PhD Projects with Gravitational Wave Group

School of Physics, University of Western Australia

Gravitational waves are ripples of space and time created by violent events in the Universe such as mergers of two black holes or core-collapse of massive stars at supernovae. Their existence was first predicted by Einstein's general theory of relativity. Gravitational waves will represent a completely new spectrum in astronomy and its detection will revolutionize our understanding of how space and time behave in violent events. The ultimate direct detections of gravitational waves are confidently expected in the coming decade, as the advanced gravitational wave detectors start to operate.

The advanced gravitational wave detectors are giant interferometers looking for those tiny ripples in spacetime induced by astronomical events. There are worldwide efforts to create the gravitational wave detector network and develop cutting edge techniques for improving the sensitivities of the advanced gravitational wave detectors. Figure 2 shows the gravitational wave detector network including the 3 existing km scale detectors LIGO (4km US), and Virgo (3km, an Italy-Franc collaboration, located near Pisa, Italy), the 3 km detector under construction KAGRA (Japan), the 600m detector GEO600 (a German-UK collaboration, located at Hanover, Germany), as well as the Australian 80m test facility.

Australia plays an active role in developing technologies for the advanced gravitational wave detectors. The University of Western Australia group is part of the Australian Consortium of Interferometric Gravitational wave Astronomy (ACIGA), and operates ACIGA High Optical Power facility. We work on developing techniques to further improve the sensitivity of the advanced detectors below the standard quantum limit (SQL), which is currently the limiting sensitivity. The development of advanced techniques to improve the sensitivity of gravitational wave detectors leads to exciting new physics phenomena and techniques that may have application beyond gravitational wave detectors. Our project covers a range of projects from gravitational wave data analysis, and optical cavity experiment in both large and small scale.

Experimental Projects

1. Using Light to Control Parametric Instability High optical power gravitational wave detectors are likely to suffer parametric instability due to the resonant interaction between the cavity optical modes and the high Q acoustic modes of the test mass mirrors. This instability can be suppressed by feeding back optical signals into the cavities. This project will investigate this idea of optical feedback control in a small scale experiment. The research result will be in conjunction with experiments at the Gingin High Optical Power Facility.

Parametric instability in a free optical cavity was first observed in a small scale table top experiment in UWA lab. Then we observed the parametric instability in our 80m suspended

LI GO (Hanford, US)4km

LI GO (Livingston,US) 4km

VIRGO (near Pisa) 3km

GEO600, Germany/UK

KAGRA- J apan

LIGO-India(Proposed)

ACIGA 80m

Figure 2. Global network of gravitational wave detectors

cavity. Shortly afterward, LIGO also observed parametric instability in the 4km interferometer detector, with only 20% of the design optical power. It is of importance we find effective control strategies to suppress and control the stability. One of them is to setup an optical system to destructively interfere with the field inside the cavity to suppress the instability. This will be achieved by reflect the cavity transmitted beam back into the cavity after frequency shifting and phase masking. The reflected beam needs to be phase locked to the cavity transmission to maintain correct phase to destructively interfere with the beam inside cavity generated by the parametric process. The other is to use CO2 laser to modulate the cavity parameters to suppress the parametric gain.

2. Optical springs: towards measurements below the standard quantum limitOptical springs are created by radiation pressure forces in optical cavities. This effect could be used to modify the dynamics of the resonator/mirror in the optical cavity and thus creating an opto-mechanical system with very low loss that could be used in a range of schemes for beating the standard quantum limit for gravitational wave detectors.

This project will be focused on developing low loss cavities with novel resonator design, and test optical spring effect. We are collaborating with researchers in Austria, Taiwan, Holland and France to fabricate the “thermal noise free” resonators. An optomechanical system as shown in Figure 3 has been designed. The project involves modelling the resonator using finite element analysis, constructing and tuning optical cavities to observe optical spring dilution to achieve very low loss resonators. This scheme has the potential of measuring macroscopic objects with resolution better than the “standard quantum limit” predicted by naïve application of quantum mechanics. This offers a new technique for improving gravitational wave detectors as well as allowing a range of new experiments in quantum experiments.

Pictures of UWA optical laboratory table top opto-mechanics experiments and the 80m high optical power facility

Figure 3. An optical cavity with a “cat-flap” resonator mirror design (the purple part is the coated mirror)

Detecting Gravitational Wave Events - Data Analysis

The research group led by Prof. Linqing Wen aims at solving the most critical issues that the entire gravitational wave community is facing, that is, how to best detect a gravitational-wave event and identify its electromagnetic counterpart in a timely manner. The approach is to participate directly in the on-going international frontier research in the gravitational-wave data analysis to (1) discover and (2) localize in real-time, possibly the first gravitational-wave sources, (3) search for their electromagnetic (EM) counterparts using both radio and optical telescopes, and (4) use theory of gravitation and data from electromagnetic observations to probe the astrophysics of GW sources. Students with proficiency in programming languages C and MATLAB are a plus.

The titles of the specific projects are:

1. Real-time low-latency searches of gravitational waves from coalescing binaries of neutron stars and black holes.

2. Application of graphics processing units (GPUs) to speed up searches of gravitational waves

3. Probe of the parameter space of the gravitational-wave/X-ray source 4U 1820-30 using physics of 3-body dynamics, gravitation theory, and data from electromagnetic observations

Probing the Transient Universe with a Robotic Telescope

This research group is led by David Coward (david.coward@uwa.edu.au) and Ron Burman (ron.burman@uwa.edu.au).

The 21st century has heralded a new era in probing the Universe: for the first time mankind is able to observe the Universe across all parts of the electromagnetic spectrum and beyond. Space based gamma ray burst detectors have opened a window into a Universe teeming with short-lived exotic phenomena, the so-called “transient Universe”.

The following projects will employ a new robotic telescope, the UWA Zadko Telescope, to perform the following transient sky science:

1. Probe the prompt optical emission of gamma ray bursts triggered by satellite observatories, such as the NASA Swift satellite Swift and Fermi.

2. Search for optical transients in coincidence with gravitational wave candidates triggered from LIGO. A positive coincidence would significantly increase the confidence of a gravitational wave detection.

3. An Earth orbiting space debris identification and tracking program is commencing.

Gamma Ray Bursts (GRBs)GRBs are the brightest explosions in the Universe.Theory and observation projects available using a robotic telescope network.Projects involve collaborators in France

Space debris and satellite trackingSpace debris is a serious problem for all countries that rely on satellites for security, communication and remote sensing.

The project will focus on developing dedicated software for tracking fast moving space debris and will use the robotic Zadko Telescope.

For expressions of interest, please contact: Prof. David Blair david.blair@uwa.edu.au A/Prof. Li Ju li.ju@uwa.edu.au Dr. Chunnong Zhao chunnong.zhao@uwa.edu.au Prof. Linqing Wen linqing.wen@uwa.edu.au A/Prof. David Coward david.coward@uwa.edu.au

Scholarships

Australian and New Zealand citizens and Australian permanent residents are legible to apply UWA post graduate Scholarship http://www.scholarships.uwa.edu.au/home/postgrad

International students can apply for International Postgraduate Research Scholarships (IPRS) and Scholarships for International Research Fees (SIRFs) http://www.scholarships.uwa.edu.au/home/postgrad/international/iprs

Outstanding candidates in receipt of Australian Postgraduate Awards or University Postgraduate Awards may be eligible to receive supplementary scholarships. Tutoring and part-time teaching may also be available for additional income.

Academic visitors: Many of our PhD students first visit here as academic visitors. We have had students and visitors from China, India, France, Chile, Austria, Poland, Singapore, Germany, Romania and USA. Visitors usually receive living allowance equal to the value of a PhD scholarship.