Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userBohmian quantum gravity and cosmology
67
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Quantum gravity aims to describe gravity in quantum mechanical terms. How exactly this needs to be done remains an open question. Various proposals have been put on the table, such as canonical quantum gravity, loop quantum gravity, string theory, etc. These proposals often encounter technical and conceptual problems. In this chapter, we focus on canonical quantum gravity and discuss how many conceptual problems, such as the measurement problem and the problem of time, can be overcome by adopting a Bohmian point of view. In a Bohmian theory (also called pilot-wave theory or de Broglie-Bohm theory, after its originators de Broglie and Bohm), a system is described by certain variables in space-time such as particles or fields or something else, whose dynamics depends on the wave function. In the context of quantum gravity, these variables are a space-time metric and suitable variable for the matter fields (e.g., particles or fields). In addition to solving the conceptual problems, the Bohmian approach yields new applications and predictions in quantum cosmology. These include space-time singularity resolution, new types of semi-classical approximations to quantum gravity, and approximations for quantum perturbations moving in a quantum background.
rate research
Read More
I will briefly discuss three cosmological models built upon three distinct quantum gravity proposals. I will first highlight the cosmological role of a vector field in the framework of a string/brane cosmological model. I will then present the resolution of the big bang singularity and the occurrence of an early era of accelerated expansion of a geometric origin, in the framework of group field theory condensate cosmology. I will then summarise results from an extended gravitational model based on non-commutative spectral geometry, a model that offers a purely geometric explanation for the standard model of particle physics.
We construct a generalized class of quantum gravity condensate states, that allows the description of continuum homogeneous quantum geometries within the full theory. They are based on similar ideas already applied to extract effective cosmological dynamics from the group field theory formalism, and thus also from loop quantum gravity. However, they represent an improvement over the simplest condensates used in the literature, in that they are defined by an infinite superposition of graph-based states encoding in a precise way the topology of the spatial manifold. The construction is based on the definition of refinement operators on spin network states, written in a second quantized language. The construction lends itself easily to be applied also to the case of spherically symmetric quantum geometries.
We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynmans formulation of Einsteins theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.
Quantum illumination is a quantum sensing technique where entanglement is exploited to improve the detection of low-reflectivity targets in a strong thermal background. In this paper, we study the quantum illumination of suspected targets under the curved spacetime background of the Earth. It is counterintuitive to find that to achieve the same error-probability both target detection scenarios, the illumination strategy curved spacetime consumes less resources than the flat spacetime strategy. That is to say, the gravitational effect of the Earth can promote the efficiency of quantum spatial target detection. This is because the average particle number of the thermal signal reflected in the curved spacetime is always less than the number in flat spacetime. We also find that the spatial quantum target detection with bipartite entangled state is more efficient than the coherent state strategy in the curved spacetime.
Experiments have recently been proposed testing whether quantum gravitational interactions generate entanglement between adjacent masses in position superposition states. We propose potentially less challenging experiments that test quantum gravity against theories with classical space-times defined by postulating semi-classical gravity (or classical effects of similar scale) for mesoscopic systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
