An article exploring the revival of quadratic gravity, a 1977 theory initially dismissed for its negative-energy "ghost" particles, which physicists now believe may be manageable and even offer insights into quantum gravity and cosmic inflation.
Quadratic gravity is renormalizable, meaning it avoids infinities that plague other quantum gravity theories, and it offers new predictions and insights into cosmic inflation and the nature of space-time. Researchers are exploring modifications to quantum field theory rules to accommodate these ghost particles without violating fundamental principles like unitarity and causality. The theory is gaining renewed interest as alternative approaches like string theory falter, and it may offer a path toward understanding gravity at a quantum level.
Quadratic gravity is renormalizable, meaning it avoids infinities that plague other quantum gravity theories, and it offers new predictions and insights into cosmic inflation and the nature of space-time. Researchers are exploring modifications to quantum field theory rules to accommodate these ghost particles without violating fundamental principles like unitarity and causality. The theory is gaining renewed interest as alternative approaches like string theory falter, and it may offer a path toward understanding gravity at a quantum level.
The theoretical physicist and best-selling author finds inspiration in politics and philosophy for rethinking space and time.
Carlo Rovelli's work focuses on reconciling general relativity and quantum mechanics through **Loop Quantum Gravity (LQG)**, which proposes that spacetime is discrete and emerges from interactions, not as a pre-existing background. He also advocates for **Relational Quantum Mechanics**, asserting reality is defined by interactions and perspective – there is no objective, observer-independent reality. A key idea is that **time is not fundamental** but an emergent property linked to entropy. While promising, LQG faces challenges in making testable predictions.
Essentially, Rovelli argues for a shift from seeking absolute truths to understanding a relational, perspective-dependent universe.
Carlo Rovelli's work focuses on reconciling general relativity and quantum mechanics through **Loop Quantum Gravity (LQG)**, which proposes that spacetime is discrete and emerges from interactions, not as a pre-existing background. He also advocates for **Relational Quantum Mechanics**, asserting reality is defined by interactions and perspective – there is no objective, observer-independent reality. A key idea is that **time is not fundamental** but an emergent property linked to entropy. While promising, LQG faces challenges in making testable predictions.
Essentially, Rovelli argues for a shift from seeking absolute truths to understanding a relational, perspective-dependent universe.
This paper presents a model where gravity, through its fundamental unification with matter, explains the collapse of the wavefunction. The model is local, parameter-free, and makes testable predictions, proposing that the time evolution of quantum states deviates from the Schrödinger equation due to gravitational effects, leading to a natural explanation for why macroscopic superpositions do not occur.
A new theoretical framework utilizing three dimensions of time, arising from symmetries observed across quantum, interaction, and cosmological scales. This framework naturally explains the three generations of particles and their mass hierarchy, offering solutions to problems in particle physics like parity violation and ultraviolet divergences in quantum gravity. The theory makes testable predictions for neutrino masses, new resonances at colliders, and modifications to the speed of gravity, potentially verifiable within the next few years.
A recent study proposes that the universe functions as a vast quantum gravity computer, processing information at the Planck scale at an incredible rate, potentially influencing how physicists view cosmic interactions and energy conservation.
This article presents a white paper summarizing current knowledge on quantum gravity phenomenology and its multi-messenger signals. It provides an overview of the field, discusses experimental and observational signatures, and identifies key questions and challenges.
