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- Genre: Doctoral Dissertation
- Member of: Theses and Dissertations
Description
Monte Carlo methods often used in nuclear physics, such as auxiliary field diffusion Monte Carlo and Green's function Monte Carlo, have typically relied on phenomenological local real-space potentials containing as few derivatives as possible, such as the Argonne-Urbana family of interactions, to make sampling simple and efficient. Basis set methods such as no-core shell model or coupled-cluster techniques typically use softer non-local potentials because of their more rapid convergence with basis set size. These non-local potentials are typically defined in momentum space and are often based on effective field theory. Comparisons of the results of the two types of methods are complicated by the use of different potentials. This thesis discusses progress made in using such non-local potentials in quantum Monte Carlo calculations of light nuclei. In particular, it shows methods for evaluating the real-space, imaginary-time propagators needed to perform quantum Monte Carlo calculations using non-local potentials and universality properties of these propagators, how to formulate a good trial wave function for non-local potentials, and how to perform a "one-step" Green's function Monte Carlo calculation for non-local potentials.
ContributorsLynn, Joel E (Author) / Schmidt, Kevin E (Thesis advisor) / Alarcon, Ricardo (Committee member) / Lebed, Richard (Committee member) / Shovkovy, Igor (Committee member) / Shumway, John (Committee member) / Arizona State University (Publisher)
Created2013
Description
In the first part of this thesis, we use the generalized Landau-level represen-
tation to study the effect of screening on the properties of the graphene quantum Hall states with integer filling factors. The analysis is performed in the low-energy Dirac model in the mean-field approximation, in which the long-range Coulomb in- teraction is modified by the one-loop static screening effects. The solutions demon- strate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The results of the temperature dependence of the energy gaps mimic well the temperature dependence of the activation energies measured in experiment. The Landau-level running of the quasiparticle dynamical parameters could be tested via optical studies of the integer quantum Hall states.
In the second part, by using the generalized Landau-level representation, we study the interaction induced chiral asymmetry in cold QED plasma beyond the weak-field approximation. The chiral shift and the parity-even chiral chemical potential function are obtained numerically and are found peaking near the Fermi surface and increases and decreases with the Landau level index, respectively. The results are used to quantify the chiral asymmetry of the Fermi surface in dense QED matter. The chiral asymmetry appears to be rather small even in the strongest mag- netic fields and at the highest stellar densities. However, the analogous asymmetry can be substantial in the case of dense quark matter.
tation to study the effect of screening on the properties of the graphene quantum Hall states with integer filling factors. The analysis is performed in the low-energy Dirac model in the mean-field approximation, in which the long-range Coulomb in- teraction is modified by the one-loop static screening effects. The solutions demon- strate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The results of the temperature dependence of the energy gaps mimic well the temperature dependence of the activation energies measured in experiment. The Landau-level running of the quasiparticle dynamical parameters could be tested via optical studies of the integer quantum Hall states.
In the second part, by using the generalized Landau-level representation, we study the interaction induced chiral asymmetry in cold QED plasma beyond the weak-field approximation. The chiral shift and the parity-even chiral chemical potential function are obtained numerically and are found peaking near the Fermi surface and increases and decreases with the Landau level index, respectively. The results are used to quantify the chiral asymmetry of the Fermi surface in dense QED matter. The chiral asymmetry appears to be rather small even in the strongest mag- netic fields and at the highest stellar densities. However, the analogous asymmetry can be substantial in the case of dense quark matter.
ContributorsXia, Lifang, Ph.D (Author) / Shovkovy, Igor (Thesis advisor) / Lebed, Richard (Committee member) / Schmidt, Kevin (Committee member) / Damien, Easson (Committee member) / Arizona State University (Publisher)
Created2016
Description
For this project, the diffuse supernova neutrino background (DSNB) has been calculated based on the recent direct supernova rate measurements and neutrino spectrum from SN1987A. The estimated diffuse electron antineutrino flux is ∼ 0.10 – 0.59 /cm2/s at 99% confidence level, which is 5 times lower than the Super-Kamiokande 2012 upper limit of 3.0 /cm2/s, above energy threshold of 17.3 MeV. With a Megaton scale water detector, 40 events could be detected above the threshold per year. In addition, the detectability of neutrino bursts from direct black hole forming collapses (failed supernovae) at Megaton detectors is calculated. These neutrino bursts are energetic and with short time duration, ∼ 1s. They could be identified by the time coincidence of N ≥2 or N ≥3 events within 1s time window from nearby (4 – 5 Mpc) failed supernovae. The detection rate of these neutrino bursts could get up to one per decade. This is a realistic way to detect a failed supernova and gives a promising method for studying the physics of direct black hole formation mechanism. Finally, the absorption of ultra high energy (UHE) neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel, is discussed. Results are applied to serval models of UHE neutrino sources. Suppression effects are strong for sources that extend beyond z ∼ 10. This provides a fascinating probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10 – 100. Ultimately this research will examine the detectability of DSNB, neutrino bursts from failed supernovae and absorption effects in the neutrino spectrum.
ContributorsYang, Lili, 1970- (Author) / Lunardini, Cecilia (Thesis advisor) / Alarcon, Ricardo (Committee member) / Shovkovy, Igor (Committee member) / Timmes, Francis (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
The GlueX experiment housed in Hall D of the Thomas Jefferson National Laboratory was created to map the light meson spectrum in order to contribute to the Standard Model of particle physics by strengthening our understanding of the strong interaction. GlueX is a medium-energy photoproduction experiment that utilizes a linearly polarized photon beam to create hadronic forms of matter. By mapping the light meson spectrum, the GlueX collaboration hopes to identify meson states forbidden by the Constituent Quark Model. As a main research objective, the GlueX collaboration is searching for hybrid $q\bar{q}g$ meson states that exhibit exotic quantum numbers. One hybrid meson candidate is the $\eta'_1$, which is predicted to decay to $K^\ast\bar{K}$ and have a mass near $2.3~\mathrm{GeV}$ (\citeauthor{qn_exotic_status}, \citeyear{qn_exotic_status}; \citeauthor{hybrid_mesons}, \citeyear{hybrid_mesons}). At this time, very few meson states have been identified in the $2.0~\mathrm{GeV}$ mass region. This dearth of evidence for existing states requires any tool developed to search for meson states above $2.0~\mathrm{GeV}$ must be verified by looking at known meson states. In order to search for the $\eta'_1$ hybrid meson candidate in $\gamma p \rightarrow pK^+K^-\gamma\gamma$ events, meson states decaying $K^\ast\bar{K}$ that contribute to the low mass region must be identified, defined in this document as particles having masses between $1400$ and $1600~\mathrm{MeV}$. Identifying what meson states exist in the low mass region is also critical to mapping the light meson spectrum and determining the quark-gluonic content of those meson states. The results of a partial wave analysis (PWA) of $\gamma p \rightarrow pX$ where $X\rightarrow K^\ast\bar{K}$ from $\gamma p \rightarrow pK^+K^-\gamma\gamma$ events in GlueX are presented. In the $J=0$ invariant mass distribution, the $\eta(1405)$ and $\eta(1475)$ are identified, adding to the debate as to whether two pseudoscalar mesons exist in the low mass region. For the $J=1$ distribution, the $f_1(1420)$ and $f_1(1510)$ axial vector mesons are seen, where the former helps further elaborate on the $E\iota$ puzzle of the twentieth century \citep{E_iota_puzzle}. With respect to the controversy of meson states in the low mass region, evidence for the existence of the $f_2(1430)$ meson is strengthened in the $J=2$ distribution, and the $f'_2(1525)$ state is seen. This work lays a foundation for the ASU Meson Physics Group to continue a wider search for hybrid mesons in the $\gamma p \rightarrow pK^+K^-\gamma\gamma$ reaction topology.
ContributorsCole, Sebastian Miles (Author) / Dugger, Michael (Thesis advisor) / Ritchie, Barry (Committee member) / Alarcon, Ricardo (Committee member) / Shovkovy, Igor (Committee member) / Arizona State University (Publisher)
Created2021