לוח שנה משולב

Advancements in the field of observational astronomy are usually limited by technological capabilities. In the current era technology has allowed for space-based surveys delivering a growing sample of high quality time series photometry. This has finally enabled the detailed study of variability along the orbital motion, or orbital phase, of stellar binaries and star-planet systems. These orbital modulations are induced by a combination of gravitational and atmospheric processes. Gravitational processes include the beaming effect (also known as Doppler boosting) and tidal ellipsoidal distortion, so the photometric light curve shape is sensitive to the companion’s mass and orbit’s shape. Atmospheric processes include reflection of light and thermal emission by the companion, making phase curves a tool for probing the companion’s atmosphere. Therefore, the study of phase curves has a large scientific potential, which we have only begun to explore in recent years. I will present the science done with phase curves, including the mass measurement of companions to hot early-type stars (where the mass cannot be measured using radial velocities), the search for non-eclipsing systems, and the study of the companions’ atmosphere. Finally, I will briefly discuss the study of phase curves with current and future space-based surveys including K2, TESS, and PLATO.

We study random knots and links in R^3 using the Petaluma model, which is based on the petal projections developed by Adams et al. (2012).

In this model we obtain a formula for the distribution of the linking number of a random two-component link. We also obtain formulas for the expectations and the higher moments of the Casson invariant and the order-three knot invariant v3. These are the first precise formulas given for the distributions of invariants in any model for random knots or links.

All terms above will be defined and explained.

Joint work with Joel Hass, Nati Linial, and Tahl Nowik.

Imposing a curved shape on a solid sheet, generates in it elastic stress. This familiar motif is a consequence of Gauss’ theorema Egregium, which posits that there exists no isometric map between two surfaces of different Gaussian curvatures. This coupling between geometry (curvature) and mechanics (stress) underlies the morphological richness observed in solid sheets, and their nontrivial response to exerted forces.

In this talk I will attempt to provide a unifying framework of this geometry-mechanics interplay, by demonstrating basic mechanisms through which a Gaussian curvature can (or cannot) be accommodated by solid sheets. A few examples will be discussed: a sheet attached to liquid drop, a twisted ribbon, and the indentation of a floating sheet.

Walking was once considered to be an automatic task that requires minimal higher-level cognitive input. This presentation will briefly review emerging evidence that links cognitive function to gait and fall risk in healthy adults and in patients with neurodegenerative disease. We will attempt to explain why certain gait alterations predict the development of dementia and why safe ambulation depends on executive function and attention. Building on those insights, we describe preliminary findings that illustrate the potential of novel therapeutic approaches for enhancing mobility and cognition and for reducing fall risk. A final example illustrates that a motor-cognitive intervention may promote beneficial neural plasticity in frontal lobe activation during complex walking conditions.