36 research outputs found
A hypothetical effect of the Maxwell-Proca electromagnetic stresses on galaxy rotation curves
The Maxwell-Proca electrodynamics corresponding to a finite photon mass
causes a substantial change of the Maxwell stress tensor and, under certain
circumstances, may cause the electromagnetic stresses to act effectively as
"negative pressure." The paper describes a model where this negative pressure
imitates gravitational pull and may produce forces comparable to gravity and
even become dominant. The effect is associated with the random magnetic fields
in the galactic disk with a scale exceeding the photon Compton wavelength. The
presence of a weaker regular field does not affect the forces under
consideration. The stresses act predominantly on the interstellar gas and cause
an additional force pulling the gas towards the center and towards the galactic
plane. The stars do not experience any significant direct force but get
involved in this process via a "recycling loop" where rapidly evolving massive
stars are formed from the gas undergoing galactic rotation and then lose their
masses back to the gas within a time shorter than roughly 1/6 of the rotation
period. This makes their dynamics inseparable from that of the rotating gas.
The lighter, slowly evolving stars, as soon as they are formed, lose connection
to the gas and are confined within the galaxy only gravitationally. Numerical
examples based on the parameters of our galaxy reveal both opportunities and
challenges of this model and motivate further analysis. The critical issue is
the plausibility of formation of the irregular magnetic field that would be
force free. Another challenge is developing a predictive model of the evolution
of the gaseous and stellar population of the galaxy under the aforementioned
scenario. It may be interesting to also explore possible broader cosmological
implications of the negative-pressure model.Comment: 29 pages, 1 figur
Precision measurement of light shifts at two off-resonant wavelengths in a single trapped Ba+ ion and determination of atomic dipole matrix elements
We define and measure the ratio (R) of the vector ac-Stark effect (or light
shift) in the 6S_1/2 and 5D_3/2 states of a single trapped barium ion to 0.2%
accuracy at two different off-resonant wavelengths. We earlier found R =
-11.494(13) at 514.531nm and now report the value at 1111.68nm, R = +0.4176(8).
These observations together yield a value of the matrix element,
previously unknown in the literature. Also, comparison of our results with an
ab initio calculation of dynamic polarizability would yield a new test of
atomic theory and improve the understanding of atomic structure needed to
interpret a proposed atomic parity violation experiment.Comment: 12 pages, 11 figures, in submission to PR
Can a quantum nondemolition measurement improve the sensitivity of an atomic magnetometer?
Noise properties of an idealized atomic magnetometer that utilizes spin
squeezing induced by a continuous quantum nondemolition measurement are
considered. Such a magnetometer measures spin precession of atomic spins by
detecting optical rotation of far-detuned light. Fundamental noise sources
include the quantum projection noise and the photon shot-noise. For measurement
times much shorter than the spin-relaxation time observed in the absence of
light () divided by , the optimal sensitivity of the
magnetometer scales as , so an advantage over the usual sensitivity
scaling as can be achieved. However, at longer measurement times,
the optimized sensitivity scales as , as for a usual shot-noise
limited magnetometer. If strongly squeezed probe light is used, the Heisenberg
uncertainty limit may, in principle, be reached for very short measurement
times. However, if the measurement time exceeds , the
scaling is again restored.Comment: Some details of calculations can be found in a companion note:
physics/040712
Search for plant biomagnetism with a sensitive atomic magnetometer
We report what we believe is the first experimental limit placed on plant
biomagnetism. Measurements with a sensitive atomic magnetometer were performed
on the Titan arum (Amorphophallus titanum) inflorescence, known for its fast
bio-chemical processes while blooming. We find that the surface magnetic field
from these processes, projected along the Earth's magnetic field, and measured
at the surface of the plant, is less then ~0.6uG.Comment: 5 pages, 5 figures, to be published - modified one sentence in
abstract + reformatted fi
Nondestructive in-line sub-picomolar detection of magnetic nanoparticles in flowing complex fluids
Over the last decades, the use of magnetic nanoparticles in research and
commercial applications has increased dramatically. However, direct detection
of trace quantities remains a challenge in terms of equipment cost, operating
conditions and data acquisition times, especially in flowing conditions within
complex media. Here we present the in-line, non-destructive detection of
magnetic nanoparticles using high performance atomic magnetometers at ambient
conditions in flowing media. We achieve sub-picomolar sensitivities measuring
30 nm ferromagnetic iron and cobalt nanoparticles that are suitable for
biomedical and industrial applications, under flowing conditions in water and
whole blood. Additionally, we demonstrate real-time surveillance of the
magnetic separation of nanoparticles from water and whole blood. Overall our
system has the merit of inline direct measurement of trace quantities of
ferromagnetic nanoparticles with so far unreached sensitivities and could be
applied in the biomedical field (diagnostics and therapeutics) but also in the
industrial sector
Infrared absorption band and vibronic structure of the nitrogen-vacancy center in diamond
Negatively charged nitrogen-vacancy (NV-) color centers in diamond have generated much interest for use in quantum technology. Despite the progress made in developing their applications, many questions about the basic properties of NV- centers remain unr
Optical Magnetometry
Some of the most sensitive methods of measuring magnetic fields utilize
interactions of resonant light with atomic vapor. Recent developments in this
vibrant field are improving magnetometers in many traditional areas such as
measurement of geomagnetic anomalies and magnetic fields in space, and are
opening the door to new ones, including, dynamical measurements of bio-magnetic
fields, detection of nuclear magnetic resonance (NMR), magnetic-resonance
imaging (MRI), inertial-rotation sensing, magnetic microscopy with cold atoms,
and tests of fundamental symmetries of Nature.Comment: 11 pages; 4 figures; submitted to Nature Physic
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.publishedVersio
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies
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Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies