The subsolar mass primordial black hole (PBH) attracts attention as robust
evidence of its primordial origin against the astrophysical black hole. Not
only with themselves, PBHs can also form binaries with ordinary astrophysical
objects, catching them by gravitational wave (GW) bremsstrahlung. We discuss
the detectability of the inspiral GWs from binaries consisting of a PBH and a
white dwarf (WD) by using space-borne gravitational wave interferometers like
DECIGO. The conservative assessment shows the expected event number in three
years by DECIGO is $mathcal{O}(10^{-6})$ for $M_mathrm{PBH} sim 0.1M_odot$.
Possible enhancement mechanisms of WD-PBH binary formation may amplify this
event rate. We discuss how large enhancement associated with WDs is required to
detect WD-PBH merger events without violating the existing constraints on the
PBH-PBH merger by the ground-based detector.

The text discusses the potential detectability of gravitational waves (GWs) from binary systems consisting of a primordial black hole (PBH) and a white dwarf (WD) using space-borne gravitational wave interferometers like DECIGO. The conservative assessment suggests that the expected event number in three years by DECIGO is on the order of 10^-6 for PBH masses around 0.1 times the mass of the Sun.

However, the event rate could potentially be amplified through enhancement mechanisms of WD-PBH binary formation. The article highlights the need to discuss how large enhancements associated with WDs are required to detect WD-PBH merger events without violating existing constraints on PBH-PBH mergers by ground-based detectors.

Future Roadmap and Potential Challenges:

  1. Further research and analysis are needed to understand the exact mechanisms and conditions for enhancing WD-PBH binary formation. This will involve studying the dynamics and interactions between WDs and PBHs.
  2. Development and deployment of space-borne gravitational wave interferometers like DECIGO will be crucial for detecting GW signals from WD-PBH mergers. The success of these missions depends on technological advancements and funding.
  3. There may be challenges in distinguishing GW signals from WD-PBH mergers from other astrophysical sources or noise. Signal processing techniques and data analysis methods need to be optimized to improve detection sensitivity and accuracy.
  4. The existing constraints on PBH-PBH mergers by ground-based detectors need to be considered and incorporated into the analysis. Balancing the search for WD-PBH mergers while complying with the limits set by PBH-PBH mergers poses a challenge.
  5. Theoretical modeling and simulations can help determine the expected event rate of WD-PBH mergers and compare it with observational data. This will further refine our understanding of primordial black holes and their interactions with white dwarfs.

Opportunities on the Horizon:

  • The detection of GW signals from WD-PBH mergers would provide robust evidence for the existence of primordial black holes and their interactions with ordinary astrophysical objects.
  • Understanding the formation and dynamics of WD-PBH binaries can shed light on the early universe and the processes that gave rise to primordial black holes.
  • The enhanced event rate of WD-PBH mergers due to WD-related mechanisms can potentially allow for more frequent detections and a better understanding of these binary systems.
  • The success of space-borne gravitational wave interferometers like DECIGO would open up possibilities for studying a wide range of astrophysical phenomena and potentially discover new classes of objects or events.
  • Improved signal processing techniques and data analysis methods developed for the detection of WD-PBH mergers could also benefit other areas of gravitational wave astronomy, enhancing our ability to detect and study various astrophysical sources.

In conclusion, the detection of GWs from WD-PBH mergers is an exciting area of research that has the potential to provide valuable insights into the nature and origin of primordial black holes. While there are challenges to overcome, such as understanding the enhancement mechanisms and meeting the constraints set by ground-based detectors, there are significant opportunities for advancements in our understanding of the early universe and gravitational wave astronomy.

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Introduction to Quantum Cosmology

Quantum Cosmology stands as the forefront of unraveling the profound secrets of our universe. Merging the principles of Quantum Mechanics and General Relativity, this advanced field seeks to explain the cosmos’s very early stages, focusing on the Planck era where classical theories of gravity no longer suffice. We delve deep into the realms of spacetime, singularity, and the initial conditions of the universe, exploring how Quantum Cosmology reshapes our understanding of the cosmos’s birth and evolution.

The Birth of the Universe: The Big Bang and Beyond

At the heart of Quantum Cosmology is the intriguing narrative of the universe’s inception, commonly referred to as the Big Bang. Traditional models depict a singular point of infinite density and temperature. However, Quantum Cosmology introduces a more nuanced picture, suggesting a quantum bounce or other quantum phenomena that avoid the singularity, offering a revolutionary perspective on the universe’s earliest moments.

Unraveling the Planck Era

The Planck era represents the universe’s first






seconds, a time when the classical laws of physics cease to operate. Quantum Cosmology strides into this enigmatic epoch, employing quantum gravity theories like Loop Quantum Gravity or String Theory. These theories aim to provide a coherent description of spacetime’s fabric at this fundamentally small scale, potentially uncovering new insights about the universe’s structure and behavior.

The Role of Quantum Fluctuations

In the primordial universe, quantum fluctuations are believed to play a pivotal role. These minute variations in energy density, amplified by cosmic inflation, are thought to lead to the large-scale structures we observe today, such as galaxies and clusters. Quantum Cosmology seeks to quantitatively understand these fluctuations, deciphering their implications for the universe’s overall architecture and destiny.

Navigating through Cosmic Singularities

One of the most tantalizing challenges in contemporary physics is understanding cosmic singularities—points where the laws of physics as we know them break down. Quantum Cosmology proposes various scenarios to address these enigmas, suggesting that quantum effects may smooth out singularities or even connect our universe to others through cosmic gateways known as wormholes.

The Quantum Landscape of the Universe

The concept of a quantum landscape has emerged, depicting a vast, complex space of possible universes each with their own laws of physics. This landscape offers a staggering vision of a multiverse, where our universe is but one bubble in a frothy sea of countless others. Quantum Cosmology explores these ideas, examining their implications for fundamental physics and our place in the cosmos.

Advanced Theories and Models

To tackle these profound questions, Quantum Cosmology utilizes several advanced theories and models. Loop Quantum Cosmology offers insights into the very early universe, suggesting a bounce instead of a big bang. String Theory proposes a universe composed of tiny, vibrating strings, potentially in higher dimensions. These and other models are at the cutting edge, each contributing valuable perspectives to our understanding of the cosmos.

Empirical Evidence and Observational Challenges

While Quantum Cosmology is a field rich with theoretical insights, it faces the significant challenge of empirical verification. As researchers devise ingenious methods to test these theories, from observations of the cosmic microwave background to the detection of gravitational waves, the field stands at a thrilling juncture where theory may soon meet observation.

Future Directions and Implications

As we advance, Quantum Cosmology continues to push the boundaries of knowledge, hinting at a universe far stranger and more wonderful than we could have imagined. Its implications stretch beyond cosmology, potentially offering new insights into quantum computing, energy, and technology. As we stand on this precipice, the future of Quantum Cosmology promises not just deeper understanding of the cosmos, but also revolutionary advancements in technology and philosophy.

Conclusion: A Journey through Quantum Cosmology

Quantum Cosmology is more than a field of study; it’s a journey through the deepest mysteries of existence. From the universe’s fiery birth to the intricate dance of quantum particles, it offers a compelling narrative of the cosmos’s grandeur and complexity. As we continue to explore this fascinating frontier, we not only uncover the universe’s secrets but also reflect on the profound questions of our own origins and destiny.

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