here is another link). On page 80, the authors describe the leap-frog algorithm, which is used extensively in molecular ...
2
votes
1answer
155 views

If the graph isomorphism problem can't be solved in polynomial time, do spin-networks in loop quantum gravity violate the Church-Turing thesis?

If the graph isomorphism problem can't be solved in polynomial time, do spin-networks in loop quantum gravity violate the Church-Turing thesis? To determine whether or not two graphs are isomorphic ...
2
votes
2answers
320 views

Why can't we set the lattice spacing 'a' in lattice QCD?

My question is to do with lattice QCD. In the lattice action there is a parameter, 'a', the lattice spacing in physical units. However, if we want to generate a configuration with a certain lattice ...
2
votes
2answers
223 views

numerical formulation of Dirac equation plus electromagnetic field

I have the following equations describing the electron field in a (classic) electromagnetic field: $$ c\left(\alpha _i\right.{\cdot (P - q(A + A_b) + \beta mc) \psi = E \psi } $$ where $A_b$ is ...
2
votes
1answer
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, ...
2
votes
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, ...
2
votes
1answer
136 views

Numerical Ising Model: Swendsen–Wang algorithm, Percolation theory?

When you look at the original paper of Swendsen and Wang in 1987: "Nonuniversal critical dynamics in Monte Carlo simulations" it is somewhat mentioned that the proposed algorithm uses percolation ...
2
votes
1answer
101 views

The number of mean free paths which a particle traverses is independent of the material traversed

This is a manual from a Monte Carlo physics manual: Computing the occurrence of a process Can anyone tell me why the number of mean free paths of a particle is independent of the material which it ...
2
votes
1answer
777 views

Lennard Jones liquid vapour phase transition

I am trying to generate a phase diagram of pressure versus temperature in a NPT ensemble using molecular dynamics method. I am using the Lennard Jones potential with 108 particles and Berendsen ...
2
votes
1answer
127 views

Mutual Interaction of $N$-Particles in a Cartesian Plane

I am making a simulation of $N$-Particles in a cartesian plane and need help with understanding the basics. At anytime, in my particle system, I will have $N$ number of particles. I am treating the ...