7,656 research outputs found
Plasmon-exciton polaritons in 2D semiconductor/metal interfaces
The realization and control of polaritons is of paramount importance in the
prospect of novel photonic devices. Here, we investigate the emergence of
plasmon-exciton polaritons in hybrid structures consisting of a two-dimensional
(2D) transition metal dichalcogenide (TMDC) deposited onto a metal substrate or
coating a metallic thin-film. We determine the polaritonic spectrum and show
that, in the former case, the addition of a top dielectric layer, and, in the
latter, the thickness of the metal film,can be used to tune and promote
plasmon-exciton interactions well within the strong coupling regime. Our
results demonstrate that Rabi splittings exceeding 100 meV can be readily
achieved in planar dielectric/TMDC/metal structures under ambient conditions.
We thus believe that this work provides a simple and intuitive picture to
tailor strong coupling in plexcitonics, with potential applications for
engineering compact photonic devices with tunable optical properties.Comment: 6 pages, including 5 figures and reference
Integrability of the Minimal Strain Equations for the Lapse and Shift in 3+1 Numerical Relativity
Brady, Creighton and Thorne have argued that, in numerical relativity
simulations of the inspiral of binary black holes, if one uses lapse and shift
functions satisfying the ``minimal strain equations'' (MSE), then the
coordinates might be kept co-rotating, the metric components would then evolve
on the very slow inspiral timescale, and the computational demands would thus
be far smaller than for more conventional slicing choices. In this paper, we
derive simple, testable criteria for the MSE to be strongly elliptic, thereby
guaranteeing the existence and uniqueness of the solution to the Dirichlet
boundary value problem. We show that these criteria are satisfied in a test-bed
metric for inspiraling binaries, and we argue that they should be satisfied
quite generally for inspiraling binaries. If the local existence and uniqueness
that we have proved holds globally, then, for appropriate boundary values, the
solution of the MSE exhibited by Brady et. al. (which tracks the inspiral and
keeps the metric evolving slowly) will be the unique solution and thus should
be reproduced by (sufficiently accurate and stable) numerical integrations.Comment: 6 pages; RevTeX; submitted to Phys. Rev. D15. Technical issue of the
uniqueness of the solution to the Dirichlet problem clarified. New subsection
on the nature of the boundary dat
Software-defined networking: guidelines for experimentation and validation in large-scale real world scenarios
Part 1: IIVC WorkshopInternational audienceThis article thoroughly details large-scale real world experiments using Software-Defined Networking in the testbed setup. More precisely, it provides a description of the foundation technology behind these experiments, which in turn is focused around OpenFlow and on the OFELIA testbed. In this testbed preliminary experiments were performed in order to tune up settings and procedures, analysing the encountered problems and their respective solutions. A methodology consisting of five large-scale experiments is proposed in order to properly validate and improve the evaluation techniques used in OpenFlow scenarios
Mitochondria: role in ischemia, reperfusion and cell death
Recent advances in the knowledge of the biochemical basis of myocardial ischemia have enabled a better understanding of the complex sequence of events occurring in ischemic cardiomyopathy, whatever its manifestations. This has clearly highlighted the important role played by cardiac mitochondria in these events. At first only associated with energy production, mitochondria have been clearly shown to have other important functions, like the maintenance of calcium homeostasis, as well as ischemic and non-ischemic preconditioning, and also modulation of cellular life and death. The aims of this review are twofold: firstly, to review the current knowledge on mitochondrial morphology and structure, and how these can be affected by ischemia and ischemia-reperfusion; and secondly, to summarize the role of cardiac mitochondria in cardioprotection and modulation of cell death mechanisms
AN EXERGY COST ANALYSIS OF A COGENERATION PLANT
The exergy analysis, including the calculation of the unit exergetic cost of all flows of the cogeneration plant, was the main purpose of the thermoeconomic analysis of the STAG (STeam And Gas) combined cycle CHP (Combined Heat and Power) plant. The combined cycle cogeneration plant is composed of a GE10 gas turbine (11250 kW) coupled with a HRSG (Heat Recovery Steam Generator) and a condensing extraction steam turbine. The GateCycleTM Software was used for the modeling and simulation of the combined cycle CHP plant thermal scheme, and calculation of the thermodynamic properties of each flow (Mass Flow, Pressure, Temperature, Enthalpy). The entropy values for water and steam were obtained from the Steam Tab software while the entropy and exergy of the exhaust gases were calculated as instructed by. For the calculation of the unit exergetic cost was used the neguentropy and Structural Theory of Thermoeconomic. The GateCycleTM calculations results were exported to an Excel sheet to carry out the exergy analysis and the unit exergetic cost calculations with the thermoeconomic model that was created for matrix inversion solution. Several simulations were performed varying separately five important parameters: the Steam turbine exhaust pressure, the evaporator pinch point temperature, the steam turbine inlet temperature, Rankine cycle operating pressure and the stack gas temperature to determine their impact in the recovery cycle heat exchangers transfer area, power generation and unit exergetic cost
Quantum transitions of the XY model with long-range interactions on the inhomogenous periodic chain
The isotropic XY model in a transverse field, with uniform
long-range interactions among the transverse components of the spins, on the
inhomogeneous periodic chain, is studied. The model, composed of segments
with different exchange interactions and magnetic moments, is exactly
solved by introducing the integral gaussian transformation and the generalized
Jordan-Wigner transformation, which reduce the problem to the diagonalization
of a finite matrix of th order. The quantum transitions induced by the
transverse field are determined by analyzing the induced magnetization of the
cell and the equation of state. The phase diagrams for the quantum transitions,
in the space generated by the transverse field and the interaction parameters,
are presented. As expected, the model presents multiple, first- and
second-order quantum transitions induced by the transverse field, and it
corresponds to an extension of the models recently considered by the authors.
Detailed results are also presented, at T=0, for the induced magnetization and
isothermal susceptibility as function of the transverse field.Comment: 24 pages, 11 figures, accepted for publication in Physical Review
Enhancement of prompt photons in ultrarelativistic proton-proton collisions from nonlinear gluon evolution at small-
In this paper we estimate the influence of nonlinear gluon evolution in the
production of prompt photons at the LHC pp collider. We assume the validity of
collinear factorization and consider the EHKQS parton distributions, which are
solutions of the GLR-MQ evolution equations and describe quite well the DESY
HERA data, as input in our calculations. We find that both single and
double photon production are enhanced for low- photons and central
rapidities, while this effect is absent for the high- photons. The
implications of this effect for the Quark-Gluon Plasma searches and for the QCD
background to Higgs are also discussed.Comment: 4 pages, 4 figures. Version to be published in Physical Review
Ranking and clustering of nodes in networks with smart teleportation
Random teleportation is a necessary evil for ranking and clustering directed
networks based on random walks. Teleportation enables ergodic solutions, but
the solutions must necessarily depend on the exact implementation and
parametrization of the teleportation. For example, in the commonly used
PageRank algorithm, the teleportation rate must trade off a heavily biased
solution with a uniform solution. Here we show that teleportation to links
rather than nodes enables a much smoother trade-off and effectively more robust
results. We also show that, by not recording the teleportation steps of the
random walker, we can further reduce the effect of teleportation with dramatic
effects on clustering.Comment: 10 pages, 7 figure
Nuclear shadowing from exclusive quarkonium photoproduction at the BNL RHIC and CERN LHC
The photonuclear production of vector mesons in ultraperipheral heavy ion
collisions is investigated within the collinear approach using different
parameterizations for the nuclear gluon distribution. The integrated cross
section and the rapidity distribution for the () process are computed for energies of RHIC and LHC. A comparison with
the recent PHENIX data on coherent production of mesons is also
presented. We demonstrate that the study of the exclusive quarkonium
photoproduction can be used to constrain the nuclear effects in the gluon
distribution.Comment: 8 pages, 4 figures, 2 tables. Version to be published in Physical
Review
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