arXiv subjects
Publications and source records attributed to Gavin Pandya.
We establish constructive geometric tools for determining when a domain is $L^s$-averaging and obtain upper and lower bounds for the $L^s$-integrals of the quasihyperbolic distance. We also construct examples which are helpful to understand our geometric tools and the relationship between $p$-Poincar\'{e} domains and $L^s$-averaging domains. Finally, finite unions of $L^s(\mu)$-averaging domains are explored.
We derive interface models for 3D Rayleigh-Taylor instability (RTI), making use of a novel asymptotic expansion in the non-locality of the fluid flow. These interface models are derived for the purpose of studying universal features associated to RTI such as the Froude number in single-mode RTI, the predicted quadratic growth of the interface amplitude under multi-mode random perturbations, the optimal (viscous) mixing rates induced by the RTI and the self-similarity of horizontally averaged density profiles, and the remarkable stabilization of the mixing layer growth rate which arises for the three-fluid two-interface heavy-light-heavy configuration, in which the addition of a third fluid bulk slows the growth of the mixing layer to a linear rate. Our interface models can capture the formation of small-scale structures induced by severe interface roll-up, reproduce experimental data in a number of different regimes, and study the effects of multiple interface interactions even as the interface separation distance becomes exceedingly small. Compared to traditional numerical schemes used to study such phenomena, our models provide a computational speed-up of at least two orders of magnitude.
For $0<\alpha<\frac{1}{3}$ we construct unique solutions to the fractal Burgers equation $\partial_t u + u\partial_xu + (-\Delta)^\alpha u = 0$ which develop a first shock in finite time, starting from smooth generic initial data. This first singularity is an asymptotically self-similar, stable $H^6$ perturbation of a stable, self-similar Burgers shock profile. Furthermore, we are able to compute the spatio-temporal location and H\"older regularity for the first singularity. There are many results showing that gradient blowup occurs in finite time for the supercritical range, but the present result is the first example where singular solutions have been explicitly constructed and so precisely characterized.