12,828 research outputs found
A measure of tripartite entanglement in bosonic and fermionic systems
We describe an efficient theoretical criterion suitable for the evaluation of
the tripartite entanglement of any mixed three-boson or -fermion state, based
on the notion of the entanglement of particles for bipartite systems of
identical particles. Our approach allows one to quantify the accessible amount
of quantum correlations in the systems without any violation of the local
particle number superselection rule. A generalization of the tripartite
negativity is here applied to some correlated systems including the
continuous-time quantum walks of identical particles (both for bosons and
fermions) and compared with other criteria recently proposed in the literature.
Our results show the dependence of the entanglement dynamics upon the quantum
statistics: the bosonic bunching results into a low amount of quantum
correlations while Fermi-Dirac statistics allows for higher values of the
entanglement.Comment: 19 pages, 3 figure
Exciton-phonon scattering and photo-excitation dynamics in J-aggregate microcavities
We have developed a model accounting for the photo-excitation dynamics and
the photoluminescence of strongly coupled J-aggregate microcavities. Our model
is based on a description of the J-aggregate film as a disordered Frenkel
exciton system in which relaxation occurs due to the presence of a thermal bath
of molecular vibrations. In a strongly coupled microcavity exciton-polaritons
are formed, mixing superradiant excitons and cavity photons. The calculation of
the microcavity steady-state photoluminescence, following a CW non resonant
pumping, is carried out. The experimental photoluminescence intensity ratio
between upper and lower polariton branches is accurately reproduced. In
particular both thermal activation of the photoluminescence intensity ratio and
its Rabi splitting dependence are a consequence of the bottleneck in the
relaxation, occurring at the bottom of the excitonic reservoir. The effects due
to radiative channels of decay of excitons and to the presence of a
paritticular set of discrete optical molecular vibrations active in relaxation
processes are investigared.Comment: 8 pages, 6 figure
"All on short" prosthetic-implant supported rehabilitations
Objectives. Short implants are increasing their popularity among clinicians who want to fulfill the constant demanding of fixed prosthetic solutions in edentulous jaws. The aim of this report was to propose a new possibility to project and realize an occlusal guided implant cross-arch prosthesis supported by ultra-short implants, describing it presented an edentulous mandible case report. Methods. A 61-year-old, Caucasian, female patient who attended the dental clinic of the University of L’Aquila presented with edentulous posterior inferior jaw and periodontitis and periimplantitis processes in the anterior mandible. The remaining tooth and the affected implant were removed. Six 4-mm-long implants were placed to support a cross-arch metal-resin prosthesis. Results. At 1-year follow-up clinical and radiological assessment showed a good osseointegration of the fixtures and the patient was satisfied with the prosthesis solution. Conclusion. The method, even if it requires further validation, seems to be a valid aid in solving lower edentulous clinical cases, and appears less complex and with more indications of other proposals presented in the current clinical literature. Our case report differs from the current technique All-on-Four, which uses four implants in the mandible to support overdenture prosthesis, assuring a very promising clinical resul
Integrating the geodesic equations in the Schwarzschild and Kerr space-times using Beltrami's "geometrical" method
We revisit a little known theorem due to Beltrami, through which the
integration of the geodesic equations of a curved manifold is accomplished by a
method which, even if inspired by the Hamilton-Jacobi method, is purely
geometric. The application of this theorem to the Schwarzschild and Kerr
metrics leads straightforwardly to the general solution of their geodesic
equations. This way of dealing with the problem is, in our opinion, very much
in keeping with the geometric spirit of general relativity. In fact, thanks to
this theorem we can integrate the geodesic equations by a geometrical method
and then verify that the classical conservation laws follow from these
equations.Comment: 12 pages; corrected typos, journal-ref adde
First-principles study of multiferroic RbFe(MoO)
We have investigated the magnetic structure and ferroelectricity in
RbFe(MoO) via first-principles calculations. Phenomenological analyses
have shown that ferroelectricity may arise due to both the triangular chirality
of the magnetic structure, and through coupling between the magnetic helicity
and the ferroaxial structural distortion. Indeed, it was recently proposed that
the structural distortion plays a key role in stabilising the chiral magnetic
structure itself. We have determined the relative contribution of the two
mechanisms via \emph{ab-initio} calculations. Whilst the structural axiality
does induce the magnetic helix by modulating the symmetric exchange
interactions, the electric polarization is largely due to the in-plane spin
triangular chirality, with both electronic and ionic contributions being of
relativistic origin. At the microscopic level, we interpret the polarization as
a secondary steric consequence of the inverse Dzyaloshinskii-Moriya mechanism
and accordingly explain why the ferroaxial component of the electric
polarization must be small
Cardiac oxidative stress and inflammatory cytokines response after myocardial infarction
Oxidative stress in heart failure or during ischemia/reperfusion occurs as a result of the excessive generation or accumulation of free radicals or their oxidation products. Free radicals formed during oxidative stress can initiate lipid peroxidation, oxidize proteins to inactive states and cause DNA strand breaks. Oxidative stress is a condition in which oxidant metabolites exert toxic effects because of their increased production or an altered cellular mechanism of protection. In the early phase of acute heart ischemia cytokines have the feature to be functional pleiotropy and redundancy, moreover, several cytokines exert similar and overlapping actions on the same cell type and one cytokine shows a wide range of biological effects on various cell types. Activation of cytokine cascades in the infarcted myocardium was established in numerous studies. In experimental models of myocardial infarction, induction and release of the pro-inflammatory cytokines like TNF-&alpha (Tumor Necrosis Factor &alpha), IL-1&beta (Interleukin- 1&beta) and IL-6 (Interleukin-6) and chemokines are steadily described. The current review examines the role of oxidative stress and pro-inflammatory cytokines response following acute myocardial infarction and explores the inflammatory mechanisms of cardiac injur
Simplicial Chiral Models
Principal chiral models on a d-1 dimensional simplex are introduced and
studied analytically in the large limit. The and
models are explicitly solved. Relationship with standard lattice models and
with few-matrix systems in the double scaling limit are discussed.Comment: 6 pages, PHYZZ
Clarification of the Bootstrap Percolation Paradox
We study the onset of the bootstrap percolation transition as a model of
generalized dynamical arrest. We develop a new importance-sampling procedure in
simulation, based on rare events around "holes", that enables us to access
bootstrap lengths beyond those previously studied. By framing a new theory in
terms of paths or processes that lead to emptying of the lattice we are able to
develop systematic corrections to the existing theory, and compare them to
simulations. Thereby, for the first time in the literature, it is possible to
obtain credible comparisons between theory and simulation in the accessible
density range.Comment: 4 pages with 3 figure
Estimating the conditions for polariton condensation in organic thin-film microcavities
We examine the possibility of observing Bose condensation of a confined
two-dimensional polariton gas in an organic quantum well. We deduce a suitable
parameterization of a model Hamiltonian based upon the cavity geometry, the
biexciton binding energy, and similar spectroscopic and structural data. By
converting the sum-over-states to a semiclassical integration over
-dimensional phase space, we show that while an ideal 2-D Bose gas will not
undergo condensation, an interacting gas with the Bogoliubov dispersion
close to will undergo Bose condensation at a given
critical density and temperature. We show that is sensitive
to both the cavity geometry and to the biexciton binding energy. In particular,
for strongly bound biexcitons, the non-linear interaction term appearing in the
Gross-Pitaevskii equation becomes negative and the resulting ground state will
be a localized soliton state rather than a delocalized Bose condensate.Comment: 2 figure
Comparing P-stars with Observations
P-stars are compact stars made of up and down quarks in -equilibrium
with electrons in a chromomagnetic condensate. P-stars are able to account for
compact stars as well as stars with radius comparable with canonical neutron
stars. We compare p-stars with different available observations. Our results
indicate that p-stars are able to reproduce in a natural manner several
observations from isolated and binary pulsars.Comment: 15 pages, 2 figures; accepted for publication in Astrophysical
Journa
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