128,250 research outputs found
Electromagnetically Induced Transparency with Quantized Fields in Optocavity Mechanics
We report electromagnetically induced transparency using quantized fields in
optomechanical systems. The weak probe field is a narrow band squeezed field.
We present a homodyne detection of EIT in the output quantum field. We find
that the EIT dip exists even though the photon number in the squeezed vacuum is
at the single photon level. The EIT with quantized fields can be seen even at
temperatures of the order of 100 mK paving the way for using optomechanical
systems as memory elements.Comment: 6 pages, 5 figure
The lin-15 locus encodes two negative regulators of Caenorhabditis elegans vulval development
During Caenorhabditis elegans vulval development, an inductive signal from the anchor cell stimulates three of the six vulval precursor cells (VPCs) to adopt vulval rather than nonvulval epidermal fates. Genes necessary for this induction include the lin-3 growth factor, the let-23 receptor tyrosine kinase, and let-60 ras. lin-15 is a negative regulator of this inductive pathway. In lin-15 mutant animals, all six VPCs adopt vulval fates, even in the absence of inductive signal. Previous genetic studies suggested that lin-15 is a complex locus with two independently mutable activities, A and B. We have cloned the lin-15 locus by germline transformation and find that it encodes two nonoverlapping transcripts that are transcribed in the same direction. The downstream transcript encodes the lin-15A function; the upstream transcript encodes the lin-15B function. The predicted lin-15A and lin- 15B proteins are novel and hydrophilic. We have identified a molecular null allele of lin-15 and have used it to analyze the role of lin-15 in the signaling pathway. We find that lin-15 acts upstream of let-23 and in parallel to the inductive signal
Unification of Gravitation, Gauge Field and Dark Energy
This paper is composed of two correlated topics: 1. unification of
gravitation with gauge fields; 2. the coupling between the daor field and other
fields and the origin of dark energy. After introducing the concept of ``daor
field" and discussing the daor geometry, we indicate that the complex daor
field has two kinds of symmetry transformations. Hence the gravitation and
SU(1,3) gauge field are unified under the framework of the complex connection.
We propose a first-order nonlinear coupling equation of the daor field, which
includes the coupling between the daor field and SU(1,3) gauge field and the
coupling between the daor field and the curvature, and from which Einstein's
gravitational equation can be deduced. The cosmological observations imply that
dark energy cannot be zero, and which will dominate the doom of our Universe.
The real part of the daor field self-coupling equation can be regarded as
Einstein's equation endowed with the cosmological constant. It shows that dark
energy originates from the self-coupling of the space-time curvature, and the
energy-momentum tensor is proportional to the square of coupling constant
\lambda. The dark energy density given by our scenario is in agreement with
astronomical observations. Furthermore, the Newtonian gravitational constant G
and the coupling constant \epsilon of gauge field satisfy G=
\lambda^{2}\epsilon^{2}.Comment: 24 pages, revised version; references added; typos correcte
Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals
Negative refraction is demonstrated in one-dimensional (1D) dielectric
photonic crystals (PCs) at microwave frequencies. Focusing by plano-concave
lens made of 1D PC due to negative refraction is also demonstrated. The
frequency-dependent negative refractive indices, calculated from the
experimental data matches very well with those determined from band structure
calculations. The easy fabrication of one-dimensional photonic crystals may
open the door for new applications.Comment: 3 pages and 5 figure
Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites
Neutron scattering measurements on a magnetoresistive manganite
La(CaSr)MnO show that uncorrelated
dynamic polaronic lattice distortions are present in both the orthorhombic (O)
and rhombohedral (R) paramagnetic phases. The uncorrelated distortions do not
exhibit any significant anomaly at the O-to-R transition. Thus, both the
paramagnetic phases are inhomogeneous on the nanometer scale, as confirmed
further by strong damping of the acoustic phonons and by the anomalous
Debye-Waller factors in these phases. In contrast, recent x-ray measurements
and our neutron data show that polaronic correlations are present only in the O
phase. In optimally doped manganites, the R phase is metallic, while the O
paramagnetic state is insulating (or semiconducting). These measurements
therefore strongly suggest that the {\it correlated} lattice distortions are
primarily responsible for the insulating character of the paramagnetic state in
magnetoresistive manganites.Comment: 10 pages, 8 figures embedde
Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model
The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin
S=1/2 are dynamically investigated within the framework of a chiral constituent
quark model by solving a resonating group method (RGM) equation. The results
show that the interaction between Sigma_c and Dbar is attractive, which
consequently results in a Sigma_c Dbar bound state with the binding energy of
about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive
interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar
and Lambda_c Dbar is found to be negligible due to the fact that the gap
between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and
the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.Comment: 7 pages,2 figures. arXiv admin note: text overlap with
arXiv:nucl-th/0606056 by other author
- …