Neutron star radius-to-mass ratio from accretion disc occultation

• Riccardo La Placa

The equation of state (EoS) of ultradense matter in neutron stars (NSs) contains key information on the strong force and possible exotic states of matter; however, it is only poorly constrained from earth-based experiments and theory, while precise measurements of NS masses (M) and radii (R) would act as proxies of the EoS. I present a new method to measure the R/M ratio of disk-accreting NSs exploiting the occultation of the inner disk region right behind the NS by its surface. By simulating observations of a near-future mission we found that R/M can be measured to <5% precision, which is the one required to draw quantitative conclusions on the EoS of ultradense matter.

Dicussion

Pressure in Active Bacterial Bath

• Ojus Bagal

Active matter is driven system in which energy is supplied directly, isotropically and independently to individual constituents, who dissipate it to achieve persistent motion. Active particles, at micron scale, are capable of generating mechanical power. However, thermodynamic concept of pressure vaguely defined in them. We experimentally study active systems using genetically modified phototactic E. coli strains along with dynamic light patterning. Using Two Photon Polymerisation to fabricate detailed 3D micro-structures and holographic tweezers to measure the forces acting on them, the goal is to understand pressure in active systems and eventually design microstructures having optimal propulsion in active baths.

Discussion