1,314 research outputs found

    Child universes UV regularization?

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    It is argued that high energy density excitations, responsible for UV divergences in quantum field theories, including quantum gravity, are likely to be the source of child universes which carry them out of the original space time. This decoupling prevents these high UV excitations from having any influence on physical amplitudes. Child universe production could therefore be responsible for UV regularization in quantum field theories which takes into account gravitational effects. Also child universe production in the last stages of black hole evaporation, the prediction of absence of tranplanckian primordial perturbations, connection to the minimum length hypothesis and in particular connection to the maximal curvature hypothesis are discussed.Comment: 6 pages, RevTex, discussion to the maximum curvature hypothesis adde

    Wormholes and Child Universes

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    Evidence to the case that classical gravitation provides the clue to make sense out of quantum gravity is presented. The key observation is the existence in classical gravitation of child universe solutions or "almost" solutions, "almost" because of some singularity problems. The difficulties of these child universe solutions due to their generic singularity problems will be very likely be cured by quantum effects, just like for example "almost" instanton solutions are made relevant in gauge theories with breaking of conformal invariance. Some well motivated modifcations of General Relativity where these singularity problems are absent even at the classical level are discussed. High energy density excitations, responsible for UV divergences in quantum field theories, including quantum gravity, are likely to be the source of child universes which carry them out of the original space time. This decoupling could prevent these high UV excitations from having any influence on physical amplitudes. Child universe production could therefore be responsible for UV regularization in quantum field theories which take into account semiclassically gravitational effects. Child universe production in the last stages of black hole evaporation, the prediction of absence of tranplanckian primordial perturbations, connection to the minimum length hypothesis and in particular the connection to the maximal curvature hypothesis are discussed. Some discussion of superexcited states in the case these states are Kaluza Klein excitations is carried out. Finally, the posibility of obtaining "string like" effects from the wormholes associated with the child universes is discussed.Comment: Talk presented at the IWARA 2009 Conference, Maresias, Brazil, October 2009, accepted for publication in the proceedings, World Scientific format, 8 page

    Second-layer nucleation in coherent Stranski-Krastanov growth of quantum dots

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    We have studied the monolayer-bilayer transformation in the case of the coherent Stranski-Krastanov growth. We have found that the energy of formation of a second layer nucleus is largest at the center of the first-layer island and smallest on its corners. Thus nucleation is expected to take place at the corners (or the edges) rather than at the center of the islands as in the case of homoepitaxy. The critical nuclei have one atom in addition to a compact shape, which is either a square of i*i or a rectangle of i*(i-1) atoms, with i>1 an integer. When the edge of the initial monolayer island is much larger than the critical nucleus size, the latter is always a rectangle plus an additional atom, adsorbed at the longer edge, which gives rise to a new atomic row in order to transform the rectangle into the equilibrium square shape.Comment: 6 pages, 4 figures. Accepted version, minor change

    Comparative analysis of technical characteristics of cyclone dust collectors

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    The article presented an analytical review of existing designs of cyclone dust collectors, lists their main advantages compared to other vehicles of similar purpose. Classification of cyclone dust collectors, design features, advantages and disadvantages, application of back-and-flow cyclone, flow cyclone and whirl dust collectors are described. The factors influencing the efficiency of the cyclone apparatuses are analyzed. Advanced designs of cyclones CN are offered

    The feasibility grounds for using of untwisting devices in cyclones

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    The article presented a feasibility study of application of the developed constructions of untwisting devices in cyclone apparatus: blade untwisting device and the untwisting device with stream recirculation, allowing substantially to reduce pressure drop and promote efficiency of catching of dispersible particles. The calculations of economy of energy and money facilities are resulted at cleaning of gas in cyclones with the developed untwisting devices. Application in the most widespread cyclones CN-11 and CN-15 blade untwisting device power inputs on clearing 1,000 m3 gas decrease on the average on 0.25 and 0.15 kW · h, and using of the untwisting device with recirculation of a stream – on 0.2 and 0.11 kW · h accordingly. The term of recoupment of additional expenses on an untwisting device will make less than year

    Coherent Stranski-Krastanov growth in 1+1 dimensions with anharmonic interactions: An equilibrium study

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    The formation of coherently strained three-dimensional islands on top of the wetting layer in Stranski-Krastanov mode of growth is considered in a model in 1+1 dimensions accounting for the anharmonicity and non-convexity of the real interatomic forces. It is shown that coherent 3D islands can be expected to form in compressed rather than in expanded overlayers beyond a critical lattice misfit. In the latter case the classical Stranski-Krastanov growth is expected to occur because the misfit dislocations can become energetically favored at smaller island sizes. The thermodynamic reason for coherent 3D islanding is the incomplete wetting owing to the weaker adhesion of the edge atoms. Monolayer height islands with a critical size appear as necessary precursors of the 3D islands. The latter explains the experimentally observed narrow size distribution of the 3D islands. The 2D-3D transformation takes place by consecutive rearrangements of mono- to bilayer, bi- to trilayer islands, etc., after exceeding the corresponding critical sizes. The rearrangements are initiated by nucleation events each next one requiring to overcome a lower energetic barrier. The model is in good qualitative agreement with available experimental observations.Comment: 12 pages text, 15 figures, Accepted in Phys.Rev.B, Vol.61, No2

    EPG-representations with small grid-size

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    In an EPG-representation of a graph GG each vertex is represented by a path in the rectangular grid, and (v,w)(v,w) is an edge in GG if and only if the paths representing vv an ww share a grid-edge. Requiring paths representing edges to be x-monotone or, even stronger, both x- and y-monotone gives rise to three natural variants of EPG-representations, one where edges have no monotonicity requirements and two with the aforementioned monotonicity requirements. The focus of this paper is understanding how small a grid can be achieved for such EPG-representations with respect to various graph parameters. We show that there are mm-edge graphs that require a grid of area Ω(m)\Omega(m) in any variant of EPG-representations. Similarly there are pathwidth-kk graphs that require height Ω(k)\Omega(k) and area Ω(kn)\Omega(kn) in any variant of EPG-representations. We prove a matching upper bound of O(kn)O(kn) area for all pathwidth-kk graphs in the strongest model, the one where edges are required to be both x- and y-monotone. Thus in this strongest model, the result implies, for example, O(n)O(n), O(nlogn)O(n \log n) and O(n3/2)O(n^{3/2}) area bounds for bounded pathwidth graphs, bounded treewidth graphs and all classes of graphs that exclude a fixed minor, respectively. For the model with no restrictions on the monotonicity of the edges, stronger results can be achieved for some graph classes, for example an O(n)O(n) area bound for bounded treewidth graphs and O(nlog2n)O(n \log^2 n) bound for graphs of bounded genus.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

    Field of homogeneous Plane in Quantum Electrodynamics

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    We study quantum electrodynamics coupled to the matter field on singular background, which we call defect. For defect on the infinite plane we calculated the fermion propagator and mean electromagnetic field. We show that at large distances from the defect plane, the electromagnetic field is constant what is in agreement with the classical results. The quantum corrections determining the field near the plane are calculated in the leading order of perturbation theory.Comment: 16 page

    Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath

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    The calculating of ionic equilibria in the system «Pb(CH3COO)2 - CdCl2 - Na3C6H5O7 - ‎(NH3)2(CH2)2 - N2H4CS» allowed us to find conditions and concentration regions of PbS and CdS co-deposition. The determined conditions provided the CBD obtaining of CdxPb1−xS (0 ≤ x ≤ 0.033) substitutional solid solutions films with a cubic structure B1 (space group Fm ) with the grains preferred orientation (200). We established the evolution of the surface morphology of the synthesized films from cubic crystallites to hierarchical structure of globular aggregates by scanning electron microscopy. A quantitative analysis of diffraction patterns showed a decrease of microstrains in CdxPb1−xS films by a about factor of 3 with an increase of the cadmium chloride concentration in the reaction mixture from 0.005 to 0.14 mol/l. The excess of the cadmium content, established by EDX analysis, in the studied films as compared to its content in the solid solution is associated with the additional formation of the amorphous CdS phase up to 72 mol %.A Corrigendum is available for this article at https://doi.org/10.15826/chimtech.2021.8.2.12

    Psychosomatic disorders in clinical practice

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    Psychosomatic disorders in a broad sense represent a group of conditions that are different in etiology and pathogenesis, characterizing the interconnection and mutual influence of the somatic and mental sphere: psychosomatic diseases, somatoform disorders, somatogenia, psychogenia, personality traits and behavior that lead to the development of somatic diseases. Diagnosis of psychosomatic disorders in patients in the somatic network is of great practical importance in connection with the early detection of pathology and effective action on the immediate causes of its occurrence
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