19,374 research outputs found
Information-disturbance tradeoff in quantum measurements
We present a simple information-disturbance tradeoff relation valid for any
general measurement apparatus: The disturbance between input and output states
is lower bounded by the information the apparatus provides in distinguishing
these two states.Comment: 4 Pages, 1 Figure. Published version (reference added and minor
changes performed
Anti-transpirant effects on vine physiology, berry and wine composition of cv. Aglianico (Vitis vinifera L.) Grown in South Italy
In viticulture, global warming requires reconsideration of current production models. At the base of this need there are some emerging phenomena: modification of phenological phases; acceleration of the maturation process of grapes, with significant increases in the concentration of sugar musts; decoupling between technological grape maturity and phenolic maturity. The aim of our study was to evaluate the effect of a natural anti-transpirant on grapevine physiology, berry, and wine composition of Aglianico cultivar. For two years, Aglianico vines were treated at veraison with the anti-transpirant Vapor Gard and compared with a control sprayed with only water. A bunch thinning was also applied to both treatments. The effectiveness of Vapor Gard were assessed through measurements of net photosynthesis and transpiration and analyzing the vegetative, productive and qualitative parameters. The results demonstrate that the application of antitranspirant reduced assimilation and transpiration rate, stomatal conductance, berry sugar accumulation, and wine alcohol content. No significant differences between treatments were observed for other berry and wine compositional parameters. This method may be a useful tool to reduce berry sugar content and to produce wines with a lower alcohol content
Sub-Heisenberg estimation strategies are ineffective
In interferometry, sub-Heisenberg strategies claim to achieve a phase
estimation error smaller than the inverse of the mean number of photons
employed (Heisenberg bound). Here we show that one can achieve a comparable
precision without performing any measurement, just using the large prior
information that sub-Heisenberg strategies require. For uniform prior (i.e. no
prior information), we prove that these strategies cannot achieve more than a
fixed gain of about 1.73 over Heisenberg-limited interferometry. Analogous
results hold for arbitrary single-mode prior distributions. These results
extend also beyond interferometry: the effective error in estimating any
parameter is lower bounded by a quantity proportional to the inverse
expectation value (above a ground state) of the generator of translations of
the parameter.Comment: 4 pages, 2 figures, revised version that was publishe
Robust strategies for lossy quantum interferometry
We give a simple multiround strategy that permits to beat the shot noise
limit when performing interferometric measurements even in the presence of
loss. In terms of the average photon number employed, our procedure can achieve
twice the sensitivity of conventional interferometric ones in the noiseless
case. In addition, it is more precise than the (recently proposed) optimal
two-mode strategy even in the presence of loss.Comment: 4 pages, 3 figure
Single-stage electrohydraulic servosystem for actuating on airflow valve with frequencies to 500 hertz
An airflow valve and its electrohydraulic actuation servosystem are described. The servosystem uses a high-power, single-stage servovalve to obtain a dynamic response beyond that of systems designed with conventional two-stage servovalves. The electrohydraulic servosystem is analyzed and the limitations imposed on system performance by such nonlinearities as signal saturations and power limitations are discussed. Descriptions of the mechanical design concepts and developmental considerations are included. Dynamic data, in the form of sweep-frequency test results, are presented and comparison with analytical results obtained with an analog computer model is made
No Fermionic Wigs for BPS Attractors in 5 Dimensions
We analyze the fermionic wigging of 1/2-BPS (electric) extremal black hole
attractors in N=2, D=5 ungauged Maxwell-Einstein supergravity theories, by
exploiting anti-Killing spinors supersymmetry transformations. Regardless of
the specific data of the real special geometry of the manifold defining the
scalars of the vector multiplets, and differently from the D=4 case, we find
that there are no corrections for the near--horizon attractor value of the
scalar fields; an analogous result also holds for 1/2-BPS (magnetic) extremal
black string. Thus, the attractor mechanism receives no fermionic corrections
in D=5 (at least in the BPS sector).Comment: 24 pages, LaTeX2
Where in the String Landscape is Quintessence
We argue that quintessence may reside in certain corners of the string
landscape. It arises as a linear combination of internal space components of
higher rank forms, which are axion-like at low energies, and may mix with
4-forms after compactification of the Chern-Simons terms to 4D due to internal
space fluxes. The mixing induces an effective mass term, with an action which
{\it preserves} the axion shift symmetry, breaking it spontaneously after the
background selection. With several axions, several 4-forms, and a low string
scale, as in one of the setups already invoked for dynamically explaining a
tiny residual vacuum energy in string theory, the 4D mass matrix generated by
random fluxes may have ultralight eigenmodes over the landscape, which are
quintessence. We illustrate how this works in simplest cases, and outline how
to get the lightest mass to be comparable to the Hubble scale now, . The shift symmetry protects the smallest mass from
perturbative corrections in field theory. Further, if the ultralight eigenmode
does not couple directly to any sector strongly coupled at a high scale, the
non-perturbative field theory corrections to its potential will also be
suppressed. Finally, if the compactification length is larger than the string
length by more than an order of magnitude, the gravitational corrections may
remain small too, even when the field value approaches .Comment: 8 pages RevTeX; added references, matches published versio
- …