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.

learn more… | top users | synonyms (1)

8
votes
0answers
509 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 ...
5
votes
0answers
113 views

Computational scaling of quantum and classical Monte Carlo algorithms

How does the computational complexity of finding an equilibrium thermal state for a given Hamiltonian at a given temperature scale with system size under classical and quantum Monte Carlo? I know ...
5
votes
0answers
192 views

Numerical Solution of the Propagation-Dispersion equation

I have asked this question on Computational Science and also on Mathoverflow, but no satisfactory answers so far. I thought maybe the physics community could shed some insight on the issue. I am ...
5
votes
0answers
710 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 ...
4
votes
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 ...
4
votes
0answers
1k 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} -\frac{\hbar^{2}}...
3
votes
0answers
42 views

Calculating 2 particle Partial Trace for Density Matrix in Zeeman basis for a large number of Spins

I want to trace out all spins but 2 from a density matrix in the zeeman basis for N spins. For N=3 for example I would have the basisvectors: $ |S=1.5, m=-1.5\rangle =|000\rangle, |S=1.5, m=1.5\rangle ...
3
votes
0answers
58 views

Simulation of plasma in tokamak

I am reading some papers on numerical algorithms for simulation of plasma in the context of nuclear fusion in a tokamak. I am getting a little lost as there is a huge number of references, and it is ...
3
votes
0answers
33 views

The definition of fidelity for fermion

The definition of fidelity for two mixed ensembles is $F=Tr\sqrt{\sqrt{\rho_1}\rho_2\sqrt{\rho_1}}$. Now I came across a problem in numerical calculation, Systems A,B are identical, but attached to ...
3
votes
0answers
47 views

How are boundary consitions implemented correctly in time dependent hydrodynamics?

I posted this question more than one year ago and got an answer recently. This answer looks good to me, but indicates that something is wrong in my original approach to the problem. Can someone tell ...
3
votes
0answers
142 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
votes
0answers
71 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
votes
0answers
96 views

Non-linear Wave Equation - Numerical Methods

Motivation: I'm working with a highly non-linear spherical wave-like equation (second order PDE). The equation can be written on the form $$\ddot{u} = f(t, \dot{u},\dot{u}',u',u'')$$ where $'=\frac{...
3
votes
0answers
151 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
votes
0answers
1k 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 ...
2
votes
0answers
19 views

Boundary conditions and density when using smoothed particle hydrodynamics/corrective smoothed particle method for two-temperature models

I am trying to solve the dual-hyperbolic two temperature model (TTM) using a modified smoothed particle hydrodynamics (SPH) scheme known as CSPM (corrective smoothed particle method), as demonstrated ...
2
votes
0answers
52 views

Efficient Method for Multiplying Angular Momentum Operators

I'm doing a calculation that involves canonical symmetrization of angular momentum. For example: $H_{\text{classical}} = J_x J_y \rightarrow \hat{H}_{\text{quantum}} = \frac{1}{2}(\hat{J_x}\cdot \...
2
votes
0answers
20 views

Derivation of generation of time between two subsequent particle enters into computational domain

I have problem with understanding derivation of one equation in following problem. You have 1D computational domain (it is not 1D but because it is symmetrical and we are watching only radial ...
2
votes
0answers
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. ...
2
votes
0answers
65 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}(\...
2
votes
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 ...
2
votes
0answers
66 views

How to let Pythia to output the complete event record in LHEF or StDHep format?

I am currently using Pythia 6.4 to simulate some processes (I do not have the intention to upgrade to 8). Now, I need Pythia to output its event record in the format of LHEF or StDHeP. I accidently ...
2
votes
0answers
352 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: http://scicomp.stackexchange.com/questions/...
2
votes
0answers
77 views

Are there resources for simulating and/or theoretically describing solitons?

Recently there are striking new ideas emerging on "lower level" dynamics with respect to quantum mechanics involving fluid mechanics principles, including hints of soliton-like aspects to particle ...
2
votes
0answers
68 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: $$ \tag{...
2
votes
0answers
99 views

Modelling gravitational potential of a galaxy

I am interested in modelling the gravitational potential of a disc-shaped galaxy with radius $R$, i.e. solving the 2D Poisson equation numerically by Gauss-Seidel relaxation: $$\nabla^2 \phi = 4\pi G ...
2
votes
0answers
260 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 ...
2
votes
0answers
39 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
votes
0answers
451 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 ...
2
votes
0answers
66 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 ...
1
vote
0answers
17 views

Capturing superfluid condensation with exact diagonalization

Doing exact diagonalization on bosonic systems is tricky, because the possibility of multiple occupancy means that even the single-site Hilbert space is infinite-dimensional. It's my understanding ...
1
vote
0answers
73 views

How to plot numerically the wave functions according to the Hamiltonian?

It is often difficult to analytically solve the Schrodinger equation, and so we need to obtain a solution numerically. An example plot is shown below. Here, the wave functions for a three junction ...
1
vote
0answers
14 views

Modelling a flow due to an oscillating hemisphere?

Say I have a long cylinder filled with air, closed at one end and open at the other. Now say I place a compressible hemisphere at the closed end and make it oscillate (compression and expansion of the ...
1
vote
0answers
23 views

Master curve of the 3D Ising model

I am currently doing some grand canonical Monte Carlo simulations for LJ particles and my professor has asked me to map the normalized probability distribution of density on to a master curve of the ...
1
vote
0answers
29 views

Numerically integrate equations of motion with noise

Consider the equations of motion $$\begin{cases} \dot{x}(t) & = v(t) \\ \dot{v}(t) & = -\frac{\lambda}{m} v(t) + \frac{1}{m}F^{c}(x(t)) = a(x(t), v(t)) \end{cases},$$ where $x$ is the ...
1
vote
0answers
24 views

How is time evolution done in numerical GR?

Suppose we're simulating what happens when a fairly massive object falls into a black hole. Say the object starts far away, so that the initial condition is that the metric is the Schwarzschild metric ...
1
vote
0answers
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 ...
1
vote
0answers
38 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 ...
1
vote
0answers
38 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: $...
1
vote
0answers
24 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 ...
1
vote
0answers
77 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 ...
1
vote
0answers
93 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 ...
1
vote
0answers
42 views

Computational method for finding edge states?

I am actually interested to learn how to calculate edge states in 1D topological systems using computational methods, Q. can anyone tell me which method is best suited and easy to calculate edge ...
1
vote
0answers
120 views

What are the differences between the Jetphox, Pythia and Herwig event generators?

I know Jetphox is a parton-level event NLO generator program. But I want to know more about other generator programs such as Pythia and Herwig. What are the differences? I am undergraduate student so ...
1
vote
0answers
101 views

Selecting physical solutions in numerical eigenvalue problems

I try to solve a certain time-independent Schrodinger equation numerically, using the method of finite differences. My boundary conditions are such that the finite difference method gives me an ...
1
vote
0answers
47 views

Is there a numerical calculation for black hole - neutron star merges?

I think it might be even a more frequent event as the black hole merges. It would be similar to the black hole merges in the gravitational wave spectrum, but it could have a very clear neutrino and ...
1
vote
0answers
101 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, ...
1
vote
0answers
43 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 ...
1
vote
0answers
120 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 ...
1
vote
0answers
144 views

Numerical Solution of 1D Boltzmann Transport Equation

I need to solve the one-dimensional Boltzmann transport equation in a semiconductor numerically, and I want to take a deterministic approach toward the problem (i.e. not use Monte-Carlo or similar non-...