15,129 research outputs found

    Effects of rotation in the energy spectrum of C60C_{60}

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    In this paper, motivated by the experimental evidence of rapidly rotating C60C_{60} molecules in fullerite, we study the low-energy electronic states of rotating fullerene within a continuum model. In this model, the low-energy spectrum is obtained from an effective Dirac equation including non-Abelian gauge fields that simulate the pentagonal rings of the molecule. Rotation is incorporated into the model by solving the effective Dirac equation in the rotating referential frame. The exact analytical solution for the eigenfunctions and energy spectrum is obtained, yielding the previously known static results in the no rotation limit. Due to the coupling between rotation and total angular momentum, that appears naturally in the rotating frame, the zero modes of static C60C_{60} are shifted and also suffer a Zeeman splitting whithout the presence of a magnetic field

    Inertial-Hall effect: the influence of rotation on the Hall conductivity

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    Inertial effects play an important role in classical mechanics but have been largely overlooked in quantum mechanics. Nevertheless, the analogy between inertial forces on mass particles and electromagnetic forces on charged particles is not new. In this paper, we consider a rotating non-interacting planar two-dimensional electron gas with a perpendicular uniform magnetic field and investigate the effects of the rotation in the Hall conductiv

    A dynamical point of view of Quantum Information: entropy and pressure

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    Quantum Information is a new area of research which has been growing rapidly since last decade. This topic is very close to potential applications to the so called Quantum Computer. In our point of view it makes sense to develop a more "dynamical point of view" of this theory. We want to consider the concepts of entropy and pressure for "stationary systems" acting on density matrices which generalize the usual ones in Ergodic Theory (in the sense of the Thermodynamic Formalism of R. Bowen, Y. Sinai and D. Ruelle). We consider the operator L\mathcal{L} acting on density matrices ρ∈MN\rho\in \mathcal{M}_N over a finite NN-dimensional complex Hilbert space L(ρ):=∑i=1ktr(WiρWi∗)ViρVi∗,\mathcal{L}(\rho):=\sum_{i=1}^k tr(W_i\rho W_i^*)V_i\rho V_i^*, where WiW_i and ViV_i, i=1,2,...ki=1,2,...k are operators in this Hilbert space. L\mathcal{L} is not a linear operator. In some sense this operator is a version of an Iterated Function System (IFS). Namely, the Vi (.) Vi∗=:Fi(.)V_i\,(.)\,V_i^*=:F_i(.), i=1,2,...,ki=1,2,...,k, play the role of the inverse branches (acting on the configuration space of density matrices ρ\rho) and the WiW_i play the role of the weights one can consider on the IFS. We suppose that for all ρ\rho we have that ∑i=1ktr(WiρWi∗)=1\sum_{i=1}^k tr(W_i\rho W_i^*)=1. A family W:={Wi}i=1,...,kW:=\{W_i\}_{i=1,..., k} determines a Quantum Iterated Function System (QIFS) FW\mathcal{F}_{W}, $\mathcal{F}_W=\{\mathcal{M}_N,F_i,W_i\}_{i=1,..., k}.

    A dynamical point of view of Quantum Information: Wigner measures

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    We analyze a known version of the discrete Wigner function and some connections with Quantum Iterated Funcion Systems. This paper is a follow up of "A dynamical point of view of Quantum Information: entropy and pressure" by the same authors

    A Thermodynamic Formalism for density matrices in Quantum Information

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    We consider new concepts of entropy and pressure for stationary systems acting on density matrices which generalize the usual ones in Ergodic Theory. Part of our work is to justify why the definitions and results we describe here are natural generalizations of the classical concepts of Thermodynamic Formalism (in the sense of R. Bowen, Y. Sinai and D. Ruelle). It is well-known that the concept of density operator should replace the concept of measure for the cases in which we consider a quantum formalism. We consider the operator Λ\Lambda acting on the space of density matrices MN\mathcal{M}_N over a finite NN-dimensional complex Hilbert space Λ(ρ):=∑i=1ktr(WiρWi∗)ViρVi∗tr(ViρVi∗), \Lambda(\rho):=\sum_{i=1}^k tr(W_i\rho W_i^*)\frac{V_i\rho V_i^*}{tr(V_i\rho V_i^*)}, where WiW_i and ViV_i, i=1,2,...,ki=1,2,..., k are linear operators in this Hilbert space. In some sense this operator is a version of an Iterated Function System (IFS). Namely, the Vi (.) Vi∗=:Fi(.)V_i\,(.)\,V_i^*=:F_i(.), i=1,2,...,ki=1,2,...,k, play the role of the inverse branches (i.e., the dynamics on the configuration space of density matrices) and the WiW_i play the role of the weights one can consider on the IFS. In this way a family W:={Wi}i=1,...,kW:=\{W_i\}_{i=1,..., k} determines a Quantum Iterated Function System (QIFS). We also present some estimates related to the Holevo bound

    Tumour necrosis factor-alpha and interleukin-8 inhibit neutrophil migration in vitro and in vivo

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    Pretreatment of human neutrophils with recombinant tumour necrosis factor-alpha (rTNF-α) and/or interleukin-8 (rIL-8), but not with either transforming growth factor-beta, interleukin-6 or interferon-gamma, rendered these cells less responsive to FMLP, in microchemotaxis assays. This inhibitory effect was dose dependent and more powerful when neutrophils were pretreated with a mixture of both cytokines. Intravenous injection of human rIL-8 (hrIL-8) and/or murine rTNF-α (mrTNF-α) also significantly reduced in vivo neutrophil migration into peritoneal cavities of rats stimulated with carrageenan. These data suggest that the defect in neutrophil migration during septicaemia or endotoxaemia may be the result of the continuous release of IL-8 and TNF-α into the circulation. Thus, either the selective control or blockade of releasing of these cytokines as well as of its effects on neutrophils may be clinically useful in reestablishing the cell defence mechanisms

    Asymptotic Entanglement Dynamics and Geometry of Quantum States

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    A given dynamics for a composite quantum system can exhibit several distinct properties for the asymptotic entanglement behavior, like entanglement sudden death, asymptotic death of entanglement, sudden birth of entanglement, etc. A classification of the possible situations was given in [M. O. Terra Cunha, {\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no known examples. In this work we give a better classification for the possibile relaxing dynamics at the light of the geometry of their set of asymptotic states and give explicit examples for all the classes. Although the classification is completely general, in the search of examples it is sufficient to use two qubits with dynamics given by differential equations in Lindblad form (some of them non-autonomous). We also investigate, in each case, the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J. Phys. A: Math. Theo

    Theory of Stellar Oscillations

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    In recent years, astronomers have witnessed major progresses in the field of stellar physics. This was made possible thanks to the combination of a solid theoretical understanding of the phenomena of stellar pulsations and the availability of a tremendous amount of exquisite space-based asteroseismic data. In this context, this chapter reviews the basic theory of stellar pulsations, considering small, adiabatic perturbations to a static, spherically symmetric equilibrium. It starts with a brief discussion of the solar oscillation spectrum, followed by the setting of the theoretical problem, including the presentation of the equations of hydrodynamics, their perturbation, and a discussion of the functional form of the solutions. Emphasis is put on the physical properties of the different types of modes, in particular acoustic (p-) and gravity (g-) modes and their propagation cavities. The surface (f-) mode solutions are also discussed. While not attempting to be comprehensive, it is hoped that the summary presented in this chapter addresses the most important theoretical aspects that are required for a solid start in stellar pulsations research.Comment: Lecture presented at the IVth Azores International Advanced School in Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta, Azores Islands, Portugal in July 201
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