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Shuqiang Zhu

Publications and source records attributed to Shuqiang Zhu.

At least 19 recordsLinked to original sources
arXiv2025

On Finiteness of Stationary Configurations of the Planar Five-vortex Problem

The finiteness problem of stationary configurations for the planar five-vortex problem is considered in this paper. The numbers of equilibria and rigidly translating configurations are shown to be at most 6 and 24 respectively. The numbers of relative equilibria and collapse configurations are shown to be finite, except perhaps if the 5-tuple of vorticities belongs to a given codimension 2 subvariety of the vorticity space. In particular, if the vorticities are of the same sign, the number of stationary configurations is finite.

math-ph↗
arXiv2025

N-body choreographies on a p-limacon curve

We consider an $N$--body problem under a harmonic potential of the form $\frac{1}{2}\sum κ_{jl} |q_j-q_l|^2$. A $p$-limaçon curve is a planar curve parametrized by $t$ given by $a(\cos t,\sin t)+b(\cos pt, \sin pt)$, where $a,b\in \mathbb{R}$, $p \in \mathbb{Z}$, and $t \in [0,2π]$. We study $N$-body choreographic motions constrained to a $p$-limaçon curve and establish necessary and sufficient conditions for their existence. Specifically, we prove that choreographic motions exist if and only if $p/N, (p \pm 1)/N \notin \mathbb{Z}$. Under an additional symmetry assumption on the force coefficients, we further refine these conditions. We also analyze the occurrence of collisions, showing that for given $p$ and $N$, at most $2(N-1)$ choices of $a/b$ lead to collisions. Furthermore, we find additional conserved quantities.

math.DS↗
arXiv2025

Equivalence of Rigid Motions and Relative Equilibria in the N-Body Problem on the Two-Sphere

We investigate the relationship between rigid motions and relative equilibria in the N-body problem on the two-dimensional sphere, S2. We prove that any rigid motion of the N-body system on S2 must be a relative equilibrium. Our approach extends the classical study of rigid body dynamics by Euler and utilizes a rotating frame attached to the particles to derive the corresponding equations of motion. We further show that our results can be extended to the N-body gravitational system in R3. The results are oriented to a broader understanding of the dynamics of N-body systems on curved surfaces.

math.DS↗
arXiv2025

Symbolic Computations of the Two-Colored Diagrams for Central Configurations of the Planar N-vortex Problem

We apply the singular sequence method to investigate the finiteness problem for stationary configurations of the planar N-vortex problem. The initial step of the singular sequence method involves identifying all two-colored diagrams. These diagrams represent potential scenarios where finiteness may fail. We develop a symbolic computation algorithm to determine all two-colored diagrams for central configurations of the planar N-vortex problem.

math.DS↗
arXiv2024

Two Colored Diagrams for Central Configurations of the Planar Five-vortex Problem

We apply the singular sequence method to investigate the finiteness problem for stationary configurations of the planar five-vortex problem. The initial step of the singular sequence method involves identifying all two-colored diagrams. These diagrams represent potential scenarios where finiteness may fail. We determined all such diagrams for the planar five-vortex problem.

math.DS↗
arXiv2024

On the Nonexistence of Centered Co-Circular Central Configurations With Three Unequal masses

This paper examines the existence of centered co-circular central configurations in the general power-law potential n-body problem. We prove the nonexistence of such configurations when the system consists of n-3 equal masses and three arbitrary masses, under the condition that the three special masses are distinct or, if two of them are equal, not arranged in a specific manner.

math-ph↗
arXiv2023

Perturbing Masses: A Study of Centered Co-Circular Configurations in Power-Law n-Body Problems

This research investigates centered co-circular central configurations in the general power-law potential $n$-body problem. Firstly, there are no such configurations when all masses are equal, except for two; secondly, unless all masses are equal, no such configurations exist when masses can be divided into two sets of equal masses. We adapt Wang's criterion and incorporate insights on cyclic quadrilaterals, alongside mathematical induction.

math.DS↗
arXiv2023

On the finiteness of four-body central configurations

The number of central configurations in the four body problem was proved to be finite, first by Hampton and Moeckel, then by Albouy and Kaloshin, when the masses are all positive. We prove that the four-body central configurations are finite for any four nonzero masses.

math.DS↗
arXiv2022

The Schubart orbits on the circle

We consider the three body problem on $S^1$ under the cotangent potential. We first construct homothetic orbits ending in singularities, including total collision singularity and collision-antipodal singularity. Then certain symmetrical periodic orbits with two equal masses, called Schubart orbits, are shown to exist. The proof is based on the construction of a Wazewski set in the phase space.

math.DS↗
arXiv2021

Odd index of the amended potential implies linear instability

For a relative equilibrium of a symmetric simple mechanical system, if the Morse index of the corresponding amended potential is odd, whether the nullity is zero or not, it is linearly unstable. We also provide a sufficient condition for spectral instability.

math.DS↗
arXiv2021

Dziobek equilibrium configurations on a sphere

We investigate the n-body problem on a sphere with a general interaction potential that depends on the mutual distances. We focus on the equilibrium configurations, especially on the Dziobek equilibrium configurations, which is an analogy of Dziobek central configurations of the classical n-body problem. We obtain a criterion and then reduce it to two sets of equations. Then we apply these equations to the curved n-body problem in S^3. In the end, we find the derivative of the Cayley-Menger determinant.

math.CA↗
arXiv2021

Compactness and index of ordinary central configurations for the curved n-body problem

For the curved n-body problem, we show that the set of ordinary central configurations is away from most singular configurations in H^3, and away from a subset of singular configurations in S^3. We also show that each of the n!/2 geodesic ordinary central configurations for n masses has Morse index n-2. Then we get a direct corollary that there are at least (3n-4)(n-1)!/2 ordinary central configurations for given n masses if all ordinary central configurations of these masses are non-degenerate.

math.DS↗
arXiv2020

A Lower Bound for the Number of Central Configurations on H^2

We study the indices of the geodesic central configurations on $\H^2$. We then show that central configurations are bounded away from the singularity set. With Morse's inequality, we get a lower bound for the number of central configurations on $\H^2$.

math.CA↗
arXiv2019

Regular polygonal equilibrium configurations on S^1 and stability of the associated relative equilibria

For the curved n-body problem in S^3, we show that a regular polygonal configuration for n masses on a geodesic is an equilibrium configuration if and only if n is odd and the masses are equal. The equilibrium configuration is associated with a one-parameter family (depending on the angular velocity) of relative equilibria, which take place on S^1 embedded in S^2. We then study the stability of the associated relative equilibria on two invariant manifolds, T^*((§^1)^n\D) and T^*((§^2)^n\D). We show that they are Lyapunov stable on S^1, they are Lyapunov stable on S^2 if the absolute value of angular velocity is larger than a certain value, and that they are linearly unstable on S^2 if the absolute value of angular velocity is smaller than that certain value.

math.DS↗
arXiv2019

Classification of stacked central configurations in R^3

We classify the extensions of n-body central configurations to (n + 1)-body central configurations in R3, in both the collinear case and the non-collinear case. We completely solve the two open questions posed by Hampton (Nonlinearity 18: 2299- 2304, 2005). This classification is related with study on co-circular and co-spherical central configurations. We also obtain a general property of co-circular central configurations.

math.DS↗
arXiv2017

The $N$-Body Problem in Spaces with Uniformly Varying Curvature

We generalize the curved $N$-body problem to spheres and hyperbolic spheres whose curvature $κ$ varies in time. Unlike in the particular case when the curvature is constant, the equations of motion are non-autonomous. We first briefly consider the analogue of the Kepler problem and then investigate the homographic orbits for any number of bodies, proving the existence of several such classes of solutions on spheres. Allowing the curvature to vary in time offers some insight into the effect of an expanding universe, in the context the curved $N$-body problem, when $κ$ satisfies Hubble's law. The study of these equations also opens the possibility of finding new connections between classical mechanics and general relativity.

math.DS↗
arXiv2016

Three dimensional central configurations in H3 and S3

We show that each central configuration in the three-dimensional hyperbolic sphere is equivalent to one central configuration on a particular two- dimensional hyperbolic sphere. However, there exist both special and ordinary central configurations in the three-dimensional sphere that are not confined to any two-dimensional sphere.

math.CA↗