## Mathematical experiments test quantum gravity theories

Newtonian gravitation is well described but its quantum counterpart is not. Scientists developed a formula to describe gravitational anomalies important to a quantum description of gravity that promises to shed light on the mystery.

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The Standard Model of particle physics is a broadly accepted theory of the particles and forces that make up the Universe. However, it has a few acknowledged gaps, one of the most important being that it does not include a satisfactory description of gravity. This is one of the most pressing open issues in particle physics today.

The graviton, the 'gravity' particle that is predicted to exist, may one day be found. For now, existing experimental techniques are forced to rely on mathematical descriptions of graviton, giving rise to gravitational anomalies. As an example for gravitational anomaly, we can consider the difference between actual planet movement measurements and the predicted movement from a model.

Quantum gravity is thus a concept of particle physics, and quantum field theory is a branch of mathematics that helps to describe and explain it. There are an infinite number of quantum field theories but the right systems of equations providing self-consistency need to be applied. In other words, the right equations and the conditions that can solve these equations need to be determined.

Scientists initiated the EU-funded project 'Defects in two dimensional field theories' (D2DFT) to investigate specific consistency conditions not well characterised to date — that is, the cancellation of global gravitational anomalies in the field theory description at low energies. Two field theories related to supergravity — string theory and M-theory, give rise to gravitational anomalies. The anomaly formula has been known for the one since the 1980s but has remained out of reach for the second (the so-called self-dual field theory).

Researchers successfully determined the formula for the global gravitational anomaly of self-dual field theories. This has important implications in the field of mathematics and particle physics, leading to an eventual description of quantum gravity. Work encompassed a broad mix of mathematical subfields and scientists are currently exploring the cancellation of global gravitational anomalies to evaluate concepts related to quantum gravity. Gravity may be the glue that holds the Universe together. Scientists are one step closer to defining it on a quantum level — physically and mathematically, thanks to work carried out by the D2DFT project.

The graviton, the 'gravity' particle that is predicted to exist, may one day be found. For now, existing experimental techniques are forced to rely on mathematical descriptions of graviton, giving rise to gravitational anomalies. As an example for gravitational anomaly, we can consider the difference between actual planet movement measurements and the predicted movement from a model.

Quantum gravity is thus a concept of particle physics, and quantum field theory is a branch of mathematics that helps to describe and explain it. There are an infinite number of quantum field theories but the right systems of equations providing self-consistency need to be applied. In other words, the right equations and the conditions that can solve these equations need to be determined.

Scientists initiated the EU-funded project 'Defects in two dimensional field theories' (D2DFT) to investigate specific consistency conditions not well characterised to date — that is, the cancellation of global gravitational anomalies in the field theory description at low energies. Two field theories related to supergravity — string theory and M-theory, give rise to gravitational anomalies. The anomaly formula has been known for the one since the 1980s but has remained out of reach for the second (the so-called self-dual field theory).

Researchers successfully determined the formula for the global gravitational anomaly of self-dual field theories. This has important implications in the field of mathematics and particle physics, leading to an eventual description of quantum gravity. Work encompassed a broad mix of mathematical subfields and scientists are currently exploring the cancellation of global gravitational anomalies to evaluate concepts related to quantum gravity. Gravity may be the glue that holds the Universe together. Scientists are one step closer to defining it on a quantum level — physically and mathematically, thanks to work carried out by the D2DFT project.