Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

1
vote
1answer
53 views

Is Verlet method suitable for to solve projectile motion with quadratic drag?

Consider the following non-dimensional equations of projectile motion in presence of air resistance, I understand it can be numerically solved using the mid-point method, but can I also use Verlet ...
1
vote
0answers
18 views

Arranging objects by mass [on hold]

I have n objects with different masses . Say mass of n1=m1, n2=m2 .... so on. I want to use concept of centrality in physics to arrange these objects in a field (computer simulation ) . Where object ...
0
votes
0answers
74 views

Maxwell's equations UPML in FDTD with inhomogeneous media

I'm looking at matching the UPML (uniaxial perfectly matched layer) defined in Taflove&Hagness' Computational electrodynamics to an inhomogeneous media (inhomogeneous w.r.t. both $\varepsilon$ and ...
1
vote
0answers
24 views

Metropolis method under the Gand Canonical Ensemble

I am writing code to simulate Langmuir adsorption using Metropolis method under the Gand Canoninal Ensemble. Aided by the Wikipedia Article, I derived the corresponding equation, proposed a sample ...
0
votes
1answer
45 views

Correlation function at zero distance

I'm confused about the definition of the correlation function (at equal time). I know it is defined from the thermal average of the scalar product of two random variables (for example the spins of a ...
1
vote
0answers
37 views

Gravitational $N$-body mergers?

Beyond binary systems and its mergers, have numerical relativity groups computed an approximation to $N$-body GW signals/waveforms or is that a hard unsolved task?
0
votes
0answers
29 views

Schrödinger Equation Simulator: Time Evolution into $\psi=0$ region

I would like to simulate the evolution of $\psi(x,t)$ with $V(x)=0$ for all $x$. As an initial condition, $\psi(x,t=0)$ can be any function, but for all points $x\geq1$, we have $\psi(x,t=0)=0$. The ...
1
vote
0answers
48 views

What numerical methods are being used here to solve the differential equation?

I am having trouble following and understanding the numerical approach to solving for $h(r,t)$ in the following text: How is the integral force balance (10) used to calculate the new pressure ...
2
votes
0answers
17 views

Excited state probability decay in the Monte-Carlo wave function method

When using the Monte-Carlo wave function method to simulate spontaneous decay in a two-level system one typically uses a non-Hermitian Hamiltonian, e.g.: $$H_\mathrm{tot} = H_\mathrm{sys} - i\Gamma ...
0
votes
0answers
17 views

Veto algorithm in particle decays and Monte Carlo techniques

What is the main concept behind Veto algorithm and how does it contribute to efficiency in Monte Carlo methods like when used in designing a parton shower?
1
vote
3answers
55 views

Kinds of orbits in two-body problem

I have a numerical simulation for two bodies moving under gravitational interaction, and some of the outputs are not cohering with my understanding of the theory. My understanding of the theory: In ...
0
votes
0answers
31 views

Modelling Proton Beams using Numerical Methods

I'm attempting to model proton beams/proton therapy using numerical models in MATLAB. I'm having trouble tracking down the correct master equations to use to model beam energy (60-250MeV range) ...
2
votes
2answers
87 views

Solving a fluid dynamics problem numerically, do these assumptions look correct and complete?

I have used Python scripts to numerically solve Laplace's equation (also here) and to solve the diffusion equation in the past. Now I want to write a similar script to solve numerically solve Euler'...
1
vote
0answers
24 views

How to properly align my relaxed molecule onto my gold electrode?

the question is described below since it can be considered a chemistry or physics question: How to translate from one plane to another? originally posted on mathematics SE I am trying to get ...
0
votes
0answers
37 views

Stability condition of a finite difference algorithm

While studying finite difference methods of TDSE I found myself stuck on a reasoning step: The largest possible spatial curvature for the wave function, $\frac{\partial^{2}}{\partial x^{2}} \Psi(x, ...
0
votes
1answer
26 views

Wave-packet backwards emission

I am trying to reproduce the results of a TDSE two wave-packet algorithm described in "Computational Physics: Problem Solving with Python" by Landau, Paez and Bordeianu, in section 22.4 (Wave Packet–...
4
votes
0answers
93 views

Method to build a polyhedral die with given probabilities [closed]

Let's define a die as a polyhedron that, if rolled over a perfect horizontal plane, ends up being in a physically stable unambiguous state labelled $n$. The die has $N$ states. Each state $n$ has a ...
0
votes
0answers
50 views

“Data structure” for a fermion field

I am understanding the path integral formalism of fermion fields. Most textbooks told me that grassmannian integration is only algebaric notation. It shouldn't be understood in a Lebesgue Integral ...
0
votes
1answer
17 views

Tipler & Mosca on “accuracy”

In the Tipler & Mosca textbook we are shown how numerical integration (the Euler's method species of it) is done using a spreadsheet program. The authors then go on to say on page 138 that the ...
0
votes
1answer
59 views

Quantum statistical mechanics formalism

How do we solve a Hamiltonian written in second quantization by using quantum statistical formalism? For example, the following Hamiltonian $$H = \sum_{i=1}^L c_{i+1}^\dagger c_i + h.c.$$ I have ...
0
votes
1answer
16 views

In the limit of an infinite basis, the Hartree Fock orbital gives the true ground state energy for some systems

The system in question is H$_{2}$. Why does the Hartree Fock orbital give true ground state energy for this system?
0
votes
1answer
28 views

Is it possible to have discontinuities in the phase portrait of a dynamical system? If yes what does it really mean?

I've been using Mathematica to draw the phase portrait of a system and I got some jumps along the trajectory. I have a deviation term which might be the reason of this but is it possible to have them ...
0
votes
0answers
18 views

How to use Dyall basis sets for radial wave functions?

I have found the dyall basis set coefficients on the homepage http://dirac.chem.sdu.dk/basisarchives/dyall/ Does anyone in the forum has experience for using for example the "5p" basis set? I only ...
0
votes
1answer
80 views

Ferromagnetism - computational physics

The autocorrelation of the magnetisation is plotted for the Ising model of a ferromagnet. The critical temperature is 2.3 J/k Is this the expected behaviour? as in, it decays super fast for ...
1
vote
0answers
23 views

Numerical method to find the roots of the expected value of a spin 2j state

Currently I am working with finding the solutions for the following problem: I have a unit sphere in which I have n points defined by their polar and azimuthal angles: $\theta_n , \phi_n$. I then do ...
0
votes
1answer
33 views

Structure factor in a homogenous system

I want to calculate the structure factor for a homogenous system. The system that I am dealing with is the results of a Vicsek type model simulation. The structure factor is defined as : $$S(q) = \...
2
votes
1answer
74 views

Do infinities occur when Quantum Field Theory is treated numerically?

What puzzles me regarding QFT and the occuring of infinte integrals when treated in a perturbatative manner is if these infinties would also occur when the theory is treated numerically, maybe even in ...
3
votes
0answers
76 views

Calculate the matrix size for ground states BEC using difference with Gross–Pitaevskii equation

The Ground states BEC at $0$ temperature can be described by Gross–Pitaevskii equation as $(-\frac{\hbar^2}{2m}\nabla^2+V(r)+g|\psi|^2)\psi(r)=\mu\psi(r)$ We limit the BEC in 2D where $V(r)=\frac{1}{...
3
votes
1answer
51 views

Geodesic equation in different coordinate systems

Suppose I have a Schwarzschild metric in Schwarzschild-coordinates and I obtain the geodesic equations for this metric. Suppose I transform the Schwarzschild metric into a different coordinate system,...
0
votes
1answer
59 views

Formally condition and sample distribution of physical field

Is there any formal way to generate samples of physical fields (e.g. electromagnetic field, fluid flow) conditional on observations? The samples would need to satisfy conditions like being continuous, ...
1
vote
0answers
70 views

Numerically Solving EM problems. Book covering: ABS, PML, Near field calcul., LU fact, BicGstab, Pardiso etc

I looking for a book (or two) covering a range of topics: numerical implementation of boundary conditions (PEC, PMC, ABS); perfect matching layer; LU factorisation; numerical solvers and when to use ...
1
vote
1answer
47 views

State of $N$-body system after time $t$ (elastic collision & no gravity)

I am creating a gas particle simulator based game. All nodes (green circles) represent gaseous particles and collide elastically. My algorithm correctly accounts for two-particle collisions, as the ...
0
votes
0answers
35 views

Is it possible to compare two systems in superposition?

Is it possible to compare if two systems in a superposition are equal or not equal to each other, i.e. two systems with two electrons in superposition? At first: Superposition of two electrons (...
1
vote
2answers
60 views

Making sense of phase portrait of simple mass-spring oscillator

I'm new to physics, and I'm having trouble making sense of phase portrait of the following system, $$ m \ddot{x} + k x = 0 $$ whose phase portrait is in here. Since $$ x(t) = \sqrt{\frac{2E}{k}} \...
1
vote
1answer
87 views

State of $N$-body system after time $t$ (under gravity and inelastic collision)

Given the centers of gravity of $n$ spherical bodies of unit mass, $p_1$, $p_2$, ...$p_n$, and assuming perfectly inelastic collisions, how does one find the location of the bodies after time $t$? ...
4
votes
0answers
136 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 ...
1
vote
1answer
43 views

Cross sections in Geant4 [closed]

Does anyone know where I can find the information about cross sections in Geant4? I would like to use my own file with cross section (exported from another code to MC simulations), but I cannot find ...
2
votes
1answer
52 views

Where's the Database in Grover's Algorithm

I am a little confused by parts of Quantum Computation and Quantum Information by Nielsen and Chuang on Grover's algorithm: Grover's algorithm searches a number of quantum states for a "marked ...
0
votes
0answers
33 views

Diffusion between unequally spaced points?

I believe what I have is a rather simple issue at heart: assume I have a number of $M$ scattered points in an $N$-dimensional space $\mathbb{R}^N$. Each of these points has coordinates $x \in \mathbb{...
1
vote
0answers
69 views

Fourier transforms and convolution for finding Fraunhofer diffraction of compound objects: how does it work?

I've been exposed to this notion in multiple classes (namely math and physics) but can't find any details about how one would actually calculate something using this principle: Diffraction in optics ...
-4
votes
1answer
75 views

Brute-forcing the theory of everything [closed]

If brute force doesn't work, you're probably just not using enough of it. That's especially true for guessing combinations of stuff, like characters in a password. Assuming some combination of ...
0
votes
1answer
87 views

Can anyone tell me how can draw shadow of black hole like in presented in Intersteller movie? Is there any code for it in Mathematica or in Python? [closed]

Equation of motion for photon $$ \Sigma \frac{dt}{d\lambda} = aL\left(1-\frac{r^2+a^2}{\Delta}\right) + \omega\left(\frac{\left(r^2+a^2\right)^2}{\Delta}-a^2 \sin ^2\theta\right)\ , $$ $$ \Sigma\frac{...
2
votes
2answers
93 views

Wave simulation without reflection on the boundaries [duplicate]

I would like to numerically simulate a wave (let's say in a string) with different boundary conditions: Fixed endpoints Periodic Boundless $\varphi(x, t)$ is the value of the wave (vertical ...
0
votes
0answers
51 views

difficulty of lid driven cavity simulation

Many people do lid driven cavity simulation, but most people don't get correct results. Many wrong attempts give an overall spinning motion of the fluid, without corner vortices. What's the reason of ...
0
votes
1answer
35 views

FEM: Distributed loads over adjacent quadratic bar elements

I am an electrical engineering student trying to teach myself Finite Element Methods (FEM) through a couple of textbooks and independent study. While I believe that I understand the basic ideas ...
2
votes
2answers
76 views

How can I simulate a ground state degenerate system numerically?

I'm using numerical method like DMRG to simulate ground state of correlated systems. But the degeneracy of the ground state has long bothered me: When degeneracy exists the ground state isn't unique. ...
-1
votes
2answers
98 views

Can we create new physics through moderately brute force computing? [closed]

So my argument for this is that the expansion of knowledge in any field of physics depends on what is previously known, and what we physicists express or knowledge as equations. So here's what I ...
-2
votes
1answer
51 views

Would any continuous model of the universe have/be based on hypercomputational laws?

I've read that when Turing-Church thesis is applied to the universe and physics, one of the three interpretations that we can use and is defended by some important physicists is that: "The universe ...
1
vote
2answers
79 views

Clarification on the Lid-Driven Cavity Problem in CFD

I need some clarifications on The Lid-Driven Cavity Problem. What does it actually mean? I know cavities are bubbles created when a fluid moves through liquid in low pressure zones, but what does the ...
1
vote
1answer
21 views

Self consistent calculations in quantum well. Mixing by electron density?

I'm challenging the problem of calculating energy structure of InAs/GaAs quantum well. One part of the task is to perform self consistent calculations in order to include potential that comes from ...