bio  website  ilorentz.org/beenakker 

location  Leiden, The Netherlands  
age  
visits  member for  3 years, 9 months 
seen  28 mins ago  
stats  profile views  4,210 
physicist at Leiden University
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Use a graphic tablet to write in Latex or MathML
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Use a graphic tablet to write in Latex or MathML
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Use a graphic tablet to write in Latex or MathML
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answered  Use a graphic tablet to write in Latex or MathML 
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Taking matrix derivative with MATLAB or Wolfram Alpha
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Mathematics of volleyball
"mathematics of volleyball"? don't you mean "physics of volleyball"? there's an extensive literature on that. 
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answered  Taking matrix derivative with MATLAB or Wolfram Alpha 
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Taking matrix derivative with MATLAB or Wolfram Alpha
en.wikipedia.org/wiki/Matrix_calculus#Other_matrix_derivatives 
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answered  Making a system of secondorder ODEs chaotic 
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Helmholtz equation Poynting vector integral
I like to think about this in mechanical terms: the domain $\Omega$ is a box filled with photons, sloshing around periodically with period $2\pi/\omega$; their total momentum oscillates with the same period, why would the amplitude of this oscillation be zero? Momentum conservation just says that forces on the boundary of the box have to appear if the momentum oscillates, so there will be some net force on the boundaries that oscillates with the same period. Why do you see a conflict with conservation of momentum? 
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Helmholtz equation Poynting vector integral
physics.stackexchange.com/questions/131509/…  researchgate.net/post/… 
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Trapping a particle
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Trapping a particle
To determine $C$ in equation (1) one will have to solve a diffusion equation and there is no closedform expression, unlike for the ergodic case in equations (2)(4). The proof by Lewenkopf and Vallejos applies to the ergodic case, when the particle explores the whole phase space before exiting. Then $\tau$ is simply a ratio of phase space areas, without any shape dependence. A Brownian walk inside $Y$ is not ergodic, so their proof does not apply. 
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Trapping a particle
@BorisBukh  I have added a figure and included a reference where the result for the average dwell time is derived in some detail. 
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