Renormalization Processes Research Articles

Systematic improvement of x -dependent unpolarized nucleon generalized parton distributions in lattice-QCD calculation

We present a first study of the effects of renormalization-group resummation (RGR) and leading-renormalon resummation (LRR) on the systematic errors of the unpolarized isovector nucleon generalized parton distribution in the framework of large-momentum effective theory. This work is done using lattice gauge ensembles generated by the MILC Collaboration, consisting of 2+1+1 flavors of highly improved staggered quarks with a physical pion mass at lattice spacing a≈0.09 fm and a box width L≈5.76 fm. We present results for the nucleon H and E generalized parton distributions (GPDs) with average boost momentum Pz≈2 GeV at momentum transfers Q2=[0,0.97] GeV2 at skewness ξ=0 as well as Q2∈0.23 GeV2 at ξ=0.1, renormalized in the modified minimal subtraction (MS¯) scheme at scale μ=2.0 GeV, with two- and one-loop matching, respectively. We demonstrate that the simultaneous application of RGR and LRR significantly reduces the systematic errors in renormalized matrix elements and distributions for both the zero and nonzero skewness GPDs, and that it is necessary to include both RGR and LRR at higher orders in the matching and renormalization processes. Published by the American Physical Society 2024

Many-particle induced band renormalization processes in few- and mono-layer MoS2

Band renormalization effects play a significant role for two-dimensional (2D) materials in designing a device structure and customizing their optoelectronic performance. However, the intrinsic physical mechanism about the influence of these effects cannot be revealed by general steady-state studies. Here, band renormalization effects in organic superacid treated monolayer MoS2, untreated monolayer MoS2 and few-layer MoS2 are quantitatively analyzed by using broadband femtosecond transient absorption spectroscopy. In comparison with the untreated monolayer, organic superacid treated monolayer MoS2 maintains a direct bandgap structure with two thirds of carriers populated at K valley, even when the initial exciton density is as high as 2.05 × 1014 cm−2 (under 400 nm excitations). While for untreated monolayer and few-layer MoS2, many-particle induced band renormalizations lead to a stronger imbalance for the carrier population between K and Q valleys in k space, and the former experiences a direct-to-indirect bandgap transition when the initial exciton density exceeds 5.0 × 1013 cm−2 (under 400 nm excitations). Those many-particle induced band renormalization processes further suggest a band-structure-controlling method in practical 2D devices.

Work as management in an environment governed by standards: a study of situations in the steel industry

Abstract: This article aims to analyze the renormalization processes in work situations of technicians working in a testing laboratory of a steel company in Southeastern Brazil, explaining the contributions of the analytical perspective of Ergology when investigating how workers are organized to manage their activities in order to meet their production and quality goals, their personal as well as customer satisfaction, and protect themselves from work accidents. The qualitative research was carried out based on the analytical approach of Ergology, and the instruments used for data production were documentary investigation within the organization, direct observation of the activities, and semi-structured interviews with the participating workers. The data were treated using content analysis. It was found that these workers value standard operating procedures as tools to aid in the execution of their duties, but criticize them for being extensive, making consultation tiresome, and request more condensed, practical, and attractive procedures for handling. Research showed that certain unforeseen events in the process are only remedied by oneself and the other, demonstrating that the more complete a prescription is, collective experience fills any gaps, since the activity is more complex than anticipated by the standards. This study may contribute to a better understanding of situations common to the steel industry, as well as to academic progress, demarcating the importance of renormalizations not yet explored in this field of study – Ergology in the –Brazilian steel industry.

Numerical Verification of Dielectric Contactor as Auxiliary Loads for Measuring the Multi-Port Network Parameter of Vertical Interconnection Array

For the accurate and reliable multi-port characterization of vertical interconnection array structures, this paper presents an indirect-contact probing method to obtain network parameters of N-port device-under-tests (DUTs) using an M-port (N > M) vector network analyzer (VNA) with a dielectric contactor. By utilizing the dielectric contactor as auxiliary loads for un-probed ports for vertical interconnections, multiple M-port sub-array network parameters can be correctly synthesized into the N-port network parameters through the renormalization processes. To verify the proposed method, four-port DUTs for packaging and microwave applications were characterized with two-port indirect-contact probing sub-array simulations including the dielectric contactor. Compared with two-port direct-contact probing simulations without the dielectric contactor, it was confirmed that the proposed method with the dielectric contactor provides improved accuracy in terms of the feature selective validation (FSV) method.

Repeated Structural Imaging Reveals Nonlinear Progression of Experience-Dependent Volume Changes in Human Motor Cortex.

Evidence for experience-dependent structural brain change in adult humans is accumulating. However, its time course is not well understood, as intervention studies typically consist of only 2 imaging sessions (before vs. after training). We acquired up to 18 structural magnetic resonance images over a 7-week period while 15 right-handed participants practiced left-hand writing and drawing. After 4 weeks, we observed increases in gray matter of both left and right primary motor cortices relative to a control group; 3 weeks later, these differences were no longer reliable. Time-series analyses revealed that gray matter in the primary motor cortices expanded during the first 4 weeks and then partially renormalized, in particular in the right hemisphere, despite continued practice and increasing task proficiency. Similar patterns of expansion followed by partial renormalization are also found in synaptogenesis, cortical map plasticity, and maturation, and may qualify as a general principle of structural plasticity. Research on human brain plasticity needs to encompass more than 2 measurement occasions to capture expansion and potential renormalization processes over time.

Using The Potential Of Renormalization Processes In Teacher Education

Cet article analyse le potentiel de renormalisation contenu dans les dispositifs de formation « orientés activité » utilisant le visionnement de films montrant des enseignants au travail. Par renormalisation, nous entendons le travail permanent de renouvellement des règles d’élaboration de l’expérience et des règles à suivre dans l’action. Nous soumettons à analyse une séquence d’alloconfrontation et une séquence d’autoconfrontation simple suivie d’une autoconfrontation croisée produites dans le cadre d’une recherche menée à l’Université de Genève avec des enseignants secondaires en formation. Les processus de renormalisation identifiés font l’objet d’une description fine, suivant pas à pas le développement de l’interaction des enseignants avec les films visionnés. L’analyse montre que ces processus de renormalisation reposent sur un double mouvement d’explicitation de règles implicites et d’élaboration de conflits entre les règles personnelles et les règles du milieu (institution et attentes des pairs). Nous discutons ensuite le potentiel de ces processus pour la formation et proposons une ingénierie à même de les favoriser.

Growth of a Population of Bacteria in a Dynamical Hostile Environment

We study the growth of a population of bacteria in a dynamical hostile environment corresponding to the immune system of the colonized organism. The immune cells evolve as subcritical open clusters of oriented percolation and are perpetually reinforced by an immigration process, while the bacteria try to grow as a supercritical oriented percolation in the remaining empty space. We prove that the population of bacteria grows linearly when it survives. From this perspective, we build general tools to study dependent oriented percolation models issued from renormalization processes.

Growth of a Population of Bacteria in a Dynamical Hostile Environment

We study the growth of a population of bacteria in a dynamical hostile environment corresponding to the immune system of the colonized organism. The immune cells evolve as subcritical open clusters of oriented percolation and are perpetually reinforced by an immigration process, while the bacteria try to grow as a supercritical oriented percolation in the remaining empty space. We prove that the population of bacteria grows linearly when it survives. From this perspective, we build general tools to study dependent oriented percolation models issued from renormalization processes.

Effects which will not blur the message of the 1H (11Li, 9Li) 3H reaction: observation of phonon–exchange pairing correlations in nuclei

The results of the 1H (11Li, 9Li) 3H experiment carried out recently at TRIUMF have given detailed information concerning the structure and the reaction mechanism at work in the case of halo, exotic nuclei, providing important stepping stones for an eventual quantitative description of superfluidity in finite nuclei. In fact, the central role played by renormalization processes as testified by the excitation of the 1/2– (2.69 MeV) member of the 9Li (2+ ⊗p3/2(π))j− multiplet (nuclear structure) together with the post-prior symmetry (reaction), testify to the fact that a detailed knowledge of the "bare" quantities, like e.g. the NN-interaction is likely to be less important, in a unified Nuclear Field Theory description of the structure and the reaction aspects of the experiment, than previously thought.

Dynamics of mesoscopic systems: Non-equilibrium Green's functions approach

Recent developments in technologies and experiments enable us to observe dynamical behavior of very small quantum systems under conditions when it is sensitive to system parameters, internal interactions, the environment and the external time-dependent fields. This contribution deals with the status and perspectives of description of such truly non-equilibrium quantum many body systems using the non-equilibrium Green's functions (NGF). The basic aim of this approach is to describe time development of the many-body system out of equilibrium from its initial state over its transient dynamics to its long time asymptotic evolution. The early stages of the transient evolution will be characterized for a broad class of the initial conditions generated in the course of Keldysh switch-on states. Gradual loss of initial correlations due to interactions and related renormalization processes in the system may, under favorable conditions, give rise to the evolution stage expressible in terms of non-equilibrium quasi-particles. This permits to reduce the description of the system behavior to a quantum transport equation. The consistency of such approximations for NGF may be judged by checking the non-equilibrium version of transport Ward identities. These identities follow from the gauge invariance of the 1st kind for NGF. To cover the whole time domain of the transient, we obtain the non-equilibrium Ward identities for NGF with initial conditions included.

Proton radioactivity with analytically solvable potential

The phenomenon of proton emission is treated as a process of asymmetric fission through a one-dimensional potential barrier developed due to combined effects of the Coulomb potential, centrifugal potential and various renormalization processes. The barrier is simulated to an asymmetric, smooth and analytically solvable potential with adjustable depth, shape and range. The half-lives of proton emitters in the mass range A = 105–171 have been calculated using exact expression for the transmission coefficients. Good agreement with the experimental data is obtained by the adjustment of just one parameter in all the cases.

Distillation protocols for mixed states of multilevel qubits and the quantum renormalization group

We study several properties of distillation protocols to purify multilevel qubit states (qudits) when applied to a certain family of initial mixed bipartite states. We find that it is possible to use qudits states to increase the stability region obtained with the flow equations to distill qubits. In particular, for qutrits we get the phase diagram of the distillation process with a rich structure of fixed points. We investigate the large-$D$ limit of qudits protocols and find an analytical solution in the continuum limit. The general solution of the distillation recursion relations is presented in an appendix. We stress the notion of weight amplification for distillation protocols as opposed to the quantum amplitude amplification that appears in the Grover algorithm. Likewise, we investigate the relations between quantum distillation and quantum renormalization processes.

Renormalization processes in the charge density of polymer colloids

The spatial microstructure exhibited by charge stabilized colloidal dispersion at very low ionic strength has been determined using static light scattering. The obtained structure factors have been analyzed assuming a DLVO type effective particle–particle interaction potential, and with the aid of the Ornstein–Zernike equation and the hyper-netted-chain closure. The effective charges needed to fit the experimental data in this way are found to be considerably smaller than the total number of ionizable groups on the surface. In order to account for this behavior, two approaches have been taken. Firstly, a widely used charge renormalization approach was applied. It is based on the idea that the potentials derived with linear approximations underestimate the actual charge characterizing the interaction. The surface charge does not seem to be an appropriate input parameter for this model. Secondly, electrophoretic mobilities were measured and converted into ζ-potential (using the O’Brien–White theory). The electrokinetic charges were also calculated. A discussion in terms of these electrokinetic data is presented. The similar behavior found between the effective and electrokinetic charges seems to point out that not only the renormalization has to be considered, but also the structure of the electric double layer.

Gluonic enhancements in non-spectator beauty decays—an inclusive mirage though an exclusive possibility

It has been claimed that gluon emission can raise weak annihilation contributions to heavy quark decays by powers of ( m Q μ had ) , the ratio of the heavy quark mass to a light hadron mass scale. We show that such powerlike enhancements of annihilation, interference and other preasymptotic effects do not arise for fully inclusive transitions, only for partial rates. The leading corrections are then logarithmic; even so they are crucial for determining the impact of these effects. We establish a non-trivial relation between euclidean renormalization and real decay processes in Minkowski space. Phenomenological consequences are briefly discussed, e.g. we expect the B d and B − lifetimes to differ by only a few percent with interference being the maon driving force. The (hybrid) log corrections are essential for the degree of interference by effectively cancelling non-leading terms in a 1 N c expansion.