Staggered Chiral Perturbation Theory

We discuss how to formulate a staggered chiral perturbation theory. This amounts to a generalization of the Lee-Sharpe Lagrangian to include more than one flavor (i.e. multiple staggered fields), which turns out to be nontrivial. One loop corrections to pion and kaon masses and decay constants are computed as examples in three cases: the quenched, partially quenched, and full (unquenched) case. The results for the one loop mass and decay constant corrections have already been presented in Ref. [1].Comment: talk presented by C. Aubin at Lattice2002(spectrum); 3 pages, 1 figur

Reevaluating the Roles of Large Public Surpluses and Sovereign Wealth Funds in Asia

This paper discusses the increasingly important roles of Asian official institutions in the new global financial landscape and the reasons that have led to the build-up of massive public surpluses. We re-examine the role of sovereign wealth funds (SWFs) as the de facto "global lender of last resort" during the recent financial crisis. Specifically, we analyze SWFs’ balance sheet characteristics, target allocations strategies, strategic agendas and political realities, management philosophies, and other real-world challenges, both before and after the crisis. Part of our analysis incorporates data which includes announced deals, regulatory filings, balance sheet information, and actual performance data made available by specific SWFs. We also point out a logical inconsistency in the common application of the Berk-Green alpha argument to the management of SWFs. For instance, the recent work done by Ang, Goetzmann, and Schaefer (2009) suggests limited or no evidence that alpha-seeking activities have impacts on SWF performance. We argue that the problem may be partially due to the choice of an appropriate performance benchmark for such large, non-commercial mandates. Finally, we propose a set of principles to construct a fair performance benchmark for SWFs.sovereign wealth funds; global financial crisis; public surpluses; global financial system

Penguin diagrams for improved staggered fermions

We calculate, at the one loop level, penguin diagrams for improved staggered fermion operators constructed using various fat links. The main result is that diagonal mixing coefficients with penguin operators are identical between the unimproved operators and the improved operators using such fat links as Fat7, Fat7+Lepage, $\bar{\rm Fat7}$, HYP (I) and HYP (II). In addition, it turns out that the off-diagonal mixing vanishes for those constructed using fat links of Fat7, $\bar{\rm Fat7}$ and HYP (II). This is a consequence of the the fact that the improvement by various fat links changes only the mixing with higher dimension operators and off-diagonal operators. The results of this paper, combined with those for current-current diagrams, provide the complete matching at the one loop level with all corrections of ${\cal O}(g^2)$ included.Comment: 11 pages, 4 figure

Sheets of BPS Monopoles and Instantons with Arbitrary Simple Gauge Group

We show that the BPS configurations of uniform field strength can be interpreted as those for sheets of infinite number of BPS magnetic monopoles, and found that the number of normalizable zero modes per each magnetic monopole charge is four. We identify monopole sheets as the intersecting planes of D3 branes. Similar analysis on self-dual instanton configurations is worked out and the number of zero modes per each instanton number is found to match that of single isolated instanton.Comment: LaTex file, 11 page

Chiral logs with staggered fermions

We compute chiral logarithms in the presence of "taste" symmetry breaking of staggered fermions. The lagrangian of Lee and Sharpe is generalized and then used to calculate the logs in $\pi$ and $K$ masses. We correct an error in Ref. [1] [C. Bernard, hep-lat/0111051]; the issue turns out to have implications for the comparison with simulations, even at tree level. MILC data with three light dynamical flavors can be well fit by our formulas. However, two new chiral parameters, which describe order $a^2$ hairpin diagrams for taste-nonsinglet mesons, enter in the fits. To obtain precise results for the physical coefficients at order $p^4$, these new parameters will need to be bounded, at least roughly.Comment: talk presented by C. Bernard at Lattice2002(spectrum); 3 pages, 2 figure

All-fiber fused directional coupler for highly efficient spatial mode conversion

We model and demonstrate a simple mode selective all-fiber coupler capable of exciting specific higher order modes in two- and few-mode fibres with high efficiency and purity. The coupler is based on inter-modally phase-matching the propagation constants in each arm of the asymmetric fused coupler, formed by dissimilar fibres. At a specific coupler diameter, the launched fundamental LP01 mode is coupled into the higher order mode (LP11, LP21, LP02) in the other arm, over a broadband wavelength range around 1550 nm. Unlike other techniques, the demonstrated coupler is composed of a multimode fiber that is weakly fused with a phase matched conventional single mode telecom fiber (SMF-28). The beating between the supermodes at the coupler waist produces a periodic power transfer between the two arms, and therefore, by monitoring the beating while tapering, it is possible to obtain optimum selection for the desired mode. High coupling efficiencies in excess of 90% for all the higher order modes were recorded over 100 nm spectral range, while insertion losses remain as low as 0.5 dB. Coupling efficiency can be further enhanced by performing slow tapering at high temperature, in order to precisely control the coupler cross-section geometry

Recent progress in calculating weak matrix elements using staggered fermions

We present a chronological review of the progress in calculating weak matrix elements using staggered fermions. We review the perturbative calculation of one-loop matching formula including both current-current diagrams and penguin diagrams using improved staggered fermions. We also present preliminary results of weak matrix elements relevant to CP violation calculated using the improved (HYP (II)) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the $g^2$ corrections included. The main results include both $\Delta I = 3/2$ and $\Delta I = 1/2$ contributions.Comment: 7 pages, 7 figures, LHP200

Meson-baryon sigma terms in QCD Sum Rules

We evaluate the pion-nucleon and the pion-Delta sigma terms by employing the method of quantum chromodynamics (QCD) sum rules. The obtained value of the pion-nucleon sigma term is compatible with the larger values already anticipated by the recent calculations. It is also found that the pion-Delta sigma term is as large as the pion-nucleon sigma term.Comment: 14 pages, 2 figures; extended discussion and added references; version to be published in Phys. Lett.