4,284 research outputs found
Entanglement dynamics of two independent Jaynes-Cummings atoms without rotating-wave approximation
Entanglement evolution of two independent Jaynes-Cummings atoms without
rotating-wave approximation (RWA) is studied by an numerically exact approach.
The previous results in the RWA are essentially modified in the strong coupling
regime (), which has been reached in the recent experiments on the
flux qubit coupled to the LC resonator. For the initial Bell state with
anti-correlated spins, the entanglement sudden death (ESD) is absent in the
RWA, but does appear in the present numerical calculation without RWA.
Aperiodic entanglement evolution in the strong coupling regime is observed. The
strong atom-cavity coupling facilitates the ESD. The sign of detuning play a
essential role in the entanglement evolution for strong coupling, which is
irrelevant in the RWA. An analytical results based on an unitary transformation
are also given, which could not modify the RWA picture essentially. It is
suggested that the activation of the photons may be the origin of the ESD. The
present theoretical results could be applied to artificial atoms realized in
recent experiments.Comment: 16 pages, 8 figure
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A regioselectivity switch in Pd-catalyzed hydroallylation of alkynes.
By exploiting the reactivity of a vinyl-Pd species, we control the regioselectivity in hydroallylation of alkynes under Pd-hydride catalysis. A monophosphine ligand and carboxylic acid combination promotes 1,5-dienes through a pathway involving isomerization of alkynes to allenes. In contrast, a bisphosphine ligand and copper cocatalyst favor 1,4-dienes via a mechanism that involves transmetalation. Our study highlights how to access different isomers by diverting a common organometallic intermediate
Remarks on Hawking radiation as tunneling from the BTZ black holes
Hawking radiation viewed as a semiclassical tunneling process from the event
horizon of the (2 + 1)-dimensional rotating BTZ black hole is carefully
reexamined by taking into account not only the energy conservation but also the
conservation of angular momentum when the effect of the emitted particle's
self-gravitation is incorporated. In contrast to previous analysis of this
issue in the literature, our result obtained here fits well to the
Kraus-Parikh-Wilczek's universal conclusion without any modification to the
Bekenstein-Hawking area-entropy formulae of the BTZ black hole.Comment: 12pages, no figure, use JHEP3.cls. Version better than published one
in JHE
Superconducting state in the non-centrosymmetric Mg_{9.3}Ir_{19}B_{16.7} and Mg_{10.5}Ir_{19}B_{17.1} revealed by NMR
We report ^{11}B NMR measurements in non-centrosymmetric superconductors
Mg_{9.3}Ir_{19}B_{16.7} (T_c=5.8 K) and Mg_{10.5}Ir_{19}B_{17.1} (T_c=4.8 K).
The spin lattice relaxation rate and the Knight shift indicate that the Cooper
pairs are predominantly in the spin-singlet state with an isotropic gap.
However, Mg_{10.5}Ir_{19}B_{17.1} is found to have more defects and the spin
susceptibility remains finite even in the zero-temperature limit. We interpret
this result as that the defects enhance the spin-orbit coupling and bring about
more spin-triplet component.Comment: for a proper, high-resolution Fig.5, contact the corresponding autho
Fidelity susceptibility and long-range correlation in the Kitaev honeycomb model
We study exactly both the ground-state fidelity susceptibility and bond-bond
correlation function in the Kitaev honeycomb model. Our results show that the
fidelity susceptibility can be used to identify the topological phase
transition from a gapped A phase with Abelian anyon excitations to a gapless B
phase with non-Abelian anyon excitations. We also find that the bond-bond
correlation function decays exponentially in the gapped phase, but
algebraically in the gapless phase. For the former case, the correlation length
is found to be , which diverges
around the critical point .Comment: 7 pages, 6 figure
Quantum theory of light diffraction
At present, the theory of light diffraction only has the simple wave-optical
approach. In this paper, we study light diffraction with the approach of
relativistic quantum theory. We find that the slit length, slit width, slit
thickness and wave-length of light have affected to the diffraction intensity
and form of diffraction pattern. However, the effect of slit thickness on the
diffraction pattern can not be explained by wave-optical approach, and it can
be explained in quantum theory. We compare the theoretical results with single
and multiple slits experiment data, and find the theoretical results are
accordance with the experiment data. Otherwise, we give some theory prediction.
We think all the new prediction will be tested by the light diffraction
experiment.Comment: 10 page
Controlling the spin orientation of photoexcited electrons by symmetry breaking
We study reflection of optically spin-oriented hot electrons as a means to
probe the semiconductor crystal symmetry and its intimate relation with the
spin-orbit coupling. The symmetry breaking by reflection manifests itself by
tipping the net-spin vector of the photoexcited electrons out of the light
propagation direction. The tipping angle and the pointing direction of the
net-spin vector are set by the crystal-induced spin precession, momentum
alignment and spin-momentum correlation of the initial photoexcited electron
population. We examine non-magnetic semiconductor heterostructures and
semiconductor/ferromagnet systems and show the unique signatures of these
effects.Comment: 4 pages, 3 figures, resubmitte
Comparative investigation of damage induced by diatomic and monoatomic ion implantation in silicon
The damaging effect of mono- and diatomic phosphorus and arsenic ions implanted into silicon was investigated by spectroscopic ellipsometry (SE) and high-depth-resolution Rutherford backscattering and channeling techniques. A comparison was made between the two methods to check the capability of ellipsometry to examine the damage formed by room temperature implantation into silicon. For the analysis of the spectroscopic ellipsometry data we used the conventional method of assuming appropriate optical models and fitting the model parameters (layer thicknesses and volume fractions of the amorphous silicon component in the layers) by linear regression. The depth dependence of the damage was determined by both methods. It was revealed that SE can be used to investigate the radiation damage of semiconductors together with appropriate optical model construction which can be supported or independently checked by the channeling method. However, in case of low level damage (consisting mainly of isolated point defects) ellipsometry can give false results, overestimating the damage using inappropriate dielectric functions. In that case checking by other methods like channeling is desirable
Analysis of decays in the perturbative QCD approach
Within the framework of perturbative QCD approach, we study the charmless
two-body decays . Using the decays constants
and the light-cone distribution amplitudes for these mesons derived from the
QCD sum rule method, we find the following results: (a) Our predictions for the
branching ratios are consistent well with the QCDF results within errors, but
much larger than the naive factorization approach calculation values. (b) We
predict that the anomalous polarizations occurring in the decays also happen in the decays , while do not happen in
the decays . Here the contributions from the annihilation diagrams
play an important role to explain the lager transverse polarizations in the
decays , while they are not sensitive to the polarizations in
decays . (c) Our predictions for the direct CP-asymmetries agree
well with the QCDF results within errors. The decays have larger direct CP-asymmetries, which
could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with
arXiv:1203.5913, arXiv:1203.591
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Mixed Spices at Culinary Doses Have Prebiotic Effects in Healthy Adults: A Pilot Study.
Spices were used as food preservatives prior to the advent of refrigeration, suggesting the possibility of effects on microbiota. Previous studies have shown prebiotic activities in animals and in vitro, but there has not been a demonstration of prebiotic or postbiotic effects at culinary doses in humans. In this randomized placebo-controlled study, we determined in twenty-nine healthy adults the effects on the gut microbiota of the consumption daily of capsules containing 5 g of mixed spices at culinary doses by comparison to a matched control group consuming a maltodextrin placebo capsule. The 16S ribosomal RNA sequencing data were used for microbial characterization. Spice consumption resulted in a significant reduction in Firmicutes abundance (p < 0.033) and a trend of enrichment in Bacteroidetes (p < 0.097) compared to placebo group. Twenty-six operational taxonomic units (OTUs) were different between the spice and placebo groups after intervention. Furthermore, there was a significant negative correlation between fecal short-chain fatty acid propionate concentration and Firmicutes abundance in spice intervention group (p < 0.04). The production of individual fecal short-chain fatty acid was not significantly changed by spice consumption in this study. Mixed spices consumption significantly modified gut microbiota, suggesting a prebiotic effect of spice consumption at culinary doses
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