2,203 research outputs found
Improved test of Lorentz Invariance in Electrodynamics using Rotating Cryogenic Sapphire Oscillators
We present new results from our test of Lorentz invariance, which compares
two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We
have now acquired over 1 year of data, allowing us to avoid the short data set
approximation (less than 1 year) that assumes no cancelation occurs between the
and parameters from the photon
sector of the standard model extension. Thus, we are able to place independent
limits on all eight and parameters.
Our results represents up to a factor of 10 improvement over previous non
rotating measurements (which independently constrained 7 parameters), and is a
slight improvement (except for ) over results from
previous rotating experiments that assumed the short data set approximation.
Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a
new limit on the isotropy parameter of
, an improvement of a factor of 2.Comment: Accepted for publication in Phys. Rev.
Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS III. The first global photometric metallicity map of the Galactic bulge
We investigate the large scale metallicity distribution in the Galactic
bulge, using a large spatial coverage, in order to constrain the bulge
formation scenario. We use the VISTA variables in the Via Lactea (VVV) survey
data and 2MASS photometry, covering 320 sqdeg of the Galactic bulge, to derive
photometric metallicities by interpolating of the (J-Ks)0 colors of individual
Red Giant Branch stars based on a set of globular cluster ridge lines. We then
use this information to construct the first global metallicity map of the bulge
with a resolution of 30'x45'. The metallicity map of the bulge revealed a clear
vertical metallicity gradient of ~0.04 dex/deg (~0.28 dex/kpc), with metal-rich
stars ([Fe/H]~0) dominating the inner bulge in regions closer to the galactic
plane (|b|<5). At larger scale heights, the mean metallicity of the bulge
population becomes significantly more metal-poor. This fits in the scenario of
a boxy-bulge originated from the vertical inestability of the Galactic bar,
formed early via secular evolution of a two component stellar disk. Older,
metal-poor stars dominate at higher scale heights due to the non-mixed orbits
from the originally hotter thick disk stars.Comment: Accepted for publication in A&
Extremely Low Loss Phonon-Trapping Cryogenic Acoustic Cavities for Future Physical Experiments
Low loss Bulk Acoustic Wave devices are considered from the point of view of
the solid state approach as phonon-confining cavities. We demonstrate effective
design of such acoustic cavities with phonon-trapping techniques exhibiting
extremely high quality factors for trapped longitudinally-polarized phonons of
various wavelengths. Quality factors of observed modes exceed 1 billion, with a
maximum -factor of 8 billion and product of at
liquid helium temperatures. Such high sensitivities allow analysis of intrinsic
material losses in resonant phonon systems. Various mechanisms of phonon losses
are discussed and estimated
Towards achieving strong coupling in 3D-cavity with solid state spin resonance
We investigate the microwave magnetic field confinement in several microwave
3D-cavities, using 3D finite-element analysis to determine the best design and
achieve strong coupling between microwave resonant cavity photons and solid
state spins. Specifically, we design cavities for achieving strong coupling of
electromagnetic modes with an ensemble of nitrogen vacancy (NV) defects in
diamond. We report here a novel and practical cavity design with a magnetic
filling factor of up to 4 times (2 times higher collective coupling) than
previously achieved using 1D superconducting cavities with small mode volume.
In addition, we show that by using a double-split resonator cavity, it is
possible to achieve up to 200 times better cooperative factor than the
currently demonstrated with NV in diamond. These designs open up further
opportunities for studying strong and ultra-strong coupling effects on spins in
solids using alternative systems with a wider range of design parameters.Comment: 20 pages, 9 figure
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