title: Searching for rational bubble footprints in the Singaporean and Indonesian stock markets

authors: Nartea, Gilbert V.

abstract: We re-examine the presence of rational speculative bubbles in the Singaporean and Indonesian stock markets in light of contradictory results in the literature. We employ a mix of descriptive statistics, explosiveness tests and duration dependence tests for an expanded dataset from 1970 to 2013 that covers at least two suspected bubble episodes - the 1997 Asian Financial Crisis (AFC) and the Global Financial Crisis (GFC). We find bubble footprints in Singapore and Indonesia using descriptive statistics and explosiveness tests. However, we find no evidence of rational bubbles in Singapore using the duration dependence test. On the other hand, in Indonesia we find evidence of rational bubbles in weekly but not in monthly data. Our results indicate that the duration dependence test could be sensitive to data frequency suggesting that the duration dependence test results are not always conclusive and that it should be used in conjunction with other tests.

text: Searching for rational bubble footprints in the Singaporean and Indonesian stock markets We re-examine the presence of rational speculative bubbles in the Singaporean and Indonesian stock markets in light of contradictory results in the literature. We employ a mix of descriptive statistics, explosiveness tests and duration dependence tests for an expanded dataset from 1970 to 2013 that covers at least two suspected bubble episodes - the 1997 Asian Financial Crisis (AFC) and the Global Financial Crisis (GFC). We find bubble footprints in Singapore and Indonesia using descriptive statistics and explosiveness tests. However, we find no evidence of rational bubbles in Singapore using the duration dependence test. On the other hand, in Indonesia we find evidence of rational bubbles in weekly but not in monthly data. Our results indicate that the duration dependence test could be sensitive to data frequency suggesting that the duration dependence test results are not always conclusive and that it should be used in conjunction with other tests.

year: 2017

title: Linear theory of fast reconnection at an X-type neutral point

authors: Craig, Ian J.D.

abstract: A linear theory is developed for the dissipation of the free magnetic energy in small disturbances imposed on the potential field of an X-type neutral point. An eigenmode analysis, using cylindrical coordinates centered on the neutral point, extends the work of Craig & McClymont (1991) to include non-azimuthally symmetric perturbations on the flux function. We demonstrate that all physically significant disturbances, both reconnective and nonreconnective, decay resistively on a "fast" time scale ∼|ln η|, where η is the nondimensional resistivity. Thus resistive diffusion is remarkably effective as a dissipation mechanism for all classes of perturbation not only those modes which induce changes in the field topology. The fundamental reason for the fast dissipation is the focusing of wave energy onto the neutral point by the gradient in Alfvén speed. This occurs for all types of disturbances launched from the outer boundary, but reconnective modes propagate purely radially while nonreconnective modes correspond to waves with an azimuthal motion and a smaller wave speed in the radial direction. Dissipation of reconnective disturbances takes place in a diffusion region of diameter ≈η1/2 around the neutral point, on a time scale ∝ |ln η|2, but nonreconnective perturbations decay before penetrating to the neutral point, because of the increased path lengths due to their azimuthal motion. These modes release their energy in an annulus of radius ≈[(m3/ 4k)η]1/2, where m and k are azimuthal and radial wavenumbers: because of their longer transit time, nonreconnective waves decay on a |ln η|3 time scale. We conclude by discussing the significance of the linear theory within the general context of steady state and dynamic reconnection studies. It is pointed out that, dynamically, disturbances can be expected to focus explosively in the vicinity of the neutral point. This suggests the formation of a "flux pile-up" current layer in which the bulk of the magnetic energy is released as heat rather than kinetic energy of mass motion.

text: Linear theory of fast reconnection at an X-type neutral point A linear theory is developed for the dissipation of the free magnetic energy in small disturbances imposed on the potential field of an X-type neutral point. An eigenmode analysis, using cylindrical coordinates centered on the neutral point, extends the work of Craig & McClymont (1991) to include non-azimuthally symmetric perturbations on the flux function. We demonstrate that all physically significant disturbances, both reconnective and nonreconnective, decay resistively on a "fast" time scale ∼|ln η|, where η is the nondimensional resistivity. Thus resistive diffusion is remarkably effective as a dissipation mechanism for all classes of perturbation not only those modes which induce changes in the field topology. The fundamental reason for the fast dissipation is the focusing of wave energy onto the neutral point by the gradient in Alfvén speed. This occurs for all types of disturbances launched from the outer boundary, but reconnective modes propagate purely radially while nonreconnective modes correspond to waves with an azimuthal motion and a smaller wave speed in the radial direction. Dissipation of reconnective disturbances takes place in a diffusion region of diameter ≈η1/2 around the neutral point, on a time scale ∝ |ln η|2, but nonreconnective perturbations decay before penetrating to the neutral point, because of the increased path lengths due to their azimuthal motion. These modes release their energy in an annulus of radius ≈[(m3/ 4k)η]1/2, where m and k are azimuthal and radial wavenumbers: because of their longer transit time, nonreconnective waves decay on a |ln η|3 time scale. We conclude by discussing the significance of the linear theory within the general context of steady state and dynamic reconnection studies. It is pointed out that, dynamically, disturbances can be expected to focus explosively in the vicinity of the neutral point. This suggests the formation of a "flux pile-up" current layer in which the bulk of the magnetic energy is released as heat rather than kinetic energy of mass motion.

year: 1993

title: Arts Festival: 'Moonwalking Backwards Into The Future: "Poi E", Music Video and Documentary'

authors: Perrott, Lisa

subjects: Art

abstract: Research presentation - an audiovisual presentation drawing upon my published research (book chapter: 'Moonwalking Backwards Into The Future: "Poi E", Music Video and Documentary'). This presentation presented a Matuaranga Maori perspective of the temporal travels of music video and documentary, framed by the concept of whakapap. This presentation took place as part of a panel of 4 presenters who represented Te Kura Toi at the Arts Festival during the University of Waikato Open Day, 2023. This was an oral presentation, which included projected slides and videos from a PPT presentation. The audience included prospective students, their teachers and family members, community members, and current students and academic staff from the University of Waikato. My presentation was documented and photographed.

text: Arts Festival: 'Moonwalking Backwards Into The Future: "Poi E", Music Video and Documentary' Research presentation - an audiovisual presentation drawing upon my published research (book chapter: 'Moonwalking Backwards Into The Future: "Poi E", Music Video and Documentary'). This presentation presented a Matuaranga Maori perspective of the temporal travels of music video and documentary, framed by the concept of whakapap. This presentation took place as part of a panel of 4 presenters who represented Te Kura Toi at the Arts Festival during the University of Waikato Open Day, 2023. This was an oral presentation, which included projected slides and videos from a PPT presentation. The audience included prospective students, their teachers and family members, community members, and current students and academic staff from the University of Waikato. My presentation was documented and photographed.

year: 2023-05-26