304 research outputs found
Noncommutativity Approach to Supersymmetry on the Lattice: SUSY Quantum Mechanics and an Inconsistency
It is argued that the noncommutativity approach to fully supersymmetric field
theories on the lattice suffers from an inconsistency. Supersymmetric quantum
mechanics is worked out in this formalism and the inconsistency is shown both
in general and explicitly for that system, as well as for the Abelian super BF
model.Comment: 8 pages, typo's corrected, conclusions unchange
A Critique of the Link Approach to Exact Lattice Supersymmetry
We examine the link approach to constructing a lattice theory of N=2 super
Yang Mills theory in two dimensions. The goal of this construction is to
provide a discretization of the continuum theory which preserves all
supersymmetries at non-zero lattice spacing. We show that this approach suffers
from an inconsistency and argue that a maximum of just one of the
supersymmetries can be implemented on the lattice.Comment: 7 page
Quantitative comparison of filtering methods in lattice QCD
We systematically compare filtering methods used to extract topological
excitations (like instantons, calorons, monopoles and vortices) from lattice
gauge configurations, namely APE-smearing and spectral decompositions based on
lattice Dirac and Laplace operators. Each of these techniques introduces
ambiguities, which can invalidate the interpretation of the results. We show,
however, that all these methods, when handled with care, reveal very similar
topological structures. Hence, these common structures are free of ambiguities
and faithfully represent infrared degrees of freedom in the QCD vacuum. As an
application we discuss an interesting power-law for the clusters of filtered
topological charge.Comment: 6 pages, 18 plots in 5 figures; final version as published in EPJ A;
section 4 was adde
Intrapartum asphyxia and hypoxic ischaemic encephalopathy in a public hospital: Incidence and predictors of poor outcome
Objective: To determine the incidence of asphyxia and hypoxic ischaemic encephalopathy (HIE) and predictors of poor outcome in a hospital in a developing country.Methods: Neonates of birth weight ≥2 000 g who required bag-and-mask ventilation and were admitted with a primary diagnosis of asphyxia from January to December 2011 were included. Medical records were retrieved and maternal and infant data collected and analysed. Infants who had severe HIE and/or died were compared with those who survived to hospital discharge with no or mild to moderate HIE.Results: There were 21 086 liveborn infants with a birth weight of ≥2 000 g over the study period. The incidence of asphyxia ranged from 8.7 to 15.2/1 000 live births and that of HIE from 8.5 to 13.3/1 000, based on the definition of asphyxia used. In 60% of patients with HIE it was moderate to severe. The overall mortality rate was 7.8%. The mortality rate in infants with moderate and severe HIE was 7.1% and 62.5%, respectively. The odds of severe HIE and/or death were high if the Apgar score was <5 at 10 minutes (odds ratio (OR) 19.1; 95% confidence interval (CI) 5.7 - 66.9) and if there was no spontaneous respiration at 20 minutes (OR 27.2; 95% CI 6.9 - 117.4), a need for adrenaline (OR 81.2; 95% CI 13.2 - 647.7) and a pH of <7 (OR 5.33; 95% CI 1.31 - 25.16). Predictors of poor outcome were Apgar score at 10 minutes (p=0.004), need for adrenaline (p=0.034) and low serum bicarbonate (p=0.028).Conclusion: The incidence of asphyxia in term and near-term infants is higher than that reported in developed countries. Apgar score at 10 minutes and need for adrenaline remain important factors in predicting poor outcome in infants with asphyxia
Local CP-violation and electric charge separation by magnetic fields from lattice QCD
We study local CP-violation on the lattice by measuring the local correlation
between the topological charge density and the electric dipole moment of
quarks, induced by a constant external magnetic field. This correlator is found
to increase linearly with the external field, with the coefficient of
proportionality depending only weakly on temperature. Results are obtained on
lattices with various spacings, and are extrapolated to the continuum limit
after the renormalization of the observables is carried out. This
renormalization utilizes the gradient flow for the quark and gluon fields. Our
findings suggest that the strength of local CP-violation in QCD with physical
quark masses is about an order of magnitude smaller than a model prediction
based on nearly massless quarks in domains of constant gluon backgrounds with
topological charge. We also show numerical evidence that the observed local
CP-violation correlates with spatially extended electric dipole structures in
the QCD vacuum.Comment: 19 pages, 7 figures. Additional lattice results about the induced
electric dipole structure, extended model description, specified terminology.
Version published in JHE
Deconfinement phase transition and the quark condensate
We study the dual quark condensate as a signal for the
confinement-deconfinement phase transition of QCD. This order parameter for
center symmetry has been defined recently by Bilgici et al. within the
framework of lattice QCD. In this work we determine the ordinary and the dual
quark condensate with functional methods using a formulation of the
Dyson-Schwinger equations for the quark propagator on a torus. The temperature
dependence of these condensates serves to investigate the interplay between the
chiral and deconfinement transitions of quenched QCD.Comment: 4 pages, 3 figures, v2: minor changes, typos corrected, version
accepted by PR
Ethane-1,2-diylbis(methylÂphosphinic acid)
In the title compound, C4H12O4P2, there are two crystallographically independent half-molÂecules in the asymmetric unit, both molecules lying on centres of symmetry. Each molÂecule is connected on both sides to neighbouring molÂecules via strong O—Hâ‹ŻO hydrogen bonds. The –POOH groups accept and donate one hydrogen bond in interactions with the neighbouring –POOH group of the adjacent molÂecule, to give one-dimensional chains along [10]. As each phosphinic acid group donates and accepts one hydrogen bond, the connection between the molÂecules is best described by a ring motif which can be classified by the Etter symbol R
2
2(8)
Thermodynamic properties of QCD in external magnetic fields
We consider the effect of strong external electromagnetic fields on
thermodynamic observables in QCD, through lattice simulations with 1+1+1
flavors of staggered quarks at physical quark masses. Continuum extrapolated
results are presented for the light quark condensates and for their tensor
polarizations, as functions of the temperature and the magnetic field. We find
the light condensates to undergo inverse magnetic catalysis in the transition
region, in a manner that the transition temperature decreases with growing
magnetic field. We also compare the results to other approaches and lattice
simulations. Furthermore, we relate the tensor polarization to the spin part of
the magnetic susceptibility of the QCD vacuum, and show that this contribution
is diamagnetic.Comment: 13 pages, 9 figures, talks presented by FB and GE at Xth Quark
Confinement and the Hadron Spectrum, 8-12 October 2012, TUM Campus Garching,
Munich, German
Probing for Instanton Quarks with epsilon-Cooling
We use epsilon-cooling, adjusting at will the order a^2 corrections to the
lattice action, to study the parameter space of instantons in the background of
non-trivial holonomy and to determine the presence and nature of constituents
with fractional topological charge at finite and zero temperature for SU(2). As
an additional tool, zero temperature configurations were generated from those
at finite temperature with well-separated constituents. This is achieved by
"adiabatically" adjusting the anisotropic coupling used to implement finite
temperature on a symmetric lattice. The action and topological charge density,
as well as the Polyakov loop and chiral zero-modes are used to analyse these
configurations. We also show how cooling histories themselves can reveal the
presence of constituents with fractional topological charge. We comment on the
interpretation of recent fermion zero-mode studies for thermalized ensembles at
small temperatures.Comment: 26 pages, 14 figures in 33 part
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