Questions tagged [simulations]

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Trying to determine physically meaningful initial conditions for test particle around a Kerr black hole

I am working on some code for a test particle orbiting a Kerr black hole. I am trying to determine what the initial $ \frac{d t}{d\tau} $ would be. On Wikipedia https://en.wikipedia.org/wiki/...
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Does Hubble constant $H$ change with time in $N$-body simulations?

In $N$-body simulations, there is a Hubble constant $H$ in equation of motion. when we integrate the equation of motion, does this constant H also change with the simulation time? or it is just a ...
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Input field conditions for beam gaussian propagation

I am trying to calculate a beam propagating through a lens with focal length $f_0$ and a gaussian shape perpendicular to the beam propagation axis. For that I use the equation $$\partial_zE=\frac{i}{...
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1answer
21 views

Lorenz System in reference to Astrophysics / Planetary orbits

From my research I have found that there are a system of ordinary differential equations for atmospheric convection. What I am seeking are any Lorenz equations that apply to any areas of Astrophysics ...
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1answer
66 views

Velocity driven Poiseuille flow using the incompressible lattice Boltzmann method

My goal here is to develop a Poiseuille flow in a channel, using constant pressure and zero velocity as initial conditions. From what I have read, people seem to be mostly using pressure-driven, or ...
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1answer
37 views

Fluctuating magnetization curve in ising model

I am working on Metropolis-Montecarlo algorithm for 2D Ising model in python partly based on this document. I ran the simulation for 100 times on a 25 x 25 lattice with external magnetic field B = 0. ...
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1answer
27 views

Simulating a fan speed given power applied to it over time [closed]

I am driving a fan using a micro-controller. I want to test the micro-controller code without having fans physically attached to it so I thought I would model one programmatically. I want to model a ...
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1answer
50 views

Predicting orbital trajectory of an object

I'm new here, I'm not a physics student, I'm a programmer and a soon to be computer science student (I come in peace). I'm developing a space simulation thing and I need your help. I know the ...
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1answer
59 views

Extension of classical Liouville operator

Let us consider a classical Hamiltonian system described by the Hamiltonian \begin{equation} H(q,p) =\frac{p^2}{2m}+V(q) \end{equation} where we stick to the case of single particle for simplicity. I ...
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2answers
53 views

Simulation of Feynman path integral in literature

Can someone provide me a numerical simulation of Feynman path integral? Where the contribution of each path is added individually so that I can understand how much do the paths outside the light cone ...
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1answer
55 views

Accounting for expansion in $N$-Body gravitational simulations

I have an $N$-Body simulation for the evolution of the universe. It uses a hybrid Tree Particle-Mesh scheme to compute the forces. The tree code used Newtons law of gravity: $$\textbf{F}_i = -G \sum_{...
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1answer
59 views

Understanding the equations of motion for the Polyakov action in string theory

I want to make a small numerical simulation of how strings in theory move under their equations of motion but I'm getting stuck at implementing the constraints. The Polyakov action reads $$S=-\frac 1{...
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Is there a good physical simulation software (mainly refers to the rigid body mechanics simulation)? [duplicate]

I want to simulate the examples in theoretical mechanics and analytical mechanics. I need a mechanical simulation software, which can customize the force field, spring, rigid body, connecting member ...
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1answer
55 views

Phase-ordering dynamics: numerical solution of the Mazenko equation in $D=2$

I'm considering the Mazenko equation as it's written in https://doi.org/10.1103/PhysRevB.46.10594 (eq. 7) \begin{equation} \label{a} f''+\left(\frac{1}{x}+\frac x 4 \right)f'+\frac \lambda \pi \,\tan\...
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1answer
52 views

Chaotic Hamiltonian system poincare surfaces depend on the integrator

First question on StackOverflow so go easy on me. I have a Hamiltonian system that consists on the following Hamiltonian: $H(p,x;\textbf{P,X})=\frac{p^2}{2m}-a\frac{x^2}{2}+b\frac{x^4}{4}+x\sum_{n=1}^...
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1answer
49 views

Variance of Simulated Langevin Equation

I simulated (by Matlab) the Langevin equation for optical-trapped particle in very short time "steps" And I got this white noise figure.. The question is how I can calculate the variance (or in ...
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Simulating Thin Film Bulk Acoustic Resonator based on Lateral Field Excitation on COMSOL

I am a beginner to COMSOL and I have to simulate a Thin Film Bulk Acoustic Resonator based on Lateral Field Excitation on COMSOL. Can someone give me a detailed approach on how should I do the ...
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16 views

X-Ray simulation software suggestions

Asking here as a 'specialist' location, as opposed to the regular 'software suggestion'. I am looking to find a way to generate synthetic x-rays of a 3D model. The closest I've found (Free) was http:/...
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27 views

How to properly implement Newton Cooling in FTCS Heat Equation

I am attempting to model the temperature in 2D plate using the FTCS scheme for the heat equation. The plate is finite, and discretized squarely. I do not want the temperature fixed at the edges. ...
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1answer
59 views

Simulated gravity equations

I'm working on a game that'll have a (I probably naively believe) simple gravity component and am looking for a couple of equations for the task. Given 1) a ball rolling from point A down (or up) a ...
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44 views

“Unnatural” Hamiltonian systems from a statistician's perspective

I would like to learn more about "unnatural" Hamiltonian systems, that is, systems whose energies cannot be written as $$H(p,q) = K(q) + U(p).$$ I have seen the term "natural" applied to systems ...
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What is the difference between the rot_star and nrotstar class in LORENE (Numerical Relativity)

Im doing my final grade work about neutron stars simulations. I need to compute some simulations for different EoS. In the classes, I find two different classes: nrotstar-> I think the n means ...
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1answer
37 views

Generating random change in photon frequency $\Delta \nu$ from angle-averaged isotropic redistribution function

I am implementing the Monte Carlo Simulation Code for the case of photons being scattered by electrons. The paper I'm referring (Hillier 1991, Appendix B) suggests that after each scattering, the ...
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1answer
2k views

How do I simulate an atom?

Let us assume I wish to simulate a Helium atom, since there does not exist a closed-form solution. However, I presume I would need to simulate the time-dependent Schrodinger wave equation. I would ...
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Is simulating 3D brownian motion in axially symmetrical 2D sensible?

I'm writing a Monte Carlo particle trajectory simulation program. There are fluid forces like the Stokes drag force involved, as well as Brownian motion. For runtime reasons, the program should be ...
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1answer
49 views

Determination of the thermal resistance of a molding tool with cooling channel

This is a section of cooling channels in injection moulding tools. I have tried to calculate the thermal resistance in this section with 2 methods, one analytical and one numerical. analytical ...
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27 views

Heisenberg Hamiltonian: Energy per site on the triangular lattice

I want to find the energy per site for the Heisenberg Model with 3D spin-vectors $\bf S_i$ on a 2D triangular lattice and nearest neighbor interactions. I have a Monte-Carlo Simulation (green +) and I'...
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1answer
68 views

Simulate Background Gamma Radiation for Localization [closed]

I'm working on a gamma radiation source localization project. The gamma radiation measurement model is: $\lambda_k = \frac{I}{(x_s - x_k)^2 + (y_s - x_y)^2} +\lambda_b$. Where $\lambda_k$ is the $...
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1answer
60 views

Building realistic simulation using differential equations [closed]

I am building simulation using differential equations to model the motion of a damped vertical spring-mass system. I wish to use this simulation to extract data. For example, I am trying to find the ...
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1answer
55 views

Molecular simulations of proteins: how good an approximation is electrostatics?

This question has to do with molecular dynamics simulation of molecules, especially proteins, using software such as GROMACS. This type of software uses empirical force fields (eg AMBER) and some ...
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30 views

Numeric simulation of light propagation throug micropores in water

I am interested in the simulation of the propagation of light through the surface of the silicon diatom frustule. Could you recommend me any free program that allow to perform such simulation? That is,...
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How molecular simulation could be used to determine frequency-dependent electrical susceptibility?

Are there any frequency regions inaccessible to simulation? Do certain frequency regions require special methods?
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How to calculate the entropy trace of a system where the microstate number may not be analytically found?

I have a simulation that allocates utility values to agents on a grid. These utility values govern their ability to subsequently perform a series of moves on the grid in a simulation. These values are ...
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101 views

Using MATLAB to simulate the Ising Model [closed]

I am using MATLAB to simulate a 1D Ising Chain. I am running into an issue where when trying to find heat capacity, my system has a tremendous amount of noise. I'll post my code and an image of the ...
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26 views

Help with diagonalizing a BdG Hamiltonian

I am working on a simulation which diagonalizes a BdG Hamiltonian; let's start with one of the form: $$\hat{H}=-t\sum_{<r,r'>,\sigma}\hat{c}^\dagger_{r\sigma}\hat{c}_{r'\sigma}+\sum_{r}\Big(\...
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1answer
58 views

Computational Physics Books [duplicate]

I'm really interested on how to simulate physical systems that I'm currently studying as a first year student at University. For example, how to replicate a Pendulum using different algorithms (Euler'...
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2answers
58 views

What is the easiest way to do basic mechanical simulations? [closed]

I am interested in doing basic mechanical simulations, such as experimenting with the brachistochrone problem (path of quickest descent) and the motion of point particles under the influence of ...
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protein simulation question

for simulating a globular protein that has a diameter of 100Åin a cubic box of side length L, water adjacent to the protein is very different from bulk water. I want the periodic replicas of the ...
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27 views

Bond Orientational Correlation Function - how exactly to calculate

I have a question about this article. I am trying to compute the bond order correlation function, $g_6$. It is defined based on the bond order parameter: $$\psi_6(r_i) = \frac{1}{N}\sum_{j}^{}{\exp[...
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1answer
86 views

How to test the physical accuracy of a finite difference solution to Laplace equation?

I just wrote a program that computes the potential field inside a Penning-Malmberg trap; my end goal is to simulate plasma inside this trap. First I need to make sure my potential field across the ...
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17 views

Validity of the Poisson equation in high-frequency device simulations

Many device simulators use the quasi-stationary Poisson equation \begin{equation} \nabla\cdot(\epsilon(\vec{r})\nabla\varphi(\vec{r})) = -\rho(\vec{r}) \end{equation} for calculation of the ...
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1answer
30 views

Taking the speed of light into account during n-body simulation

Currently, I compute the force between two gravitational interacting particles in a simulation with $n$ bodies according to $$F = G\frac{m_1m_2}{r^2}.$$ Doing this, however, assumes that all bodies ...
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26 views

How to simulate the formation of chemical bonds by calculating electrodynamic forces?

I had the idea recently that if the interactions between atoms could be calculated, that a large enough computer could simulate biological processes. What would I need to know to simulate something ...
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49 views

How to implement periodic boundary conditions in a $n$-body simulation

I implemented a vanilla $n$-body simulation for educational purposes. As was to be expected, a point cloud collapses towards the middle of the simulation if the particles have zero initial velocity. ...
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2answers
90 views

What does it mean to simulate a quantum system?

What does it mean by simulating quantum system? Can I simulate Young's double slit experiment with a quantum computer? If yes, won't it violate no-cloning theorem?
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Intensity increase in Monte Carlo radiative transfer simulations (in case of Rayleigh scattering)?

I came across something weird (at least for me) while looking at the Müller matrix for Rayleigh-scattering. If I see it correctly, for some scattering angles, it can actually increase the intensity up ...
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1answer
102 views

Why a quantum computer simulation is not a quantum computer?

Is it because the inability to generate true random numbers (I dont think so) in the host machine or something else? My understanding is that the ability to emulate a quantum computer in a ...
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59 views

Physics Simulation of a Simple Pendulum with Drag Forces

I am working on simulating a simple pendulum with present drag forces. My task is to use numerical methods (I am using Verlet integrator) to estimate the angle as a function of time, as well as the ...
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1answer
646 views

Rotational motion integration (Rigid body dynamics)

I am trying to integrate the rotational motion of a rigid body (a set of N point masses) $\textbf{in the inertial frame}$, but my results seem totally wrong. What of the following steps could be wrong?...
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1answer
32 views

Inserting Wind effects on a rocket trajectory simulator

I`m more used to the math.stackexchange so i really don't know how much information about my problem i should provide, if it is not enough i'll add more. So, basically i already have a 6DOF ...

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