GR20/Amaldi10: Space-time is not the same for everyone

Before the Big Bang, space-time as we know it did not exist. So how was it born? The process of creating normal space-time from an earlier state dominated by quantum gravity has been studied for years by theorists at the Faculty of Physics, University of Warsaw. Recent analyses suggest a surprising conclusion: not all elementary particles are subject to the same space-time.

Several billion years ago, in the era soon after the Big Bang, the Universe was so dense and so hot that elementary particles felt the existence of gravity strongly. For decades, physicists around the world have been attempting to discover the laws of quantum gravity describing this phase of the evolution of the Universe. Recently Professor Jerzy Lewandowski's group at the Faculty of Physics, University of Warsaw (FUW) proposed its own model of the quantum Universe. Recent studies of its properties, discussed during the 20th International Conference on General Relativity and Gravitation (GR20), being held in Warsaw in conjunction with the 10th Edoardo Amaldi Conference on Gravitational Waves (Amaldi10), have surprised researchers. The analyses performed by Prof. Lewandowski and his PhD student Andrea Dapor show that different elementary particles "experience" the existence of different space-times.

One of the attempts to describe quantum gravity is called loop quantum gravity (LQG). This theory assumes that space-time is structurally somewhat similar to a fabric: It consists of a large number of very small fibres entangled in loops. A field with an area of one square centimetre might hold a million trillion trillion trillion trillion trillion (10^66) such fibres.

Three years ago, Prof. Lewandowski's group developed a consistent mathematical model of LQG that combines quantum mechanics with general relativity. The model assumes the existence of two interacting fields. One is a gravitational field, which can be identified with a space (since, according to the general theory of relativity, gravity warps space-time, and this curved space-time gives rise to gravitational effects). The second field in the model is a (scalar) field that assigns a number to each point in space. This field is interpreted as the simplest type of matter.