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72
votes
10answers
12k views

Is time continuous or discrete?

While working on physical system simulation software, I noticed that I had implemented discrete time, which means that there was an update mechanism advancing the simulation for a fixed amount of time ...
30
votes
6answers
6k views

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 ...
18
votes
2answers
1k views

Why can't Humans run any faster?

If you wanted to at least semi-realistically model the key components of Human running, what are the factors that determine the top running speed of an individual? The primary things to consider would ...
17
votes
3answers
1k views

What open-source n-body codes are available and what are their features?

I'm interested in doing simulations with large numbers of particles and need a good n-body code. Are there any out there in the public domain that are open-source and what are their strengths and ...
16
votes
1answer
4k views

How realistic is the game “A slower speed of light”?

The game "A slower speed of light" from MIT claims to simulate effects of special relativity: Visual effects of special relativity gradually become apparent to the player, increasing the ...
15
votes
2answers
74 views

Sampling typical clusters between distant points in subcritical percolation

I have on several occasions wondered how one might proceed in order to sample large subcritical Bernoulli bond-percolation clusters, say on the square lattice. More precisely, let's consider the ...
14
votes
5answers
4k views

Does there exist a free good molecule / atom simulation software?

I'm looking for a software or software package (for example C/C++) that can simulate a lot (say thousands at least) of molecules in action (ie. in movement or attached to say static walls). I have ...
13
votes
3answers
17k views

Where can I find simulation software for electricity and magnets?

Is there easily-available* software to simulate coils, solenoids, and other magnetic and electromagnetic devices? I'd like to play around with some design ideas, such as Halbach arrays, but physics ...
12
votes
14answers
33k views

Best (most realistic) physics game? [closed]

Inspired by a similar post, I wanted to know what video games, past or present, most accurately employ the laws of physics. I believe this is an appropriate question for this site, since the users ...
12
votes
1answer
824 views

Solution to the Schrodinger equation for periodically time dependent Hamiltonians

I have a Hamiltonian which is time dependent but possesses periodic symmetry: $H(t+t_0)=H(t)$. Is there any clever techniques to exploit this? Edit: In particular, I would like a practical method to ...
11
votes
6answers
4k views

How many bits are needed to simulate the universe?

This is not the same as: How many bytes can the observable universe store? The Bekenstein bound tells us how many bits of data can be stored in a space. Using this value, we can determine the ...
11
votes
2answers
980 views

Use of Monte-Carlo simulation in High-energy Physics

I've been doing some research into the analysis used in particle physics when determining the significance of a finding (e.g. the recent Higgs candidate was announced as a boson in the 125-126 ...
11
votes
3answers
1k views

When is the “minus sign problem” in quantum simulations an obstacle?

The "minus sign problem" in quantum simulation refers to the fact that the probability amplitudes are not positive-definite, and it is my understanding that this leads to numerical instability when ...
11
votes
2answers
2k views

How to model/simulate pressures and flows in a network of pipes

I'm having a hard time finding information on how to model/simulate this. I attached a couple files, both of which show an example tank & pump network. It's just nonsense that I made up for this ...
10
votes
2answers
1k views

How are Monte Carlo simulations used in experimental high energy physics?

How are Monte Carlo simulations used in experimental high energy physics? Particularly in studying detectors limitations (efficiencies?) and data analysis. I will appreciate giving a simple example ...
10
votes
3answers
463 views

Are there models/simulations of antigravitational antimatter-galaxies?

In the comments to another question's answer, I started wondering: Assuming antimatter possessed negative gravitational mass§ (which is not proven impossible to date, though deemed unlikely), ...
10
votes
1answer
546 views

Why doesn't my particle simulation end in a flat disc?

I've made a 3d particle simulator where particles are attracted to each other by the inverse of the square radius. The purpose of my experiment is to see if this alone would create a flat disk (like ...
10
votes
2answers
4k views

LED Thermal Modeling (How to solve heat equation with constant heat source)

I have a mechanical design with LEDs that generate heat. I want to estimate the temperature at the LED junction vs. time, but especially at steady state. Knowing the LED voltage drop and current, I ...
9
votes
3answers
2k views

What happens if you slow down a moon?

Let's say you'd put a whooping big rocket engine on the surface of the moon, and slow down its orbital velocity. Not to a complete stop, mind you. Just a bit slower than it was going before (a couple ...
9
votes
1answer
168 views

How can one build a multi-scale physics model of fluid flow phenomena?

I am working on a problem in Computational Fluid Dynamics, modeling multi-phase fluid flow through porous media. Though there are continuum equations to describe macroscopic flow (darcy's law, ...
9
votes
2answers
223 views

In a Monte Carlo NVT simulation How do I determine equilibration

I'm running an NVT (constant number of particles, volume and temperature) Monte Carlo simulation (Metropolis algorithm) of particles in two dimensions interacting via Lennard-Jonse potential ($U = ...
8
votes
10answers
203 views

Are there websites or programmes that permit a simulation of the night sky in the past and the future on an ordinary computer?

Are there websites or programs that permit a simulation of the night sky in the past and the future on an ordinary computer? (For the past, I would be content with objects visible to the naked eye.) ...
8
votes
1answer
1k views

physics of wet hair

I'm curious about the physics behind the clumping of wet hair. More specifically, how the amount of water in hair and distance between hairs affect the clumping process. I know intuitively that when ...
8
votes
7answers
8k views

Is there a general physics simulator for learning purposes?

Is there a complete physics simulator that I can use to do general simulations for learning purposes? For example: Create a sandbox. Fill with a gas. Load a 3d solid model like this (but 3d). Fill ...
8
votes
1answer
213 views

How do subgrid-scale parametrisations in climate models work?

Global Circulation Models typically have grids of 100-300km on a side. There are obviously lots of atmospheric processes that happen at smaller scales than this. Convection, cloud formation, the ...
8
votes
1answer
2k views

Riemann invariants…Any physical interpretation?

I am really new to the CFD simulation, and started some simple algorithms recently. I then got introduced to the Riemann Invariants. Can any one provide some physical interpretation? Also, why is ...
8
votes
1answer
2k views

What are the limitations of Smoothed-Particle Hydrodynamics?

I've been excited by some of the possibilities of Smoothed-Particle Hydrodynamics (SPH). I have seen some very exciting demonstrations of their use in 3D graphics, but I am wondering how well the ...
7
votes
3answers
1k views

Most True to Life Physics & Biology Simulation Engine? [closed]

I'm a programmer. I code in C++, C#, HTML5, and PHP. There are many graphics engines I have at my disposal. The question is: Does there exist a graphics engine that is as true to our reality as ...
7
votes
5answers
1k views

Why do objects in a gravity simulation experience sudden large accelerations?

I'm trying to create a simple program that simulates gravity. The idea is that I have one central sun and several planets that I can create with a swipe gesture on the screen, and I use the initial ...
7
votes
2answers
292 views

Simulation of QED

Can anyone point me to a paper dealing with simulation of QED or the Standard Model in general? I will particularly appreciate a review paper.
7
votes
2answers
620 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 ...
7
votes
2answers
259 views

Why do we still use perturbation theory, when we have advanced numerical methods and fast computers?

If my question sounds ignorant or even insulting, I apologise. I may be completely wrong, since I'm not a theoretical physicist. So, I understand why perturbation theory was originally used in ...
7
votes
2answers
1k views

Numerical Ising Model - Wolff algorithm and correlations

I'm doing some numerical Monte Carlo analysis on the 2 dimensional Ising model at the critical point. I was using the Metropolis 'single flip' evolution at first with success, though it suffers from ...
7
votes
1answer
390 views

How to simulate a crashing wave? [closed]

I'd like to create a very rough animation of a wave crashing on a beach. I'm guessing it would have to be a particle simulator, where you code in the forces between the particles and then integrate ...
7
votes
1answer
271 views

Simulating the evolution of a wavepacket through a crystal lattice

I am interested simulating the evolution of an electronic wave packet through a crystal lattice which does not exhibit perfect translational symmetry. Specifically, in the Hamiltonian below, the ...
7
votes
1answer
244 views

Converting between $\frac{d \sigma}{d t}$ and $\frac{d \sigma}{d \Omega}$

I'm performing some simulation where I require the integration of a cross section of the form $$\sigma = \int_{-s}^{0}dt \frac{1}{(t-\mu^2)^2} f(\theta,\phi)$$ where $s$ and $t$ are the usual ...
7
votes
1answer
375 views

Parton showering in Pythia 6 Monte Carlo generator

I have Pythia Monte Carlo (MC) samples where I can't understand the parton showering model. If I print out full decay chains from the events, each event contains multiple string objects with pdgId 92. ...
6
votes
6answers
27k views

Free Optics Simulation Programs

I'm having an extremely difficult time finding an optics program that is easy to use and offers accurate physics simulations. I'm not asking for much, I just want to be able to simulate a laser going ...
6
votes
5answers
444 views

Resolving General relativity and Newtonian mechanics to a computer [closed]

I know this is considered an old subject long ridiculed by many as the folly of layman. But I work in the field of computer simulation, specifically in producing fully functional 3D interactive ...
6
votes
4answers
455 views

Monte Carlo use

Where is the Monte Carlo method used in physics?
6
votes
4answers
4k views

Trampoline physics - what is the right time to crouch and to jump to maximize your height?

Please bear in mind that I'm neither a physics guy nor particularly a math guy. So I will probably need a bit more hand-holding than just a complex equation. For a game, I'm trying to calculate a ...
6
votes
1answer
671 views

Kerr geodesics differential equations in equatorial plane

With friend, we are writing an interactive educational simulation of particle falling into a black hole. Currently we use Schwarzschild geodesics. However, we want to generalize it to the case of ...
6
votes
3answers
559 views

How to include random force in the simulation (Classical Molecular Dynamics)

I need to implement a random force in my code according to the fluctuation dissipation theorem. I have a Gaussian distribution function ready width average 0 and distribution 1 and I know I need to ...
6
votes
2answers
336 views

Physics and math behind flight through solar system: Where to start?

I wrote a first program that simulates a solar system. I was able to calculate the locations for every planet on its elliptical route for any given time. In a second program i managed to simulate ...
6
votes
1answer
555 views

Why do air bubbles stick to the side of plastic tubing?

I'm watching water with air bubbles flow through transparent plastic tubing. The inner diameter is a few mm. Bubbles typically are the same diameter as the tubing, with length about the same or up ...
6
votes
1answer
493 views

Cellular automata rules for quantum mechanics

My limited understanding of quantum theory is that a quantum system is completely described by its wave function, which deterministically evolves according to Schrödinger's equation until wave ...
6
votes
1answer
1k views

The skin effect and the reflectivity of gold

I am simulating a waveguide in COMSOL, a FEM solver. My model looks like this (it is similar to a standard Quantum Cascade Laser geometry): Therefore there is a very thin (30nm) layer of gold ...
6
votes
1answer
381 views

partial trace with sparse matrices

Let $\rho_{ABCD}$ be a sparse matrix of 4 systems each in a $d$-dimensional Hilbert space. For $d<7$ in a reasonable time (few seconds) I able to perform the partial trace $\rho_{AD}$ using the ...
6
votes
1answer
180 views

How can I simulate a model electronic hole?

Suppose I can solve time-dependent Schrödinger equation for several 1D particles (currently 3). I'd like to see, what an electronic hole is and how it behaves — in a series of numerical experiments. ...
6
votes
0answers
141 views

Final-state baryons in $p \bar p$ collisions in Pythia

I'm trying to simulate inclusive $\chi_c$ production in $p \bar p$ collisions at very low energies (~ 5.5 GeV) using Pythia8 event generator. Leaving aside problems bounded with applicability of ...