335 research outputs found
De Sitter Invariant Vacuum States, Vertex Operators, and Conformal Field Theory Correlators
We show that there is only one physically acceptable vacuum state for quantum
fields in de Sitter space-time which is left invariant under the action of the
de Sitter-Lorentz group and supply its physical interpretation in
terms of the Poincare invariant quantum field theory (QFT) on one dimension
higher Minkowski spacetime. We compute correlation functions of the generalized
vertex operator , where is a massless scalar
field, on the -dimensional de Sitter space and demonstrate that their
limiting values at timelike infinities on de Sitter space reproduce correlation
functions in -dimensional Euclidean conformal field theory (CFT) on
for scalar operators with arbitrary real conformal dimensions. We
also compute correlation functions for a vertex operator on
the \L obaczewski space and find that they also reproduce correlation functions
of the same CFT. The massless field is the nonlocal transform of
the massless field on de Sitter space introduced by one of us.Comment: 14 pages, LaTeX file We thank Roman Jackiw for bringing to our
attention Ref. 1
Fragrance release profile from sonochemically prepared protein microsphere containers
Protein microspheres have been prepared by sonicating a mixture of pure fragrant oil (amyl acetate (AA)) with an aqueous protein (bovine serum albumin) solution. The prepared protein spheres are nano- to micrometer sized with an encapsulation efficiency of approx. 97% for the AA present on the surface and inside the BSA capsule. Containers were found stable for more than 6 months when stored sealed at 4 °C and 20 °C. For the release profile measurements, we used a simple, automated and direct method. We continuously weighed the encapsulated microspheres and measured the evaporation rates. The release profiles at 15 °C and 25 °C display two different evaporation rates. The higher rate is the sum of a few evaporation rates, including water molecules, while the slower rate is due to the evaporation of pure AA. The changes in the evaporation rates occur upon the collapse of the container. This event coincides with the full evaporation of water. For morphological characterization we dyed the AA with Nile red, and used SEM, ESEM, Cryo-SEM, light microscopy, and confocal laser scanning microscopy measurements
Robust optical clock transitions in trapped ions using dynamical decoupling
We present a novel method for engineering an optical clock transition that is robust agaiast external field fluctuations and is able to overcome limits resulting from field inhomogeneities. The technique is based on the application of continuous driving fields to form a pair of dressed states essentially free of all relevant shifts. Specifically, the clock transition is robust to magnetic field shifts, quadrupole and other tensor shifts, and amplitude fluctuations of the driving fields. The scheme is applicable to either a single ion or an ensemble ofions, and is relevant for several types of ions, such as 40Ca, Sr1", l38BiT and 176Lo". Taking a spherically symmetric Coulomb crystal formed by 400 40Ca+ ions as an example, we show through numerical simulations that the in homogeneous linewidth of teas of Hertz in such a crystal together with linear Zeeman shifts of order 10 MHz are reduced to form a linewidth of around 1 Hz. We estimate a two-order-of-magnitude reduction in averaging time compared tostate-of-the art single ion frequency references, assuming a probe laser fractional instability of 10~1 Furthermore, a statistical uncertainty reaching2.9 x 10"16 in 1 s is estimated for a cascaded clock scheme in which the dynamically decoupled Coulomb crystal clock stabilizes the interrogation laser for an 2/Al clock
Frateuria defendens reduces yellows disease symptoms in grapevine under field conditions
Yellows diseases in grapevine, associated with the presence of different phytoplasmas, are a major problem for growers, with no environmentally friendly means of control. Frateuria defendens (Frd), a bacterium with endophytic traits, has been shown to reduce yellows symptoms in grapevine plantlets under laboratory conditions. The objective of this study was to test whether similar effects could be achieved under field conditions. A trial was conducted in a heavily infected vineyard in northern Israel for two consecutive years. A suspension of Frd cells (108·mL-1) was applied bi-weekly by foliar spray on grapevines from bud burst to leaf senescence. Frd penetrated the leaves during the growing period but not during leaf senescence and could be detected in the leaves by PCR analysis up to 14 days post-spraying. The rate of yellows infection was lower in the treated grapevines compared to its increase in untreated grapevines and the yield of symptomatic plants was improved by 10 to 20 %. Taken together, the results suggest Frd acted as a biological control agent in vineyards under the experimental conditions tested
Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant
Let the reciprocal Newton 'constant' be an apparently non-dynamical
Brans-Dicke scalar field damped oscillating towards its General Relativistic
VEV. We show, without introducing additional matter fields or dust, that the
corresponding cosmological evolution averagely resembles, in the Jordan frame,
the familiar dark radiation -> dark matter -> dark energy domination sequence.
The fingerprints of our theory are fine ripples, hopefully testable, in the FRW
scale factor; they die away at the General Relativity limit. The possibility
that the Brans-Dicke scalar also serves as the inflaton is favorably examined.Comment: RevTex4, 12 pages, 5 figures; Minor revision, References adde
Negative quasiprobabilities enhance phase estimation in quantum-optics experiment
Operator noncommutation, a hallmark of quantum theory, limits measurement
precision, according to uncertainty principles. Wielded correctly, though,
noncommutation can boost precision. A recent foundational result relates a
metrological advantage with negative quasiprobabilities -- quantum extensions
of probabilities -- engendered by noncommuting operators. We crystallize the
relationship in an equation that we prove theoretically and observe
experimentally. Our proof-of-principle optical experiment features a filtering
technique that we term partially postselected amplification (PPA). Using PPA,
we measure a waveplate's birefringent phase. PPA amplifies, by over two orders
of magnitude, the information obtained about the phase per detected photon. In
principle, PPA can boost the information obtained from the average filtered
photon by an arbitrarily large factor. The filter's amplification of systematic
errors, we find, bounds the theoretically unlimited advantage in practice. PPA
can facilitate any phase measurement and mitigates challenges that scale with
trial number, such as proportional noise and detector saturation. By
quantifying PPA's metrological advantage with quasiprobabilities, we reveal
deep connections between quantum foundations and precision measurement.Comment: 5 pages, 4 figures in main text; 8 pages, 1 figure in appendice
Predominance of deterministic microbial community dynamics in salterns exposed to different light intensities
While the dynamics of microbial community assembly driven by environmental perturbations have been extensively studied, our understanding is far from complete, particularly for lightâinduced perturbations. Extremely halophilic communities thriving in coastal solar salterns are mainly influenced by two environmental factorsâsalt concentrations and high sunlight irradiation. By experimentally manipulating light intensity through the application of shading, we showed that light acts as a deterministic factor that ultimately drives the establishment of recurrent microbial communities under nearâsaturation salt concentrations. In particular, the stable and highly changeâresistant communities that established under highâlight intensities were dominated (>90% of metagenomic reads) by Haloquadratum spp. and Salinibacter spp. On the other hand, under 37âfold lower light intensity, different, less stable and changeâresistant communities were established, mainly dominated by yet unclassified haloarchaea and relatively diverse photosynthetic microorganisms. These communities harboured, in general, much lower carotenoid pigment content than their highâirradiation counterparts. Both assemblage types appeared to be highly resilient, reâestablishing when favourable conditions returned after perturbation (i.e. highâirradiation for the former communities and lowâirradiation for the latter ones). Overall, our results revealed that stochastic processes were of limited significance to explain these patterns.This study was funded by the Spanish Ministry of Economy projects CGL2012-39627-C03-03 CLG2015_66686-C3-1-P and PGC2018-096956-B-C41 (to R.R.M.), CGL2015_66686-C3-3-P (to J.A.) and CGL2015_66686-C3-2-P (to J.E.G.P.), which were also supported with European Regional Development Fund (FEDER) funds. R.A. was funded by the Max Planck Society. KTKâs research was supported, in part, by the U.S. National Science Foundation (Award No. 1831582). T.V.P. received a pre-doctoral fellowship (No. BES-2013-064420) from the Spanish Government Ministry for Finance and Competition. R.R.M. acknowledges the financial support of the sabbatical stay at Georgia Tech supported by the Grant PRX18/00048 of the Ministry of Sciences, Innovation and Universities
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