Lorentzian Quantum Gravity and the Graviton Spectral Function.

Area of Science:

• Theoretical Physics
• Quantum Gravity
• High Energy Physics

Background:

• Quantum gravity remains a significant challenge in theoretical physics, lacking a complete, nonperturbative description.
• Understanding the behavior of gravitons, the hypothetical quantum particles of gravity, is crucial for a unified theory.

Purpose of the Study:

• To perform the first direct and nonperturbative computation of the graviton spectral function.
• To explore the implications of asymptotic safety in quantum gravity.
• To investigate the influence of a cosmological constant on gravitational properties.

Main Methods:

• Utilized a novel Lorentzian renormalization group approach.
• Employed a spectral representation of correlation functions for direct computation.
• Incorporated a cosmological constant into the theoretical framework.

Main Results:

• Successfully computed a positive graviton spectral function.
• Identified a massless one-graviton peak and a multigraviton continuum.
• Observed an asymptotically safe scaling for large spectral values.
• Analyzed the impact of a cosmological constant on the spectral function.

Conclusions:

• The findings support the existence of asymptotic safety in quantum gravity.
• The computed spectral function provides insights into the quantum nature of gravity.
• Further research into scattering processes and unitarity is warranted.