3,427 research outputs found
Generalized Jacobi Elliptic One-Monopole - Type A
We present new classical generalized one-monopole solution of the SU(2)
Yang-Mills-Higgs theory with the Higgs field in the adjoint representation. We
show that this generalized solution with -winding number and
-winding number is an axially symmetric Jacobi elliptic
generalization of the 't Hooft-Polyakov one-monopole. We construct this axially
symmetric one-monopole solution by generalizing the large distance asymptotic
solution of the 't Hooft-Polyakov one-monopole to the Jacobi elliptic functions
and solving the second order equations of motion numerically when the Higgs
potential is vanishing and non vanishing. These solutions are regular non-BPS
finite energy solutions.Comment: 17 pages, 5 figure
Gluon confinement criterion in QCD
We fix exactly and uniquely the infrared structure of the full gluon
propagator in QCD, not solving explicitly the corresponding dynamical equation
of motion. By construction, this structure is an infinite sum over all possible
severe (i.e., more singular than ) infrared singularities. It reflects
the zero momentum modes enhancement effect in the true QCD vacuum, which is due
to the self-interaction of massless gluons. It existence automatically exhibits
a characteristic mass (the so-called mass gap). It is responsible for the scale
of nonperturbative dynamics in the true QCD ground state. The theory of
distributions, complemented by the dimensional regularization method, allows
one to put the severe infrared singularities under the firm mathematical
control. By an infrared renormalization of a mass gap only, the infrared
structure of the full gluon propagator is exactly reduced to the simplest
severe infrared singularity, the famous . Thus we have exactly
established the interaction between quarks (concerning its pure gluon (i.e.,
nonlinear) contribution) up to its unimportant perturbative part. This also
makes it possible for the first time to formulate the gluon confinement
criterion and intrinsically nonperturbative phase in QCD in a manifestly
gauge-invariant ways.Comment: 10 pages, no figures, no tables. Typos corrected and the
clarification is intoduced. Shorten version to appear in Phys. Lett.
?Who am I to say?? Dutch care providers? evaluation of psychosocial vulnerability in pregnant women
Titan's atmosphere as observed by Cassini/VIMS solar occultations: CH, CO and evidence for CH absorption
We present an analysis of the VIMS solar occultations dataset, which allows
us to extract vertically resolved information on the characteristics of Titan's
atmosphere between 100-700 km with a characteristic vertical resolution of 10
km. After a series of data treatment procedures, 4 occultations out of 10 are
retained. This sample covers different seasons and latitudes of Titan. The
transmittances show clearly the evolution of the haze and detect the detached
layer at 310 km in Sept. 2011 at mid-northern latitudes. Through the inversion
of the transmission spectra with a line-by-line radiative transfer code we
retrieve the vertical distribution of CH and CO mixing ratio. The two
methane bands at 1.4 and 1.7 {\mu}m are always in good agreement and yield an
average stratospheric abundance of %. This is significantly less
than the value of 1.48% obtained by the GCMS/Huygens instrument. The analysis
of the residual spectra after the inversion shows that there are additional
absorptions which affect a great part of the VIMS wavelength range. We
attribute many of these additional bands to gaseous ethane, whose near-infrared
spectrum is not well modeled yet. Ethane contributes significantly to the
strong absorption between 3.2-3.5 {\mu}m that was previously attributed only to
C-H stretching bands from aerosols. Ethane bands may affect the surface windows
too, especially at 2.7 {\mu}m. Other residual bands are generated by stretching
modes of C-H, C-C and C-N bonds. In addition to the C-H stretch from aliphatic
hydrocarbons at 3.4 {\mu}m, we detect a strong and narrow absorption at 3.28
{\mu}m which we tentatively attribute to the presence of PAHs in the
stratosphere. C-C and C-N stretching bands are possibly present between 4.3-4.5
{\mu}m. Finally, we obtain the CO mixing ratio between 70-170 km. The average
result of ppm is in good agreement with previous studies.Comment: 51 pages, 28 figure
Differential atom interferometry beyond the standard quantum limit
We analyze methods to go beyond the standard quantum limit for a class of
atomic interferometers, where the quantity of interest is the difference of
phase shifts obtained by two independent atomic ensembles. An example is given
by an atomic Sagnac interferometer, where for two ensembles propagating in
opposite directions in the interferometer this phase difference encodes the
angular velocity of the experimental setup. We discuss methods of squeezing
separately or jointly observables of the two atomic ensembles, and compare in
detail advantages and drawbacks of such schemes. In particular we show that the
method of joint squeezing may improve the variance by up to a factor of 2. We
take into account fluctuations of the number of atoms in both the preparation
and the measurement stage, and obtain bounds on the difference of the numbers
of atoms in the two ensembles, as well as on the detection efficiency, which
have to be fulfilled in order to surpass the standard quantum limit. Under
realistic conditions, the performance of both schemes can be improved
significantly by reading out the phase difference via a quantum non-demolition
(QND) measurement. Finally, we discuss a scheme using macroscopically entangled
ensembles.Comment: 10 pages, 5 figures; eq. (3) corrected and other minor change
The apparent roughness of a sand surface blown by wind from an analytical model of saltation
We present an analytical model of aeolian sand transport. The model
quantifies the momentum transfer from the wind to the transported sand by
providing expressions for the thickness of the saltation layer and the apparent
surface roughness. These expressions are derived from basic physical principles
and a small number of assumptions. The model further predicts the sand
transport rate (mass flux) and the impact threshold (the smallest value of the
wind shear velocity at which saltation can be sustained). We show that, in
contrast to previous studies, the present model's predictions are in very good
agreement with a range of experiments, as well as with numerical simulations of
aeolian saltation. Because of its physical basis, we anticipate that our model
will find application in studies of aeolian sand transport on both Earth and
Mars
Agent-based homeostatic control for green energy in the smart grid
With dwindling non-renewable energy reserves and the adverse effects of climate change, the development of the smart electricity grid is seen as key to solving global energy security issues and to reducing carbon emissions. In this respect, there is a growing need to integrate renewable (or green) energy sources in the grid. However, the intermittency of these energy sources requires that demand must also be made more responsive to changes in supply, and a number of smart grid technologies are being developed, such as high-capacity batteries and smart meters for the home, to enable consumers to be more responsive to conditions on the grid in real-time. Traditional solutions based on these technologies, however, tend to ignore the fact that individual consumers will behave in such a way that best satisfies their own preferences to use or store energy (as opposed to that of the supplier or the grid operator). Hence, in practice, it is unclear how these solutions will cope with large numbers of consumers using their devices in this way. Against this background, in this paper, we develop novel control mechanisms based on the use of autonomous agents to better incorporate consumer preferences in managing demand. These agents, residing on consumers' smart meters, can both communicate with the grid and optimise their owner's energy consumption to satisfy their preferences. More specifically, we provide a novel control mechanism that models and controls a system comprising of a green energy supplier operating within the grid and a number of individual homes (each possibly owning a storage device). This control mechanism is based on the concept of homeostasis whereby control signals are sent to individual components of a system, based on their continuous feedback, in order to change their state so that the system may reach a stable equilibrium. Thus, we define a new carbon-based pricing mechanism for this green energy supplier that takes advantage of carbon-intensity signals available on the internet in order to provide real-time pricing. The pricing scheme is designed in such a way that it can be readily implemented using existing communication technologies and is easily understandable by consumers. Building upon this, we develop new control signals that the supplier can use to incentivise agents to shift demand (using their storage device) to times when green energy is available. Moreover, we show how these signals can be adapted according to changes in supply and to various degrees of penetration of storage in the system. We empirically evaluate our system and show that, when all homes are equipped with storage devices, the supplier can significantly reduce its reliance on other carbon-emitting power sources to cater for its own shortfalls. By so doing, the supplier reduces the carbon emission of the system by up to 25% while the consumer reduces its costs by up to 14.5%. Finally, we demonstrate that our homeostatic control mechanism is not sensitive to small prediction errors and the supplier is incentivised to accurately predict its green production to minimise costs
Photon number resolution using a time-multiplexed single-photon detector
Photon number resolving detectors are needed for a variety of applications
including linear-optics quantum computing. Here we describe the use of
time-multiplexing techniques that allows ordinary single photon detectors, such
as silicon avalanche photodiodes, to be used as photon number-resolving
detectors. The ability of such a detector to correctly measure the number of
photons for an incident number state is analyzed. The predicted results for an
incident coherent state are found to be in good agreement with the results of a
proof-of-principle experimental demonstration.Comment: REVTeX4, 6 pages, 8 eps figures, v2: minor changes, v3: changes in
response to referee report, appendix added, 1 reference adde
Genetic and Biochemical Characterization of the Oligopeptide Transport System of Lactococcus lactis
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