Browsing by Subject "Theoretical physics"

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    Classical and quantum aspects of non-linear sigma models with a squashed sphere target space
    (2022-07) Schubring, Daniel
    Various aspects of non-linear sigma models with an SU(N) x U(1) symmetric target space are considered. In the case N=2, three-dimensional topological defects are discussed which are relevant for frustrated magnetic systems and which may offer a new perspective on the Skyrme model. An apparent discrepancy between the large N expansion and the weak coupling expansion noted earlier in the literature is reviewed and clarified. A systematic approach to the operator product expansion at sub-leading order in large N is developed and the spinon two-point function is expanded as a trans-series in which all ambiguities in the Borel plane are shown to cancel.
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    Light-Front Coupled-Cluster Method In Phi-Four Field Theory
    (2016-05) Elliott, Blair
    The light-front coupled-cluster (LFCC) method is investigated as an alternative method for determining mass eigenvalues in quantum field theories. Traditional methods create an infinite set of coupled equations, and solutions are then approximated by truncating the system of equations and computationally determining the wavefunctions. Instead, the use of an exponential operator to construct the basis set of Fock states allows for generatingthefullsetofstates,maintainingnormalization,whilestillbeingabletocreate a finite problem for the wavefunctions. Application of the LFCC method to phi-4 field theoryisshowntoproducesolutionsingoodagreementwithothermethods. Inparticular, we obtain the masses of the lowest eigenstate as a function of the coupling strength and study the behavior of the wavefunction components. The calculation was facilitated by the construction of a new type of fully symmetric multivariate polynomials used as basis functions for the numerical solution of the LFCC equations. The approximations made for the purpose of this investigation prevented the full scope of symmetry breaking from being observed, but the foundation has been established for future work to apply the LFCC method to symmetry breaking in phi-4 field theory.