Belief-Propagation for Weighted b-Matchings on Arbitrary Graphs and its Relation to Linear Programs with Integer Solutions

We consider the general problem of finding the minimum weight \bm-matching on arbitrary graphs. We prove that, whenever the linear programming (LP) relaxation of the problem has no fractional solutions, then the belief propagation (BP) algorithm converges to the correct solution. We also show that when the LP relaxation has a fractional solution then the BP algorithm can be used to solve the LP relaxation. Our proof is based on the notion of graph covers and extends the analysis of (Bayati-Shah-Sharma 2005 and Huang-Jebara 2007}. These results are notable in the following regards: (1) It is one of a very small number of proofs showing correctness of BP without any constraint on the graph structure. (2) Variants of the proof work for both synchronous and asynchronous BP; it is the first proof of convergence and correctness of an asynchronous BP algorithm for a combinatorial optimization problem.Comment: 28 pages, 2 figures. Submitted to SIAM journal on Discrete Mathematics on March 19, 2009; accepted for publication (in revised form) August 30, 2010; published electronically July 1, 201

Self-Consistent Random Phase Approximation - Application to the Hubbard Model for finite number of sites

Within the 1D Hubbard model linear closed chains with various numbers of sites are considered in Self Consistent Random Phase Approximation (SCRPA). Excellent results with a minimal numerical effort are obtained for 2+4n sites cases, confirming earlier results with this theory for other models. However, the 4n sites cases need further considerations. SCRPA solves the two sites problem exactly. It therefore contains the two electrons and high density Fermi gas limits correctly.Comment: 17 pages, 17 figure

Hybrid multi-independent mmWave MNOs assessment utilising spectrum sharing paradigm for 5G networks

Spectrum sharing paradigm (SSP) has recently emerged as an attractive solution to provide capital expenditure (CapEx) and operating expenditure (OpEx) savings and to enhance spectrum utilization (SU). However, practical issues concerning the implementation of such paradigm are rarely addressed (e.g., mutual interference, fairness, and mmWave base station density). Therefore, in this paper, we proposed ultra-reliable and proportionally fair hybrid spectrum sharing access strategy that aims to address the aforementioned aspects as a function of coverage probability (CP), average rate distributions (ARD), and the number of mmWave base stations (mBSs). In this strategy, the spectrum is sliced into three parts (exclusive, semi-pooled, and fully pooled). A typical user that belongs to certain operator has the right to occupy a part of the spectrum available in the high and low frequencies (28 and 73 GHz) based on an adaptive multi-state mmWave cell selection scheme (AMMC-S) which associates the user with the tagged mBS that offers a highest SINR to maintain more reliable connection and enrich the user experience. Numerical results show that significant improvement in terms of ARD, CP, fairness among operators, and maintain an acceptable level of mBSs density

Energy-efficient user association mechanism enabling fully hybrid spectrum sharing among multiple 5G cellular operators

Spectrum sharing (SS) is a promising solution to enhance spectrum utilization in future cellular systems. Reducing the energy consumption in cellular networks has recently earned tremendous attention from diverse stakeholders (i.e., vendors, mobile network operators (MNOs), and government) to decrease the CO2 emissions and thus introducing an environment-friendly wireless communication. Therefore, in this paper, joint energy-efficient user association (UA) mechanism and fully hybrid spectrum sharing (EE-FHSS) approach is proposed considering the quality of experience QoE (i.e., data rate) as the main constraint. In this approach, the spectrum available in the high and low frequencies (28 and 73 GHz) is sliced into three portions (licensed, semi-shared, and fully-shared) aims to serve the users (UEs) that belong to four operators in an integrated and hybrid manner. The performance of the proposed QoE-Based EE UA-FHSS is compared with the well-known maximum signal-to-interference-plus-noise ratio (max-SINR UA-FHSS). Numerical results show that remarkable enhancement in terms of EE for the four participating operators can be achieved while maintaining a high degree of QoE to the UEs

DBI in the Sky

We analyze the spectrum of density perturbations generated in models of the recently discovered "D-cceleration" mechanism of inflation. In this scenario, strong coupling quantum field theoretic effects sum to provide a DBI-like action for the inflaton. We show that the model has a strict lower bound on the non-Gaussianity of the CMBR power spectrum at an observable level, and is thus falsifiable. This in particular observationally distinguishes this mechanism from traditional slow roll inflation generated by weakly interacting scalar fields. The model also favors a large observable tensor component to the CMBR spectrum.Comment: 30 pages latex. v2: references added. v3: correction in three point function. v4: sign of non-Gaussianity corrected; fNL is negativ

Enhancement of boresight radiation for leaky wave antenna array

An array of half-width microstrip leaky-wave antennas (HW-MLWAs) of two uniform elements was designed to obtain maximum boresight radiation. Achieve this, two uniform of HW-MLWAs are placed at 180◦ and fed by a probe located at the center between the elements, two uniforms of HW-MLWAs, loaded terminated by 50Ω lumped element. Two beams from two branches individual merge to form the resultant directive beam. The simulation represents the susceptibility of the proposed array of uniform HW-MLWAs to the radiation broadside direction effectively. The predict bandwidth matched of the array is 582 MHz (4.18–4.76 GHz). The direction of its main beam in boresight happens over a wide 13%, relatively (4.18-4.76 GHz) band. The proposed peak gain at the boresight direction of the array is 9.91 dBi

On R**2 Corrections for 5D Black Holes

We study higher order corrections to extremal black holes/black string in five dimensions. These higher order corrections are due to supersymmetric completion of R**2 term in five dimensions. By making use of the results we extend the notion of very special geometry when higher derivative terms are also taken into account. This can be used to make a connection between total bundle space of near horizon wrapped M2's and wrapped M5's in the presence of higher order corrections. We also show how the corrected geometry removes the singularity of a small black hole.Comment: 16 pages, latex file, V3: typos corrected, refs added, V4; minor corrections, few comments added, refs adde

Electronically controlled radiation pattern leaky wave antenna array for (C band) application

This paper provides an insight of a new, leaky-wave antenna (LWA) array. It holds the ability to digitally steer its beam at a fixed frequency by utilizing only two state of bias voltage. This is done with acceptable impedance matching while scanning and very little gain variation. Investigation is carried out on LWAs’ control radiation pattern in steps at a fixed frequency via PIN diodes switches. This study also presents a novel half-width microstrip LWA (HWMLWA) array. The antenna is made up of the following basic structures: two elements and reconfigurable control cell with each being comprised of two diodes and two triangle patches. A double gap capacitor in each unit cell is independently disconnected or connected via PIN diode switch to achieve fixed-frequency control radiation pattern. The reactance profile at the microstrip’s free edge and thus the main beam direction is changed once the control-cell states are changed. The main beam may be directed by the antenna between 61o and 19o at 4.2 GHz. C band achieved the measured peak gain of the antenna of 15 dBi at 4.2 GHz beam scanning range

Spin Fidelity for Three-qubit Greenberger-Horne-Zeilinger and W States Under Lorentz Transformations

Constructing the reduced density matrix for a system of three massive spin$-\frac{1}{2}$ particles described by a wave packet with Gaussian momentum distribution and a spin part in the form of GHZ or W state, the fidelity for the spin part of the system is investigated from the viewpoint of moving observers in the jargon of special relativity. Using a numerical approach, it turns out that by increasing the boost speed, the spin fidelity decreases and reaches to a non-zero asymptotic value that depends on the momentum distribution and the amount of momentum entanglement.Comment: 12pages, 2 figure

The potential use of service-oriented infrastructure framework to enable transparent vertical scalability of cloud computing infrastructure

Cloud computing technology has become familiar to most Internet users. Subsequently, there has been an increased growth in the use of cloud computing, including Infrastructure as a Service (IaaS). To ensure that IaaS can easily meet the growing demand, IaaS providers usually increase the capacity of their facilities in a vertical IaaS increase capability and the capacity for local IaaS amenities such as increasing the number of servers, storage and network bandwidth. However, at the same time, horizontal scalability is sometimes not enough and requires additional strategies to ensure that the large number of IaaS service requests can be met. Therefore, strategies requiring horizontal scalability are more complex than the vertical scalability strategies because they involve the interaction of more than one facility at different service centers. To reduce the complexity of the implementation of the horizontal scalability of the IaaS infrastructures, the use of a technology service oriented infrastructure is recommended to ensure that the interaction between two or more different service centers can be done more simply and easily even though it is likely to involve a wide range of communication technologies and different cloud computing management. This is because the service oriented infrastructure acts as a middle man that translates and processes interactions and protocols of different cloud computing infrastructures without the modification of the complex to ensure horizontal scalability can be run easily and smoothly. This paper presents the potential of using a service-oriented infrastructure framework to enable transparent vertical scalability of cloud computing infrastructures by adapting three projects in this research: SLA@SOI consortium, Open Cloud Computing Interface (OCCI), and OpenStack