Thermodynamic Approaches to Quantum Gravity: Discussion

[BaronBautista]

TL;DR

Can gravity be an emergent phenomenon from spacetime thermodynamics, as Jacobson (1995) suggests? How might this apply to quantum gravity at the Planck scale? Thoughts?

Jacobson’s work (1995) [1] demonstrated that Einstein’s equations can be derived from thermodynamic principles, suggesting gravity might emerge from the thermodynamic behavior of spacetime, tied to the entropy of horizons. Other researchers, such as Bekenstein [2] and Verlinde [3], have explored similar ideas, linking gravity to entropy and holographic principles.


I’m interested in discussing how these thermodynamic approaches might apply to quantum gravity, particularly at the Planck scale. For instance, could quantum corrections to spacetime entropy—such as logarithmic terms inspired by conformal field theory and black hole entropy studies—produce observable gravitational effects, like changes in Hawking radiation from primordial black holes? Or might they imply a discrete spacetime structure, aligned with the holographic principle? Additionally, in high-curvature regimes like the early universe, could curvature-dependent entropy terms play a role in gravitational dynamics, as suggested by Penrose’s ideas on low gravitational entropy at the universe’s beginning?


References:
[1] Jacobson, T. (1995). "Thermodynamics of Spacetime: The Einstein Equation of State," Physical Review Letters.
[2] Bekenstein, J. D. (1973). "Black Holes and Entropy," Physical Review D.
[3] Verlinde, E. (2011). "On the Origin of Gravity and the Laws of Newton," Journal of High Energy Physics.

[Mentors' note: this post has been edited to remove references to an unpublished work. The forum rules require that papers must have been published in an appropriate peer-reviewed journal before they can be discussed here]

 

[sbrothy]

I'm not as smart as you guys I admit, but I stumbled over this recent [Submitted on 7 May 2025] paper which at least touches a little on the subject and mentions other papers along the same lines (and then of course no one else seemed to be answering...).

Why Do We Want a Theory of Quantum Gravity?

"The search for a new scientific theory is typically prompted by an encounter with something in the world that cannot be explained by current theories. This is not the case for the search for a theory of quantum gravity, which has been primarily motivated by theoretical and philosophical concerns. This Element introduces some of the motivations for seeking a theory of quantum gravity, with the aim of instigating a more critical perspective on how they are used in defining and constraining the theory sought. These motivations include unification, incompatibilities between general relativity and quantum field theory, consistency, singularity resolution, and results from black hole thermodynamics."