12:35 PM - 01:20 PM (45 min)

Lighning talk session II

1. Binary systems of boson stars

12:35 PM – 12:44 PM

Pedro Ildefonso (Instituto Superior Técnico, University of Lisbon)

Gravitational physics has been, in the past 50 years, getting more attention than ever. Recently, the first detection of gravitational waves (GW) from a Black Hole (BH) - Black Hole, Neutron star (NS) – Neutron Star and BH-NS binaries gave a boost and a new enthusiasm to this study field. These new ways of studying the Universe not only allows the mapping of these compact objects but also opens a window on the detection and study of more exotic objects, like Boson Stars (BSs), which can mimic BH binaries. In my thesis I use the Einstein Toolkit framework to: evolve head-on collisions within two independent static BSs solutions; and doublet systems of dipolar BSs solutions (l=1, m=0) (both particular cases of a Q-ball solution). With these results I extract both the scalar field distribution and the l=m=2 mode of the real part of the GW signal.

2. Ringdown of compact objects

12:44 PM – 12:53 PM

Mostafizur Rahman (Indian Institute of Technology, Gandhinagar) (recording)

In recent years, several horizonless compact object models were proposed to address the problems associated with the existence of black holes. As the gravitational wave detectors started to observe more and more merger events with a large signal-to-noise ratio, gravitational wave spectroscopy could hold the key to uncover the existence of these objects. This is because the late time ringdown signals of horizonless compact objects differ from that of the black holes. In this talk, I will discuss the ringdown properties of compact objects and compare them with those obtained in the black hole scenario. Since the internal structure and the equation of state of these compact objects are largely unknown, we employ the membrane paradigm to obtain appropriate boundary conditions for the perturbations of these objects. This model can describe the ringdown properties of a large variety of compact objects.

3. Nonlinear Dynamics of Quadratic Gravity

12:53 PM – 01:02 PM

Aaron Held (Imperial College London)

I will present results on the first numerically stable nonlinear evolution for the leading-order gravitational effective field theory (Quadratic Gravity) in the spherically symmetric sector. The respective simulations (obtained in collaboration with Hyun Lim) provide numerical evidence for a well-posed initial-value formulation. As this provides a proof-of-principle for the possibility of stable numerical evolution in the presence of higher derivatives, I will also comment on the status of full 3+1 simulations in Quadratic Gravity.

4. Boson Star Initial data

01:02 PM – 01:11 PM

Thomas Helfer (Johns Hopkins University ) (recording)

We show a new way of generating initial data for binary Boson Stars, which reduces initial excitations significantly. We show that it will dramatically improve the quality of the extracted gravitational waves.