Subdiscipline of theoretical physics which consists in the study of physics problems using numerical algorithms. PLEASE NOTE that questions about computational methods and/or programming are OFF-TOPIC on Physics.SE.

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66 views

Methods for handling close approaches in $N$-body simulations

In direct gravitational $N$-body simulations, what are the preferred methods for handling close approaches between bodies in order to preserve the accuracy of the evolution of the system?
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66 views

Simulating TE011 mode in cylindrical cavity, Comsol [closed]

I have been trying to simulate TE011 mode in a cylindrical cavity by modifying the example given in Comsol site(https://www.comsol.co.in/model/computing-q-factors-and-resonant-frequencies-of-cavity-...
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25 views

Choosing the boundary conditions knowing the potential

So I have to apply Numerov's algorithm to solve the Schrödinger equation in spherical coordinates using the potential $V(r)=-A e^{-r/a}$, where $A=32.7MeV$ and $a=2.18fm$. I have already ...
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1answer
74 views

Schrödinger equation in spherical coordinates using Numerov's method?

So I need to solve the Schrödinger equation using Numerov's method. However, the problem I have assigned to me is in spherical coordinates. As it seems, I only need to take into account the dependance ...
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16 views

Spherical Harmonic fitting excess polar magnitudes

I am trying to fit an expansion of spherical harmonic functions to a dataset distributed over the surface of a sphere using the least squares method. Each data point is in terms of $(r,\theta,\varphi)$...
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1answer
50 views

Current Status of the Monte Carlo Sign Problem

I've been reading about the Monte Carlo sign problem, and I am a little confused about its current status. Specifically, after reading this post When is the "minus sign problem" in quantum ...
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0answers
33 views

Calculate 2D Effective mass from bulk effective mass

I am trying to create a self consistent Shrodinger Poisson Solver for various semiconductors. There is already one done by Professor Hu from UC Berkeley - QM CV Simulator. Looking at the code, they ...
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1answer
54 views

Numerically finding the energy diagram of the hamiltonian

I'm looking at a collection of three two level systems (qubits) coupled to each other (with known bare state energies and couplings). The hamiltonian is given by $$\mathcal{H}=\sum_{i=1}^3{\omega_ia^\...
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19 views

Standing waves and acoustic levitation

i am doing a new personnal project about acoustic levitation with standing waves into ambiant air using a piezo ultrasonic tranceiver and a reflective pannel. I modelised both of the emission and the ...
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24 views

Plotting EM fields

I am currently studying transformation optics and learning about electromagnetic cloaking. To plot my results(Electric and magnetic fields) i have to solve maxwell's equations given the permeability ...
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1answer
35 views

Simulating the Electric Field inside a Hollow Sphere of Uniform Charge

I've recently been studying Gauss's Law and have come across some results that I want to verify. For one, I am trying to verify that the electric field inside a conductor (in this case it could be ...
0
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1answer
94 views

Quadratic drag projectile motion

I have calculated formulas with 1 dimensional trajectory motion (free-fall) including quadratic drag, and have created the following equations. These equations of motion are not of much use on its ...
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1answer
14 views

Which are the best books I can refer for turbulent heat transfer and its computation?

I am a graduate student. I wanted to do computation on heat transfer problem mainly heat convection. I am working on turbulent regime. Can you kindly suggest some good books so that I can get ...
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64 views

Which formula was used to get Gravitational Waves animation?

I would like to make animation like this by myself It is from wikipedia article "Gravitational wave". But if I use formula from wikipedia article "Gravitational wave" subsection "7.2.2 Wave ...
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1answer
38 views

N-Body Simulation for Photons

For my undergrad optics class I am taking we have to select final projects to work on for second half of the semester. I have spent the last few weeks working on my own project which was a GPU ...
0
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1answer
49 views

Review article recommendation in the field of 2d materials

I am new to 2d materials. I tried to search related review articles in review of modern physics, but did not find anyone covering the whole of the 2d material area. Anybody can recommend some latest ...
2
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1answer
280 views

Is Machine Learning a useful tool for analyzing experimental data? [closed]

Apart from being a student of Physics I'm also a developer and recently in the context of cloud development I've been hearing a lot about cloud based Machine Learning. After looking at some examples ...
4
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1answer
80 views

Do black hole merger simulations include regions inside event horizons?

Inspired by this question, I would like to ask the following specific point. In numerical simulations of general relativity that involve black holes, like the ones used to understand the black-hole ...
0
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2answers
74 views

About unit definition in numerical computation [closed]

I attend an undergraduate level course of quantum mechanics. I am thinking of computer computation on a quantum mechanical problem. I do not have much experience in numerical computation, so I read ...
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1answer
48 views

Calculating orbits with varying laws of physics? [closed]

The general way planets orbit stars in our universe is determined by the inverse square law and the three laws of motion. Both the inverse square law and the three laws of motion are the reason that ...
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23 views

Numerical simulation of strong field gravitational vacuum solutions colliding

I am interested in the current state of knowledge of strong field General Relativity learned from numerical investigations of gravitational wave packets colliding with each other or black holes. If ...
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0answers
23 views

photometric redshifts - the origin of 1 / (1+ zspec) in photometric accuracy

i have a training sample of sources with known spectroscopic redshifts ($z_{\rm spec}$) and i run a photometric fitting code that uses a template to determine the photometric redshifts ($z_{\rm phot}$)...
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0answers
36 views

Vortex in a Pipe / Solutions or approximations?

I want to study a vortex flow in a pipe; in other words helical flow. A couple introductory texts on fluid mechanics (e.g. Shames, Mechanics of Fluids) describe the solution to vortex flow in 2D: $...
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2answers
75 views

time step in kinetic montecarlo simulation

I have a doubt about how the time step is calculated in kinetic montecarlo simulations. One state with index $i$ is connected to other $N$ states, indexed by $j=1...N$, by transitions that happen ...
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0answers
17 views

Explicit solvent simulations in NVE ensemble: Molecular Dynamics

I am simulating a SDS micelle system in NVE ensemble at room temperature. I am not sure if the system is equilibrated, since the pressure variations are around 100's of atm, where the average pressure ...
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0answers
23 views

Efficient ways to solve complicated kinematics problems

I'm curious about the range of approaches one can take to perform motion/kinematic simulations on many 3D objects. Currently I am familiar with the iterative process of doing such a simulation, that ...
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0answers
24 views

Books on Spectral Jacobian

Can anyone point me a book to better understand "spectral Jacobian". I am studying X-parameters, I have the book X-Parameters: Characterization, Modeling, and Design of Nonlinear RF and Microwave ...
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28 views

Initial guess for calculating the Universal Variable Formulation of the two-body Kepler problem

I am trying to simulate orbits using the Universal Variable Formulation of Keplers two-body problem, using the algorithm provided by Howard curtis in Orbital Mecanichs for Engineering Students as per ...
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30 views

Open-source code for computing response functions

Summing Feynman diagrams to compute the response functions of a microscopic model is common in many areas of physics. While conceptually straightforward, the task can be computationally intensive. ...
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1answer
45 views

Monte Carlo simulation of Breit-Wigner

I am using a Monte Carlo approach to integrate a scattering amplitude which has a propagator-squared term like $f(s)=\frac{1}{(s - 4)^2 + 1}$, between $s=0$ and $s=20$. Using a uniform random ...
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2answers
256 views

In a Monte Carlo NVT simulation How do I determine equilibration

I'm running an NVT (constant number of particles, volume and temperature) Monte Carlo simulation (Metropolis algorithm) of particles in two dimensions interacting via Lennard-Jonse potential ($U = 4(\...
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1answer
226 views

Tight binding Hamiltonian for 2D finite dimensional lattice and nanowire

The Hamiltonian of a 1D lattice having finite $N$ atoms, (if we consider one basis per atom) is given by the following $N\times N$ matrix- Here $E$ is the onsite energy and $t$ is the hopping ...
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1answer
98 views

Numerically solving a simple Schrodinger equation with fast Fourier transforms

While trying to solve a stochastic Gross-Piaevskii equation I have found a problem that can be tracked down to something buggy occurring in the simplest Schrodinger equation possible: $$\partial_t \...
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0answers
67 views

Electromagnetic scattering $T$-matrix in MATLAB

My problem with the inverse of the matrix T (in the photo) , the matrix consists of Bessel and Henkel functions in high order (the orders from 1 to 21), then the elements of this matrix arrived to ...
2
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1answer
54 views

Quantification of uncertainty, or information loss, when modeling a physical system?

Say I have a physical circuit (say a battery, wires and an incandescent lamp) that I want to model. To model it I could perhaps use: traditional circuit theory some kind of finite element analysis ...
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2answers
101 views

Statistical specific heat as energy fluctuation in spin glasses

Consider the specific heat (in statistical sense, as energy fluctuation in the canonical ensemble) of a complex model, something similar to a spin glass. Is the specific heat defined on fluctuations ...
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0answers
47 views

About multi dimensional numerical integration [closed]

I want to calculate 4 dimensional phase space integration.If anybody help me with a general 4 dimensional integration that will be OK. I can apply trapezoidal or Simpson's rule in lower dimensional ...
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5answers
1k views

Why do objects in a gravity simulation experience sudden large accelerations?

I'm trying to create a simple program that simulates gravity. The idea is that I have one central sun and several planets that I can create with a swipe gesture on the screen, and I use the initial ...
2
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1answer
34 views

Testing the accuracy of a solar system simulation

I've written a java program to model the solar system, and I need to test its accuracy. What would be some good ways to do that? I've checked for conservation of energy and angular momentum. I'm using ...
0
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1answer
63 views

Lollipop 3d choreography animation

I initially wanted to recreate the little dancing dots android lollipop's boot animation in javascript: For that, I've implemented a 3d $n$-body simulation (with css and js): http://codepen.io/...
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0answers
24 views

Package for flavour physics computation? [closed]

Which softwares one usually uses for flavour physics related calculations? I saw one called SUSY_FLAVOR. I haven't used it yet though. What in case of other BSM models other than SUSY? Is there any ...
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0answers
68 views

Software engineer vs physics engineer vs computational physics [closed]

Don't know if this question is off topic, but i think it is the best place to get an answer. I am finishing the 3rd year of a degree in physics engineering. I enjoyed the first year, but in the ...
7
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2answers
274 views

Why do we still use perturbation theory, when we have advanced numerical methods and fast computers?

If my question sounds ignorant or even insulting, I apologise. I may be completely wrong, since I'm not a theoretical physicist. So, I understand why perturbation theory was originally used in ...
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0answers
63 views

Numerical problem with Hartree-Fock equations for dilute Bose gas

I have to solve the following set of equations self-consistently: $$\begin{align} n_c(\mathbf{r}) & = \frac{1}{g}\left[\mu - V_{\rm ext}(\mathbf{r}) - 2 g n_{T}(\mathbf{r}) \right] \\[3mm] n_{T}(\...
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2answers
72 views

Can lens designs be brute-force computed to create optically precise equipment? [closed]

It seems lens design hasn't changed much over the last 50 years or so with many older manual lenses still very much being used today. Can the order, distance between and type of lens elements be brute ...
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1answer
22 views

How to choose basis functions that contribute most efficiently per term? [closed]

I would like to approximate some positive, scalar function $f(x,y) > 0$ on a 2D field of finite size i.e. $x\in [a,b],y\in[c,d]$ I am familiar with the set of basis functions used in the Fourier ...
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1answer
71 views

Gravitational field of thin 2D ring - numerical simulation

I'm aware of Newton's Shell Theorem, which states that inside of a thin ring of uniform density, the gravitational force exerted on a point mass should be zero. I wrote a quick field simulation to ...
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1answer
136 views

Conversion of satellite coordinates from ITRF to J2000

I have coordinates of various satellites in two coordinate systems: Cartesian coordinates in the international terrestrial reference frame (ITRF) RA / DEC in J2000 epoch, as derived from plate ...
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60 views

What is an intensive property of a fluid?

Let's assume we are considering a fluid which occupies the bounded domain $\Omega_t\subseteq\mathbb R^d$ at time $t\ge 0$. Let $c\in\Omega_0$ be a particle of the fluid and $$x_c:[0,\infty)\to\mathbb ...
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1answer
35 views

Does *advection* describe the change of density of massless infinitesimal tiny *thingies* injected into a fluid?

I'm considering an incompressible Newtonian fluid with uniform density and try to figure out what's meant by the term advection. Let $\Omega_0\subseteq\mathbb R^d$ be an (infinitesimal small) bounded ...