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2
votes
2answers
143 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
1answer
570 views

How to get the new direction of 2 disks colliding?

I'm developing a 2D game including collisions between many disks. I would like to know how I can get the angle corresponding to the new direction of each disk. For every disk I have this information :...
2
votes
1answer
63 views

Could there be a sort of “Molecular Destiny”?

Let's say we start with the Big Bang. Every bit of matter started from this event. Therefore, given EVERY variable (every particle, movements of particles, weights, times, etc) and an INFINITE amount ...
2
votes
2answers
75 views

time step in kinetic montecarlo simulation

I have a doubt about how the time step is calculated in kinetic montecarlo simulations. One state with index $i$ is connected to other $N$ states, indexed by $j=1...N$, by transitions that happen ...
2
votes
1answer
103 views

Monte Carlo with zero-temperature: trapped in a local minimum

I have a problem reaching the correct ground state while performing a Monte Carlo at zero temperature. Some parts of the system get trapped in a local minimum, and for getting the global one (the ...
2
votes
2answers
82 views

how to simulate a steep potential barrier in langevin equation

When simulating a Langevin equation, how is a vertical potential barrier handled? I have the time overdamped evolution of the position $x$, described by $\gamma\frac{dx}{dt}=-V'(x)+\eta(t)$ where $...
2
votes
2answers
114 views

Center of mass chaotic in n-body gravitational interactions?

I wrote a gravitational particle simulation. To prevent the particles flinging off out of the screen, I added a bit of friction (it also makes the animation prettier as particles spiral into one ...
2
votes
1answer
293 views

Local minima in Ising model in a Monte Carlo simulation

Is there any way to check whether in a Monte Carlo simulation using Ising model is stuck in any (false) local minima of energy or not, particularly in 3D system ?
2
votes
1answer
97 views

Damping a spring force

I'm modelling particles in a system using a spring and damper force. $$F= kx -cv$$ $x=x_i -x_f$, where $x_i$=centre of spring and $x_f$= displaced position. Above $x$ is the displacement and $v$ is ...
2
votes
2answers
69 views

How do I modify a 3-D simulation grid to be 2-D?

I am creating a particle in cell simulation that models an electron plasma in a cylindrical container. Part of this process is assigning charge density to grid points based on the position of each ...
2
votes
1answer
89 views

Quantum Space Simulation

There are a number of simulators, which simulate the macroscopic world around us (Space Engine: http://en.spaceengine.org/ comes to mind, but there is also Universe Sandbox). My question, does ...
2
votes
2answers
177 views

If you “disobey” the constraints of the Kramers-Kronig relations, what happens? Do you get non-physical results?

If you "disobey" the constraints of the Kramers-Kronig relations, what happens? Do you get non-physical results? I am simulating reflection and transmission off/through a slab of material. I specify ...
2
votes
2answers
551 views

How to calculate velocities after collision?

I'm currently writing a program for a particle simulator. One of the requirements is that the particles collide in a realistic way. However, I don't know how to calculate the final velocities. For ...
2
votes
1answer
89 views

Any FLOSS Monte-Carlo package for reactor physics? [closed]

Any FLOSS Monte-Carlo package for reactor physics? Are there any Free and Open Source software packages for nuclear reactor processes simulation? Maybe, something similar to MCNP?
2
votes
2answers
183 views

How should I simulate the electric potential field from a wavefunction?

I was interested in making what I thought would be a simple simulation of an electron encountering a positron by numerically solving the Schrodinger equation over several time steps, but I've run ...
2
votes
3answers
137 views

How much space to simulate a small Hilbert space?

I'm thinking about trying to do a numerical simulation of some very simple QM problems. How much space do I need? To simulate the Hilbert space? I'd like to eventually simulate the absorption or ...
2
votes
1answer
736 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
50 views

Current Status of the Monte Carlo Sign Problem

I've been reading about the Monte Carlo sign problem, and I am a little confused about its current status. Specifically, after reading this post When is the "minus sign problem" in quantum ...
2
votes
2answers
99 views

Limitations of particle in cell method for high desnity plasma

Are there any limitations of particle in cell (PIC) method for high density plasma? To be more specific, is modelling of a narrow channel of high density plasma possible or are there any limitations ...
2
votes
1answer
195 views

Problems implementing Lattice Boltzmann method

I want to make a basic 2D implementation of the Lattice Boltzmann method (in javascript) to simulate gas/fluid flow, but I have run into some problems and I can't seem to find the cause of it. ...
2
votes
5answers
109 views

Is more lift always better?

In the domain of aircraft, and more specifically powered flight, is there any case in which you wouldn't want the airfoil used to generate as much lift (and as little drag) as possible at a null angle ...
2
votes
3answers
266 views

Calculating vector to aim for moving asteroid (3D asteroid game)

Considering we're in a 3D system of coordinates: our ship is at point A, motionless our ship can shoot bullets, the speed of which is known the asteroid is at point B the asteroid is moving on known ...
2
votes
1answer
312 views

Simulation of fluid flow using Euler equation

I have been looking on Euler's equations for a while and can't grasp one thing. Suppose we have initial system state with volumes of fluid "hanging" in air (time is frozen and equal to zero), each of ...
2
votes
1answer
189 views

Simulating a 1-dimensional wave on (a segment of) an infinite line

I'm trying to numerically simulate a 1-dimensional with a chain of linked harmonic oscillators as described here (the result can be seen here). The simulation behaves like a wave on a finite line ...
2
votes
1answer
662 views

How to model water flow with and without friction against other objects?

I am interested in modeling water flow including boundary flow (with friction) against other objects in the path of the water flow. I'm not a physicist but I am interested to learn the relevant ...
2
votes
1answer
1k views

Simulating Gravity in 3D Game?

Alright, I am writing a space simulator for a 3D game and I would like to implement gravity of objects into it. Is there a nice way to find a velocity vector which can be added to my engine output ...
2
votes
2answers
2k views

How to implement Heun's method to solve a 2nd order ODE? [closed]

I am trying to simulate a soft body object by having a collection of points connected by springs. I also want to have the object bounce on a plane. I have been able to implement Euler's method to make ...
2
votes
1answer
673 views

Software for simulating supersonic aerodynamics [closed]

Could you please suggest the software, where I can load my 3D model and see how it behave on various conditions (speed - preferably including supersonic, temperature, pressure)? Both free & ...
2
votes
1answer
63 views

What does the solid phase in a two-dimensional system with Lennard-Jones potential look like?

Consider a system of two dimensional particles interacting via Lennard-Jones pair potential: $$u(r) = 4[(\frac{1}{r^{12}})-(\frac{1}{r^{6}})]$$ where r is the distance between two particles. What does ...
2
votes
1answer
316 views

Simple QFT simulation - how to do it

I would like to write a simple QFT simulation for a free scalar field with a cubic interaction term. However, I got stuck a bit. I will try to describe what I think I understand. I want to have a ...
2
votes
2answers
141 views

Simulation of everyday life based on standard model [closed]

If I were to model the standard model, say on a super powered computer (which does not necessarily have to exist in the real world), would I get molecules, chemistry, life? I want to understand the ...
2
votes
1answer
97 views

Is the $\mu VE$ ensemble possible to formulate?

I have recently learned about ensembles in statistical mechanics, and I've seen multiple applications and interpretations of the EVN (microcanonical), TVN (canonical), $\mu$VT (grand canonical) and ...
2
votes
1answer
52 views

Ewald summation without repeating one particle periodically?

I need to perform an Ewald summation for a Brownian Dynamics simulation. In the normal Ewald summation procedure, all particles in the simulation box are periodically repeated in the neighbouring ...
2
votes
1answer
52 views

How does phonon scattering change the distribution function?

For a one-dimensional structure, we know that the modified distribution function has the following energy dependency in equilibrium: \begin{equation} Z(\varepsilon)\,f(\varepsilon) = \dfrac{N_\text{1D}...
2
votes
1answer
62 views

Reaction-diffusion. From kinetic parameters in 3D, can we infer their equivalent in 1D?

I am studying a reaction-diffusion system : $A+B ⇌_{k_{-}}^{k_{+}} C$. From experimental data I have all the kinetic parameters : diffusion coefficients $d$ and reaction rates $k_+$, $k_-$. Beside I ...
2
votes
1answer
151 views

Can two distinct events occur at precisely the same moment in time?

I am writing a simulation and am having difficulty resolving the order in which two distinct forces occur. The simulation will give different results if the forces are applied to the state in ...
2
votes
1answer
421 views

How do I simulate this simple quantum circuit in MATLAB

I want to simulate a circuit similar to the one below in MATLAB. If you have a state matrix describing the state of 3 qubits, I understand that you could apply a CNOT matrix tensored with and identity ...
2
votes
1answer
702 views

Dynamic simulation of surface tension [closed]

Is there any substantial body of work in physics on dynamically simulating effects of surface tension on liquids? The texts i found so far on fluid dynamics all seem to ignore surface tension, ...
2
votes
1answer
1k views

Rolling (without slipping) ball on a moving surface

I've been looking at examples of a ball rolling without slipping down an inclined surface. What happens if the incline angle changes as the ball is rolling? More precisely I've been trying to find ...
2
votes
1answer
140 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 ...
2
votes
2answers
463 views

Ideal 2D Unicycle Kinematics

A particle is connected to a massive wheel by a rigid rod. The wheel can roll without slipping on a horizontal surface. The particle is free to rotate around the centre of the wheel. I believe the ...
2
votes
0answers
31 views

Is there a form of rigid body dynamics that uses unit quaternions instead of Euler angles?

I’d like to know specifically about an elegant way of deriving a second derivative of an orientation quaternion from a torque and a moment of inertia matrix, if one is available. The straight forward,...
2
votes
0answers
36 views

What is the meaning of the Fourier Transform of the electric field of a well guided mode in a dielectric waveguide?

I have been studying waveguiding in dielectrics for a while now; however, I cannot understand the meaning of the Fourier transformed electric field. I will first give some background information. ...
2
votes
0answers
19 views

Derivation of generation of time between two subsequent particle enters into computational domain

I have problem with understanding derivation of one equation in following problem. You have 1D computational domain (it is not 1D but because it is symmetrical and we are watching only radial ...
2
votes
1answer
161 views

Missile-like trajectory calculation [closed]

First of all I want to let you know that I'm not a Physicist, I am a Video Game Developer. I can simulate physical and mathematical equations and can also use some built in physics. For example I ...
2
votes
0answers
25 views

Initial conditions for a massive objects to follow a path

Suppose I have a path, such as the one traced out by $r^2 = \cos(2\theta)$, and $n$ objects with mass $m$ at equidistant points on this path. What velocities should each object initially have in order ...
2
votes
0answers
53 views

Simulation of oscillator with frequency dependent damping

What would be the equation for the frequency dependent damping of harmonic oscillator? Is there something like: $$ \ddot{x}+2\delta\dot{x}+\omega_0^2x = \frac{F}{m}f(t) $$ with frequency dependent ...
2
votes
0answers
63 views

How to let Pythia to output the complete event record in LHEF or StDHep format?

I am currently using Pythia 6.4 to simulate some processes (I do not have the intention to upgrade to 8). Now, I need Pythia to output its event record in the format of LHEF or StDHeP. I accidently ...
2
votes
0answers
40 views

How to find the maximum torque to apply to a robot joint to have realistic movement? [closed]

I am a computer science student. I am trying to simulate a locomotion of a legged robot. The weight and dimensions of the robot: A rectangular torso has 1 Kg, (0.15m*0.3m*0.03m) (width * length * ...
2
votes
1answer
105 views

How to get the linear and angular acceleration generated by a force vector field?

I am working on a physics simulation and I have to calculate the angular acceleration in degrees per seconds squared around the point on the object located relatively to the center of a vector field (...