Short-Wave Asymptotics of the Information Entropy of a Circular Membrane

The spreading of the position and momentum probability distributions for the stable free oscillations of a circular membrane of radius l is analyzed by means of the associated Boltzmann-Shannon information entropies in the correspondence principle limit (n → ∞, m fixed), where the numbers (n,m), n ∈ N and m ∈ Z, uniquely characterize an oscillation of this two-dimensional system. This is done by solving the short-wave asymptotics of the physical entropies in the two complementary spaces, which boils down to the calculation of the asymptotic behaviour of certain entropic integrals of Bessel functions. It is rigorously shown that the position and momentum entropies behave as 2 ln(l) + ln(4π)− 2 and ln(n)− 2 ln(l) + ln(2π) when n → ∞, respectively. So the total entropy sum has a logarithmic dependence on n and it does not depend on the membrane radius. The former indicates that the ordering of short-wavelength oscillations is exactly identical for the entropic sum and the single-particle energy. The latter holds for all oscillations of the membrane because of the uniform scaling invariance of the entropy sum. ∗Corresponding author e-mail: [email protected]