CLS 2+1 flavor simulations at physical light- and strange-quark masses

We report recent efforts by CLS to generate an ensemble with physical light- and strange-quark masses in a lattice volume of 192x96^3 at $\beta=3.55$ corresponding to a lattice spacing of 0.064 fm. This ensemble is being generated as part of the CLS 2+1 flavor effort with improved Wilson fermions. Our simulations currently cover 5 lattice spacings ranging from 0.039 fm to 0.086 fm at various pion masses along chiral trajectories with either the sum of the quark masses kept fixed, or with the strange-quark mass at the physical value. The current status of simulations is briefly reviewed, including a short discussion of measured autocorrelation times and of the main features of the simulations. We then proceed to discuss the thermalization strategy employed for the generation of the physical quark-mass ensemble and present first results for some simple observables. Challenges encountered in the simulation are highlighted.Comment: 7 pages, 8 figures; Proceedings, 35th International Symposium on Lattice Field Theory (Lattice2017): Granada, Spai

Quantifying Regional and Global Liver Function Via Gadoxetic Acid Uptake

Liver function is a dominant factor in the survival of patients with hepatocellular carcinoma (HCC). Measures of regional and global liver function are critical in guiding treatments for intrahepatic cancers. Regional and global liver function assessments important for defining the magnitude and spatial distribution of radiation dose to preserve functional liver parenchyma and reduce incidence of hepatotoxicity from radiation therapy (RT) for intrahepatic cancer treatment. This individualized liver function-guided RT strategy is critical for patients with heterogeneous and poor liver function, often observed in cirrhotic patients treated for HCC. Dynamic gadoxetic-acid enhanced (DGAE) magnetic resonance imaging (MRI) allows investigation of liver function through observation of the uptake of contrast agent into the hepatocytes. This work seeks to determine if gadoxetic uptake rate can be used as a reliable measure of liver function, and to develop robust methods for uptake estimation with an interest in the therapeutic application of this knowledge in the case of intrahepatic cancers. Since voxel-by voxel fitting of the preexisting nonlinear dual-input two-compartment model is highly susceptible to over fitting, and highly dependent on data that is both temporally very well characterized and low in noise, this work proposes and validates a new model for quantifying the voxel-wise uptake rate of gadoxetic acid as a measure of regional liver function. A linearized single-input two-compartment (LSITC) model is a linearization of the pre-existing dual-input model but is designed to perform uptake quantification in a more robust, computationally simpler, and much faster manner. The method is validated against the preexisting dual-input model for both real and simulated data. Simulations are used to investigate the effects of noise as well as issues related to the sampling of the arterial peak in the characteristic input functions of DGAE MRI. Further validation explores the relationship between gadoxetic acid uptake rate and two well established global measures of liver function, namely: Indocyanine Green retention (ICGR) and Albumin-Bilirubin (ALBI) score. This work also establishes the relationships between these scores and imaging derived measures of whole liver function using uptake rate. Additionally, the same comparisons are performed for portal venous perfusion, a pharmacokinetic parameter that has been observed to correlate with function in patients with relatively good liver function, and has been used as a guide for individualized liver function-guided RT. For the patients assessed, gadoxetic acid uptake rate performs significantly better as a predictor of whole liver function than portal venous perfusion. This work also investigates the possible gains that could be introduced through use of gadoxetic uptake rate maps in the creation of function-guided RT plans. To this end, plans were created using both perfusion and uptake, and both were compared to plans that did not use functional guidance. While the plans were generally broadly similar, significant differences were observed in patients with severely compromised uptake that did not correspond with compromised perfusion. This dissertation also deals with the problem of quantifying uptake rate in suboptimal very temporally sparse or short DGAE MRI acquisitions. In addition to testing the limits of the LSITC model for these limited datasets (both realistic and extreme), a neural network-based approach to quantification of uptake rate is developed, allowing for increased robustness over current models.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163264/1/jjsimeth_1.pd

η\eta and η′\eta^\prime masses and decay constants

We present preliminary results for the masses and decay constants of the $\eta$ and $\eta^\prime$ mesons using CLS $N_f = 2+1$ ensembles. One of the major challenges in these calculations are the large statistical fluctuations due to disconnected quark loops. We tackle these by employing a combination of noise reduction techniques which are tuned to minimize the statistical error at a fixed cost. On the analysis side we carefully assess excited states contributions by using a direct fit approach.Comment: 8 pages, 7 figures, talk presented at the 35th International Symposium on Lattice Field Theory, 18-24 June 2017, Granada, Spain. v2: corrected axis labe

Non-local order in Mott insulators, Duality and Wilson Loops

It is shown that the Mott insulating and superfluid phases of bosons in an optical lattice may be distinguished by a non-local 'parity order parameter' which is directly accessible via single site resolution imaging. In one dimension, the lattice Bose model is dual to a classical interface roughening problem. We use known exact results from the latter to prove that the parity order parameter exhibits long range order in the Mott insulating phase, consistent with recent experiments by Endres et al. [Science 334, 200 (2011)]. In two spatial dimensions, the parity order parameter can be expressed in terms of an equal time Wilson loop of a non-trivial U(1) gauge theory in 2+1 dimensions which exhibits a transition between a Coulomb and a confining phase. The negative logarithm of the parity order parameter obeys a perimeter law in the Mott insulator and is enhanced by a logarithmic factor in the superfluid.Comment: published versio

Using NSPT for the Removal of Hypercubic Lattice Artifacts

The treatment of hypercubic lattice artifacts is essential for the calculation of non-perturbative renormalization constants of RI-MOM schemes. It has been shown that for the RI'-MOM scheme a large part of these artifacts can be calculated and subtracted with the help of diagrammatic Lattice Perturbation Theory (LPT). Such calculations are typically restricted to 1-loop order, but one may overcome this limitation and calculate hypercubic corrections for any operator and action beyond the 1-loop order using Numerical Stochastic Perturbation Theory (NSPT). In this study, we explore the practicability of such an approach and consider, as a first test, the case of Wilson fermion bilinear operators in a quenched theory. Our results allow us to compare boosted and unboosted perturbative corrections up to the 3-loop order.Comment: 7 pages, 6 figures, talk presented at the 32nd International Symposium on Lattice Field Theory (Lattice 2014), 23-28 June 2014, New York, USA; PoS(LATTICE2014)29

Discretization Errors for the Gluon and Ghost Propagators in Landau Gauge using NSPT

The subtraction of hypercubic lattice corrections, calculated at 1-loop order in lattice perturbation theory (LPT), is common practice, e.g., for determinations of renormalization constants in lattice hadron physics. Providing such corrections beyond 1-loop order is however very demanding in LPT, and numerical stochastic perturbation theory (NSPT) might be the better candidate for this. Here we report on a first feasibility check of this method and provide (in a parametrization valid for arbitrary lattice couplings) the lattice corrections up to 3-loop order for the SU(3) gluon and ghost propagators in Landau gauge. These propagators are ideal candidates for such a check, as they are available from lattice simulations to high precision and can be combined to a renormalization group invariant product (Minimal MOM coupling) for which a 1-loop LPT correction was found to be insufficient to remove the bulk of the hypercubic lattice artifacts from the data. As a bonus, we also compare our results with the ever popular H(4) method.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

GAN and dual‐input two‐compartment model‐based training of a neural network for robust quantification of contrast uptake rate in gadoxetic acid‐enhanced MRI

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154967/1/mp14055_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154967/2/mp14055.pd

Patents and Knowledge Diffusion:The Effect of Early Disclosure

We study how the timing of information disclosure affects the diffusion of codified technical information. On November 29, 2000, the American Inventors Protection Act (AIPA) reduced the default publication time of patents at the United States Patent and Trademark Office (USPTO) to 18 months. We analyze the effects of this change by means of a regression discontinuity design with time as an assignment variable and a complementary difference-in-differences analysis. Our study shows that information flows from patents measured by forward citations, increased. Interestingly, the degree of localization within geographic boundaries remained unchanged and technological localization even increased moderately. Moreover, the effect of early disclosure on citations from patents filed by patent attorney service firms is particularly strong. These results imply that knowledge diffusion stemming from speedier disclosure of technical information is confined to the existing attention scope and absorptive capacity of inventors and organizations

Lattice simulations with Nf=2+1N_f=2+1 improved Wilson fermions at a fixed strange quark mass

The explicit breaking of chiral symmetry of the Wilson fermion action results in additive quark mass renormalization. Moreover, flavour singlet and non-singlet scalar currents acquire different renormalization constants with respect to continuum regularization schemes. This complicates keeping the renormalized strange quark mass fixed when varying the light quark mass in simulations with $N_f=2+1$ sea quark flavours. Here we present and validate our strategy within the CLS (Coordinated Lattice Simulations) effort to achieve this in simulations with non-perturbatively order-$a$ improved Wilson fermions. We also determine various combinations of renormalization constants and improvement coefficients.Comment: 18 pages, 11 Figures, V2: References added/updated, all fits rerun with improved statistics for ensemble N204, also using the final values for the improvement coefficients A and b_P-b_A (very minor impact), The figures have been replotted accordingly. (The differences with respect to V1 are invisible to the human eye). Minor change

Asymmetric Information and R&D Disclosure: Evidence from Scientific Publications

We examine how asymmetric information in financial markets affects voluntary research and development (R&D) disclosure, considering scientific publications as a disclosure channel. Difference-in-differences regressions around brokerage house mergers and closures, which increase information asymmetry through reductions in analyst coverage, indicate a quick and sustained increase in scientific publications from treated firms relative to the number of publications from control firms. The treatment effects are concentrated among firms with higher information asymmetry and lower investor demand, firms with greater financial constraints, and firms with lower proprietary costs. We do not find evidence of changes in financial disclosure, nor do we find changes in patenting. Results from ordinary least squares regressions show that scientific publications by firms are positively associated with investor attention toward those firms. We complement these results with qualitative evidence from conference calls. Our results highlight the limitations and trade-offs R&D firms face in their financial market disclosure policies