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Tom R. Ladstätter

Publications and source records attributed to Tom R. Ladstätter.

2 recordsLinked to original sources

Cosmic Acceleration from Quantum Gravity: Emergent Inflation and Dynamical Dark Energy

We present a mechanism for the emergence of cosmic acceleration within the mean-field approximation of Group Field Theory models of quantum gravity. Depending on the interaction type, the resulting cosmological dynamics can either feature a late-time attractor corresponding to a dynamical dark energy phase, often with characteristic phantom behavior, including in models inspired by simplicial gravity, or instead support an early slow-roll inflationary epoch driven by the same underlying quantum-gravitational effects. This emergent inflation, effectively captured by a single-field description, can sustain the required expansion, naturally avoids the graceful exit problem, and appears to transition into a persistent, non-accelerating phase consistent with classical expectations.

gr-qc↗

Interacting Scalar Field Cosmology from Full Quantum Gravity

We study the relational cosmological dynamics emerging from interacting group field theory (GFT) models minimally coupled to a massless clock scalar field and a self-interacting scalar field. We focus on two broad classes of GFT interactions - pseudosimplicial and pseudotensorial - which generalize simplicial and tensorial interactions, respectively. Treating these interactions perturbatively, we extract the effective cosmological dynamics using mean-field techniques. In the geometric sector, we identify appropriate classical limits of the resulting dynamics, characterized by the emergence of a cosmological constant term in pseudotensorial models and of dynamical dark energy in pseudosimplicial ones. In the matter sector, we find that quantum gravity interactions induce a mass term and modify the classical symmetries of the scalar field dynamics, allowing for a consistent classical matter-geometry description only for specific forms of the effective scalar field potential. Finally, we show that these quantum gravity compatibility conditions on the effective potentials can be relaxed by allowing for a scale-dependent gravitational coupling, and that this running is uniquely fixed once the classical scalar field potential is specified.

gr-qc↗