Title: Theoretical Study Reveals Extremal Kerr Black Holes as Potential Amplifiers of New Physics
Subtitle: Researchers from UC Santa Barbara, University of Warsaw, and University of Cambridge explore the unique properties of extremal Kerr black holes
Date: September 22, 2023
Byline: Science X Network
Black holes have long fascinated scientists with their immensely strong gravitational pull that prevents anything, including matter and electromagnetic waves, from escaping. Now, a team of researchers from the University of California–Santa Barbara, University of Warsaw, and University of Cambridge has conducted a theoretical study shedding light on extremal Kerr black holes and their potential to amplify new, unknown physics.
The study, published in Physical Review Letters, highlights the discovery that extremal black holes exhibit distinct characteristics that make them ideal amplifiers of new physics. According to Maciej Kolanowski, one of the researchers involved in the study, this research builds on a previous project focused on extremal black holes and their properties.
The team’s previous paper revealed that extremal black holes, when affected by a cosmological constant, experience infinite tidal forces. This suggests that if living beings were to approach these black holes, they would be crushed by gravity before even nearing the black hole’s center. However, the researchers found that if the cosmological constant is zero, as commonly assumed in many astrophysical scenarios, this effect vanishes.
The current study emerged from a discussion during UC Santa Barbara’s Gravity Lunch, where the idea of EFT (effective field theories) and quantum corrections to the Einstein equations giving rise to singularities on black hole horizons was explored. Grant Remmen, who had previously worked on EFTs, collaborated with Gary Horowitz, Maciej Kolanowski, and Jorge Santos to test this idea with a series of calculations.
The calculations focused on extremal black holes that rotate at the maximum possible rate, with horizons moving at the speed of light. It was discovered that the higher-derivative EFT corrections caused the horizons of these black holes to become singular, resulting in infinite tidal forces. This is in contrast to regular black holes, where tidal forces only become infinite at the center.
Surprisingly, the researchers found that the singularity extends from the center of the black hole to its horizon—a phenomenon deemed unexpected. The researchers note that these higher-derivative terms in the EFT equations are sensitive to new physics, with their coefficients influenced by the presence of particles at high energies and short distances.
Moreover, the strength of the tidal divergence and the occurrence of tidal singularities in extremal black holes were found to depend heavily on the EFT coefficients. The results indicate that the spacetime geometry near the horizon of these black holes is sensitive to new physics at higher energies, even using the EFT coefficients generated by the Standard Model of particle physics.
The study’s implications are significant, as they challenge the assumptions made about extremal Kerr black holes. While it was not expected that the horizons of these black holes would have infinitely large curvatures, the researchers’ findings suggest that they do.
In future work, the researchers aim to explore ways of resolving these singularities through ultraviolet physics. They also plan to investigate other scenarios where short-distance effects might unexpectedly manifest at larger distances.
This study opens up new avenues for understanding the intricacies of black holes and their potential for uncovering new physics. By exploring extremal Kerr black holes, researchers are one step closer to unraveling the mysteries of these cosmic phenomena and their role in our understanding of the universe.
Reference:
Gary T. Horowitz et al, “Extremal Kerr Black Holes as Amplifiers of New Physics,” Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.131.091402