Theoretical physics

Inside of a black hole, the two theoretical pillars of 20th-century physics appear to clash. Now a group of young physicists think they have resolved the conflict by appealing to the central pillar of the new century — the physics of quantum information.

The puzzling behavior of black hole interiors has led researchers to propose a new physical law: the second law of quantum complexity.

Several areas of physics suggest reasons to think that unobservable universes with different natural laws could lie beyond ours. The theoretical physicist David Kaplan talks with Steven Strogatz about the mysteries that a multiverse would solve.

A new phase of matter called a “time crystal” plays with our expectations of thermodynamics. The physicist Vedika Khemani talks with Steven Strogatz about its surprising quantum behavior.

Last fall, a team of physicists announced that they had teleported a qubit through a holographic wormhole in a quantum computer. Now another group suggests that’s not quite what happened.

Using “refreshingly old” tools, mathematicians resolved a 50-year-old conjecture about how to categorize important functions called modular forms, with consequences for number theory and theoretical physics.

New calculations suggest that the event horizons around black holes will ‘decohere’ quantum possibilities — even those that are far away.

Richard Feynman’s path integral is both a powerful prediction machine and a philosophy about how the world is. But physicists are still struggling to figure out how to use it, and what it means.

Two teams have made photons act as if time were simultaneously flowing in two directions. The experiments demonstrate a way to potentially boost the performance of quantum devices.