217 research outputs found
Dynamics of pollutant discharge in combined sewer systems during rain events: chance or determinism?
International audienceA large database of continuous flow and turbidity measurements cumulating data on hundreds of rain events and dry weather days from two sites in Paris (called Quais and Clichy) and one in Lyon (called Ecully) is presented. This database is used to characterize and compare the behaviour of the three sites at the inter-events scale. The analysis is probed through three various variables: total volumes and total suspended solids (TSS) masses and concentrations during both wet and dry weather periods in addition to the contributions of diverse-origin sources to event flow volume and TSS load values. The results obtained confirm the previous findings regarding the spatial consistency of TSS fluxes and concentrations between both sites in Paris having similar land uses. Moreover, masses and concentrations are proven to be correlated between Parisian sites in a way that implies the possibility of some deterministic processes being reproducible from one catchment to another for a particular rain event. The results also demonstrate the importance of the contribution of wastewater and sewer deposits to the total events' loads and show that such contributions are not specific to Paris sewer networks
Imaging magnetic polarons in the doped Fermi-Hubbard model
Polarons are among the most fundamental quasiparticles emerging in
interacting many-body systems, forming already at the level of a single mobile
dopant. In the context of the two-dimensional Fermi-Hubbard model, such
polarons are predicted to form around charged dopants in an antiferromagnetic
background in the low doping regime close to the Mott insulating state.
Macroscopic transport and spectroscopy measurements related to high
materials have yielded strong evidence for the existence of such quasiparticles
in these systems. Here we report the first microscopic observation of magnetic
polarons in a doped Fermi-Hubbard system, harnessing the full single-site spin
and density resolution of our ultracold-atom quantum simulator. We reveal the
dressing of mobile doublons by a local reduction and even sign reversal of
magnetic correlations, originating from the competition between kinetic and
magnetic energy in the system. The experimentally observed polaron signatures
are found to be consistent with an effective string model at finite
temperature. We demonstrate that delocalization of the doublon is a necessary
condition for polaron formation by contrasting this mobile setting to a
scenario where the doublon is pinned to a lattice site. Our work paves the way
towards probing interactions between polarons, which may lead to stripe
formation, as well as microscopically exploring the fate of polarons in the
pseudogap and bad metal phase
Gluon mass generation without seagull divergences
Dynamical gluon mass generation has been traditionally plagued with seagull
divergences, and all regularization procedures proposed over the years yield
finite but scheme-dependent gluon masses. In this work we show how such
divergences can be eliminated completely by virtue of a characteristic
identity, valid in dimensional regularization. The ability to trigger the
aforementioned identity hinges crucially on the particular Ansatz employed for
the three-gluon vertex entering into the Schwinger-Dyson equation governing the
gluon propagator. The use of the appropriate three-gluon vertex brings about an
additional advantage: one obtains two separate (but coupled) integral
equations, one for the effective charge and one for the gluon mass. This system
of integral equations has a unique solution, which unambiguously determines
these two quantities. Most notably, the effective charge freezes in the
infrared, and the gluon mass displays power-law running in the ultraviolet, in
agreement with earlier considerations.Comment: 37 pages, 9 figures; minor typos corrected and a few brief
explanatory remarks adde
On the connection between the pinch technique and the background field method
The connection between the pinch technique and the background field method is
further explored. We show by explicit calculations that the application of the
pinch technique in the framework of the background field method gives rise to
exactly the same results as in the linear renormalizable gauges. The general
method for extending the pinch technique to the case of Green's functions with
off-shell fermions as incoming particles is presented. As an example, the
one-loop gauge independent quark self-energy is constructed. We briefly discuss
the possibility that the gluonic Green's functions, obtained by either method,
correspond to physical quantities.Comment: 13 pages and 3 figures, all included in a uuencoded file, to appear
in Physical Review
Pinch Technique for Schwinger-Dyson equations
In the context of scalar QED we derive the pinch technique self-energies and
vertices directly from the Schwinger-Dyson equations. After reviewing the
perturbative construction, we discuss in detail the general methodology and the
basic field-theoretic ingredients necessary for the completion of this task.
The construction requires the simultaneous treatment of the equations governing
the scalar self-energy and the fundamental interaction vertices. The resulting
non-trivial rearrangement of terms generates dynamically the Schwinger-Dyson
equations for the corresponding Green's functions of the background field
method. The proof relies on the extensive use of the all-order Ward-identities
satisfied by the full vertices of the theory and by the
one-particle-irreducible kernels appearing in the usual skeleton expansion. The
Ward identities for these latter quantities are derived formally, and several
subtleties related to the structure of the multiparticle kernels are addressed.
The general strategy for the generalization of the method in a non-Abelian
context is briefly outlined, and some of the technical difficulties are
discussed.Comment: 43 pages, 11 figures; title and abstract slightly modified, several
clarifying discussions added; final version to match the one accpted for
publication in JHE
Displacement Operator Formalism for Renormalization and Gauge Dependence to All Orders
We present a new method for determining the renormalization of Green
functions to all orders in perturbation theory, which we call the displacement
operator formalism, or the D-formalism, in short. This formalism exploits the
fact that the renormalized Green functions may be calculated by displacing by
an infinite amount the renormalized fields and parameters of the theory with
respect to the unrenormalized ones. With the help of this formalism, we are
able to obtain the precise form of the deformations induced to the Nielsen
identities after renormalization, and thus derive the exact dependence of the
renormalized Green functions on the renormalized gauge-fixing parameter to all
orders. As a particular non-trivial example, we calculate the gauge-dependence
of at two loops in the framework of an Abelian Higgs model, using a
gauge-fixing scheme that preserves the Higgs-boson low-energy theorem for
off-shell Green functions. Various possible applications and future directions
are briefly discussed.Comment: 41 pages, 8 figure
A Pilot Study on effects of vaccination on immunity of broiler chickens
A pilot study was carried out with the aim of highlighting the effects of NDV vaccine on the immune responses of broiler chickens challenged with NDV. Twenty (20) broilers of day-old were used for the study. They were grouped into five of four per group. During the study they were fed with standard feeds and clean water ad libitum. Both vaccinated and unvaccinated groups were challenged with 0.2 saline suspension of 106 ELD50 intradermal inoculation of NDV challenged strain. The vaccinated groups showed neither clinical signs nor symptoms of NDV infections while unvaccinated group showed 100% mortality after 48hr. This result indicate that vaccines is still very important in the prevention, management and control of poultry diseases as maternal immunity passed on to the young chicks at precocial stage could not be relied on to fight against infectious disease in broiler chickens. Therefore, the use of locally produced vaccines should be encouraged among farmers for the prevention, control and management of outbreaks of viral infections in our community. Key: Challenged, Poultry birds- broilers, Newcastle disease virus, Vaccinatio
CP violation through particle mixing and the H-A lineshape
We consider the possibility of looking for CP-mixing effects in two-Higgs
doublet models (and particularly in the MSSM) by studying the lineshape of the
CP-even (H) and CP-odd (A) neutral scalars. In most cases H and A come quite
degenerate in mass, and their s-channel production would lead to nearly
overlapping resonances. CP-violating effects may connect these two Higgs
bosons, giving origin to one-loop particle mixing, which, due to their mass
proximity, can be resonantly enhanced. The corresponding transition amplitude
contains then CP-even and CP-odd components; besides the signal of
intereference between both amplitudes, leading to a CP-odd asymmetry, we
propose to look for the mixing probability itself, a quantity which, although
CP-even, can originate only from a CP-odd amplitude. We show that, in general,
the effect of such a mixing probability cannot be mimicked by (or be
re-absorbed into) a simple redefinition of the H and A masses in the context of
a CP-conserving model. Specifically, the effects of the CP-mixing are such
that, either the mass-splitting of the H and A bosons cannot be accounted for
in the absence of CP-mixing, and/or the detailed energy dependence of the
produced lineshape is clearly different from the one obtained by redefining the
masses, but not allowing any mixing. This analysis suggests that the detailed
study of the lineshape of this Higgs system may provide valuable information on
the CP nature of the underlying theory.Comment: 16 pages, 13 figures; v2: added one reference; v3: radiative
corrections taken into account, agreement now with CP-SuperH, conclusions
unchanged. v3 matches the paper version accepted for publication in JHE
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