2. November 25, 2002Gustavus Adolphus College Catch the Gravity Wave: Searching for Einstein’s Elusive Prediction Rauha Rahkola, University of Oregon

3. November 25, 2002Gustavus Adolphus College Special Relativity Physics works the same in different reference frames Speed of light is constant in all frames & General Relativity –“generalizes” to frames of reference with a  0 –“special” because a=0

4. November 25, 2002Gustavus Adolphus College MASS CAUSES SPACE TO CURVE Einstein’s predictions using GR: What General Relativity tells us… verified –Perihelion shift of Mercury (twice what Newton predicted) 1916 –Light rays are bent near a massive star1919 –Gravitational waves1998???

5. November 25, 2002Gustavus Adolphus College Gravitational Waves Einstein describes GWs: Propagate information (gravitational field) at the speed of light Source of energy loss Two polarizations– ’+’ and ‘×’ Alter the dimensions of space perpendicular to axis of propagation Rendering of space stirred by two orbiting black holes: MOVING MASS CAUSES SPACE TO CURVE DYNAMICALLY

6. November 25, 2002Gustavus Adolphus College Important Signature of Gravitational Waves Gravitational waves shrink space along one axis perpendicular to the wave direction as they stretch space along another axis perpendicular both to the shrink axis and to the wave direction.

7. November 25, 2002Gustavus Adolphus College Exaggerated Picture of the Effects of Gravitational Radiation THIS IS YOUR BRAIN LIGO THIS IS A GRAVITY WAVE Time THIS IS YOUR BRAIN IN A GRAVITY WAVE ANY QUESTIONS?

8. November 25, 2002Gustavus Adolphus College PSR 1913+16: Evidence for GWs Slight energy loss (semi- stable orbits) –r , , T  Taylor and Hulse were awarded the 1993 Nobel Prize in Physics for this work. Circumstantial evidence – not a detection of gravity waves

9. November 25, 2002Gustavus Adolphus College Sources of Gravity-Waves All sources have two things in common: they’re dynamic they’re asymmetric Credits: Steve Snowden (supernova remnant); Kip Thorne (binary black hole diagram) Supernovae Binary end-stage More?

10. November 25, 2002Gustavus Adolphus College LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Brought to you by the National Science Foundation; operated by Caltech and MIT; the research focus for about 350 LIGO Science Collaboration members worldwide.

11. November 25, 2002Gustavus Adolphus College Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

12. November 25, 2002Gustavus Adolphus College Recycling Mirror Optical Cavity 4 km or 2-1/2 miles Beam Splitter Laser Photodetector Fabry-Perot-Michelson with Power Recycling

13. November 25, 2002Gustavus Adolphus College How Small is 10 -18 Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter

14. November 25, 2002Gustavus Adolphus College What Limits Sensitivity of Interferometers? Seismic noise & vibration limit at low frequencies Atomic vibrations (Thermal Noise) inside components limit at mid frequencies Quantum nature of light (Shot Noise) limits at high frequencies Myriad details of the lasers, electronics, etc., can make problems above these levels Sensitive region

15. November 25, 2002Gustavus Adolphus College LIGO Observatories

16. November 25, 2002Gustavus Adolphus College LIGO Schedule 1996Construction Underway (mostly civil) 1997Facility Construction (vacuum system) 1998Interferometer Construction (complete facilities) 1999Construction Complete (interferometers in vacuum) 2000Detector Installation (commissioning subsystems) 2001 Commission Interferometers (first coincidences) 2002Sensitivity studies (initiate LIGO I Science Run) 2003+ LIGO I data run (one year integrated data at h ~ 10 -21 ) 2006+Begin ‘Advanced LIGO’ installation

17. November 25, 2002Gustavus Adolphus College What UofO does for LIGO Data Characterization (separating the signal from the noise) –monitor the instrument (Global Diagnostics System) –monitor the environment (Physics Environment Monitoring System) –real-time programs to monitor data (Data Monitoring Tool) –track down glitches, frequency resonances (Noise Studies) Data Reduction –Start with ~4Mb / s –Reduce to ~1Gb / week (output) Data Analysis –Search for correlations between output & the environment –Search for GWs associated with Gamma Ray Bursts (GRBs)

18. November 25, 2002Gustavus Adolphus College Gamma Ray Bursts (GRBs) High-energy, short-duration electromagnetic radiation from extra-galactic sources Favored models point to exploding fireball –Involve large amounts of matter, –ejected at relativistic speeds, –producing a series of high-energy E/M shockwaves--- initially gamma-rays (some redshift to lower-energy gamma- rays or X-rays, others are absorbed), then X-rays (red-shifted to optical wavelengths), visible light may burst before, during, or after finally radio wavelengths http://online.itp.ucsb.edu/online/gamma_c99/piran/oh/06.html

19. November 25, 2002Gustavus Adolphus College Searching for GWs using GRBs as triggers Gamma ray bursts (GRBs) are high-energy, short duration E/M radiation from extra-galactic sources Why do we care? Gravitational Wave Bursts (GWBs) are possibly emitted from same source as GRBs Most probably, GWBs emitted before GRBs So, we can look for GWs specifically during times we see GRBs! GRB sources may be energetic enough to produce GWs that LIGO can see even now

20. November 25, 2002Gustavus Adolphus College Correlating output for two interferometers Goal: We want to see if evidence for GWs exist in both interferometers simultaneously 1 GW  Time-domain cross-correlation Several GWs  Frequency-domain cross-correlation Signal is too low for one c.c. value to be significant …but … A distribution of cross-correlation values is stationary over time… … except in the presence of gravity waves!

21. November 25, 2002Gustavus Adolphus College Testing the Null Hypothesis (based on method proposed by Finn, Mohanty, and Romano, gr-qc/9903101) Make two types of cross-correlated time series for two interferometers –“on-source”: cross-correlated during times containing possible GW –“off-source”: cross-correlated during (related) times which likely do not contain GW signals –Takes out uncorrelated noise while GW signal remains Repeat for many GRBs –Increases signal-to-noise Compare the two distributions of cross-correlations –Check if there is a statistical difference due to the GRB trigger

22. November 25, 2002Gustavus Adolphus College SURF’ing w/ LIGO (Catch the Wave, Man!) LIGO’s summer undergraduate research fellowship Work with a staff scientist @ Caltech or one of the observatories 2 ½ months w/ stipend (housing provided at the observatories) Spaces are limited – apply now!

23. November 25, 2002Gustavus Adolphus College Recent Undergraduate Projects 2002 (38 projects) Mapping of Synthetic Sapphire Optical Absorption at 1064nm Noise Characterization in the LIGO Livingston 4-km Interferometer An Improved Template Matching Algorithm for LIGO An Improved Actuator for Earth-Tide Compensation Characterization of Glitches in LHO Interferometers 2001 (24 projects) Automated Measurement of Sideband Power in the 2K Interferometer Tool Development for External Trigger Driven Burst Detection Core Optics Auto-Alignment Sequencer 2000 (25 projects) Commissioning the Tidal Compensation Servo Wavefront Sensing for the 40m LIGO Prototype

24. November 25, 2002Gustavus Adolphus College Benefits for Students Learn some general relativity Probe into current topics in astrophysics and cosmology (or other fields of physics) Hone/Increase your programming skills Experience one of the rising “new” fields of physics

25. November 25, 2002Gustavus Adolphus College Summary Gravity waves are a consequence of general relativity –Transfer information (curvature of space) at light speed –But, they need a lot of energy (mass) to be produced LIGO is a broadband method of detecting gravity waves –Limited by seismic noise (low freq), shot noise (high freq) –Goal is to be sensitive to 1:10 -21 We can look for associations between gravity waves and gamma ray bursts –Use correlated output from two (or more) interferometers –Test the null hypothesis for distributions of cross-correlations Plenty of research opportunities for undergraduates (& graduates!) –SURF program (see handout) –Possibly at a graduate school near you! (LIGO home page) –Also hiring operators on site