## Topics in Lattice QCD and Effective Field Theory

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##### Date

2010##### Author

Buchoff, Michael Ireland

##### Advisor

Bedaque, Paulo F

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Show full item record##### Abstract

Quantum Chromodynamics (QCD) is the fundamental theory that governs
hadronic physics. However, due to its non-perturbative nature at low-energy/long
distances, QCD calculations are difficult. The only method for performing these
calculations is through lattice QCD. These computationally intensive calculations
approximate continuum physics with a discretized lattice in order to extract hadronic
phenomena from first principles. However, as in any approximation, there are multiple
systematic errors between lattice QCD calculation and actual hardronic phenomena.
Developing analytic formulae describing the systematic errors due to the
discrete lattice spacings is the main focus of this work.
To account for these systematic effects in terms of hadronic interactions, effective
field theory proves to be useful. Effective field theory (EFT) provides a
formalism for categorizing low-energy effects of a high-energy fundamental theory
as long as there is a significant separation in scales. An example of this is in chiral
perturbation theory (χPT ), where the low-energy effects of QCD are contained in a
mesonic theory whose applicability is a result of a pion mass smaller than the chiral
breaking scale. In a similar way, lattice χPT accounts for the low-energy effects of
lattice QCD, where a small lattice spacing acts the same way as the quark mass.
In this work, the basics of this process are outlined, and multiple original calculations
are presented: effective field theory for anisotropic lattices, I=2 ππ scattering
for isotropic, anisotropic, and twisted mass lattices. Additionally, a combination of
effective field theory and an isospin chemical potential on the lattice is proposed
to extract several computationally difficult scattering parameters. Lastly, recently
proposed local, chiral lattice actions are analyzed in the framework of effective field
theory, which illuminates various challenges in simulating such actions.

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