bluuebunny/crossref_metadata_2025 huggingface dataset:
The opportunities for obtaining of the biogas on methane fermentation from marine algae biomass and water plant biomass
Authors: Jachniak Ewa , Chmura Joanna , Kuglarz Mariusz , Wiktor Józef
Published: March 2018

The aim of the research was to try to obtain of the biogas on a laboratory scale from marine algae biomass and water plant biomass. The research was conducted in 2016 year and samples were taken from the Polish coast of the Baltic Sea. In laboratory work, algae and plant species were first identified. The next, in order to subject them to methane fermentation processes and to obtain biogas,partial mechanical treatment of the biomass was conducted. Dry matter content and dry organic matter content were also determined. The research has shown different production of the biogas depending on the various species of the algae and plants. The percentage composition of the biogas was also determined (% CO2and % CH4). In this research some kinds and species of algae and aquatic plants were distinguished:Scytosiphon cf. S. tortilis, Fucus vesiculosus, Cladophora, Audouinella, Potamogeton perfoliatus. Production of biogas from selected algae and water plants oscillated between 0.023 dm3·g-1and 0.303 dm3·g-1. The highest content of the methane in biogas was obtained from the mixture of Ectocarpus from spring and autumn harvest (values oscillated from 80.7 % to 81.2 %), while the highest percentage share of carbon dioxide in the biogas was characterized by the mixtureFucus vesiculosusandAudouinella(22 %). Due to a small amount of the research in this field, more research is needed.
Root system architecture in winter varieties of spelt (TriticumspeltaL.)
Authors: Żabiński Andrzej , Sadowska Urszula
Published: March 2018

The objective of the study was determination of the variability of morphometry and comparison of the morphological structure of the root system in winter cultivars of spelt. Four spelt cultivars were used in the study: Frankencorn, Oberkulmer Rotkorn, Schwabenkorn and Ostro. The material for the study originated from a field experiment. The roots were collected using the soil core method to the depth of 30 cm, from the rows and inter-rows, then the roots were separated using a semi-automatic hydropneumatic scrubber. The cleaned roots were manually separated and scanned, obtaining their digital images. Image analysis was performed using the Aphelion computer software. In order to characterize the root system of the spelt cultivars included in the study, values of the following indexes were determined: root dry mass (RDM), root length density (RLD), specific root length (SRL), mean root diameter (MD). Based on the obtained results it was determined that the RDM, MD and RLD indexes in all spelt cultivars attain the highest values in the row, at the depth 0–5 cm.The highest value of the RDM and MD indexes characterized the root system of the Ostro cultivar at the depth 0–5 cm. The Oberkulmerrotkorn spelt cultivar was distinguished among the tested objects by the highest value of the SRL index.
The effect of conditions and storage time on course of moisture and temperature of maize grains
Authors: Angelovič Marek , Krištof Koloman , Jobbágy Ján , Findura Pavol , Križan Milan
Published: March 2018

Characteristics of stored cereals significantly affect the technical solution of individual storage facilities, as well as the technical appliances used to provide storage technologies, i.e. storing aeration and off-loading. The objective of the study was to monitor the influence of atmospheric temperature and extraneous moisture on the course of temperature and moisture of maize grain during the storage. An average value of maize grain moisture was 13.6% and an average value of temperature inside of the silo was 12.3°C within a defined timeframe. An average moisture value of maize grain stored in the floored warehouse was 13.7%, but an average temperature inside the warehouse was 21.9°C, however extraneous conditions during the storage were unchanged. Average value of extraneous moisture was 86.5 % and an average value of atmospheric temperature was 9.17°C. It was not recorded any occurrence of animal pests in stored maize grain during the storage. Grain water content differs with the change of air moisture and temperature. Reduction of grain water content is most frequently realized by residual drying (moisture is less than 15%); the storage stability is provided at the moisture of 12%.
Effect of hydrothermal treated corn flour addition on the
quality of corn-field bean gluten-free pasta
Authors: Dib Ahlem , Wójtowicz Agnieszka , Benatallah Leila , Bouasla Abdallah , Zidoune Mohammed Nasreddine
Published: March 2018

Corn semolina supplemented by field bean semolina in ratio of 2/1 (w/w) were used for obtaining protein and fiber enriched gluten-free pasta. The effect of hydrothermal treatment of corn flour on its applicability as gluten-free pasta improver was tested. A central composite design involving water hydration level and the amount of hydrothermal treated corn flour were used. Instrumental analyses of pasta (cooking loss, water absorption capacity, hydration and pasting properties, textural parameters and microstructure) were carried out to assess the impact of experimental factors. Results showed that hydrothermal treatment of corn flour affected in different extent on pasta properties, improving cooking and textural characteristics of pasta. The optimum formulation of corn-field bean contained 7.41 g of treated corn flour and 77.26 mL of water was selected on the base of desirability function approach with value of 0.825 which showed the best pasta properties. Obtained results showed also that addition of treated flour induced significant differences (p < 0.05) in all parameters in comparison with control pasta.
Quality assessment of solid biofuel made of sweet sorghum biomass
Authors: Ivanova Tatiana , Muntean Alexandru , lHavrland Bohumi , Hutla Petr
Published: March 2018

The present article relates to assessment of energy utilization of sweet sorghum waste biomass as solid biofuel (briquettes). The briquettes were produced from biomass of pure sweet sorghum after juice extraction, mixture of sorghum with wood sawdust (ratio 1:1) and mixture of sorghum with wood shavings (ratio 1:1). Chemical, physical and mechanical properties of produced briquettes were measured in accordance with appropriate standards. The research results showed that the mixed sorghum briquettes with wood shavings have the highest mechanical durability and the lowest ash content; on the other hand, briquettes made of sweet sorghum and wood sawdust havethe best values of all other parameters, including higher calorific values, density, etc. Although addition of residual wood biomass improved the general quality of sorghum based briquettes, it was stated that the briquettes made of pure processed sorghum stalks belong to the category of high quality agricultural solid biofuels. It can be concluded that sweet sorghum is of very good prospects and thus it is a promising biomass feedstock for solid biofuels production (not only for the production of liquid biofuel as it has been used by today and has been known before).
The concept of algorithm supporting the process of scheduling production tasks
Authors: Knapczyk Adrian , Francik Sławomir , Ślipek Zbigniew
Published: March 2018

The purpose of the work was to develop a concept of an algorithm which supports the process of scheduling production tasks. The designed algorithm performs a task queue creation process in six steps: selecting a schedule type, declaring a queue length, selecting orders for queue development, loading data, automatic job analysis, and queue and Gantt chart generation, taking a decision on the acceptance of the designed production program. The designed system will use single-attribute priority rules (defined by experts) and multi-attribute rules that can be created by combining single-attribute rules. The concept of an algorithm that supports the process of scheduling production tasks, developed and tested by conducting simulations, can be the basis for developing a computer application supporting decision-making process in a manufacturing or service company.
Organizational and technological compatibility of the technological processes of second and third line maintenance of KhTZ-3522 tractors
Authors: Kyzminskyj Roman , Barabash Ruslan
Published: March 2018

The work is devoted to systematic substantiation of productivity, production structure and specialization of service stations of KhTZ-3522 tractors. Based on the technical and economic comparative analysis of the results of the technological processes modeling of the second and third line maintenance of KhTZ-3522 tractors, the parametrical series of production structures of service stations both mono- and polytechnological specialization, which can work effectively in a wide range of the general annual program of orders, and in the conditions of seasonal fluctuations of orders for the maintenance of these tractors, are found. The results of calculations of the indicators system for organizational and technological compatibility of technological processes of the second and third line maintenance of KhTZ-3522 tractors in the joint technological flow are presented. The dependencies of these indicators on the total annual program of orders for service stations of different productivity are analyzed. According to the results of the analysis, the polytechnological specialization of such service stations is substantiated.
Quality of dried cauliflower according to the methods and drying parameters
Authors: Łapczyńska-Kordon Bogusława , Krzysztofik Barbara , Sobol Zygmunt
Published: March 2018

The quality of food products is a complex concept. It can be defined in many ways. The common element of most of these definitions is the condition of meeting the requirements of consumers. Quality determines product compliance with the requirements set by the normalized regulations. The paper attempts to determine the optimal method and parameters of cauliflower drying. In addition, a qualitative assessment of the obtained product was made. The results show that the method and parameters of drying significantly affect the quality of the dried cauliflower. Convection drying guarantees higher drought quality with respect to the color of the sample (higher brightness), taste and odor. Of the drying parameters accepted in the experiment, the most positive effect on the tested parameters was recorded using convection drying at a flow rate of 0.2 ms-1and the least favorable for microwave drying 170 or 210 W.
Effect of biomaterials and working pressure of a briquetting machine on physical characteristics and energy consumption of briquette production
Authors: Niedziółka Ignacy , Sprawka Maciej , Zaklika Beata , Kraszkiewicz Artur , Przywara Artur
Published: March 2018

The paper presents an analysis of the influence of biomaterials and working pressure of a briquetting machine on physical characteristics and energy consumption of briquette production. The following types of biomaterials were used in the study: rape, oat and maize straw. Hydraulic piston briquetting machine JUNIOR manufactured by Deta Polska was used for briquetting. During the briquetting process, the working pressures of briquetting machine were 20, 26 and 32 MPa. Depending on the type of biomaterial used and the assumed working pressure of briquetting machine, produced briquettes differed in terms of both their physical characteristics and energy consumption. Based on the analysis of the obtained results, it was found that physical characteristics and energy consumption during briquette production were influenced by such factors as the type of compacted material, its fragmentation as well as granulometric composition and working pressure of the briquetting machine used.
Analysis of the distribution of the raw material base for biogas production in communes of the małopolskie voivodship
Authors: Sikora Jakub , Leśniak Edyta
Published: March 2018

The purpose of the work was to determine the electricity production potential of the available fermentation masses of selected organic fractions in the Małopolskie voivodship, as aggregated at the commune level. The determined potential of biomass production for energy purposes was presented in the form of a spatial distribution, based on data obtained from the queries of the Central Statistical Office. The purpose of the correlation was to facilitate the analysis of the problem of creating agricultural biogas plants in the discussed area. The scope of the study included all communes in the Małopolskie voivodship, as well as public statistics on the sown acreage for cereals, maize, the number of population, the population of pigs and cattle, as well as municipal solid waste. The tool used in the study was the Biogas Calculator of the Masovian Energy Agency and the software for creating spatial databases, ArcView 10.2.1
The effect of UV-C stimulation of potato tubers and soaking of potato strips in water on density differences of intermediates for French-fry production
Authors: Sobol Zygmunt , Jakubowski Tomasz , Wrona Paulina
Published: March 2018

The paper describes the effect of UV-C stimulation of potato tubers and immersing of potato strips in water on differences in density of intermediate products for French-fry production. The density difference used for description of the experiment was defined as a relationship between the post-treatment density and pre-treatment density. The study was conducted on tubers of the Innovator variety. The studies of density changes induced by absorption of water involved measurements of the mass of potato strips in air and in water. Potato strips measured 10 × 10 mm and 60 mm in length. The strips were cut lengthwise along the longest tuber axis set between the proximal and distal tuber end. Water absorption was investigated by immersing strips in water (1) at a temperature of 20°C for 15 min and (2) at 40°C for 20 min. In addition, the study included the group (3) where strips were blanched at a temperature of 90°C for 2 min and a control group (0) which was not immersed in water. Potato tubers were irradiated by UV-C in the following ways: (1) irradiation on one side for 30 min, (2) irradiation on both sides for 15 min each, (0) control group (no irradiation). The studies were conducted at two dates: (0) after harvest and (1) after 3-month storage. Laboratory and storage experiments were conducted in 2016-2017. The density difference was statistically significantly influenced by storage time, UV-C stimulation and immersion conditions of potato strips. The density difference increased with the increase in storage duration of tubers, immersion duration of strips, water temperature (up to starch gelification temperature) and UV-C stimulation.
Multi-boson block factorization of fermions
Authors: Giusti Leonardo , Cè Marco , Schaefer Stefan
Published: March 2018

The numerical computations of many quantities of theoretical and phenomenological interest are plagued by statistical errors which increase exponentially with the distance of the sources in the relevant correlators. Notable examples are baryon masses and matrix elements, the hadronic vacuum polarization and the light-by-light scattering contributions to the muon g – 2, and the form factors of semileptonic B decays. Reliable and precise determinations of these quantities are very difficult if not impractical with state-of-the-art standard Monte Carlo integration schemes. I will review a recent proposal for factorizing the fermion determinant in lattice QCD that leads to a local action in the gauge field and in the auxiliary boson fields. Once combined with the corresponding factorization of the quark propagator, it paves the way for multi-level Monte Carlo integration in the presence of fermions opening new perspectives in lattice QCD. Exploratory results on the impact on the above mentioned observables will be presented.
The topological properties of QCD at high temperature: problems and perspectives
Authors: Bonati Claudio
Published: March 2018

Lattice computations are the only first principle method capable of quantitatively assessing the topological properties of QCD at high temperature, however the numerical determination of the topological properties of QCD, especially in the high temperature phase, is a notoriously difficult problem. We will discuss the difficulties encountered in such a computation and some strategies that have been proposed to avoid (or at least to alleviate) them.
Temperature-dependence of the QCD topological susceptibility
Authors: Kovacs Tamas G.
Published: March 2018

We recently obtained an estimate of the axion mass based on the hypothesis that axions make up most of the dark matter in the universe. A key ingredient for this calculation was the temperature-dependence of the topological susceptibility of full QCD. Here we summarize the calculation of the susceptibility in a range of temperatures from well below the finite temperature cross-over to around 2 GeV. The two main difficulties of the calculation are the unexpectedly slow convergence of the susceptibility to its continuum limit and the poor sampling of nonzero topological sectors at high temperature. We discuss how these problems can be solved by two new techniques, the first one with reweighting using the quark zero modes and the second one with the integration method.
Multigrid accelerated simulations for Twisted Mass fermions
Authors: Bacchio Simone , Alexandrou Constantia , Finkerath Jacob
Published: March 2018

Simulations at physical quark masses are affected by the critical slowing down of the solvers. Multigrid preconditioning has proved to deal effectively with this problem. Multigrid accelerated simulations at the physical value of the pion mass are being performed to generate Nf = 2 and Nf = 2 + 1 + 1 gauge ensembles using twisted mass fermions. The adaptive aggregation-based domain decomposition multigrid solver, referred to as DD-αAMG method, is employed for these simulations. Our simulation strategy consists of an hybrid approach of different solvers, involving the Conjugate Gradient (CG), multi-mass-shift CG and DD-αAMG solvers. We present an analysis of the multigrid performance during the simulations discussing the stability of the method. This significant speeds up the Hybrid Monte Carlo simulation by more than a factor 4 at physical pion mass compared to the usage of the CG solver.
Fighting topological freezing in the two-dimensional CPN−1 model
Authors: Hasenbusch Martin
Published: March 2018

We perform Monte Carlo simulations of the CPN−1 model on the square lattice for N = 10, 21, and 41. Our focus is on the severe slowing down related to instantons. To fight this problem we employ open boundary conditions as proposed by Lüscher and Schaefer for lattice QCD. Furthermore we test the efficiency of parallel tempering of a line defect. Our results for open boundary conditions are consistent with the expectation that topological freezing is avoided, while autocorrelation times are still large. The results obtained with parallel tempering are encouraging.
DD-αAMG on QPACE 3
Authors: Georg Peter , Richtmann Daniel , Wettig Tilo
Published: March 2018

We describe our experience porting the Regensburg implementation of the DD-αAMG solver from QPACE 2 to QPACE 3. We first review how the code was ported from the first generation Intel Xeon Phi processor (Knights Corner) to its successor (Knights Landing). We then describe the modifications in the communication library necessitated by the switch from InfiniBand to Omni-Path. Finally, we present the performance of the code on a single processor as well as the scaling on many nodes, where in both cases the speedup factor is close to the theoretical expectations.
Testing algorithms for critical slowing down
Authors: Cossu Guido , Boyle Peter , Christ Norman , Jung Chulwoo , Jüttner Andreas , Sanfilippo Francesco
Published: March 2018

We present the preliminary tests on two modifications of the Hybrid Monte Carlo (HMC) algorithm. Both algorithms are designed to travel much farther in the Hamiltonian phase space for each trajectory and reduce the autocorrelations among physical observables thus tackling the critical slowing down towards the continuum limit. We present a comparison of costs of the new algorithms with the standard HMC evolution for pure gauge fields, studying the autocorrelation times for various quantities including the topological charge.
Phase diagram and Chiral Magnetic Effect in Dirac Semimetals from Lattice Simulation
Authors: Boyda D.L. , Braguta V.V. , Katsnelson M.I. , Kotov A.Yu.
Published: March 2018

Dirac Semimetals Na3Bi and Cd3As2 are recently discovered materials, which low energy electronic spectrum is described by two flavours of massless 3+1D fermions. In order to study electronic properties of these materials we formulated lattice field theory with rooted staggered fermions on anisotropic lattice. It is shown that in the limit of zero temporal lattice spacing this theory reproduces effective theory of Dirac semimetals. Using the lattice field theory we study the phase diagram of Dirac semimetals in the plane effective coupling constant - Fermi velocity anisotropy. We also measure conductivity of Dirac Semimetals within lattice field theory in external magnetic field. Our results confirm the existence of Chiral Magnetic Effect in Dirac Semimetals.
Dynamics of entanglement entropy of interacting fermions in a 1D driven harmonic trap
Authors: McKenney Joshua R. , Porter William J. , Drut Joaquín E.
Published: March 2018

Following up on a recent analysis of two cold atoms in a time-dependent harmonic trap in one dimension, we explore the entanglement entropy of two and three fermions in the same situation when driven through a parametric resonance. We find that the presence of such a resonance in the two-particle system leaves a clear imprint on the entanglement entropy. We show how the signal is modified by attractive and repulsive contact interactions, and how it remains present for the three-particle system. Additionaly, we extend the work of recent experiments to demonstrate how restricting observation to a limited subsystem gives rise to locally thermal behavior.
Direct detection of metal-insulator phase transitions using the modified Backus-Gilbert method
Authors: Ulybyshev Maksim , Winterowd Christopher , Zafeiropoulos Savvas
Published: March 2018

The detection of the (semi)metal-insulator phase transition can be extremely difficult if the local order parameter which characterizes the ordered phase is unknown. In some cases, it is even impossible to define a local order parameter: the most prominent example of such system is the spin liquid state. This state was proposed to exist in the Hubbard model on the hexagonal lattice in a region between the semimetal phase and the antiferromagnetic insulator phase. The existence of this phase has been the subject of a long debate. In order to detect these exotic phases we must use alternative methods to those used for more familiar examples of spontaneous symmetry breaking. We have modified the Backus-Gilbert method of analytic continuation which was previously used in the calculation of the pion quasiparticle mass in lattice QCD. The modification of the method consists of the introduction of the Tikhonov regularization scheme which was used to treat the ill-conditioned kernel. This modified Backus-Gilbert method is applied to the Euclidean propagators in momentum space calculated using the hybrid Monte Carlo algorithm. In this way, it is possible to reconstruct the full dispersion relation and to estimate the mass gap, which is a direct signal of the transition to the insulating state. We demonstrate the utility of this method in our calculations for the Hubbard model on the hexagonal lattice. We also apply the method to the metal-insulator phase transition in the Hubbard-Coulomb model on the square lattice.
SU(3) breaking and the pseudo-scalar spectrum in multi-taste QCD
Authors: Creutz Michael
Published: March 2018

Using the Sigma model to explore the lowest order pseudo-scalar spectrum with SU(3) breaking, this talk considers an additional exact “taste” symmetry to mimic species doubling. Rooting replicas of a valid approach such as Wilson fermions reproduces the desired physical spectrum. In contrast, extra symmetries of the rooted staggered approach leave spurious states and a flavor dependent taste multiplicity.
The Chiral Separation Effect in quenched finite-density QCD
Authors: Puhr Matthias , Buividovich Pavel
Published: March 2018

We present results of a study of the Chiral Separation Effect (CSE) in quenched finite-density QCD. Using a recently developed numerical method we calculate the conserved axial current for exactly chiral overlap fermions at finite density for the first time. We compute the anomalous transport coeffcient for the CSE in the confining and deconfining phase and investigate possible deviations from the universal value. In both phases we find that non-perturbative corrections to the CSE are absent and we reproduce the universal value for the transport coeffcient within small statistical errors. Our results suggest that the CSE can be used to determine the renormalisation factor of the axial current.
Distribution of the Dirac modes in QCD
Authors: Catillo M. , Glozman L. Ya.
Published: March 2018

It was established that distribution of the near-zero modes of the Dirac operator is consistent with the Chiral Random Matrix Theory (CRMT) and can be considered as a consequence of spontaneous breaking of chiral symmetry (SBCS) in QCD. The higherlying modes of the Dirac operator carry information about confinement physics and are not affected by SBCS. We study distributions of the near-zero and higher-lying modes of the overlap Dirac operator within NF = 2 dynamical simulations. We find that distributions of both near-zero and higher-lying modes are the same and follow the Gaussian Unitary Ensemble of Random Matrix Theory. This means that randomness, while consistent with SBCS, is not a consequence of SBCS and is related to some more general property of QCD in confinement regime.
Global Symmetries of Naive and Staggered Fermions in Arbitrary Dimensions
Authors: Kieburg Mario , Würfel Tim R.
Published: March 2018

It is well-known that staggered fermions do not necessarily satisfy the same global symmetries as the continuum theory. We analyze the mechanism behind this phenomenon for arbitrary dimension and gauge group representation. For this purpose we vary the number of lattice sites between even and odd parity in each single direction. Since the global symmetries are manifest in the lowest eigenvalues of the Dirac operator, the spectral statistics and also the symmetry breaking pattern will be affected. We analyze these effects and compare our predictions with Monte-Carlo simulations of naive Dirac operators in the strong coupling limit. This proceeding is a summary of our work [1].
Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology
Authors: Azcoiti Vicente
Published: March 2018

The axion is one of the more interesting candidates to make the dark matter of the universe, and the axion potential plays a fundamental role in the determination of the dynamics of the axion field. Moreover, the way in which the U(1)A anomaly manifests itself in the chiral symmetry restored phase of QCD at high temperature could be tested when probing the QCD phase transition in relativistic heavy ion collisions. With these motivations, we investigate the physical consequences of the survival of the effects of the U(1)A anomaly in the chiral symmetric phase of QCD, and show that the free energy density is a singular function of the quark mass m, in the chiral limit, and that the σ and π susceptibilities diverge in this limit at any T ≥ Tc. We also show that the difference between the π and δ susceptibilities diverges in the chiral limit at any T ≥ Tc, a result that can be contrasted with the existing lattice calculations; and discuss on the generalization of these results to the Nf ≥ 3 model.
Lattice QCD with mixed action – Borici-Creutz valence quark on staggered sea
Authors: Basak Subhasish , Goswami Jishnu , Chakrabarti Dipankar
Published: March 2018

Mixed action lattice QCD with Borici-Creutz valence quarks on staggered sea is investigated. The counter terms in Borici-Creutz action are fixed nonperturbatively to restore the broken symmetries. On symmetry restoration, the usual signatures of partial quenching / unitarity violation like negative scalar correlator are observed. The size of unitarity violation due to different discretization of valence and sea quark is determined by measuring Δmix.
Chiral Extrapolations of the ρ(770) Meson in Nf = 2 + 1 Lattice QCD Simulations
Authors: Molina R. , Hu B. , Doering M. , Mai M. , Alexandru A.
Published: March 2018

Several lattice QCD simulations of meson-meson scattering in p-wave and Isospin = 1 in Nf = 2 + 1 flavours have been carried out recently. Unitarized Chiral Perturbation Theory is used to perform extrapolations to the physical point. In contrast to previous findings on the analyses of Nf = 2 lattice data, where most of the data seems to be in agreement, some discrepancies are detected in the Nf = 2 + 1 lattice data analyses, which could be due to different masses of the strange quark, meson decay constants, initial constraints in the simulation, or other lattice artifacts. In addition, the low-energy constants are compared to the ones from a recent analysis of Nf = 2 lattice data.
Scattering from finite-volume energies including higher partial waves and multiple decay channels
Authors: Brett Ruairí , Bulava John , Fallica Jacob , Hanlon Andrew , Hörz Ben , Morningstar Colin , Singha Bijit
Published: March 2018

A new implementation of estimating the two-to-two K-matrix from finitevolume energies based on the Luescher formalism is described. The method includes higher partial waves and multiple decay channels, and the fitting procedure properly includes all covariances and statistical uncertainties. The method is also simpler than previously used procedures. Formulas and software for handling total spins up to S = 2 and orbital angular momenta up to L = 6 are presented.
Sanity check for NN bound states in lattice QCD with Lüscher’s finite volume formula – Disclosing Symptoms of Fake Plateaux –
Authors: Aoki Sinya , Doi Takumi , Iritani Takumi
Published: March 2018

The sanity check is to rule out certain classes of obviously false results, not to catch every possible error. After reviewing such a sanity check for NN bound states with the Lüscher’s finite volume formula [1–3], we give further evidences for the operator dependence of plateaux, a symptom of the fake plateau problem, against the claim [4]. We then present our critical comments on [5] by NPLQCD: (i) Operator dependences of plateaux in NPL2013 [6, 7] exist with the P value of 4–5%. (ii) The volume independence of plateaux in NPL2013 does not prove their correctness. (iii) Effective range expansions (EREs) in NPL2013 violate the physical pole condition. (iv) Their comment is partly based on new data and analysis different from the original ones. (v) Their new ERE does not satisfy the Lüscher’s finite volume formula.
ρ resonance from the I = 1 ππ potential in lattice QCD
Authors: Kawai Daisuke
Published: March 2018

We calculate the phase shift for the I = 1 ππ scattering in 2+1 flavor lattice QCD at mπ = 410 MeV, using all-to-all propagators with the LapH smearing. We first investigate the sink operator independence of the I = 2 ππ scattering phase shift to estimate the systematics in the LapH smearing scheme in the HAL QCD method at mπ = 870 MeV. The difference in the scattering phase shift in this channel between the conventional point sink scheme and the smeared sink scheme is reasonably small as long as the next-toleading analysis is employed in the smeared sink scheme with larger smearing levels. We then extract the I = 1 ππ potential with the smeared sink operator, whose scattering phase shift shows a resonant behavior (ρ resonance). We also examine the pole of the S-matrix corresponding to the ρ resonance in the complex energy plane.
Glueball relevant study on isoscalars from Nf = 2 lattice QCD
Authors: Sun Wei , Gui Long-Cheng , Chen Ying , Gong Ming , Liu Zhaofeng
Published: March 2018

Abstract.We perform a glueball-relevant study on isoscalars based on anisotropic Nf = 2 lattice QCD gauge configurations. In the scalar channel, we identify the ground state obtained through gluonic operators to be a single-particle state through its dispersion relation. When qq operator is included, we find the mass of this state does not change, and the qq operator couples very weakly to this state. So this state is most likely a glueball state. For pseudoscalars, along with the exiting lattice results, our study implies that both the conventional qq state η2 (or η' in flavor SU(3)) and a heavier glueball-like state with a mass of roughly 2.6 GeV exist in the spectrum of lattice QCD with dynamical quarks.
More on heavy tetraquarks in lattice QCD at almost physical pion mass
Authors: Francis Anthony , Hudspith Renwick J. , Lewis Randy , Maltman Kim
Published: March 2018

We report on our progress in studying exotic, heavy tetraquark states, qq′ Q̅Q̅′. Using publicly available dynamical nf = 2 + 1 Wilson-Clover gauge configurations, generated by the PACS-CS collaboration, with pion masses ≃ 164, 299 and 415 MeV, we extend our previous analysis to heavy quark components containing heavier than physical bottom quarks Q̅Q̅′ = b̅′b̅′ or Q̅Q̅′ = b̅b̅′, charm and bottom quarks c̅b̅ and also only charm quarks c̅ c̅. Throughout we employ NRQCD and relativistic heavy quarks for the heavier than bottom, bottom and charm quarks. Using our previously established diquark-antidiquark and meson-meson operator basis we comment in particular on the dependence of the binding energy on the mass of the heavy quark component Q̅Q̅, with heavy quarks ranging from mQ = 0:85… 6.3 · mb. In the heavy flavor non-degenerate case, Q̅Q̅′, and especially for the tetraquark channel udc̅d̅, we extend our work to utilize a 3 × 3 GEVP to study the ground and threshold states thereby enabling a clear identification of possible binding. Finally, we present initial work on the Q̅Q̅′ = c̅c̅ system where a much larger operator basis is available in comparison to flavor combinations with NRQCD quarks.
Multi-hadron spectroscopy in a large physical volume
Authors: Bulava John , Hörz Ben , Morningstar Colin
Published: March 2018

We demonstrate the effcacy of the stochastic LapH method to treat all-toall quark propagation on a Nf = 2 + 1 CLS ensemble with large linear spatial extent L = 5:5 fm, allowing us to obtain the benchmark elastic isovector p-wave pion-pion scattering amplitude to good precision already on a relatively small number of gauge configurations. These results hold promise for multi-hadron spectroscopy at close-to-physical pion mass with exponential finite-volume effects under control.
Calm Multi-Baryon Operators
Authors: Berkowitz Evan , Nicholson Amy , Chang Chia Cheng , Rinaldi Enrico , Clark M.A. , Joó Bálint , Kurth Thorsten , Vranas Pavlos , Walker-Loud André
Published: March 2018

There are many outstanding problems in nuclear physics which require input and guidance from lattice QCD calculations of few baryons systems. However, these calculations suffer from an exponentially bad signal-to-noise problem which has prevented a controlled extrapolation to the physical point. The variational method has been applied very successfully to two-meson systems, allowing for the extraction of the two-meson states very early in Euclidean time through the use of improved single hadron operators. The sheer numerical cost of using the same techniques in two-baryon systems has so far been prohibitive. We present an alternate strategy which offers some of the same advantages as the variational method while being significantly less numerically expensive. We first use the Matrix Prony method to form an optimal linear combination of single baryon interpolating fields generated from the same source and different sink interpolating fields. Very early in Euclidean time this optimal linear combination is numerically free of excited state contamination, so we coin it a calm baryon. This calm baryon operator is then used in the construction of the two-baryon correlation functions.

To test this method, we perform calculations on the WM/JLab iso-clover gauge configurations at the SU(3) flavor symmetric point with mπ~ 800 MeV — the same configurations we have previously used for the calculation of two-nucleon correlation functions. We observe the calm baryon significantly removes the excited state contamination from the two-nucleon correlation function to as early a time as the single-nucleon is improved, provided non-local (displaced nucleon) sources are used. For the local two-nucleon correlation function (where both nucleons are created from the same space-time location) there is still improvement, but there is significant excited state contamination in the region the single calm baryon displays no excited state contamination.
Electromagnetic corrections to the hadronic vacuum polarization
of the photon within QEDL and QEDM
Authors: Bussone Andrea , Della Morte Michele , Janowski Tadeusz
Published: March 2018

We compute the leading QED corrections to the hadronic vacuum polarization (HVP) of the photon, relevant for the determination of leptonic anomalous magnetic moments, al. We work in the electroquenched approximation and use dynamical QCD configurations generated by the CLS initiative with two degenerate flavors of nonperturbatively O(a)-improved Wilson fermions. We consider QEDL and QEDM to deal with the finite-volume zero modes. We compare results for the Wilson loops with exact analytical determinations. In addition we make sure that the volumes and photon masses used in QEDM are such that the correct dispersion relation is reproduced by the energy levels extracted from the charged pions two-point functions. Finally we compare results for pion masses and the HVP between QEDL and QEDM. For the vacuum polarization, corrections with respect to the pure QCD case, at fixed pion masses, turn out to be at the percent level.
HVP contributions to the muon (g−2) including QED corrections with twisted-mass fermions
Authors: Giusti Davide , Lubicz Vittorio , Martinelli Guido , Sanfilippo Francesco , Simula Silvano
Published: March 2018

We present a lattice calculation of the Hadronic Vacuum Polarization (HVP) contribution of the strange and charm quarks to the anomalous magnetic moment of the muon including leading-order electromagnetic (e.m.) corrections. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf = 2+1 + 1 dynamical quarks at three values of the lattice spacing (a ≃ 0.062,0.082,0.089 fm) with pion masses in the range Mπ ≃ 210 - 450 MeV. The strange and charm quark masses are tuned at their physical values. Neglecting discon-nected diagrams and after the extrapolations to the physical pion mass and to the continuum limit we obtain: [see formula in PDF] and [see formula in PDF] for the strange and charm contributions, respectively.!
The current matrix elements from HAL QCD method
Authors: Watanabe Kai , Ishii Noriyoshi
Published: March 2018

HAL QCD method is a method to construct a potential (HAL QCD potential) that reproduces the NN scattering phase shift faithful to the QCD. The HAL QCD potential is obtained from QCD by eliminating the degrees of freedom of quarks and gluons and leaving only two particular hadrons. Therefor, in the effective quantum mechanics of two nucleons defined by HAL QCD potential, the conserved current consists not only of the nucleon current but also an extra current originating from the potential (two-body current). Though the form of the two-body current is closely related to the potential, it is not straight forward to extract the former from the latter. In this work, we derive the the current matrix element formula in the quantum mechanics defined by the HAL QCD potential. As a first step, we focus on the non-relativistic case. To give an explicit example, we consider a second quantized non-relativistic two-channel coupling model which we refer to as the original model. From the original model, the HAL QCD potential for the open channel is constructed by eliminating the closed channel in the elastic two-particle scattering region. The current matrix element formula is derived by demanding the effective quantum mechanics defined by the HAL QCD potential to respond to the external field in the same way as the original two-channel coupling model.
Electromagnetic form factors and axial charge of the nucleon fromNf= 2 + 1 Wilson fermions
Authors: Djukanovic Dalibor , Harris Tim , von Hippel Georg M. , Junnarkar Parikshit M. , Meyer Harvey B. , Wittig Hartmut
Published: March 2018

We present an update on our determination of the electromagnetic form factors and axial charge of the nucleon from theNf= 2 + 1 CLS ensembles with increased statistics and an additional finer lattice spacing. We also investigate the impact ofO(a)-improvement of the currents.
Numerical investigation of finite-volume effects for the HVP
Authors: Boyle Peter , Gülpers Vera , Harrison James , Jüttner Andreas , Portelli Antonin , Sachrajda Christopher
Published: March 2018

It is important to correct for finite-volume (FV) effects in the presence of QED, since these effects are typically large due to the long range of the electromagnetic interaction. We recently made the first lattice calculation of electromagnetic corrections to the hadronic vacuum polarisation (HVP). For the HVP, an analytical derivation of FV corrections involves a two-loop calculation which has not yet been carried out. We instead calculate the universal FV corrections numerically, using lattice scalar QED as an effective theory. We show that this method gives agreement with known analytical results for scalar mass FV effects, before applying it to calculate FV corrections for the HVP. This method for numerical calculation of FV effects is also widely applicable to quantities beyond the HVP.
Exploratory studies for the position-space approach to hadronic light-by-light scattering in the muon g - 2
Authors: Asmussen Nils , Gérardin Antoine , Meyer Harvey B. , Nyffeler Andreas
Published: March 2018

The well-known discrepancy in the muon g − 2 between experiment and theory demands further theory investigations in view of the upcoming new experiments. One of the leading uncertainties lies in the hadronic light-by-light scattering contribution (HLbL), that we address with our position-space approach. We focus on exploratory studies of the pion-pole contribution in a simple model and the fermion loop without gluon exchanges in the continuum and in infinite volume. These studies provide us with useful information for our planned computation of HLbL in the muon g − 2 using full QCD.
Perturbative Renormalization of Wilson line operators
Authors: Constantinou Martha , Panagopoulos Haralambos
Published: March 2018

We present results for the renormalization of gauge invariant nonlocal fermion operators which contain a Wilson line, to one loop level in lattice perturbation theory. Our calculations have been performed for Wilson/clover fermions and a wide class of Symanzik improved gluon actions. The extended nature of such ‘long-link’ operators results in a nontrivial renormalization, including contributions which diverge linearly as well as logarithmically with the lattice spacing, along with additional finite factors. We present nonperturbative prescriptions to extract the linearly divergent contributions.
Nucleon Axial and Electromagnetic Form Factors
Authors: Jang Yong-Chull , Bhattacharya Tanmoy , Gupta Rajan , Lin Huey-Wen , Yoon Boram
Published: March 2018

We present results for the isovector axial, induced pseudoscalar, electric, and magnetic form factors of the nucleon. The calculations were done using 2 + 1 + 1-flavor HISQ ensembles generated by the MILC collaboration with lattice spacings a ≈ 0.12, 0.09, 0.06 fm and pion masses Mπ ≈ 310, 220, 130 MeV. Excited-states contamination is controlled by using four-state fits to two-point correlators and by comparing two-versus three-states in three-point correlators. The Q2 behavior is analyzed using the model independent z-expansion and the dipole ansatz. Final results for the charge radii and magnetic moment are obtained using a simultaneous fit in Mπ, lattice spacing a and finite volume.
Landau levels in QCD in an external magnetic field
Authors: Bruckmann Falk , Endrődi Gergely , Giordano Matteo , Katz Sándor D. , Kovács Tamás G. , Pittler Ferenc , Wellnhofer Jacob
Published: March 2018

We will discuss the issue of Landau levels of quarks in lattice QCD in an external magnetic field. We will show that in the two-dimensional case the lowest Landau level can be identified unambiguously even if the strong interactions are turned on. Starting from this observation, we will then show how one can define a “plowest Landau level” in the four-dimensional case, and discuss how much of the observed effects of a magnetic field can be explained in terms of it. Our results can be used to test the validity of low-energy models of QCD that make use of the lowest-Landau-level approximation.
Complex Langevin simulation of QCD at finite density and low temperature using the deformation technique
Authors: Nagata Keitro , Nishimura Jun , Shimasaki Shinji
Published: March 2018

We study QCD at finite density and low temperature by using the complex Langevin method. We employ the gauge cooling to control the unitarity norm and intro-duce a deformation parameter in the Dirac operator to avoid the singular-drift problem. The reliability of the obtained results are judged by the probability distribution of the magnitude of the drift term. By making extrapolations with respect to the deformation parameter using only the reliable results, we obtain results for the original system. We perform simulations on a 43 × 8 lattice and show that our method works well even in the region where the reweighing method fails due to the severe sign problem. As a result we observe a delayed onset of the baryon number density as compared with the phase-quenched model, which is a clear sign of the Silver Blaze phenomenon.
Comparative studies of the deformation techniques for the singular-drift problem in the complex Langevin method
Authors: Ito Yuta , Nishimura Jun
Published: March 2018

In application of the complex Langevin method to QCD at high density and low temperature, the singular-drift problem occurs due to the appearance of near-zero eigenvalues of the Dirac operator. In order to avoid this problem, we proposed to de-form the Dirac operator in such a way that the near-zero eigenvalues do not appear and to extrapolate the deformation parameter to zero from the available data points. Here we test three different types of deformation in a simple large-N matrix model, which under-goes an SSB due to the phase of the fermion determinant, and compare them to see the consistency with one another.
Thermal modifications of charmonia and bottomonia from spatial correlation functions
Authors: Ding Heng-Tong , Kaczmarek Olaf , Kruse Anna-lena , Mukherjee Swagato , Ohno Hiroshi , Sandmeyer Hauke , Shu Hai-Tao
Published: March 2018

We present our study on the thermal modifications of charmonia and bottomonia from spatial correlation functions at zero and nonzero momenta in quenched QCD. To accommodate the heavy quarks on the lattice we performed simulations on very fine lattices at a fixed beta value corresponding to a lattice spacing a-1 = 22:8 GeV on 1923×32, 1923 × 48, 1923 × 56, 1923 × 64 and 1923 × 96 lattices using clover-improved Wilson fermions. These lattices correspond to temperatures of 2.25Tc, 1.50Tc, 1.25Tc, 1.10Tc and 0.75Tc. To increase the signal to noise ratio in the axial-vector and scalar channels we used multi-sources for the measurement of spatial correlation functions. By investigating on the differences between spatial and temporal correlators as well as the temperature dependence of screening masses we will discuss the thermal effects in different channels of quarkonium states. Besides this the dispersion relation of the screening mass at different momenta is also discussed.