Fakultäten » Mathematisch-naturwissenschaftliche Fakultät » Physik-Institut » Prof. Dr. Philippe Jetzer » Jetzer

Completed research project

Title / Titel Strong lensing of gravitational waves as seen by LISA
PDF Abstract (PDF, 14 KB)
Summary / Zusammenfassung We discussed strong gravitational lensing of gravitational waves from merging of massive
black hole binaries in the context of the LISA mission. Detection of multiple events
would provide invaluable information on competing theories of gravity, evolution and formation
of structures and, with complementary observations, constraints on H0 and other
cosmological parameters. Most of the optical depth for lensing is provided by intervening
massive galactic halos, for which wave optics effects are negligible. Probabilities to observe
multiple events are sizable for a broad range of formation histories. For the most
optimistic models, up to · 4 multiple events with a signal to noise ratio ¸ 8 are expected
in a 5-year mission. Chances are significant even for conservative models with either light
(· 60%) or heavy ( · 40%) seeds. Due to lensing amplification, some intrinsically too
faint signals are brought over threshold (· 2 per year).
In a further paper we showed that the detection of multiple gravitational lensing events
could provide a new tool for cosmography. Constraints on cosmological parameters
could be placed by exploiting either lensing statistics of strongly lensed sources or time
delay measurements of lensed gravitational wave signals. These lensing methods do not
need the measurement of the redshifts of the sources and the identification of their electromagnetic
counterparts. They would extend cosmological probes to redshift z < 10 and
are then complementary to other lower or higher redshift tests, such as type Ia supernovae
or cosmic microwave background. The accuracy of lensing tests strongly depends on the
formation history of the merging binaries, and the related number of total detectable
multiple images. Lensing amplification might also help to find the host galaxies. Any
measurement of the source redshifts would allow to exploit the distance-redshift test in
combination with lensing methods. Time-delay analyses might measure the Hubble parameter
H0 with accuracy of ¸ 10 km s^(−1) Mpc^(−1). With prior knowledge of H0, lensing
statistics and time delays might constrain the DM density, due to parameter
degeneracy). Inclusion of our methods with other available orthogonal techniques
might significantly reduce the uncertainty contours for ­M and the dark energy equation
of state.
Publications / Publikationen Phys. Rev. Lett., Volume 105, (2010), pp. 251101

Mont. Not. R. Astron. Soc., Volume 415, (2011), pp. 2773

Project leadership and contacts /
Projektleitung und Kontakte
Prof. Philippe Jetzer (Project Leader)
Funding source(s) /
Unterstützt durch
SNF (Personen- und Projektförderung)
In collaboration with /
In Zusammenarbeit mit
M. Sereno, Politecnico Torino Italy
Duration of Project / Projektdauer Jul 2010 to Jun 2011