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报告内容
摘要
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Pulsars
are extraordinarily good clocks. This property has been exploited
in a wide range of applications ranging from studying the interiors of
neutron stars to testing theories of gravitation. Many pulsars, especially
millisecond pulsars, are in orbit around another star, providing a near-ideal
gravitational laboratory. Double-neutron-star systems such as the Double
Pulsar provide the most stringent tests of gravitational theories in
strong-field environments. A Pulsar Timing Array (PTA) can in principle give
a direct detection of GWs at nanohertz frequencies. A secondary goal of PTA
projects is the establishment of a “pulsar timescale” which, over long time
intervals, may be more accurate than the best available timescales based on
atomic clocks. Since mid-2004, the Parkes Pulsar Timing Array (PPTA) project
has been making regular timing measurements of 20 millisecond pulsars with
steadily improving precision. While we do not yet have a significant GW
detection, our current upper limit seriously constrains standard models for
galaxy evolution and formation of super-massive black holes in galaxy cores.
In collaboration with the European and North American PTAs we have formed the
International Pulsar Timing Array (IPTA) to enhance progress toward PTA goals.
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