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.
16
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5answers
429 views
What do theoretical physicists need from computer scientists?
I recently co-authored a paper (not online yet unfortunately) with some chemists that essentially provided answers to the question, "What do chemists need from computer scientists?" This included the ...
13
votes
4answers
430 views
Home-made lattice calculation?
The topic of Lattice QCD or Lattice gauge theory or even Lattice field theory is quite old now. And the main reason for the interest in the topic is the ability to calculate nonperturbative stuff on a ...
10
votes
1answer
79 views
Consideration of static atomic displacements in electronic structure calculations
I am hoping to discuss some details of electronic structure calculations. I am not an expert on this topic, so please forgive any abuse of terminology. It is my understanding that first principles ...
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 ...
8
votes
1answer
1k views
What programming languages would be helpful for a physicist to know? [closed]
From the vantage point of a physicist and the kind of problems he would like a computer program to solve, what are the essential programming languages that a physicist should know.
I know C++ and I ...
8
votes
1answer
263 views
How do you simulate chiral gauge theories on a computer?
David Tong and Lubos Motl have argued that our universe can't possibly be a digital computer simulation because chiral gauge theories can't be discretized, and the Standard Model is a chiral gauge ...
7
votes
5answers
468 views
How useful is programming in physics?
I have been wondering recently how useful programming is to a physicist. It seems fairly useful (simulations are a lot cheaper than the actual thing in many cases) in some areas (say space programs), ...
7
votes
4answers
682 views
Dirac equation on general geometries?
I have a numerical method for computing solutions to the Dirac equation for a spin 1/2 particle constrained to an arbitrary surface and am interested in finding applications where the configuration ...
7
votes
2answers
798 views
Should acceleration be included in state vector of a Kalman filter?
I'm developing (actually adopting existing solution) a Kalman filter to model motion of a vehicle (UAV or automobile). The state vector will include position, velocity, and, possibly, acceleration.
...
6
votes
2answers
788 views
Physics of simple collisions
I'm building a physics simulator for a graphics course, and so far I have it implementing gravitational and Coulomb forces. I want to add collisions next, but I'm not exactly sure how to go about ...
6
votes
1answer
437 views
What is the status of applying numerical analysis to QM/QFT problems
This is something I don't ever seem to hear about, except regarding QCD ("lattice QCD"). What about QED? Is numerical integration always inferior to hand-calculating Feynman diagrams in perturbation ...
5
votes
2answers
2k views
Solving one dimensional Schrodinger equation with finite difference method
Consider the one-dimensional Schrodinger equation
$$-\frac{1}{2}D^2 \psi(x)+V(x)\psi(x)=E\psi(x)$$
where $D^2=\dfrac{d^2}{dx^2},V(x)=-\dfrac{1}{|x|}$.
I want to calculate the ground state ...
5
votes
3answers
301 views
Supergravity calculation using computer algebra system in early days
I was having a look at the original paper on supergravity by Ferrara, Freedman and van Nieuwenhuizen available here. The abstract has an interesting line saying that
Added note: This term has now ...
5
votes
2answers
221 views
In condensed matter simulations, how is particle number density computed in practice?
I have been reading a recent paper. In it, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, in which liquid resides between the parallel-plate electrodes. ...
5
votes
1answer
166 views
What equation describes the electrostatic potential in these circumstances?
I have a solver for Poisson's equation and it works nicely. It uses finite differences. It works in the presence of multiple dielectrics.
It also solves the Poisson Boltzmann equation. That is, fixed ...
5
votes
3answers
210 views
Simulate a physical impact of objects made of finite, small elements
I want to simulate an impact between two bodies according to gravity, and eventually considering other forces to stick matter together. I'd like to use python to do this, but I am open to ...
5
votes
2answers
263 views
Can the Metropolis-Hastings algorithm be generalized to quantum systems?
The Metropolis-Hastings algorithm is an efficient way of simulating classical ensembles using the Monte Carlo method. Is there a generalization of this algorithm to quantum systems? What I DON'T have ...
5
votes
3answers
268 views
How to include random force in the simulation (Classical Molecular Dynamics)
I need to implement a random force in my code according to the fluctuation dissipation theorem. I have a Gaussian distribution function ready width average 0 and distribution 1 and I know I need to ...
4
votes
3answers
835 views
Why is the canonical ($NVT$) ensemble often used for (classical) molecular dynamics (MD) simulations?
Molecular dynamics (MD) simulation is a common approach to the (classical) many-body problem. It relies on integration of Newton's equations of motion to simulate the trajectories of many (e.g., ...
4
votes
3answers
342 views
Nanorobots. What stops us from producing them yet?
If we can already predicts accuratelly motion on molecular levels, what stops us from developing small robots to, for instance, navigate through our blood vessels looking for cancerous cells and ...
4
votes
2answers
557 views
Radial Schrodinger equation with inverse power law potential
Recently I read a paper about solving radial Schrodinger equation with inverse power law potential.
Consider the radial Schrodinger equation(simply set $\mu=\hbar=1$):
...
4
votes
1answer
108 views
Using the monte carlo method to compute the magnetic field of a curent carrying loop
I have written a program in cpp that computes the magnetic field at a point from a current carrying loop. It uses the biot savart law and the monte carlo technique to carry out the integral. The ...
4
votes
2answers
673 views
On numerically solving the Schrödinger equation
I just read a paper 'A pocket calculator determination of energy eigenvalues' by J Killingbeck
(1979).
Link: http://iopscience.iop.org/0305-4470/10/6/001
I have some questions about section 2.
Why ...
4
votes
0answers
346 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
votes
3answers
255 views
Future Computer Performance
Moore's law has succesfully predicted up to now that integrated circuit transister density doubles every two years. However, computer performance is dependent on additional factors like architecture, ...
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 ...
3
votes
2answers
449 views
Can cellular automata be reconcilied with quantum mechanics?
CAs are deterministic representations of the universe, which, according to the Bell's inequality are not entirely accurate. Cells interact "locally" (only with the closest neighbours), while quantum ...
3
votes
2answers
148 views
Difference between Monte Carlo and Quantum Monte Carlo methods?
What are the differences between Classical Monte Carlo methods and Quantum Monte Carlo methods in condensed matter physics? If one want to study strongly correlated systems with Quantum Monte Carlo ...
3
votes
1answer
90 views
buiding circuits from color superconductors
caveat: the sort of exotic matter engineering in here is currently beyond the reach of our technology, but, that having been said:
Has their been any research on building models of these sorts of ...
3
votes
2answers
320 views
Mixed conductive and convective heat transfer
I want to make a finite element analysis of a cold airflow through warmer pipes. In particular I want to see how the pipes cool down and the air heats up, as it travels through the pipes. Wich are the ...
3
votes
1answer
188 views
Industry application of computational quantum mechanics?
I was wondering if anybody knew of an industry application of computational quantum mechanics. For example, the efficient placement of circuit elements on a PCB is in part motivated by classical FDTD ...
3
votes
2answers
219 views
Can I use imaginary time propagation for many-body problems?
There are various ways to numerically find the ground state energy and wavefunction of a many-body Hamiltonian. You can diagonalize the Hamiltonian and pick out the lowest eigenstate, or you use ...
3
votes
3answers
332 views
Adding rotation to internal coordinates
I'm optimizing the geometry of a system composed of several interacting masses (a molecule). The energy of the system depends on the relative position of the masses, and all velocities are zero.
In a ...
3
votes
1answer
349 views
Numerical computation of the Rayleigh-Lamb curves
The Rayleigh-Lamb equations:
$$\frac{\tan (pd)}{\tan (qd)}=-\left[\frac{4k^2pq}{\left(k^2-q^2\right)^2}\right]^{\pm 1}$$
(two equations, one with the +1 exponent and the other with the -1 exponent) ...
3
votes
1answer
214 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
1answer
98 views
How to determine predicted CP violation for a given SUSY point?
I'm currently studying at the spectra of some supersymmetric models, and would like to know whether the parameter points I'm looking at are ruled out due to excessive CP violation.
I am using SPheno, ...
3
votes
1answer
109 views
Diifference between real time propagation and imaginary time propagation?
Suppose I want to solve Nonlinear Schrodinger equation using imaginary time propagation to get the ground state solution. I choose $t = - i t$, and then solve the equation using split step Crank ...
3
votes
1answer
172 views
Using Relaxation Method to Model Negative Dielectrics in an electric field?
How can you use the relaxation method to model negative dielectrics?
The relaxation method is usually used to model electrostatics problems but negative dielectrics are only see in dynamic systems.
...
3
votes
0answers
48 views
The etymology of “Umbrella Sampling” [migrated]
I am just wondering where the term Umbrella Sampling came from. Is there another meaning of literal "umbrella" in physics or mathematics?
2
votes
4answers
163 views
Computer Science Modeling of Physical World
I am curious what efforts have been made to date to define virtual computer worlds based on the physics we know in the real world?
I think it would be awesome to say start off with an atom defining ...
2
votes
2answers
131 views
Computational Science involve programming? [closed]
I read what is computational science in Wikipedia but the explanation and understanding are not very clear.
So, I could you please give a simple example computational science project and what all ...
2
votes
1answer
131 views
If the graph isomorphism problem can't be solved in polynomial time, do spin-networks in loop quantum gravity violate the Church-Turing thesis?
If the graph isomorphism problem can't be solved in polynomial time, do spin-networks in loop quantum gravity violate the Church-Turing thesis? To determine whether or not two graphs are isomorphic ...
2
votes
2answers
234 views
Why can't we set the lattice spacing 'a' in lattice QCD?
My question is to do with lattice QCD. In the lattice action there is a parameter, 'a', the lattice spacing in physical units.
However, if we want to generate a configuration with a certain lattice ...
2
votes
1answer
78 views
What states are satisfying an entropic area law and why do they satisfy it? More specificly why do matrix product states satisfy it?
I am currently reading some papers concerning the question why the density matrix renormalization group (DMRG) method is working well for simulating one dimensional systems and bad for higher ...
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 ...
2
votes
1answer
242 views
Implementing simple atom model using density functional theory (DFT)
I am trying to write computer code which will find the energy and density function for a atom with Z protons and N electrons. I am working in 1D for simplicity and would like to make the overall code ...
2
votes
1answer
1k views
How Does force relate to velocity
I had originally asked this question on math overflow and it was suggested that I ask it here.
So I know that a force will change the magnitude of velocity if it is at an angle other that 90 degrees. ...
2
votes
1answer
47 views
The number of mean free paths which a particle traverses is independent of the material traversed
This is a manual from a Monte Carlo physics manual:
Computing the occurrence of a process
Can anyone tell me why the number of mean free paths of a particle is independent of the material which it ...
2
votes
1answer
244 views
Lennard Jones liquid vapour phase transition
I am trying to generate a phase diagram of pressure versus temperature in a NPT ensemble using molecular dynamics method. I am using the Lennard Jones potential with 108 particles and Berendsen ...
2
votes
1answer
82 views
Mutual Interaction of $N$-Particles in a Cartesian Plane
I am making a simulation of $N$-Particles in a cartesian plane and need help with understanding the basics.
At anytime, in my particle system, I will have $N$ number of particles. I am treating the ...
