General Relativity & Quantum Cosmology

Black-hole recoils are arguably the strong-gravity phenomena with the most striking astrophysical consequences. In the late inspiral and final coalescence of black-hole binaries, anisotropic emission of gravitational waves causes significant linear momentum loss. The remnant black hole, therefore, recoils in the opposite direction. These final kicks can reach magnitudes up to 5000 km/s (“superkicks”), larger than the escape speed of even the most massive galaxies, thus opening the possibility of black hole ejections. In this talk, I summarize recent advances in modeling black-hole recoils and their astrophysical environments. I will address the relevance of disk-assisted spin alignment, new approaches to model black-hole recoils with waveform approximants, and prospects to directly detect superkicks with gravitational-wave detectors.

Despite being broadly accepted nowadays, temperature gradients in thermal equilibrium states continue to cause confusion, since they naively seem to contradict the laws of classical thermodynamics. In this talk, we will explore the physical meaning behind this concept, specifically discussing the role played by the university of free fall. We will show that temperature, just like time, is an observer dependent quantity and discuss why gravity is the only force capable of causing equilibrium thermal gradients without violating any of the laws of thermodynamics. We will also demonstrate that significant care and delicacy are necessary when extending Tolman's results to distinct classes of heat baths in stationary spacetimes.

The entanglement entropy, while being under the spotlight of theoretical physics for more than ten years now, remains very challenging to compute, even in free quantum field theories, and a number of issues are yet to be explored.

One such issues concerns boundary effects on entanglement entropy, which is important both for theoretical explorations of entanglement and for applications of entanglement entropy to lattice simulations, condensed matter systems, etc.. During this talk, I will show how the presence of spacetime boundaries affects the entanglement entropy, with emphasize on universal (boundary-induced) logarithmic terms, using field theoretic, lattice, and holographic methods.