The dawn of gravitational-wave astronomy
Professor Bangalore Sathyaprakash, Penn State, USA and Cardiff University, UK
Gravitational waves from merging black hole binaries are the most powerful events ever witnessed. LIGO's observations of binary black holes have already begun to impact astrophysical models of the formation and evolution of compact binaries and have facilitated tests of general relativity in a regime where the theory had not been tested before. In addition to binary black holes we also expect to observe binaries in which one or both the companions is a neutron star and the other is possibly a black hole. Observing the full spectrum of binaries will help us understand the origin of short gamma-ray bursts, measure the equation-of-state of dense nuclear matter, test the no-hair theorem for black holes and map the cosmic history of the formation and growth of light black hole seeds. Gravitational wave observations could also reveal processes that operate in core collapse supernovae and the mechanism of core bounce and formation of neutron stars and black holes.
Low-frequency gravitational wave astronomy from space
Professor Karsten Danzmann, Albert Einstein Institute Hannover, Germany
ESA has selected The Gravitational Universe as the Science Theme for the L3 large mission flight opportunity with a foreseen launch in 2034. The LISA Consortium has proposed the LISA mission concept for this Science Theme and recently the Science Programme Committee (SPC) of ESA has selected LISA as the L3 mission. LISA will comprise 3 spacecraft at the corners of an equilateral triangle with 2.5 million km arms in a heliocentric orbit trailing the earth. It will form a laser interferometer with 3 arms and 6 laser links, observing low-frequency gravitational waves with frequencies from less than 0.1 mHz up to more than 0.1 Hz. The LISA Pathfinder mission has concluded science operations on July 18th, 2017. It has demonstrated an acceleration noise performance more than a factor of three better than required for the full LISA mission, paving the way for a timely start of LISA.
Gravitational wave detection using laser interferometry beyond the standard quantum limit
Professor Michele Heurs, Leibniz Universität Hannover, Germany
Interferometric gravitational wave detectors (such as Advanced LIGO) employ high power solid-state lasers to maximise their detection sensitivity and hence their “reach” into the universe. These sophisticated light sources are ultra-stabilised with regard to output power, emission frequency, and beam geometry; this is crucial to obtain low detector noise. However, even when all laser noise is reduced as far as technically possible, unavoidable quantum noise of the laser still remains. This is a consequence of the Heisenberg Uncertainty Principle, the basis of quantum mechanics: In this case, it is fundamentally impossible to simultaneously reduce both the phase noise and the amplitude noise of a laser to arbitrarily low levels. This fact manifests in the detector noise budget as two distinct noise sources – photon shot noise and quantum radiation pressure noise – which together form a lower boundary for current-day gravitational wave detector sensitivities, the standard quantum limit of interferometry. In order to overcome this limit, various techniques are being proposed, among them different uses of non-classical light, and alternative interferometer topologies. MH will explain how quantum noise enters and manifests in an interferometric gravitational wave detector, and will give an overview of proposed schemes to overcome this seemingly fundamental limitation, all aimed at the goal of higher gravitational wave event detection rates.
Use of nanovibrational stimulation ("nanokicking") to control cell behaviour and stem cell differentiation
Professor Stuart Reid, Strathclyde University, United Kingdom
The ability to control cell behaviour and cell fate remains a significant challenge within various fields of medical research, such as for manufacturing engineered tissues and for drug discovery. The use of mechanotransduction (how cells convert mechanical forces to biochemical cues) could provide an alternative route for providing high quality controlled/specialised cells without the requirement for chemical induction factors or complex cell scaffolds. Measurement and analytical techniques developed within the field of gravitational wave astronomy have recently been used to develop a novel technique for cell stimulation based on nanoscale vibration, referred to as "nanokicking". The technique has been demonstrated to differentiate a potential autologous cell source, mesenchymal stem cells (MSCs), into mineralized tissue in 3D. This could provide a new route for providing autologous bone grafts, which are currently in short supply, and are currently associated with pain and donor-site morbidity. In addition, other cell responses include the promotion of cell fusion in placental cell lines, in addition to modifying biofilm deposition from bacteria (P. aeruginosa), suggesting that the response to nanoscale vibration is applicable to a wider range of cell types in addition to potentially being established early in evolutionary history. The development of the current hardware for supplying nanoscale vibrations to cell cultures, and an overview of cell responses, is discussed.
MEMS gravimeters as a new tool for gravity imaging
Professor Giles Hammond, Glasgow University, United Kingdom
The Institute for Gravitational Research at the University of Glasgow has led the development of the fused silica suspensions used to support the 40kg mirrors of the aLIGO detectors. These suspension systems required the development of ultralow mechanical loss glass structures and corresponding bespoke modelling techniques to provide the required analysis tools.
Over the past 4 years, Prof. Hammond has grown an applied research group in collaboration with the School of Engineering, focussing on precision MicroElectroMechanicalSensors (MEMS) for gravity imaging applications. The group has developed the first MEMS based gravity sensor with sufficient sensitivity and stability to detect the earth tides; elastic deformations in the solid earth caused by the tidal potential of the moon and sun. The unique combination of expertise on low noise opto-mechanical systems, combined with the fabrication expertise of the James Watt Nanofabrication Centre, has enabled the development of this new research theme, currently funded under the QuantIC hub, one of the 4 UK quantum technology hubs.
In this talk I will describe the translation of fundamental research from the field of gravitational wave detection into applied gravity sensing. I will detail the design of the MEMS gravimeter system including the novel low frequency flexure architecture and the construction of a high sensitivity, long term stable, optical shadow sensor. I will further provide an overview of the current activities being undertaken by the research team. These include the development of a field portable system that can operate outside of the laboratory, capable of measuring vertical gravity changes within the Physics building in Glasgow. I will also detail some of the ongoing industrial research projects to further improve the device and allow for new sensing methodologies in precision MEMS gravimeters. This includes the development of an on-chip silicon interferometer with Schlumberger, the development of MEMS gradiometer systems with Clydespace, and modelling of gravitational signatures with QinetiQ. Finally I will provide an outlook of the direction of the research group, the current efforts to commercialise this technology.