arXiv subjects

Kamlesh Parwani

Publications and source records attributed to Kamlesh Parwani.

11 recordsLinked to original sources

arXiv2021

$C^1$ actions on the circle of finite index subgroups of $Mod(Σ_g)$, $Aut(F_n)$, and $Out(F_n)$

Let $Σ_{g}$ be a closed, connected, and oriented surface of genus $g \geq 24$ and let $Γ$ be a finite index subgroup of the mapping class group $Mod(Σ_{g})$ that contains the Torelli group $\mathcal{I}(Σ_g)$. Then any orientation preserving $C^1$ action of $Γ$ on the circle cannot be faithful. We also show that if $Γ$ is a finite index subgroup of $Aut(F_n)$, when $n \geq 8$, that contains the subgroup of IA-automorphisms, then any orientation preserving $C^1$ action of $Γ$ on the circle cannot be faithful. Similarly, if $Γ$ is a finite index subgroup of $Out(F_n)$, when $n \geq 8$, that contains the Torelli group $\mathcal{T}_n$, then any orientation preserving $C^1$ action of $Γ$ on the circle cannot be faithful. In fact, when $n \geq 10$, any orientation preserving $C^1$ action of a finite index subgroup of $Aut(F_n)$ or $Out(F_n)$ on the circle cannot be faithful.

math.GT↗

arXiv2016

Zero entropy subgroups of mapping class groups

Let $M$ be a compact surface with boundary. We are interested in the question of how a group action on $M$ permutes a finite invariant set $X \subset int(M)$. More precisely, how the algebraic properties of the induced group of permutations of a finite invariant set affects the dynamical properties of the group. Our main result shows that in many circumstances if the induced permutation group is not solvable then among the homeomorphisms in the group there must be one with a pseudo-Anosov component. We formulate this in terms of the mapping class group relative to the finite set and show the stronger result that in many circumstances (e.g. if $\partial M \ne \emptyset$) this mapping class group is itself solvable if it has no elements with pseudo-Anosov components.

math.DS↗

arXiv2015

Anomalous partially hyperbolic diffeomorphisms I: dynamically coherent examples

We build an example of a non-transitive, dynamically coherent partially hyperbolic diffeomorphism $f$ on a closed $3$-manifold with exponential growth in its fundamental group such that $f^n$ is not isotopic to the identity for all $n\neq 0$. This example contradicts a conjecture in \cite{HHU}. The main idea is to consider a well-understood time-$t$ map of a non-transitive Anosov flow and then carefully compose with a Dehn twist.

math.DS↗

arXiv2010

On 3-manifolds that support partially hyperbolic diffeomorphisms

Let M be a closed 3-manifold that supports a partially hyperbolic diffeomorphism f. If $π_1(M)$ is nilpotent, the induced action of f on $H_1(M, R)$ is partially hyperbolic. If $π_1(M)$ is almost nilpotent or if $π_1(M)$ has subexponential growth, M is finitely covered by a circle bundle over the torus. If $π_1(M)$ is almost solvable, M is finitely covered by a torus bundle over the circle. Furthermore, there exist infinitely many hyperbolic 3-manifolds that do not support dynamically coherent partially hyperbolic diffeomorphisms; this list includes the Weeks manifold. If f is a strong partially hyperbolic diffeomorphism on a closed 3-manifold M and if $π_1(M)$ is nilpotent, then the lifts of the stable and unstable foliations are quasi-isometric in the universal of M. It then follows that f is dynamically coherent. We also provide a sufficient condition for dynamical coherence in any dimension. If f is center bunched and if the center-stable and center-unstable distributions are Lipschitz, then the partially hyperbolic diffeomorphism f must be dynamically coherent.

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arXiv2008

C^1 actions of the mapping class group on the circle

Let S be a connected orientable surface with finitely many punctures, finitely many boundary components, and genus at least 6. Then any C^1 action of the mapping class group of S on the circle is trivial. The techniques used in the proof of this result permit us to show that products of Kazhdan groups and certain lattices cannot have C^1 faithful actions on the circle. We also prove that for n > 5, any C^1 action of Aut(F_n) or Out(F_n) on the circle factors through an action of Z/2Z.

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arXiv2007

Harmonic functions on R-covered foliations and group actions on the circle

Let (M, F) be a compact codimension-one foliated manifold whose leaves are equipped with Riemannian metrics, and consider continuous functions on M that are harmonic along the leaves of F . If every such function is constant on leaves we say that (M, F) has the Liouville property. Our main result is that codimension-one foliated bundles over compact negatively curved manifolds satisfy the Liouville property. Related results for R-covered foliations, as well as for discrete group actions and discrete harmonic functions, are also established.

math.DS↗

arXiv2006

Fixed Points of abelian actions

We prove that if $\F$ is an abelian group of $C^1$ diffeomorphisms isotopic to the identity of a closed surface $S$ of genus at least two then there is a common fixed point for all elements of $\F.$

math.DS↗

arXiv2005

Fixed Points of abelian actions on $S^2$

We prove that if $F$ is a finitely generated abelian group of orientation preserving $C^1$ diffeomorphisms of $R^2$ which leaves invariant a compact set then there is a common fixed point for all elements of $F.$ We also show that if $F$ is any abelian subgroup of orientation preserving $C^1$ diffeomorphisms of $S^2$ then there is a common fixed point for all elements of a subgroup of $F$ with index at most two.

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arXiv2005

Simple braids for surface homeomorphisms

Let S be a compact, oriented surface with negative Euler characteristic and let f be a homeomorphism of S that is isotopic to the identity. If there exists a periodic orbit with a non-zero rotation vector, then there exists a simple braid with the same rotation vector.

math.DS↗

arXiv2005

Monotone periodic orbits for torus homeomorphisms

Let f be a homeomorphism of the torus isotopic to the identity and suppose that there exists a periodic orbit with a non-zero rotation vector (p/q,r/q), then f has a topologically monotone periodic orbit with the same rotation vector.

math.DS↗

arXiv2005

Actions of SL(n,Z) on homology spheres

Any continuous action of SL(n,Z), where n > 2, on a r-dimensional mod 2 homology sphere factors through a finite group action if r < n - 1. In particular, any continuous action of SL(n+2,Z) on the n-dimensional sphere factors through a finite group action.

math.GT↗