Quantum widening of CDT universe

The physical phase of Causal Dynamical Triangulations (CDT) is known to be described by an effective, one-dimensional action in which three-volumes of the underlying foliation of the full CDT play a role of the sole degrees of freedom. Here we map this effective description onto a statistical-physics model of particles distributed on 1d lattice, with site occupation numbers corresponding to the three-volumes. We identify the emergence of the quantum de-Sitter universe observed in CDT with the condensation transition known from similar statistical models. Our model correctly reproduces the shape of the quantum universe and allows us to analytically determine quantum corrections to the size of the universe. We also investigate the phase structure of the model and show that it reproduces all three phases observed in computer simulations of CDT. In addition, we predict that two other phases may exists, depending on the exact form of the discretised effective action and boundary conditions. We calculate various quantities such as the distribution of three-volumes in our model and discuss how they can be compared with CDT.Comment: 19 pages, 13 figure

Bionic Hand Team

The project goal is to design a low cost prosthetic hand controlled by a PIC18F25K22 microcontroller that will allow the user to perform simple tasks that require a greater dexterity than what a mechanical prosthetic can deliver. The digits of the prosthetic will be contracted or relaxed using electromyographic signals measured by electrodes on a single muscle group. Grip settings, which define the open and closed position for each digit, are used for the control of the hand. This allows common actions, such as grabbing a door handle or pencil, to be accomplished with readings from one muscle group instead of requiring a muscle group for each digit. Additionally, the use of pressure sensors on the fingers provide feedback to the user, and prevent the system from damaging itself by forcing the digits into an impossible position. Our design focuses on increasing the accessibility and affordability of a prosthetic hand, without significantly sacrificing its quality or usefulness. Apart from wires, screws, and such miscellany, all components are 3D printed. This significantly decreases the cost, as well as ensures that replacement parts are readily available, with access to the STLs and a FDM printer. The design utilizes an OLED display interface, showing the currently selected hand grip and allowing the user to cycle through settings and menus using four tactile buttons. Settings include adjusting contrast and calibrating the EMG threshold for the current user. The calibration stores the EMG values of the relaxed and flexed state of the muscle group, and calculates the ideal threshold, the value at which the system closes the grip of the hand. Prosthetic hands on the market are either prohibitively expensive, or unwieldy and limited in their usefulness. Targeting the former issue by relying on 3D printed parts, greatly alleviates the financial burden of the hand. Likewise, defining finger/grip positions and using EMG signals to switch between open and closed positions allows finer control than a mechanical prosthetic without burdening the user with a significant learning curve for using their prosthetic

The NuMAX Long Baseline Neutrino Factory Concept

A Neutrino Factory where neutrinos of all species are produced in equal quantities by muon decay is described as a facility at the intensity frontier for exquisite precision providing ideal conditions for ultimate neutrino studies and the ideal complement to Long Baseline Facilities like LBNF at Fermilab. It is foreseen to be built in stages with progressively increasing complexity and performance, taking advantage of existing or proposed facilities at an existing laboratory like Fermilab. A tentative layout based on a recirculating linac providing opportunities for considerable saving is discussed as well as its possible evolution toward a muon collider if and when requested by Physics. Tentative parameters of the various stages are presented as well as the necessary R&D to address the technological issues and demonstrate their feasibility.Comment: JINST Special Issue on Muon Accelerators. arXiv admin note: text overlap with arXiv:1308.0494, arXiv:1502.0164

Pair-factorized steady states on arbitrary graphs

Stochastic mass transport models are usually described by specifying hopping rates of particles between sites of a given lattice, and the goal is to predict the existence and properties of the steady state. Here we ask the reverse question: given a stationary state that factorizes over links (pairs of sites) of an arbitrary connected graph, what are possible hopping rates that converge to this state? We define a class of hopping functions which lead to the same steady state and guarantee current conservation but may differ by the induced current strength. For the special case of anisotropic hopping in two dimensions we discuss some aspects of the phase structure. We also show how this case can be traced back to an effective zero-range process in one dimension which is solvable for a large class of hopping functions.Comment: IOP style, 9 pages, 1 figur

Influence of carbon on spin reorientation processes in Er_{2-x}R_{x}Fe_{14}C (R = Gd, Pr) - Mössbauer and magnetometric studies

The $Er_{2-x}R_{x}Fe_{14}C$ (R=Gd, Pr) polycrystalline compounds have been synthesized and investigated with $\text{}^{57}Fe$ Mössbauer spectroscopy and magnetic measurements. The spin reorientation phenomena were studied extensively by narrow step temperature scanning in the neighborhood of the spin reorientation temperature. Obtained Mössbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mössbauer spectra were obtained, temperature and composition dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. Initial magnetization versus temperature measurements (in zero and non-zero external field) for $Er_{2-x}Gd_{x}Fe_{14}C$ compounds allowed to establish the temperature regions of reorientation, change of magnetization value during the transition process. The results obtained with different methods were analyzed and the spin arrangement diagrams were constructed. Data obtained for $Er_{2-x}Gd_{x}Fe_{14}C$ were compared with those for $Er_{2-x}Gd_{x}Fe_{14}B$ series