9 research outputs found
A new bigravity model with exclusively positive branes
We propose a new ``bigravity'' model with two positive tension AdS_4 branes
in AdS_5 bulk and no negative tension branes. The bounce of the ``warp'' factor
mimics the effect of a negative brane and thus gives rise to an anomalously
light graviton KK mode. This configuration satisfies the weak energy condition
and has no ghost state. In addition, the extra polarization states of the
massive graviton practically decouple and thus it does not contradict to
Einsteinian gravity. However, the model has certain phenomenological
difficulties associated with the presence of a negative cosmological constant
on the branes.Comment: 17 pages, 1 axodraw figure, comments added in the introduction,
references added, minor typos correcte
A Three three-brane Universe:New Phenomenology for the New Millennium?
We consider an extension of the Randall-Sundrum model with three parallel
3-branes in a 5-dimensional spacetime. This new construction, apart from
providing a solution to the Planck hierarchy problem, has the advantage that
the SM fields are confined on a positive tension brane. The study of the
phenomenology of this model reveals an anomalous first KK state which is
generally much lighter than the remaining tower and also much more strongly
coupled to matter. Bounds on the parameter space of the model can be placed by
comparison of specific processes with the SM background as well as by the
latest Cavendish experiments. The model suggests a further exotic possibility
if one drops the requirement of solving the hierarchy problem. In this case
gravity may result from the exchange of the ordinary graviton plus an
ultralight KK state and modifications of gravity may occur at both small and
extremely large scales.Comment: 17 pages, 5 Postscript figures, uses axodraw.sty, corrected some
typo
Radion in Multibrane World
The radion dynamics related to the presence of moving branes with both
positive or negative tensions is studied in the linearized approximation. The
radion effective Lagrangian is computed for a compact system with three branes
and in particular we examine the decompactification limit when one brane is
sent to infinity. In the non-compact case we calculate the coupling of the
gravitational modes (graviton, dilaton and radion) to matter on the branes. The
character of gravity on the two branes for all possible combinations of brane
tensions is also discussed. It turns out that one can have a normalizable
dilaton mode even in the non-compact case. Finally, we speculate on the role of
moving branes as a possible source of radion emission.Comment: 24 pages, 4 figures, comments added, version published in Nucl. Phys.
Multi-Localization in Multi-Brane Worlds
We study bulk fields in various multi-brane models with localized gravity. In
the case of spin 0, 1/2 and 3/2 fields, the non-trivial background geometry
itself can induce (multi-) localization of the zero modes along the extra
dimension. The addition of appropriate mass terms controls the strength or/and
the position of this localization and can induce (multi-) localization of spin
1 fields as well. We show that multi-brane models may also give rise to
anomalously light KK modes which are also localized. The possibility of
multi-localization in the context of supersymmetric brane world models in AdS_5
spacetime is also discussed.Comment: 34 pages, 5 figure
Marine Strategy Framework Directive - Descriptor 2, Non-Indigenous Species, Delivering solid recommendations for setting threshold values for non-indigenous species pressure on European seas
Marine Non-Indigenous Species (NIS) are animals and plants introduced accidently or deliberately into the European seas, originating from other seas of the globe. About 800 marine non-indigenous species (NIS) currently occur in the European Union national marine waters, several of which have negative impacts on marine ecosystem services and biodiversity. Under the Marine Strategy Framework Directive (MSFD) Descriptor 2 (D2), EU Member States (MSs) need to consider NIS in their marine management strategies. The Descriptor D2 includes one primary criterion (D2C1: new NIS introductions), and two secondary criteria (D2C2 and D2C3). The D2 implementation is characterized by a number of issues and uncertainties which can be applicable to the Descriptor level (e.g. geographical unit of assessment, assessment period, phytoplanktonic, parasitic, oligohaline NIS, etc.), to the primary criterion D2C1 level (e.g. threshold values, cryptogenic, questionable species, etc), and to the secondary criteria D2C2 and D2C3. The current report tackles these issues and provides practical recommendations aiming at a smoother and more efficient implementation of D2 and its criteria at EU level. They constitute a solid operational output which can result in more comparable D2 assessments among MSs and MSFD regions/subregions. When it comes to the policy-side, the current report calls for a number of different categories of NIS to be reported in D2 assessments, pointing the need for the species to be labelled/categorised appropriately in the MSFD reporting by the MSs. These suggestions are proposed to be communicated to the MSFD Working Group of Good Environmental Status (GES) and subsequently to the Marine Strategy Coordination Group (MSCG) of MSFD. Moreover, they can serve as an input for revising the Art. 8 Guidelines
Venous Thromboembolism Risk and Prophylaxis in the Acute Care Hospital Setting (ENDORSE Survey) Findings in Surgical Patients
Objective: To evaluate venous thromboembolism (VTE) risk in patients who underwent a major operation, including the use of, and factors influencing, American College of Chest Physicians-recommended types of VTE prophylaxis