Tag Info

Hot answers tagged

17

I think perhaps some of the other answers are taking computer science to be synonymous with computation. I guess that this is perhaps not what you mean, but rather theoretical computer science. There is obviously a huge overlap with quantum information processing of which I think you are already well aware, so I will ignore that. Much of physics (including ...


13

Starting from 90nm tech processes we've started to see sad signs of stagnation: 1) Most of delay in logic circuits is in interconnect, not transistors 2) Most of energy dissipated is due to quantum tunneling, not transistor switching. By far. 3) As consequence of #2 - transistor gate width scaling has significantly slowed down, as well as dielectric width ...


12

Programming is immensely useful in any branch of physics. I don't know where the notion that programming is not useful at CERN comes from (? Home of the ROOT package, and the internet? Really? TeraGrid, eh? 1 GB/s of data from the detectors at the LHC won't analyze themselves!), but you may wish to revisit your research on that matter. I can say that in ...


10

Crank-Nicholson method is effectively the average of forward (explicit) Euler $\psi(x,t+dt)=\psi(x,t) - i*H \psi(x,t)*dt$ and backward (implicit) Euler method $\psi(x,t+dt)=\psi(x,t) - i*H \psi(x,t+dt)*dt$ The backward component makes Crank-Nicholson method stable. The forward component makes it more accurate, but prone to oscillations. If you want to ...


10

EDIT: This answer is specifically from the perspective of very computationally oriented fields like theoretical plasma physics. Most physicists can program, and in fact many are rather good programmers. It would be difficult to work in modern physics without being able to program. Unfortunately, many are also not terribly good programmers (I've read many a ...


10

I can't really know why your professor used C++, but there are several reasons why you would: Performance: Scientific computations might require top-notch performance. C++ allows for very low level control over the hardware and has many possibilities for micro-optimization while still providing high-level abstraction. Of course, this is also the reason ...


9

Programming is extremely important in almost every area of physics. Not every physicist has to be an expert programmer, but many are, and virtually all physicists are at least competent programmers. In most experiments, the process of data analysis is complex enough to require some programming. More importantly, in many situations, the best (or only) way of ...


7

You don't need a really big computer. Peter LePage used to do talks where he'd ask the audience fro a "random" number as the beginning of the talk (but not 7, 17, 42, or 69 'cause he'd already done those) and start a simulation on one screen with that number as a seed. Then he'd give a talk on how to speed up LQCD calculations on the other screen while his ...


7

You are asking two questions. I am only going to address one of them: Can the Church-Turing hypothesis be deduced from other fundamental law of physics? There are two fundamental theories of physics that account for nearly all experiments and observations performed to date: general relativity and the Standard Model. If we could simulate these theories ...


7

this is a broad, complex, somewhat tricky question with many angles that an entire survey or book could be written on but unfortunately it seems one hasnt yet. heres a "grab bag" of some deep parallels noticed over the years that such a book might cover & "research leads" for further inquiry. Modelling and simulation. as computing capability has ...


6

While not strictly lattice QCD, Michael Creutz' 30 year old lattice gauge papers have very simple C implementations (!). For example, look at this paper, which gives a very readable explanation of lattice gauge simulations, with source code: http://latticeguy.net/mypubs/pub165.pdf The source code is also available here: http://thy.phy.bnl.gov/~creutz/z2/ ...


6

The first thing that comes to mind is that the speed of light limits the rate at which different components of a computer, or even a single chip, can communicate with each other. For example, if you have, say, 10 cm of wire running between your motherboard and hard drive, it will necessarily take a minimum of about a third of a nanosecond to fetch data from ...


6

"They" are probably talking about symplectic integrators. Most numerical integrators for (partial) differential equations do not specifically consider the energy of the system; they are generic integrators capable of solving any set of DEs, and not all DE's have a concept like "energy". When these are applied to a classical dynamics problem concerning ...


6

If you look at the Laplacian: $$ \nabla^2=\frac{1}{r}\,\frac{\partial}{\partial r}\left(r\frac{\partial}{\partial r}\right)+\frac1{r^2}\frac{\partial^2}{\partial\phi^2} $$ you can clearly see that this diverges at $r=0$ so discretization of this should also diverge. There are three solutions to remedying the divergent feature that I can think of: Choose a ...


5

Programming is a skill that some physicists need and others do not. Ditto for knowing your way around a mill or a lathe. Ditto for digital electronics, or contour integrals, or writing popularizations, or vacuum systems.


5

When you think of a physical parameter which is "uncomputable", what precisely do you mean? For us to know that it is uncomputable, it has to arise somehow, on theoretical grounds, from e.g. a compu­tational process which is equivalent to the Halting Problem of theoretical computer science; so that we could not compute it from first principles. ...


5

Some of the SDSS images in JPEG format (for example those served by the SDSS DAS) have sections of the FITS headers of the corresponding data images embedded in them. I expect that other projects have done similar things, but I am not aware of any uniformity in how it is done. For the most part, the image formats you list were really not intended for ...


5

Overlap fermion approach may be the answer. Ounce a theory is defined on a lattice, it can be simulated by a computer that we already have. Here is a review on overlap fermion approach: Tata lectures on overlap fermions arXiv:1103.4588 R. Narayanan Overlap formalism deals with the construction of chiral gauge theories on the lattice. These set of ...


5

Color forces are not like electromagnetic ones. There exist no unbound color carrying particles analogous to the electron, because the forces increase with the distance rather than decrease and collective effects appear only within nuclei through residuals of the colored forces which attract the nucleons and hold them in the nuclei. Collective effects ...


5

Computational quantum chemistry is one. Researchers in pharmaceutics use computational quantum chemistry programs to model the interactions of small molecules (drugs or fragments of drugs) with proteins/DNA and predict whether or not the designed drug may or may not be effective for its purpose. They can do that before having to spend time and money ...


5

What you want to do is change the wave equation into a Klein-Gordon equation: $$\frac {1}{c^2} \frac{\partial^2 \psi}{\partial t^2} - \nabla^2 \psi + \alpha^2 \psi = 0,$$ where $\alpha$ is a constant of appropriate dimension and usually (in quantum theory) given by $$\alpha=\frac {m c}{\hbar}.$$ Inserting an ansatz of the form $$\psi=e^{i(kx-\omega ...


5

There are numerous examples of people using genetic algorithms, for example, to optimize some output where an actual solution of the equation would be otherwise impossible. Information entropy, which is a generic computing concept, has some hold on statistical physics. But I cannot think of a case I have seen where a concept from cutting edge computer ...


5

As I commented, I would think that any 3D hydrodynamics code would work. The basics of hydrodynamics can be summed up in the following five equations: \begin{eqnarray} \frac{\partial \rho}{\partial t}+\nabla\cdot\rho\mathbf{v}=0 \tag{1} \\ \frac{\partial \rho\mathbf{v}}{\partial t}+\nabla\cdot\left[\rho\mathbf{v}\otimes\mathbf{v}+P\mathbb ...


5

I would argue that this maybe due to the way you calculate your autocorrelation. An autocorrelation like that straight line is the result of a large square signal. The Ising model has a phase transition at the critical temperature. Above it, it's disordered; below it, it becomes ordered, which means that the magnetization stops flipping back and forth. This ...


5

There are three ways you can proceed in: 1. Homogeneous Flow Model Herein, you would assume single averaged flow quantities and then solve the Navier-Stokes equations as if it were arising from the flow of an averaged liquid. What I mean is that if you had water and steam flowing together, you would take the average density, viscosity and so on. ...


4

What they show in the paper is that, for $\beta>2$, there are no solutions with the given asymptotic form as $r\to 0$ unless we assume $\alpha>0$. I think you can go further and show that there are no nonsingular solutions for $\beta>2,\alpha<0$, but I'm not sure. What does this mean physically? Well, when we have a potential with a ...


4

After a bit of research, I believe the most robust solution that I could find is the 'Astronomy Visualization Metadata (AVM) standard for astronomical imagery', which uses Adobe's XMP standard to embed the metadata as RDF. XMP can be embedded in PDF, JPEG, JPEG 2000, GIF, PNG, TIFF, PS, EPS and audio and other non-image formats. Other potential candidates ...



Only top voted, non community-wiki answers of a minimum length are eligible