Hot answers tagged

8

Virtually all experiments (at least in condensed matter physics) fall under this category. Unlike in high energy, where we're actually testing fundamental physical theories, at the energy scales of condensed matter, we are quite confident that in principle, the many-body nonrelativistic Schrodinger equation runs the whole show. (Perhaps with relativistic ...


2

A very well-known example is atomic weapons. It is much easier to build a device and test it than it is to simulate it: it took a very long time before simulations of existing designs and small variations on them became convincing enough that people had any faith in them at all, and I believe that we can really only use simulations now because it became ...


2

If there is no gravity in your simulation, your thoughts are on the right lines. The amount of centripetal force (=thrust) required to maintain a space-craft of mass m in circular orbit of radius r at speed v is $F=mv^2/r$. Thrust has to be directed towards the centre of the circle and has to be maintained constantly - so unlike orbiting a planet using ...


2

The point is there's several $W$'s. $$\rho_i=\sum_j W(\mathbf{p}_i-\mathbf{p}_j,h)=W(\mathbf{p}_i-\mathbf{p}_1,h)+W(\mathbf{p}_i-\mathbf{p}_2,h)+\ldots$$ dropping the mass as they do in the paper. The thing is they're treating the particles as indistinguishable e.g. they all have equal mass, so the form of the functions/constraints applied to them are the ...


1

But I think it gives the wrong answer. No matter what the direction of $\mathbf{m} _{1}$ or $\mathbf{m} _{2}$, I think the force must be always parallel to r to conserve angular momentum. The force acting on magnetic moment due to another magnetic moment is not always parallel to the line that connects them. This does not violate conservation of angular ...


1

You are not the first to question this; see for example the work by Leiner et al. from 2013 and 2014. Here the Ray Tracing technique is interfaced to Finite Difference Time Domain (FDTD) Maxwell simulations with ''the Poynting vector representation of either rays or wave propagation directions''. As noted in these works you should be aware of the absence ...


1

The weight functions should be continuous and vary from a maximum value at $r=0$ to zero at the cut-off. The linear function is the simplest and computationally least expensive function that satisfies this requirement. That's why it's used. Note, however, that non-linear functions are occasionally used, e.g. Yaghoubi, S., et al. "New modified weight ...


1

Well, the "object" has two kinds of energy at all times: kinetic (movement), and gravitational potential. This calculation you want to do is easiest if there is only one significant body, like the sun. In this case, at the beginning your KE (kinetic energy) is 0.5mv2, and your gravitational energy is Ug = -Gm1m2/r. Now, an object can never completely leave ...


1

I know that in Full Configurational Interaction Quantum Monte Carlo(FCIQMC), where they start from the Schrödinger equation and sample the full configurational space with integer walkers, there is a spontaneous symmetry breaking between the $\Psi$ and $-\Psi$ after a sufficient number of walkers are spawned into the configurational space. It treats the ...


1

The formula for gravity is $F_g=\large{\frac{Gm_1m_2}{r^2}}$. So store variables for your $x$ and $y$ velocities (or an array or whatever method you wish) and change your position by your velocity each frame. Also each frame, use a loop (I don't know what language you're using so I can't give exact code) to look at each planet and plug everything into the ...



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