RG Flow from ϕ4\phi^4 Theory to the 2D Ising Model

We study 1+1 dimensional $\phi^4$ theory using the recently proposed method of conformal truncation. Starting in the UV CFT of free field theory, we construct a complete basis of states with definite conformal Casimir, $\mathcal{C}$. We use these states to express the Hamiltonian of the full interacting theory in lightcone quantization. After truncating to states with $\mathcal{C} \leq \mathcal{C}_{\max}$, we numerically diagonalize the Hamiltonian at strong coupling and study the resulting IR dynamics. We compute non-perturbative spectral densities of several local operators, which are equivalent to real-time, infinite-volume correlation functions. These spectral densities, which include the Zamolodchikov $C$-function along the full RG flow, are calculable at any value of the coupling. Near criticality, our numerical results reproduce correlation functions in the 2D Ising model.Comment: 31+12 page

Effect of Surgical Fusion on Volitional Weight-Shifting in Individuals With Adolescent Idiopathic Scoliosis

Study Design Prospective. Objectives The goals of this study were to (1) evaluate the differences in weightbearing symmetry between individuals with adolescent idiopathic scoliosis (AIS) and typically developing controls; (2) observe the effect of posterior spinal fusion and instrumentation (PSFI) on volitional weight-shifting at 1 and 2 years postoperatively; and (3) evaluate whether lowest instrumented fusion level (ie, lowest instrumented vertebra [LIV]) in PSFI has an effect on volitional weight-shifting. Summary of Background Data Previous studies have conflicting findings with regard to the effect of scoliosis on postural control tasks as well as the effect of surgery. They have also noted an inconsistent effect of PSFI at different LIVs, with more distal LIVs exhibiting greater reductions in postoperative range of motion. Methods The study was designed with an AIS group of 41 patients (8 males and 33 females) with AIS who underwent PSFI, along with a Control Group of 24 age-matched typically developing participants (12 male and 12 female). Both groups performed postural control tasks (static balance and volitional weight-shifting), with the AIS group repeating the tasks at 1 and 2 years postoperatively. Results At baseline, the AIS group showed increased weightbearing asymmetry than the Control Group (p = .01). The AIS group showed improvements in volitional weight-shifting at 2 years over baseline (p \u3c .01). There was no effect of LIV on volitional weight-shifting by the second postoperative year. Conclusions Individuals with AIS have greater weightbearing asymmetry but improved volitional weight-shifting over typically developing controls. PSFI improves volitional weight-shifting beyond preoperative baseline but does not differ significantly by LIV

Effect of Surgical Fusion on Volitional Weight-Shifting in Individuals With Adolescent Idiopathic Scoliosis

Study Design Prospective. Objectives The goals of this study were to (1) evaluate the differences in weightbearing symmetry between individuals with adolescent idiopathic scoliosis (AIS) and typically developing controls; (2) observe the effect of posterior spinal fusion and instrumentation (PSFI) on volitional weight-shifting at 1 and 2 years postoperatively; and (3) evaluate whether lowest instrumented fusion level (ie, lowest instrumented vertebra [LIV]) in PSFI has an effect on volitional weight-shifting. Summary of Background Data Previous studies have conflicting findings with regard to the effect of scoliosis on postural control tasks as well as the effect of surgery. They have also noted an inconsistent effect of PSFI at different LIVs, with more distal LIVs exhibiting greater reductions in postoperative range of motion. Methods The study was designed with an AIS group of 41 patients (8 males and 33 females) with AIS who underwent PSFI, along with a Control Group of 24 age-matched typically developing participants (12 male and 12 female). Both groups performed postural control tasks (static balance and volitional weight-shifting), with the AIS group repeating the tasks at 1 and 2 years postoperatively. Results At baseline, the AIS group showed increased weightbearing asymmetry than the Control Group (p = .01). The AIS group showed improvements in volitional weight-shifting at 2 years over baseline (p \u3c .01). There was no effect of LIV on volitional weight-shifting by the second postoperative year. Conclusions Individuals with AIS have greater weightbearing asymmetry but improved volitional weight-shifting over typically developing controls. PSFI improves volitional weight-shifting beyond preoperative baseline but does not differ significantly by LIV

A two-phase gripper to reorient and grasp

This paper introduces the design of novel two-phase fingers to passively reorient objects while picking them up. Two-phase refers to a change in the finger-object contact geometry, from a free spinning point contact to a firm multipoint contact, as the gripping force increases. We exploit the two phases to passively reorient prismatic objects from a horizontal resting pose to an upright secure grasp. This problem is particularly relevant to industrial assembly applications where parts often are presented lying on trays or conveyor belts and need to be assembled vertically. Each two-phase finger is composed of a small hard contact point attached to an elastic strip mounted over a V-groove cavity. When grasped between two parallel fingers with low gripping force, the object pivots about the axis between the contact points on the strips, and aligns upright with gravity. A subsequent increase in the gripping force makes the elastic strips recede into the cavities letting the part seat in the V-grooves to secure the grasp. The design is compatible with any type of parallel-jaw gripper, and can be reconfigured to specific objects by changing the geometry of the cavity. The two-phase gripper provides robots with the capability to accurately position and manipulate parts, reducing the need for dedicated part feeders or time-demanding regrasp procedures.National Science Foundation (U.S.). National Robotics Initiative (NSF-IIS-1427050

Generating reversible circuits from higher-order functional programs

Boolean reversible circuits are boolean circuits made of reversible elementary gates. Despite their constrained form, they can simulate any boolean function. The synthesis and validation of a reversible circuit simulating a given function is a difficult problem. In 1973, Bennett proposed to generate reversible circuits from traces of execution of Turing machines. In this paper, we propose a novel presentation of this approach, adapted to higher-order programs. Starting with a PCF-like language, we use a monadic representation of the trace of execution to turn a regular boolean program into a circuit-generating code. We show that a circuit traced out of a program computes the same boolean function as the original program. This technique has been successfully applied to generate large oracles with the quantum programming language Quipper.Comment: 21 pages. A shorter preprint has been accepted for publication in the Proceedings of Reversible Computation 2016. The final publication is available at http://link.springer.co

Reconstructing baryon oscillations

The baryon acoustic oscillation (BAO) method for constraining the expansion history is adversely affected by non-linear structure formation, which washes out the correlation function peak created at decoupling. To increase the constraining power of low z BAO experiments, it has been proposed that one use the observed distribution of galaxies to "reconstruct'' the acoustic peak. Recently Padmanabhan, White and Cohn provided an analytic formalism for understanding how reconstruction works within the context of Lagrangian perturbation theory. We extend that formalism to include the case of biased tracers of the mass and, because the quantitative validity of LPT is questionable, we investigate reconstruction in N-body simulations. We find that LPT does a good job of explaining the trends seen in simulations for both the mass and for biased tracers and comment upon the implications this has for reconstruction.Comment: 9 pages, 8 figure

Promoting global clinical care and research for children with orthopaedic disabilities through motion analysis technology

Human motion analysis is a tool used to understand orthopaedic disabilities in children and to plan and monitor treatment strategies. It enables clinicians to quantitatively describe rehabilitative progress, plan surgeries, and conduct research. While this technology is prevalent in major academic medical centers, access is lacking in many regions throughout the world. This paper presents a novel approach to offer more accessible technology at greatly reduced cost. Current applications are underway in the Philippines, Mexico, and Colombia. Through international partnerships, improvements in clinical care, medical education, and research have been observed