The Universe seen through gravitational waves

1. The Universe seen through gravitational waves Stuart Reid Royal Society of Edinburgh, 20 May 2008

2. Research aim • Aim • To observe Gravitational Waves from astrophysical systems using laser interferometric techniques on Earth • GEO 600 (UK/Germany) • LIGO (USA) • Virgo (Italy/France) • Future planned detectors (e.g. Einstein Telescope) • Why? • To open up a new andoriginal branch of Astronomy

3. Prediction of gravitational waves Newton Einstein gravity a force gravity a geometry  prediction of gravitational waves

4. “Gravitational Waves” • Gravitational waves ‘Ripples in the curvature of spacetime’ that carry information about changing gravitational fields - or - ‘fluctuating strains in space of amplitude h’ where: • Produced by violent acceleration of mass in: • Neutron star binary coalescences • Black hole formation and interactions • Cosmic string vibrations in the early Universe (?) • and less violent events: • Pulsars • Binary stars • However, for these sources we expect tiny strains of 10-22. binary stars coalescing

5. Indirect detection of gravitational waves Joseph Taylor & Russell Hulse Binary Pulsar PSR 1913+16

6. Detection of Gravitational Waves • Consider the effect of a wave on a ring of particles: one cycle Michelson interferometer • Gravitational waves have very weak effect: - want baseline of interferometers as long as possible - expect movements of less than 10-18 m over 4 km

7. GW detector network

8. Advanced LIGO Principal limits to detector sensitivity • I am involved in developments for the future upgrades to the LIGO, Advanced LIGO (funded by US, UK and Germany) and in the development of a future detector in Europe (Einstein Telescope). Thermal noise already limits detector sensitivity in the most sensitive frequency band and will set the low-frequency limit if quantum noise is further reduced

9. Thermal noise in test masses and suspensions Detection band thermal displacement frequency pendulum mode internal mode

10. Research - reduction of TN in test masses and suspensions • Surface preparation and properties of silica • Quantification and reduction of the effects of dissipation • Hydroxide-catalysis bonding of silica surfaces for improved suspension thermal noise performance Advanced LIGOsuspension (quasi-monolithic silica lower stage)

11. Research - reduction of TN in test masses and suspensions • Thermo-mechanical properties of silica • Precise balancing of the tension in suspensions elements against the effects of material thermo-mechanical properties • Charging effects in precision measurements • Modification of silica surfaces to ameliorate charge build-up • Charging may lead to electrostatic dissipation (thermal noise) and control issues that could limit the anticipated enhancements from the 2nd generation of instruments.

12. Research - reduction of TN in test masses and suspensions • Novel material properties at low temperature • Apply silica surface knowledge base to develop ultra-low dissipation silicon suspension technology • Study thermo-mechanical properties of silicon at low temperature (dependence on doping etc).

13. 10-19 10-20 10-21 10-22 10-23 10-24 10-25 LIGO 2005 Virgo 2008 GEO-HF 2011 Ad LIGO/Virgo NB Advanced LIGO/Virgo (2014) Credit: M.Punturo Einstein Telescope 1 10 102 103 104 Frequency (Hz) Detector sensitivities

14. Benefits to Scotland – knowledge exchange, public outreach • Placing Scotland at the forefront of international collaboration • Exchange of personnel internationally • Training of research students • Spin-off technology • e.g. Spanoptic, Selex Galilean, Astrium, TNO • Schools and public outreach • Key subject for engaging audiences in the excitement of science • RS Summer Exhibition, RSE Masterclasses, school visits RSE Masterclass November 2005

15. Gravitational Wave Astronomy • GW detector systems now reaching levels where they may see signals within the next few years. • Fundamental physics • Astrophysics • Cosmology • New sources and science A new way to observe the Universe