BRST quantization and canonical Ward identity of the supersymmetric electromagnetic interaction system

According to the method of path integral quantization for the canonical constrained system in Becchi-Rouet-Stora-Tyutin scheme, the supersymmetric electromagnetic interaction system was quantized. Both the Hamiltonian of the supersymmetric electromagnetic interaction system in phase space and the quantization procedure were simplified. The BRST generator was constructed, and the BRST transformations of supersymmetric fields were gotten; the effective action was calculated, and the generating functional for the Green function was achieved; also, the gauge generator was constructed, and the gauge transformation of the system was obtained. Finally, the Ward-Takahashi identities based on the canonical Noether theorem were calculated, and two relations between proper vertices and propagators were obtained.

Light-front zero-mode contribution to the Ward Identity

In a covariant gauge we implicitly assume that the Green's function propagates information from one point of the space-time to another, so that the Green's function is responsible for the dynamics of the relativistic particle. In the light front form one would naively expect, that this feature would be preserved. In this manner, the fermionic field propagator can be split into a propagating piece and a non-propagating (contact) term. Since the latter (contact) one does not propagate information; and therefore, supposedly can be discarded with no harm to the field dynamics we wanted to know what would be the impact of dropping it off. To do that, we investigated its role in the Ward identity in the light front. Here we use the terminology Ward identity to identify the limiting case of photon's zero momentum transfer in the vertex from the more general Ward-Takahashi identity with nonzero momentum transfer.

Structure constants of beta deformed super Yang-Mills

We study the structure constants of the N = 1 beta deformed theory perturbatively and at strong coupling. We show that the planar one loop corrections to the structure constants of single trace gauge invariant operators in the scalar sector is determined by the anomalous dimension Hamiltonian. This result implies that 3 point functions of the chiral primaries of the theory do not receive corrections at one loop. We then study the structure constants at strong coupling using the Lunin-Maldacena geometry. We explicitly construct the supergravity mode dual to the chiral primary with three equal U(1) R-charges in the Lunin-Maldacena geometry. We show that the 3 point function of this supergravity mode with semi-classical states representing two other similar chiral primary states but with large U(1) charges to be independent of the beta deformation and identical to that found in the AdS(5) x S-5 geometry. This together with the one-loop result indicate that these structure constants are protected by a non-renormalization theorem. We also show that three point function of U(1) R-currents with classical massive strings is proportional to the R-charge carried by the string solution. This is in accordance with the prediction of the R-symmetry Ward identity.

Elétrons fortemente correlacionados na vizinhança de uma transição de fase quântica

The aim of this work is to derive theWard Identity for the low energy effective theory of a fermionic system in the presence of a hyperbolic Fermi surface coupled with a U(1) gauge field in 2+1 dimensions. These identities are important because they establish requirements for the theory to be gauge invariant. We will see that the identity associated Ward Identity (WI) of the model is not preserved at 1-loop order. This feature signalizes the presence of a quantum anomaly. In other words, a classical symmetry is broken dynamically by quantum fluctuations. Furthermore, we are considering that the system is close to a Quantum Phase Transitions and in vicinity of a Quantum Critical Point the fermionic excitations near the Fermi surface, decay through a Landau damping mechanism. All this ingredients need to be take explicitly to account and this leads us to calculate the vertex corrections as well as self energies effects, which in this way lead to one particle propagators which have a non-trivial frequency dependence

Renormalized new solutions for the massless Thirring model

We present a nonperturbative study of the (1 + 1)-dimensional massless Thirring model by using path integral methods. The regularization ambiguities - coming from the computation of the fermionic determinant - allow to find new solution types for the model. At quantum level the Ward identity for the 1PI 2-point function for the fermionic current separates such solutions in two phases or sectors, the first one has a local gauge symmetry that is implemented at quantum level and the other one without this symmetry. The symmetric phase is a new solution which is unrelated to the previous studies of the model and, in the nonsymmetric phase there are solutions that for some values of the ambiguity parameter are related to well-known solutions of the model. We construct the Schwinger-Dyson equations and the Ward identities. We make a detailed analysis of their UV divergence structure and, after, we perform a nonperturbative regularization and renormalization of the model.

On dynamical gluon mass generation

The effective gluon propagator constructed with the pinch technique is governed by a Schwinger-Dyson equation with special structure and gauge properties, that can be deduced from the correspondence with the background field method. Most importantly the non-perturbative gluon self-energy is transverse order-by-order in the dressed loop expansion, and separately for gluonic and ghost contributions, a property which allows for a meanigfull truncation. A linearized version of the truncated Schwinger-Dyson equation is derived, using a vertex that satisfies the required Ward identity and contains massless poles. The resulting integral equation, subject to a properly regularized constraint, is solved numerically, and the main features of the solutions are briefly discussed.

Direct instantons, topological charge screening, and QCD glueball sum rules

Nonperturbative Wilson coefficients of the operator product expansion (OPE) for the spin-0 glueball correlators are derived and analyzed. A systematic treatment of the direct instanton contributions is given, based on a realistic instanton size distribution and renormalization at the operator scale. In the pseudoscalar channel, topological charge screening is identified as an additional source of (semi-) hard nonperturbative physics. The screening contributions are shown to be vital for consistency with the anomalous axial Ward identity, and previously encountered pathologies (positivity violations and the disappearance of the 0(-+) glueball signal) are traced to their neglect. on the basis of the extended OPE, a comprehensive quantitative analysis of eight Borel-moment sum rules in both spin-0 glueball channels is then performed. The nonperturbative OPE coefficients turn out to be indispensable for consistent sum rules and for their reconciliation with the underlying low-energy theorems. The topological short-distance physics strongly affects the sum rule results and reveals a rather diverse pattern of glueball properties. New predictions for the spin-0 glueball masses and decay constants and an estimate of the scalar glueball width are given, and several implications for glueball structure and experimental glueball searches are discussed.

Topological charge screening and pseudoscalar glueballs

Topological charge screening in the QCD vacuum is found to provide crucial nonperturbative contributions to the short-distance expansion of the pseudoscalar (0-+) glueball correlator. The screening contributions enter the Wilson coefficients and are an indispensable complement to the direct instanton contributions. They restore consistency with the anomalous axial Ward identity and remedy several flaws in the 0-+ glueball sum rules caused by direct instantons in the absence of screening (lack of resonance signals, violation of the positivity bound and of the underlying low-energy theorem). The impact of the finite width of the instanton size distribution and the (gauge-invariant) renormalization of the instanton contributions are also discussed. New predictions for the 0-+ glueball mass and decay constant are presented.

Radiative corrections for the gauged Thirring model in causal perturbation theory

We evaluate the one-loop fermion self-energy for the gauged Thirring model in (2+1) dimensions. with one massive fermion flavor. We do this in the framework of the causal perturbation theory. In contrast to QED3, the corresponding two-point function turns out to be infrared finite on the mass shell. Then, by means of a Ward identity, we derive the on-shell vertex correction and discuss the role played by causality for non-renormalizable theories.

Gluon mass generation in the PT-BFM scheme

In this article we study the general structure and special properties of the Schwinger-Dyson equation for the gluon propagator constructed with the pinch technique, together with the question of how to obtain infrared finite solutions, associated with the generation of an effective gluon mass. Exploiting the known all-order correspondence between the pinch technique and the background field method, we demonstrate that, contrary to the standard formulation, the non-perturbative gluon self-energy is transverse order-by-order in the dressed loop expansion, and separately for gluonic and ghost contributions. We next present a comprehensive review of several subtle issues relevant to the search of infrared finite solutions, paying particular attention to the role of the seagull graph in enforcing transversality, the necessity of introducing massless poles in the three-gluon vertex, and the incorporation of the correct renormalization group properties. In addition, we present a method for regulating the seagull-type contributions based on dimensional regularization; its applicability depends crucially on the asymptotic behavior of the solutions in the deep ultraviolet, and in particular on the anomalous dimension of the dynamically generated gluon mass. A linearized version of the truncated Schwinger-Dyson equation is derived, using a vertex that satisfies the required Ward identity and contains massless poles belonging to different Lorentz structures. The resulting integral equation is then solved numerically, the infrared and ultraviolet properties of the obtained solutions are examined in detail, and the allowed range for the effective gluon mass is determined. Various open questions and possible connections with different approaches in the literature are discussed. © SISSA 2006.

Australian and Thai isolates of Burkholderia pseudomallei are distinct by multilocus sequence typing: Revision of a case of mistaken identity

A recent study using multilocus sequence typing (MLST) of Burkholderia pseudomallei isolates found a sequence type (ST60) to be common to both Thailand and Australia, contradicting earlier studies showing complete distinction between isolates from these regions. The ST60 isolates reportedly from Australia had been obtained for MLST from United Kingdom and U.S. collections. We have located and characterized the original Australian isolates; they were collected in 1983, and they are neither ST60 nor B. pseudomallei isolates. The B. pseudomallei MLST database has been corrected, and there is no ST common to isolates verified as obtained from Australia or from Thailand.

Valuing local built heritage in a global setting : identity & visual perceptions of cultural built heritage in Northern Ireland

‘In these troubled times with the world in search of its bearings and way ward minds using the terms “culture” and “civilization” in an attempt to turn human beings against one another, there is an urgent need to remember how fundamental cultural diversity is to humanity itself’ (UNESCO 2002). The progressive idea of culture can be used in regressive ways by extremists who used it occasionally to pursue the politics of xenophobia and exclusion. The hypothesis that different communities can share the same culture but have different visual perception of their built environment might seems contradictory. It is essential to describe what is meant by the ‘same culture’. The ever evolving changes of definition and re-definition of the word has not yet settled. This paper adopts the descriptive definition of culture while challenging its interpretation. The descriptive definition refers to ‘all the characteristics activities by a people’. While this description is generally accepted, the interpretation of what ‘a people’ means is divisive. It is not clear how Eliot defines ‘a people’. Is the term genetically prescribed or is ‘a people’ place related? And what about the moral and religious orientation? This paper argues that culture is basically place related and the forces that shape a culture of a ‘people’ are deeply embedded in the environmental forces that also shape other aspects of the place making and its identity. The paper addresses the questions of conflicts, value systems, and culture definitions and the inseparable links with architecture aesthetics.

Local built heritage in Northern Ireland is taken as a case study. Unlike many parts of the world, visual perceptions in Northern Ireland is well recognised with iconic as well as formal representations. The population is well aware of the signified as well as the signifiers. The boundaries between iconology and formalism theories are very blurred in the Northern Ireland context. This paper examines how the two communities visually perceive their shared built heritage and the extent of overlapping between the understanding of iconic and formalist visual representations in the built environment. The paper takes the buildings of the successful economic ventures of the shirt industry in the 19th century as a case study. The case study provides an insight of how a signified value of a successful economic regeneration initiative that is deeply imbedded in the social structure and within the urban fabric can overcome divisive visual perception. The paper examines the possibility of building upon the historical success of the shirt industry to promote architectural cultural dialogue in which cultural built heritage in Derry is able to facilitate knowledge creation and social capital in different arenas.

Narrative identity and offender rehabilitation

The rehabilitation of offenders is an evaluative and capability-building process and is concerned with promoting primary goods and managing risk. At the heart of this process is the construction of a more adaptive narrative identity and the acquisition of capabilities to enable offenders to secure important values in their postrelease environments. In this article, the authors examine the idea of narrative identity and its relationship to values and to assessment and treatment.

Nursing handover from ICU to cardiac ward: standardised tools to reduce safety risks

BACKGROUND: Standardising handover processes and content, and using context-specific checklists are proposed as solutions to mitigate risks for preventable errors and patient harm associated with clinical handovers. OBJECTIVES: Adapt existing tools to standardise nursing handover from the intensive care unit (ICU) to the cardiac ward and assess patient safety risks before and after pilot implementation. METHODS: A three-stage, pre-post interrupted time-series design was used. Data were collected using naturalistic observations and audio-recording of 40 handovers and focus groups with 11 nurses. In Stage 1, examination of existing practice using observation of 20 handovers and a focus group interview provided baseline data. In Stage 2, existing tools for high-risk handovers were adapted to create tools specific to ICU-to-ward handovers. The adapted tools were introduced to staff using principles from evidence-based frameworks for practice change. In Stage 3, observation of 20 handovers and a focus group with five nurses were used to verify the design of tools to standardise handover by ICU nurses transferring care of cardiac surgical patients to ward nurses. RESULTS: Stage 1 data revealed variable and unsafe ICU-to-ward handover practices: incomplete ward preparation; failure to check patient identity; handover located away from patients; and information gaps. Analyses informed adaptation of process, content and checklist tools to standardise handover in Stage 2. Compared with baseline data, Stage 3 observations revealed nurses used the tools consistently, ward readiness to receive patients (10% vs 95%), checking patient identity (0% vs 100%), delivery of handover at the bedside (25% vs 100%) and communication of complete information (40% vs 100%) improved. CONCLUSION: Clinician adoption of tools to standardise ICU-to-ward handover of cardiac surgical patients reduced handover variability and patient safety risks. The study outcomes provide context-specific tools to guide handover processes and delivery of verbal content, a safety checklist, and a risk recognition matrix.