16,187 research outputs found

    Quasi-Phase Transition and Many-Spin Kondo Effects in Graphene Nanodisk

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    The trigonal zigzag nanodisk with size NN has NN localized spins. We investigate its thermodynamical properties with and without external leads. Leads are made of zigzag graphene nanoribbons or ordinary metallic wires. There exists a quasi-phase transition between the quasi-ferromagnet and quasi-paramagnet states, as signaled by a sharp peak in the specific heat and in the susceptability. Lead effects are described by the many-spin Kondo Hamiltonian. A new peak emerges in the specific heat. Furthermore, the band width of free electrons in metallic leads becomes narrower. By investigating the spin-spin correlation it is argued that free electrons in the lead form spin-singlets with electrons in the nanodisk. They are indications of many-spin Kondo effects.Comment: 5 pages, 5 figure

    Quasinormal modes of Unruh's Acoustic Black Hole

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    We have studied the sound perturbation of Unruh's acoustic geometry and we present an exact expression for the quasinormal modes of this geometry. We are obtain that the quasinormal frequencies are pure-imaginary, that give a purely damped modes.Comment: 5 Page

    A two-stage approach to relaxation in billiard systems of locally confined hard spheres

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    We consider the three-dimensional dynamics of systems of many interacting hard spheres, each individually confined to a dispersive environment, and show that the macroscopic limit of such systems is characterized by a coefficient of heat conduction whose value reduces to a dimensional formula in the limit of vanishingly small rate of interaction. It is argued that this limit arises from an effective loss of memory. Similarities with the diffusion of a tagged particle in binary mixtures are emphasized.Comment: Submitted to Chaos, special issue "Statistical Mechanics and Billiard-Type Dynamical Systems

    Exact results for spatial decay of the one-body density matrix in low-dimensional insulators

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    We provide a tight-binding model of insulator, for which we derive an exact analytic form of the one-body density matrix and its large-distance asymptotics in dimensions D=1,2D=1,2. The system is built out of a band of single-particle orbitals in a periodic potential. Breaking of the translational symmetry of the system results in two bands, separated by a direct gap whose width is proportional to the unique energy parameter of the model. The form of the decay is a power law times an exponential. We determine the power in the power law and the correlation length in the exponential, versus the lattice direction, the direct-gap width, and the lattice dimension. In particular, the obtained exact formulae imply that in the diagonal direction of the square lattice the inverse correlation length vanishes linearly with the vanishing gap, while in non-diagonal directions, the linear scaling is replaced by the square root one. Independently of direction, for sufficiently large gaps the inverse correlation length grows logarithmically with the gap width.Comment: 4 pages, 2 figure

    Municipal Solid Waste Flow Control in the Post-Carbone World

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    Garbage will always ultimately be the government\u27s problem. Evolving environmental standards and state and federal policies will continue to require reasoned responses from local governments and municipal solid waste flow control is a vital cog in many jurisdictions\u27 solid waste management solutions. Without flow control of some form, governments\u27 ability to plan and provide for the most environmentally sound and economically acceptable solutions will wane, leaving the public vulnerable to the vagaries of a private market that does not have a duty to protect the public health and safety. The Carbone decision has blunted one of the local governments chief weapons-legislative flow control-and it appears Congress will not supply an adequate answer for many solid waste systems. More than ever, alternatives to legislative flow control will be needed to enable municipalities to fulfill their solid waste duties, to comply with federal and state mandates, and to provide workable, environmentally-sound, long-term solid waste programs serving the interests of the public health and safety. Local governments must act soon by examining these options and deciding which will best serve the public

    Upper limit on the critical strength of central potentials in relativistic quantum mechanics

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    In the context of relativistic quantum mechanics, where the Schr\"odinger equation is replaced by the spinless Salpeter equation, we show how to construct a large class of upper limits on the critical value, gc()g_{\rm{c}}^{(\ell)}, of the coupling constant, gg, of the central potential, V(r)=gv(r)V(r)=-g v(r). This critical value is the value of gg for which a first \ell-wave bound state appears.Comment: 8 page

    Global boundary conditions for a Dirac operator on the solid torus

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    We study a Dirac operator subject to Atiayh-Patodi-Singer like boundary conditions on the solid torus and show that the corresponding boundary value problem is elliptic, in the sense that the Dirac operator has a compact parametrix

    General boundary quantum field theory: Timelike hypersurfaces in Klein-Gordon theory

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    We show that the real massive Klein-Gordon theory admits a description in terms of states on various timelike hypersurfaces and amplitudes associated to regions bounded by them. This realizes crucial elements of the general boundary framework for quantum field theory. The hypersurfaces considered are hyperplanes on the one hand and timelike hypercylinders on the other hand. The latter lead to the first explicit examples of amplitudes associated with finite regions of space, and admit no standard description in terms of ``initial'' and ``final'' states. We demonstrate a generalized probability interpretation in this example, going beyond the applicability of standard quantum mechanics.Comment: 25 pages, LaTeX; typos correcte

    Dynamics of ultracold molecules in confined geometry and electric field

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    We present a time-independent quantum formalism to describe the dynamics of molecules with permanent electric dipole moments in a two-dimensional confined geometry such as a one-dimensional optical lattice, in the presence of an electric field. Bose/Fermi statistics and selection rules play a crucial role in the dynamics. As examples, we compare the dynamics of confined fermionic and bosonic polar KRb molecules under different confinements and electric fields. We show how chemical reactions can be suppressed, either by a "statistical suppression" which applies for fermions at small electric fields and confinements, or by a "potential energy suppression", which applies for both fermions and bosons at high electric fields and confinements. We also explore collisions that transfer molecules from one state of the confining potential to another. Although these collisions can be significant, we show that they do not play a role in the loss of the total number of molecules in the gas.Comment: 13 pages, 6 figure

    Interference detection in gaussian noise

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    Interference detection in gaussian noise is proposed. It can be applied for easy detection and editing of interference lines in radio spectral line observations. One need not know the position of occurence or keep track of interference in the band. Results obtained on real data have been displayed.Comment: 10 pages, 11 figure