287 research outputs found
Gravitating Instantons In 3 Dimensions
We study the Einstein-Chern-Simons gravity coupled to Yang-Mills-Higgs theory
in three dimensional Euclidean space with cosmological constant. The classical
equations reduce to Bogomol'nyi type first order equations in curved space.
There are BPS type gauge theory instanton (monopole) solutions of finite action
in a gravitational instanton which itself has a finite action. We also discuss
gauge theory instantons in the vacuum (zero action) AdS space. In addition we
point out to some exact solutions which are singular.Comment: 17 pages, 4 figures, title has changed, gravitational instanton
actions are adde
Yang-Mills Solutions on Euclidean Schwarzschild Space
We show that the apparently periodic Charap-Duff Yang-Mills `instantons' in
time-compactified Euclidean Schwarzschild space are actually time independent.
For these solutions, the Yang-Mills potential is constant along the time
direction (no barrier) and therefore, there is no tunneling. We also
demonstrate that the solutions found to date are three dimensional monopoles
and dyons. We conjecture that there are no time-dependent solutions in the
Euclidean Schwarzschild background.Comment: 12 pages, references added, version to appear in PR
Direct Detection of Dark Matter in the MSSM with Non-Universal Higgs Masses
We calculate dark matter scattering rates in the minimal supersymmetric
extension of the Standard Model (MSSM), allowing the soft
supersymmetry-breaking masses of the Higgs multiplets, m_{1,2}, to be
non-universal (NUHM). Compared with the constrained MSSM (CMSSM) in which
m_{1,2} are required to be equal to the soft supersymmetry-breaking masses m_0
of the squark and slepton masses, we find that the elastic scattering cross
sections may be up to two orders of magnitude larger than values in the CMSSM
for similar LSP masses. We find the following preferred ranges for the
spin-independent cross section: 10^{-6} pb \ga \sigma_{SI} \ga 10^{-10} pb, and
for the spin-dependent cross section: 10^{-3} pb \ga \sigma_{SD}, with the
lower bound on \sigma_{SI} dependent on using the putative constraint from the
muon anomalous magnetic moment. We stress the importance of incorporating
accelerator and dark matter constraints in restricting the NUHM parameter
space, and also of requiring that no undesirable vacuum appear below the GUT
scale. In particular, values of the spin-independent cross section another
order of magnitude larger would appear to be allowed, for small \tan \beta, if
the GUT vacuum stability requirement were relaxed, and much lower cross-section
values would be permitted if the muon anomalous magnetic moment constraint were
dropped.Comment: 30 pages LaTeX, 40 eps figure
Examining the Role of Narrative Performance Appraisal Comments on Performance
Despite their prevalence in performance appraisal systems and purported importance in theory, narrative performance appraisal comments have been rarely examined. This study aimed to contribute to the literature by developing and testing a theory of quality narrative feedback. The author argues that managerial feedback that is both directive (i.e., lengthy, specific, and includes goals) and motivational (i.e., positive and high in interactional justice) would be related to year-lagged performance. Negative and positive emotions are also proposed as mediators of this relationship. Performance appraisal comments were coded for a sample of 1,019 clinical nurses. The structural equations modeling results provided preliminary evidence that feedback favorability and interactional justice demonstrated significant direct and indirect (through positive and negative emotion) effects on year-lagged employee performance. © 2013 Copyright Taylor and Francis Group, LLC
First-Person Perspective Effects on Theory of Mind without Self-Reference
This study examined dissociations between brain networks involved in theory of mind, which is needed for guessing others' mental states, and the self, which might constitute the basis for theory of mind's development. We used event-related fMRI to compare a condition that required participants to guess the mental state of a subject featured in first-person perspective sentences (1stPP condition) with a third-person perspective sentence condition (3rdPP condition). The caudate nucleus was marginally more activated in the 1stPP than in the 3rdPP condition, while the left dorsolateral prefrontal cortex (DLPFC) was significantly more activated in the 3rdPP condition as compared to the 1stPP condition. Furthermore, we examined the correlation between activation (signal intensity) of the caudate nucleus and left DLPFC with that of the right DLPFC, which is thought to be closely connected with sense of self. We found a significant correlation between caudate nucleus and right DLPFC activation in the 1stPP condition, and between left and right DLPFC activation in the 3rdPP condition. Although theory of mind and the self both appear to recruit the right DLPFC, this region seems to be accessed through the left DLPFC during theory of mind tasks, but through the caudate nucleus when tasks require self reference
Graphene-based ultrathin flat lenses
Flat lenses when compared to curved surface lenses have the advantages of being aberration free and they offer a compact design necessary for a myriad of electro-optical applications. In this paper we present flat and ultra-thin lenses based on graphene, the worldâs thinnest known material. Monolayers and low number multilayers of graphene were fabricated into Fresnel zones to produce Fresnel zone plates which utilize the reflection and transmission properties of graphene for their operation. The working of the lens and their performance in the visible and terahertz regimes was analyzed computationally. Experimental measurements were also performed to characterize the lens in the visible regime and a good agreement was obtained with the simulations. The work demonstrates the principle of atom thick graphene-based lenses, with perspectives for ultra-compact integration.HB would like to thank The Leverhulme Trust for the research funding. QD is supported by Bureau of International Cooperation, Chinese Academy of Sciences (121D11KYSB20130013).This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/ph500197j
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