The numerics tag has no wiki summary.
2
votes
0answers
28 views
Monte Carlo for Random Bond Ising ferromagnet
The set-up:
Consider the Ising model on an $L \times L$ square lattice, where the coupling of each bond is chosen to be $+J$ (ferromagnetic) with probability $(1-p)$ and $-J$ (antiferromagnetic) with ...
2
votes
1answer
31 views
Electric current streamlines in induction cooking vessel
I am looking for a plot of the typical streamlines of the electric induced currents ("eddy currents") in a induction cooking vessel.
How can one theoretically predict the streamlines? How is it ...
4
votes
2answers
88 views
Solve the angular part of Schrodinger equation numerically
I would like to solve the angular part (the one for what is usually called the $\theta$ angle) of a time-independent 3D Schrodinger equation
$$
\frac{\mathrm{d}}{\mathrm{d}x}\left[ (1-x^2) ...
0
votes
0answers
33 views
Irregular events within an otherwise cyclic time series
(I have asked the same question on math.stackexchange, but I figured that physicists might actually be more likely to have encountered the same problem before.)
I am considering a time series with a ...
1
vote
1answer
94 views
Superconducting gap, temperature
Tinkham (page 63) states that the temperature dependence of the gap energy of a superconductor $\Delta(T)$ can be calculated using the following integral: http://i45.tinypic.com/w1s13t.png
How can ...
1
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0answers
78 views
neutron transport approximations for nuclear rocket modelling
I'm pretty ignorant regarding neutron and nuclear transport modelling, but i'm interested in trying to pursue it for a particular pet project. It regards modelling of nuclear reactions like those ...
2
votes
2answers
132 views
numerical formulation of Dirac equation plus electromagnetic field
I have the following equations describing the electron field in a (classic) electromagnetic field:
$$ c\left(\alpha _i\right.{\cdot (P - q(A + A_b) + \beta mc) \psi = E \psi } $$
where $A_b$ is ...
3
votes
3answers
223 views
Can a wavefunction be solved to any arbitrary precision, given enough computer time?
I learned that the wavefunction for the hydrogen atom can be solved analytically (we did the derivation in class), but that for more complicated atoms it is "impossible" to solve and that only ...
-4
votes
3answers
117 views
How to recognize broken candies from whole ones [closed]
Let's say I have a bag full of sugar candy. Some will be whole, some will be dent, some will be broken (in part, or half, etc).
Let's say I have a device with an input box where I empty the bag, and ...
0
votes
0answers
75 views
Coupled decay behavior? [closed]
I solved the following "coupled" ODE numerically, whit forward Euler scheme:
$$
\frac{\text{d}N_a}{\text{d}t} = -\frac{N_a}{\tau_a}
$$
$$
\frac{\text{d}N_b}{\text{d}t} = ...
4
votes
0answers
345 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 ...
0
votes
1answer
393 views
Calculating Kramers-Kronig using Mathematica
First of all, I know there is a Mathematica group in beta, but I don't think the problem of the following is directly a Mathematica issue.
I am trying to calculate the change of the refractive index ...
1
vote
1answer
168 views
Numerical algorithms to generate a random wavefunction from a thermal ensemble
I am seeking an algorithm to generate a random wavefunction = $\sum {c_i |\varphi _i\rangle }$ from a thermal ensemble, whose density matrix $\rho \sim e^{-\beta H}$, without the need to diagonalize ...
12
votes
2answers
50 views
Numerical Analysis of Elliptic PDEs
I am looking for an elementary reference regarding issues of stability in numerical analysis of non-linear elliptic PDEs, particularly using the finite difference method (but something more ...
1
vote
1answer
203 views
Transparent boundary condition. Beam propagation method
I am interested in the finite-difference beam propagation method and its applications. I try to solve the Helmholtz equation. At first, i would like to solve numerically it for the easiest case, ...
3
votes
1answer
213 views
Numeric method to calculate the charge distribution on a conducting surface?
If I have an arbitrary (closed?) conducting surface and a nearby charge density, is there a simple numeric way of computing the induced charge distribution on the surface?
3
votes
3answers
309 views
Numerical software to manipulate a light beam in its plane wave representation?
Any light field can be expressed as a sum of plane waves. Such an ensemble of plane waves is called the plane wave spectrum of the light field. The plane wave spectrum is the Fourier transform of the ...
14
votes
1answer
185 views
Why isn't the Gear predictor-corrector algorithm for integration of the equations of motion symplectic?
Okumura et al., J. Chem. Phys. 2007 states that the Gear predictor-corrector integration scheme, used in particular in some molecular dynamics packages for the dynamics of rigid bodies using ...
2
votes
1answer
440 views
Physics needed to build a top down billiards game [duplicate]
Possible Duplicate:
How are these balls reflected after they hit each other?
I was wondering what sort of physics equations would I need in order to build a top down billiards game? I tried ...
3
votes
1answer
122 views
Smoothed particle hydrodynamics in cosmological N-body simulations
What is the role of smoothed particle hydrodynamics (SPH) in cosmological N-body simulations like the Millenium Run (performed with Gadget-2)?
8
votes
1answer
2k views
Solving Schrödinger's equation with Crank-Nicolson method
I am trying to numerically solve Schrödinger's equation with Cayley's expansion ($\hbar=1$)
$$\psi(x,t+\Delta t)=e^{-i H\Delta t}\psi(x,t)\approx\frac{1-\frac{1}{2}i H\Delta t}{1+\frac{1}{2}i H\Delta ...
2
votes
0answers
48 views
Degenerated Anderson Model Simulation
I'm trying to simulate the degenerative Anderson model. So depending on an energy difference first orbital and afterwards spin magnetism occurs. First i try to solve an easier ansatz with a limitation ...
1
vote
2answers
259 views
History of the use of the concept of phase space in engineering
Engineering textbooks constantly use the concept of 'phase space' (see e.g. http://www.cs.cmu.edu/~baraff/sigcourse/notesc.pdf). That is, they think of the state of a mechanical system as a ...
2
votes
1answer
488 views
Using Fourier Transforms to Solve Systems with springs of high frequency
I'm trying to numerically solve the differential equations of motion in a system with multiple springs of very high frequency. Because the solution is often a combination of rapidly-oscillating sine ...
10
votes
5answers
1k views
Basic mechanics problems, unsolvable by brute-force numerical integration
I'm looking for simple problems in theoretical mechanics that are impossible or unreasonably difficult to solve by means of "brute-force" numerical integration of Newton or Euler-lagrange equations.
...
11
votes
5answers
466 views
Binary Black Hole Solution of General Relativity?
This is rather a technical question for experts in General Relativity. An accessible link would be an accepable answer, although any additional discussion is welcome.
GR has well known solutions ...
4
votes
1answer
427 views
Mathematica to help for an Hamiltonian problem
I have an Hamiltonian problem whose 2D phase space exhibit islands of stability (elliptic fixed points).
I can calculate the area of these islands in some cases, but for other cases I would like to ...
