arXiv subjects

D. Németh

Publications and source records attributed to D. Németh.

3 recordsLinked to original sources

arXiv2022

Topology induced first-order phase transitions in lattice quantum gravity

Causal Dynamical Triangulations (CDT) is a lattice formulation of quantum gravity, suitable for Monte-Carlo simulations which have been used to study the phase diagram of the model. It has four phases characterized by different dominant geometries, denoted phase $A$, $B$, $C$ and $C_b$. In this article we analyse the $A-B$ and the $B-C$ {phase} transitions in the case where the topology of space is that of the three-torus. This completes the phase diagram of CDT for such a spatial topology. We observe that the order of a phase transition of spacetime geometries can depend on the topology of spacetime.

hep-lat↗

arXiv2021

Matter-driven change of spacetime topology

Using Monte-Carlo computer simulations, we study the impact of matter fields on the geometry of a typical quantum universe in the CDT model of lattice quantum gravity. The quantum universe has the size of a few Planck lengths and the spatial topology of a three-torus. The matter fields are multi-component scalar fields taking values in a torus with circumference $δ$ in each spatial direction, which acts as a new parameter in the CDT model. Changing $δ$, we observe a phase transition caused by the scalar field. This discovery may have important consequences for quantum universes with non-trivial topology, since the phase transition can change the topology to a simply connected one.

hep-th↗

arXiv2021

Cosmic voids and filaments from quantum gravity

Using computer simulations we study the geometry of a typical quantum universe, i.e. the geometry one might expect before a possible period of inflation. We display it using coordinates defined by means of four classical scalar fields satisfying the Laplace equation with non-trivial boundary conditions. The field configurations reveal cosmic web structures surprisingly similar to the ones observed in the present-day Universe. Inflation might make these structures relevant for our Universe.

gr-qc↗