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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Monte-Carlo hybridization-expansion observable defined with phases of the configurational weights

I am writing a quantum Monte Carlo algoritm (hybridization-expansion algorithm following this DOI: 10.1103/PhysRevB.79.035320), my configurations have weights $w_c = \phi_c |w_c|$ which are in ...
pter26'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 ...
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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
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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
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Bayesian update approach for quantum phase estimation query

Bayesian Estimation Approach for Quantum Phase Estimation: I am interested if my understanding of the iterative method for Bayesian quantum phase estimation is correct before producing computational ...
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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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Textbook recommendation for practical simulation of quantum systems

I'm hoping to find a textbook (or other type of reference) which discusses an introduction to simulating quantum systems with classical computers. To clarify, I'm interested in finding a resource that ...
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$N$-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 ...
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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 ...
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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 ...
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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. ...
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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 ...
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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
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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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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-...
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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
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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 ...
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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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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
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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 ...
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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 ...
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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^\...
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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 ...
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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
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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
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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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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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Determining a direction/projection/heading for an object in 3D space after it has been rotated

I hope this is a good place to find an answer. Regardless, Worldbuilding looks like a great forum to follow. I'm not a math wiz and I've tried to tackle this problem many times over the past decade or ...
edasac's user avatar
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Circle-circle collision, linear and angular momenta transfer

I am trying to simulate particle collisions in two dimensions (hydrated ions). I have found the formulas I need for the transfer of linear momentum. However, I kind of suspect that angular momentum of ...
Oleg Shevchenko's user avatar
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Simulating joints in rigid body physics

When simulating rigid body physics with joints(say unconstrained for simplicity) you normally have a constraint force binding the two objects together applied at the point of the joint. This results ...
FourierFlux's user avatar
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Carbon Nanotube Modeling

In various references, we see the construction of unit cells of carbon nanotubes from chiral and translational vectors. The chiral vector is given as: $$\vec C_h = n\vec a_1 + m\vec a_2$$ While the ...
benjamin_ee's user avatar
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Two-point-correlation in the 3D ising model

I am currently coding a 3D (Monte-Carlo) implementation of the Ising model, using the single spin-flip & Wolff algorithm. So far, I was able to calculate all the interesting observables, like $M$ ...
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Is there a way to simulate particle stopping stochastically, from a known $dE/dx$ curve?

I want to make a simulation of the stopping of Muons in liquid water that, instead of considering they lost exactly the amount of energy predicted by the $dE/dx$ curve at each iteration, sorts an ...
user2934303's user avatar
1 vote
1 answer
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What effect causes stars to be optically enlarged at the Einstein ring of a black hole?

Sadly i do not know what this effect is called, but it can be seen in some simulations; Credit to Alessandro Roussel The same effect can be seen on the Wiki page for black holes. For a while now, me ...
ErikHall's user avatar
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Physics of Landing a Rocket on a Specific Location [closed]

I have been working on a rocket model for the past year, and I have a question about the landing phase of the rocket flight. How do rockets, such as those from SpaceX, land on a specific location ...
Cheyon Vijayakumar's user avatar
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Setting up a wall with a slit inside the domain of a 2D wave being solved using the fourier-spectral method

The wave equation is given by: $$ \frac{\partial^2 u}{\partial t^2} = \alpha^2 \cdot \left( \frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} \right)$$ If we assume the solution to ...
Thenu Kaluarachchi's user avatar
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Free energy as a function of temperature over phase transition in molecular dynamics simulation

I've constructed a low density standard MD simulation (in Python), using the Lennard-Jones potential with an Andersen thermostat, of 10 particles in a box V = 10 $\times$ 10 $ \times$ 10 in the NVT ...
erkoo's user avatar
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How do I interpret the energy per particle in the Smoothed Particle Hydrodynamics (SPH) formulation?

I'm working on a basic Smoothed Particle Hydrodynamics simulation. I figured I would start with an ideal gas with equation of state $p=K\rho$. However, in calculating the SPH equations of motion, we ...
David's user avatar
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How to begin my journey into simulating light-matter interactions?

I am interested in simulating how light interacts with matter. For example, I want to create a 3D heatmap describing how light might scatter in some heterogenous material. But the more I dig into this ...
Jeff Boker's user avatar
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1 answer
78 views

Numerical simulations of standard model

Is standard model simulation a current and possible branch of research, or is it just lattice QCD?
Matteo's user avatar
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Can anyone suggest a calculation model for estimating the location of a dropped object falling from a height?

I'm trying to find models that allow me to calculate dropped objects, specifically, a model where I can consider lateral displacement due to wind force and vary the weight and resistance force of the ...
Francisco Lopez Chamberlain's user avatar
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Boundary crossing rate by independent Monte Carlo samples

I have written a Monte Carlo simulation, where I have a Brownian particle in a certain potential energy landscape. The particle moves in a squared 2d space (Simulation space) with periodic boundary ...
Polymers_physics_2000's user avatar
10 votes
1 answer
847 views

Explaining deviations in simulated to experimental Cs-137 spectrum

I'm comparing a Geant4 (Monte Carlo based) simulated gamma spectrum of $^{137}$Cs to my experimental results using a NaI(Tl) detector. I find good agreement between the two for the main features such ...
erkoo's user avatar
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1 answer
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How do you extrapolate frequency data from FDTD simulation time data?

Context: Im a PhD student who plans on doing research in theoretical plasmonics/nanophotonics, so I am studying up on understanding FDTD. I am having a bit of a conceptual issue regarding ...
ahrensaj's user avatar
2 votes
2 answers
108 views

Phase transition in Ising Model with local $\mathbb{Z}_2$ symmetry

I am studying the Ising model with a local $\mathbb{Z}_2$ gauge symmetry \begin{equation} \mathcal{H} = -\sum_{\text{plaquettes}} \sigma^z(\vec{x}, \vec{\mu})\sigma^z(\vec{x}+\vec{\mu}, \vec{\nu})\...
QFTheorist's user avatar
3 votes
2 answers
168 views

Theoretical calculation of Electron Paramagnetic Resonance (EPR) spectra

I have read that rather than holding the static magnetic field constant and varying the frequency of the oscillating field in Electron Paramagnetic Resonance/Electron Spin Resonance (EPR/ESR) ...
slithy_tove's user avatar
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What is the exhaust pressure of the Saturn V on the Apollo 11? [closed]

I am trying to write some code to simulate rocket launches, and I am doing a proof of concept using the Apollo 11 as a model, to fill my values. When calculating thrust I am using the equation: $$F = ...
owinius's user avatar
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1 vote
1 answer
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3D projectile motion simulator with drag is not constrained to a 2D plane

This is an example of the problem. I've set the initial velocities to be $(x,y,z) = (100,10,100)$ and the drag-coefficient and CS-area to be 1. As you can see the motion is not constrained to one ...
Thenu Kaluarachchi's user avatar

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