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Gravitational Waves Max Planck Institute for Gravitational Physics

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Gravitational Waves Max Planck Institute for Gravitational Physics Powered By Docstoc
					Gravitational Waves
     at the AEI

              Bernard Schutz


 Bernard.Schutz@aei.mpg.de
                                     Themes
• General relativity impacts astrophysics broadly today:
  black holes, neutron stars, gravitational lensing,
  cosmology, gravitational waves.
• Our main interest is in gravitational waves and their
  sources, mainly black holes and neutron stars.
• We are involved with detector development
  (GEO600, LIGO, LISA) and with numerical
  simulations of gravitational wave emission from black
  hole and neutron star collisions.

     Bernard F Schutz
     Albert Einstein Institute         AEI Ferienkurs: Astrophysical Relativity

     12 March 2004               2
                Astrophysical Relativity Groups
Numerical Relativity (Rezzolla) Gravitational Waves (Papa)
• Simulations of black hole and      • Astrophysics of GW sources
  neutron star dynamics, mergers • Data analysis for GEO, LIGO,
• Prediction of gravitational wave-    and VIRGO detectors
  forms                              • Designing LISA analysis system
• ~20 active scientists              • ~15 active scientists
• Peyote and Belladonna clusters • Merlin cluster, 1.3 Tflops peak
  provide one of the most powerful speed, 18 TB of data storage.
  computational facilities available   Expect to replace it this year with
  to any numerical relativity group    a facility 5 times as fast.
  worldwide.                         • Einstein@Home project
            Theoretical Gravitational Wave Physics (Chen)
    Design of advanced detectors. Gravitational wave data analysis. 5 scientists.
           Bernard F Schutz
           Albert Einstein Institute       AEI Ferienkurs: Astrophysical Relativity

           12 March 2004               3
                  Gravitational Wave Detection
• Gravitational waves are the most important prediction of Einstein
  that has not yet been verified by direct detection. The Hulse-
  Taylor pulsar system PSR1913+16 gives very strong indirect
  confirmation of the theory.
• Gravitational waves carry huge energies, but they interact very
  weakly with matter. These properties make them ideal probes of
  some of the most interesting parts of the Universe, now that we
  have learned how to make sufficiently sensitive detectors.
• Unlike in most of electromagnetic astronomy, gravitational waves
  will be observed coherently, following the phase of the wave.
  This is possible because of their relatively low frequencies (most
  interest is below 10 kHz). This makes detection strategies very
  different: instead of bolometric (energy) detection in hardware,
  gravitational wave detection will be by data analysis, in software.
        Bernard F Schutz
        Albert Einstein Institute       AEI Ferienkurs: Astrophysical Relativity

        12 March 2004               4
     GW physics across the spectrum
                             1        1
                        f     G ~            GM / R 3
                            2       2


                                                                               fhigh
                                                                                        108
                                                                               flow


                                                                   A chirping system is a GW
                                                                   standard candle: if position
                                                                   is known, distance can be
                                                                            inferred.



Bernard F Schutz
Albert Einstein Institute           AEI Ferienkurs: Astrophysical Relativity

12 March 2004               5
                                        Polarisation
• Gravitational waves have 2 independent polarisations, illustrated
  here by the motions of free “test” particles.




• They follow the motions of the source projected on the sky.
• Interferometers are linearly polarised detectors.
• A measurement of the degree of circular polarisation determines
  the inclination of a simple binary orbit. If the orbit is more
  complex, as for strong spin-spin coupling, then the changes in
  polarisation tell what is happening to the orbit.
        Bernard F Schutz
        Albert Einstein Institute            AEI Ferienkurs: Astrophysical Relativity

        12 March 2004               6
Worldwide Interferometer Network




Bernard F Schutz
Albert Einstein Institute       AEI Ferienkurs: Astrophysical Relativity

12 March 2004               7
Large Interferometers: the 1st Generation




   Bernard F Schutz
   Albert Einstein Institute       AEI Ferienkurs: Astrophysical Relativity

   12 March 2004               8
            GEO: Advanced Technology
                                          • GEO beats disadvantage of
                                            shorter baseline with advanced
                                            technology for controlling noise
                                            and adjusting bandwidth.
                                          • GEO is the only 1st-gen detector
                                            that can go narrow-band; will do
                                            best all-sky pulsar searches.
                                          • GEO’s technology will be used
                                            to make the Advanced LIGO
                                            upgrade. GEO responsible for
                                            suspensions and lasers. Funded
                                            by Max Planck Society and
                                            PPARC.
                                          • GEO upgrade to GEO-HF, also
                                            now funded by Max Planck
                                            Society and PPARC, will happen
                                            end of this decade.
Bernard F Schutz
Albert Einstein Institute       AEI Ferienkurs: Astrophysical Relativity

12 March 2004               9
LIGO performance in September 2005




        S5 data taking run is underway:
      At Design Sensitivity for 18 months!
   Bernard F Schutz
   Albert Einstein Institute   AEI Ferienkurs: Astrophysical Relativity

   12 March 2004          10

        Binary Inspiral Range 11 Mpc!
Data: Massive Volume, Massive Analysis
• The LSC records hundreds •         LIGO and GEO have jointly
  of terabytes of data per           developed data analysis software
  year. Most of this is              and are doing joint analysis of
  “housekeeping”. Signal             current data for upper limits.
  data around 500 GB/y.      •       New software have come from
• AEI responsible for pulsar         this:
  searches, contributes to             – Triana quick-look system (Cardiff)
  others                               – Coherent demodulation code (AEI)
• All-sky surveys for                  – Hough-transform hierarchical
                                         methods for all-sky surveys (AEI)
  pulsars very demanding:
  Einstein@Home giving us •          Grid efforts increasing:
  40 Tflops delivered,               GriPhyN, DataGrid,
  continuous.                        Triana/GridOneD

    Bernard F Schutz
    Albert Einstein Institute   AEI Ferienkurs: Astrophysical Relativity

    12 March 2004          11
Merlin Cluster


• 180 dual-processor
Athlon nodes
• 1.6 GHz clock speed
• 1.3 Tflop peak speed
• Storage capacity 18 TB

                                    Maria Alessandra Papa

   Bernard F Schutz
   Albert Einstein Institute   AEI Ferienkurs: Astrophysical Relativity

   12 March 2004          12
              Observe from Ground or Space?
                         Detectors are complementary
• Ground detectors –               •       Space detectors –
  - Can only observe at f > 1 Hz           - Required for f < 1 Hz
  because of gravity noise on              - Many strong sources
  Earth; can’t be screened.                - Many known sources
  - Events are rare, catastrophic.         - Expected:
  - Likely:                                     * Massive BH mergers
       * neutron-star in-spiral                 * Small BHs  larger ones
       (gamma-ray bursts?)                      * Known binaries
       * black-hole in-spiral              - Genuine tests of general
       * neutron stars                     relativity are possible because of
  - First detections are likely to         high S/N.
  be made from the ground.
         Bernard F Schutz
         Albert Einstein Institute    AEI Ferienkurs: Astrophysical Relativity

         12 March 2004          13
                            LISA




Bernard F Schutz
Albert Einstein Institute    AEI Ferienkurs: Astrophysical Relativity

12 March 2004          14
                            LISA in Orbit




Bernard F Schutz
Albert Einstein Institute        AEI Ferienkurs: Astrophysical Relativity

12 March 2004          15
                                LISA Sources
• Supermassive black holes in galactic centers
• Binary star systems in the Galaxy


                               LISA Organization
• Joint ESA-NASA project (50-50 sharing)
• Development guided by LISA International
  Science Team (LIST); 3 of the 14 European
  members are from AEI.
   Bernard F Schutz
   Albert Einstein Institute          AEI Ferienkurs: Astrophysical Relativity

   12 March 2004          16
     Gravitational Waves from Black Holes
• Generically, there are 3
  regimes in which black
  holes radiate:
   – Orbital in-spiral: post-
     Newtonian approximations
     or point-particle orbits.
   – Plunge/merger after the last
     stable orbit: numerical
     simulations or point-particle
     orbits.
   – Ring-down of the disturbed
     black hole as it settles down
     to a Kerr hole: perturbation                                               (Kip Thorne)


     theory of black holes.
        Bernard F Schutz
        Albert Einstein Institute    AEI Ferienkurs: Astrophysical Relativity

        12 March 2004          17
                   Plunge and Merger Radiation
• In the point-particle limit, we can calculate the orbit and the
  radiation reaction. But for two holes of comparable mass, we need
  numerical simulations. This is a major activity at the AEI, as well
  as at many other centers.
• GR is complex. First-order formulations of the vacuum field
  equations can contain 50 variables or more at each grid point. The
  largest supercomputers are still not big enough. Coordinate
  choices are very difficult and codes are so far not as robust as we
  would like.
• Recent breakthroughs at the AEI and in 4 other groups around the
  world have produced first full orbit simulations, merger
  simulations, believable waveform predictions. But much work
  still to be done.


        Bernard F Schutz
        Albert Einstein Institute   AEI Ferienkurs: Astrophysical Relativity

        12 March 2004          18
                                 LISA Data Analysis
• ESA and NASA are now developing the LISA DA system,
  much genuine research needed to solve source confusion
  problem.
• AEI played a leading role in specifying the goals of the
  system, and is now helping to coordinate the European
  collaboration: 50 institutes in 7 countries.
• At AEI we will increasingly concentrate effort in this area,
  expect to make 4-5 postdoctoral appointments in the next
  few years, support several PhD students.


     Bernard F Schutz
     Albert Einstein Institute           AEI Ferienkurs: Astrophysical Relativity

     12 March 2004          19
                 IMPRS Gravitational Waves

• Started this year, jointly with AEI/Hannover.
• Unique: only course in world where students get
  postgrad courses in detectors, theory, data
  analysis, and numerical work.
• Will take in ~5 students per year for a 3-year
  award.
• See AEI website for application procedure.

    Bernard F Schutz
    Albert Einstein Institute   AEI Ferienkurs: Astrophysical Relativity

    12 March 2004          20

				
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