Differential Light Shift Cancellation in a Magnetic-Field-Insensitive Transition of 87^{87}Rb

We demonstrate near-complete cancellation of the differential light shift of a two-photon magnetic-field-insensitive microwave hyperfine (clock) transition in $^{87}$Rb atoms trapped in an optical lattice. Up to $95(2)$ of the differential light shift is canceled while maintaining magnetic-field insensitivity. This technique should have applications in quantum information and frequency metrology.Comment: 5 pages, 4 figure

Conditional probabilities with Dirac observables and the problem of time in quantum gravity

We combine the "evolving constants" approach to the construction of observables in canonical quantum gravity with the Page--Wootters formulation of quantum mechanics with a relational time for generally covariant systems. This overcomes the objections levied by Kucha\v{r} against the latter formalism. The construction is formulated entirely in terms of Dirac observables, avoiding in all cases the physical observation of quantities that do not belong in the physical Hilbert space. We work out explicitly the example of the parameterized particle, including the calculation of the propagator. The resulting theory also predicts a fundamental mechanism of decoherence.Comment: 4 pages, no figures, RevTe

The gravitational S-matrix

We investigate the hypothesized existence of an S-matrix for gravity, and some of its expected general properties. We first discuss basic questions regarding existence of such a matrix, including those of infrared divergences and description of asymptotic states. Distinct scattering behavior occurs in the Born, eikonal, and strong gravity regimes, and we describe aspects of both the partial wave and momentum space amplitudes, and their analytic properties, from these regimes. Classically the strong gravity region would be dominated by formation of black holes, and we assume its unitary quantum dynamics is described by corresponding resonances. Masslessness limits some powerful methods and results that apply to massive theories, though a continuation path implying crossing symmetry plausibly still exists. Physical properties of gravity suggest nonpolynomial amplitudes, although crossing and causality constrain (with modest assumptions) this nonpolynomial behavior, particularly requiring a polynomial bound in complex s at fixed physical momentum transfer. We explore the hypothesis that such behavior corresponds to a nonlocality intrinsic to gravity, but consistent with unitarity, analyticity, crossing, and causality.Comment: 46 pages, 10 figure

Fundamental decoherence from relational time in discrete quantum gravity: Galilean covariance

We have recently argued that if one introduces a relational time in quantum mechanics and quantum gravity, the resulting quantum theory is such that pure states evolve into mixed states. The rate at which states decohere depends on the energy of the states. There is therefore the question of how this can be reconciled with Galilean invariance. More generally, since the relational description is based on objects that are not Dirac observables, the issue of covariance is of importance in the formalism as a whole. In this note we work out an explicit example of a totally constrained, generally covariant system of non-relativistic particles that shows that the formula for the relational conditional probability is a Galilean scalar and therefore the decoherence rate is invariant.Comment: 10 pages, RevTe

Multicomponent reaction-diffusion processes on complex networks

We study the reaction-diffusion process $A + B \to \emptyset$ on uncorrelated scale-free networks analytically. By a mean-field ansatz we derive analytical expressions for the particle pair-correlations and the particle density. Expressing the time evolution of the particle density in terms of the instantaneous particle pair-correlations, we determine analytically the `jamming' effect which arises in the case of multicomponent, pair-wise reactions. Comparing the relevant terms within the differential equation for the particle density, we find that the `jamming' effect diminishes in the long-time, low-density limit. This even holds true for the hubs of the network, despite that the hubs dynamically attract the particles.Comment: 8 pages, 6 figure

Pair Connectedness and Shortest Path Scaling in Critical Percolation

We present high statistics data on the distribution of shortest path lengths between two near-by points on the same cluster at the percolation threshold. Our data are based on a new and very efficient algorithm. For $d=2$ they clearly disprove a recent conjecture by M. Porto et al., Phys. Rev. {\bf E 58}, R5205 (1998). Our data also provide upper bounds on the probability that two near-by points are on different infinite clusters.Comment: 7 pages, including 4 postscript figure

Beyond employment: Lower-income participants’ experiences in a healthcare training program for medical assistants, pharmacy technicians, and certified nursing assistants

Purpose: The purpose of this study was to gain a deeper understanding of participant experiences in a healthcare training program for medical assistants, pharmacy technicians, and certified nursing assistants in areas beyond employment procurement or retention. During the year 2020, employment rates decreased and the cost of living increased. Those changes ultimately put lower-income populations at risk for not meeting the basic needs of life, as it became increasingly more difficult to obtain an adequately paying job. Healthcare training programs for lower income individuals allow for participants to gain the appropriate knowledge and experience required for working in the healthcare industry while also providing them necessary skills and confidence for securing and maintaining employment. While the primary objective of the Genesis Center Healthcare Training Program was to increase employment rates, this study found the program substantially contributed to participant’s lives in many ways that will contribute to their overall life satisfaction, financial well-being, and mental wellness for many years. Method: This current research adds to existing literature by utilizing a mixed methods sequential exploratory strategy that analyzes quantitative survey data (n=51) and qualitative data from phone interviews with program participants (n=19). Results: Findings from this study provide evidence that healthcare training programs for lower income populations may improve participant lives by increasing financial well-being and financial capability. Participants also reported enhanced opportunities, increased motivation, and improved mental health following participation. Conclusion: Employment programs for future allied health professionals targeting lower income populations should ensure that financial coaching and additional supports are included in their protocols. Future research on these types of training programs should include pre/post measures and ideally experimental design procedures using standardized measures for life satisfaction, financial well-being, and mental health