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Questions tagged [simulations]

The imitation of a real-world process using an analogous process that is easier to control and experiment with.

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Good Physics Engine Recommendations [closed]

Basically, I am looking for a precise physics engine I can use to run tests and tune a PID controller. The simulation is relatively simple: a small rocket with air brakes reaching a target altitude. ...
3 votes
1 answer
76 views

Ising Model magnetisation

I am simulating the 2D Ising Model and specifically looking at the time evolution of magnetisation $m$. Now, in the non-equilibrium state, magnetisation will grow as a power law with time $t$, if ...
Principia Mathematica's user avatar
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1 answer
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Accuracy of the Higuera-Cary Particle Pusher

UPDATE: 12 July 2024 This question has been answered. Also, I figured out the problem. One of the papers I was referencing (Ripperda et al.) had a typo, which was leading to the errors. The method is ...
Mohammad Yasir's user avatar
1 vote
1 answer
70 views

How do you solve instantaneous 3 body collisions

A few years ago I built myself a very basic python program that did some very basic collision mechanics between particles with a mass and velocity and it was helpful in learning a few things and ...
Max's user avatar
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Finite Difference Modeling of MOSFET Device

Does anyone know of any references for MOSFET modeling done using the Finite Difference Method that they could point me to? I understand the gist of the operation, namely using Poisson's equation to ...
Schoppe's user avatar
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1 vote
2 answers
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Vertical trajectory of a projectile with quadratic drag

I was wondering is there is an equation (or function) that can predict the apogee time and height of an object given its current acceleration and the usual constants ( mass, drag coefficient, cross ...
Frontiers Aerospace's user avatar
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23 views

Distribution of scattered photons in cone-beam computed tomography (CBCT)

I am using MCGPU to simulate photon transport in cone-beam computed tomography (CBCT). I ran an experiment, where a water cylinder containing spherical objects was irradiated. The simulation software ...
In the blind's user avatar
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31 views

Better equations for modeling and simulating a halo orbit?

I'm trying to model a halo orbit at low altitude (10m from surface). The satellite is using propulsion to trace the circular halo path. It looks like this "from the top" (the blue ball is ...
Nico Brenner's user avatar
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Method of inserting random numbers in the numerical calculation of mean-squared displacement for brownian particle

I am trying to plot Mean-Squared-Displacement for a passive Brownian particle. For that I'm using the discretized over-damped version of the Langevin equation as: $$x(i+1)=x(i)+\sqrt{\frac{2.k_BT.\...
QuestionTheAnswer's user avatar
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Topological illustration of spacetime dilation: which function should I use for isometric lines spacing?

Scientific popularization, when it comes to illustrating spacetime dilation around massive objects, often relies on the description of a two-dimensional square-grid, which can be regarded as a cross-...
olivierlambert's user avatar
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Best method for numerically solving Schrodinger equation for quantum tunneling w/ arbitrary potential

Goal: to compute accurate tunneling probabilities with an arbitrary barrier using numerical solutions to Schrodinger's equation. Main question: what method is best for generating a robust numerical ...
perchlorious's user avatar
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Favre Averaged Navier-Stokes equations

Consider the Navier-Stokes (NS) equation \begin{equation} \frac{\partial (\rho u_i)}{\partial t} + \frac{\partial (\rho u_i u_j)}{\partial x_j} = - \frac{\partial p}{\partial x_i} + \frac{\partial}...
Somestudent01's user avatar
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How does the Fermi level of graphene change if it is placed in a biased pn junction or in a plate capacitor?

I ran into a problem on which I can't really find any solutions in literature. I am looking at a Graphene sheet that is sandwiched in a biased pn junction (current flows orthogonal to the Graphene ...
kimcheez's user avatar
1 vote
1 answer
61 views

Numerical evaluation of gravitational light bending

I am looking into how light is being bent by objects of large masses with the intention of creating a numerical simulation of this (basically a ray tracer taking this phenomenon into account). I was ...
Pandicon's user avatar
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1 answer
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Is the drag coefficient linear with speed?

I made an RC-car and wanted to simulate the drag of it in Solidworks. But after I did my simulations I put my results in a graph, the drag is quadratic with speed but the drag coefficient $C_D$ is ...
BobTheBuilder's user avatar
1 vote
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Solving a system of equations involving Gaussian Integrals numerically [closed]

I wish to solve the following system of equations numerically in any software, I tried in Mathematica using the expectation functions, but I have a difficulty in understanding how to go about solving ...
rhombicosicodecahedron's user avatar
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What information we can obtain from total transverse energy and transverse momentum plots on particle physics

I am working on particle physics simulations and making some plots for which the purpose are not yet clear to me, as I am a novice in this field of study. To make my doubts clear, let's consider an ...
dumb physicist's user avatar
1 vote
2 answers
214 views

Resistively and Capacitively Shunted Junction (RCSJ) Model of Josephson Junction Numerical Solution

I'm trying to write a program to plot the I-V charateristics the josephson junction using a python program for some given values of resistance $R$, capacitance $C$, and critical current $I_0$, using ...
L lawliet's user avatar
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3 votes
2 answers
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Direct Current through a Copper Tube - Magnetic Field Question

Passing direct current through a straight copper wire generates the familiar "nested" cylinders of magnetic field strength along the length of the wire, decreasing in strength with distance. ...
GravityTim's user avatar
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Force-simulation for graph layout: How to avoid particle collapsing into a single point?

In a force-based graph-layout simulation using Barnes-Hut, what are the conditions for collapse? With collapse I mean multiple (or even all) nodes "collapsing" into a single point. Is there ...
skep's user avatar
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2 votes
1 answer
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Finite differencing for velocity cross terms?

In writing down the Navier-Stokes equation I have encountered two equations as follows: $$ 4\frac{\partial^2 v_x}{\partial x^2} + \frac{\partial^2 v_x}{\partial y^2} + 3\frac{\partial^2 v_y}{\partial ...
Raj Upadhyay's user avatar
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1 answer
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Is this the correct way to integrate orientation given torque and inertia tensor?

I am trying to develop a 3D rigid body simulation in C++ in which I had some conceptual doubts on how to integrate for orientation given the total torque applied to a rigid body, and it's initial ...
Kotetsu Chan's user avatar
3 votes
2 answers
172 views

About how to calculate observables in Quantum Monte Carlo with complex weights

I'm rewriting a Diagrammatic Quantum Monte Carlo algorithm following Werner, P., Oka, T., & Millis, A. J. (2009). Diagrammatic Monte Carlo simulation of nonequilibrium systems. Physical Review B, ...
pter26's user avatar
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Partition function expression from a discrete Hubbard-Stratonovich transformation

$\DeclareMathOperator{tr}{tr}$ This question is about a very specific (but very mysterious to me) detail. In some quantum Monte Carlo methods such as determinant QMC, the partition function $Z = \tr e^...
Banach space fan's user avatar
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Literature on the design of MQW for optoelectronics

I am looking for literature that teaches how to design a MQW for optoelectronic devices, particular a phase-shifter. I see these devices being used throughout the literature and they are quite ...
0 votes
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10 views

What are cellular automata qualitativly and what makes them different from other types of simulations?

Is there a qualitative difference between simulation for ex. movement of fluids via cellular automata rules and solving some diffusion equation via a discretization of a finite element method?
Sapiens's user avatar
  • 26
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Modeling an Electrolyzer System

In this study, the authors provide an equation for operating cell voltage: $V_{cell} = V_{rev} + V_{act} + V_{ohm}$, the sum of the reversible overvoltage, the activation overvoltage and the ohmic ...
Lucien Jaccon's user avatar
2 votes
0 answers
25 views

Modelling Mie Theory: Resources

I am currently working on simulating the scattering of light from nanoparticles. Are there any resources like books/ handouts/ videos that explain Mie Theory in depth?
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Boundary conditions for the stagnation point axisymmetric boundary layer equations

Good morning, I am trying to solve the Boundary Layer equations in the stagnation point in order to compute the stagnation point heat flux. In particular, the fluid is: -A continuum -In thermal and ...
Domenico Lanza's user avatar
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2 answers
80 views

$N$-body gravitation simulation in 2D and 3D

My question is quite general. I want to make $N$-body simulation, for example galactic dynamics, using $N$ stars. One possibility is to make these calculations in 2D using an inverse square law and ...
Rémy Galli's user avatar
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What will be the effect of density on relaxation time?

I am doing a Monte Carlo simulation of protein chains of various lengths. I change the densities of the simulation box. In my experiment, I found that density has no effect on relaxation time. Do you ...
user366312's user avatar
2 votes
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96 views

Numerical Relativity for Computer Scientists

What resources on numerical relativity/simulation would be suitable for a primarily theoretical computer science background [algorithms analysis, complexity theory, etc.]? Importantly, while I'm ...
-1 votes
1 answer
47 views

Determining particle position in a magnetic field given initial conditions [closed]

I am trying to create MATLAB code that will simulate a charged particle's path in a magnetic field. I have the user enter vectors for velocity and magnetic field, and then calculate the force vector. ...
tophatcollection's user avatar
9 votes
2 answers
298 views

About simple thermalization simulation: why the final distribution is not $E^{2}\exp[-E/T]$ but $E\exp[-E/T]$?

I made a simulation that studies the thermalization of massless particles, assuming isotropic and homogeneous spatial distribution, in 3 dimensions. Namely, I started with $N$ particles having random ...
Name YYY's user avatar
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1 vote
2 answers
277 views

Simulating the helium atom using the Schrödinger equation numerically?

I recently set up a numeric solver of the Schrödinger equation and can receive solutions for single-particle quantum mechanical problems. I became interested in simulating atoms, since there is a ...
Teo Tyrov's user avatar
1 vote
2 answers
150 views

Why is the $\cos^2$ envelope much more popular than $\cos^4$ to approximate the shape of a Gaussian laser pulse?

The Gaussian laser pulse $$ E(t) = E_0 e^{\frac{-2\ln 2}{\tau^2} t^2} \cos{\omega t} $$ (where $\tau$ is the intensity FWHM) is often troublesome in numerical simulations due to the infinite temporal ...
Neinstein's user avatar
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1 vote
1 answer
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Euclidean LQCD not on a lattice?

How much the idea of calculating Euclidean path integrals in LQCD is fundamentally tied to using formulations based on the discretized spacetime lattice? In computational approaches to quantum many-...
mavzolej's user avatar
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How do particle acquire thermal distribution?

Consider some toy N-body simulation: we start with a bunch of particles, discretize time, and simulate their interactions at each timestep. What numerical features should the simulation include to ...
Name YYY's user avatar
  • 8,901
6 votes
1 answer
498 views

Periodic boundary conditions: torus or infinite images?

I have a "philosophical" question regarding the use of periodic boundary conditions (PBD) in modeling and simulating systems of particles. Let us consider a system of $N$ classical particles ...
Michele Pellegrino's user avatar
0 votes
1 answer
69 views

How optimal launching angle is affected by mass?

I'm writing a code to calculate the maximum optimal angle for motion under linear drag and how it's affected by mass. It appears that for the most part this angle is independent of mass and not of ...
KatJ11's user avatar
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Apparent paradox: Mass flow rate decreases when I increase nozzle diameter

I do computational fluid dynamics for a living. I have recently been working on a case in which I simulate the flow (assumed 2D) of a compressible gas from a large chamber at pressure $P_1$, through a ...
K.defaoite's user avatar
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0 answers
26 views

How do I find numerical solutions to geodesics when given initial four-position, initial four-velocity and a metric? (for a ray tracer)

I've had the idea to try and code a ray tracer that obeys laws of special/general relativity. In order to predict the motion of objects in the scene I'd need to compute geodesics with a user specified ...
DesertedGecko15's user avatar
0 votes
1 answer
64 views

Math and Pseudo code paper on black hole binary simulation

I want to do a short practice to see how mass evolve space and how space curvature evolve mass distribution. Most of the GR simulations were rather complicated but I think the black hole binary had ...
0 votes
0 answers
18 views

Computing matter power spectrum using FFT

I have a 3-dimensional density field from a big N-body simulation, and I would like to compute the matter power spectrum $P(k)$ to see how it compares with the one observed by Planck etc. I know that ...
Frogfire's user avatar
  • 157
2 votes
1 answer
61 views

Is it possible to solve numerically the classical Yang-Mills for a generic source?

The classical Yang-Mills equation in the presence of a source $J^\nu(x)$ can be written as $$ \partial_\mu F^{\mu \nu} - i g [A_\mu, F^{\mu \nu}] = J^\nu (x), $$ where $F^{\mu \nu} = \partial^\mu A^\...
aruera's user avatar
  • 81
2 votes
0 answers
70 views

Initial condition of the millenium simulation

I would like to know the initial conditions used for the millenium simulation. More specifically, I would like to know the amplitude of the initial power spectrum $\mathcal{A}$. I have found the ...
konstle's user avatar
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1 vote
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94 views

Can the specific heat capacity in the Ising Model be negative?

Im working on a numerical method for the Ising model. I'm asked to calculate both the absolute magnetizetion and the specific heat capacity: $$c = \frac{\beta^2}{N} \left( \langle H^2 \rangle - \...
Gonzalo Chiva San Román's user avatar
1 vote
1 answer
104 views

Purcell Effect Without RWA

I am trying to simulate a coupled qubit-resonator system, and want to extract the Purcell decay rate of the qubit. For that, I initialise the qubit in state $\left|1\right>$ and fit the probability ...
AdRs's user avatar
  • 11
1 vote
0 answers
53 views

Constrained Lagrangian simulation. Fails depending on constraint definition [closed]

Introduction I want to simulate a robotic leg that has a closed kinematic chain. The analytical equation i derived are compared with a simulink multibody model. Initially, my simulation failed, and ...
MIKE PAPADAKIS's user avatar
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33 views

Calculating enthalpy of a solid as a function of temperature in Molecular Dynamics

I would like to get the enthalpy as a function of temperature for BCC lithium at zero pressure. I have performed a series of NVT simulations with 500 atoms using a Nose-Hoover thermostat at the ...
unkown's user avatar
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