The formation of planets in disks around young stars is one of the most fundamental questions in astronomy. Transition disks are of particular interest because of their gas/dust depleted cavities. Clearing by companions is the most exciting explanation, but photoevaporation or other physical processes can be responsible of such inner cavities and represent active evolution of protoplanetary disks.
The Atacama Large Millimeter/submillimeter Array (ALMA) now offers unprecedented sensitivity and spatial resolution, which have revealed fascinating structures of transition disks: rings, vortices, asymmetries, and spiral arms. Complement with data at other wavelengths, these detailed observations are revolutionising our knowledge on the dynamic processes in transition disks, as a critical evolutionary stage in the formation of planets. Recent numerical simulations have shown a wide range of instabilities that indeed result in asymmetric structures. The cavities in transition disks are thus not only a signature of active evolution in the disk, the physical processes involved may actually trigger further evolution and planet formation.
We will bring together experts in theoretical models and observations of transition disks, to discuss and understand the most recent ALMA Cycle 1 and 2 observations of some of these objects. During the workshop the most recent results will be presented both from observations and modelling efforts, followed by extensive discussion. We will address different questions such as: What is creating the transition disk structures, specially the dust cavities? Can we constrain the properties of embedded planets? What are the gas and dust distributions in these disks? Do all classical disks evolve through these transition phases? The aims of the workshop are: starting scientific papers to connect the most recent observations with current theoretical models; making a detailed plan for future collaborations to improve the bridge between theory and observations of transition disks; and planning future observational proposals for ALMA-Cycle 3.