194 research outputs found
Gigantic Enhancement of Magneto-Chiral Effect in Photonic Crystals
We theoretically propose a method to enhance dramatically a
magneto-chiral(MC) effect by using the photonic crystals composed of a
multiferroic material. The MC effect, the directional birefringence even for
unpolarized light, is so small that it has been difficult to observe
experimentally. Two kinds of periodic structures are investigated; (a) a
multilayer and (b) a stripe composed of a magneto-chiral material and air. In
both cases, the difference in reflectivity between different magnetization
directions is enhanced by a factor of hundreds compared with a bulk material.Comment: 3 pages, 3 figure
Three-Dimensional Simulations of Standing Accretion Shock Instability in Core-Collapse Supernovae
We have studied non-axisymmetric standing accretion shock instability, or
SASI, by 3D hydrodynamical simulations. This is an extention of our previous
study on axisymmetric SASI. We have prepared a spherically symmetric and steady
accretion flow through a standing shock wave onto a proto-neutron star, taking
into account a realistic equation of state and neutrino heating and cooling.
This unperturbed model is supposed to represent approximately the typical
post-bounce phase of core-collapse supernovae. We then have added a small
perturbation (~1%) to the radial velocity and computed the ensuing evolutions.
Not only axisymmetric but non-axisymmetric perturbations have been also
imposed. We have applied mode analysis to the non-spherical deformation of the
shock surface, using the spherical harmonics. We have found that (1) the growth
rates of SASI are degenerate with respect to the azimuthal index m of the
spherical harmonics Y_l^m, just as expected for a spherically symmetric
background, (2) nonlinear mode couplings produce only m=0 modes for the
axisymmetric perturbations, whereas m=!0 modes are also generated in the
non-axisymmetric cases according to the selection rule for the quadratic
couplings, (3) the nonlinear saturation level of each mode is lower in general
for 3D than for 2D because a larger number of modes are contributing to
turbulence in 3D, (4) low l modes are dominant in the nonlinear phase, (5) the
equi-partition is nearly established among different m modes in the nonlinear
phase, (6) the spectra with respect to l obey power laws with a slope slightly
steeper for 3D, and (7) although these features are common to the models with
and without a shock revival at the end of simulation, the dominance of low l
modes is more remarkable in the models with a shock revival.Comment: 37 pages, 16 figures, and 1 table, submitted to Ap
Chiral meta-interface: Polarity reversal of ellipticity through double layers consisting of transparent chiral and absorptive achiral media
We have studied circular dichroism (CD) in the visible region of composite and double-layer films consisting of a transparent chiral molecule, glucose, and an absorptive achiral dye, rhodamine. Composite and double-layer films show an absorption-induced CD response caused by chirality of glucose at 540 nm, where the rhodamine exhibits absorption. More importantly, in double layers, the polarity of the ellipticity in CD signals is found to be reversed when the incident direction is reversed. We discuss the origin of the polarity reversal, which is very similar to the magneto-optical effect, at the chiral meta-interface without magnetic field
Direct Observation of Magnetochiral Effects through a Single Metamolecule in Microwave Regions
We report direct observation of magnetochiral (MCh) effects for the X-band microwaves through a single metamolecule consisting of a copper chiral structure and ferrite rod. A fictitious interaction between chirality and magnetism is realized in the metamolecule without intrinsic electronic interactions. The MCh effects are induced at the resonant optical activities by applying a weak dc magnetic field of 1 mT, and are increased with the magnetic field. The nonreciprocal differences in refractive indices are evaluated to be 10?3 at 200 mT
Metamaterials with magnetism and chirality
This review introduces and overviews electromagnetism in structured metamaterials which undergo simultaneous time-reversal and space-inversion symmetry breaking due to magnetism and chirality. Direct experimental observation of optical magnetochiral effects in a single metamolecule with magnetism and chirality is demonstrated at microwave frequencies. Numerical simulations based on a finite element method reproduce the experimental results well, and predict the emergence of giant magnetochiral effects, by combining resonances in the metamolecule. Toward the realization of magnetochiral effects at higher frequencies than microwaves, a metamolecule is miniaturized in the presence of ferromagnetic resonance in a cavity and coplanar waveguide. This work opens the door to the realization of a one-way mirror and synthetic gauge fields for electromagnetic waves
Observation of asymmetric electromagnetic field profiles in chiral metamaterials
We experimentally observe asymmetric electromagnetic field profiles along two-dimensional chiral metamaterials. The asymmetric field profiles depending on the chirality and the operation frequency have been reproduced well by the numerical simulation. Around a chiral meta-atom, distribution of a Poynting vector is found to be shifted asymmetrically. These results are explained in terms of an analogy with the side-jump mechanism in the electronic anomalous Hall systems
Focused Prefix Tuning for Controllable Text Generation
In a controllable text generation dataset, there exist unannotated attributes
that could provide irrelevant learning signals to models that use it for
training and thus degrade their performance. We propose focused prefix
tuning(FPT) to mitigate the problem and to enable the control to focus on the
desired attribute. Experimental results show that FPT can achieve better
control accuracy and text fluency than baseline models in single-attribute
control tasks. In multi-attribute control tasks, FPT achieves comparable
control accuracy with the state-of-the-art approach while keeping the
flexibility to control new attributes without retraining existing models.Comment: Accepted to the ACL 202
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