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For questions about mathematical problems arising from physics, the natural science studying general properties of matter, radiation and energy.

3 votes

Conserved quantities for the Cauchy momentum equation

1) conserved quantity for incompressible flow: $$\frac{d\rho}{dt}=\frac{\partial\rho}{\partial t}+\bar{v}\cdot\nabla\rho=0$$ so if the flow is stationary, $\partial\rho/\partial t=0$, the density $\ …
Carlo Beenakker's user avatar
6 votes
Accepted

Mathematical difference between solitons and traveling waves for a non-linear dispersive PDE

A necessary requirement for a traveling wave $u(x,t)=f(x-ct)$ to be a "solitary wave" or "soliton" is that the two limits $\lim_{s\rightarrow\pm\infty}f(s)=\alpha_\pm$ exist. This is the condition of …
Carlo Beenakker's user avatar
7 votes
Accepted

How are spatial coordinate systems in physics defined?

This question has been explored in the context of global positioning systems, which need to account for general relativity. The traditional Minkowski coordinates $(t,x,y,z)$ of flat space-time do not …
Carlo Beenakker's user avatar
2 votes
Accepted

Why is the physical space equivalent to $\mathbb{R}^3$

this is basically a question on the granularity of space, which is an active topic of research in physics: space appears to be continuous, but does it actually come in discrete chunks on some very small …
Carlo Beenakker's user avatar
1 vote

orthotropic materials solution of boundary value problems

Analytical methods of solution are typically restricted to two-dimensional geometries, see for example Applications of symmetry methods in basic problems of orthotropic elasticity (1999) We discus …
Carlo Beenakker's user avatar
6 votes
Accepted

Why are discreteness and smoothness in physics inversed with respect to geometry?

The "manifold picture" can be applied to physics in the context of the Brillouin zone, see for example On Brillouin Zones. …
Carlo Beenakker's user avatar
5 votes

Why are solenoidal fields called solenoidal?

[To expand on Wojowu's comment.] Q: "Why the description of a divergence-free field as solenoidal? I expect that this name had historical origins but its unlikely that it was so named without some lin …
Carlo Beenakker's user avatar
13 votes
Accepted

How does a Masters student of math learn physics by self?

I can recommend Leonard Susskind's Theoretical Minimum: A number of years ago I became aware of the large number of physics enthusiasts out there who have no venue to learn modern physics and cosmology … So I started a series of courses on modern physics at Stanford University where I am a professor of physics. …
Carlo Beenakker's user avatar
12 votes

Representation theory and elementary particles

The Algebra of Grand Unified Theories, by John Baez and John Huerta may well be to your liking: A full-fledged treatment of particle physics requires quantum field theory, which uses representations … This brings in a lot of analytical subtleties, which make it hard to formulate theories of particle physics in a mathematically rigorous way. …
Carlo Beenakker's user avatar
6 votes

Applications of Hamiltonian formalism to classical mechanics

The Poincaré-von Zeipel method in celestial mechanics relies on canonical transformations of the Hamiltonian to separate fast and slow degrees of freedom in a solar system. See, for example, A note on …
Carlo Beenakker's user avatar
11 votes
Accepted

Does current follow the path(s) of least (total) resistance?

Perhaps to resolve this issue it helps to work out a simple example. Take a region $D$ consisting of the strip $|x|<1$, $0<y<1$, and a $y$-independent conductivity profile $$\sigma(x)=\begin{cases} 1 …
Carlo Beenakker's user avatar
5 votes
Accepted

Gadgets as primality tests

The gadgets use effects from chemistry (Biochemical identification of prime numbers), biology ( A Biological Generator of Prime Numbers, and physics An optical Eratosthenes' sieve for large prime numbers …
Carlo Beenakker's user avatar
3 votes

Quantum tunneling on the line with non-symmetric double well potential

Tunnel splitting of the spectrum and bilocalization of eigenfunctions in an asymmetric double well has a "theorem" on the bilocalization phenomenon (wave function localized in both asymmetric wells); …
Carlo Beenakker's user avatar
18 votes

Applications of complex exponential

Early applications of $e^{i\omega t}$ in the context of electromagnetism were understood as a mathematical device: the physical fields are real, and the complex exponential is a convenient method to i …
Carlo Beenakker's user avatar
28 votes

When exactly and why did matrix multiplication become a part of the undergraduate curriculum?

The article by J.-L. Dorier in On the Teaching of Linear Algebra suggests the answer to your question will be different for the UK and for continental Europe: In an attempt to answer your questio …
Carlo Beenakker's user avatar

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