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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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
64 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
73 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 ...
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2answers
281 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
64 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
87 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
144 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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0answers
62 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
37 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 ...
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0answers
76 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 ...
1
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1answer
84 views

What is the time imaginary method? [closed]

I have to submit homework about the scheme which solves the time-independent Schrödinger equation and finds the ground state by the imaginary time method. I know the substitution $-\mathrm{i}\tau\...
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0answers
31 views

Numerically evaluating momentum sums

For many-body systems, calculations often involve momentum sums, which are ultimately evaluated numerically for a finite system size $N$. The larger $N$ is, the more accurate the results. Is there ...
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1answer
28 views

Numerical computation of electric multipoles

I'm trying to do a plot of the first multipole terms in Mathematica. My plot isn't what I expected, so maybe my problem is in the mathematics. Following the Griffiths' book on Electrodynamics, the ...
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0answers
76 views

Experiments to resolve dillema between continuity and discrete

Which experiments/experimental methods are suggested to resolve an alternative about the structure of our universe space and time - is it continuous or is it discrete in a very small scale, especially ...
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1answer
77 views

Numerical relativity in causally pathological spacetimes

To perform numerical relativity simulations one almost universally adopts the so called "3+1" approach: spacetime is divided up into spacelike slices, each representing a "moment in time". After some ...
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42 views

canonical ensemble density matrix numerical integration of the von Neumann equation

I am working with a numerically calculated Eigensystem of a given non-linear Hamiltonian. As a test I integrated Schrödinger equation for each eigenstate in time with Dormand Prince 54 and also Runge ...
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6answers
6k views

Is there any aspect of an explosion resulting from a nuclear weapon test that cannot be simulated using super computers?

This Washington Post news article states that with the advent of computer simulation of nuclear tests, live tests are no longer needed. Generally speaking there are 3 aspects of an explosion ...
1
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1answer
48 views

Single fluid simulation algorithm

Every fluid simulation I've seen implicitly involves a fluid that isn't mentioned, usually air. This is clear because the simulation usually has an ambient temperature, and always an ambient velocity. ...
1
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1answer
28 views

Why will a Fourier transform of a pickup placed at the middle of a string only result in odd harmonics?

My physics teacher explained a lot of information about strings but he never went in depth with my question. What happens to the even harmonics and why are the odd ones the only ones picked up?
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0answers
49 views

recovering numerical wave function using path integral after Wick rotation

I have written two different path-integral codes, PATHINT and PATHTREE, to numerically solve some classical-physics problems in nonlinear systems, finance and neuroscience. They work just fine. My ...
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2answers
190 views

Do electrons actually reside in orbitals?

(Following this answer on Chemistry.SE) Let's define "dwell"/"reside" as the area in which the probability to find an electron is more than 90%, for example. Calculated orbitals comprise a basis set,...
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0answers
22 views

Heat transfer in liquid helium channel connected to “infinite” reservoir

I am trying to solve the temperature distribution in liquid helium using numerical analysis (OpenFOAM for those who are familiar with it). One part of the fluid is contained in a narrow channel, one ...
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0answers
84 views

Graduate level orbital mechanics book

I recently finished an undergraduate course in classical mechanics and really enjoyed the subject, particularly the sections regarding the mechanics of orbits. I am considering pursuing a graduate ...
2
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1answer
61 views

Difference between finite volume, characteristic method and plug flow models of a pipe

I have to model pipes (of a district heating network) with ODE's. My background is computer-science, so it is not that easy for me to understand different approaches. Finite volume approach. Method ...
2
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0answers
47 views

Is the finite element method easily extrapolable to new disciplines? [closed]

I am a structural engineer with a good solid mechanics background. I am reasonably familiar with finite element methods as applied to linear/nonlinear solids and structures, I would like to know how ...
2
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0answers
35 views

Comparing two versions of the same hydrodynamic code and their error

So I have two versions of a hydrodynamic code that has the same underlying physics. Lets call them code A and B. However code B is more optimized and more object oriented. I was trying to compare the ...
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0answers
174 views

How do you fourier transform a tight binding hamiltonian numerically?

The task is to do a fourier transformation of a tight binding hamiltonian of a 1D-chain with unit cell size 2, but even after many tries and googling I still don't have a idea how to do it correctly. ...
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2answers
96 views

Obtaining Velocity from Acceleration

I'm following a research paper (PDF via RG), part of which is about using the accelerometer of a smartphone to assist the user's positioning via WLAN. Accelerometer is used to determine if the user ...
2
votes
2answers
133 views

Exact Diagonalization of a BdG Hamiltonian on a Finite Lattice

I would like to numerically find the edge modes of a $p_x$ + $i p_y$ BdG Hamiltonian. The lattice version is given by H = $\sum\left[-t \left(c_{m+1,n}^{\dagger} c_{m,n} + \text{h.c} \right) - t\left(...
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0answers
12 views

Numeric fermiomic creation operators and unit cell

I have to do some numerics (e.g. FFT in Maple/Octave) on a 1D fermionic chain without forces between the particles. The description says that two sites build an unit cell. What does this mean? And ...
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2answers
87 views

Molecular Dynamics simulation question

In molecular dynamics simulations you apply and solve Newton’s equations of motion for a set of atoms to obtain real dynamical information on how individual atomic positions change as a function of ...
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1answer
94 views

Modeling transient heat transfer between two 1-D materials

So I have been working on creating a 1-D model of a material with a layer of heat resistant material stuck to it. For this I have been trying to use the implicit finite-differential method. The ...
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0answers
46 views

RF cavity Field Maps using Poisson Superfish

This may be a slightly obscure question but I'm trying to use Poisson Superfish to generate field maps for single cell of an ILC SRF Cavity. There are examples in the documentation for radio ...
2
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1answer
94 views

Why is modelling water so difficult?

There are several models of water that have come into existence so far. Nevertheless, there is no one particular model which effectively gives all the properties of water correctly. A model like TIP3P ...
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1answer
84 views

Is it possible to understand physics and make new discoveries using computer simulation? [closed]

I'm a computer science major and I want to learn Physics. I can create computer simulations of any type. I'm not good at math that is required to learn QFT or GR,but I'm thinking is it possible to ...
2
votes
1answer
181 views

Finding the Riemann tensor for the surface of a sphere with sympy.diffgeom

I have implemented a SymPy program that can calculate the Riemann curvature tensor for a given curve element. However, I am encountering problems solving for the case when the curve element is the ...
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1answer
115 views

How do I calculate the effect of a prograde, retrograde, radial and anti-radial burn on the orbital elements of a two-dimensional orbit?

My relevant knowledge: This question works in two dimensions, with a two-body problem (see bottom for context). To my understanding, a two-dimensional orbit has the following orbital elements (3D ...
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2answers
84 views

What is the output of a simulation of quantum particles? [closed]

When physicists simulate a quantum system, what is the output of such computation? Is it the probability wave function of the system? What if the system consists of enough particles to be considered ...
0
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1answer
141 views

Calculating Reynolds number of ellipse in fluid

I know Reynolds number is calculated from the formula by including length or diameter of an object in fluid. I have a case where there is ellipse with 2a major and 2b axis. I hv learnt when the ...
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2answers
195 views

Must-know topics for Computational Fluid Dynamics (CFD)

My undergrad major was Electrical Engineering. My MS thesis is related to simulation of hydrogen movement in a complex geometry. I did take a course on Fluid Dynamics but I have to say it wasn't one ...
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92 views

Obtaining propagating solutions for Schrodinger equation from known bound states (in 2 and 3 dimensions)?

If I found all the bound states for a certaing potential in 2 or 3 dimensions (numerically), can I immediately obtain some information about the propagating solutions for the same potential (such as ...
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3answers
182 views

How to propagate $E_x (x,t) = \exp(-t^2/\tau^2-i\omega_0 t) \exp(-x^2/w_0^2)$ in finite difference time domain (FDTD) analysis

Finite difference time domain (FDTD) allows to solve differential equations for time evolution. For example, we can analyze ultra-short pulses in free space by solving the Maxwell's equations. The ...
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0answers
56 views

Numerical approach to Mean Field Hubbard Model

I am trying to produce the phase diagram of a 2D Hubbard model on a Lattice for spineless bosons. The hamiltonian of the problem is: $$ H = -t\sum_{<i,j>}(b_i^+b_j + c.c.) +U\sum_i \frac{n_i(n_i-...
2
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1answer
199 views

Problems implementing Lattice Boltzmann method

I want to make a basic 2D implementation of the Lattice Boltzmann method (in javascript) to simulate gas/fluid flow, but I have run into some problems and I can't seem to find the cause of it. ...
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2answers
147 views

How Much Computing Power would be Required to Fully Simulate a Cubic Meter? [closed]

Imagine you want to simulate a cubic meter down to the particle. By following the Standard Model and other basic physical equations, how much computing power would be required to do this, in say, a ...
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2answers
224 views

Diffusion of gas into vaccum

I'm interested in solving the diffusion equation for gas in vacuum. I have a general question and a more specific questions. What I know: The Diffusion Equation: For density function $\phi(\vec{\...
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1answer
51 views

Reading ensdf files

I understand that this is more of a computing question, but I still think the appropriate place to ask it is here. The Evaluated Nuclear Structure Data Files are on the internet, available for ...