25 research outputs found
Constraining domain wall dark matter with a network of superconducting gravimeters and LIGO
There is strong astrophysical evidence that dark matter (DM) makes up some
27% of all mass in the universe. Yet, beyond gravitational interactions, little
is known about its properties or how it may connect to the Standard Model.
Multiple frameworks have been proposed, and precision measurements at low
energy have proven useful to help restrict the parameter space for many of
these models. One set of models predicts that DM is a scalar field that
"clumps" into regions of high local density, rather than being uniformly
distributed throughout the galaxy. If this DM field couples to the Standard
Model, its interaction with matter can be thought of as changing the effective
values of fundamental constants. One generic consequence of time variation of
fundamental constants (or their spatial variation as the Earth passes through
regions of varying density) is the presence of an anomalous,
composition-dependent acceleration. Here we show how this anomalous
acceleration can be measured using superconducting accelerometers, and
demonstrate that >20 years of archival data from the International Geodynamics
and Earth Tide Services (IGETS) network can be utilized to set new bounds on
these models. Furthermore, we show how LIGO and other gravitational wave
detectors can be used as exquisitely sensitive probes for narrow ranges of the
parameter space. While limited to DM models that feature spatial gradients,
these two techniques complement the networks of precision measurement devices
already in use for direct detection and identification of dark matter
Optical atomic coherence at the one-second time scale
Highest resolution laser spectroscopy has generally been limited to single
trapped ion systems due to rapid decoherence which plagues neutral atom
ensembles. Here, precision spectroscopy of ultracold neutral atoms confined in
a trapping potential shows superior optical coherence without any deleterious
effects from motional degrees of freedom, revealing optical resonance
linewidths at the hertz level with an excellent signal to noise ratio. The
resonance quality factor of 2.4 x 10^{14} is the highest ever recovered in any
form of coherent spectroscopy. The spectral resolution permits direct
observation of the breaking of nuclear spin degeneracy for the 1S0 and 3P0
optical clock states of 87Sr under a small magnetic bias field. This optical
NMR-like approach allows an accurate measurement of the differential Lande
g-factor between the two states. The optical atomic coherence demonstrated for
collective excitation of a large number of atoms will have a strong impact on
quantum measurement and precision frequency metrology.Comment: in press (2006
Systematic study of the Sr clock transition in an optical lattice
With ultracold Sr confined in a magic wavelength optical lattice, we
present the most precise study (2.8 Hz statistical uncertainty) to-date of the
- optical clock transition with a detailed analysis of
systematic shifts (20 Hz uncertainty) in the absolute frequency measurement of
429 228 004 229 867 Hz. The high resolution permits an investigation of the
optical lattice motional sideband structure. The local oscillator for this
optical atomic clock is a stable diode laser with its Hz-level linewidth
characterized across the optical spectrum using a femtosecond frequency comb.Comment: 4 pages, 4 figures, 1 tabl