Quasinormal modes in kink excitations and kink-antikink interactions: a toy model

We study excitations and collisions of kinks in a scalar field theory where the potential has two minima with $Z_2$ symmetry. The field potential is designed to create a square well potential in the stability equation of the kink excitations. The stability equation is analogous to the Schr\"{o}dinger equation, and therefore we use quantum mechanics techniques to study the system. We modify the square well potential continuously, which allows the excitation to tunnel and consequently turns the normal modes of the kink into quasinormal modes. We study the effect of this transition, leading to energy leak, on isolated kink excitations. Finally, we investigate kink-antikink collisions and the resulting scaling and fractal structure of the resonance windows considering both normal and quasinormal modes and compare the results.Comment: 23 pages, 11 figure

Collisions between kinks with long-range tails: a simple and efficient method

We construct initial configurations for the scattering between kinks with long-range tails. For this purpose, we exploit kink solutions in the presence of BPS-preserving impurities. This approach offers a highly efficient method and effortless implementation with a negligible computational cost. Our algorithm has a much smaller complexity than the usual minimization method, becoming more than a hundred times faster in some scenarios. Consequently, conducting kink-antikink simulations becomes remarkably straightforward

COMBATING HEGEMONIC DISCOURSE IN AN ONLINE MULTICULTURAL LEADERSHIP COURSE: A NARRATIVE STUDY OF AN INSTRUCTOR AND STUDENT WORKING AT TANDEM FOR SOCIAL JUSTICE

This narrative study examines hegemonic discourse in an online multicultural leadership course by translating e-narrative analysis findings into implications for social justice and recommendations for andragogical strategies. These strategies specifically address hegemonic discourse within an online educational environment. The setting for this article is a graduate level class in Multicultural Leadership geared toward Masters’ students in an educational leadership program. Through the e-narrative analysis, four themes emerged that characterized the hegemonic discourse: rejecting social justice; wooing white privilege; he oppressive “other,” and telling it straight. Based on the findings and implications surrounding the research questions, four andragogical strategies were recommended: engaging in moral conversations; adopting bilateral teaching tools; strategizing for collaborative alliances; and enabling emblematic change

The missing dwarf galaxies of the Local Group

We study the Local Group (LG) dwarf galaxy population predicted by the APOSTLE ΛCDM cosmological hydrodynamics simulations. These indicate that: (i) the total mass within 3 Mpc of the Milky Way-Andromeda midpoint (M3Mpc) typically exceeds ∼3 times the sum of the virial masses (M200crit) of the two primaries and (ii) the dwarf galaxy formation efficiency per unit mass is uniform throughout the volume. This suggests that the satellite population within the virial radii of the Milky Way and Andromeda should make up fewer than one third of all LG dwarfs within 3 Mpc. This is consistent with the fraction of observed LG galaxies with stellar mass M* > 107 M⊙ that are satellites (12 out of 42; i.e., 28 per cent). For the APOSTLE galaxy mass-halo mass relation, the total number of such galaxies further suggests a LG mass of M3Mpc ∼ 1013 M⊙. At lower galaxy masses, however, the observed satellite fraction is substantially higher (42 per cent for M* > 105 M⊙). If this is due to incompleteness in the field sample, then ∼50 dwarf galaxies at least as massive as the Draco dwarf spheroidal must be missing from the current LG field dwarf inventory. The incompleteness interpretation is supported by the pronounced flattening of the LG luminosity function below M* ∼ 107 M⊙, and by the scarcity of low-surface brightness LG field galaxies compared to satellites. The simulations indicate that most missing dwarfs should lie near the virial boundaries of the two LG primaries, and predict a trove of nearby dwarfs that await discovery by upcoming wide-field imaging surveys

Wavefront correction with a ferrofluid deformable mirror: experimental results and recent developments

We present the research status of a deformable mirror made of a magnetic liquid whose surface is actuated by a triangular array of small current carrying coils. We demonstrate that the mirror can correct a 11 microns low order aberrated wavefront to a residual RMS wavefront error 0.05 microns. Recent developments show that these deformable mirrors can reach a frequency response of several hundred hertz. A new method for linearizing the response of these mirrors is also presented.Comment: To appear in "Ground-based and Airborne Instrumentation for Astronomy II" SPIE conference, Marseille, 23-28 June 200