Bubble of nothing

In theoretical physics, a bubble of nothing is a physical instability that is found in higher-dimensional spacetime models. It was first described by Edward Witten in 1982, as a consequence of the positive energy theorem failing in semiclassical gravity.^[1]^[2]^[3] It is a non-perturbative decay channel of Kaluza–Klein theory, in which spacetime can spontaneously collapse through the nucleation of a gravitational instanton.^[3] The collapse of the extra dimensions then propagates outward at the speed of light, similarly to the bubbles formed in false vacuum decay, pushing along objects that impact it.^[2]^[1] This bubble of nothing has no interior, not even spacetime.^[2]^[3] Bubbles of nothing are forbidden in models that include supersymmetry.^[3]

It has been considered as an hypothetical end of the universe mechanism.^[4] The decay rate for a Kaluza–Klein vacuum is roughly of order $e^{-\pi R^{2}c/4G\hbar }$ , where $R$ is the radius of the fifth dimension and $G$ is the gravitational constant in 4 dimensions.^[1] As bubbles of nothing have not been observed, their absence can be used to put constraints on other theories.^[4] In addition, the outer wall of a bubble of nothing resembles a de Sitter space, and Giuseppe Dibitetto has proposed that our universe might lie on the surface of an expanding bubble of nothing in a 5-dimensional ambient space.^[5]

References

1 2 3 Witten, Edward (1982-02-22). "Instability of the Kaluza-Klein vacuum". Nuclear Physics B. 195 (3): 481–492. doi:10.1016/0550-3213(82)90007-4. ISSN 0550-3213.
1 2 3 Wood, Charlie (2022-08-09). "How the Physics of Nothing Underlies Everything". Quanta Magazine. Retrieved 2025-08-18.
1 2 3 4 Ong, Yen Chin (2015-11-27). Evolution of Black Holes in Anti-de Sitter Spacetime and the Firewall Controversy. Springer. ISBN 978-3-662-48270-4.
1 2 Minsky, Carly (2020-03-05). "Physicists Are Studying Mysterious 'Bubbles of Nothing' That Eat Spacetime". VICE. Retrieved 2025-08-18.
↑ Dibitetto, Giuseppe; Petri, Nicolò; Schillo, Marjorie (10 August 2020). "Nothing really matters". Journal of High Energy Physics. 2020 (8). arXiv:2002.01764. doi:10.1007/JHEP08(2020)040.

External links

A bubble of absolute nothing on YouTube by Sixty Symbols

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[witten1982-1] 1 2 3 Witten, Edward (1982-02-22). "Instability of the Kaluza-Klein vacuum". Nuclear Physics B. 195 (3): 481–492. doi:10.1016/0550-3213(82)90007-4. ISSN 0550-3213.

[:0-2] 1 2 3 Wood, Charlie (2022-08-09). "How the Physics of Nothing Underlies Everything". Quanta Magazine. Retrieved 2025-08-18.

[:2-3] 1 2 3 4 Ong, Yen Chin (2015-11-27). Evolution of Black Holes in Anti-de Sitter Spacetime and the Firewall Controversy. Springer. ISBN 978-3-662-48270-4.

[:1-4] 1 2 Minsky, Carly (2020-03-05). "Physicists Are Studying Mysterious 'Bubbles of Nothing' That Eat Spacetime". VICE. Retrieved 2025-08-18.

[5] Dibitetto, Giuseppe; Petri, Nicolò; Schillo, Marjorie (10 August 2020). "Nothing really matters". Journal of High Energy Physics. 2020 (8). arXiv:2002.01764. doi:10.1007/JHEP08(2020)040.

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