bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary QCD phase transition line for 695 MeV dynamical staggered fermions from effective Polyakov line actions
Authors: Höllwieser Roman , Greensite Jeff
Published: March 2018

We present a phase diagram for SU(3) lattice gauge theory with 695 MeV dynamical staggered fermions, in the plane of temperature and chemical potential, obtained from effective Polyakov line actions. The derivation is via the method of relative weights, and the effective theories are solved at finite chemical potential by mean field theory.
Spin models in complex magnetic fields: a hard sign problem
Authors: de Forcrand Philippe , Rindlisbacher Tobias
Published: March 2018

Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these points. In this study, we couple the N-state Potts model in different ways to a complex external magnetic field and discuss the above mentioned phenomena and their relations based on analytic calculations (1D) and results obtained using a modified cluster algorithm (general D) that in many cases either cures or at least drastically reduces the sign-problem induced by the complex external field.
Complex Langevin Simulations of QCD at Finite Density – Progress Report
Authors: Sinclair D. K. , Kogut J. B.
Published: March 2018

We simulate lattice QCD at finite quark-number chemical potential to study nuclear matter, using the complex Langevin equation (CLE). The CLE is used because the fermion determinant is complex so that standard methods relying on importance sampling fail. Adaptive methods and gauge-cooling are used to prevent runaway solutions. Even then, the CLE is not guaranteed to give correct results. We are therefore performing extensive testing to determine under what, if any, conditions we can achieve reliable results. Our earlier simulations at β = 6/g2 = 5.6, m = 0.025 on a 124 lattice reproduced the expected phase structure but failed in the details. Our current simulations at β = 5.7 on a 164 lattice fail in similar ways while showing some improvement. We are therefore moving to even weaker couplings to see if the CLE might produce the correct results in the continuum (weak-coupling) limit, or, if it still fails, whether it might reproduce the results of the phase-quenched theory. We also discuss action (and other dynamics) modifications which might improve the performance of the CLE.
Equation of State and Freezeout in QCD with Staggered Quarks
Authors: Datta Saumen , Gavai R. V. , Gupta Sourendu
Published: March 2018

We report the equation of state at finite chemical potential, namely the baryon number density and the baryonic contribution to the pressure, using a resummation of the Taylor expansion. We also report the freezeout conditions for a measure of fluctuations. We examine the major sources of systematic and statistical errors in all of these measurements.
Finite temperature gluon propagator in Landau gauge: non-zero Matsubara frequencies and spectral densities
Authors: Silva Paulo J. , Oliveira Orlando , Dudal David , Roelfs Martin
Published: March 2018

We report on the lattice computation of the Landau gauge gluon propagator at finite temperature, including the non-zero Matsubara frequencies. Moreover, the corresponding Källén-Lehmann spectral density is computed, using a Tikhonov regularisation together with the Morozov discrepancy principle. Implications for gluon confinement are also discussed.
Improved convergence of Complex Langevin simulations
Authors: Attanasio Felipe , Jäger Benjamin
Published: March 2018

The sign problem appears in lattice QCD as soon as a non-zero chemical potential is introduced. This prevents direct simulations to determine the phase structure of the strongly interacting matter. Complex Langevin methods have been successfully used for various models or approximations of QCD. However, in some scenarios it converges to incorrect results. We present developments of our new method that helps to improve the convergence by keeping the system closer to the SU(3) manifold and discuss preliminary tests and results.
Spectrum of QCD at Finite Isospin Density
Authors: Scior Philipp , Smekal Lorenz von , Smith Dominik
Published: March 2018

We study the phase diagram of QCD at finite isospin density using two flavors of staggered quarks. We investigate the low temperature region of the phase diagram where we find a pion condensation phase at high chemical potential. We started a basic analysis of the spectrum at finite isospin density. In particular, we measured pion, rho and nucleon masses inside and outside of the pion condensation phase. In agreement with previous studies in two-color QCD at finite baryon density we find that the Polyakov loop does not depend on the density in the staggered formulation.
Path optimization method for the sign problem
Authors: Ohnishi Akira , Mori Yuto , Kashiwa Kouji
Published: March 2018

We propose a path optimization method (POM) to evade the sign problem in the Monte-Carlo calculations for complex actions. Among many approaches to the sign problem, the Lefschetz-thimble path-integral method and the complex Langevin method are promising and extensively discussed. In these methods, real field variables are complexified and the integration manifold is determined by the flow equations or stochastically sampled. When we have singular points of the action or multiple critical points near the original integral surface, however, we have a risk to encounter the residual and global sign problems or the singular drift term problem. One of the ways to avoid the singular points is to optimize the integration path which is designed not to hit the singular points of the Boltzmann weight. By specifying the one-dimensional integration-path as z = t +if(t)(f ϵ R) and by optimizing f(t) to enhance the average phase factor, we demonstrate that we can avoid the sign problem in a one-variable toy model for which the complex Langevin method is found to fail. In this proceedings, we propose POM and discuss how we can avoid the sign problem in a toy model. We also discuss the possibility to utilize the neural network to optimize the path.
An estimate for the thermal photon rate from lattice QCD
Authors: Brandt Bastian B. , Francis Anthony , Harris Tim , Meyer Harvey B. , Steinberg Aman
Published: March 2018

We estimate the production rate of photons by the quark-gluon plasma in lattice QCD. We propose a new correlation function which provides better control over the systematic uncertainty in estimating the photon production rate at photon momenta in the range πT/2 to 2πT. The relevant Euclidean vector current correlation functions are computed with Nf = 2 Wilson clover fermions in the chirally-symmetric phase. In order to estimate the photon rate, an ill-posed problem for the vector-channel spectral function must be regularized. We use both a direct model for the spectral function and a modelindependent estimate from the Backus-Gilbert method to give an estimate for the photon rate.
Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime
Authors: Gagliardi Giuseppe , Kim Jangho , Unger Wolfgang
Published: March 2018

We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this limiting case β → 0 are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the μB – T plane has been established in the strong coupling limit. We present numerical simulations away from the strong coupling limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of β.
Improved results for the mass spectrum of N = 1 supersymmetric SU(3) Yang-Mills theory
Authors: Ali Sajid , Bergner Georg , Gerber Henning , Giudice Pietro , Kuberski Simon , Münster Gernot , Montvay István , Piemonte Stefano , Scior Philipp
Published: March 2018

This talk summarizes the results of the DESY-Münster collaboration for N = 1 supersymmetric Yang-Mills theory with the gauge group SU(3). It is an updated status report with respect to our preliminary data presented at the last conference. In order to control the lattice artefacts we have now considered a clover improved fermion action and different values of the gauge coupling.
Testing a non-perturbative mechanism for elementary fermion
mass generation: numerical results
Authors: Capitani Stefano , De Divitiis Giulia Maria , Dimopoulos Petros , Frezzotti Roberto , Garofalo Marco , Knippschild Bastian , Kostrzewa Bartosz , Pittler Ferenc , Rossi Giancarlo , Urbach Carsten
Published: March 2018

Based on a recent proposal according to which elementary particle masses could be generated by a non-perturbative dynamical phenomenon, alternative to the Higgs mechanism, we carry out lattice simulations of a model where a non-abelian strongly interacting fermion doublet is also coupled to a doublet of complex scalar fields via a Yukawa and an “irrelevant" Wilson-like term. In this pioneering study we use naive fermions and work in the quenched approximation. We present preliminary numerical results both in the Wigner and in the Nambu-Goldstone phase, focusing on the observables relevant to check the occurrence of the conjectured dynamical fermion mass generation effect in the continuum limit of the critical theory in its spontaneously broken phase.
SU(2) with fundamental fermions and scalars
Authors: Hansen Martin , Janowski Tadeusz , Pica Claudio , Toniato Arianna
Published: March 2018

We present preliminary results on the lattice simulation of an SU(2) gauge theory with two fermion flavors and one strongly interacting scalar field, all in the fundamental representation of SU(2). The motivation for this study comes from the recent proposal of “fundamental” partial compositeness models featuring strongly interacting scalar fields in addition to fermions. Here we describe the lattice setup for our study of this class of models and a first exploration of the lattice phase diagram. In particular we then investigate how the presence of a strongly coupled scalar field affects the properties of light meson resonances previously obtained for the SU(2) model.

Preprint: CP3-Origins-2017-047 DNRF90
Supermultiplets in N=1 SUSY SU(2) Yang-Mills Theory
Authors: Ali Sajid , Bergner Georg , Gerber Henning , Giudice Pietro , Kuberski Simon , Montvay István , Münster Gernot , Piemonte Stefano , Scior Philipp
Published: March 2018

We study N = 1 supersymmetric Yang-Mills theory (SYM) on the lattice. The non-perturbative nature of supersymmetric field theories is still largely unknown. Similarly to QCD, SYM is confining and contains strongly bound states. Applying the variational method together with different smearing techniques we extract masses of the lightest bound states such as gluino-glue, glueball and mesonic states. As these states should form supermultiplets, this study allows to check whether SYM remains supersymmetric also on the quantum level.
Higgs-Yukawa model on the lattice
Authors: Chu David Y.-J. , Jansen Karl , Knippschild Bastian , Lin C.-J. David
Published: March 2018

We present results from two projects on lattice calculations for the Higgs-Yukawa model. First we report progress on the search of first-order thermal phase transitions in the presence of a dimension-six operator, with the choices of bare couplings that lead to viable phenomenological predictions. In this project the simulations are performed using overlap fermions. Secondly, our study for applying finite-size scaling techniques near the Gaussian fixed point of the Higgs-Yukawa model is presented. We discuss the analytical formulae for the Higgs Yukawa model and show results for a first numerical study in the pure O(4) scalar sector of the theory.
N = 2* Yang-Mills on the Lattice
Authors: Joseph Anosh
Published: March 2018

The N = 2* Yang-Mills theory in four dimensions is a non-conformal theory that appears as a mass deformation of maximally supersymmetric N = 4 Yang-Mills theory. This theory also takes part in the AdS/CFT correspondence and its gravity dual is type IIB supergravity on the Pilch-Warner background. The finite temperature properties of this theory have been studied recently in the literature. It has been argued that at large N and strong coupling this theory exhibits no thermal phase transition at any nonzero temperature. The low temperature N = 2* plasma can be compared to the QCD plasma. We provide a lattice construction of N = 2* Yang-Mills on a hypercubic lattice starting from the N = 4 gauge theory. The lattice construction is local, gauge-invariant, free from fermion doubling problem and preserves a part of the supersymmetry. This nonperturbative formulation of the theory can be used to provide a highly nontrivial check of the AdS/CFT correspondence in a non-conformal theory.
Two-dimensional N = 2 Super-Yang-Mills Theory
Authors: August Daniel , Wellegehausen Björn , Wipf Andreas
Published: March 2018

Supersymmetry is one of the possible scenarios for physics beyond the standard model. The building blocks of this scenario are supersymmetric gauge theories. In our work we study the N = 1 Super-Yang-Mills (SYM) theory with gauge group SU(2) dimensionally reduced to two-dimensional N = 2 SYM theory. In our lattice formulation we break supersymmetry and chiral symmetry explicitly while preserving R symmetry. By fine tuning the bar-mass of the fermions in the Lagrangian we construct a supersymmetric continuum theory. To this aim we carefully investigate mass spectra and Ward identities, which both show a clear signal of supersymmetry restoration in the continuum limit.
Flavor-singlet spectrum in multi-flavor QCD
Authors: Aoki Yasumichi , Aoyama Tatsumi , Bennett Ed , Kurachi Masafumi , Maskawa Toshihide , Miura Kohtaroh , Nagai Kei-ichi , Ohki Hiroshi , Rinaldi Enrico , Shibata Akihiro , Yamawaki Koichi , Yamazaki Takeshi
Published: March 2018

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.
Confinement study of an SU(4) gauge theory with fermions in multiple representations
Authors: Ayyar Venkitesh , Hackett Daniel C. , Jay William I. , Neil Ethan T.
Published: March 2018

We discuss the phase diagnostics used in our finite-temperature study of an SU(4) gauge theory with dynamical fermions in both the fundamental and two-index antisymmetric representations. Beyond the usual Polyakov loop diagnostics of confinement, we employ several Wilson flow phase diagnostics. The first, what we call the ‘‘flow anisotropy’’, is known in the literature: the deconfinement transition introduces anisotropy between the spatial and temporal directions, to which the flow is extremely sensitive. The second, the ‘‘long flow time Polyakov loop,’’ is related but novel. While we do not claim to fully understand this diagnostic, we have empirically found it to be useful as an unusually sharp diagnostic of phase.
BaHaMAS A Bash Handler to Monitor and Administrate Simulations
Authors: Sciarra Alessandro
Published: March 2018

Numerical QCD is often extremely resource demanding and it is not rare to run hundreds of simulations at the same time. Each of these can last for days or even months and it typically requires a job-script file as well as an input file with the physical parameters for the application to be run. Moreover, some monitoring operations (i.e. copying, moving, deleting or modifying files, resume crashed jobs, etc.) are often required to guarantee that the final statistics is correctly accumulated. Proceeding manually in handling simulations is probably the most error-prone way and it is deadly uncomfortable and inefficient! BaHaMAS was developed and successfully used in the last years as a tool to automatically monitor and administrate simulations.
Automated lattice data generation
Authors: Ayyar Venkitesh , Hackett Daniel C. , Jay William I. , Neil Ethan T.
Published: March 2018

The process of generating ensembles of gauge configurations (and measuring various observables over them) can be tedious and error-prone when done “by hand”. In practice, most of this procedure can be automated with the use of a workflow manager. We discuss how this automation can be accomplished using Taxi, a minimal Python-based workflow manager built for generating lattice data. We present a case study demonstrating this technology.
Charm quark effects on the strong coupling extracted from the static force
Authors: Calì Salvatore , Knechtli Francesco , Korzec Tomasz , Panagopoulos Haralambos
Published: March 2018

We compute the fermionic contribution to the strong coupling αqq extracted from the static force in Lattice QCD up to order g4 in perturbation theory. This allows us to subtract the leading fermionic lattice artifacts from recent determinations of αqq produced in simulations of two dynamical charm quarks.

Moreover, by using a suitable parametrization of the βqq-function, we can evaluate the charm loop effects on αqq in the continuum limit.
Estimates of Scaling Violations for Pure SU(2) LGT
Authors: Berg Bernd , Clarke David
Published: March 2018

We investigate the approach of pure SU(2) lattice gauge theory with theWilson action to its continuum limit using the deconfining transition, Lüscher’s gradient flow [1], and the cooling flow [2, 3] to set the scale. Of those, the cooling flow turns out to be computationally most efficient. We explore systematic errors due to use of three different energy observables and two distinct reference values for the flow time, the latter obtained by matching initial scaling behavior of some energy observables to that of the deconfining transition. Another important source of systematic errors are distinct fitting forms for the approach to the continuum limit. Besides relying in the conventional way on ratios of masses, we elaborate on a form introduced by Allton [4], which incorporates asymptotic scaling behavior. Ultimately we find that, though still small, our systematic errors are considerably larger than our statistical errors.
Non-perturbative determination of improvement b-coefficients in Nf = 3
Authors: de Divitiis Giulia Maria , Firrotta Maurizio , Heitger Jochen , Köster Carl Christian , Vladikas Anastassios
Published: March 2018

We present our preliminary results of the non-perturbative determination of the valence mass dependent coefficients bA - bP and bm as well as the ratio ZPZm=ZA entering the flavour non-singlet PCAC relation in lattice QCD with Nf = 3 dynamical flavours. We apply the method proposed in the past for quenched approximation and Nf = 2 cases, employing a set of finite-volume ALPHA configurations with Schrödinger functional boundary conditions, generated with O(a) improved Wilson fermions and the tree-level Symanzik-improved gauge action for a range of couplings relevant for simulations at lattice spacings of about 0.09 fm and below.
Beyond Complex Langevin Equations: positive representation of a class of complex measures
Authors: Seiler Erhard , Wosiek Jacek
Published: March 2018

A positive representation for a set of complex densities is constructed. In particular, complex measures on a direct product ofU(1) groups are studied. After identifying general conditions which such representations should satisfy, several concrete realizations are proposed. Their utility is illustrated in few concrete examples representing problems in abelian lattice gauge theories.
Extracting observables from lattice data in the three-particle sector
Authors: Rusetsky Akaki , Hammer Hans-Werner , Pang Jin-Yi
Published: March 2018

The three-particle quantization condition is derived, using the particle-dimer picture in the non-relativistic effective field theory. The procedure for the extraction of various observables in the three-particle sector (the particle-dimer scattering amplitudes, breakup amplitudes, etc.) from the finite-volume lattice spectrum is discussed in detail. As an illustration of the general formalism, the expression for the finite-volume energy shift of the three-body bound-state in the unitary limit is re-derived. The role of the threebody force, which is essential for the renormalization, is highlighted, and the extension of the result beyond the unitary limit is studied. Comparison with other approaches, known in the literature, is carried out.
Loop equation in Lattice gauge theories and bootstrap methods
Authors: Anderson Peter , Kruczenski Martin
Published: March 2018

In principle the loop equation provides a complete formulation of a gauge theory purely in terms ofWilson loops. In the case of lattice gauge theories the loop equation is a well defined equation for a discrete set of quantities and can be easily solved at strong coupling either numerically or by series expansion. At weak coupling, however, we argue that the equations are not well defined unless a certain set of positivity constraints is imposed. Using semi-definite programming we show numerically that, for a pure Yang Mills theory in two, three and four dimensions, these constraints lead to good results for the mean value of the energy at weak coupling. Further, the positivity constraints imply the existence of a positive definite matrix whose entries are expectation values of Wilson loops. This matrix allows us to define a certain entropy associated with theWilson loops. We compute this entropy numerically and describe some of its properties. Finally we discuss some preliminary ideas for extending the results to supersymmetric N = 4 SYM.
Topological Susceptibility under Gradient Flow
Authors: Mejía-Díaz Héctor , Bietenholz Wolfgang , Cichy Krzysztof , Forcrand Philippe de , Dromard Arthur , Gerber Urs , Sandoval Ilya Orson
Published: March 2018

We study the impact of the Gradient Flow on the topology in various models of lattice field theory. The topological susceptibility Xt is measured directly, and by the slab method, which is based on the topological content of sub-volumes (“slabs”) and estimates Xt even when the system remains trapped in a fixed topological sector. The results obtained by both methods are essentially consistent, but the impact of the Gradient Flow on the characteristic quantity of the slab method seems to be different in 2-flavour QCD and in the 2d O(3) model. In the latter model, we further address the question whether or not the Gradient Flow leads to a finite continuum limit of the topological susceptibility (rescaled by the correlation length squared, ξ2). This ongoing study is based on direct measurements of Xt in L × L lattices, at L/ξ ≃6.
Double-winding Wilson loops in SU(N) Yang-Mills theory – A criterion for testing the confinement models –
Authors: Matsudo Ryutaro , Kondo Kei-Ichi , Shibata Akihiro
Published: March 2018

We examine how the average of double-winding Wilson loops depends on the number of color N in the SU(N) Yang-Mills theory. In the case where the two loops C1 and C2 are identical, we derive the exact operator relation which relates the doublewinding Wilson loop operator in the fundamental representation to that in the higher dimensional representations depending on N. By taking the average of the relation, we find that the difference-of-areas law for the area law falloff recently claimed for N = 2 is excluded for N ⩾ 3, provided that the string tension obeys the Casimir scaling for the higher representations. In the case where the two loops are distinct, we argue that the area law follows a novel law (N − 3)A1/(N − 1) + A2 with A1 and A2(A1 < A2) being the minimal areas spanned respectively by the loops C1 and C2, which is neither sum-ofareas (A1 + A2) nor difference-of-areas (A2 − A1) law when (N ⩾ 3). Indeed, this behavior can be confirmed in the two-dimensional SU(N) Yang-Mills theory exactly.
Dirac-mode analysis for quark number density and its application for deconfinement transition
Authors: Doi Takahiro M. , Kashiwa Kouji
Published: March 2018

The quark number density at finite imaginary chemical potential is investigated in the lattice QCD using the Dirac-mode expansion. We find the analytical formula of the quark number density in terms of the Polyakov loop in the large quark mass regime. On the other hand, in the small quark mass region, the quark number density is investigated by using the quenched lattice QCD simulation. The quark number density is found to strongly depend on the low-lying Dirac modes while its sign does not change. This result leads to that the quark number holonomy is not sensitive to the low-lying Dirac modes. We discuss the confinement-deconfinement transition from the property of the quark number density and the quark number holonomy.
Observation of a Coulomb flux tube
Authors: Greensite Jeff , Chung Kristian
Published: March 2018

In Coulomb gauge there is a longitudinal color electric field associated with a static quark-antiquark pair. We have measured the spatial distribution of this field, and find that it falls off exponentially with transverse distance from a line joining the two quarks. In other words there is a Coulomb flux tube, with a width that is somewhat smaller than that of the minimal energy flux tube associated with the asymptotic string tension. A confinement criterion for gauge theories with matter fields is also proposed.
Flux tubes in Nf = 2 + 1 QCD with external magnetic fields
Authors: Bonati Claudio , Calì Salvatore , D’Elia Massimo , Mesiti Michele , Negro Francesco , Rucci Andrea , Sanfilippo Francesco
Published: March 2018

We study the behavior of the confining flux tube in Nf = 2 + 1 QCD at the physical point, discretized with the stout smearing improved staggered quark action and the tree level Symazik gauge action. We discuss how it depends on a uniform external magnetic field, showing how it displays anisotropies with respect to the magnetic field direction. Moreover, we compare the observed anisotropy pattern with that of the static quark-antiquark (QQ̅) potential we obtained in [1, 2].
Instanton dominance over αs at low momenta from lattice QCD simulations at Nf = 0, Nf = 2 + 1 and Nf = 2 + 1 + 1
Authors: Athenodorou Andreas , Boucaud Philippe , de Soto Feliciano , Rodríguez-Quintero José , Zafeiropoulos Savvas
Published: March 2018

We report on an instanton-based analysis of the gluon Green functions in the Landau gauge for low momenta; in particular we use lattice results for αs in the symmetric momentum subtraction scheme (MOM) for large-volume lattice simulations. We have exploited quenched gauge field configurations, Nf = 0, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with Nf = 2 + 1 and Nf = 2 + 1 + 1 dynamical flavors (domain wall and twisted-mass fermions, respectively).

We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination of phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing.

We furthermore apply the Gradient Flow to remove short-distance fluctuations. The Gradient Flow gets rid of the QCD scale, ΛQCD, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of the instanton density and size distribution that is compatible with those extracted from the analysis of the Green functions.
The B(s) → D(s)lv Decay with Highly Improved Staggered Quarks and NRQCD
Authors: McLean Euan , Davies Christine , Colquhoun Brian , Lytle Andrew
Published: March 2018

We report on progress of a lattice QCD calculation of the B → Dlv and Bs → Dslv semileptonic form factors. We use a relativistic staggered action (HISQ) for light and charm quarks, and an improved non-relativistic (NRQCD) action for bottom, on the second generation MILC ensembles.
D meson semileptonic form factors in Nf = 3 QCD with Möbius domain-wall quarks
Authors: Kaneko Takashi , Colquhoun Brian , Fukaya Hidenori , Hashimoto Shoji
Published: March 2018

e present our calculation of D → π and D → K semileptonic form factors in Nf = 2 + 1 lattice QCD. We simulate three lattice cutoffs a-1 ≃ 2.5, 3.6 and 4.5 GeV with pion masses as low as 230 MeV. The Möbius domain-wall action is employed for both light and charm quarks. We present our results for the vector and scalar form factors and discuss their dependence on the lattice spacing, light quark masses and momentum transfer.
Dispersion relation and unphysical poles of Möbius domain-wall fermions in free field theory at finite Ls
Authors: Tomii Masaaki
Published: March 2018

We investigate the dispersion relation of Möbius domain-wall fermions in free field theory at finite Ls. We find that there are Ls - 1 extra poles of Möbius domain-wall fermions in addition to the pole which realizes the physical mode in the continuum limit. The unphysical contribution of these extra poles could be significant when we introduce heavy quarks. We show in this report the fundamental properties of these unphysical poles and discuss the optimal choice of Möbius parameters to minimize their contribution to four-dimensional physics.
BSM Kaon Mixing at the Physical Point
Authors: Boyle Peter , Garron Nicolas , Kettle Julia , Khamseh Ava , Tsang Justus Tobias
Published: March 2018

We present a progress update on the RBC-UKQCD calculation of beyond the standard model (BSM) kaon mixing matrix elements at the physical point. Simulations are performed using 2+1 flavour domain wall lattice QCD with the Iwasaki gauge action at 3 lattice spacings and with pion masses ranging from 430 MeV to the physical pion mass.
Non-leptonic kaon decays at large Nc
Authors: Donini Andrea , Hernández Pilar , Pena Carlos , Romero-López Fernando
Published: March 2018

We study the scaling with the number of colors Nc of the weak amplitudes mediating kaon mixing and decay, in the limit of light charm masses (mu = md = ms = mc). The amplitudes are extracted directly on the lattice for Nc = 3 - 7 (with preliminar results for Nc = 8 and 17) using twisted mass QCD. It is shown that the (sub-leading) 1 /Nc corrections to [see formula in PDF] are small and that the naive Nc → ∞ limit, [see formula in PDF] = 3/4, seems to be recovered. On the other hand, the O (1/Nc) corrections in K → ππ amplitudes (derived from K → π matrix elements) are large and fully anti-correlated in the I = 0 and I = 2 channels. This may have some implications for the understanding of the ΔI = 1/2 rule.
A tmQCD mixed-action approach to flavour physics
Authors: Herdoíza Gregorio , Pena Carlos , Preti David , Romero José Ángel , Ugarrio Javier
Published: March 2018

We discuss a mixed-action approach in which sea quarks are regularised using non-perturbatively O(a) improved Wilson fermions, while a fully-twisted tmQCD action is used for valence quarks. In this setup, automatic O(a) improvement is preserved for valence observables, apart from small residual O(a) effects from the sea. A strategy for matching sea and valence is set up, and carried out for Nf = 2 + 1 CLS ensembles with open boundary conditions at several simulation points. The scaling of basic light-quark observables such as the pseudoscalar meson decay constant is studied, as well as the isospin splitting of pseudoscalar meson masses.
Total decay and transition rates from LQCD
Authors: Hansen Maxwell T. , Meyer Harvey B. , Robaina Daniel
Published: March 2018

We present a new technique for extracting total transition rates into final states with any number of hadrons from lattice QCD. The method involves constructing a finite-volume Euclidean four-point function whose corresponding infinite-volume spectral function gives access to the decay and transition rates into all allowed final states. The inverse problem of calculating the spectral function is solved via the Backus-Gilbert method, which automatically includes a smoothing procedure. This smoothing is in fact required so that an infinite-volume limit of the spectral function exists. Using a numerical toy example we find that reasonable precision can be achieved with realistic lattice data. In addition, we discuss possible extensions of our approach and, as an example application, prospects for applying the formalism to study the onset of deep-inelastic scattering. More details are given in the published version of this work, Ref. [1].
Improving the theoretical prediction for the Bs - B̅s width difference: matrix elements of next-to-leading order ΔB = 2 operators
Authors: Davies Christine , Harrison Judd , Lepage G Peter , Monahan Christopher , Shigemitsu Junko , Wingate Matthew
Published: March 2018

We present lattice QCD results for the matrix elements of R2 and other dimension-7, ΔB = 2 operators relevant for calculations of Δs, the Bs - B̅s width difference. We have computed correlation functions using 5 ensembles of the MILC Collaboration’s 2+1 + 1-flavour gauge field configurations, spanning 3 lattice spacings and light sea quarks masses down to the physical point. The HISQ action is used for the valence strange quarks, and the NRQCD action is used for the bottom quarks. Once our analysis is complete, the theoretical uncertainty in the Standard Model prediction for ΔΓs will be substantially reduced.
D → π and D → K semileptonic form factors with Nf = 2 + 1 + 1 twisted mass fermions
Authors: Lubicz Vittorio , Riggio Lorenzo , Salerno Giorgio , Simula Silvano , Tarantino Cecilia
Published: March 2018

We present a lattice determination of the vector and scalar form factors of the D → π(K)lv semileptonic decays, which are relevant for the extraction of the CKM matrix elements |Vcd| and |Vcs| from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 +1 flavors of dynamical quarks. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV. The matrix elements of both vector and scalar currents are determined for a plenty of kinematical conditions in which parent and child mesons are either moving or at rest. Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum limit the vector and scalar form factors are determined in the whole kinematical region from q2 = 0 up to [see formula in PDF] accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of q2 where some deviations are visible.
An update on the BQCD Hybrid Monte Carlo program
Authors: Haar Taylor Ryan , Nakamura Yoshifumi , Stüben Hinnerk
Published: March 2018

We present an update of BQCD, our Hybrid Monte Carlo program for simulating lattice QCD. BQCD is one of the main production codes of the QCDSF collaboration and is used by CSSM and in some Japanese finite temperature and finite density projects. Since the first publication of the code at Lattice 2010 the program has been extended in various ways. New features of the code include: dynamical QED, action modification in order to compute matrix elements by using Feynman-Hellman theory, more trace measurements (like Tr(D-n) for K, cSW and chemical potential reweighting), a more flexible integration scheme, polynomial filtering, term-splitting for RHMC, and a portable implementation of performance critical parts employing SIMD.
Vector-Vector Scattering on the Lattice
Authors: Romero-López Fernando , Urbach Carsten , Rusetsky Akaki
Published: March 2018

In this work we present an extension of the LüScher formalism to include the interaction of particles with spin, focusing on the scattering of two vector particles. The derived formalism will be applied to Scalar QED in the Higgs Phase, where the U(1) gauge boson acquires mass.
Numerical experiments using deflation with the HISQ action
Authors: Davies Christine , DeTar Carleton , McNeile Craig , Vaquero Alejandro
Published: March 2018

We report on numerical experiments using deflation to compute quark propagators for the highly improved staggered quark (HISQ) action. The method is tested on HISQ gauge configurations, generated by the MILC collaboration, with lattice spacings of 0.15 fm, with a range of volumes, and sea quark masses down to the physical quark mass.
New methods for B decay constants and form factors from Lattice NRQCD
Authors: Davies Christine , Hughes Ciaran , Monahan Christopher
Published: March 2018

We determine the normalisation of scalar and pseudo scalar current operators made from NonRelativistic QCD (NRQCD) b quarks and Highly Improved Staggered (HISQ) light quarks through O(αs∧QCD/mb). We use matrix elements of these operators to extract B meson decay constants and form factors and compare to those obtained using the standard vector and axial vector operators. We work on MILC second-generation 2+1+1 gluon field configurations, including those with physical light quarks in the sea. This provides a test of systematic uncertainties in these calculations and we find agreement between the results to the 2% level of uncertainty previously quoted.
Genetics of Lithium Response in Bipolar Disorder
Authors: Papiol Sergi , Schulze Thomas , Alda Martin
Published: March 2018

Introduction Lithium remains the best-established long-term treatment for bipolar disorder because of its efficacy in maintaining periods of remission and reducing the risk of suicide. Not all patients successfully respond to lithium treatment, and the individual response, including the occurrence of side effects, is highly variable and not easy to predict. The genetic basis of lithium response is supported by the fact that the response clusters in families. Likewise, recent high-throughput genomic analyses have shed light on its genetic architecture.

Methods This nonsystematic review summarizes the main results obtained in genetic association studies using lithium response as target trait.

Results These studies suggest that several genetic loci might modulate the way a patient responds to lithium maintenance treatment. Further studies to fully characterize the genetic architecture of lithium response are warranted.

Discussion The identification of genetic factors associated with lithium response will be important for (1) better understanding of lithium’s mode of action and (2) development of a predictive model for optimization of long-term treatment of bipolar disorder.
Antimicrobial Essential Oil Combinations to Combat Foot Odour
Authors: Orchard Ané , Viljoen Alvaro , van Vuuren Sandy
Published: March 2018

Foot odour (bromodosis) is an embarrassing and perplexing condition mostly caused by bacteria of the Brevibacterium species. Essential oils are a credible option as an affordable treatment of odour and contribute towards antimicrobial efficacy. Therefore, this study sets out to investigate the antimicrobial activity of essential oil combinations against odour-causing bacteria. The broth microdilution method was used to investigate the antimicrobial activity of 119 essential oil combinations, and the fractional inhibitory index was calculated to determine the interactive profile. Combinations that resulted in synergy in 1 : 1 ratios were further evaluated in different concentrations, and isobolograms were plotted to determine the influence of the ratio on overall activity. Numerous combinations could be identified as having synergistic interactions against the Brevibacterium spp. and no antagonism was observed. The combination of Juniperus virginiana (juniper) and Styrax benzoin (benzoin) demonstrated synergy against all three Brevibacterium spp. tested and J. virginiana was the essential oil responsible for the majority of the synergistic interactions. The results reported here confirm the promising potential of the majority of these oils and selected combinations in treating and controlling bromodosis.
Immunosuppression: Have We Learnt Anything?
Authors: Hachem Ramsey
Published: March 2018

Outcomes after lung transplantation remain disappointing because there is a high incidence of chronic lung allograft dysfunction (CLAD), which typically follows a progressive clinical course and often results in allograft failure and death. Chronic rejection is considered the predominant cause of CLAD. Thus, optimal immunosuppression has been viewed as having the potential to prevent CLAD and improve survival after lung transplantation. Numerous clinical trials have been conducted investigating the efficacy and safety of various immunosuppressive agents. Many studies have been small and single-center clinical trials but some have been international and multicenter trials enrolling more than 300 patients. This review focuses on clinical trials of immunosuppression conducted in lung transplantation and points out strengths and limitations of the various studies. Ultimately, the findings of these clinical trials explain the current state of practice in lung transplantation and identify gaps in knowledge that require additional study. Finally, there is an ongoing need for carefully designed and conducted clinical trials to improve clinical practice and outcomes after lung transplantation.
Procedural Results and Immediate Outcomes following De Novo Saphenous Venous Graft Interventions
Authors: Jyotsna Maddury , D. Malleswara , Nemani Lalita
Published: March 2018

Background Distal embolization is the detrimental factor in SVG intervention. There is no specific treatment for it except prevention. Guidelines have endorsed the use of embolic protection devices; however, their use is not without complications, and increases the procedural time and cost for the patient.

The objective of this study is to analyze the procedural results and immediate outcome in de novo SVG stenting.

Methods A retrospective observational study of patients who have undergone SVG-percutaneous coronary intervention at our institute. Baseline clinical, demographic data, intervention details, and in-hospital events are analyzed. Statistical analysis was done using Mini tab version 17. Chi-square testing, odds ratio, and 95% confidence intervals were calculated.

Results The study population included 96 lesions in 80 patients. Average age of the graft was 8.2 ± 4 years. Embolic protection devices were used only in 10%. Angiographic and clinical success was seen in 92.5%. Distal embolization was seen in 7.5%. Drug-eluting stent and shorter stents were associated with lesser distal embolization. Stent length (> 20 mm) proved to be an independent predictor of distal embolization. There was no correlation between distal embolization and age of patient, sex, hypertension, diabetes, and smoking, left ventricular function, age of graft, direct stenting, use of embolic device, and glycoprotein 2b/3a inhibitors.

Conclusion De novo SVG lesions can be stented with a high rate of angiographic and procedural success. Stent length is the only independent predictor of distal embolization. SVG interventions can be safely done in the absence of embolic protection devices irrespective of the graft age.
Free-Flap Lower Extremity Reconstruction: A Cohort Study and Meta-Analysis of Flap Anastomotic Outcomes between Perforator and Nonperforator Flaps
Authors: Song Christopher , Koh Keith , Tan Bien-Keem , Goh Terence
Published: March 2018

Introduction Free-flap outcomes in lower extremity reconstruction carry the lowest anastomotic success rates compared with other anatomical sites. Despite their advantages over traditional nonperforator flaps, free perforator flaps have only recently become established in this area due to the additional challenges faced. It is therefore crucial to assess the anastomotic outcomes of perforator and nonperforator free flaps.

Methods We performed a single-center retrospective cohort study and combined this with a meta-analysis of the relevant literature. We evaluated three flap anastomotic outcomes: reexploration, operative salvage, and flap failure rates.

Results Between January 2010 and June 2015, our center managed 161 patients who underwent lower extremity free-flap reconstruction, which included 76 perforator flaps and 85 nonperforator flaps. The perforator flaps had higher reexploration rates compared with the nonperforator flaps, but this was not statistically significant (18.4 and 10.6%; p = 0.18). Perforator flaps had a higher flap salvage rate but were not statistically significant (78.6 and 22.2%; p = 0.374). Lastly, although not statistically significant, perforator flaps had a lower rate of complete failure due to anastomotic complications (3.9 and 8.2%; p = 0.336). The meta-analysis included 12 studies (inclusive of the index study) and found no statistical difference in all three outcomes.

Conclusion Our meta-analysis is the first reported study and serves as an indication that free perforator flaps in lower extremity are as reliable as their traditional nonperforator counterparts. This does come with the prerequisite appreciation of the anatomical variations, the delicate handling of these flaps, and a low threshold for reexploration.
Recurrent 8-Year Ongoing Unilateral Breast Seroma Formation after PIP Implant Removal—A Case Report and Review of the Literature
Authors: Kästner Sonja , Paprottka Felix , Gonser Phillipp , López Manuel , Kaye Kai
Published: March 2018

Late seroma formation is a rare complication after implant-based breast enlargement surgery and even less frequent after implant removal. This case report presents a case of painful recurrent seroma formation after the removal of a ruptured Poly Implants Prothèse implant.

A 52-year-old patient presented herself in our clinic with a clinical history of recurrent unilateral seroma of the right breast over a period of 8 years after the initial unilateral implant removal. Removal of the remaining implant and complete bilateral capsulectomy was performed. Intraoperative findings revealed a macroscopically thickened capsule with signs of chronic inflammation on the affected side. The clinical history and the macroscopic appearance of the capsule demanded histopathological exclusion of a possible anaplastic large cell lymphoma.

Histopathological and microbiological analysis of the capsule and encapsulated material revealed no signs of malignancy or infection. Immediate soft tissue reconstruction of the breast was successfully performed using autologous fat transfer. An aesthetically satisfying result regarding symmetry and volume was achieved, and no further seroma formation was observed within a 6-month follow-up period.

Level of evidence: V, Case Report.