16,975 research outputs found
Coherent Destruction of Tunneling and Dark Floquet State
We study a system of three coherently coupled states, where one state is
shifted periodically against the other two. We discover such a system possesses
a dark Floquet state at zero quasienergy and always with negligible population
at the intermediate state. This dark Floquet state manifests itself dynamically
in terms of the suppression of inter-state tunneling, a phenomenon known as
coherent destruction of tunneling. We suggest to call it dark coherent
destruction of tunneling (DCDT). At high frequency limit for the periodic
driving, this Floquet state reduces to the well-known dark state widely used
for STIRAP. Our results can be generalized to systems with more states and can
be verified with easily implemented experiments within current technologies.Comment: 5 pages, 3 figure
Formation of hot subdwarf B stars with neutron star components
Binary population synthesis predicts the existence of subdwarf B stars (sdBs)
with neutron star (NS) or black hole (BH) companions. We systematically
investigate the formation of sdB+NS binaries from binary evolution and aim to
obtain some clues for a search for such systems. We started from a series of
MS+NS systems and determined the parameter spaces for producing sdB+NS binaries
from the stable Roche-lobe overflow (RLOF) channel and from the common envelope
(CE) ejection channel. Various NS accretion efficiencies and NS masses were
examined to investigate the effects they have. We show the characteristics of
the produced sdB+NS systems, such as the mass of components, orbital period,
the semi-amplitude of the radial velocity (K), and the spin of the NS
component. In the stable RLOF channel, the orbital period of sdB+NS binaries
produced in this way ranges from several days to more than 1000 days and moves
toward the short-period (~ hr) side with increasing initial MS mass. the sdB+NS
systems that result from CE ejection have very short orbital periods and then
high values of K (up to 800km s^-1). Such systems are born in very young
populations (younger than 0.3 Gyr) and are potential gravitational wave sources
that might be resolved by the Laser Interferometer Space Antenna (LISA) in the
future. Gravitational wave radiation may again bring them into contact on a
timescale of only ~Myr. As a consequence, they are rare and hard to discover.
The pulsar signal is likely a feature of sdB+NS systems caused by stable RLOF,
and some NS components in sdB binaries may be millisecond pulsars.Comment: 12 pages, 6 figures, 4 tables. Accepted for publication in A&
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