5,630 research outputs found
An Improved Action for Heavy Quarks
We extend the Fermilab method for heavy quarks to include all interactions of
dimension six in the action. We discuss a subtlety in the power counting, which
implies that, for heavy quarks, certain interactions of dimension seven are
commensurate with some of those of dimension six. We then present tree-level
matching conditions obtained from calculating the Compton scattering amplitude
for (lattice) QCD. When the matching conditions have been applied, the improved
action removes (tree-level) discretization errors of order
and .Comment: 1+5 pp., contribution to Lattice 2006(Quark Masses, Gauge Couplings,
and Renormalization
A Solution to Matching with Preferences over Colleagues
We study many-to-one matchings, such as the assignment of students to colleges, where the students have preferences over the other students who would attend the same college. It is well known that the core of this model may be empty, without strong assumptions on agents' preferences. We introduce a method that finds all core matchings, if any exist. The method requires no assumptions on preferences. Our method also finds certain partial solutions that may be useful when the core is empty.Matching markets, Core, Lattice, Gale-Shapley algorithm
Why blame?
We provide experimental evidence that subjects blame others based on events they are not responsible for. In our experiment an agent chooses between a lottery and a safe asset; payment from the chosen option goes to a principal who then decides how much to allocate between
the agent and a third party. We observe widespread blame: regardless of their choice, agents are blamed by principals for the outcome of the lottery, an event they are not responsible for. We provide an explanation of this apparently irrational behavior with a delegated-expertise
principal-agent model, the subjectsâ salient perturbation of the environment
DNA Typing Compatibility with a One Step Saliva Screening Test
Screening a substrate for bodily fluids is an extremely important step for locating areas that may contain DNA. Several different methods have been developed for saliva (1). The PhadebasÂź Forensic Press (PFP) test is a presumptive saliva test that utilizes a preloaded paper that will react with the enzyme amylase, a component of saliva (2-5). Because of its ability to screen for amylase while simultaneously locating stains, the PFP may prove to be an effective, rapid method for screening. However it is important to assess whether the PFP introduces any inhibitors (7) to downstream processing such as PCR amplification. Based on previous studies, we hypothesize that the PFP will provide a rapid and sensitive method for locating multiple saliva stains simultaneously, without introducing inhibitors to DNA profiling. To test the limitations of PFP as well as evaluated its effects on DNA profiling we first created a dilution series of saliva ranging from neat to 1:5000. After this we preformed sensitivity tests on an indirect method, UV degraded samples and washed samples as well as with bodily fluid mixtures. Once all sensitivity tests were done, cuttings were taken from the substrate and PFP paper and analyzed for DNA. Tests found that the sensitivity ranges of the PFP were between 1:10 and 1:1000, indirect tests were less sensitive than direct, all bodily fluid mixtures were detected, and UV degraded samples took more time to react. In addition our DNA results confirmed our hypothesis that PFP does not inhibit DNA and is a useful method for locating stains. This project was funded by NSFREU Grant DBI 1262832
Engineering nonlinear response of nanomaterials using Fano resonances
We show that, nonlinear optical processes of nanoparticles can be controlled
by the presence of interactions with a molecule or a quantum dot. By choosing
the appropriate level spacing for the quantum emitter, one can either suppress
or enhance the nonlinear frequency conversion. We reveal the underlying
mechanism for this effect, which is already observed in recent experiments: (i)
Suppression occurs simply because transparency induced by Fano resonance does
not allow an excitation at the converted frequency. (ii) Enhancement emerges
since nonlinear process can be brought to resonance. Path interference effect
cancels the nonresonant frequency terms. We demonstrate the underlying physics
using a simplified model, and we show that the predictions of the model are in
good agreement with the 3-dimensional boundary element method (MNPBEM toolbox)
simulations. Here, we consider the second harmonic generation in a plasmonic
converter as an example to demonstrate the control mechanism. The phenomenon is
the semi-classical analog of nonlinearity enhancement via electromagnetically
induced transparency.Comment: 10 pages, 6 figure
Spectral functions of charmonium from 2 flavour anisotropic lattice data
The spectral functions of QCD can give us insight into properties of hadrons,
and they are useful in probing the QCD vacuum. I will discuss the correlators
and spectral functions of charmonium in high temperature two flavour QCD. The
spectral functions have been obtained using the Maximum Entropy Method from
anisotropic lattice data using the conserved vector current. This work has been
done as part of the FASTSUM collaboration. We find that the spectral functions
for zero momentum are stable. At non-zero momentum the spectral functions are
less stable but still produce resonance and transport peaks. This work is part
of our programme to calculate the heavy quark diffusion constant.Comment: 7 pages, 5 figures, 31st International Symposium on Lattice Field
Theory LATTICE 201
Heavy-quark meson spectrum tests of the Oktay-Kronfeld action
The Oktay-Kronfeld (OK) action extends the Fermilab improvement program for
massive Wilson fermions to higher order in suitable power-counting schemes. It
includes dimension-six and -seven operators necessary for matching to QCD
through order in HQET power counting, for
applications to heavy-light systems, and in NRQCD power
counting, for applications to quarkonia. In the Symanzik power counting of
lattice gauge theory near the continuum limit, the OK action includes all
and some terms. To assess whether the
theoretical improvement is realized in practice, we study combinations of
heavy-strange and quarkonia masses and mass splittings, designed to isolate
heavy-quark discretization effects. We find that, with one exception, the
results obtained with the tree-level-matched OK action are significantly closer
to the continuum limit than the results obtained with the Fermilab action. The
exception is the hyperfine splitting of the bottom-strange system, for which
our statistical errors are too large to draw a firm conclusion. These studies
are carried out with data generated with the tadpole-improved Fermilab and OK
actions on 500 gauge configurations from one of MILC's ~fm,
-flavor, asqtad-staggered ensembles.Comment: 12 pages, 5 figure
- âŠ