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Questions tagged [simulations]

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2
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0answers
26 views

Stability criterion for leapfrog in relativistic physics

I am doing a 2D MD simulations of charge carriers in graphene using the Leapfrog algorithm. I am trying to prove that, in some specific cases (when distance between particles is small), the method is ...
0
votes
0answers
24 views

Ball collison in 2D in Java [on hold]

For a course in my university the final project is basically making a program with java that simulates some particles moving in a 2D frame.We should consider that the collision may not be completely ...
2
votes
1answer
31 views

What is this secondary transition in the simulation of the Ising model?

Here, the horizontal axis is the strength of the ambient magnetic field. The Hamiltonian I used is $$H = -h\sum_i \sigma_i - J\sum_{\langle i \, j \rangle}\sigma_i\sigma_j.$$ The horizontal axis is $h$...
0
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0answers
25 views

DMRG for Heisenberg spin chain [closed]

I am learning DMRG. I am writing a DMRG code of Heisenberg chain, which has following Hamiltonian $$H=\sum_i S_i\cdot S_{i+1}$$ The algorithm for infinite DMRG is following: Build left and right ...
-1
votes
1answer
41 views

Mimicking the behavior of a current loop using a finite number of infinitely small sources [closed]

I am attempting to model the field produced by either a loop of current, or a magnetic moment. In either case I am assuming that the distances I care about are sufficiently far from the source to not ...
1
vote
0answers
51 views

Wolff cluster update in Monte Carlo simulation - at critical temperature [closed]

A general question to the Monte Carlo experts. When I use Wolff algorithm for global updates, say for Ising 2d, I always flip at least one spin (the initial random spin in the cluster). So, near the ...
0
votes
0answers
24 views

Is there a mass spectrometer software that can measure the mass of a hydrogen atom [duplicate]

For a school project I need to measure the mass of a hydrogen atom either as a lab experiment or with a computer simulation. Since I don't have the appropriate equipment for the experiment, does ...
0
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0answers
42 views

Is there a mass spectrometer software that can measure the mass of a proton

I spent a lot of hours looking for mass spectrometer software (or Cathode-ray simulator) that can measure the mass of a proton or any sub atomic particle. Until now I only found software that work on ...
10
votes
2answers
280 views

How can one obtain the metric tensor numerically?

I am self-studying General Relativity. Is there a method for obtaining the metric tensor exterior to a specified mass distribution numerically? In the simplest case of a spherical mass this should ...
0
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0answers
7 views

Resonant frequency of Split Ring Resonator (SRR)

I am working on circular and square split ring resonator design as part of my thesis. I wrote a Matlab code to calculate SRR resonant frequency but I am not getting the same answer of any published ...
0
votes
1answer
46 views

Screening of a coulomb-like potential

Imagine that we have a potential in the form of: $U(r) \propto \frac{1}{r^n}$ in a 2D system, with the high concentration of particles interacting with the above potential. How do you find the ...
0
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1answer
42 views

Ising magnetization in metropolis

I am working on the Metropolis-Montercarlo algorithm for the square lattice ising 2D. Im running the simulations for a given lattice size, running from low temperature to high temperature, and ...
0
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0answers
24 views

Entropy in the Klimontovich Picture of Kinetic Theory

In the Klimontovich picture of kinetic theory, a classical $N$-body system is fully specified by the phase-space distribution $$ \rho(\vec X,t) = \sum_{i=1}^N\delta[\vec X-\vec X_i(t)] , $$ where $\...
1
vote
0answers
51 views

Negative Eigenvalues of the Hessian

I am calculating the eigenvalues of the Hessian for a ferromagnetic system. My energy has the zeeman term, a nearest neighbor exchange term, and a dipole-dipole term. I create the hessian where my ...
1
vote
1answer
54 views

Metropolis Monte Carlo Phase Transition for small systems

Metropolis Monte Carlo simulation for the argon liquid fails to reproduce correctly the pressure-temperature isotherm from the point of liquid-vapour coexistence: Why such a phenomenon appears ? The ...
3
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4answers
140 views

Is it possible to draw a potential landscape for this system?

Attention: The question was modified for numerical solution. (see Update 2) I have the following system of differential equations: \begin{align} \dot x & = -x+F(a\,y+b),\\ \dot y & = -y +F(...
1
vote
0answers
66 views

Why does conservation of energy appear to be violated? [closed]

I am currently working on a rigid body simulator. Before getting proper collision and rotations working, I decided to simulate the collision of spheres as axis-aligned objects. The simulation works ...
1
vote
1answer
86 views

Brownian dynamics simulations in confined geometries [closed]

I am currently trying to implement a 2D Brownian dynamics simulation in confined geometries (corrugated channels, of the form $A\cos(2 \pi x) \ + B\ $ in this case). The concept is to compute the ...
6
votes
4answers
152 views

Is there a name for this wave effect?

So I was using this wave simulation (https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html) when this happened; using the settings: Oscillator, High tension, no damping. ...
1
vote
1answer
42 views

Periodic autocorrelation function for Ising model?

I am trying to calculate the autocorrelation time for a 2-D Ising model Monte Carlo simulation. As the autocorrelation function, I am using $$\chi (t) = \frac{1}{t_{max}-t} \sum_{t' = 0}^{t_{max}-t-1} ...
0
votes
1answer
35 views

Multiparticle simulation and Velocity Verlet Algorithm

The Velocity Verlet algorithm requires using an updated particle acceleration to compute and updated velocity. If that acceleration depends on a force that depends on distance to the other particles, ...
-1
votes
0answers
49 views

Position based dynamics: explosive collision constraint velocities when timestep is small

I'm studying PBD algorithms and can't figure out the solution to a particular problem. Here is the pseudocode for a typical PBD solver loop: For normal equality constraints (distance constraints ...
2
votes
1answer
40 views

Solar System Position and Velocity data

I'm trying to create an nbody simulator and to test it I'd like some real world data. A good test would be the solar system. I've come across the JPL Horizons software but if cant seem to figure out ...
1
vote
1answer
95 views

Weird results of Monte Carlo simulation

I'm simulating the 3D Ising Model using the Wolff update algorithm. I am using the Mersenne Twister RNG. When the lattice size is $L = 50$, the specific heat curve looks very weird!! I want to ...
2
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0answers
72 views

Is there an alternative to SIMION?

Is anyone aware of an alternative, possibly open-source, to the SIMION software? From their website: SIMION is a particle optics simulation software primarily used to calculate electric fields ...
0
votes
1answer
67 views

Implementing a Monte Carlo Simulation for the Gaussian Model

I want to implement a Monte Carlo simulation of the 1D Gaussian Model (the continuous generalisation of the Ising Model). That is the statistical mechanical model with the following Hamiltonian: $$ H ...
0
votes
1answer
23 views

Can you use HLvL scheme to solve these quations?

I successfully used HLvL scheme (https://epubs.siam.org/doi/10.1137/1025002) to numerically solve set of equations of this type: $\frac{\partial u}{\partial t} + \frac{\partial f(u)}{\partial x} = 0$...
3
votes
1answer
126 views

The acceleration of the particles by finite difference [closed]

I would like to approximate the acceleration of a molecular dynamics system. I'm following an online tutorial to solve a set of equations for molecular dynamics. I can use $F=ma$ to calculate the ...
1
vote
1answer
89 views

Phase transition in a 2D classical Heisenberg model Monte Carlo simulation

I have performed a Monte Carlo simulation of the classical Heisenberg model for a simple 2D square lattice. But I obtain some strange results. In fact, there is clearly a phase transition and a ...
1
vote
2answers
60 views

Modeling water flow between two tanks

To familiarize myself with concepts from my system modeling class, I have posed myself the following problem, which I have been struggling with for a good while now. I am an absolute physics beginner, ...
-1
votes
2answers
41 views

Lateral acceleration to angle [closed]

I am doing a 2D simulation in discrete steps of a vehicle. The vehicle will desire a certain lateral acc. at any given timestep. So I would like to know the delta angle of the velocity vector after ...
1
vote
1answer
50 views

Why do we need large system in Monte Carlo simulations?

Why do we need to simulate large systems (especially in spin systems)? Is it just a better representation of the real behaviur of magnetic systems? Is there an instability of the finite system with ...
1
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0answers
32 views

Impurity diffusion from solid to air

I have to put up a simple 1D model to simulate the diffusion of impurities in a bulk material, to a top thin layer made of another material, and compare it to experimental data. I first did it with ...
2
votes
1answer
37 views

Simulating electrostatics in discrete time steps

I am trying to simulate the motion of several charged particles that are free to move around but have repulsive forces between each other. These may be 10 electrons moving around causing an ...
-1
votes
1answer
59 views

Analytic and numerical integration of the rocket equation yield different results [closed]

Background The mass of a rocket as a function of time is: $$ m = m_0 - \dot m t$$ Where $m_0 $ is the initial mass of the rocket and $\dot m$ is the mass flow rate. At a certain time all the fuel has ...
1
vote
1answer
80 views

Why are simulations like Monte Carlo or Metropolis studied for Ising Models when 1d and 2d case have analytical solutions?

I know that absolute analytical solutions exist for the 1d and 2d case but need some intuition as to why these simulation algorithms are used and how do we benefit from them ?
1
vote
1answer
36 views

Integrating Carnahan-Starling Pressure

Given the Carnahan-Starling equation of state for a solution of hard-spheres, $$ Z = \frac{P}{\rho k_BT} = \frac{1 + \eta + \eta^2 - \eta^3}{(1-\eta)^3}$$ where $\rho = N/V$ is the number density and ...
4
votes
1answer
60 views

Is it possible to simulate Diffuse Interstellar Bands?

I recently saw this YouTube video about Diffuse Interstellar Bands (DIB) which describes the confirmation of a buckminsterfullerene as the source of one DIB. Is it possible to simulate how a proposed ...
1
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0answers
31 views

What type of potential is suitable for ion bombardment in Molecular Dynamics?

I would like to study ion bombardment on targets with molecular dynamics, especially on oxides. So far I ran conclusive tests with Lennard-Jones potentials, but I would like to obtain better ...
0
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0answers
12 views

Simulation of a rotor with a shroud

I am doing a simulation of a rotor with a shroud to know about the effects of the shroud to the aerodynamcis performance of the rotor. I am using Fluent to do this project. For me, there are two ways ...
0
votes
1answer
37 views

How would one compute the path of an particle's motion from forces defined in different frames of reference?

I'm trying to write a computer program to render and play-back the path of a particle existing in 2D space given all forces acting on said particle. This is relatively easy to do if all forces are ...
0
votes
1answer
24 views

How to determine the off-diagonal term of magnetic susceptibility tensor from fluctations?

I have run a Monte Carlo simulation of the classical Heisenberg model (in the future I am planning to add other interaction terms). I would like to extract information about the property of the system ...
5
votes
2answers
278 views

How can I include variable particle number in a Brownian dynamics simulation?

I programmed a Brownian dynamics simulation in two dimensions. (Coarse-grained proteins on surfaces with interaction potentials i.e. patchy particles.) Now I want to allow particles to leave or enter ...
1
vote
0answers
50 views

Proof that, for any force law in Newtonian Mechanics, if a planet gets closer and then further from its star repeatedly, the orbit is bounded

I have run simulations of planetary motion using various force laws that are functions of distance $f(r)$, including but not limited to $$f(r)=\frac{1}{r^2}$$ $$f(r)=\sin(r)$$ $$f(r)=r!$$ $$f(r)=\...
0
votes
1answer
30 views

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same “dimensionality” and unit?

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same "dimensionality" and unit? $W/mk$ is thermal conductivity. $W/m^2$ is heat flow density related to one unit. $W/m^2k$ is heat transfer ...
-5
votes
2answers
63 views

Can we simulate whole universe with infinite size of RAM and modern computer? [duplicate]

If modern computers are universal turing machines and C language is turing complete, theoretically we could calculate and simulate every problem in the universe then theoritically we can simulate ...
0
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0answers
31 views

Is simulating the interaction of multiple particles possible in $0$ spacelike and $3$ timelike dimensions?

In multiple time like dimensions it is possible for particles to effect it's own past, and two particles can both be effected by each others future. I tried to simulate the interaction of multiple ...
1
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0answers
28 views

Is there something similar to time step increments for simulating a system of multiple particles in quantum mechanics?

In Newtonian Physics it is possible to simulate a system of multiple electrically charged bodies, that all exert an electric force on each other, using time step increments. For instance given the ...
1
vote
1answer
51 views

How to simulate possible trajectories of particles after $\beta$ decay?

I'm a programmer trying to simulate the movement of the particles involved in $\beta^-$ decay, or at least an approximation of it, for fun, in a 2D universe. I would like to keep the simulation ...
0
votes
1answer
13 views

What is NLL in MC of SM/BSM?

I know that NLO represents using Next to Leading Order Feynman diagrams for a more accurate calculation. And similarly NNLO being Next to Next to Leading Oder. I am wondering what NLL is an acronym ...