14,995 research outputs found

    Equilibrium states in open quantum systems

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    The aim of the paper is to study the question whether or not equilibrium states exist in open quantum systems that are embedded in at least two environments and are described by a non-Hermitian Hamilton operator H\cal H. The eigenfunctions of H\cal H contain the influence of exceptional points (EPs) as well as that of external mixing (EM) of the states via the environment. As a result, equilibrium states exist (far from EPs). They are different from those of the corresponding closed system. Their wavefunctions are orthogonal although the Hamiltonian is non-Hermitian.Comment: 12 page

    Binary Stars in Planetary Nebulae

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    When a star like the sun dies, it swells into a red giant and then expels its outer layers to form a planetary nebula. Eventually the outer layers leave the leftover core and it becomes a white dwarf. The cause of the many exotic shapes in the planetary nebulae is unknown; however, it is thought that binary stars may play a role in the shaping process. In this project we are studying the central stars of planetary nebulae to see if they vary in brightness, and to see if that variability is due to the central star having a binary companion. Data is collected with the SARA North and SARA South telescopes. We have recently found the central star of the planetary nebula PN G337.0+08.4 to vary with a period of 0.2959 days (7.102 hours). We have data for this object in green (V), red (R), and blue (B) filters. The data strongly indicates that the central star does have a binary companion. Using a binary star modeling program we have found several possible sets of physical parameters for the binary central star of the planetary nebula PN G337.0+08.4

    Exceptional points and double poles of the S matrix

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    Exceptional points and double poles of the S matrix are both characterized by the coalescence of a pair of eigenvalues. In the first case, the coalescence causes a defect of the Hilbert space. In the second case, this is not so as shown in prevoius papers. Mathematically, the reason for this difference is the bi-orthogonality of the eigenfunctions of a non-Hermitian operator that is ignored in the first case. The consequences for the topological structure of the Hilbert space are studied and compared with existing experimental data.Comment: 9 pages, no figure
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