arXiv subjects

Luke M. Schubert

Publications and source records attributed to Luke M. Schubert.

2 recordsLinked to original sources

arXiv1999

Nonexistence results for the Korteweg-deVries and Kadomtsev-Petviashvili equations

We study characteristic Cauchy problems for the Korteweg-deVries (KdV) equation $u_t=uu_x+u_{xxx}$, and the Kadomtsev-Petviashvili (KP) equation $u_{yy}=\bigl(u_{xxx}+uu_x+u_t\bigr)_x$ with holomorphic initial data possessing nonnegative Taylor coefficients around the origin. For the KdV equation with initial value $u(0,x)=u_0(x)$, we show that there is no solution holomorphic in any neighbourhood of $(t,x)=(0,0)$ in ${\mathbb C}^2$ unless $u_0(x)=a_0+a_1x$. This also furnishes a nonexistence result for a class of $y$-independent solutions of the KP equation. We extend this to $y$-dependent cases by considering initial values given at $y=0$, $u(t,x,0)=u_0(x,t)$, $u_y(t,x,0)=u_1(x,t)$, where the Taylor coefficients of $u_0$ and $u_1$ around $t=0$, $x=0$ are assumed nonnegative. We prove that there is no holomorphic solution around the origin in ${\mathbb C}^3$ unless $u_0$ and $u_1$ are polynomials of degree 2 or lower.

solv-int↗

arXiv1998

The Laplacian on $p$-forms on the Heisenberg group

The Novikov-Shubin invariants for a non-compact Riemannian manifold M can be defined in terms of the large time decay of the heat operator of the Laplacian on square integrable p-forms on M. For the (2n+1)-dimensional Heisenberg group H, the Laplacian can be decomposed into operators in the conjugate of the generalised Bargmann representations which, when restricted to the centre of H, are characters. The representation space is an anti-Fock space of anti-holomorphic functions on complex n-space which are square integrable with respect to a Gaussian measure. In this paper, the eigenvalues of decomposed operators are calculated, using operators which commute with the Laplacian; this information determines all the Novikov-Shubin invariants of H. Further, some eigenvalues of operators connected with nilpotent Lie groups of Heisenberg type are calculated in the later sections.

math.DG↗