arXiv subjects

Tomislav Andric

Publications and source records attributed to Tomislav Andric.

4 recordsLinked to original sources

arXiv2026

Correlation-based Modeling of Seismic Newtonian Noise in Half-Space and Full-Space Media

Seismic Newtonian noise, arising from fluctuating gravitational forces on detector test masses due to ambient seismic activity, represents a fundamental sensitivity limit for low-frequency gravitational-wave observatories such as the Einstein Telescope. Effective mitigation of Newtonian noise requires detailed knowledge of the statistical correlations between the Newtonian acceleration perturbation at the test mass and the seismic displacement field measured by surrounding sensor arrays. In this work, the gravitoelastic correlation tensors (the cross-correlations between the Newtonian acceleration perturbation and the seismic displacement field) are derived and numerically validated for Rayleigh waves and body waves in half-space and full-space media, considering test masses located above and below ground, with and without a spherical cavity. The analytical solutions provide exact and asymptotic benchmarks for validating a Cartesian numerical integration framework, which reproduces the corresponding gravitoelastic tensors across Rayleigh-wave and body-wave models, establishing a unified tool for Newtonian-noise modeling and sensor-array design in future gravitational-wave detectors.

gr-qc↗

arXiv2025

Improving cosmological reach of a gravitational wave observatory using Deep Loop Shaping

Improved low-frequency sensitivity of gravitational wave observatories would unlock study of intermediate-mass black hole mergers, binary black hole eccentricity, and provide early warnings for multi-messenger observations of binary neutron star mergers. Today's mirror stabilization control injects harmful noise, constituting a major obstacle to sensitivity improvements. We eliminated this noise through Deep Loop Shaping, a reinforcement learning method using frequency domain rewards. We proved our methodology on the LIGO Livingston Observatory (LLO). Our controller reduced control noise in the 10--30Hz band by over 30x, and up to 100x in sub-bands surpassing the design goal motivated by the quantum limit. These results highlight the potential of Deep Loop Shaping to improve current and future GW observatories, and more broadly instrumentation and control systems.

astro-ph.IM↗

arXiv2025

GEMINI: The First Underground Testbed for Seismic Isolation and Interplatform Control in Next-Generation Gravitational-Wave Detectors

GEMINI is an underground research and development facility dedicated to advancing seismic isolation and control technologies for future gravitational-wave observatories, including the Einstein Telescope (ET) and the Lunar Gravitational-Wave Antenna (LGWA). This paper presents the technical design and theoretical framework of GEMINI's active seismic isolation platforms, including detailed noise budget analyses, performance predictions, and residual platform motion evaluations. The GEMINI platforms are designed to achieve unprecedented vibration isolation, targeting motion suppression across the 10 mHz to 10 Hz frequency band, and with the goal to make them the quietest platforms of their kind. In the context of ET, GEMINI will enable the development and validation of inter-platform control strategies essential for the stabilization of auxiliary degrees of freedom of its interferometers. GEMINI will also support the testing of cryogenic payloads and ultra-sensitive inertial sensors required for LGWA. By integrating advanced cryogenic systems, precision inertial sensors, and state-of-the-art vibration isolation technologies, GEMINI will serve as a versatile testbed for next-generation ground-based gravitational-wave detectors and lunar seismometry missions.

physics.ins-det↗

arXiv2023

Characterization and evasion of backscattered light in the squeezed-light enhanced gravitational wave interferometer GEO 600

Squeezed light is injected into the dark port of gravitational wave interferometers, in order to reduce the quantum noise. A fraction of the interferometer output light can reach the OPO due to sub-optimal isolation of the squeezing injection path. This backscattered light interacts with squeezed light generation process, introducing additional measurement noise. We present a theoretical description of the noise coupling mechanism. We propose a control scheme to achieve a de-amplification of the backscattered light inside the OPO with a consequent reduction of the noise caused by it. The scheme was implemented at the GEO 600 detector and has proven to be crucial in maintaining a good level of quantum noise reduction of the interferometer for high parametric gain of the OPO. In particular, the mitigation of the backscattered light noise helped in reaching 6dB of quantum noise reduction [Phys. Rev. Lett. 126, 041102 (2021)]. The impact of backscattered-light-induced noise on the squeezing performance is phenomenologically equivalent to increased phase noise of the squeezing angle control. The results discussed in this paper provide a way for a more accurate estimation of the residual phase noise of the squeezed light field.

physics.optics↗