Energy nonconservation as a link between $f(R,T)$ gravity and noncommutative quantum theory

Abstract

$f(R,T)$ gravity was proposed as an extension of the $f(R)$ theories, containing not just geometrical correction terms to the General Relativity equations, but also material correction terms, dependent on the trace of the energy-momentum tensor $T$. These material extra terms prevent the energy-momentum tensor of the theory to be conserved, even in a flat background. Energy nonconservation is a prediction of quantum theory with time-space noncommutativity. If time is considered as an operator and there are compact spatial coordinates which do not commute with time, then the time evolution gets quantized and energy conservation can be violated. In the present work we construct a model in a 5-dimensional flat spacetime consisting of 3 commutative spatial dimensions and 1 compact spatial dimension whose coordinate does not commute with time. We show that energy flows from the 3-dimensional commutative slice into the compact extra dimension (and vice-versa), so that conservation of energy is restored. In this model the energy flux is proportional to the energy density of the matter content, leading to a differential equation for $f(R,T)$, thus providing a physical criterion to restrict the functional form of $f(R,T)$. We solve this equation and analyze the behavior of its solution in a spherically symmetric context.

Accepted version

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• To conserve, or not to conserve: A review of nonconservative theories of gravity
• Neutron stars in $f(R,T)$ gravity with conserved energy-momentum tensor: Hydrostatic equilibrium and asteroseismology
• A conservative energy-momentum tensor in the $f(R,T)$ gravity and its implications for the phenomenology of neutron stars
• Stable and self consistent charged gravastar model within the framework of $f(R,T)$ gravity
• General approach to the Lagrangian ambiguity in $f(R,T)$ gravity
• Slow-roll inflation in $f(R,T)$ gravity with a $RT$ mixing term
• Rapidly rotating neutron stars in $f(R,T)$ gravity
• The trace of the trace of the energy-momentum tensor-dependent Einstein's field equations
• Plane symmetric model in $f(R,T)$ gravity
• LRS Bianchi I model with constant expansion rate in $f(R,T)$ gravity
• Inflationary Cosmology in a non-minimal $f(R,T)$ gravity theory using a $RT$ mixing term
• Well behaved class of Heintzmann's solution within $f(R,T)$ framework
• Intermediate Coupling Regime in Dilatonic $f(R,T)$ Inflationary Universe
• A MOND model applied to the rotation curve of galaxies