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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421 views

Intuition for when the replica trick should work and why it works

I am a graduate student in mathematics working in probability (without a very good background in physics honestly) and I've started to see arguments based on computations derived from the replica ...
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98 views

The use of Artificial Intelligence in physics resarch

I have been reading about a machine that observed a double pendulum and created equations that both described its motion and associated conservation laws. The authors claims: We have developed a ...
5
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0answers
586 views

Interpretation of Stiffness Matrix and Mass Matrix in Finite Element Method

I would like to have a general interpretation of the coefficients of the stiffness matrix that appears in FEM. For instance if we are solving a linear elasticity problem and we modelize the relation ...
3
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0answers
113 views

black body simulation

black body radiation is typically understood from Planck's argument of light resonance in a box, from which the density of states is computed. Now, suppose I want to simulate a black body ...
3
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0answers
62 views

Textbooks on algorithms for the perturbative calculation of High energy physics

For the perturbative calculation of High energy physics, I have known some packages such as FeynArts, FeynCalc, MadGraph, CompHEP, GiNaC, and so on. But I am wondering whether there exists a textbook ...
3
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0answers
190 views

What is the probability of quantum tunneling occurring in this CPU?

You may have noticed over the last few years that Moore's law is no longer applying to the real world. This observation states that over the history of computing hardware, the number of transistors on ...
3
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0answers
793 views

Numerical problem in solving the Bogoliubov de Gennes equations- methods to solve?

I am trying to solve an assignment on solving the Bogoliubov de Gennes equations self-consistently in Matlab. BdG equations in 1-Dimension are as follows:- $$\left(\begin{array}{cc} ...
3
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0answers
135 views

Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model

In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
3
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0answers
663 views

Comparison of different ab-initio codes

One may find on the web a lot of different computational packages to perform "ab-initio" calculations of electron structure of the solids. Usually, the documentation is not quite transparent about the ...
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46 views

Precession of Mercury (Python simulation)

I was trying to simulate the precession of Mercury based on the perturbed solution, and my questions about its implementation in python can be seen here: ...
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0answers
31 views

How can the fictitious mass in the Car-Parrinello method reproduce the “real” dynamics?

In the Car-Parrinello method, to solve simultaneously the classical equations of motion for the atoms and the Kohn-Sham equations for the electrons, the following effective Lagrangian is used: $$ ...
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31 views

Mass scaling in molecular dynamics

I've noticed some authors scale the mass of particles in molecular dynamics simulations while leaving the force field parameters the same in order to achieve materials of different densities. Does ...
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0answers
127 views

How to compute matsubara frequency summation over computer?

Matsubara frequency sum usually takes the following form: $S_\eta = \frac{1}{\beta}\sum_{i\omega_n} g(i\omega_n).$ But in my problem, $g(i\omega_n)$ is a lengthy expression, which can not be ...
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30 views

Coefficients and Parameters for contracted Gaussian basis sets

This is a repost from Chemistry.stackexchange in the hopes that someone here will be able to help me. Any help at all would be greatly appreciated. As far as I understand, an STO-NG contracted ...
2
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0answers
59 views

Trotter splitting and entanglement entropy

I have heard that a numerical solution to the Schrodinger equation using the Trotter splitting formula for a many-body Hamiltonian can cause an artificial increase in the entanglement entropy. I was ...
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0answers
32 views

Mixed spin Ising Model

As we know ferrimagnets can be modeled by the Ising model. I came across this equation in "Compensation Temperature of the Mixed-Spin Ising Model on the Hexagonal Lattice" by W. Figueiredo, M. Godoy, ...
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52 views

Tight binding model in a magnetic field

The standard way to treat a tight binding method in a magnetic is to replace the hopping matrix element: $t_{i,j}\rightarrow e^{i\int_i^j\mathbf{A(x)}.d\mathbf{x}}$ the so called "Peierls ...
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0answers
23 views

Introduction material for lattice field simulation

I am looking for introductory material of lattice field theory simulation. It is better start from simple example (e.g. \phi^4) and include some source code. Is there any on-line or book which is ...
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53 views

Ising model Monte Carlo simulations in 4D and 5D

I'm going to be simulating the Ising Model in 4D and above to calculate spin-spin correlations and critical exponents and am wondering how to tackle this algorithmically. For example, in 1D, use an ...
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0answers
177 views

Problems while numerically computing band structure using k.p theory

I want to use k.p theory to numerically compute the band structure of a bulk semiconductor. The band I like to include are the lowest conduction band (cb), the heavy-hole (hh), the light-hole (lh) and ...
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0answers
25 views

Cellular automata and time T

Reading around about various CA models I saw that there are even those who are following the track to provide a single mechanicist model of the universe. For example Gerard van 't Hooft claims that ...
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0answers
51 views

Does Planck's constant imply limits to computing *results*

... I don't mean quantum effects limiting hardware fabrication sizing. Such small scales have for some time exhibited issues. Rather, along the lines of imagining the smallest possible divisions of ...
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0answers
34 views

Computer coding of Perdew Burke and Ernzerho (PBE) method

I have been assigned the task to write a computer code to implement the Perdew Burke and Ernzerhof (PBE) method. Does anyone know a good reference which can make the coding of this method easier?
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330 views

Hysteresis Curve and how to implement it using Preisach model or other models

As a homework I need to draw a hysteresis curve (preferably an interactive one) using Matlab or any other programming language. The problem is I have trouble finding a good algorithm to do so. I need ...
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0answers
73 views

Application of wavelets in computational electromagnetics

I am a first-year graduate student (electrical eng.); wavelets is one of the courses that I am taking presently. As part of the course, I plan to explore application of wavelets in computational ...
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0answers
96 views

How does the Lennard Jones Potential changes for interaction between particles of different sizes?

I am interested in incorporating a Lennard-Jones potential in a simulation. When the interaction only involves the same type of particle, with same characteristics, we can use reduced units, scaling ...
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0answers
109 views

Gerstner Wave Formula to Vertex information $(x,y,z)$

I have created a program, that draws a plane mesh, and allows to me edit or animate all the separate vertices along it. The idea behind it, is for me to be able to create a gridMesh based wave ...
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0answers
509 views

Is Bremermann's limit redundant with Landauer's limit for all practical purposes?

Trying to understand the physical limits to computation, I notice that among these we have two types of limits that constrain the minimum allowable energy for a computation. Limits that constrain ...
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0answers
54 views

Find out ground sates for large 2D classical spin model

Reaching the ground state of a large 2D classical spin model (e.g. classical Heisenberg model) might be a relatively difficult task while using conventional "flip/reject" Monte Carlo method. The ...
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0answers
298 views

What is the drag coefficient of an open wedge?

To check my two dimensional CFD calculation I am looking for reference data on the drag coefficient of an open wedge. The geometry is shown below, together with the flow direction. I have found ...
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0answers
170 views

RGEs of the MSSM - problems with Mathematica

I'm having some troubles with the trilinear soft couplings of the MSSM RGEs. I've used the ones written in Martin's supersymmetry primer and I run them using mathematica, if I do so without taking ...
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0answers
3k views

How to calculate the velocity of fluid at the outlet when density and the pressure drop are known?

I have a U- like pipe. Its inlet has atmospheric pressure $p_o=10^{5} \, Pa$. Vacuum is applied to the other end with a pressure gradient $\nabla p_v=-30 \cdot 10^{3} \, kPa/s$. The total time of the ...
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0answers
232 views

2D quantum well energy spectrum (analytical vs numerical)

I am trying to understand the energy spectrum difference between the analytical and the approximated solution for a quantum well. The particle is inside a box with domain $\Omega=(0,0)$X$(1,1)$. For ...
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0answers
34 views

What exactly is closed orbit theory and what assumptions go into it?

I am just beginning a research project on the study of closed orbits, specifically as related to hydrogen, and I wanted a little bit more information on what exactly makes something a "closed orbit". ...
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31 views

What is the largest atom with a reliable configuration-interaction (CI) calculation?

The simplest approximation for calculating the ground state of an atom is the Hartree-Fock approximation. To get accurate result for the ground state energy, one has to do configuration-interaction ...
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0answers
26 views

Q: Any standard terminology for “gold standard” Monte Carlo solutions

The "standard" way in our field to compute scattering statistics in wave propagation problems is via a "deterministic" wave prop code operating in a Monte Carlo context where we iterate over many ...
0
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0answers
21 views

What is the difference between finite displacement and linear response for calculating vibrational properties?

I see these concepts appearing in the context of calculating phonons and other vibrational properties, but I can't find a concrete explanation of the differences between linear response (DFPT) and the ...
0
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0answers
46 views

Ising Model 2D Correlation Length

I'm using Metropolis and Wolff Clustering algorithms to estimate the spin-spin correlation function $$<s_os_r>$$ I know that this is related to the correlation length but how do we determine ...
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0answers
39 views

Why are functional representations of systems important in physics or computational physics?

This was an addendum to a previous question I asked, but I figured I should make it it's own discussion. Assuming I am able derive a functional representation for any dynamical system (dissipative, ...
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18 views

Why breakdown voltage decreases with increasing FWHM of an asperity?

I am running a simulation for a dielectric breakdown. I am getting breakdown voltage decreases with FWHM, which does not make sense as field enhancement is higher for a small width. Simulations solve ...
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0answers
25 views

Optimize locations of vertices and edge length using physics without simulation

I have a directed graph with set of vertices and edges. Each vertices don't have a position coordinate to be displayed on 2D computer screen. I want to add unique position coordinate to each vertices ...
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0answers
25 views

Adams-Moulton and BDF methods

1.What are the differences between Adams-Moulton and BDF methods. Which one is better and which one computes the solution faster? I think Adams-Moulton is a better method as it can get to the ...
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0answers
72 views

How to calculate a Mooney-Rivlin material

Well, I'm working on a fsi (fluid-solid/structure interaction) model. I've got ready the fluid part, now I need to get ready the solid part. Since I'm working with tissues, I need to use an ...
0
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0answers
38 views

need some references in molecular dynamics simulation

I Just start we a new model on my project and I will need to work with Molecular dynamic simulation. I have to simulate dynamics of many filament inside a network (actomyosin network).The problem is ...
0
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0answers
26 views

Electron scattering with CSDA simulation

I am currently in the process of writing simulation code for a "computational physics lab course" and in the present case the task is to simulate the trajectories of 20 [MeV] electrons impinging on a ...
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0answers
49 views

Examples of application of detour matrices in physics?

Are there any good examples of application of detour matrices in physics?
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0answers
45 views

Poisson equation solver with specific boundary condition

I want to solve 2d Poisson equation with this Boundary conditions below $$u(-5,y) = 0 , \\ \frac{\partial u(x,y)}{ \partial x} = 0 \,\,{\rm at}\,\, x = -5\\ u(x,-5) = u(x,5)$$ Now my question is ...
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0answers
26 views

Verlet timestep

I am using velocity Verlet in molecular dynamics. Is just a simple question, if a simulation using time-step femtosecond, in velocity Verlet is just necessary $dt = 10^{-15}$ to use femtosecond?
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81 views

Need help simulating a fan

I'm trying to write some code to approximately simulate a number fans in an arbitrarily shaped room. I'm not real strong in physics, and could use some help. If it helps I'm not interested in fine ...
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0answers
43 views

Should particles in Smoothed Particle Hydrodynamics (SPH) always move during a simulation?

Or can they just be used as an interpolation points and use some other "transported property" which are just evolved and propagated from boundary conditions like for eg. heat conduction through a ...