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Babak Modami

Publications and source records attributed to Babak Modami.

9 recordsLinked to original sources
arXiv2024

Thurston geodesics: no backtracking and active intervals

We develop the notion of the active interval for a subsurface along a geodesic in the Thurston metric on Teichmuller space of a surface S. That is, for any geodesic in the Thurston metric and any subsurface R of S, we find an interval of times where the length of the boundary of R is uniformly bounded and the restriction of the geodesic to the subsurface R resembles a geodesic in the Teichmuller space of R. In particular, the set of short curves in R during the active interval represents a reparametrized quasi-geodesic in the curve graph of R (no backtracking) and the amount of movement in the curve graph of R outside of the active interval is uniformly bounded which justifies the name active interval. These intervals provide an analogue of the active intervals introduced by the third author in the setting of Teichmuller space equipped with the Teichmuller metric.

math.GT↗
arXiv2020

Bottlenecks for Weil-Petersson geodesics

We introduce a method for constructing Weil-Petersson (WP) geodesics with certain behavior in the Teichm\"{u}ller space. This allows us to study the itinerary of geodesics among the strata of the WP completion and its relation to subsurface projection coefficients of their end invariants. As an application we demonstrate the disparity between short curves in the universal curve over a WP geodesic and those of the associated hyperbolic $3$-manifold.

math.GT↗
arXiv2016

Limit sets of Weil-Petersson geodesics

In this paper we prove that the limit set of any Weil-Petersson geodesic ray with uniquely ergodic ending lamination is a single point in the Thurston compactification of Teichm\"uller space. On the other hand, we construct examples of Weil-Petersson geodesics with minimal nonuniquely ergodic ending laminations and limit set a circle in the Thurston compactification.

math.GT↗
arXiv2016

Limit sets of Teichm\"uller geodesics with minimal nonuniquely ergodic vertical foliation, II

Given a sequence of curves on a surface, we provide conditions which ensure that (1) the sequence is an infinite quasi-geodesic in the curve complex, (2) the limit in the Gromov boundary is represented by a nonuniquely ergodic ending lamination, and (3) the sequence divides into a finite set of subsequences, each of which projectively converges to one of the ergodic measures on the ending lamination. The conditions are sufficiently robust, allowing us to construct sequences on a closed surface of genus $g$ for which the space of measures has the maximal dimension $3g-3$, for example. We also study the limit sets in the Thurston boundary of Teichm\"uller geodesic rays defined by quadratic differentials whose vertical foliations are obtained from the constructions mentioned above. We prove that such examples exist for which the limit is a cycle in the $1$-skeleton of the simplex of projective classes of measures visiting every vertex.

math.GT↗
arXiv2012

Prescribing the behavior of Weil-Petersson geodesics in the moduli space of Riemann surfaces

We study Weil-Petersson (WP) geodesics with narrow end invariant and develop techniques to control length-functions and twist parameters along them and prescribe their itinerary in the moduli space of Riemann surfaces. This class of geodesics is rich enough to provide for examples of closed WP geodesics in the thin part of the moduli space, as well as divergent WP geodesic rays with minimal filling ending lamination. Some ingredients of independent interest are the following: A strength version of Wolpert's Geodesic Limit Theorem proved in Sec.4. The stability of hierarchy resolution paths between narrow pairs of partial markings or laminations in the pants graph proved in Sec.5. A kind of symbolic coding for laminations in terms of subsurface coefficients presented in Sec.7.

math.GT↗