54 research outputs found
Pseudoscalar-photon Interactions, Axions, Non-Minimal Extensions, and Their Empirical Constraints from Observations
Pseudoscalar-photon interactions were proposed in the study of the relations
among equivalence principles. The interaction of pseudoscalar axion with gluons
was proposed as a way to solve the strong CP problem. Subsequent proposal of
axion as a dark matter candidate has been a focus of search. Motivation from
superstring theories add to its importance. After a brief introduction and
historical review, we present (i) the current status of our optical experiment
using high-finesse Fabry-Perot resonant cavity - Q & A experiment - to detect
pseudoscalar-photon interactions, (ii) the constraints on pseudoscalar-photon
interactions from astrophysical and cosmological observations on cosmic
polarization rotation, and (iii) theoretical models of non-minimal interactions
of gravitational, electromagnetic and pseudoscalar (axion) fields, and their
relevance to cosmology.Comment: 8 page
New constraints on cosmic polarization rotation from the ACTPol cosmic microwave background B-Mode polarization observation and the BICEP2 constraint update
Recently ACTPol has measured the cosmic microwave background (CMB) B-mode and
E-mode polarizations and obtained TE, EE, BB, TB and EB power spectra in the
multipole range 225-8725. In our previous paper (Ap. J. 792 (2014) 35 [Paper
I]), we have analyzed jointly the results of three experiments on the CMB
B-mode polarization -- SPTpol, POLARBEAR and BICEP2 to include in the model, in
addition to the gravitational lensing and the inflationary gravitational waves
components, also the fluctuation effects induced by the cosmic polarization
rotation (CPR), if it exists within the upper limits at the time. In this
paper, we fit both the mean CPR angle and its fluctuation
from the new ACTPol data, and update our fitting of CPR
fluctuations using BICEP2 data taking the new Planck dust measurement results
into consideration. We follow the method of Paper I. The mean CPR angle is
constrained from the EB correlation power spectra to || < 14 mrad
(0.8{\deg}) and the fluctuation (rms) is constrained from the BB correlation
power spectra to 1/2 < 29.3 mrad (1.68{\deg}). Assuming that
the polarization angle of Tau A does not change from 89.2 to 146 GHz, the
ACTPol data give = 1.0 {\pm} 0.63{\deg}. These results suggest that
the inclusion of the present ACTPol data is consistent with no CPR detection.
With the new Planck dust measurement, we update our fits of the BICEP2 CPR
fluctuation constraint to be 32.8 mrad (1.88{\deg}). The joint
ACTpol-BICEP2-POLARBEAR CPR fluctuation constraint is 23.7 mrad (1.36{\deg}).Comment: 15 pages, 2 figures, 2 tables, version to match the accepted
submission to ApJ. Unfortunately there is a sign error in equation (6b). This
propagated to equations (7b) and (8a) and to the results for \alpha_\beta.
The errors in the last raw of Table 1 had been overestimated and correcte
Relationships between stress, coping and depressive symptoms among overseas university preparatory Chinese students: a cross-sectional study
<p>Abstract</p> <p>Background</p> <p>Mental health problems in young people are an important public health issue. Students leaving their hometown and family at a young age to pursue better educational opportunities overseas are confronted with life adjustment stress, which in turn affects their mental health and academic performance. This study aimed to examine the relationships among stress, coping strategies, and depressive symptoms using the stress coping framework in overseas Chinese university preparatory students in Taiwan.</p> <p>Methods</p> <p>A cross-sectional study was conducted at an overseas Chinese university preparatory institute in Taiwan. Of enrolled overseas Chinese university preparatory students at 2009, 756 completed a structured questionnaire measuring stress, strategies for coping with it, and the Center for Epidemiologic Studies Depression Scale.</p> <p>Results</p> <p>High levels of stress significantly predicted the adoption of active, problem-focused coping strategies (<it>R</it><sup>2 </sup>= 0.13<!-- entity --><it>, p </it>< .01) and passive, emotion-focused coping strategies (<it>R</it><sup>2 </sup>= 0.24<!-- entity --><it>, p </it>< .01). Acceptable CFI, SRMR, and RMSEA values from the structural equation modeling analysis demonstrated that the model satisfactorily fits the stress coping framework, after active coping strategies were eliminated from the model. Results from the Sobel test revealed that passive coping strategies mediated the relation between stress and depressive symptoms (<it>z </it>= 8.06, <it>p </it>< .001).</p> <p>Conclusion</p> <p>Our study results suggested that stress is associated with coping strategies and depressive symptoms and passive strategies mediate the relation between stress and depressive symptoms in overseas Chinese university preparatory students.</p
Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus
Experiments for vacuum birefringence and vacuum dichroism have been set up
with high-finesse high magnetic experimental apparatuses, which seem to be
ideal for small gaseous Cotton-Mouton effect (CME) measurements. PVLAS
Collaboration has measured CMEs in krypton, xenon and neon at the wavelength of
1064 nm. In this Letter, we report on our measurement of CMEs in nitrogen,
oxygen, carbon dioxide, argon, and krypton at the same wavelength in a magnetic
field B = 2.3 T at pressure P = 0.5-300 Torr and temperature T = 295-298 K. Our
results agree with the PVLAS results in the common cases.Comment: 8 pages, 2 tables, 5 figures, submitted to Chemical Physics Letters.
Some modifications are made in the revision according to the referee's
comments: Donotations in equations are unified. Error in quoting numbers in 2
places in Table 2 is corrected. Uncertainty in modulation depth is included
in the total systematic error. References are order re-arrange
Erratum: "New Constraints on Cosmic Polarization Rotation from the ACTPol Cosmic Microwave Background B-mode Polarization Observation and the BICEP2 Constraint Update" (2015, ApJ, 805, 107)
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Ellipsometry noise spectrum, suspension transfer function measurement and closed-loop control of the suspension system in the Q & A experiment
The Q & A experiment, aiming at the detection of vacuum birefringence
predicted by quantum electrodynamics, consists mainly of a suspended 3.5 m
Fabry-Perot cavity, a rotating permanent dipole magnet and an ellipsometer. The
2.3 T magnet can rotate up to 10 rev/s, introducing an ellipticity signal at
twice the rotation frequency. The X-pendulum gives a good isolation ratio for
seismic noise above its main resonant frequency 0.3 Hz. At present, the
ellipsometry noise decreases with frequency, from 1*10^{-5} rad Hz^{-1/2} at 5
Hz, 2*10^{-6} rad Hz^{-1/2} at 20 Hz to 5*10^{-7} rad Hz^{-1/2} at 40 Hz. The
shape of the noise spectrum indicates possible improvement can be made by
further reducing the movement between the cavity mirrors. From the preliminary
result of yaw motion alignment control, it can be seen that some peaks due to
yaw motion of the cavity mirror was suppressed. In this paper, we first give a
schematic view of the Q & A experiment, and then present the measurement of
transfer function of the compound X-pendulum-double pendulum suspension. A
closed-loop control was carried out to verify the validity of the measured
transfer functions. The ellipsometry noise spectra with and without yaw
alignment control and the newest improvement is presented.Comment: 7 pages, 5 figures, presented in 6th Edoardo Amaldi Conference on
Gravitational Waves, June 2005, Okinawa Japan and submitted to Journal of
Physics: Conference Series. Some modifications are made according to the
referee's comments: mainly to explain the relation between the displacement
of cavity mirror and the ellipticity noise spectru
Q & A Experiment to Search for Vacuum Dichroism, Pseudoscalar-Photon Interaction and Millicharged Fermions
A number of experiments are underway to detect vacuum birefringence and
dichroism -- PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed
optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical
interpretations of this result include a possible pseudoscalar-photon
interaction and the existence of millicharged fermions. Here, we report the
progress and first results of Q & A (QED [quantum electrodynamics] and Axion)
experiment proposed and started in 1994. A 3.5-m high-finesse (around 30,000)
Fabry-Perot prototype detector extendable to 7-m has been built and tested. We
use X-pendulums and automatic control schemes developed by the
gravitational-wave detection community for mirror suspension and cavity
control. To polarize the vacuum, we use a 2.3-T dipole permanent magnet, with
27-mm-diameter clear borehole and 0.6-m field length,. In the experiment, the
magnet is rotated at 5-10 rev/s to generate time-dependent polarization signal
with twice the rotation frequency. Our
ellipsometer/polarization-rotation-detection-system is formed by a pair of
Glan-Taylor type polarizing prisms with extinction ratio lower than 10-8
together with a polarization modulating Faraday Cell with/without a quarter
wave plate. We made an independent calibration of our apparatus by performing a
measurement of gaseous Cotton-Mouton effect of nitrogen. We present our first
experimental results and give a brief discussion of our experimental limit on
pseudo-scalar-photon interaction and millicharged fermions.Comment: 21 pages, 13 figures, submitted to Modern Physics Letter
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