Log-Concave Duality in Estimation and Control

In this paper we generalize the estimation-control duality that exists in the linear-quadratic-Gaussian setting. We extend this duality to maximum a posteriori estimation of the system's state, where the measurement and dynamical system noise are independent log-concave random variables. More generally, we show that a problem which induces a convex penalty on noise terms will have a dual control problem. We provide conditions for strong duality to hold, and then prove relaxed conditions for the piecewise linear-quadratic case. The results have applications in estimation problems with nonsmooth densities, such as log-concave maximum likelihood densities. We conclude with an example reconstructing optimal estimates from solutions to the dual control problem, which has implications for sharing solution methods between the two types of problems

Restoring the sting to metric preheating

The relative growth of field and metric perturbations during preheating is sensitive to initial conditions set in the preceding inflationary phase. Recent work suggests this may protect super-Hubble metric perturbations from resonant amplification during preheating. We show that this possibility is fragile and sensitive to the specific form of the interactions between the inflaton and other fields. The suppression is naturally absent in two classes of preheating in which either (1) the vacua of the non-inflaton fields during inflation are deformed away from the origin, or (2) the effective masses of non-inflaton fields during inflation are small but during preheating are large. Unlike the simple toy model of a $g^2 \phi^2 \chi^2$ coupling, most realistic particle physics models contain these other features. Moreover, they generically lead to both adiabatic and isocurvature modes and non-Gaussian scars on super-Hubble scales. Large-scale coherent magnetic fields may also appear naturally.Comment: 6 pages, 3 ps figures, RevTex, revised discussion of backreaction and new figure. To appear Phys. Rev. D (Rapid Communication

A late-time transition in the equation of state versus Lambda-CDM

We study a model of the dark energy which exhibits a rapid change in its equation of state w(z), such as occurs in vacuum metamorphosis. We compare the model predictions with CMB, large scale structure and supernova data and show that a late-time transition is marginally preferred over standard Lambda-CDM.Comment: 4 pages, 1 figure, to appear in the proceedings of XXXVIIth Rencontres de Moriond, "The Cosmological Model", March 200

Spin Readout Techniques of the Nitrogen-Vacancy Center in Diamond

The diamond nitrogen-vacancy (NV) center is a leading platform for quantum information science due to its optical addressability and room-temperature spin coherence. However, measurements of the NV center's spin state typically require averaging over many cycles to overcome noise. Here, we review several approaches to improve the readout performance and highlight future avenues of research that could enable single-shot electron-spin readout at room temperature.Comment: 21 pages, 7 figure

The development of the head direction system before eye opening in the rat.

Head direction (HD) cells are neurons found in the hippocampal formation and connected areas that fire as a function of an animal's directional orientation relative to its environment. They integrate self-motion and environmental sensory information to update directional heading. Visual landmarks, in particular, exert strong control over the preferred direction of HD cell firing. The HD signal has previously been shown to appear adult-like as early as postnatal day 16 (P16) in the rat pup, just after eye opening and coinciding with the first spontaneous exploration of its environment. In order to determine whether the HD circuit can begin its organization prior to the onset of patterned vision, we recorded from the anterodorsal thalamic nucleus (ADN) and its postsynaptic target in the hippocampal formation, the dorsal pre-subiculum (PrSd), before and after eye opening in pre-weanling rats. We find that HD cells can be recorded at the earliest age sampled (P12), several days before eye opening. However, this early HD signal displays low directional information content and lacks stability both within and across trials. Following eye opening, the HD system matures rapidly, as more cells exhibit directional firing, and the quality and reliability of the directional signal improves dramatically. Cue-rotation experiments show that a prominent visual landmark is able to control HD responses within 24 hr of eye opening. Together, the results suggest that the directional network can be organized independently of visual spatial information while demonstrating the importance of patterned vision for accurate and reliable orientation in space

Ctrl+Alt+Delete : the changing landscape of the uncanny valley and the fear of second loss

We are living in a digital era where ubiquitous social media are becoming part of the everyday lives of many. These social media platforms were designed for the living; however an estimated 8000 Facebook members die daily. It is therefore no surprise that the phenomena of how social media platforms are adopted to discuss death dying and grieving have become a growing area of research across numerous disciplines. Using qualitative methods, this article adds to and moves beyond existing research by focusing on the creation and inheritance of Facebook pages, thanablogs, posthumous chatbots, posthumous messages and posthumous avatars, to explore whether digital afterlives enabled by the Internet affect how people grieve. In order to examine how these messages and memories are experienced this study used in-depth qualitative interviews with participants from 3 distinct areas: Digital Creators (DC), Digital Inheritors (DI) and Service Providers (SP) the findings presented here explore three emerging themes (1) the link between comfort and control (2) the changing landscape of the uncanny valley and (3) the fear of ‘second loss’

Who wants to live forever? : living, dying and grieving in our digital society

Almost ubiquitous hardware technology, such as smart phones, ensures that social networking sites are part of users’ everyday norms and routines. However, some are now using these new communication technologies to deal with the issues of death, dying and grief. With the hope of being able to create digital memories to leave behind for future generations, the opportunity to “live on” and become digitally immortal is seen as empowering to some: but what about those left behind? Through a review of the current literature exploring how social media are being used as a new space to grieve and mourn, this paper contributes to the literature by arguing for the need for clarity in the lexicon being used by thanatologists and other disciplines. Furthermore, it introduces the term “digital zombie” to describe the dead who remain “alive” in our digital society. The paper concludes by joining the call for further research into the nascent phenomena being generated by human-computer interaction

Small farm family program series : homemade cottage cheese (1988)

Reprint 7/88/5M