3,218 research outputs found
Interplay of the volume and surface plasmons in the electron energy loss spectra of C
The results of a joint experimental and theoretical investigation of the C60
collective excitations in the process of inelastic scattering of electrons are
presented. The shape of the electron energy loss spectrum is observed to vary
when the scattering angle increases. This variation arising due to the electron
diffraction of the fullerene shell is described by a new theoretical model
which treats the fullerene as a spherical shell of a finite width and accounts
for the two modes of the surface plasmon and for the volume plasmon as well. It
is shown that at small angles, the inelastic scattering cross section is
determined mostly by the symmetric mode of the surface plasmon, while at larger
angles, the contributions of the antisymmetric surface plasmon and the volume
plasmon become prominent.Comment: 11 pages, 3 figure
Geometry and Dynamics of a Coupled 4D-2D Quantum Field Theory
Geometric and dynamical aspects of a coupled 4D-2D interacting quantum field
theory - the gauged nonAbelian vortex - are investigated. The fluctuations of
the internal 2D nonAbelian vortex zeromodes excite the massless 4D Yang-Mills
modes and in general give rise to divergent energies. This means that the
well-known 2D CP(N-1) zeromodes associated with a nonAbelian vortex become
nonnormalizable. Moreover, all sorts of global, topological 4D effects such as
the nonAbelian Aharonov-Bohm effect come into play. These topological global
features and the dynamical properties associated with the fluctuation of the 2D
vortex moduli modes are intimately correlated, as shown concretely here in a
U(1) x SU(N) x SU(N) model with scalar fields in a bifundamental representation
of the two SU(N) factor gauge groups.Comment: Latex, 39 pages, 5 figure
Interplay of post collision interaction and photoelectron recapture in the near threshold inner shell ionization of rare gases
The Ar 2p?11/2 n?, Kr 3d1/2?1 n? and Xe 4d?11/2 n? resonances have been photoexcited and the angular distributions of the low energy electrons ejected in the autoionistaion to the lower spin orbit component of the respective ions have been measured. The observed lineshapes can be described by a combination of the post-collision interaction effects and the electron recapture probability in the very near threshold region
A 2-year point-prevalence surveillance of healthcare-associated infections and antimicrobial use in Ferrara University Hospital, Italy
Background: Healthcare-Associated Infections (HAIs) represent one of the leading issues to patient safety as well as a significant economic burden. Similarly, Antimicrobial Use (AMU) and Resistance (AMR) represent a growing threat to global public health and the sustainability of healthcare services. Methods: A Point Prevalence Survey (PPS) following the 2016 ECDC protocol for HAI prevalence and AMU was conducted at Ferrara University Hospital (FUH). Data were collected by a team of trained independent surveyors in 2016 and 2018. Risk factors independently associated with HAI were assessed by a multivariate logistic regression model. Results: Of the 1102 patients surveyed, 115 (10.4%) had an active HAI and 487 (44.2%) were on at least 1 systemic antimicrobial agent. Factors independently associated with increased HAI risk were a "Rapidly Fatal" McCabe score (expected fatal outcome within 1 year), presence of medical devices (PVC, CVC, indwelling urinary catheter or mechanically assisted ventilation) and a length of hospital stay of at least 1 week. The most frequent types of HAI were pneumonia, bloodstream infections, and urinary tract infections. Antimicrobial resistance to third-generation cephalosporins was observed in about 60% of Enterobacteriaceae. Conclusions: The survey reports a high prevalence of HAI and AMU in FUH. Repeated PPSs are useful to control HAIs and AMU in large acute-care hospitals, highlighting the main problematic factors and allowing planning for improvement actions
Formalism of collective electron excitations in fullerenes
We present a detailed formalism for the description of collective electron
excitations in fullerenes in the process of the electron inelastic scattering.
Considering the system as a spherical shell of a finite width, we show that the
differential cross section is defined by three plasmon excitations, namely two
coupled modes of the surface plasmon and the volume plasmon. The interplay of
the three plasmons appears due to the electron diffraction of the fullerene
shell. Plasmon modes of different angular momenta provide dominating
contributions to the differential cross section depending on the transferred
momentum.Comment: 11 pages, 2 figures; submitted to the special issue "Atomic Cluster
Collisions: Structure and Dynamics from the Nuclear to the Biological Scale"
of Eur. Phys. J.
Magnetothermodynamics of BPS baby skyrmions
The magnetothermodynamics of skyrmion type matter described by the gauged BPS
baby Skyrme model at zero temperature is investigated. We prove that the BPS
property of the model is preserved also for boundary conditions corresponding
to an asymptotically constant magnetic field. The BPS bound and the
corresponding BPS equations saturating the bound are found. Further, we show
that one may introduce pressure in the gauged model by a redefinition of the
superpotential. Interestingly, this is related to non-extremal type solutions
in the so-called fake supersymmetry method. Finally, we compute the equation of
state of magnetized BSP baby skyrmions inserted into an external constant
magnetic field and under external pressure , i.e., , where
is the "volume" (area) occupied by the skyrmions. We show that the BPS baby
skyrmions form a ferromagnetic medium.Comment: Latex, 39 pages, 14 figures. v2: New results and references added,
physical interpretation partly change
The Conformal Anomaly of M5-Branes
We show that the conformal anomaly for N M5-branes grows like . The
method we employ relates Coulomb branch interactions in six dimensions to
interactions in four dimensions using supersymmetry. This leads to a relation
between the six-dimensional conformal anomaly and the conformal anomaly of N=4
Yang-Mills. Along the way, we determine the structure of the four derivative
interactions for the toroidally compactified (2,0) theory, while encountering
interesting novelties in the structure of the six derivative interactions.Comment: 38 pages, LaTeX; references adde
Determinant and Weyl anomaly of Dirac operator: a holographic derivation
We present a holographic formula relating functional determinants: the
fermion determinant in the one-loop effective action of bulk spinors in an
asymptotically locally AdS background, and the determinant of the two-point
function of the dual operator at the conformal boundary. The formula originates
from AdS/CFT heuristics that map a quantum contribution in the bulk partition
function to a subleading large-N contribution in the boundary partition
function. We use this holographic picture to address questions in spectral
theory and conformal geometry. As an instance, we compute the type-A Weyl
anomaly and the determinant of the iterated Dirac operator on round spheres,
express the latter in terms of Barnes' multiple gamma function and gain insight
into a conjecture by B\"ar and Schopka.Comment: 11 pages; new comments and references added, typos correcte
Proceedings of the Workshop on Monte Carlo's, Physics and Simulations at the LHC PART II
These proceedings collect the presentations given at the first three meetings
of the INFN "Workshop on Monte Carlo's, Physics and Simulations at the LHC",
held at the Frascati National Laboratories in 2006. The first part of these
proceedings contains pedagogical introductions to several basic topics of both
theoretical and experimental high pT LHC physics. The second part collects more
specialised presentations.Comment: 157 pages, 136 figures; contribution by M. Grazzini has been adde
Solitons in the Higgs phase -- the moduli matrix approach --
We review our recent work on solitons in the Higgs phase. We use U(N_C) gauge
theory with N_F Higgs scalar fields in the fundamental representation, which
can be extended to possess eight supercharges. We propose the moduli matrix as
a fundamental tool to exhaust all BPS solutions, and to characterize all
possible moduli parameters. Moduli spaces of domain walls (kinks) and vortices,
which are the only elementary solitons in the Higgs phase, are found in terms
of the moduli matrix. Stable monopoles and instantons can exist in the Higgs
phase if they are attached by vortices to form composite solitons. The moduli
spaces of these composite solitons are also worked out in terms of the moduli
matrix. Webs of walls can also be formed with characteristic difference between
Abelian and non-Abelian gauge theories. We characterize the total moduli space
of these elementary as well as composite solitons. Effective Lagrangians are
constructed on walls and vortices in a compact form. We also present several
new results on interactions of various solitons, such as monopoles, vortices,
and walls. Review parts contain our works on domain walls (hep-th/0404198,
hep-th/0405194, hep-th/0412024, hep-th/0503033, hep-th/0505136), vortices
(hep-th/0511088, hep-th/0601181), domain wall webs (hep-th/0506135,
hep-th/0508241, hep-th/0509127), monopole-vortex-wall systems (hep-th/0405129,
hep-th/0501207), instanton-vortex systems (hep-th/0412048), effective
Lagrangian on walls and vortices (hep-th/0602289), classification of BPS
equations (hep-th/0506257), and Skyrmions (hep-th/0508130).Comment: 89 pages, 33 figures, invited review article to Journal of Physics A:
Mathematical and General, v3: typos corrected, references added, the
published versio
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