Working towards a gauge-invariant description of the Higgs model: from local composite operators to spectral density functions

We analyze different BRST invariant solutions for the introduction of a mass term in Yang-Mills (YM) theories. First, we analyze the non-local composite gauge-invariant field $A^h_{\mu}(x)$, which can be localized by the Stueckelberg-like field $\xi^a(x)$. This enables us to introduce a mass term in the $SU(N)$ YM model, a feature that has been indicated at a non-perturbative level by both analytical and numerical studies. We also consider the unitary Abelian Higgs model and investigate its spectral functions at one-loop order. This analysis allows to disentangle what is physical and what is not at the level of the elementary particle propagators, in conjunction with the Nielsen identities. We highlight the role of the tadpole graphs and the gauge choices to get sensible results. We also introduce an Abelian Curci-Ferrari action coupled to a scalar field to model a massive photon which, like the non-Abelian Curci-Ferarri model, is left invariant by a modified non-nilpotent BRST symmetry. Finally, the spectral properties of a set of local gauge-invariant composite operators are investigated in the $U(1)$ and $SU(2)$ Higgs model quantized in the 't Hooft $R_{\xi}$ gauge. These operators enable us to give a gauge-invariant description of the spectrum of the theory, thereby surpassing certain incommodities when using the standard elementary fields. The corresponding two-point correlation functions are evaluated at one-loop order and their spectral functions are obtained explicitly. It is shown that the spectral functions of the elementary fields suffer from a strong unphysical dependence from the gauge parameter $\xi$, and can even exhibit positivity violating behaviour. In contrast, the BRST invariant local operators exhibit a well defined positive spectral density.Comment: PhD thesis, september 202

Some remarks on the spectral functions of the Abelian Higgs Model

We consider the unitary Abelian Higgs model and investigate its spectral functions at one-loop order. This analysis allows to disentangle what is physical and what is not at the level of the elementary particle propagators, in conjunction with the Nielsen identities. We highlight the role of the tadpole graphs and the gauge choices to get sensible results. We also introduce an Abelian Curci-Ferrari action coupled to a scalar field to model a massive photon which, like the non-Abelian Curci-Ferarri model, is left invariant by a modified non-nilpotent BRST symmetry. We clearly illustrate its non-unitary nature directly from the spectral function viewpoint. This provides a functional analogue of the Ojima observation in the canonical formalism: there are ghost states with nonzero norm in the BRST-invariant states of the Curci-Ferrari model.Comment: 32 pages, 12 figure

Vertical variation of mixing within porous sediment beds below turbulent flows

River ecosystems are influenced by contaminants in the water column, in the pore water and adsorbed to sediment particles. When exchange across the sediment-water interface (hyporheic exchange) is included in modelling, the mixing coefficient is often assumed to be constant with depth below the interface. Novel fibre-optic fluorometers have been developed and combined with a modified EROSIMESS system to quantify the vertical variation in mixing coefficient with depth below the sediment-water interface. The study considered a range of particle diameters and bed shear velocities, with the permeability Péclet number, image between 1,000 and 77,000 and the shear Reynolds number, image between 5 and 600. Different parameterisation of both an interface exchange coefficient and a spatially variable in-sediment mixing coefficient are explored. The variation of in-sediment mixing is described by an exponential function applicable over the full range of parameter combinations tested. The empirical relationship enables estimates of the depth to which concentrations of pollutants will penetrate into the bed sediment, allowing the region where exchange will occur faster than molecular diffusion to be determined

The stakeholder requirements of building systems for coastal low income housing concerning safety and adaptability

Many coastal settlements in humid tropical developing countries face the burdens of risks due to their location as well as due to a rather low quality of housing that does not meet the requirements of sustainability. An important aspect is that the provided building systems for coastal houses in some developing countries (DCs) do not cater for the stakeholder requirement of building safety and adaptability in the coastal area. This paper describes the results on stakeholder requirements and preferences of building systems for determination and adaptation of the performance of low cost housing in HTCCs towards improved sustainability concerning safety and adaptability. Keywords : stakeholder requirements, sustainability and lifespan, building systems, humid tropical coastal cities , safety and adaptabilit

The stakeholder requirements of building systems for coastal low income housing concerning safety and adaptability

Many coastal settlements in humid tropical developing countries face the burdens of risks due to their location as well as due to a rather low quality of housing that does not meet the requirements of sustainability. An important aspect is that the provided building systems for coastal houses in some developing countries (DCs) do not cater for the stakeholder requirement of building safety and adaptability in the coastal area. This paper describes the results on stakeholder requirements and preferences of building systems for determination and adaptation of the performance of low cost housing in HTCCs towards improved sustainability concerning safety and adaptability. Keywords : stakeholder requirements, sustainability and lifespan, building systems, humid tropical coastal cities , safety and adaptabilit

Activities and space use for enabling local economy in coastal low income housing : towards a methodologycal approach

Many low income households are supported by Home Based Enterprises (HBE) for their income generation. However, settlements in coastal areas have physical problems related to the corrosive land and climate condition, as well as the possibilities of natural hazards such as flooding (ADB, 2003: UNHABITAT 2003). The rapid growth of cities especially in developing countries (DCs) contributes to social problems, serious burdens for human health and the environment. In order to improve the quality of human life in the coastal cities, some local governments decided to remove some settlements to the inland area such as problems in some big coastal cities in Indonesia. In many cases, many resettlements of housing failed to meet community’s and user’s requirements. To reduce and avoid sustainability problems, it is necessary to have more insight and understanding of the used of space in coastal low income housing. This paper describes user’s activities and methodological approach used in order to determine user’s requirements in coastal low income housing (LIH). Keywords: coastal settlements, low income housing, home based enterprises (HBE), user’s activities, space design

Low-frequency oscillation suppression in dystonia:Implications for adaptive deep brain stimulation

Background: Low-frequency oscillations (LFO) detected in the internal globus pallidus of dystonia patients have been identified as a physiomarker for adaptive Deep Brain Stimulation (aDBS), since LFO correlate with dystonic symptoms and are rapidly suppressed by continuous DBS (cDBS). However, it is as yet unclear how LFO should be incorporated as feedback for aDBS. Objectives: to test the acute effects of aDBS, using the amplitude of short-lived LFO-bursts to titrate stimulation, to explore the immediate effects of cDBS on LFO-modulation and dystonic symptoms, and to investigate whether a difference in the resting-state LFO is present between DBS-naïve patients and patients with chronic DBS. Methods: seven patients were assessed during either DBS-implantation (n = 2) or battery replacement surgery (n = 5), and pseudorandomized in three conditions: no stimulation, cDBS, and aDBS. Additionally, resting-state LFP-recordings from patients undergoing battery replacement were compared to those obtained during DBS-implantation; LFP-recordings from a previous cohort of six dystonia patients undergoing DBS-implantation were incorporated into this analysis (total n = 8 newly implanted patients). Results: we corroborated that a mild LFO-suppression rapidly occurs during cDBS. However, no acute changes in clinical symptoms were observed after cDBS or aDBS. Remarkably, we observed that resting-state LFO were significantly lower in patients who had been effectively treated with chronic cDBS compared to those of newly implanted patients, even when stimulation was suspended. Conclusions: our results indicate that LFO-suppression in dystonia, similar to symptom response to cDBS, might be gradual, and remain after stimulation is suspended. Therefore, tracking gradual changes in LFO may be required for aDBS implementation

Clinical Pearls - how my patients taught me:The fainting lark symptom

BACKGROUND: Compulsive movements, complex tics and stereotypies are frequent, especially among patients with autism or psychomotor retardation. These movements can be difficult to characterize and can mimic other conditions like epileptic seizures or paroxysmal dystonia, particularly when abnormal breathing and cerebral hypoxia are induced. CASE PRESENTATION: We describe an 18-year-old patient with Asperger syndrome who presented with attacks of tonic posturing of the trunk and neck. The attacks consisted of self-induced stereotypic stretching of the neck combined with a compulsive Valsalva-like maneuver. This induced cerebral hypoperfusion and subsequently dysautonomia and some involuntary movements of the arms. CONCLUSION: This patient suffered from a complex tic with compulsive respiratory stereotypies. His symptoms contain aspects of a phenomenon described in early literature as 'the fainting lark'