No Conformal Anomaly in Unimodular Gravity

The conformal invariance of unimodular gravity survives quantum corrections, even in the presence of conformal matter. Unimodular gravity can actually be understood as a certain truncation of the full Einstein-Hilbert theory, where in the Einstein frame the metric tensor enjoys unit determinant. Our result is compatible with the idea that the corresponding restriction in the functional integral is consistent as well.Comment: 20 pages; misprints correcte

Frame (In)equivalence in Quantum Field Theory and Cosmology

We revisit the question of frame equivalence in Quantum Field Theory in the presence of gravity, a situation of relevance for theories aiming to describe the early Universe dynamics and Inflation in particular. We show that in those cases, the path integral measure must be carefully defined and that the requirement of diffeomorphism invariance forces it to depend non-trivially on the fields. As a consequence, the measure will transform also non-trivially between different frames and it will induce a new finite contribution to the Quantum Effective Action that we name frame discriminant. This new contribution must be taken into account in order to asses the dynamics and physical consequences of a given theory. We apply our result to scalar-tensor theories described in the Einstein and Jordan frame, where we find that the frame discriminant can be thought as inducing a scale-invariant regularization scheme in the Jordan frame.Comment: 33 pages, minor correction

The inter-linkages between rapid growth in livestock production, climate change, and the impacts on water resources, land use, and deforestation

Livestock systems globally are changing rapidly in response to human population growth, urbanization, and growing incomes. This paper discusses the linkages between burgeoning demand for livestock products, growth in livestock production, and the impacts this may have on natural resources, and how these may both affect and be affected by climate change in the coming decades. Water and land scarcity will increasingly have the potential to constrain food production growth, with adverse impacts on food security and human well-being. Climate change will exacerbate many of these trends, with direct effects on agricultural yields, water availability, and production risk. In the transition to a carbon-constrained economy, livestock systems will have a key role to play in mitigating future emissions. At the same time, appropriate pricing of greenhouse gas emissions will modify livestock production costs and patterns. Health and ethical considerations can also be expected to play an increasing role in modifying consumption patterns of livestock products, particularly in more developed countries. Livestock systems are heterogeneous, and a highly differentiated approach needs to be taken to assessing impacts and options, particularly as they affect the resource-poor and those vulnerable to global change. Development of comprehensive frameworks that can be used for assessing impacts and analyzing trade-offs at both local and regional levels is needed for identifying and targeting production practices and policies that are locally appropriate and can contribute to environmental sustainability, poverty alleviation, and economic development.Livestock&Animal Husbandry,Wetlands,Wildlife Resources,Agricultural Knowledge&Information Systems,Rural Development Knowledge&Information Systems

To Positivity and Beyond, where Higgs-Dilaton Inflation has never gone before

We study the consequences of (beyond) positivity of scattering amplitudes in the effective field theory description of the Higgs-Dilaton inflationary model. By requiring the EFT to be compatible with a unitary, causal, local and Lorentz invariant UV completion, we derive constraints on the Wilson coefficients of the first higher order derivative operators. We show that the values allowed by the constraints are consistent with the phenomenological applications of the Higgs-Dilaton model.Comment: 27 pages, 6 figures; matches the published versio

Modelling dairy grazing systems: an integrated approach

This thesis describes a management décision-support system for dairy grazing systems based on simulation and multiple criteria decision-making (MCDM) models.Appropriate selection of holistic management strategies for livestock farming systems requires: 1) understanding of the behaviour of, and interrelations between, the different parts of the system, 2) knowledge of the basic objectives of the decision-maker managing such enterprise, and 3) understanding of the system as a whole in its agro-ecoregional context.Increasing economic and environmental pressures on livestock production systems have created the need to re-evaluate current management practices and to study new alternatives to ensure their sustainability. As a consequence, the demand for décision-support systems based on mathematical models has increased in the past years. Validated simulation models provide cost-effective means to represent the dynamics of the system and its components, while MCDM models allow for appropriate selection of resource allocation strategies depending on the different objectives and management 'styles' of particular individuals. Integration of both mechanisms provides the necessary elements for efficient décision- support at farm or ecoregional level.A décision-support system based on these techniques has been built to represent pastoral dairy production systems. The biological aspects (grass growth; grazing; digestion and metabolism; animal performance, and herd dynamics) are represented by simulation studies under a variety of management regimes. The outputs from the simulation runs (such as pasture utilisation, stocking rates, milk yields, fertilizer use, etc.) are used as data input to the MCDM models, and the latter have been used to select the management strategies which make the most efficient use of the farm's resources (i.e. land, animals, pastures).Examples are given with reference to highland dairy farming in Costa Rica. Nevertheless, the model frameworks are generic and can be adapted to different farming systems or ruminant species. The effect of model formulation and sensitivity, different decision-maker objectives, and/or activity or constraint definitions on management strategy selection are analysed. Future areas of research to expand this work to other livestock farming systems and to integrate other related disciplines into this décision-support framework are also discussed

Conformal and non Conformal Dilaton Gravity

The quantum dynamics of the gravitational field non-minimally coupled to an (also dynamical) scalar field is studied in the {\em broken phase}. For a particular value of the coupling the system is classically conformal, and can actually be understood as the group averaging of Einstein-Hilbert's action under conformal transformations. Conformal invariance implies a simple Ward identity asserting that the trace of the equation of motion for the graviton is the equation of motion of the scalar field. We perform an explicit one-loop computation to show that the DeWitt effective action is not UV divergent {\em on shell} and to find that the Weyl symmetry Ward identity is preserved {\em on shell} at that level. We also discuss the fate of this Ward identity at the two-loop level --under the assumption that the two-loop UV divergent part of the effective action can be retrieved from the Goroff-Sagnotti counterterm-- and show that its preservation in the renormalized theory requires the introduction of counterterms which exhibit a logarithmic dependence on the dilaton field.Comment: LateX, 50 pages. Several points clarified; references added. New section on Weyl invariant renormalisation adde