20 research outputs found
Yang-Mills Theory as a Deformation of Topological Field Theory, Dimensional Reduction and Quark Confinement
We propose a reformulation of Yang-Mills theory as a perturbative deformation
of a novel topological (quantum) field theory. We prove that this reformulation
of the four-dimensional QCD leads to quark confinement in the sense of area law
of the Wilson loop. First, Yang-Mills theory with a non-Abelian gauge group G
is reformulated as a deformation of a novel topological field theory. Next, a
special class of topological field theories is defined by both BRST and
anti-BRST exact action corresponding to the maximal Abelian gauge leaving the
maximal torus group H of G invariant. Then we find the topological field theory
() has a hidden supersymmetry for a choice of maximal Abelian gauge. As a
result, the D-dimensional topological field theory is equivalent to the
(D-2)-dimensional coset G/H non-linear sigma model in the sense of Parisi and
Sourlas dimensional reduction. After maximal Abelian gauge fixing, the
topological property of magnetic monopole and anti-monopole of four-dimensional
Yang-Mills theory is translated into that of instanton and anti-instanton in
two-dimensional equivalent model. It is shown that the linear static potential
in four-dimensions follows from the instanton--anti-instanton gas in the
equivalent two-dimensional non-linear sigma model obtained from the
four-dimensional topological field theory by dimensional reduction, while the
remaining Coulomb potential comes from the perturbative part in
four-dimensional Yang-Mills theory. The dimensional reduction opens a path for
applying various exact methods developed in two-dimensional quantum field
theory to study the non-perturbative problem in low-energy physics of
four-dimensional quantum field theories.Comment: 58 pages, Latex, no figures, version accepted for publication in
Phys. Rev. D (additions of Discussion, references and minor changes
Large-order NSPT for lattice gauge theories with fermions:the plaquette in massless QCD
Numerical Stochastic Perturbation Theory (NSPT) allows for perturbative
computations in quantum field theory. We present an implementation of NSPT that
yields results for high orders in the perturbative expansion of lattice gauge
theories coupled to fermions. The zero-momentum mode is removed by imposing
twisted boundary conditions; in turn, twisted boundary conditions require us to
introduce a smell degree of freedom in order to include fermions in the
fundamental representation. As a first application, we compute the critical
mass of two flavours of Wilson fermions up to order in a
gauge theory. We also implement, for the first time,
staggered fermions in NSPT. The residual chiral symmetry of staggered fermions
protects the theory from an additive mass renormalisation. We compute the
perturbative expansion of the plaquette with two flavours of massless staggered
fermions up to order in a gauge theory, and
investigate the renormalon behaviour of such series. We are able to subtract
the power divergence in the Operator Product Expansion (OPE) for the plaquette
and estimate the gluon condensate in massless QCD. Our results confirm that
NSPT provides a viable way to probe systematically the asymptotic behaviour of
perturbative series in QCD and, eventually, gauge theories with fermions in
higher representations.Comment: 49 pages, 28 figures. Revised version, to be published in EPJC. Some
references added, typos corrected, and improved discussion on finite-volume
effect
Flow cytometric analysis of cellular changes in mice after intradermal inoculation with a liposome-iscom adjuvanted vaccine
As it is not known what changes to leucocyte homeostasis are mandatory for effective adjuvant action, the biological relevance of systemic changes elicited by different vaccine formulations can only be interpreted in the context of the immunological outcomes. We used flow cytometry to quantify the changes in leucocyte subsets induced in mice intradermally immunized with SAMA4 (adjuvant group), outer membrane proteins (OMP) purified from Actinobacillus pleuropneumoniae (OMP antigen group), SAMA4 adjuvanted OMP (OMP vaccine group), or phosphate-buffered saline (PBS: control group). This approach allowed direct comparisons to be made between the effects of antigen, adjuvant or antigen-adjuvant complexes on immune effector cell populations. Antigens complexed with the liposome-iscom hybrid adjuvant, SAMA4, generated strong antibody responses and cytotoxic T-cell activity in animals immunized intradermally, reflecting remobilization and recruitment of specific cell populations. Splenomegaly, due to granulocytosis, monocytosis and megakaryocytosis, was most prominent in the OMP vaccine group. Histological examination of spleen sections confirmed that these changes were due primarily to splenic haematopoiesis. Circulating numbers of granulocytes and monocytes increased significantly (
Time to get personal? The impact of researchersâ choices on the selection of treatment targets using the experience sampling methodology
One of the promises of the experience sampling methodology (ESM) is that it could be used to identify relevant targets for treatment, based on a statistical analysis of an individualâs emotions, cognitions and behaviors in everyday-life. A requisite for clinical implementation is that outcomes of person-centered analyses are not wholly contingent on the researcher performing them. To evaluate how much researchers vary in their analytical approach and to what degree outcomes vary based on analytical choices, we crowdsourced the analysis of one individual patientâs ESM data to 12 prominent research teams, asking them what symptom(s) they would advise the treating clinician to target in subsequent treatment. The dataset was from a 25-year-old male with a primary diagnosis of major depressive disorder and comorbid generalized anxiety disorder, who completed momentary assessments related to depression and anxiety psychopathology prior to psychotherapy. Variation was evident at different stages of the analysis, from preprocessing steps (e.g., variable selection, clustering, handling of missing data) to the type of statistics. Most teams did include a type of vector autoregressive model, which examines relations between variables (e.g., symptoms) over time. Although most teams were confident their selected targets would provide useful information to the clinician, not one advice was similar: both the number (0-16) and nature of selected targets varied widely. This study makes transparent that the selection of treatment targets based on personalized models using ESM data is currently highly conditional on subjective analytical choices and highlights key methodological issues that need to be addressed in moving toward clinical implementation.
Research proposal, data and materials: osf.io/h3djy
Many Analysts - ESM
The experience sampling methodology (ESM) has been positioned as a promising opportunity for personalized medicine in psychiatry. A requisite for moving ESM towards clinical practice is that outcomes of person-centered analyses are not contingent on the researcher. In this study, we crowdsourced the analysis of one individual patientâs ESM data to 12 prominent research teams to investigate how much researchers vary in their analytical approach towards individual time series data and to what degree outcomes vary based on analytical choices