Oral title: Dynamical effects of rotating shadows cast on gaseous disks

Oral abstract: Despite the recent discovery of spiral-shaped features in protoplanetary discs in the near-infrared and 
millimetric wavelengths, there is still an active discussion to understand how they formed. Several physical mechanisms 
have been proposed to explain such observations:  companion torques, gravitational perturbations, and more recently, 
illumination effects. 
In this talk, I will discuss the spirals formed in the gaseous phase due to two diametrically opposed shadows cast either 
at fixed disc locations or in a rotational motion. The shadows are created by an inclined precessing disc inside the cavity, 
which is assumed to be optically thick. We find that only static and prograde shadows trigger spirals, in contrast to 
retrograde ones. Interestingly, if a region of the disc corotates with the shadow, then an instability develops at the 
resonance position. The resulting spirals resemble those caused by a planet embedded in the disc, with similar pitch 
angles. We also analyze the effect of these spirals on the dynamics of dust particles and discuss their detectability on 
transition discs emulating ALMA millimetric-wavelength observations.