Roma Tre University

About: Roma Tre University is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 4434 authors who have published 15352 publications receiving 374888 citations. The organization is also known as: Universita degli Studi Roma Tre & RomaTre.

Coherent spin-networks

Abstract: In this paper we discuss a proposal of coherent states for loop quantum gravity. These states are labeled by a point in the phase space of general relativity as captured by a spin-network graph. They are defined as the gauge-invariant projection of a product over links of Hall's heat kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the spin-foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). These states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli.

Passenger demand oriented train scheduling and rolling stock circulation planning for an urban rail transit line

Abstract: We study the integration of train scheduling and rolling stock circulation planning under time-varying passenger demand for an urban rail transit line, where the practical train operation constraints, e.g., the capacity of trains, the number of available rolling stocks, and the entering/exiting depot operations, are considered. Three solution approaches are proposed to solve the resulting multi-objective mixed-integer nonlinear programming (MINLP) problem to deliver both an irregular train schedule (i.e., departure and arrival times of all train services) and a rolling stock circulation plan (including entering/exiting depot operations of rolling stocks and connections between train services) simultaneously. We first present an iterative nonlinear programming (INP) approach, where the solutions of the original MINLP problem are obtained by solving a nonlinear programming problem and a mixed integer linear programming (MILP) problem iteratively. Moreover, an equivalent MILP formulation of the original MINLP model is developed and an approximated MILP approach is proposed to reduce the number of constraints introduced by passenger demand. A case study is conducted based on the practical data of the Beijing Yizhuang line, where the three proposed approaches are compared with a state-of-the-art approach and a practical method used by the traffic planners. This comparison shows the effectiveness and efficiency of the three proposed approaches.

2D photonic crystal cavity-based WDM multiplexer

Abstract: We designed a multiport two-dimensional (2D) photonic crystal (PhC) multiplexer based on contra-directional coupling and standing-wave resonators. The device is composed of PhC filters with up to 12 cavities in the same micro-patterned structure: adjacent strips with different periods contain a single cavity, and by selecting the proper lattice constants we tune the dropped frequency of each cavity. Each filter has 1.16 nm bandwidth, at a central wavelength 1550 nm, and the channels are 10 nm spaced. The variations in the local lattice period are very small, and the mismatch between two adjacent structures does not affect the propagation of the beam in the bus channel. The PhC structure has been analyzed by using the plane wave expansion method and the device performance has been investigated with the finite-difference time-domain technique. The transmittance of each drop filter is about 74%, with a non-uniformity between channels less than 5%. The overall longitudinal dimension of the multiplexer is less than 20 μm.

Search for new phenomena in events with at least three photons collected in pp collisions at √s = 8 TeV with the ATLAS detector

Abstract: Results of a search for new phenomena in events with at least three photons are reported. Data from proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated lumi ...