Bivariate Truncated Moment Sequences with the Column Relation $XY=X^m + q(X)$, with $q$ of degree $m-1$

TL;DR

This paper investigates the truncated moment problem for specific rational plane curves, transforming it into equivalent problems and providing explicit solutions for cubic and quartic cases, advancing understanding of moment sequences on algebraic varieties.

Contribution

It introduces a method to convert the TMP for certain rational curves into Hankel completion problems and explicitly solves these for cubic and quartic curves, expanding the class of solvable cases.

Findings

Explicit solution for cubic curves' moment problem.

Reduction of quartic case to a three-variable inequality feasibility.

Transformation of TMP into Hankel positive semidefinite completion problems.

Abstract

When the algebraic variety associated with a truncated moment sequence is finite, solving the moment problem follows a well-defined procedure. However, moment problems involving infinite algebraic varieties are more complex and less well-understood. Recent studies suggest that certain bivariate moment sequences can be transformed into equivalent univariate sequences, offering a valuable approach for solving these problems. In this paper, we focus on addressing the truncated moment problem (TMP) for specific rational plane curves. For a curve of general degree we derive an equivalent Hankel positive semidefinite completion problem. For cubic curves, we solve this problem explicitly, which resolves the TMP for one of the four types of cubic curves, up to affine linear equivalence. For the quartic case we simplify the completion problem to a feasibility question of a three-variable system of inequalities.