Questions tagged [computational-physics]

Questions with this tag should be about computational physics, which is the study of physical situations with the use of software (commercial or in-house). Please note that details of writing and/or debugging code is OFF-TOPIC and should be asked at either Computational Science, Code Review or Stack Overflow.

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23 views

How to color-plot a function in Polar Coordinates? [closed]

So, I have been bothering myself the past day on how to plot a Graph on Cartesian Grid (x,y), while the Variables the Function takes as Input are Polar (r,theta). This is the part of the code that ...
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10 views

Numerical integration methods: Explicit vs Semi-Implicit vs Newton-Euler 1, 2 and use in cyclone physics engine [migrated]

I am trying to understand the difference between explicit Euler and semi-implicit Euler integration, where in explicit Euler the current position is calculated as ...
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0answers
7 views

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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9 views

Why the Interaction potentials parametrisations for Bulk system is not working for Nano-systems?

I am studying several thermodynamics properties of crystalline iron oxides (Fe3O4, Gamma- Fe2O3) in their solid phases by MD simulations. At the moment, I am facing many difficulties in simulating the ...
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23 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
56 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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0answers
42 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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4answers
54 views

Selecting Direction to Avoid Other Moving Bodies

I have several point-bodies (shown below in black) moving at constant speed, with no change in orientation. Given an arbitrary point (such as the red point), how can I find which direction to move in ...
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0answers
32 views

Good resourse for Ising Problem Model

I am student of mathematics, and I will wrote theoretical article about Ising problem in Adiabatic Computation. Do you have a good resource where it is good explaining? In my context I have ...
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0answers
24 views

What's the point of observing independent samples in Ising Model for a Monte Carlo simulation?

Something about the uncorrelated samples of observations in Markov Chain Monte Carlo(MCMC) simulation of my Ising model has been confusing me. Before I start asking my question, I'll first describe ...
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27 views

Looking for a freeware software/app that can solve eigenvalue problems symbolically

I'm taking a quantum mechanics course and my homework involves extremely tedious algebra to solve symbolic eigenvalue problems. I'm looking for a software that I can give matrices with symbolic ...
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0answers
19 views

Generating a flow field around a body?

How do I model (in MATLAB preferably) the following: for an arbitrary body and arbitrary flow field, generate a new flow field that goes around the body (but looks like our original flow field). ...
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0answers
19 views

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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0answers
11 views

Calculating energies in Coulomb regime, is there an equivalent to the Fourier transform for free space?

In free space, one can find the energy decomposition of a wavefunction by using Fourier transform. Is there an equivalent common transformation to do this for a wavefunction in a Coulomb potential? ...
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10 views

Proper way of applying absorbing boundary conditions to discrete differential equation system

I have 2nd order $1+1$ dimensions PDE (a wave equation) that I have rewritten as a coupled system of first order equations and discretized the spatial dimension using a grid of $N$ points labeled by ...
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70 views

Solving simultaneous non-linear equations [closed]

I am working on a problem in infrared spectroscopy. I have an unknown function of transmitter receiver distance, $a( d )$, which I want to determine for several fixed distances. I have an unknown ...
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0answers
36 views

Leapfrog integrator, kill off lower order terms [closed]

Let $H=A+B$ be the Hamiltonian, let $L_A(\cdot):=[\cdot,A], L_B(\cdot):=[\cdot,B]$ denote the Lie derivatives of $A, B$ respectively. We can show that the leapfrog integrator $$ \exp(\frac{\tau}{2}...
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1answer
29 views

Example of complex system, whose components have string etc. valued properties?

Complex systems are branch of physics, Phys. Rev. E has section about them. Complex systems consist from interacting components, each component has some set of properties whose values can change due ...
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80 views

Understanding quantum field theory via simulation

I took graduate QFT course 10 years ago as an undergrad. Did all the homework assignments but it never quite stuck. I think I'd understand the subject better if it were presented differently; ...
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1answer
33 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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0answers
36 views

Instability of coupled non-linear oscillators

Consider a bunch of interacting oscillators (e.g., a chain of atoms), interacting due to anharmonicity in the potential energy. You can Taylor expand the force on each oscillator about equilibrium ...
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0answers
45 views

Propagation of a Gaussian beam using FFT [closed]

I am trying to simulate the propagation of a gaussian beam through a lens using an FFT approach. I tried to implement the approach described by Couairon in this paper at page 43: https://link....
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1answer
34 views

Interpreting Slater-Koster files for DFTB

I have a question about interpreting .SKF files, I am using these parameters to model defective graphene, when I use parameter set given here: dftbBaby/C-C (I think this is from Hotbit) or the ...
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0answers
15 views

Best software to fit molecular spectroscopy data

I have some data from a molecular spectroscopy experiment, containing vibrational and rotational spectra, and I want to fit the peaks with Voigt profiles (one for each peak) in order to obtain the ...
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0answers
42 views

Constant Values with non SI units

I'm trying to code a program to study the energy levels of Helium using the variational method, but I'm not sure my constant values are correct. I'm using Angstroms as the unit of distance and $eV$ ...
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0answers
52 views

Calculate Distance to Stop With Acceleration and Drag [closed]

This is a part of a larger flight control system that I need to be able to approach a target position and stop exactly on it. https://github.com/ChristopherSharp/KinematicFlightController I have ...
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1answer
34 views

Reference for light interaction with many electron atoms

I am trying to understand light interaction with many electron atoms. I know that to calculate the bound states we can use Hartree-Fock method but for light interaction with matter i do not know it ...
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0answers
88 views

Exchange has closed form also in DFT?

I have heard from my lecturer that in the context of DFT, the exact exchange energy has a known closed form, even though it is not a functional of the density. I have been trying to figure out what ...
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0answers
34 views

Required Preconditions for Galactic Formation

In recent weeks, I have been working on building simulations to look at the formation of galaxies from dust clouds. It's a relatively crude simulation at this point as I needed a working model to ...
3
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1answer
56 views

Resources to learn about Quantum Monte Carlo?

This is a very, very broad question, but I've recently become interested with Quantum Monte Carlo (QMC) and other numerical techniques in physics and computational physics, though my undergraduate ...
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0answers
25 views

Double zeta polarised, triple zeta double polarized. What is the definition?

I understand that a single zeta basis contains the hydrogen stationary states $\psi_{nlm_l}$ for a particular selection of quantum numbers $(n,l,m_l)$. You can decide the quantum numbers that will be ...
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0answers
11 views

Metropolis sampling of branching problem

I have a particle in one dimension sitting at $(x_0,t_0)$, where $t_0$ is the currently time. At a certain time $t \ge t_0$, this particle can split into to 2 particles. The distribution of the ...
5
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0answers
73 views

Simulation of a dispersive crystal mirror

I am trying to simulate a simple setup where I have a point source of broadband light whose light is incident upon a spherical crystal at a central angle $\theta_i$. Assuming Bragg diffraction some of ...
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1answer
28 views

Can we plot a FFT for a Decibel vs Seconds data?

I was plotting FFT for Decibel values corresponding to the time in which it was recorded using a DAQ for My project, The sample data looks like this, I was attempting to plot the FFT thinking that ...
2
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1answer
93 views

Deformation of Schwarzchild radius of two approaching black holes

I'm trying to visualise merging black holes. Here's my impression of a single black hole: Green is the strength of gravity outside the Schwarzchild radius, blue is the strength of gravity inside the ...
1
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1answer
64 views

Is there a way to perform Ising model simulations with a Game of Life approach?

This question may turn out to be trivial or nonsensical as I do not have more than undergraduate understanding of both the Ising model and computational physics simulations. I just wanted to post ...
2
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1answer
123 views

How is a function approximated by Fourier analysis?

Quantum mechanics and QFT use extensively Fourier analysis. When trying to approximate a periodic function by Fourier series (say a rectangular wave), it is possible to increase the number of terms ...
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1answer
45 views

Numerical simulation for spontaneous parametric down conversion

I want to numerically simulate the SPDC (spontaneous parametric down conversion) process. I have a basic background on nonlinear and quantum optics — I am a graduate student and just took a few ...
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1answer
56 views

Time dilation in the Reissner-Nordström metric [closed]

According to Wikipedia, the formula for gravitational time dilation in the vicinity of a charged mass is: $$\varsigma = \sqrt{|g^{t t}|} = \sqrt{\frac{r^2}{Q^2+(r-2 M) r}}$$ However, if I plug in $M=...
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1answer
59 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 ...
10
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2answers
203 views

What is meant exactly by “renormalization” in condensed matter physics, specifically in density matrix renormalization group (DMRG)?

I first encountered the concept of renormalization in the context of statistical physics. Here, the renormalization "group" is a set of transformations of the system such that the Hamiltonian $H(J,\...
0
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0answers
32 views

Is there any library or mathematica package to computing things like collision term or find distribution function of Boltzmann equation?

Today there is a lot of package in mathematica or another library that are very useful, like SARAH for particle physics. But actually I am working with particle physics in early universe. In another ...
1
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1answer
34 views

Modelling a particle under the influence of an electric field with a restoring force

Suppose I have a particle under the influence of an electric field. The particle is also attached to a spring. The particle should therefore feel the influence of two forces such that the total force ...
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0answers
30 views

Lens phase mask on a laser beam profile in Fourier space

I have a Gaussian laser profile on which I want to apply a phase mask that acts like a lens. The phase mask is given by $$M_{lens} = \exp\left(-i\frac{k}{2f}(x^2 + y^2)\right)$$ where $x$ and $y$ are ...
0
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2answers
52 views

How to draw quiver plot for complex-valued electric field?

I have a matrix of complex numbers for the electric field inside a medium. Since I want to draw the quiver plot of these elements, it will be completely different if I only use the absolute part. Then ...
2
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2answers
124 views

Lift of an airfoil: viscous vs inviscid results

I am trying to understand the difference between the lift computed with an inviscid solver (Euler equations) and the one computed with a viscous solver(Navier Stokes equations). At this point, I ...
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0answers
43 views

Tight Binding Hamiltonian simulation help

Just want to make sure I am setting this up correct. I am trying to find the eigen energies for a tight binding Hamiltonian, let's say with nearest neighbor hopping term $t$. We can solve for the ...
0
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0answers
29 views

Does the mass of a rigid-body affect its bounce?

I'm working on a computer program which involves some physics. I want to know if the mass of a perfectly rigid ball will affect how high it bounces off the ground. I'm in high school and I haven't ...
1
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0answers
67 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 ...
0
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0answers
12 views

flow distribution in pipes incl. hydrostatic pressure

Imagine a system like this: A pipe fed from a pump branch into different branches, it's not a closed loop. There are non-negligible differences in elevation between the pipes. My goal is to ...

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