1,957 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
Direct Detection of the Primordial Inflationary Gravitational Waves
Inflationary cosmology is successful in explaining a number of outstanding
cosmological issues including the flatness, the horizon and the relic issues.
More spectacular is the experimental confirmation of the structure as arose
from the inflationary quantum fluctuations. However, the physics in the
inflationary era is unclear. Polarization observations of Cosmic Microwave
Background (CMB) missions may detect the tensor mode effects of inflationary
gravitational waves (GWs) and give an energy scale of inflation. To probe the
inflationary physics, direct observation of gravitational waves generated in
the inflationary era is needed. In this essay, we advocate that the direct
observation of these GWs with sensitivity Omega-gw down to 10**(-23) is
possible using present projected technology development if foreground could be
separated.Comment: 6 pages, 1 figure, received an honorable mention in the 2009 Essay
Competition of the Gravity Research Foundatio
Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3
A NMR experiment recently done by Tou et al. on a heavy Fermion
superconductor UPt is interpreted in terms of a non-unitary spin-triplet
pairing state which we have been advocating. The proposed state successfully
explains various aspects of the seemingly complicated Knight shift behaviors
probed for major orientations, including a remarkable d-vector rotation under
weak fields. This entitles UPt as the first example that a charged many
body system forms a spin-triplet odd-par ity pairing at low temperatures and
demonstrates unambiguously that the putative spin-orbit coupling in UPt is
weak.Comment: 4 pages, 2 eps figures, to be published in J. Phys. Soc. Jpn. 67
(1998) No.
Dynamical Screening and Superconducting State in Intercalated Layered Metallochloronitrides
An essential property of layered systems is the dynamical nature of the
screened Coulomb interaction. Low energy collective modes appear as a
consequence of the layering and provide for a superconducting-pairing channel
in addition to the electron-phonon induced attractive interaction. We show that
taking into account this feature allows to explain the high critical
temperatures (Tc~26K) observed in recently discovered intercalated
metallochloronitrides. The exchange of acoustic plasmons between carriers leads
to a significant enhancement of the superconducting critical temperature that
is in agreement with the experimental observations
Quasiparticle Interactions for f-Impurity Anderson Model with Crystalline-Electric-Field: Numerical Renormalization Group Study
The aspect of the quasiparticle interaction of a local Fermi liquid, the
impurity version of f-based heavy fermions, is studied by the Wilson
numerical renormalization group method. In particular, the case of the
f-singlet crystalline-electric-field ground state is investigated assuming
the case of UPt with the hexagonal symmetry. It is found that the
interorbital interaction becomes larger than the intraorbital one in contrast
to the case of the bare Coulomb interaction for the parameters relevant to
UPt. This result offers us a basis to construct a microscopic theory of the
superconductivity of UPt where the interorbital interactions are expected
to play important roles.Comment: 9 pages, 5 figure
Effect of Spin-Orbit Interaction in Spin-Triplet Superconductor: Structure of -vector and Anomalous O-NQR Relaxation in SrRuO
Supposing the spin-triplet superconducting state of SrRuO, the
spin-orbit (SO) coupling associated with relative motion in Cooper pairs is
calculated by extending the method for the dipole-dipole coupling given by
Leggett in the superfluid He. It is shown that the SO coupling works only
in the equal-spin pairing (ESP) state to make the pair angular momentum
and the pair spin angular momentum parallel with each other. The SO coupling gives rise to the internal
Josephson effect in a chiral ESP state as in superfluid A-phase of He with
a help of an additional anisotropy arising from SO coupling of atomic origin
which works to direct the {\bf d}-vector into -plane. This resolves the
problem of the anomalous relaxation of O-NQR and the structure of {\bf
d}-vector in SrRuO.Comment: Accepted for publication in J. Phys. Soc. Jpn. vol.79 (2010), No.2
(February issue); 18 pages, 2 figure
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
Actitudes y creencias anticonceptivas entre los adultos jóvenes: Contraceptive Attitudes among Hmong Young Adults in Rural California
Introduction: While different contraceptive attitudes have been reported among different ethnic groups inthe US, little if any research has been conducted to understand the reproductive health needs and attitudesamong Hmong young adults. To our knowledge, this is the first study to investigate the relationship amongcontraceptive perception of this community. Objective: The purpose of this research was to identify attitudesthat influence Hmong college students’ contraceptive practices. Methods: A campus-wide online survey wasused as part of the data collection at a midsize institution in Central California. The questionnaire was a 32-items scale instrument called Contraceptive Attitude Scale (CAS), developed by Dr. Black. Results: Three hundred and forty-four students successfully completed the 32-items scale instrument CAS, which measured general contraceptive attitudes among Hmong young adults in rural California. The data reveals a high prevalence of unmarried (85%) Hmong college students reporting being sexually active (67%), with 62% having at least one sexual partner over the past 12 months; however, only 36% reported to use condom compared to 58% who did not use condoms during the last time of sexual intercourse. Conclusion: The findings indicated statistically significant differences between groups on the characteristics of sexual partners, contraceptive methods, marital status, birthplace, primary language spoken at home, years spent in college and years lived in the United States. The findings greatly contribute to the understanding of factors that influence contraceptive choices among the Hmong college population. More importantly, the information is crucial in designing programs to promote contraceptive knowledge and practices that are specific to the Hmong.Introducción: Si bien se informaron diferencias en las actitudes anticonceptivas entre los diferentes gruposétnicos en los EE. UU., Se ha realizado poca o ninguna investigación para comprender las necesidades yactitudes de salud reproductiva entre los adultos jóvenes hmong. Hasta donde sabemos, este es el primerestudio que investiga la relación entre la percepción anticonceptiva de esta comunidad. Objetivo: El propósito de esta investigación fue identificar actitudes que influyen en las prácticas anticonceptivas de los estudiantes universitarios de Hmong.Métodos: Se utilizó una encuesta en línea en todo el campus como parte de la recopilación de datos en una institución mediana en California Central. El cuestionario era un instrumento a escala de 32 ítems llamado Escala de Actitud Anticonceptiva (CAS), desarrollado por el Dra. Black. Resultados: Trescientos cuarenta y cuatro estudiantes completaron con éxito el instrumento CAS de escala de 32 ítems, que midió las actitudes anticonceptivas generales entre los adultos jóvenes Hmong en las zonas rurales de California. Los datos revelan una alta prevalencia de estudiantes universitarios Hmong solteros (85%) que informan ser sexualmente activos (67%), con 62% teniendo al menos una pareja sexual en los últimos 12 meses; sin embargo, solo el 36% informó usar condón en comparación con el 58% que no usó condón durante la última vez que tuvo relaciones sexuales. Conclusión: Los resultados indicaron diferencias estadísticamente significativas entre los grupos en cuanto a las características de las parejas sexuales, los métodos anticonceptivos, el estado civil, el lugar de nacimiento, el idioma principal que se habla en el hogar, los años que pasaron en la universidad y los años que vivieron en los Estados Unidos. Los hallazgos contribuyen en gran medida a la comprensión de los factores que influyen en las elecciones de anticonceptivos entre la población universitaria de Hmong. Más importante aún, la información es crucial en el diseño de programas para promover el conocimiento y las prácticas anticonceptivas que son específicos del Hmong
Josephson Current between Triplet and Singlet Superconductors
The Josephson effect between triplet and singlet superconductors is studied.
Josephson current can flow between triplet and singlet superconductors due to
the spin-orbit coupling in the spin-triplet superconductor but it is finite
only when triplet superconductor has , where and
are the perpendicular components of orbital angular momentum and spin angular
momentum of the triplet Cooper pairs, respectively. The recently observed
temperature and orientational dependence of the critical current through a
Josephson junction between UPt and Nb is investigated by considering a
non-unitary triplet state.Comment: 4 pages, no figure
- …