5,607 research outputs found

    A CrC^{r} Closing Lemma for a Class of Symplectic Diffeomorphisms

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    We prove a CrC^r closing lemma for a class of partially hyperbolic symplectic diffeomorphisms. We show that for a generic CrC^r symplectic diffeomorphism, r=1,2,...,r =1, 2, ...,, with two dimensional center and close to a product map, the set of all periodic points is dense

    Generation of internal stress and its effects

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    Internal stresses may be generated continually in many polycrystalline materials. Their existence is manifested by changes in crystal defect concentration and arrangement, by surface observations, by macroscopic shape changes and particularly by alteration of mechanical properties when external stresses are simultaneously imposed

    Chiral Reductions in the Salam-Sezgin Model

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    Reductions from six to four spacetime dimensions are considered for a class of supergravity models based on the six-dimensional Salam-Sezgin model, which is a chiral theory with a gauged U(1) R-symmetry and a positive scalar-field potential. Reduction on a sphere and monopole background of such models naturally yields four-dimensional theories without a cosmological constant. The question of chirality preservation in such a reduction has been a topic of debate. In this article, it is shown that the possibilities of dimensional reduction bifurcate into two separate consistent dimensional-reduction schemes. One of these retains the massless SU(2) vector gauge triplet arising from the sphere's isometries, but it produces a non-chiral four-dimensional theory. The other consistent scheme sets to zero the SU(2) gauge fields, but retains the gauged U(1) from six dimensions and preserves chirality although the U(1) is spontaneously broken. Extensions of the Salam-Sezgin model to include larger gauge symmetries produce genuinely chiral models with unbroken gauge symmetries.Comment: 37 page

    Understanding the Behavior of Reinforcement Learning Agents

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    High pressure Ca-VI phase between 158-180 GPa: Stability, electronic structure and superconductivity

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    We have performed ab initio calculations for new high-pressure phase of Ca-VI between 158-180 GPa. The study includes elastic parameters of mono- and poly-crystalline aggregates, electronic band structure, lattice dynamics and superconductivity. The calculations show that the orthorhombic Pnma structure is mechanically and dynamically stable in the pressure range studied. The structure is superconducting in the entire pressure range and the calculated Tc (~25K) is maximum at ~172 GPa, where the transfer of charges from 4s to 3d may be thought to be completed.Comment: 8 pages, 4 figures; PACS number(s): 74.70.Ad, 62.20.de, 71.20.-b, 74.20.Pq, 74.25.Kc, 74.62.Fj; Keywords: Calcium; High pressure; Electronic band structure; Phonon spectrum; Elastic constants; Superconducto

    Interviewing anorexia: How do individuals given a diagnosis of anorexia nervosa experience Voice Dialogue with their eating disorder voice? A qualitative analysis

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    A proportion of individuals given an eating disorder diagnosis describe the experience of an eating disorder ‘voice’ (EDV). However, methods for working with this experience are currently lacking. Voice Dialogue (Stone & Stone, 1989) involves direct communication between a facilitator and parts of the self to increase awareness, understanding, and separation from inner voices. Adapted forms of this method have shown promise in working with voices in psychosis. This study aimed to explore the experience and acceptability of Voice Dialogue amongst individuals with anorexia nervosa who experience an EDV. Nine women participated in a semistructured interview following a single Voice Dialogue session. Interview transcripts were analysed using interpretative phenomenological analysis (IPA). Three overarching themes were identified as follows: (i) “separating from the EDV”; (ii) “better understanding of the EDV”; and (iii) “hopeful, motivated, and afraid of recovery”. The majority of participants found Voice Dialogue acceptable and helpful for exploring their EDV. Whilst preliminary, the results suggest that Voice Dialogue has potential in terms of helping individuals establish a more constructive relationship with their EDV and motivating change. Further research is needed to build upon these findings. Implications for addressing the EDV using voice-focused interventions are explored

    Electronic band structure, Fermi surface, and elastic properties of new 4.2K superconductor SrPtAs from first-principles calculations

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    The hexagonal phase SrPtAs (s.g. P6/mmm; #194) with a honeycomb lattice structure very recently was declared as a new low-temperature (TC ~ 4.2K) superconductor. Here by means of first-principles calculations the optimized structural parameters, electronic bands, Fermi surface, total and partial densities of states, inter-atomic bonding picture, independent elastic constants, bulk and shear moduli for SrPtAs were obtained for the first time and analyzed in comparison with the related layered superconductor SrPt2As2.Comment: 8 pages, 4 figure

    On CrC^r-closing for flows on 2-manifolds

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    For some full measure subset B of the set of iet's (i.e. interval exchange transformations) the following is satisfied: Let X be a CrC^r, 1r1\le r\le \infty, vector field, with finitely many singularities, on a compact orientable surface M. Given a nontrivial recurrent point pMp\in M of X, the holonomy map around p is semi-conjugate to an iet E:[0,1)[0,1).E :[0,1) \to [0,1). If EBE\in B then there exists a CrC^r vector field Y, arbitrarily close to X, in the CrC^r-topology, such that Y has a closed trajectory passing through p.Comment: 7 pages, 1 figur
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