Atoms of Spacetime and the Nature of Gravity

Emergent Quantum Mechanics 2015

Padmanabhan, Thanu^1

IUCAA, Pune University Campus, Ganeshkhind, Pune

411007, India^1

关键词: Field equation;    Geodesic distances;    Geodesic surfaces;    Gravitational field equations;    Heat density;    Lagrangian;    Matter field;    Zero point;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/701/1/012018/pdf
DOI  :  10.1088/1742-6596/701/1/012018

来源: IOP

【 摘 要 】

I clarify the differences between various approaches in the literature which attempt to link gravity and thermodynamics. I then describe a new perspective1based on the following features: (1) As in the case of any other matter field, the gravitational field equations should also remain unchanged if a constant is added to the Lagrangian; in other words, the field equations of gravity should remain invariant under the transformation Tab→ Tab+ δab(constant). (2) Each event of spacetime has a certain number (f) of microscopic degrees of freedom ('atoms of spacetime'). This quantity f is proportional to the area measure of an equi-geodesic surface, centered at that event, when the geodesic distance tends to zero. The spacetime should have a zero-point length in order for f to remain finite. (3) The dynamics is determined by extremizing the heat density at all events of the spacetime. The heat density is the sum of a part contributed by matter and a part contributed by the atoms of spacetime, with the latter being LP-4f. The implications of this approach are discussed.