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Full-Text Articles in Physical Sciences and Mathematics
Nonlocal Lorentz-Violating Modifications Of Qed, Qian Niu
Nonlocal Lorentz-Violating Modifications Of Qed, Qian Niu
Undergraduate Honors Theses
We consider nonlocal Lorentz-violating theories, with infinite-derivative quadratic terms. The nonlocal modifications in the form of exponential damping in the propagator lead to a better convergence of amplitudes than in the local theories. Moreover, the nonlocal Lorentz-violating theories are ghost-free and unitary when formulated in Minkowski space. We compute the loop effects assuming one-parameter and two-parameter nonlocal functions. By comparing the lower bound of the nonlocality scale with the Planck scale, we rule out these theories. We then review a more general argument, developed by Collins et al. (2004), that a microscopic theory with Lorentz violation around the Planck scale …
Progress Towards Electromagnetic Manipulation And Trapping Of Micro-Particles, Andrew John Beling
Progress Towards Electromagnetic Manipulation And Trapping Of Micro-Particles, Andrew John Beling
Undergraduate Honors Theses
This thesis describes research to investigate the electromagnetic manipulation of microspheres and microrings. The work consists of three main thrusts: 1) the use of an electric field gradient to move dielectric microspheres, 2) the use of an AC magnetic field to move a conducting ring, and 3) the preparation of substrates for a microwave atom chip. The electrostatic movement of dielectric polyethylene microspheres was observed and recorded with a CCD imaging system. The microspheres were suspended in various liquids and placed on top of a microstrip transmission line, which consists of a conducting copper trace separated from a ground plate …
Topology Of The O(3) Non-Linear Sigma Model Under The Gradient Flow, Stuart Thomas, Christopher Monahan
Topology Of The O(3) Non-Linear Sigma Model Under The Gradient Flow, Stuart Thomas, Christopher Monahan
Undergraduate Honors Theses
Quantum field theory is an extraordinarily successful framework that describes phenomena in particle physics and condensed matter. The O(3) non-linear sigma model (NLSM) is a specific theory used in both of these fields, describing ferromagnets and acting as a prototype for the strong nuclear force. It features topologically stable configurations known as instantons which cannot continuously evolve to the ground state. The topological susceptibility is a parameter that describes this stability and is predicted to vanish in physical theories, however numerical simulations find that the topological susceptibility diverges in the continuum limit. This issue has motivated the application of the …
Simulation And Optimization Of Kinematics Measurements For The Moller Parity-Violating Electron-Electron Scattering Experiment, Lauren Carver
Simulation And Optimization Of Kinematics Measurements For The Moller Parity-Violating Electron-Electron Scattering Experiment, Lauren Carver
Undergraduate Honors Theses
This report describes the optimization of the sieve collimator that will be used for the MOLLER experiment at Jefferson Laboratory. The MOLLER experiment seeks to study the parity-violating asymmetry in electron-electron elastic scattering. For this project, Monte Carlo simulations were run using a GEANT4 simulation package, which includes the main geometry of the proposed experiment, and the essential physics reaction processes. A sieve collimator was added to the simulated geometry. This collimator has pin-hole openings to select scattered electrons at certain locations (radial and azimuthal positions) corresponding to specific scattering angles (theta, and phi). Analysis of the simulated data were …
Composite Gravity In Curved Spacetime, Austin Batz
Composite Gravity In Curved Spacetime, Austin Batz
Undergraduate Honors Theses
This work presents the development of a quantum theory of gravity motivated by diffeomorphism-invariance and background-independence. A composite graviton state that satisfies the linearized Einstein’s field equations has been identified via perturbative expansion about a curved vacuum spacetime. The emergence of this gravitational interaction is discussed, as well as cancellation of tadpoles and treatment of ultraviolet divergences via dimensional regularization. In other words, the formalism of quantum field theory is used to identify a gravitational interaction as an emergent phenomenon rather than as a fundamental aspect of nature. The lattice is proposed as a candidate for a physical regulator, and …