Formulating precise definitions of conserved charges like energy-momentum and angular momentum in General Relativity is extremely challenging. Instead of entering directly into the stress-energy tensor, gravitational energy manifests as an obstruction to integrating the local stress-energy conservation law to yield globally conserved charges. A very nice quasi-local definition for mass was...
Traversable wormholes have captivated the interest of the public and of theoretical physicists since their inception, with a recent resurgence of interest in the context of holography. While wormhole geometries are permissible within the framework of general relativity, they require matter with "negative energy" to sustain them; specifically, the matter must violate the null energy condition...
Classical singularity theorems and topological‑censorship arguments seem to forbid the formation of a wormhole in 4‑dimensional general relativity, even at the kinematical level, through the emergence of naked singularities. I will present a concrete example, developed in [1], in which the would‑be singular set is excised and replaced by a controlled 0‑surgery on a compact spacetime...
Observers have always played a central role in quantum mechanics, yet their consistent incorporation into quantum gravity remains poorly understood. In asymptotically flat spacetimes, this issue becomes especially acute due to the infrared structure of gravity and the infinite-dimensional BMS symmetry group, which render the definition of observables highly nontrivial. In standard quantum...
We study propagation of high-frequency electromagnetic and gravitational waves in the gravitational field of a rotating black hole. Due to the interaction of the spin of the field with the spacetime curvature, the standard geometric optics approximation that is used for obtaining the approximate high-frequency solutions of the wave equation should be modified. The corresponding modified...
