Finiteness of AnA_n-equivalence types of gauge groups

Let $B$ be a finite CW complex and $G$ a compact connected Lie group. We show that the number of gauge groups of principal $G$-bundles over $B$ is finite up to $A_n$-equivalence for $n<\infty$. As an example, we give a lower bound of the number of $A_n$-equivalence types of gauge groups of principal \SU(2)-bundles over $S^4$.Comment: 17 pages, 10 figure

Mapping spaces from projective spaces

We denote the $n$-th projective space of a topological monoid $G$ by $B_nG$ and the classifying space by $BG$. Let $G$ be a well-pointed topological monoid of the homotopy type of a CW complex and $G'$ a well-pointed grouplike topological monoid. We prove the weak equivalence between the pointed mapping space $\mathrm{Map}_0(B_nG,BG)$ and the space of all $A_n$-maps from $G$ to $G'$. This fact has several applications. As the first application, we show that the connecting map $G\rightarrow\mathrm{Map}_0(B_nG,BG)$ of the evaluation fiber sequence $\mathrm{Map}_0(B_nG,BG)\rightarrow\mathrm{Map}(B_nG,BG)\rightarrow BG$ is delooped. As other applications, we consider higher homotopy commutativity, $A_n$-types of gauge groups, $T_k^f$-spaces by Iwase--Mimura--Oda--Yoon and homotopy pullback of $A_n$-maps. In particular, we show that the $T_k^f$-space and the $C_k^f$-space are exactly the same concept and give some new examples of $T_k^f$-spaces.Comment: 26 pages, 3 figures; the appendix in v3 is deleted since its argument was incomplet

Scattering Theory for the Dirac Equation with a Nonlocal Term

Consider a scattering problem for the Dirac equation with a nonlocal term including he Hartree type. We show the existence of scattering operators for small initial data n the subcritical and critical Sobolev spaces

On the asymptotic behavior of nonlinear waves in the presence of a short-range potential

Consider the nonlinear wave equation with zero mass and a time-independent otential in three space dimensions. When it comes to the associated Cauchy problem, it s already known that short-range potentials do not a®ect the existence of small-amplitude olutions. In this paper, we focus on the associated scattering problem and we show that he situation is quite di®erent there. In particular, we show that even arbitrarily small and apidly decaying potentials may a®ect the asymptotic behavior of solutions

Small-data scattering for nonlinear waves of critical decay in two space dimensions

Consider the nonlinear wave equation with zero mass in two space dimensions. hen it comes to the associated Cauchy problem with small initial data, the known existence esults are already sharp; those require the data to decay at a rate k ¸ kc, where kc is a critical ecay rate that depends on the order of the nonlinearity. However, the known scattering results reat only the supercritical case k > kc. In this paper, we prove the existence of the scattering perator for the full optimal range k ¸ kc