During this talk we shall discuss some properties of the semiclassical Einstein equation.

This equation is used to model the backreaction of quantum matter on classical backgrounds.

In this talk we shall in particular analyze the case of backgrounds which describe cosmological spacetimes.

The quantum field we shall consider is massive and satisfies a linear equation with a generic coupling...

A fresh attempt towards a quantum field theory of gravitons

interacting with matter is based on the Fock space quantization of

Wigner's helicity 2 representation, rather than canonical quantization

of a massless rank-2 tensor field. In this way, all issues with

indefinite state spaces, overshooting degrees of freedom, gauge fixing,

etc. are avoided. It turns out that quantum consistency...

The construction of a quantum gravity theory remains a challenge. One of the difficulties stems from the lack of sufficient experimental evidence. As a first step toward the quantum gravity experiment, Bose et al. proposed a low-energy experiment to test if Newtonian gravity can generate quantum entanglement or not. However, they assumed that only gravity is mediating in the system, and their...

The role of entropy, in particular entanglement entropy, in quantum field theory has become increasingly prominent, and entropy has appeared in relation with several primary research topics in QFT: area theorems, c theorems, the AdS/CFT correspondence, quantum null energy inequalities etc. While von Neumann entropy, the basic concept in information theory, is divergent in QFT and can thus only...

Recently, various experiments have been proposed to verify quantum entanglement induced by Newtonian gravitational interactions. However, no feasible setup has yet been found that is certainly achievable with existing techniques. To search for an optimal setup, we compute the logarithmic negativity of two oscillators with arbitrary quadratic potential and coupled by gravity. We find that...

Since the discovery of the Bekenstein-Hawking formula, there had been many attempts to derive the entropy of black holes from the entanglement between the degrees of freedom inside and outside the event horizon. This entanglement entropy reproduces the area-law, but it suffers from divergences in the continuum limit. In this talk, I show how to derive the Bekenstein-Hawking entropy from the...

We study the renormalised stress-energy tensor (RSET) for a massless, conformally

coupled scalar field on four dimensional anti-de Sitter space-time (adS4). As ads4 is

not a globally hyperbolic space-time, we impose boundary conditions on the space-time

boundary to have a well posed quantum field theory. We use Dirichlet, Neumann and

Robin (mixed) boundary conditions applied to the scalar...

We present a regularization prescription for Hadamard two-point functions defined on the boundary of a lightcone, which can be used to analyze renormalized quantities for linear scalar fields in a curved background. This can be applied to formulate the semi-classical Einstein equations as a characteristic initial value problem. Furthermore, we shall discuss how these tools can be used to...

We will discuss some newly found solutions to the full massless semiclassical Einstein equation (SCE) in a cosmological setting (with Λ=0).

After a short introduction to the relevant notions we present the SCE in a particular shape which allows for the construction of certain vacuum states. These states may be viewed as as the least possible generalization of the Minkowski vacuum to general...