Chords as the reverberation of cosmic drama

In recent years, scientists from the Institute of Physics in Opava have focused on the properties of gravitational wave reverberations. These waves are emitted from the vicinity of massive black holes or during the merger of compact cosmic objects like neutron stars. It turns out that these reverberations also include higher harmonic waves, which can be compared to the chords of musical instruments being played. "These higher harmonic waves, i.e. something like cosmic chords, always have slightly different properties compared to the fundamental waves of gravitational wave reverberations. And it is the research of these differences that can reveal the properties of the objects from which the gravitational waves originated," explains Prof. Zdeněk Stuchlík, director of the Institute of Physics in Opava.

A black hole as a musical instrument

Gravitational waves are emitted both from colliding massive cosmic objects and from black holes themselves, and this is where the scientists have focused their research. "Imagine a black hole as a grand cosmic instrument, with its gravitational wave reverberations forming the notes of a symphony," explains Dr. Roman Konoplya from the Institute of Physics in Opava, the lead author of this study. "These vibrations, known as quasi-normal modes, can be likened to the musical background that enriches the main note of a violin or piano. Traditionally, scientists have concentrated on the 'keynote' that remains relatively constant. However, the 'tones' in the background have proven to be far more intriguing," adds Konoplya.

Chords reveal the unseen

Recent research by physicists in Opava has revealed that the properties of these "cosmic chords" are highly sensitive to minor fluctuations near a black hole's event horizon. These subtle undertones could offer new insights into the geometry of black holes, which were previously thought to be indistinguishable from other cosmic phenomena, such as the hypothetical "space-time shortcuts" known as wormholes. "Our advanced models show that while the fundamental overtone remains stable, higher overtones can vary significantly with small changes near the event horizon. This discovery can be compared to the discovery that the sound of every musical instrument contains subtle undertones that reveal its specific characteristics or imperfections. Investigating these cosmic chords is crucial for probing the near-horizon geometry of black holes and may lead to important revisions in our understanding of gravity, potentially refining Einstein's classical theory," explains Dr. Konoplya regarding the implications of this research.

The future in the domain of the LISA observatory

Current gravitational wave detectors such as LIGO or Virgo are currently able to detect primarily the fundamental tone of quasi-normal modes. Future instruments, such as the planned Laser Interferometer Space Antenna (LISA) developed by NASA and ESA, are expected to significantly improve our ability to measure these faint "cosmic chords." This advancement will provide scientists with a much clearer view of the previously unobservable edges of black holes. "These overtones near the event horizon will enable scientists to differentiate between phenomena affecting the matter surrounding the black hole—such as those from a collapsing star—and the properties intrinsic to the black hole itself. Until now, scientists could only infer the characteristics of black holes through their interactions with surrounding matter. However, these cosmic chords will be crucial in directly studying the fundamental attributes of the black hole itself," explains Roman Konoplya, reflecting on the research findings.

Essentially, scientists hope that by carefully "listening" to the symphony of quasi-normal modes, they will uncover new secrets about the very structure of space and time around black holes. This progress could bring us one step closer to unraveling the mysteries of these still enigmatic cosmic objects and the fundamental laws that govern them.

An award by the Grant Agency of the Czech Republic

Roman Konoplya, a Ukrainian physicist who has long been affiliated with the Institute of Physics in Opava, received the prestigious Award of the President of the Grant Agency of the Czech Republic (GAČR) in 2023 for his significant scientific contributions. "Receiving this award means a great deal to me. It underscores the importance of our work and affirms that our team in Opava is dedicated and diligent in our research on gravitational physics and black hole phenomena," Konoplya reflects. He notes that this recognition highlights their innovative approach to understanding space-time around black holes, extending beyond Einstein's theories to explore various gravitational frameworks. "It is truly gratifying to see our efforts acknowledged as among the best in natural sciences in the Czech Republic. This recognition fuels our commitment to advancing our research and its potential impact on future scientific understanding for all of humanity," Konoplya concludes.

Contact details:

Roman Konoplya, Ph. D.

prof. RNDr. Zdeněk Stuchlík, CSc.

Mgr. Petr Horálek

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