Questions tagged [simulations]

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10
votes
1answer
238 views

What's the cause of this gap in this simulation of the Nice model?

A previous question brought me to this video (which has a spectacular change at about 0:34). It shows the orbits of Jupiter, Saturn, Uranus, Neptune, and what appear to be trans-Neptunian objects. ...
9
votes
1answer
768 views

Boundary conditions on current carrying wire

I'm trying to simulate by finite elements method Maxwell equations for a current carrying wire. My 3d geometry consists of a cylinder and a box containing it. I will use a mixed formulation and ...
6
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0answers
208 views

Final-state baryons in $p \bar p$ collisions in Pythia

I'm trying to simulate inclusive $\chi_c$ production in $p \bar p$ collisions at very low energies (~ 5.5 GeV) using Pythia8 event generator. Leaving aside problems bounded with applicability of ...
6
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0answers
88 views

Animating the Bosonic String

I am interested in studying the classical solutions to the Bosonic string in flat 3+1 dim. spacetime by having them rendered a moving picture on a computer. This is partly for fun, and partly to ...
5
votes
0answers
106 views

Do systems of fermions take longer to equilibrate than systems of bosons for complexity-theoretic reasons?

This excellent paper by Scott Aaronson persuasively argues that computational complexity can be relevant for physical processes. In particular, what's hard for a hypothetical Turing machine to do may ...
5
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0answers
164 views

BEC in a rotating disc

Goodmorning everybody, I have to run a numerical simulation of a Bose-Einstein condensate on a rotating disc. Now, my problem is that I became suspicious about the equation I'm using, since the final ...
4
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0answers
194 views

$N$-body gravity simulator: why does energy conservation break down when introducing an adaptive timestep?

I am playing with an N-body gravity simulator using the velocity-verlet algorithm. In the actual simulation I normalize everything so that it is nicely behaved numerically, but I'll express things in ...
4
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0answers
166 views

Adiabatic turning on of coupling constant in simulation of $\phi^4$ theories in the JLP algorithm

In the Quantum Algorithms for Quantum Field Theories by Jordan, Lee and Preskill they have devised an efficient algorithm to simulate $\phi^4$ theories. Given by the Lagrangian density $$\mathcal{L}(\...
4
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2answers
672 views

Boltzmann Distribution of Electrons in Confining Potential

I have a particle simulation wherein many non-interacting electrons are trapped in a electric potential well. I would expect, and therefore I initialize according to this, that the electrons would ...
3
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0answers
68 views

Quartz crystal resonance frequency simulation

Is there an open source/scientific software package that would allow to simulate Quartz crystal resonance frequency for specific cut angle, crystal geometry and temperature? How would one approach ...
3
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0answers
30 views

No sign problem in quantum Monte carlo simulations of 1D systems?

I've heard many times people saying that there is no sign problem in the quantum Monte Carlo simulations of 1D locally interacting quantum systems. I think this means, for any 1D locally-interacting ...
3
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0answers
105 views

What is the correct way to perform numerical integration over Brillouin zone?

Let us have an integral $I$ over the first Brillouin zone (BZ) of a 2D lattice. $$I = \int\int \Omega(k_x,k_y) dk_x dk_y$$ where $\Omega(k_x,k_y)$ is some function (let's say it's Berry curvature). ...
3
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2answers
72 views

Using Runge-Kutta method with measurements of acceleration (what to do with half-steps?)

I'd like to perform a short-time motion estimation based on measurements from an Inertial Measurement Unit. If I use the Runge-Kutta method, I will need to compute the k values at half-time steps (Ref)...
3
votes
1answer
118 views

Derive shape of sound wave from vibrating string simulation

I have a physical simulation of a vibrating string (made with matter.js). From this, how can I derive the sound wave / air pressure over time, that would result from such a string? I had considered ...
3
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0answers
313 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 ...
3
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0answers
339 views

Physics simulator to test the properties of metal alloys

In my free time I enjoy designing and invent random devices that do a variety of things and as part of this I design the materials that would be used to make the object, taking into account the needs ...
3
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0answers
69 views

Unexpected behaviour in numerical simulation of polymer

I noticed some strange behaviour when simulating the behaviour of a polymer subjected to an external pulling force at both ends, and would like to better understand its origin. I used LAMMPS to ...
3
votes
1answer
208 views

Gravity assist, Coordinate system transformation

I am currently learning about the physics and the mathmatics behind gravity assist. I have a question regarding the coordinate transformation between the planet frame and the sun frame. I want to ...
3
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0answers
288 views

Acceleration vector of tipping object (robot)

I am about to develop a simulation application of a robot. For that reason, I would need to calculate the acceleration of the robot (centre of mass) when its centre of mass exceeds its feet (ie it ...
3
votes
0answers
1k views

Simulating a noisy image: Poisson Noise Clarification

I'm currently working to simulate an image that mirrors the output of a CMOS camera we have in the lab. My images include Poisson (photon) noise as well as a gaussian (readout) noise. My issue is ...
3
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0answers
87 views

Barycenter correction for inner planets in solar system?

I want to run simulations of the solar system, and I've read in some papers that to speed up the simulations it is useful to use the barycenter correction of the inner planets (from Mercury to Mars), ...
3
votes
2answers
48 views

How to efficiently cool down simulated gas by time-dependent potential?

I'm trying to simulate condensation of a highly diluted gas (a model gas, not any real one). For simplicity I restrict the simulation to 2 dimensions. To setup the simulation I take some interparticle ...
3
votes
0answers
412 views

How to calculate dispersion relation from a Finite Difference (FD) wave simulation

I have a python code that calculates the solution of the inhomogeneous acoustic wave equation for a 2D medium with any velocity and source configuration. It was implemented using Finite Differences ...
3
votes
1answer
78 views

Comparing two versions of the same hydrodynamic code and their error

I have two versions of a hydrodynamic code that has the same underlying physics; let's call them code A and B. However, code B is more optimized and more object oriented than A. I was trying to ...
3
votes
1answer
1k views

Determining velocity of moons

I have a question that I believe is relatively easy to answer, I am working on an $N$-body simulation of a fictional star system and am having trouble finding the velocity of moons so that they will ...
3
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0answers
81 views

What is the output of a quantum simulator?

First off the bat, the context of this question is philosophical, but please don't run away, since a physicist is required to comment on this one: Philosophers sometimes contemplate a hypothetical ...
3
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0answers
87 views

Modeling the formation of a stellar system and matter accretion

I am trying to figure out what do I need to know to properly simulate the creation of a solar system from a particle cloud with random distribution of hydrogen atoms. Being more of a programming ...
3
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0answers
272 views

How can one activate the decay of the quark b with PYTHIA event generator?

This is my problem and I hope finding a solution. _In the simplest alternative, MSTJ(22) = 2, the comparison is based on the average lifetime, or rather (c*tau "time life") , measured in mm. Thus ...
3
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0answers
2k views

Damping and stiffness constants of water

I'm working on a simulation of water drops falling into a pool. I'm specifically interested in the waves generated by the impact of the drops. In order to calculate the vertical motion of the waves, I ...
3
votes
1answer
225 views

Simulation of oscillator with frequency dependent damping

What would be the equation for the frequency dependent damping of harmonic oscillator? Is there something like: $$ \ddot{x}+2\delta\dot{x}+\omega_0^2x = \frac{F}{m}f(t) $$ with frequency dependent ...
2
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0answers
38 views

Can we simulate hydrogen atom formation?

Is it possible to simulate the formation of a hydrogen atom from a single free electron and a free proton? The Hamiltonian for the Schrodinger equation of a free electron and free proton is the same ...
2
votes
1answer
61 views

How can mass diffuse out of a lagrangian control volume when it always tracks the same mass?

I am trying to understand how mass conservation in fluid flow works and how it relates to lagrangian and eulerian control volumes. The way I understand eulerian control volumes is that they are ...
2
votes
1answer
24 views

How can FDTD be divergence free when approximating co-located points of E and H on the Yee cell?

I am using this source as a means to produce a 3D FDTD code which can handle anisotropic material. Because tensors are used, all components of the $E$ and $H$ fields must be used when calculating the ...
2
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1answer
49 views

Deformation of a sphere

I am currently building a computational model for a simulation of a rover landing on the surface of mars. As part of the assignment I need to model airbags being used to cushion the fall. (Assuming ...
2
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0answers
160 views

Decorrelation times for a 2D Ising Model over a range of temperatures

So, I'm trying to simulate the Ising Model on a 2D square lattice of spins. When exploring the auto correlation of the magnetisation: Where the auto covariance: $$A(T) = \langle(M(t)\ - \langle M\...
2
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0answers
28 views

Impulses in a Collision

The question I have is that of computing the impulse in a collision between two objects in real life (or in a scenario that is very close to real life). I wish to simulate collisions of objects of ...
2
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0answers
45 views

de Broglie vs Schrodinger models: Why is the IR spectra different in PhET simulation?

I was playing around with the PhET simulation "Models of the Hydrogen Atom", https://phet.colorado.edu/en/simulation/legacy/hydrogen-atom . In it you can simulate a hydrogen atom's electron ...
2
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0answers
22 views

Vehicle Drive Model - wheel and engine angular speed approach

I am trying to create a simple car simulation in 2D in Unity3D, I'm having a hard time figuring out the right approach. Say I have given the throttle percentage, I know the current engine's and wheels'...
2
votes
1answer
64 views

Unitary Coupled Cluster Operator

In quantum computing, we always want to deal with unitary evolution operators. That's why the traditional definition of the Coupled Cluster ansatz is modified to the so-called Unitary Coupled Cluster, ...
2
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0answers
51 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 ...
2
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0answers
38 views

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 ...
2
votes
1answer
74 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 ...
2
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0answers
30 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 ...
2
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0answers
65 views

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 ...
2
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2answers
140 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 (...
2
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0answers
39 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 ...
2
votes
1answer
87 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/...
2
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0answers
84 views

Geant 4, simulate Tc-99m decay

I have a setup of Monte Carlo simulations in Geant4, and I'm able to simulate radioactive events from isotopes such as I-131 and F-18, which are defined in the RadioactiveDecayData5.2 files. Tc-99m ...
2
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0answers
38 views

How to set the number of fermions in the whole system in fermionic-DMRG program?

In infinite DMRG (density matrix re-normalization group) algorithm, we increase size of super-block by two sites in each iteration. How do we set number of fermions in the system? Let's say we want to ...
2
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0answers
42 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 ...

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