Topic
Research field seeking to reconcile general relativity with quantum mechanics, probing gravity at the smallest scales via theory and experiment.
Authors of a Physical Review Letters paper say they derive Einstein's equations from quantum relative entropy evaluated at a horizon. Their stated gain is mathematical rigor, since the ingredients were already known.
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OIST physicists used electron spins in a diamond to push a levitated 128-milligram assembly about 100 nanometers, they report in Science Advances. The motion was classical, so any quantum test at this scale still needs the object itself in superposition.
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Davide Batic and colleagues find quantum-gravity black hole cores ring up to 12% higher where gravity weakens and 25% lower where it strengthens. The opposite signs could in principle let a ringdown tell the models apart, though each figure is for a model pushed to its limit.
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OIST physicists pushed a levitated centimeter-wide diamond with electron spin, an object 8 to 9 orders of magnitude heavier than in earlier spin-mechanical tests. Its motion was classical, so the superposition a quantum-gravity test needs is still ahead of the team.
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Luis Anchordoqui's Lehman College team calculates that primordial black holes in a universe with a micron-wide hidden dimension would end up five-dimensional. The work links a proposed dark matter candidate to an extra dimension that has no more evidence behind it.
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Quanta's physics writer calls holography the most profound idea in theoretical physics in 30 years, built on three papers cited tens of thousands of times. The citations measure how many theorists took it up, and whether holography describes our own universe is the open question the essay sets out to answer.
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One path of a rubidium atom was held against gravity while the other fell freely, and the phase the two arms accumulated matches what Einstein's equivalence principle predicts for a quantum wave.
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A search of LHC collision data for microscopic quantum black holes found none. The exclusion limit that follows is the publishable result. Where that limit sits decides whether theorists have to move.
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Physicists under Italy's Gran Sasso mountain hunted the faint radiation that fluctuating spacetime should produce in a shielded germanium crystal. They found only background. One gravitational route to quantum collapse is now closed.
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Tamas Vami and Danyi Zhang looked through CMS data for microscopic black holes, found none, and published the bound. They also describe the search itself as a new way to look for new particles.
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A germanium detector at Gran Sasso listened for the faint radiation that a jittering spacetime should force out of charged particles, and the VIP collaboration reports it recorded none of it.
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A worldwide survey led from Waterloo and the Perimeter Institute records what working physicists believe about dark matter and quantum gravity, and the way its answer options were drawn shapes what those percentages can prove.
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A team supported by the Foundational Questions Institute calculated what two spontaneous collapse models imply for time and found an intrinsic uncertainty in it, many orders of magnitude below what today's atomic clocks can measure.
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A Physical Review D paper argues cosmic acceleration is a residue of quantum uncertainty acting on geometry, which would turn two unsolved problems into one. Upcoming surveys are the test.
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