Time without time: a stochastic clock model

We study a classical reparametrization-invariant system, in which ``time'' is not a priori defined. It consists of a nonrelativistic particle moving in five dimensions, two of which are compactified to form a torus. There, assuming a suitable potential, the internal motion is ergodic or more strongly irregular. We consider quasi-local observables which measure the system's ``change'' in a coarse-grained way. Based on this, we construct a statistical timelike parameter, particularly with the help of maximum entropy method and Fisher-Rao information metric. The emergent reparametrization-invariant ``time'' does not run smoothly but is simply related to the proper time on the average. For sufficiently low energy, the external motion is then described by a unitary quantum mechanical evolution in accordance with the Schr\"odinger equation.Comment: 18 pages; LaTeX. 4 (.ps) plus 2 (.gif) figure file

Critical temperature for first-order phase transitions in confined systems

We consider the Euclidean $D$-dimensional $-\lambda |\phi |^4+\eta |\phi |^6$ ($\lambda ,\eta >0$) model with $d$ ($d\leq D$) compactified dimensions. Introducing temperature by means of the Ginzburg--Landau prescription in the mass term of the Hamiltonian, this model can be interpreted as describing a first-order phase transition for a system in a region of the $D$-dimensional space, limited by $d$ pairs of parallel planes, orthogonal to the coordinates axis $x_1, x_2, ..., x_d$. The planes in each pair are separated by distances $L_1, L_2, ..., L_d$. We obtain an expression for the transition temperature as a function of the size of the system, $$, $i=1, 2, ..., d$. For D=3 we particularize this formula, taking $L_1=L_2=... =L_d=L$ for the physically interesting cases $d=1$ (a film), $d=2$ (an infinitely long wire having a square cross-section), and for $d=3$ (a cube). For completeness, the corresponding formulas for second-order transitions are also presented. Comparison with experimental data for superconducting films and wires shows qualitative agreement with our theoretical expressionsComment: REVTEX, 11 pages, 3 figures; to appear in Eur. Phys. Journal

Niche evolution reveals disparate signatures of speciation in the ‘great speciator’ (white‐eyes, Aves: Zosterops )

ACKNOWLEDGEMENTS J.O.E. and L.L. coordinated and secured project funding with the support from J.S.C.; we thank AT Peterson and CH Graham and two reviewers for critical feedback on earlier stages of the manuscript. The project was funded by the Research Foundation – Flanders (FWO; 1527918N & G042318N). J.O.E. received additional funds by an FWO Postdoctoral Fellowship (12G4317N). The authors declare no conflict of interest. No permits were needed to conduct the re- search presented here. DATA AVAILABILITY STATEMENT All data are available from open source platforms. Raw GBIF.org occurrence data used for this work (as accessed on 21st October 2016) can be accessed through GBIF Occurrence Download http://doi.org/10.15468/dl.erwqs6. We have deposited the prepared data used for this work on FigShare accessible through https://doi.org/10.6084/m9.figshare.13042031.v1 as well as R scripts for data analysis in a GitHub repository accessible through https://github.com/JOEngler/ZostiNicheEvol.Peer reviewedPublisher PD

5d superconformal field theories and graphs

We propose graphs, the Combined Fiber Diagrams (CFD), to characterize all 5d superconformal field theories (SCFTs) that arise as S1-reductions of 6d SCFTs. Transitions between CFDs encode mass deformations that trigger RG-flows between SCFTs. They provide a combinatorial classification of all such 5d SCFTs and encode physical information about the strongly coupled theories, like the superconformal flavor symmetry and BPS states. We consistently reproduce known results, but more importantly predict new theories and strong coupling effects in 5d SCFTs

Student Perceptions and Engagement in Video-based Learning for Microbiology Education

Online learning increases the physical distance between instructors and students and depending on the mode of delivery, it can be challenging to close this gap. To ameliorate this potential for student isolation, instructors need to communicate to students in a variety of ways, blending original online resources with synchronous interactive learning activities. During 2020, 34 lecture videos were created for a large undergraduate microbiology and immunology course offered at The University of Queensland. The teaching team applied a subset of Mayer’s multimedia learning design principles – embodiment, mixed perspectives, segmenting, signalling – to create videos featuring instructor presence, multiple presentation styles, and dynamic pacing. When compared to voice-over presentations created by automated lecture capture software, the outcomes of this design process increased student engagement in video-based learning across the 2020 and 2021 course offerings. Analysis of student perception data collected by online questionnaires and interviews revealed broad agreement with the design principles used for video-based learning. However, their value of on-screen instructor visibility, graphics, and text was variable as a result of individual preferences. Together these findings present a case study in which instructional videos were developed iteratively through the selective application of multimedia design principles and strategic adaptation of existing learning resources

Fisher Renormalization for Logarithmic Corrections

For continuous phase transitions characterized by power-law divergences, Fisher renormalization prescribes how to obtain the critical exponents for a system under constraint from their ideal counterparts. In statistical mechanics, such ideal behaviour at phase transitions is frequently modified by multiplicative logarithmic corrections. Here, Fisher renormalization for the exponents of these logarithms is developed in a general manner. As for the leading exponents, Fisher renormalization at the logarithmic level is seen to be involutory and the renormalized exponents obey the same scaling relations as their ideal analogs. The scheme is tested in lattice animals and the Yang-Lee problem at their upper critical dimensions, where predictions for logarithmic corrections are made.Comment: 10 pages, no figures. Version 2 has added reference

Relaxation and Kinetics in Scalar Field Theories

A new approach to the dynamics of relaxation and kinetics of thermalization in a scalar field theory is presented that incorporates the relevant time scales through the resummation of hard thermal loops. An alternative derivation of the kinetic equations for the ``quasiparticle'' distribution functions is obtained that allows a clear understanding of the different ``coarse graining'' approximations usually involved in a kinetic description. This method leads to a systematic perturbative expansion to obtain the kinetic equations including hard-thermal loop resummation and to an improvement including renormalization, off-shell effects and contributions that change chemical equilibrium on short time scales. As a byproduct of these methods we establish the relation between the relaxation time scale in the linearized equation of motion of the quasiparticles and the thermalization time scale of the quasiparticle distribution function in the ``relaxation time approximation''. Hard thermal loop resummation dramatically modifies the scattering rate for long wavelength modes as compared to the usual (semi) classical estimate. Relaxation and kinetics are studied both in the unbroken and broken symmetry phases of the theory. The broken symmetry phase also provides the setting to obtain the contribution to the kinetic equations from processes that involve decay of a heavy scalar into light scalar particles in the medium.Comment: 28 pages, revtex 3.0, two figures available upon reques