3,467,079 research outputs found

    Geometric quantization rules in QCPB theory

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    Using the QCPB theory, we can accomplish the compatible combination of the quantum mechanics and general relativity supported by the G-dynamics. We further study the generalized quantum harmonic oscillator, such as geometric creation and annihilation operators, especially, the geometric quantization rules based on the QCPB theory.Comment: 14 page

    Probe Brane Dynamics and the Cosmological Constant

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    Recently a brane world perspective on the cosmological constant and the hierarchy problems was presented. Here, we elaborate on some aspects of that particular scenario and discuss the stability of the stationary brane solution and the dynamics of a probe brane. Even though the brane is unstable under a small perturbation from its stationary position, such instability is harmless when the 4-D cosmological constant is very small, as is the case of our universe. One may also introduce radion stabilizing potentials in a more realistic scenario.Comment: 13 pages, 1 figure, REVTE

    Casimir energy for de Sitter branes in bulk AdS(5)

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    The vacuum energy for a massless conformally coupled scalar field in a brane world set up, corresponding to de Sitter branes in a bulk anti-de Sitter spacetime, is calculated. We use the Euclidean version of the metric which can be conformally related to a metric similar in form to the Einstein universe (S^4 times R). Employing zeta-function regularisation we evaluate the one-loop effective potential and show that the vacuum energy is zero for the one brane and non-zero for the two brane configuration. We comment on the back-reaction of this Casimir energy and on the inclusion of a mass term or non-conformal coupling.Comment: 6 pages, no figures, references added, typos corrected, to be published in Phys. Lett.

    Warped compactification to de Sitter space

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    We explore in detail the prospects of obtaining a four-dimensional de Sitter universe in classical supergravity models with warped and time-independent extra dimensions, presenting explicit cosmological solutions of the (4+n)(4+n)-dimensional Einstein equations with and without a bulk cosmological constant term. For the first time in the literature we show that there may exist a large class of warped supergravity models with a noncompact extra dimension which lead to a finite 4D Newton constant as well as a massless 4D graviton localised on an inflating four-dimensional FLRW universe. This result helps establish that the `no-go' theorem forbidding acceleration in `standard' compactification of string/M-theory on physically compact spaces should not apply to a general class of warped supergravity models that allows at least one noncompact direction. We present solutions for which the size of the radial dimension takes a constant value in the large volume limit, providing an explicit example of spontaneous compactification.Comment: 19 pages, 2 figures; final (journal) versio

    Marine yeast isolation and industrial application

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    Over the last century, terrestrial yeasts have been widely used in various industries, such as baking, brewing, wine, bioethanol and pharmaceutical protein production. However, only little attention has been given to marine yeasts. Recent research showed that marine yeasts have several unique and promising features over the terrestrial yeasts, for example higher osmosis tolerance, higher special chemical productivity and production of industrial enzymes. These indicate that marine yeasts have great potential to be applied in various industries. This review gathers the most recent techniques used for marine yeast isolation as well as the latest applications of marine yeast in bioethanol, pharmaceutical and enzyme production fields. Keyword

    On cardinal invariants and generators for von Neumann algebras

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    We demonstrate how virtually all common cardinal invariants associated to a von Neumann algebra M can be computed from the decomposability number, dec(M), and the minimal cardinality of a generating set, gen(M). Applications include the equivalence of the well-known generator problem, "Is every separably-acting von Neumann algebra singly-generated?", with the formally stronger questions, "Is every countably-generated von Neumann algebra singly-generated?" and "Is the gen invariant monotone?" Modulo the generator problem, we determine the range of the invariant (gen(M), dec(M)), which is mostly governed by the inequality dec(M) leq c^{gen(M)}.Comment: 22 pages; the main additions are Theorem 3.8 and Section

    Localization of Scalar Fluctuations in a Dilatonic Brane-World Scenario

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    We derive and solve the full set of scalar perturbation equations for a class of Z2Z_2-symmetric five-dimensional geometries generated by a bulk cosmological constant and by a 3-brane non-minimally coupled to a bulk dilaton field. The massless scalar modes, like their tensor analogues, are localized on the brane, and provide long-range four-dimensional dilatonic interactions, which are generically present even when matter on the brane carries no dilatonic charge. The shorter-range corrections induced by the continuum of massive scalar modes are always present: they persist even in the case of a trivial dilaton background (the standard Randall--Sundrum configuration) and vanishing dilatonic charges.Comment: 22 pages, late
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