10,509 research outputs found
Two dimensional fermions in three dimensional YM
Dirac fermions in the fundamental representation of SU(N) live on the surface
of a cylinder embedded in and interact with a three dimensional SU(N)
Yang Mills vector potential preserving a global chiral symmetry at finite .
As the circumference of the cylinder is varied from small to large, the chiral
symmetry gets spontaneously broken in the infinite limit at a typical bulk
scale. Replacing three dimensional YM by four dimensional YM introduces
non-trivial renormalization effects.Comment: 21 pages, 7 figures, 5 table
Chiral Symmetry Restoration in the Schwinger Model with Domain Wall Fermions
Domain Wall Fermions utilize an extra space time dimension to provide a
method for restoring the regularization induced chiral symmetry breaking in
lattice vector gauge theories even at finite lattice spacing. The breaking is
restored at an exponential rate as the size of the extra dimension increases.
Before this method can be used in dynamical simulations of lattice QCD, the
dependence of the restoration rate to the other parameters of the theory and,
in particular, the lattice spacing must be investigated. In this paper such an
investigation is carried out in the context of the two flavor lattice Schwinger
model.Comment: LaTeX, 37 pages including 18 figures. Added comments regarding power
law fitting in sect 7. Also, few changes were made to elucidate the content
in sect. 5.1 and 5.3. To appear in Phys. Rev.
Consistent and covriant anomalies in the overlap formulation of chiral gauge theories
In this letter we show how the covariant anomaly emerges in the overlap
scheme. We also prove that the overlap scheme correctly reproduces the anomaly
in the flavour currents such as in vector like theories like QCD.Comment: 10 pages, Late
Density of states in graphene with vacancies: midgap power law and frozen multifractality
The density of states (DoS), , of graphene is investigated
numerically and within the self-consistent T-matrix approximation (SCTMA) in
the presence of vacancies within the tight binding model. The focus is on
compensated disorder, where the concentration of vacancies, and
, in both sub-lattices is the same. Formally, this model belongs to
the chiral symmetry class BDI. The prediction of the non-linear sigma-model for
this class is a Gade-type singularity . Our numerical data is compatible with this
result in a preasymptotic regime that gives way, however, at even lower
energies to , . We take this finding as an evidence that similar to the case
of dirty d-wave superconductors, also generic bipartite random hopping models
may exhibit unconventional (strong-coupling) fixed points for certain kinds of
randomly placed scatterers if these are strong enough. Our research suggests
that graphene with (effective) vacancy disorder is a physical representative of
such systems.Comment: References updated onl
Vacuum Polarization and Chiral Lattice Fermions
The vacuum polarization due to chiral fermions on a 4--dimensional Euclidean
lattice is calculated according to the overlap prescription. The fermions are
coupled to weak and slowly varying background gauge and Higgs fields, and the
polarization tensor is given by second order perturbation theory. In this order
the overlap constitutes a gauge invariant regularization of the fermion vacuum
amplitude. Its low energy -- long wavelength behaviour can be computed
explicitly and we verify that it coincides with the Feynman graph result
obtainable, for example, by dimensional regularization of continuum gauge
theory. In particular, the Standard Model Callan--Symanzik RG functions are
recovered. Moreover, there are no residual lattice artefacts such as a
dependence on Wilson--type mass parameters.Comment: 23 pages, LaTe
On the Overlap Prescription for Lattice Regularization of Chiral Fermions
Feynman rules for the vacuum amplitude of fermions coupled to external gauge
and Higgs fields in a domain wall lattice model are derived using
time--dependent perturbation theory. They have a clear and simple structure
corresponding to 1--loop vacuum graphs. Their continuum approximations are
extracted by isolating the infrared singularities and it is shown that, in each
order, they reduce to vacuum contributions for chiral fermions. In this sense
the lattice model is seen to constitute a valid regularization of the continuum
theory of chiral fermions coupled to weak and slowly varying gauge and Higgs
fields. The overlap amplitude, while not gauge invariant, exhibits a well
defined (modulo phase conventions) response to gauge transformations of the
background fields. This response reduces in the continuum limit to the expected
chiral anomaly, independently of the phase conventions.Comment: 32 pages, late
The mediating role of emotional exhaustion in the relationship of mindfulness with turnover intentions and job performance
The role of mindfulness in the workplace has emerged as a legitimate and growing area of organizational scholarship. T he present research examined the role of employee emotional exhaustion in mediating the relationship of mindfulness with turnover intentions and task performance . Drawing on theory and empirical research on both organizational behavior and mindfulness, w e predicted that more mindful employees would show lower turnover intentions and higher task performance and that th e s e relationship s would be mediated by emotional exhaustion. We tested these hypotheses in two field studies in an Indian context. Study 1 was a field study of call center employees of a multinational organization, an industry in which turnover rates are very high. This study found that mindfulness was associated with lower turnover intentions and less emotional exhaustion , and that emotional ex haustion mediated the relationship between mindfulness and turnover intentions. Study 2 replicated these results in a sample of employees based in major Indian cities and drawn from different industries. In addition, it showed that mindfulness was positive ly related to supervisor - rated task performance, with e motional exhaustion again playing a mediating role. We discuss theoretical and practical implications of our findings , as well as future research directions
X-ray Near Field Speckle: Implementation and Critical Analysis
We have implemented the newly-introduced, coherence-based technique of x-ray
near-field speckle (XNFS) at 8-ID-I at the Advanced Photon Source. In the near
field regime of high-brilliance synchrotron x-rays scattered from a sample of
interest, it turns out, that, when the scattered radiation and the main beam
both impinge upon an x-ray area detector, the measured intensity shows
low-contrast speckles, resulting from interference between the incident and
scattered beams. We built a micrometer-resolution XNFS detector with a high
numerical aperture microscope objective and demonstrate its capability for
studying static structures and dynamics at longer length scales than
traditional far field x-ray scattering techniques. Specifically, we
characterized the structure and dynamics of dilute silica and polystyrene
colloidal samples. Our study reveals certain limitations of the XNFS technique,
which we discuss.Comment: 53 pages, 16 figure
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