Remarks on the horocycle flows for foliations by hyperbolic surfaces

We show that the horocycle flow associated with a foliation on a compact manifold by hyperbolic surfaces is minimal under certain conditions.

Horocycle flows without minimal sets

We show that the horocycle flows of open tight hyperbolic surfaces do not admit minimal sets.

Weak form of equidistribution theorem for harmonic measures of foliations by hyperbolic surfaces

We show that the equidistribution theorem of C. Bonatti and X. Gomez-Mont for a special kind of foliations by hyperbolic surfaces does not hold in general, and seek for a weaker form valid for general foliations by hyperbolic surfaces.

Kinematic expansive suspensions of irrational rotations on the circle

We shall show that the rotation of some irrational rotation number on the circle admits suspensions which are kinematic expansive.

Basic partitions and combinations of group actions on the circle: A new approach to a theorem of Kathryn Mann

Let $Pi_g$ be the surface group of genus $g$ ($ggeq2$), and denote by $RR_{Pi_g}$ the space of the homomorphisms from $Pi_g$ into the group of the orientation preserving homeomorphisms of $S^1$. Let $2g-2=kl$ for some positive integers $k$ and $l$. Then the subset of $RR_{Pi_g}$ formed by those $varphi$ which are semiconjugate to $k$-fold lifts of some homomorphisms and which have Euler number $eu(varphi)=l$ is shown to be clopen. This leads to a new proof of the main result of Kathryn Mann cite{Mann} from a completely different approach.

Actions of groups of diffeomorphisms on one-manifolds by $C^1$ diffeomorphisms

Denote by $DC(M)_0$ the identity component of the group of the compactly supported $C^r$ diffeomorphisms of a connected $C^infty$ manifold $M$. We show that if $dim(M)geq2$ and $r eq dim(M)+1$, then any homomorphism from $DC(M)_0$ to ${Diff}^1(R)$ or ${Diff}^1(S^1)$ is trivial.

Actions of groups of diffeomorphisms on one-manifolds

Denote by $DC(M)_0$ the identity component of the group of compactly supported $C^infty$ diffeomorphisms of a connected $C^infty$ manifold $M$, and by $HR$ the group of the homeomorphisms of $R$. We show that if $M$ is a closed manifold which fibers over $S^m$ ($mgeq 2$), then any homomorphism from $DC(M)_0$ to $HR$ is trivial.

New proofs of theorems of Kathryn Mann

We give a shorter proof of the following theorem of Kathryn Mann cite{M}: the identity component of the group of the compactly supported $C^r$ diffeomorphisms of $R^n$ cannot admit a nontrivial $C^p$-action on $S^1$, provided $ngeq2$, $r eq n+1$ and $pgeq2$. We also give a new proof of another theorem of Mann: any nontrivial endomorphism of the group of the orientation preserving $C^r$ diffeomorphisms of the circle is the conjugation by a $C^r$ diffeomorphism, if $rgeq3$.

Quantification of group chasing and escaping process

We study a simple group chase and escape model by introducing new parameters with which configurations of chasing and escaping in groups are classified into three characteristic patterns. In particular, the parameters distinguish two essential configurations: a one-directional formation of chasers and escapees, and an escapee surrounded by chasers. In addition, pincer movements and aggregating processes of chasers and escapees are also quantified. Appearance of these configurations highlights efficiency of hunting during chasing and escaping.