Renormalization group approach to spinor Bose-Fermi mixtures in a shallow optical lattice

We study a mixture of ultracold spin-half fermionic and spin-one bosonic atoms in a shallow optical lattice where the bosons are coupled to the fermions via both density-density and spin-spin interactions. We consider the parameter regime where the bosons are in a superfluid ground state, integrate them out, and obtain an effective action for the fermions. We carry out a renormalization group analysis of this effective fermionic action at low temperatures, show that the presence of the spinor bosons may lead to a separation of Fermi surfaces of the spin-up and spin-down fermions, and investigate the parameter range where this phenomenon occurs. We also calculate the susceptibilities corresponding to the possible superfluid instabilities of the fermions and obtain their possible broken-symmetry ground states at low temperatures and weak interactions.Comment: 8 pages, 8 figs v

Spin injection into a metal from a topological insulator

We study a junction of a topological insulator with a thin two-dimensional (2D) non-magnetic or partially polarized ferromagnetic metallic film deposited on a 3D insulator. We show that such a junction leads to a finite spin current injection into the film whose magnitude can be controlled by tuning a voltage $V$ applied across the junction. For ferromagnetic films, the direction of the component of the spin current along the film magnetization can also be tuned by tuning the barrier potential $V_0$ at the junction. We point out the role of the chiral spin-momentum locking of the Dirac electrons behind this phenomenon and suggest experiments to test our theory.Comment: Revised version with supplemental material

Fermionic Chern-Simons Theory of SU(4) Fractional Quantum Hall Effect

We develop a Fermionic Chern-Simons (CS) theory for the fractional quantum Hall effect in monolayer graphene with SU(4) symmetry, arising from the spin and the valley degrees of freedom, which involves four distinct CS gauge fields. We choose the corresponding elements of the CS coupling matrix such that an even number of spin and valley quantum number dependent flux quanta is attached to all electrons and that any electron with a given spin and valley quantum number sees an integer number of flux attached to other electrons with different (spin and valley) quantum numbers. Using this CS matrix, we obtain a list of possible fractional quantum Hall states that might occur in graphene and propose wavefunctions for those states. Our analysis also applies to fractional quantum Hall states of both bilayer quantum Hall systems without spin polarization and bilayer spin polarized graphene.Comment: v1; 1 Fig, 2 Tables, 7+ page

Multi-cell interference management in In-band D2D communication under LTE-A network

Device-to-Device (D2D) communication is an active research area. As a part of this active research area, Device-to-Device (D2D) communication is largely exploited in Out-band non-cellular technologies, such as, Bluetooth or Wi-Fi network. However, it has not been fully incorporated into existing cellular networks. Interference management is the main challenge of this technology as it generates both intra and inter-cell interference resulting in severe network performance degradation. eNodeBs with high transmit power usually affects D2D user equipments (UEs) with high interference. It usually incurs severe interference to the cellular UEs and to the base station (eNB). The scenario becomes more critical in case of multi-cell environment, which is the main research focus in this paper. In order to encourage and increase frequent use of D2D communications, some changes in the network configuration are required for today’s networking scenario. Flexible multi-cell D2D communication is required to reduce the network load. Interference management techniques are necessary in parallel to make the communication smooth, efficient and effective.This paper reviews multi-cell interference in In-Band D2D communications and investigates interference mitigation techniques in scenarios where two or more similar or different devices under same eNB or from two different eNBs can be connected as a D2D pair without compromising user experience and quality of service standard. These issues cannot be guaranteed by the current applications operated on unlicensed frequency band. The research also addresses the following related issues: mode selection, resource allocation (both for cellular and D2D environment), power control (both for eNB and D2D pair), and flexible frequency allocation techniques. The research aims to look at other issues, such as, achieving high SINR, improved system capacity, better throughput and transmission rate

Grand Challenges of Traceability: The Next Ten Years

In 2007, the software and systems traceability community met at the first Natural Bridge symposium on the Grand Challenges of Traceability to establish and address research goals for achieving effective, trustworthy, and ubiquitous traceability. Ten years later, in 2017, the community came together to evaluate a decade of progress towards achieving these goals. These proceedings document some of that progress. They include a series of short position papers, representing current work in the community organized across four process axes of traceability practice. The sessions covered topics from Trace Strategizing, Trace Link Creation and Evolution, Trace Link Usage, real-world applications of Traceability, and Traceability Datasets and benchmarks. Two breakout groups focused on the importance of creating and sharing traceability datasets within the research community, and discussed challenges related to the adoption of tracing techniques in industrial practice. Members of the research community are engaged in many active, ongoing, and impactful research projects. Our hope is that ten years from now we will be able to look back at a productive decade of research and claim that we have achieved the overarching Grand Challenge of Traceability, which seeks for traceability to be always present, built into the engineering process, and for it to have "effectively disappeared without a trace". We hope that others will see the potential that traceability has for empowering software and systems engineers to develop higher-quality products at increasing levels of complexity and scale, and that they will join the active community of Software and Systems traceability researchers as we move forward into the next decade of research

Temperature Dependent Mechanical Behavior of a Locally Restrained Graphite-Aluminum Laminated Plate under Bi-axial Loading

AbstractTemperature-dependent mechanical behavior of a locally restrained metal-matrix composite plate is investigated under uniform bi-axial compression. Thin rectangular plates of angle-ply and cross-ply laminate composed of Graphite-Aluminum composite are considered for the analysis. The plates are assumed to be locally restrained at their corner regions. Temperature-dependent me- chanical properties of the metal-matrix composite are used in the displacement-potential analysis of the elastic response. Results of deformed shapes as well as stress distributions are demonstrated as a function of temperature and fiber-orientation of the laminate

Spherical collapse of a heat conducting fluid in higher dimensions without horizon

We consider a scenario where the interior spacetime,described by a heat conducting fluid sphere is matched to a Vaidya metric in higher dimensions.Interestingly we get a class of solutions, where following heat radiation the boundary surface collapses without the appearance of an event horizon at any stage and this happens with reasonable properties of matter field.The non-occurrence of a horizon is due to the fact that the rate of mass loss exactly counterbalanced by the fall of boundary radius.Evidently this poses a counter example to the so-called cosmic censorship hypothesis.Two explicit examples of this class of solutions are also given and it is observed that the rate of collapse is delayed with the introduction of extra dimensions.The work extends to higher dimensions our previous investigation in 4D.Comment: 6 page