Tag

Quantum Gravity

All articles tagged with #quantum gravity

science6 days ago•52 min saved

Cosmic Acceleration May Be a Signature of Quantum Gravity on the Horizon

Physicist Savvas Koushiappas suggests the Universe’s accelerating expansion could arise from a quantum modification to cosmic geometry at the cosmological horizon, meaning dark energy might be replaced by a macroscopic imprint of quantum gravity. By tying the uncertainty in simultaneously knowing the Universe’s size and expansion rate to altered expansion equations, the model could explain acceleration and even allow a bouncing origin instead of a Big Bang, though it leaves several questions unresolved. Future data from DESI, Euclid, and the Vera Rubin Observatory could test these ideas and refine our understanding of cosmic expansion.

via Yahoo|

#cosmological-horizon #cosmology #dark-energy

science6 days ago•5 min saved

Cosmic Acceleration Could Be a Quantum Gravity Imprint, Not Dark Energy

A new Physical Review D paper by Savvas Koushiappas suggests the Universe’s accelerating expansion may arise from a macroscopic quantum uncertainty in simultaneously knowing the Universe’s size and expansion rate, effectively tying cosmic acceleration to quantum gravity at the cosmological horizon rather than to dark energy. The model can modify the expansion history and even allow a Big Bang replacement by a bounce in some configurations. Observations from DESI, Euclid, and the Vera C. Rubin Observatory could test these ideas, but the proposal remains speculative with open questions about consistency and interpretation.

via ScienceAlert|

#cosmological-horizon #cosmology #dark-energy

science27 days ago•7 min saved

Black Hole Singularity Might Be a 3D Surface, Not a Point

A forthcoming Physical Review D paper argues that Schwarzschild (and likely Kerr) singularities are better described as flat, three-dimensional spacelike surfaces rather than points. This means two observers falling in from opposite directions cannot converge on the same spacetime event, a result that could reshape how general relativity breaks down inside black holes and redefine the starting point for quantum gravity research.

via ScienceAlert|

#black-hole #general-relativity #quantum-gravity

science1 month ago•8 min saved

Gravity Emerges from Entropy: A Thermodynamic View of the Cosmos

Physicist Ginestra Bianconi proposes Gravity from Entropy (GfE), a quantum gravity framework in which gravity arises from an information-theoretic tension between two spacetime metrics. They find total entropy increases with cosmic expansion while entropy per unit volume falls, allowing local structure to form even as the universe trends toward disorder. GfE reduces to General Relativity at low energies but includes a dynamical dark-energy term that could yield observable effects, offering a potential bridge between gravity, thermodynamics, and quantum theory.

via SciTechDaily|

#cosmology #entropy #gravity

science1 month ago•4 min saved

From Planes to Spacetime: Sabrina Pasterski’s Quantum Gravity Quest

Sabrina Gonzalez Pasterski, a Chicago-born prodigy who built and solo-flied a plane as a teen, topped MIT physics, earned a Harvard PhD, and contributed to quantum gravity and the spin memory effect (cited by Hawking). She turned down lucrative offers from Blue Origin, Brown University, and NASA, and joined the Perimeter Institute in 2021 as the youngest faculty member, where she founded the Celestial Holography Initiative. In 2023, the Simons Foundation granted $8 million to support her collaborative work linking spacetime with quantum theory.

via The Times of India|

#celestial-holography-initiative #perimeter-institute #quantum-gravity

science1 month ago•4 min saved

Lab-created quantum mini-universe hints time can arise from entropy, not a clock

Physicists built a 24,000-atom isolated quantum system that behaves like a tiny universe, showing time can emerge from internal entropy changes rather than an external clock—the enigmatic "entropic time"—and maintain standard quantum dynamics, offering a controlled testbed for quantum cosmology and gravity research.

via ScienceDaily|

#entropy #laboratory-experiment #quantum-gravity

science1 month ago•121 min saved

Direct-wave signal near a black hole horizon opens a new window on gravity

Researchers analyzed a very strong gravitational-wave event (GW250114) detected by LIGO on Jan. 14, 2025 and found evidence of a “direct wave” produced from near the horizon of the newly formed black hole. The signal, matching theoretical predictions, could allow astronomers to study the region just outside the event horizon using gravitational waves, potentially testing general relativity and informing ideas about quantum gravity and the black hole information paradox. However, the claim rests on a single observation, so further detections are needed to confirm this as a universal feature of black hole mergers.

via Live Science|

#black-holes #event-horizon #gravitational-waves

science1 month ago•13 min saved

Time as an Emergent Phenomenon: Clocks Inside the Universe, Not a Fundamental Backdrop

A Space Daily piece outlines the view that time may not be a fundamental feature of reality; in quantum gravity, the Wheeler–DeWitt equation lacks an external clock, while the Page–Wootters idea shows time could arise from correlations between subsystems within the universe. Entropy and thermodynamics may explain the arrow of time, and experiments like Moreva illustrate relational time—yet the notion remains unresolved and not a claim that time is fake, just that its deepest description may be clockless.

via Space Daily|

#page-wootters #quantum-gravity #relational-time

space1 month ago•43 min saved

Time Emerges from Quantum Entanglement, Not a Universal Backdrop

A theoretical study revisits the Page and Wootters idea and argues that time may not be a fundamental backdrop but arises from the entangled relationship between a clock and a system. Using a two-system model (a clock and an oscillator), the work shows that when these subsystems are properly entangled, ordinary quantum motion can emerge and, in the macroscopic/classical limit, the familiar time of classical physics and Schrödinger dynamics appears. The research also notes the clock’s limits in fully quantum regimes and emphasizes the need for the clock to behave classically for time to emerge, while stressing that experimental confirmation remains out of reach and the idea remains speculative.

via The Brighter Side of News|

#emergent-time #general-relativity #page-and-wootters-mechanism

physics2 months ago•8 min saved

Bootstrapping String Theory: From Minimal Constraints to a Unique High-Energy Description

A bootstrap analysis shows that, under ultrasoft high-energy behavior and the assumption that Regge zeros are the only zeros, the 4- and 5-point scattering amplitudes for identical scalars are uniquely fixed to the string-theory form, implying string dynamics may emerge from fundamental consistency principles rather than being assumed a priori. Built on Lorentz invariance, crossing symmetry, positivity, and analyticity, the result supports string universality but depends on whether these inputs can be independently justified or if other assumptions yield the same outcome.

via American Physical Society|

#bootstrap #high-energy-physics #physics

science2 months ago•6 min saved

Topology Could Tame the Cosmological Constant

Brown University researchers argue that space-time topology in the CSK (Chern-Simons-Kodama) approach to quantum gravity could stabilize the cosmological constant at a small, quantized value by a mechanism analogous to the quantum Hall effect's topological protection, offering a potential path to reconciling vacuum energy with the universe’s expansion.

via ScienceDaily|

#chern-simons-kodama #cosmological-constant #quantum-gravity

science2 months ago•9 min saved

Time Emerges from Entropy in a Lab Mini-Universe

A University of Birmingham team built a sealed quantum system of 24,000 ultracold rubidium atoms that mimics a tiny expanding/contracting universe and found that the flow of time can arise from internal entropy changes rather than an external clock. The experiment demonstrates entropic time, provides experimental support for time as a derived property in some quantum gravity theories, and shows the Schrödinger equation can be expressed with entropic time, offering a new laboratory testbed for quantum cosmology and gravity ideas.

via SciTechDaily|

#emergent-time #entropy #quantum-gravity

science2 months ago•96 min saved

Quantum gravity narrows the hunt for a possible fifth fundamental force

A new quantum gravity framework based on asymptotic safety narrows the parameter space for a hypothetical fifth fundamental force, ruling out part of the possible strength and range and suggesting that high-precision gravity experiments—like atomic interferometry and lunar laser ranging—could test these ideas and potentially reveal observable effects of quantum gravity at macroscopic scales.

via Space|

#asymptotic-safety #atomic-interferometry #fifth-fundamental-force

science2 months ago•10 min saved

Lab-made 24,000-atom cosmos hints time can emerge from entropy

Researchers built a sealed, two-region quantum system of 24,000 ultracold rubidium atoms that behaves like a tiny universe, cycling between expansion and contraction without any external clock. Time appears to flow from internal changes in entropy (entropic time), allowing the sequence of events to be inferred from within the system and offering a controllable testbed for ideas in quantum gravity and early-universe physics. The study also shows Schrödinger dynamics can be reformulated under this time concept and could help probe fundamental questions about the origin of time.

via Interesting Engineering|

#entropic-time #mini-universe #nature-of-time

science2 months ago•3 min saved

Topology Reveals Global Shape of Black Hole Thermodynamics

Black holes are not just features of their accretion disks: they possess intrinsic temperature and entropy, and topology is used to classify their thermodynamic behavior. By identifying special zero points in the thermodynamic landscape and assigning them topological charges, physicists derive a global fingerprint that distinguishes different black-hole types (such as Schwarzschild vs. Reissner–Nordström) while remaining robust to changes in mass, charge, or spin; this approach links stability and state transitions to invariant properties and could illuminate paths toward quantum gravity, with implications for light rings and spacetime bending.

via Universe Today|

#astrophysics #black-holes #quantum-gravity