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5 Dimensional Black Hole Could Spell Doom For General Relativity

Theoretical physicists from the University of Cambridge and the Queen Mary University in London have conceived a hypothetical scenario that could potentially lead to a breakdown of Albert Einstein’s General Theory of Relativity. This approach would be only valid for universes having at least five dimensions. The research team has simulated a mathematical model consisting of 5D black holes which could in principle 'break' General Relativity.

The team modelled a black hole in the form of a thin ring which generates ‘bulges’, connected by strings growing thinner with time. These connections become so thin that they eventually get separated from the main frame and gives birth to miniature black holes. Owing to the earlier discovery of ring shaped black holes in 2002, scientists succeeded in simulating them in the laboratory for the first time, using advanced computing techniques.

Considered as the foundation of modern physics, the General theory of relativity is the root of our current understanding of universe. The GTR implies that gravity could be expressed using geometric properties of space and time. In short, the curvature of space and time is directly proportional to the energy or momentum of matter or radiation present. What makes this new discovery even more startling is that since its formulation, GTR has stood the test of time and almost all its predictions have been confirmed with the latest being the discovery of Gravitational Waves.

Structure shifts of ring sized black hole

Einstein had also predicted the presence of singularities, which according to him existed at the centre of Black holes. As the name suggests, singularities are points in space-time where gravity is unimaginably intense, resulting in space, time and all physical laws to collapse. The singular points hypothetically exist in the center of a mathematical black hole, surrounded by the ‘event horizon’- the point of no return. Here, gravity becomes so strong that nothing can escape, not even light.

The Cosmic Censorship conjecture states that singularities are always present behind the event horizon. GTR is still valid in such cases and it is possible to predict the events outside the black hole. However, the team questioned the notion that all black holes are hidden behind the event horizon and hinted at the possibility of such 'naked singularities'. What if the singularity is observable? This would lead to a complete breakdown of General Relativity and all predictive power would be lost at this state of infinite density.

Saran Tunyasuvunakool, a PhD student from Cambridge's DAMTP explained that although see the world in three dimensions and count time as the fourth one, in theoretical physics and especially in ‘String Theory’, the universe could be made up of as many as 11 dimensions. The reason why we don't witness these dimensions is because of a process known as compactification, where dimensions may be ultra small and coiled up in a way, making them difficult to detect. Particle Accelerators like the LHC could however, find signatures of such extra dimensions.

Scientists used the COSMOS supercomputer to simulate Einstein’s GTR in higher dimensions which ultimately confirmed that such black rings are unstable and segregate with time, analogous to drops of water emerging from a tap. In most cases, the black ring collapses back into the sphere concealing the singularity inside the event horizon. However, in a very special case the thinnest chain gives birth to a ‘naked singularity’, outside the event horizon.

In future, the team would perform a reverse process to ascertain what’s special in 4D systems that keeps the ‘Cosmic Censor Conjecture’ true. The research was published in the Physical Review Letters. The research was supported by the Science and Technology Facilities Council (STFC) DiRAC HPC Facility.

Watch the very thin Black hole here:

Source: University of Cambridge | Physical Review Letters

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