Scientific Objectives of Einstein Telescope (1206.0331v1)

Abstract: The advanced interferometer network will herald a new era in observational astronomy. There is a very strong science case to go beyond the advanced detector network and build detectors that operate in a frequency range from 1 Hz-10 kHz, with sensitivity a factor ten better in amplitude. Such detectors will be able to probe a range of topics in nuclear physics, astronomy, cosmology and fundamental physics, providing insights into many unsolved problems in these areas.

• The paper demonstrates how the Einstein Telescope will boost gravitational wave detection by achieving an order of magnitude improvement in sensitivity over current detectors.
• The paper evaluates ET's ability to explore key astrophysical phenomena, including binary mergers and neutron star interiors, through its extended frequency coverage.
• The paper examines the ET design's potential to test general relativity and cosmological models by detecting millions of events and constraining fundamental physics.

Overview of "Scientific Objectives of Einstein Telescope"

The paper entitled "Scientific Objectives of Einstein Telescope" provides a comprehensive analysis of the anticipated capabilities and scientific goals associated with the third-generation Einstein Gravitational-Wave Telescope (ET). The ET is proposed to surpass the current advanced gravitational wave (GW) detectors in terms of sensitivity and frequency range, particularly aiming at frequencies from 1 Hz to 10 kHz. This increased sensitivity by an order of magnitude over existing detectors is designed to enable a wide range of studies in nuclear physics, astrophysics, cosmology, and fundamental physics.

Motivation for ET

The primary rationale for the ET, as articulated in the paper, is its ability to probe new astrophysical phenomena and answer outstanding scientific questions about the universe. By operating with a significantly enhanced sensitivity and at a lower frequency range than current detectors like LIGO and Virgo, the ET can explore a broader spectrum of sources, including intermediate-mass black holes (IMBHs), extreme mass-ratio inspirals, and the late stages of binary neutron star inspirals.

Sensitivity and Frequency Range

ET's proposed frequency range will render it sensitive to an expanded mass range for compact objects, from stellar remnants to IMBHs. This sensitivity is expected to exceed $\sim 10^{-25}\,\rm Hz^{-1/2}$ over 20-200 Hz, making it possible to detect sources across vast cosmological distances. The design's ability to detect lower-frequency signals is key for observing the dynamics of massive black hole mergers and other phenomena that emit gravitational radiation primarily in the lower-frequency band.

Scientific Capabilities

The Einstein Telescope is expected to explore several critical scientific domains:

1. Gravitational Astrophysics: ET will enable the observation of GW signals from a variety of sources, including binary black holes (BBH), binary neutron stars (BNS), and neutron star-black hole (NS-BH) binaries, thus providing rich data for understanding their evolution and population throughout the universe.
2. Cosmology: As a standard siren, compact binary GWs carry intrinsic luminosity measurements, which can be utilized to measure cosmological parameters with high precision. ET's improved distance reach affords the potential to probe deeper into cosmic history and investigate the properties of dark energy.
3. Nuclear Physics: ET’s capability to observe high-SNR events will facilitate studies of neutron star (NS) interiors and their equation of state, providing insights into nuclear matter at extreme densities.
4. Testing General Relativity (GR): The observation of GW from different phases of compact binary coalescence will allow stringent tests of GR in the highly curved spacetime around black holes, thus enabling the constraints on alternative theories of gravity.

Expected Detection Rates

With its enhanced sensitivity, ET is poised to detect numerous GW events, potentially observing millions of compact binary mergers per year, thus vastly outstripping current observational capabilities. These observations will enhance our understanding of the merger rates of different astrophysical sources and potentially confirm or refute various formation models.

System Design and Challenges

ET’s design includes a triangular topology, employing three interferometers with 10 km arm lengths, which together will form a nearly isotropic detector array capable of resolving wave polarizations and significantly reducing blind spots. Addressing the challenge of overlapping GW signals in data is paramount, and continued developments in data analysis pipelines will be crucial for maximizing ET's scientific output.

Implications and Future Developments

The realization of the ET will mark a significant advancement in GW observation, establishing a new observational era with implications spanning fundamental physics and observational astronomy. As the project progresses, its impact is anticipated to resonate widely across multiple scientific fields, contributing pivotal insights into the fundamental workings of the universe. The ongoing collaborative development and data simulation efforts will be vital in laying the foundation for ET’s operational success and scientific achievements.