Quantum Vortex Mystery: Unveiling the Twisted Roots of Neutron Stars' Puzzling Pulses

A recent study published in the journal Scientific Reports has provided insights into the mysterious “heartbeats” observed in neutron stars. These periodic pulses, first discovered in 1967, were initially thought to be signals from extraterrestrial life, but are now known to originate from radiation beams of dead stars. However, their precision is occasionally disrupted by glitches, or sudden speed-ups in the neutron stars’ spins.

The research team, led by Muneto Nitta from Hiroshima University’s International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), proposed a new model to explain these glitches. The model is based on the dynamics of superfluid vortices and quantum vortex networks. The researchers found that their proposed model aligns with the power-law distribution of glitch energies observed in neutron stars without requiring extra tuning, unlike previous models.

The model suggests that the superfluid core of a neutron star spins at a constant pace, while its ordinary component slows its rotation by releasing gravitational waves and electromagnetic pulses. Over time, the speed discrepancy grows, causing the star to expel superfluid vortices to regain balance. However, as superfluid vortices are entangled, they drag others with them, causing glitches.

The researchers propose the existence of two types of superfluids in neutron stars: s-wave superfluidity, which dominates the outer core’s relatively tamer environment, and p-wave superfluidity, which prevails in the inner core’s extreme conditions. Each integer-quantized vortex (IQV) in the s-wave outer core splits into two half-quantized vortices (HQVs) upon entering the p-wave inner core, forming a cactus-like superfluid structure known as a boojum. As more HQVs split from IQVs and connect through boojums, the dynamics of vortex clusters become increasingly complex.

The researchers ran simulations and found that the exponent for the power-law behavior of glitch energies in their model closely matched the observed data, indicating that their proposed framework accurately reflects real-world neutron star glitches. The team believes that their argument, while simple, is powerful and provides a deep connection between the interior structure of neutron stars and observational data.

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