Questions tagged [simulations]

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Heat-bath algorithm of 2D XY model

Can anyone suggest any reference where the heat-bath algorithm for the classical 2D XY model has been discussed in detail. I have found references for the 3D Heisenberg model which can be exactly ...
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Is there a “standard” quantum simulator/animator for pedagogy?

I'm having a hard time finding animations for 1D or 2D square well, SHO, free particle with barriers, etc, that I'm sure are "trustworthy". It's the sort of thing I would do in python in my spare time ...
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3answers
48 views

How to calculate car engine acceleration and deceleration?

I'm trying to program some kind of car game in unity just for practice. So I want to start off with an engine that behaves normally, so I can then convert the engine's RPM into torque. Currently, I ...
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Software for 3D magnetic field simulation [on hold]

What are some user friendly softwares for making customized 3D models and doing magnetic field simulation. I have used FEMM for 2D models and it works great but is not capable of doing 3D models.
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Numerical simulations of Landau-Zener transition

I tried to use a midpoint method and numerically solve the Schrödinger equation for the original Landau-Zener (LZ) problem: a 2X2 Hamiltonian $\begin{pmatrix}\alpha t&\delta \\ \delta &-\alpha ...
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1answer
36 views

Is reversal of velocity always equivalent to reversal of time?

Let us imagine there is a container full of small particles which are allowed to collide with each other and the container walls (in 2D). If I initialise the system with given velocities and positions ...
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28 views

What methods can be used to interpolate values of a gradient?

Let's say I have a cubic mesh, the points of which I have obtained a vector value for, thus forming this discrete vector space of sort, I'm not really sure of the proper terminology for this which ...
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194 views

Does the fluctuations-dissipation theorem hold in active matter for macroscopic physical quantities?

I am trying to understand how the fluctuation–dissipation theorem applies to active matter. I simulated a system with motors which may consume energy from the environment to move and exert force on ...
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1answer
51 views

How to estimate the frictional losses of a car drivetrain?

I'm making a car driving video game which uses real engine torque curves, gear ratios and other physical attributes as parameters to simulate the motion of a specific car. The problem here is that I ...
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1answer
68 views

Modelling lunar motion in Python [closed]

I'm trying to solve the equations of motion of the Moon in the Moon-Sun-Earth system (equations 1139-1141 here:http://farside.ph.utexas.edu/teaching/336k/Newtonhtml/node130.html) My initial ...
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11 views

For vibrations in continuous beam, what is the unit of eigenvalue?

I have been solving a fourth order euler bernoulli differential equation to solve for vibrations of a continuous cantilever beam. When I verified for them using Comsol eigenvalue solver, it gives me ...
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1answer
40 views

Simplified general relativity simulation

I've been thinking how massive space battles might play out when vessels travel at significant portions of the speed of light (e.g. 0.01c-0.2c). I wondered if it was possible to simulate such actions ...
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Taking the derivative of the partition function describing a scalar QFT w.r.t. a constant

Premise: I know this question would be better suited to MathSE, but since it strongly concerns QFT, I'm confident I'll find a more exhaustive answer here. Consider a generic partition function $\...
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1answer
29 views

Why are the autocorrelations larger for the energy at the critical temperature?

Considering a simulation with the Swendsen-Wang algorithm for the 3-D cubic lattice I wanted to have a look at the auto-correlations, and expecting it to be quite small considering Swendsen-Wang is a ...
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53 views

What equations so I can model a “bouncing particle”? [duplicate]

What equations so I can model a "bouncing particle"? I've initially started with just $$f(x,y)=(x,\text{abs}(\sin(x)))$$ But I'm interested in doing gravity and speed changes and stuff. So how to ...
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48 views

Symplectic time-integrator for Fokker-Planck equation

Is there a way to use a symplectic time-integrator for the numerical solution Fokker-Planck equation of the form: $$\partial_{t}p = -\nabla \cdot (\underline{v}p - D\nabla p)~?$$ where $p = p(\...
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2answers
31 views

How is the magnetic flux density inside a current tube affected by an inner wire?

Background to problem Conventional wisdom informs that the magnetic flux density inside a tube carrying current is zero everywhere. Pictorially this is represented by this finite element analysis (...
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40 views

Physics Graphic Simulations

I am interested in modeling physics using graphics simulations. I took a python course with CS majors and one of the assignments was to simulate a planet orbiting a star. That being said, I was ...
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How do I calculate the pressure on the walls of my MD simulation?

So I've built a simulation in vpython where I have multiple hard balls that collide with each other and with the walls of the cube I've placed them in. I then replaced the values for their radius and ...
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1answer
38 views

Numerical calculation of skyrmion number

I'm having trouble finding a numerical method to calculate the skyrmion number for a certain system. I want to calculate $$ n = \frac{1}{4\pi}\int \textbf{M} \cdot \left( \frac{\partial \textbf{M}}{\...
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43 views

$<P_T>$ distribution as function of PL

I have a conceptual problem when working with some Monte Carlo generated data. I have to simulate the $P_T$ and $P_L$ distribution for $N$ particles through Monte Carlo methods as follows: $$\theta \...
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1answer
17 views

Obtain element boundary forces in Finite Element Method

Suppose that we have a rectangular domain discretized using 16 voxels (4x4 voxels) and I apply a Finite Element Analysis with arbitrary boundary conditions in the domain. As a result, I obtain the ...
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2answers
39 views

What are the possible method to simulate the dynamics of rigid bodies in simulation? [closed]

I just want to know the name of the methods, the simulation physicist uses to simulate the dynamics of rigid bodies. Eg. Impulse Based Dynamics developed by Mirtich
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FDTD simulations for metamaterials and complex refractive index

I have designed a working FDTD code to simulate electromagnetic wave propagation using Yee's algorithm. I have been able to place materials such as glass slabs, etc which have positive and real ...
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1answer
25 views

Deriving the form of radial distribution function in molecular dynamic simulation?

I am trying to derive the equation 8.16 in the attached image from the definition of the radial distribution function. However, I am unable to derive it with proper constants of $\frac{2}{N(N-1)}$ My ...
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Macroscopic hydrodynamics, is there a fluid “vacuum” force?

Background I was looking at the following simulated fish movement article and how the physics could be improved (ie, made more realistic) with out a huge impact on performance. It looks like they ...
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2answers
133 views

How do I simulate an ideal gas?

I wish to write a simple simulation of an ideal gas, but my maths and how I should have a model based the equation isn't quite up to it. I need some help understanding the relationship between ...
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0answers
13 views

Compute SH and SV component in shear wave (accoustics wave propagation)

I'm reading this guy right now. Basically I need to add to a ray tracing simulation components for shear waves propagation (in the acoustic/VHF range). Essentially this is related to section 1.2 of ...
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22 views

Swap protocol in parallel tempering MCMC simulations

Consider a parallel-tempering Markov-Chain Monte Carlo (MCMC) simulation of a system, with inverse temperatures $\beta_1 < \cdots < \beta_N$ and energies $E_1, \cdots, E_N$. If there are two ...
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1answer
29 views

Calculate the kinetic friction velocity vector from the kinetic friction force in a simulation

I am doing (programming) a simple kinematic 2D simulation on blocks. The idea is that the block will have a force applied. 1) From the force and mass I calculate the the acceleration vector (will ...
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34 views

Fluid simulations on spherical coordinate grid: How to handle $\theta=0$ axis?

I am working on a fluid simulation code written in spherical coords. Whoever wrote the original didn't do a great job with the boundary conditions at $\theta=0$ and $\theta=\pi$ axes. My task is to "...
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54 views

How to calculate the autocorrelation function of magnetic susceptibility for the Ising model?

In the paper Wolff U. 1989. Physics Letters B. 228(3):379–82, the autocorrelation time of susceptibility, $\tau_\chi$ was calculated, but the way to do so was not clearly explained in the paper. To ...
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2answers
34 views

What is the difference between the differents lennard-jones parameters

I know different lennard jones potentials 12-6, 9-6, 9-3. I think the difference between them is the way they describe long-range interactions,but when I use each of them? Thank you in advance
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1answer
23 views

Why neutrons production is falling along beam axis in proton/nucleus collisions?

I'm studying a case where I simulate a protons beam (~70 MeV) on a spherical target composed of light nuclei such as carbon and oxygen. I'm looking for the angular distribution of neutrons produced by ...
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0answers
117 views

Is constant invariability needed in simulation of equations of motion

Let's take for example the equation of motion for a pendulum. $$\ddot{\theta} = \frac{g}{L}sin(\theta)$$ Discretizing gets us $$y_{i + 1} = \left(\frac{g}{L}sin(\theta)\right)h^2 - y_{i - 1} + 2y_i$...
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Absence of fermion sign problem at half filling

It is said that in the hubbard model, at $\mu = 0$ , there is no sign problem. I do not see why $\mu = 0$ is necessary in the above argument? For the hubbard hamiltonian, \begin{aligned} H=-t & \...
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1answer
120 views

Universe simulation

Is it theoretically possible to simulate the universe? I know that some philosophical theories say that our universe is a computer simulation, but is this feasible? Would it ever be possible for a ...
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0answers
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Magnetic susceptibility vs Monte Carlo step

I have some difficulties in understanding how to compute the magnetic susceptibility from a Monte Carlo simulation of the Ising model. I know that it is related to the magnetisation of the system by $\...
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0answers
32 views

How to do Weierstrass-transform in MATLAB? [closed]

I have a diagonalization problem. I have the eigenstates correctly, and I want to do a Gaussian-smearing (Weierstrass-transform?) on them. So I have the wave functions ($\Psi$, $1\times N$ vectors), ...
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How to implement SHAKE algorithm in molecular dynamics for simple systems like linear chain molecule?

3 spherical beads are connected by stiff bond and forms a rod like shape. I am able to perform the Molecular dynamics of them with taking a spring force and a bending force in between them. But for a ...
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2answers
54 views

Evaluating the quality of Monte Carlo simulations for 3D Ising model

Suppose I have developed a new Monte Carlo method, and I plan to test this method on studying the magnetization of a 3D Ising model at some non-zero temperature $T$. The coupling is nearest neighbor, ...
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0answers
9 views

Lens simulator with geometrical optics [duplicate]

I'm looking for a lens simulator to see rays from geometrical optics, possibly easy to use. For now I'm playing with OpticalRayTracer that works perfectly for a preliminary simulation. I would like a ...
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2answers
71 views

Simulation software to solve high school level mechanics problems

I'm a physics teacher and I would like to find a simulation software that could be used to give exact numerical answers to high school level problems in Newtonian mechanics. I want the students to ...
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0answers
35 views

Amount of particle collisions depending on entropy

I'm doing a very simple simulation of random particles. Simple mechanics, elastic collisions. (The simulation is based on a next-event time progression.) When I count the number of particle particle ...
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0answers
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Metropolis method under the Gand Canonical Ensemble

I am writing code to simulate Langmuir adsorption using Metropolis method under the Gand Canoninal Ensemble. Aided by the Wikipedia Article, I derived the corresponding equation, proposed a sample ...
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0answers
31 views

Davis formula application

So I stumbled upon the Davis formula for trains while doing some researches about my project but I don't know how to apply it (programmatically) : Let's say for example this variant : $$R'=1.3+\frac{...
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1answer
97 views

Train Physics Simulation

It's my first time asking here so bear with me. I'm a computer scientist, and I'm working on a train simulator project. I'm having quite a difficult time understanding all the physics and formulas ...
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1answer
35 views

Magnetic susceptibility error by binning Monte Carlo

I am studying the 2D Ising model using Monte Carlo simulations and I have learned the binning (or batching) method for the error statistical analysis. Following this discussion https://books.google.it/...
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1answer
27 views

What would be a correct/natural approximation for the curve of bended materials?

Would it be a cubic/quadratic Bezier curve? Or perhaps (part of an) ellipse? I am a computer science student who is working on a physics engine using realistic materials, meaning I would like for ...
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1answer
64 views

Simple heater (radiation) model for PID constants tuning

I've searched around a lot and maybe I just don't know what exactly to search (and even ask here) for, but I'd like to create a simple model/function of a heater dissipating heat to surrounding air, ...