19,157 research outputs found
Building a 3.5 m prototype interferometer for the Q & A vacuum birefringence experiment and high precision ellipsometry
We have built and tested a 3.5 m high-finesse Fabry-Perot prototype
inteferometer with a precision ellipsometer for the QED test and axion search
(Q & A) experiment. We use X-pendulum-double-pendulum suspension designs and
automatic control schemes developed by the gravitational-wave detection
community. Verdet constant and Cotton-Mouton constant of the air are measured
as a test. Double modulation with polarization modulation 100 Hz and
magnetic-field modulation 0.05 Hz gives 10^{-7} rad phase noise for a 44-minute
integration.Comment: This draft has been presented in the 5th Edoardo Amaldi Conference on
Gravitational Wave
Substrate effects on quasiparticles and excitons in graphene nanoflakes
The effects of substrate on electronic and optical properties of triangular
and hexagonal graphene nanoflakes with armchair edges are investigated by using
a configuration interaction approach beyond double excitation scheme. The
quasiparticle correction to the energy gap and exciton binding energy are found
to be dominated by the long-range Coulomb interactions and exhibit similar
dependence on the dielectric constant of the substrate, which leads to a
cancellation of their contributions to the optical gap. As a result, the
optical gaps are shown to be insensitive to the dielectric environment and
unexpectedly close to the single-particle gaps.Comment: 4 pages, 4 figure
Neutrino masses and mixings
We propose a novel theoretical understanding of neutrino masses and mixings,
which is attributed to the intrinsic vector-like feature of the regularized
Standard Model at short distances. We try to explain the smallness of Dirac
neutrino masses and the decoupling of the right-handed neutrino as a free
particle. Neutrino masses and mixing angles are completely related to each
other in the Schwinger-Dyson equations for their self-energy functions. The
solutions to these equations and a possible pattern of masses and mixings are
discussed.Comment: LaTex 11 page
Spin states and persistent currents in a mesoscopic ring with an embedded magnetic impurity
Spin states and persistent currents are investigated theoretically in a
mesoscopic ring with an embedded magnetic ion under a uniform magnetic field
including the spin-orbit interactions. The magnetic impurity acts as a
spin-dependent -potential for electrons and results in gaps in the
energy spectrum, consequently suppresses the oscillation of the persistent
currents. The competition between the Zeeman splittings and the -
exchange interaction leads to a transition of the electron ground state in the
ring. The interplay between the periodic potential induced by the Rashba and
Dresselhaus spin-orbit interactions and the -potential induced by the
magnetic impurity leads to significant variation in the energy spectrum, charge
density distribution, and persistent currents of electrons in the ring.Comment: 8 pages, 11 figure
The finite-temperature thermodynamics of a trapped unitary Fermi gas within fractional exclusion statistics
We utilize a fractional exclusion statistics of Haldane and Wu hypothesis to
study the thermodynamics of a unitary Fermi gas trapped in a harmonic
oscillator potential at ultra-low finite temperature. The entropy per particle
as a function of the energy per particle and energy per particle versus
rescaled temperature are numerically compared with the experimental data. The
study shows that, except the chemical potential behavior, there exists a
reasonable consistency between the experimental measurement and theoretical
attempt for the entropy and energy per particle. In the fractional exclusion
statistics formalism, the behavior of the isochore heat capacity for a trapped
unitary Fermi gas is also analyzed.Comment: 6 pages, 6 figure
Spin states and persistent currents in mesoscopic rings: spin-orbit interactions
We investigate theoretically electron spin states in one dimensional (1D) and
two dimensional (2D) hard-wall mesoscopic rings in the presence of both the
Rashba spin-orbit interaction (RSOI) and the Dresselhaus spin-orbit interaction
(DSOI) in a perpendicular magnetic field. The Hamiltonian of the RSOI alone is
mathematically equivalent to that of the DSOI alone using an SU(2) spin
rotation transformation. Our theoretical results show that the interplay
between the RSOI and DSOI results in an effective periodic potential, which
consequently leads to gaps in the energy spectrum. This periodic potential also
weakens and smoothens the oscillations of the persistent charge current (CC)
and spin current (SC) and results in the localization of electrons. For a 2D
ring with a finite width, higher radial modes destroy the periodic oscillations
of persistent currents.Comment: 12 pages, 14 figure
QCD Effects in High Energy Processes
In this talk, some important QCD effects in Higgs physics, supersymmetry and
top physics, as well as the factorization and resummation techniques in QCD are
reviewed.Comment: LaTeX, 13 pages, uses ws-ijmpa.cls. Based on an invited talk at the
International Conference on QCD and Hadronic Physics, Beijing, China, June
16--20, 2005. Minor change
Fluctuations in a diffusive medium with gain
We present a stochastic model for amplifying, diffusive media like, for
instance, random lasers. Starting from a simple random-walk model, we derive a
stochastic partial differential equation for the energy field with contains a
multiplicative random-advection term yielding intermittency and power-law
distributions of the field itself. Dimensional analysis indicate that such
features are more likely to be observed for small enough samples and in lower
spatial dimensions
The detection of lubricating oil viscosity changes in gearbox transmission systems driven by sensorless variable speed drives using electrical supply parameters
Lubrication oil plays a decisive role to maintain a reliable and efficient operation of gear transmissions. Many offline methods have been developed to monitor the quality of lubricating oils. This work focus on developing a novel online method to diagnose oil degradation based on the measurements from power supply system to the gearbox. Experimental studies based on an 10kW industrial gearbox fed by a sensorless variable speed drive (VSD) shows that measurable changes in both static power and dynamic behaviour are different with lube oils tested. Therefore, it is feasible to use the static power feature to indicate viscosity changes at low and moderate operating speeds. In the meantime, the dynamic feature can separate viscosity changes for all different tested cases
Leibniz 2-algebras and twisted Courant algebroids
In this paper, we give the categorification of Leibniz algebras, which is
equivalent to 2-term sh Leibniz algebras. They reveal the algebraic structure
of omni-Lie 2-algebras introduced in \cite{omniLie2} as well as twisted Courant
algebroids by closed 4-forms introduced in \cite{4form}.
We also prove that Dirac structures of twisted Courant algebroids give rise
to 2-term -algebras and geometric structures behind them are exactly
-twisted Lie algebroids introduced in \cite{Grutzmann}.Comment: 22 pages, to appear in Comm. Algebr
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