PT\mathcal{PT}-breaking threshold in spatially asymmetric Aubry-Andre Harper models: hidden symmetry and topological states

Aubry-Andre Harper (AAH) lattice models, characterized by reflection-asymmetric, sinusoidally varying nearest-neighbor tunneling profile, are well-known for their topological properties. We consider the fate of such models in the presence of balanced gain and loss potentials $\pm i\gamma$ located at reflection-symmetric sites. We predict that these models have a finite $\mathcal{PT}$ breaking threshold only for {\it specific locations} of the gain-loss potential, and uncover a hidden symmetry that is instrumental to the finite threshold strength. We also show that the topological edge-states remain robust in the $\mathcal{PT}$-symmetry broken phase. Our predictions substantially broaden the possible realizations of a $\mathcal{PT}$-symmetric system.Comment: 8 pages, 5 figure

Student Engagement and Equitable Student Learning Outcomes

Student engagement is consistently shown by research to be a critical component of student learning. An opportunity to link variables of perceived student engagement, perceived student-teacher relationship and clarity, an in-person learning format, and a remote learning format presented itself when, in March of 2020, all Illinois public schools were mandated by Governor J.B. Pritzker to teach in a fully remote structure due to the COVID-19 pandemic. Student survey data results were examined using Wagner et al’s (2006) 4 C’s model to determine if there were statistically significant differences among student engagement and student-teacher relationships when compared across in-person and remote learning environments. Implications for educators are posed to inform future practice

Assessment of fish populations and habitat on Oculina Bank, a deep-sea coral marine protected area off eastern Florida

A portion of the Oculina Bank located off eastern Florida is a marine protected area (MPA) preserved for its dense populations of the ivory tree coral (Oculina varicosa), which provides important habitat for fish. Surveys of fish assemblages and benthic habitat were conducted inside and outside the MPA in 2003 and 2005 by using remotely operated vehicle video transects and digital still imagery. Fish species composition, biodiversity, and grouper densities were used to determine whether O. varicosa forms an essential habitat compared to other structure-forming habitats and to examine the effectiveness of the MPA. Multivariate analyses indicated no differences in fish assemblages or biodiversity among hardbottom habitat types and grouper densities were highest among the most complex habitats; however the higher densities were not exclusive to coral habitat. Therefore, we conclude that O. varicosa was functionally equivalent to other hardbottom habitats. Even though fish assemblages were not different among management areas, biodiversity and grouper densities were higher inside the MPA compared to outside. The percentage of intact coral was also higher inside the MPA. These results provide initial evidence demonstrating effectiveness of the MPA for restoring reef fish and their habitat. This is the first study to compare reef fish populations on O. varicosa with other structure-forming reef habitats and also the first to examine the effectiveness of the MPA for restoring fish populations and live reef cover

Sublattice signatures of transitions in a PT -symmetric dimer lattice

Lattice models with non-hermitian, parity and time-reversal (PTPT) symmetric Hamiltonians, realized most readily in coupled optical systems, have been intensely studied in the past few years. A PTPT-symmetric dimer lattice consists of dimers with intra-dimer coupling νν, inter-dimer coupling ν′ν′, and balanced gain and loss potentials ±iγ±iγ within each dimer. This model undergoes two independent transitions, namely a PTPT-breaking transition and a topological transition. We numerically and analytically investigate the signatures of these transitions in the time-evolution of states that are initially localized on the gain-site or the loss-site

Passive parity-time-symmetry-breaking transitions without exceptional points in dissipative photonic systems

Over the past decade, parity-time (PT)-symmetric Hamiltonians have been experimentally realized in classical, optical settings with balanced gain and loss, or in quantum systems with localized loss. In both realizations, the PT-symmetry-breaking transition occurs at the exceptional point of the non-Hermitian Hamiltonian, where its eigenvalues and the corresponding eigenvectors both coincide. Here, we show that in lossy systems, the PT transition is a phenomenon that broadly occurs without an attendant exceptional point, and is driven by the potential asymmetry between the neutral and the lossy regions. With experimentally realizable quantum models in mind, we investigate dimer and trimer waveguide configurations with one lossy waveguide. We validate the tight-binding model results by using the beam-propagation-method analysis. Our results pave a robust way toward studying the interplay between passive PT transitions and quantum effects in dissipative photonic configurations

Managerial Valuation of Applicant Credentials and Personal Traits in Hiring Decisions

We study how managers value applicant credentials and personal traits in hiring decisions. Using the ordered probit model, we confirm previous results – managers rank applicant traits higher than credentials. However, we also uncover patterns not previously observed – managerial valuations of some of these characteristics are dependent on managers' perception of the overall state of the economy, on firm and immediate workplace characteristics, and on managers' personal characteristics. Manager valuations of credentials vary with a large number of factors; this is not so for applicant personal traits. This is not surprising as most managers view the five traits considered "as extremely important."personality, credentials, hiring practices, ordered probit

The Ursinus Weekly, February 12, 1945

Rev. A. Z. Schellhase to address grads at exercises Feb. 24 • Students aid scrap drive as everybody gets little white notes • Jenkins excels as murderer in Night Must Fall production • Navy students receive orders to new units • \u27944\u27 tea honors new Rosicrucians • T. Kandahl speaks on postwar Norway • Students to present recital on Thursday • Mermaids to form new campus club • WSGA is frowning on dungarees, slacks for campus wear - (for P. E. classes, okay) • Get in the swing with spring, young man, and send your secret love a valentine • Partial schedule announced for Ruby organization photographs • Oddities of Europe: Lietenstein • Ursinus wrestlers throw Bloomsburg, 26-6, on loser\u27s mats for second consecutive win • Snell\u27s belles tie Albright basketball team in home game; win victory over Rosemont team, 24-18, in game Saturday • Bears succumb to Albright lions, 57-37 • Rosemont wins close Jayvee contest, 28-26 • Air Station downs bears in exciting game, 53-47 • Vespers\u27 topic is finding oneself\u27https://digitalcommons.ursinus.edu/weekly/1699/thumbnail.jp