Theoretical physics

Quantum mechanics has at last been formulated exclusively with real numbers, bringing a mathematical puzzle at the heart of the theory into a new era of inquiry.

The theoretical physicist and best-selling author finds inspiration in politics and philosophy for rethinking space and time.

The amplituhedron, a shape at the heart of particle physics, appears to be deeply connected to the mathematics of paper folding.

“Anomalous” heat flow, which at first appears to violate the second law of thermodynamics, gives physicists a way to detect quantum entanglement without destroying it.

According to Einstein’s theory of gravity, black holes have only a small handful of distinguishing characteristics. Quantum theory implies they may have more. Now an experimental search finds that any of this extra ‘hair’ has to be pretty short.

A new argument explores how the growth of disorder could cause massive objects to move toward one another. Physicists are both interested and skeptical.

Promise and controversy continues to surround string theory as a potential unified theory of everything. In the latest episode of The Joy of Why, Cumrun Vafa discusses his progress in trying to find good, testable models hidden among the ‘swampland’ of impossible universes.

Black hole and Big Bang singularities break our best theory of gravity. A trilogy of theorems hints that physicists must go to the ends of space and time to find a fix.

In math and computer science, researchers have long understood that some questions are fundamentally unanswerable. Now physicists are exploring how even ordinary physical systems put hard limits on what we can predict, even in principle.