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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556 views

Using the Fourier transform to find the natural frequencies of coupled oscillators

How can I find the natural frequencies of a system consisting of a pair of coupled oscillators using Fourier transforms? The System consists of two masses and three springs. One of the springs ...
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1answer
30 views

Is it realistic for soundwaves under water to “sink” or “float”?

I'm studying soundwaves under water and I had a numerical problem that I was asking about. https://stackoverflow.com/questions/28904017/are-my-matlab-iterations-working Now I wonder if you can tell ...
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1answer
677 views

Probability density function of a particle for computation [closed]

I'm writing a program, part of which relies on a particle being able to change location similar to a how a real particle would behave (pardon my physics). For example, on a grid of 100x100, a ...
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1answer
1k views

My python trajectory calculator for a small mass in a gravitational field - why is energy conservation violated?

I wrote this thing to calculate the next position of a small mass, given its current position and velocity, and a vector field determines acceleration. It sort of works - except I can never get the ...
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1answer
2k views

Physical simulation in python [closed]

Is there a "standard" python package used to aid in physical simulations? What is the most popular? edit: perhaps I should have worded this question differently. Something more to the effect: Could ...
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1answer
560 views

Monte carlo simulation for continuous spin model (e.g. XY or Heisenberg model)

Unlike the Ising model, the XY model and the Heisenberg model have a continuous spectrum. So one need discretize them for a numerical simulation. But how to make sure the discretization procedure ...
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2answers
261 views

Energy of damped harmonic oscillator begins to increase with very large Q in numerical integration

I have numerically integrated the (reduced) homogeneous equation of a damped harmonic oscillator in order to see how the error propagates. $$\frac{d^2 X}{d\phi^2} + \frac{1}{Q}\frac{dX}{d\phi}+X(\phi)...
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1answer
132 views

Failure of a simple stat mech simulation

so I did a simple simulation that I thought would yield a Boltzmann distribution, but it failed to, and I was wondering if anyone has insight into why it failed. Ok, so I had a simple discrete system ...
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1answer
184 views

Reference-request: Computational science and physics [closed]

I'm interested in the following question: Is Nature computable at it's most fundamental level? Can anyone suggest any works (books, papers / articles, reviews) related to the above question? (I'...
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1answer
207 views

Filtering and extracting turbulent data from instantaneous dataset

I have collected data on flow velocity at 1 Hz sampling rate for 25 hours using a high resolution acoustic Doppler current profiler (HR-ADCP). how I can decide up to which period is the mean velocity?...
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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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8 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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10 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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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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28 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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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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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
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 ...
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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 ...
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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 ...
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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 ...
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0answers
45 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 ...
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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 ...
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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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1answer
51 views

Bypass valve, pressure and flow rate

I have no background in thermodynamics or fluid dynamics, so please bear with me. Refer to the following figure: A working fluid with a flow rate of $1~kg/s$ enters a heater at a pressure of $1~MPa$ ...
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18 views

Which method can solve the largest number of TISEs?

In my physics studies, we often used separation of variables (or other strong assumptions) to make the problem of solving the 3D TISE more manageable to solve numerically or analytically. In contrast,...
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1answer
70 views

How do you find the initial velocity and angle required to hit a coordinate and a certain height?

Problem For a game engine I'm writing, I need a function that returns the initial velocity and angle of a projectile launch, such that the affected object reaches a given maximum height, and ends up ...
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0answers
29 views

Matrix Used for Orbital Motion [duplicate]

this question is by no means a new question, however previous questions have been unable to exactly answer my question. I'm attempting to obtain analytical results and then plot the results of a ...
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0answers
56 views

Magnetization in a finite lattice Ising model generated with MC algorithm

I generated an Ising model using a Monte-Carlo algorithm and then computed the absolute magnetization per unit volume: $|M|$ and magnetic susceptibility $\chi$ as a function of the temperature $T$ at ...
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0answers
23 views

What is computable and independent of subtraction scheme?

I am trying to compute, using mathematica, the renormalization $Z$s (of the field, mass and coupling) in $\phi^4$ theory (using dimentional regularization). I have done so in two different ...
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45 views

Good introductory book to computational physics [duplicate]

First time asking a question here. As per the title I'm trying to find a decent book that serves as an introduction to computational methods used in physics. A little background on myself will help ...
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31 views

Can we invert Density Functional Theory through sufficiently accurate experiment?

The famous Hohenberg-Kohn theorems say that there is a one-to-one mapping between the many-body Hamiltonian, $\mathcal{H}$, of a solid and its ground-state electron density $\rho(\mathbf{r})$. As far ...
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56 views

Physics Simulation of a Simple Pendulum with Drag Forces

I am working on simulating a simple pendulum with present drag forces. My task is to use numerical methods (I am using Verlet integrator) to estimate the angle as a function of time, as well as the ...
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0answers
45 views

Energy eigenstates using matrices

I just learned that derivatives can be represented as matrices. So, I was wondering if I could write the $\frac{d^2}{dx^2}$ and $V(x)$ as a matrix, maybe I could treat the eigenvalue problem, $${\bf ...
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14 views

What (in silico information) defines the transfer function of a Quantum Amplifier, in the form of a molecule?

Let’s say a team of scientists have published the structure of a molecule they claim acts as a quantum amplifier. Photons travel along a quantum channel carrying qubits in their polarization. The ...
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33 views

Simulation of Spin Hall effect

Is there commercial software available which takes the spin Hall effect into account? I know HFSS and Comsol are popular EM solvers. In my case, I have a piece of metal and a permanent magnet ...
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0answers
48 views

Monte Carlo integration - convergence

I have a 5D integral being calculated with a Monte Carlo uniform random sampling. The issue is that the region of integration is very small and for 100000 points I get only around 20-30 points every ...
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0answers
26 views

Verifying completeness of constants of motion

I can find constants of motion by looking at the null space of the Poisson Bracket operator $ \{H, \cdot\} $ over a polynomial space by brute force with symbolic algebra (code). This scales terribly ...
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0answers
53 views

Inexpensive nuclear reaction simulation tools

I am interested in seeing if there are any simulation software programs for less than $50 that may be used to simulate how neutrons (energies between thermal and 15 MeV) interact with certain nuclei ...
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0answers
79 views

Clarification on DMRG computational complexity

I was reading a paper on the density matrix renormalization group (https://arxiv.org/abs/1008.3477). In DMRG, we gradually grow a chain by inserting a unit cell at the center of the chain (for ...
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0answers
50 views

Is QCD computable?

Are arbitrarily good approximations of the time evolution of any QCD system, given initial and boundary conditions, Turing computable? Can lattice QCD simulations be used to do so in theory? How ...
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0answers
30 views

What methods can be used to interpolate values of a gradient?

Let's say I have a cubic mesh, the points of which I have obtained a vector value for, thus forming this discrete vector space of sort, I'm not really sure of the proper terminology for this which ...
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0answers
42 views

Quantum Monte Carlo Loop Algorithm for quantum spin: why is the freezing graph present in ferromagnetic Ising model?

I study the loop algorithm (Evertz et al). I cannot understand, why the freezing graph type where we have to flip all 4 spins together is not present for the quantum-XY model and the anti-/...
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0answers
17 views

What are possible causes that can lead a self consistent calculation to diverge in DFT?

I am extending a code written to do self consistent Density Functional Theory calculations to the case of spin polarized systems. Due to the modifications, the calculations are leading to diverging ...
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1answer
37 views

Metropolis Algorithm Transition-Proposal Probability

I'm working my way through a short section on the Metropolis algorithm in the lecture notes on Computational Quantum Physics by Prof. Troyer. However, I am not sure what probability distribution was ...
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0answers
56 views

Symplectic time-integrator for Fokker-Planck equation

Is there a way to use a symplectic time-integrator for the numerical solution Fokker-Planck equation of the form: $$\partial_{t}p = -\nabla \cdot (\underline{v}p - D\nabla p)~?$$ where $p = p(\...
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0answers
49 views

$<P_T>$ distribution as function of PL

I have a conceptual problem when working with some Monte Carlo generated data. I have to simulate the $P_T$ and $P_L$ distribution for $N$ particles through Monte Carlo methods as follows: $$\theta \...

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