10,588 research outputs found
Topological Phases in Neuberger-Dirac operator
The response of the Neuberger-Dirac fermion operator D=\Id + V in the
topologically nontrivial background gauge field depends on the negative mass
parameter in the Wilson-Dirac fermion operator which enters
through the unitary operator . We classify
the topological phases of by comparing its index to the topological charge
of the smooth background gauge field. An exact discrete symmetry in the
topological phase diagram is proved for any gauge configurations. A formula for
the index of D in each topological phase is derived by obtaining the total
chiral charge of the zero modes in the exact solution of the free fermion
propagator.Comment: 27 pages, Latex, 3 figures, appendix A has been revise
Sintered silicon nitrode recuperator fabrication
The preliminary design and a demonstration of the feasibility of fabricating submodules of an automotive Stirling engine recuperator for waste heat recovery at 370 C are described. Sinterable silicon nitride (Sialon) tubing and plates were fabricated by extrusion and hydrostatic pressing, respectively, suitable for demonstrating a potential method of constructing ceramic recuperator-type heat exchangers. These components were fired in nitrogen atmosphere to 1800 C without significant scale formation so that they can be used in the as-fired condition. A refractory glass composition (Al2O3 x 4.5 CaO.MgO x 11SiO2) was used to join and seal component parts by a brazing technique which formed strong recuperator submodules capable of withstanding repeated thermal cycling to 1370 C. The corrosion resistance of these materials to Na2SO4 + NaCl carbon mixtures was also assessed in atmospheres of air, hydrogen and CO2-N2-H2O mixtures at both 870 C and 1370 C for times to 1000 hours. No significant reaction was observed under any of these test conditions
A note on Zolotarev optimal rational approximation for the overlap Dirac operator
We discuss the salient features of Zolotarev optimal rational approximation
for the inverse square root function, in particular, for its applications in
lattice QCD with overlap Dirac quark. The theoretical error bound for the
matrix-vector multiplication is derived. We check that
the error bound is always satisfied amply, for any QCD gauge configurations we
have tested. An empirical formula for the error bound is determined, together
with its numerical values (by evaluating elliptic functions) listed in Table 2
as well as plotted in Figure 3. Our results suggest that with Zolotarev
approximation to , one can practically preserve the exact
chiral symmetry of the overlap Dirac operator to very high precision, for any
gauge configurations on a finite lattice.Comment: 23 pages, 5 eps figures, v2:minor clarifications, and references
added, to appear in Phys. Rev.
Chiral fermions on the lattice and index relations
Comparing recent lattice results on chiral fermions and old continuum results
for the index puzzling questions arise. To clarify this issue we start with a
critical reconsideration of the results on finite lattices. We then work out
various aspects of the continuum limit. After determining bounds and norm
convergences we obtain the limit of the anomaly term. Collecting our results
the index relation of the quantized theory gets established. We then compare in
detail with the Atiyah-Singer theorem. Finally we analyze conventional
continuum approaches.Comment: 34 pages; a more detaild introduction and a subsection with remarks
on literature adde
Influence of retardation effects on 2D magnetoplasmon spectrum
Within dissipationless limit the magnetic field dependence of magnetoplasmon
spectrum for unbounded 2DEG system found to intersect the cyclotron resonance
line, and, then approaches the frequency given by light dispersion relation.
Recent experiments done for macroscopic disc-shape 2DEG systems confirm theory
expectations.Comment: 2 pages,2 figure
THE STUDY OF RELATED FACTORS WITH BALL VELOCITY OF THROWING OF GIRLS AGED 11-12 YEARS OLD
INTRODUCTION: The forceful overarm throwing is considered a fundamental movement for many skills. In addition, it is also regards as a characteristic of child’s development. As to the researches of development, gender difference is also concerned by experts of development.
Research related to child motor development traditionally follow the structure of Burton’s (1992) on amendment of Development Sequences for Overhand Throwing table to measure throwing patterns. But overarm throwing is a kind of fast motion especially for the period which is from backswing to release. The traditional way mentioned above can’t provide detailed data. The purpose of the study was to find out the related factors with ball velocity of throwing of girls aged 11-12 years
Quenched chiral logarithms in lattice QCD with exact chiral symmetry
We examine quenched chiral logarithms in lattice QCD with overlap Dirac
quark. For 100 gauge configurations generated with the Wilson gauge action at on the lattice, we compute quenched quark
propagators for 12 bare quark masses. The pion decay constant is extracted from
the pion propagator, and from which the lattice spacing is determined to be
0.147 fm. The presence of quenched chiral logarithm in the pion mass is
confirmed, and its coefficient is determined to be , in agreement with the theoretical estimate in quenched chiral perturbation
theory. Further, we obtain the topological susceptibility of these 100 gauge
configurations by measuring the index of the overlap Dirac operator. Using a
formula due to exact chiral symmetry, we obtain the mass in quenched
chiral perturbation theory, Mev, and an estimate
of , which is in good agreement with that
determined from the pion mass.Comment: 24 pages, 6 EPS figures; v2: some clarifications added, to appear in
Physical Review
On the continuum limit of fermionic topological charge in lattice gauge theory
It is proved that the fermionic topological charge of SU(N) lattice gauge
fields on the 4-torus, given in terms of a spectral flow of the Hermitian
Wilson--Dirac operator, or equivalently, as the index of the Overlap Dirac
operator, reduces to the continuum topological charge in the classical
continuum limit when the parameter is in the physical region .Comment: latex, 18 pages. v2: Several comments added. To appear in J.Math.Phy
Stops and MET: the shape of things to come
LHC experiments have placed strong bounds on the production of supersymmetric
colored particles (squarks and gluinos), under the assumption that all flavors
of squarks are nearly degenerate. However, the current experimental constraints
on stop squarks are much weaker, due to the smaller production cross section
and difficult backgrounds. While light stops are motivated by naturalness
arguments, it has been suggested that such particles become nearly impossible
to detect near the limit where their mass is degenerate with the sum of the
masses of their decay products. We show that this is not the case, and that
searches based on missing transverse energy (MET) have significant reach for
stop masses above 175 GeV, even in the degenerate limit. We consider direct
pair production of stops, decaying to invisible LSPs and tops with either
hadronic or semi-leptonic final states. Modest intrinsic differences in MET are
magnified by boosted kinematics and by shape analyses of MET or suitably-chosen
observables related to MET. For these observables we show that the
distributions of the relevant backgrounds and signals are well-described by
simple analytic functions, in the kinematic regime where signal is enhanced.
Shape analyses of MET-related distributions will allow the LHC experiments to
place significantly improved bounds on stop squarks, even in scenarios where
the stop-LSP mass difference is degenerate with the top mass. Assuming 20/fb of
luminosity at 8 TeV, we conservatively estimate that experiments can exclude or
discover degenerate stops with mass as large as ~ 360 GeV and 560 GeV for
massless LSPs.Comment: Version submitted to journal with improved analysis and small fixes,
27 pages, 11 figures, 2 table
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