845 research outputs found

    Angular momentum I ground state probabilities of boson systems interacting by random interactions

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    In this paper we report our systematic calculations of angular momentum II ground state probabilities (P(I)P(I)) of boson systems with spin ll in the presence of random two-body interactions. It is found that the P(0) dominance is usually not true for a system with an odd number of bosons, while it is valid for an even number of bosons, which indicates that the P(0) dominance is partly connected to the even number of identical particles. It is also noticed that the P(Imax)P(I_{max})'s of bosons with spin ll do not follow the 1/N (N=l+1N=l+1, referring to the number of independent two-body matrix elements) relation. The properties of the P(I)P(I)'s obtained in boson systems with spin ll are discussed.Comment: 8 pages and 3 figure

    JJ-pairing Interactions of Fermions in a Single-jj Shell

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    In this talk I shall introduce our recent works on general pairing interactions and pair truncation approximations for fermions in a single-j shell, including the spin zero dominance, features of eigenvalues of fermion systems in a single-j shell interacting by a J‚ąíJ-pairing interaction.Comment: 10 pages and 4 figures, international symposiu

    Geometry of random interactions

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    It is argued that spectral features of quantal systems with random interactions can be given a geometric interpretation. This conjecture is investigated in the context of two simple models: a system of randomly interacting d bosons and one of randomly interacting fermions in a j=7/2 shell. In both examples the probability for a given state to become the ground state is shown to be related to a geometric property of a polygon or polyhedron which is entirely determined by particle number, shell size, and symmetry character of the states. Extensions to more general situations are discussed

    Ground state spin 0+^+ dominance of many-body systems with random interactions and related topics

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    In this talk we shall show our recent results in understanding the spinparity^{\rm parity} 0+^+ ground state (0 g.s.) dominance of many-body systems. We propose a simple approach to predict the spin II g.s. probabilities which does not require the diagonalization of a Hamiltonian with random interactions. Some findings related to the 0 g.s. dominance will also be discussed.Comment: 11 pages and 4 figure

    A study of randomness, correlations and collectivity in the nuclear shell model

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    A variable combination of realistic and random two-body interactions allows the study of collective properties, such as the energy spectra and B(E2) transition strengths in 44Ti, 48Cr and 24Mg. It is found that the average energies of the yrast band states maintain the ordering for any degree of randomness, but the B(E2) values lose their quadrupole collectivity when randomness dominates the Hamiltonian. The high probability of the yrast band to be ordered in the presence of pure random forces exhibits the strong correlations between the different members of the band.Comment: 8 pages, 10 figures, 8 tables, submitted to Physical Review

    Numerical case studies of vertical wall fire protection using water spray

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    AbstractStudies of vertical wall fire protection are evaluated with numerical method. Typical fire cases such as heated dry wall and upward flame spread have been validated. Results predicted by simulations are found to agree with experiment results. The combustion behavior and flame development of vertical polymethylmethacrylate slabs with different water flow rates are explored and discussed. Water spray is found to be capable of strengthening the fire resistance of combustible even under high heat flux radiation. Provided result and data are expected to provide reference for fire protection methods design and development of modern buildings

    Flux dynamics and vortex phase diagram of the new superconductor MgB2MgB_2

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    Magnetic critical current density and relaxation rate have been measured on MgB2MgB_2 bulks from 1.6 K to TcT_c at magnetic fields up to 8 Tesla. A vortex phase diagram is depicted based on these measurement. Two phase boundaries Hirrbulk(T)H_{irr}^{bulk}(T) and Hirrg(T)H_{irr}^{g}(T) characterizing different irreversible flux motions are found. The Hirrbulk(T)H_{irr}^{bulk}(T) is characterized by the appearance of the linear resistivity and is attributed to quantum vortex melting induced by quantum fluctuation of vortices in the rather clean system. The second boundary Hirrg(T) H_{irr}^g(T) reflects the irreversible flux motion in some local regions due to either very strong pinning or the surface barrier on the tiny grains.Comment: 4 pages, 5 figure

    Generic Rotation in a Collective SD Nucleon-Pair Subspace

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    Low-lying collective states involving many nucleons interacting by a random ensemble of two-body interactions (TBRE) are investigated in a collective SD-pair subspace, with the collective pairs defined dynamically from the two-nucleon system. It is found that in this truncated pair subspace collective vibrations arise naturally for a general TBRE hamiltonian whereas collective rotations do not. A hamiltonian restricted to include only a few randomly generated separable terms is able to produce collective rotational behavior, as long as it includes a reasonably strong quadrupole-quadrupole component. Similar results arise in the full shell model space. These results suggest that the structure of the hamiltonian is key to producing generic collective rotation.Comment: 11 pages, 5 figure

    To tweet or not to tweet about schizophrenia systematic reviews (TweetSz): study protocol for a randomised controlled trial

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    Introduction: The Cochrane Schizophrenia Group (CSzG) has produced and maintained systematic reviews of effects of interventions for schizophrenia and related illness. Each review has a Plain Language Summary (PLS), for those without specialised knowledge, and an abstract, which are freely available from The Cochrane Library (https://summaries.cochrane.org). Increasingly, evidence is being distributed using social media such as Twitter and Weibo (in China) alongside traditional publications. Methods and analysis: In a prospective two-arm, parallel, open randomised controlled trial with a 1:1 allocation ratio, we will allocate 170 published systematic reviews into the intervention group (tweeting arm/Weibo arm) versus the control group (non-tweeting arm). Reviews will be stratified by baseline access activity, defined as high (‚Č•19 views per week, n=14), medium (4.3 to 18.99 views per week, n=72) or low (<4.3 views per week, n=84), based on Google Analytics, which will also be used for evaluating outcomes. The intervention group will have three tweets daily using Hootsuite with a slightly different accompanying text (written by CEA and AB) and a shortened Uniform Resource Locator (URL) to the PLS: a) The review title as it appears in summaries.cochrane.org, b) A pertinent extract from results or discussion sections of the abstract and c) An intriguing question or pithy statement related to the evidence in the abstract. The primary outcome will be: total number of visits to a PLS in 7‚ÄÖdays following the tweet. Secondary outcomes will include % new visits, bounce rate, pages per visit, visit duration, page views, unique page views, time on page, entrances, exiting behaviour and country distribution. Ethics and dissemination: This study does not involve living participants, and uses information available in the public domain. Participants are published systematic reviews, hence, no ethical approval is required. Dissemination will be via Twitter, Weibo and traditional academic means
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