5,607 research outputs found
A Closing Lemma for a Class of Symplectic Diffeomorphisms
We prove a closing lemma for a class of partially hyperbolic symplectic
diffeomorphisms. We show that for a generic symplectic diffeomorphism, , 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
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
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
High pressure Ca-VI phase between 158-180 GPa: Stability, electronic structure and superconductivity
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
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
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
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Serving GODAE Data and Products to the Ocean Community
The Global Ocean Data Assimilation Experiment (GODAE [http://
www.godae.org]) has spanned a decade of rapid technological development. The ever-increasing volume and diversity of oceanographic data produced by in situ instruments, remote-sensing platforms, and computer simulations have driven
the development of a number of innovative technologies that are essential for connecting scientists with the data that they need. This paper gives an overview of the technologies that have been developed and applied in the course of GODAE, which now provide users of oceanographic data with the capability to discover, evaluate, visualize, download, and analyze data from all over the world. The key to this
capability is the ability to reduce the inherent complexity of oceanographic data by providing a consistent, harmonized view of the various data products. The challenges of data serving have been addressed over the last 10 years through the cooperative skills and energies of many individuals
On closing for flows on 2-manifolds
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 , , vector field, with finitely many singularities, on a compact
orientable surface M. Given a nontrivial recurrent point of X, the
holonomy map around p is semi-conjugate to an iet If
then there exists a vector field Y, arbitrarily close to X, in
the topology, such that Y has a closed trajectory passing through p.Comment: 7 pages, 1 figur
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