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

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

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

A global soil spectral calibration library and estimation service

There is growing global interest in the potential for soil reflectance spectroscopy to fill an urgent need for more data on soil properties for improved decision-making on soil security at local to global scales. This is driven by the capability of soil spectroscopy to estimate a wide range of soil properties from a rapid, inexpensive, and highly reproducible measurement using only light. However, several obstacles are preventing wider adoption of soil spectroscopy. The biggest obstacles are the large variation in the soil analytical methods and operating procedures used in different laboratories, poor reproducibility of analyses within and amongst laboratories and a lack of soil physical archives. In addition, adoption is hindered by the expense and complexity of building soil spectral libraries and calibration models. The Global Soil Spectral Calibration Library and Estimation Service is proposed to overcome these obstacles by providing a freely available estimation service based on an open, high quality and diverse spectral calibration library and the extensive soil archives of the Kellogg Soil Survey Laboratory (KSSL) of the Natural Resources Conservation Service of the United States Department of Agriculture (USDA). The initiative is supported by the Global Soil Laboratory Network (GLOSOLAN) of the Global Soil Partnership and the Soil Spectroscopy for Global Good network, which provide additional support through dissemination of standards, capacity development and research. This service is a global public good which stands to benefit soil assessments globally, but especially developing countries where soil data and resources for conventional soil analyses are most limited