10,337 research outputs found

    Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr

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    Density functional theory (DFT) calculations are carried out on ReOFeAs, Re = Ce, Pr, the parent compounds of the high-Tc_c superconductors ReO1x_{1-x}Fx_{x}FeAs, in order to determine the magnetic order of the ground state. It is found that the magnetic moments on the Fe sites adopt a collinear antiferromagnetic order, similar to the case of LaOFeAs. Within the generalized gradient approximation along with Coulomb onsite repulsion (GGA+U), we show that the Re magnetic moments also adopt an antiferromagnetic order for which, within the ReO layer, same spin Re sites lie along a zigzag line perpendicular to the Fe spin stripes. While within GGA the Re 4f band crosses the Fermi level, upon inclusion of onsite Coulomb interaction the 4f band splits and moves away from the Fermi level, making ReOFeAs a Mott insulator.Comment: 5 pages, 4 figure

    Procol - A concurrent object-oriented language with protocols delegation and constraints

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    PROCOL is an object-oriented language with distributed delegation. It strongly supports concurrency: many objects may be active simultaneously, they execute in parallel unless engaged in communication. An object has exported operations, called Actions. Only one Action can be active at a time, however special interrupt Actions may interrupt regular Actions. Communication is performed via remote procedure call, or via a one-way synchronous message with short-time binding. In communications both client and server can be specified, either by object instance identifiers, or by type. Therefore client-server mappings may be 1-1, n-1, or 1-n, though only 1 message is transferred. PROCOL controls object access by an explicit per-object protocol. This protocol is a specification of the legality and serialization of the interaction between the object and its clients. It also provides for client type checking. The use of protocols in object communication fosters structured, safer and potentially verifiable information exchange between objects. The protocol also plays an important role as a partial interface specification. In addition it acts as a composition rule over client objects, representing relations with the client objects. PROCOL's communication binding is dynamic (run-time); it functions therefore naturally in a distributed, incremental and dynamic object environment. PROCOL also supports constraints, without compromising information hiding. An implementation is available in the form of a C extension

    Octet Magnetic Moments with Null Instantons and Semibosonized Nambu-Jona-Lasinio Model

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    It is shown that the difference between the magnetic moment results in the quark model with null instantons and semibosonized Nambu-Jona-Lasinio model lies in the description of the magnetic moment of the Λ \Lambda-hyperon.Comment: RevTex, 6 pages, submitted to Progr.Theor.Phy
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