Physical model for the emptying and filling system of the third set of Panama locks

The Panama Canal Authority (ACP) extension plan includes the construction of a third lane with new locks at both sides of the Canal. The design ship is a so-called Post- Panamax 12 000 TEU container carrier. In order to maximize the transit throughput of the new locks, and at the same time, to limit hawser forces under an acceptable maximum threshold, many numerical studies and two physical model studies have been carried out. In a first phase, the filling and emptying (F/E) system of the locks has been preoptimized with numerical models (1D, 2D and 3D models). Then, to complete the design, a study have been carried out on a 1/30 physical scale model at Compagnie Nationale du Rhône Hydraulic Laboratory, Lyon, France, operating as member of the consortium CPP. The F/E system is a “double culverts” sidewall and ports system composed of: a main culvert connected by a central flow divider to two secondary culverts in middle section of the lock chamber; each secondary culvert is equipped with 10 ports which feed the lock on 80% of its length. In order to limit water consumption, each lock includes 3 Water Saving Basins (WSB). The scale model represents two locks chambers, 3 WSB associated with the lower chamber, a fore and a tail bay. The Post-Panamax container ship vessel is also modelled. A special emphasis is put on the hawser forces measurements and in the definition of a threshold value for them as no standard values presently exists for Post-Panamax locks given such operating conditions (use of water saving basins or not, hydraulic heads ranging from 3.5 m to 20 m). The experimental setup and the scenarios of tests are described and an overview of the main results (F/E times, times series of water levels with and without ship in the lock chamber, time series of hydraulic efforts on the ship hull) are given. The results of this physical model are an input for the design-build tender for the construction of the third set of locks, presently in progress

Two Dimensional Quantum Dilaton Gravity and the Positivity of Energy

Using an argument due to Regge and Teitelboim, an expression for the ADM mass of 2d quantum dilaton gravity is obtained. By evaluating this expression we establish that the quantum theories which can be written as a Liouville-like theory, have a lower bound to energy, provided there is no critical boundary. This fact is then reconciled with the observation made earlier that the Hawking radiation does not appear to stop. The physical picture that emerges is that of a black hole in a bath of quantum radiation. We also evaluate the ADM mass for the models with RST boundary conditions and find that negative values are allowed. The Bondi mass of these models goes to zero for large retarded times, but becomes negative at intermediate times in a manner that is consistent with the thunderpop of RST.Comment: 16 pages, phyzzx, COLO-HEP-309. (Confusing points in previous version clarified, discussion of ADM and Bondi masses in RST case added.

Influence of the Measure on Simplicial Quantum Gravity in Four Dimensions

We investigate the influence of the measure in the path integral for Euclidean quantum gravity in four dimensions within the Regge calculus. The action is bounded without additional terms by fixing the average lattice spacing. We set the length scale by a parameter $\beta$ and consider a scale invariant and a uniform measure. In the low $\beta$ region we observe a phase with negative curvature and a homogeneous distribution of the link lengths independent of the measure. The large $\beta$ region is characterized by inhomogeneous link lengths distributions with spikes and positive curvature depending on the measure.Comment: 12pg

The Problem of Time and Quantum Black Holes

We discuss the derivation of the so-called semi-classical equations for both mini-superspace and dilaton gravity. We find that there is no systematic derivation of a semi-classical theory in which quantum mechanics is formulated in a space-time that is a solution of Einstein's equation, with the expectation value of the matter stress tensor on the right-hand side. The issues involved are related to the well-known problems associated with the interpretation of the Wheeler-deWitt equation in quantum gravity, including the problem of time. We explore the de Broglie-Bohm interpretation of quantum mechanics (and field theory) as a way of spontaneously breaking general covariance, and thereby giving meaning to the equations that many authors have been using to analyze black hole evaporation. We comment on the implications for the ``information loss" problem.Comment: 30 pages, COLO-HEP-33

Tidal wetland restoration at Ketenisse polder (Schelde Estuary, Belgium): developments in the first year

Ketenisse polder is a former intertidal brackish marsh (30ha) situated in the mesohaline part of the Schelde Estuary. In the 19th century its central part was embanked as a polder. In the mid 1980’s the area was raised above intertidal level when it was used as a dumping site for the excavated soil from the Liefkenshoek tunnel. In 2002 the area was restored, it was levelled with a weak slope below mean high water level, creating the optimal starting conditions for the development of intertidal mudflats and marshes. Geomorphological changes, sediment characteristics and colonisation by phytobenthos, vegetation, zoobenthos, water birds and breeding birds at the restored site are monitored. The monitoring results of the first year after tidal restoration are presented. Sedimentation as well as erosion between 0 and 30cm was observed in the first year. Local changes in stream current patterns caused erosion on parts of the former mudflats; sheltered depressions filled up relatively fast. Median grain size showed large variation. Organic carbon content of the sediment varied between 0.5 and 15% and was closely related to sediment medium grain size. Chlorophyll a concentrations were negatively correlated with median grain size and tended to increase from the low water line to the shore. They were comparable to nearby intertidal areas and displayed similar seasonal variability with a maximum in spring. The large surface covered wtithVaucheria was indicator of initiated succession towards tidal marsh. Scirpus maritimus and transitional vegetations to Chenopodiaceae-vegetations established with increasing altitude. The Chenopodiaceae-vegetations were relicts of earlier vegetations before the tidal restoration, and will probably disappear. The macrobenthos community was dominated by Oligochaetes, which were present in 73% of all samples and attained an average density of about 40*103 ind. m-2. Other macrobenthos species found were nematods, copepods and Corophium. On the sheltered sampling stations macrobenthic densities were high compared to those on nearby intertidal areas. In the first season, 15 breeding bird species were recorded, the most common species being the Pied Avocet (Recurvirostra avosetta). The most common waterbirds were Common Shelduck (Tadorna tadorna), Greylag Goose (Anser anser), Pied Avocet (Recurvirostra avoset) and Lapwing (Vanellus vanellus), typical species for the mesohaline part of the estuary. The first year’s results suggest that Ketenisse polder has the potential to develop towards a varied and normal functional intertidal area

Degeneracies when T=0 Two Body Matrix Elements are Set Equal to Zero and Regge's 6j Symmetry Relations

The effects of setting all T=0 two body interaction matrix elements equal to a constant (or zero) in shell model calculations (designated as $=0$) are investigated. Despite the apparent severity of such a procedure, one gets fairly reasonable spectra. We find that using $=0$ in single j shell calculations degeneracies appear e.g. the $I={1/2} ^{-}$ and ${13/2}^{-}$ states in $^{43}$Sc are at the same excitation energies; likewise the I=$3_{2}^{+}$,$7_{2}^{+}$,9$^{+}_{1}$ and 10$^{+}_{1}$ states in $^{44}$Ti. The above degeneracies involve the vanishing of certain 6j and 9j symbols. The symmetry relations of Regge are used to explain why these vanishings are not accidental. Thus for these states the actual deviation from degeneracy are good indicators of the effects of the T=0 matrix elements. A further indicator of the effects of the T=0 interaction in an even - even nucleus is to compare the energies of states with odd angular momentum with those that are even

Standard and Generalized Newtonian Gravities as ``Gauge'' Theories of the Extended Galilei Group - I: The Standard Theory

Newton's standard theory of gravitation is reformulated as a {\it gauge} theory of the {\it extended} Galilei Group. The Action principle is obtained by matching the {\it gauge} technique and a suitable limiting procedure from the ADM-De Witt action of general relativity coupled to a relativistic mass-point.Comment: 51 pages , compress, uuencode LaTex fil

A Search for Non-Perturbative Dualities of Local N=2N=2 Yang--Mills Theories from Calabi--Yau Threefolds

The generalisation of the rigid special geometry of the vector multiplet quantum moduli space to the case of supergravity is discussed through the notion of a dynamical Calabi--Yau threefold. Duality symmetries of this manifold are connected with the analogous dualities associated with the dynamical Riemann surface of the rigid theory. N=2 rigid gauge theories are reviewed in a framework ready for comparison with the local case. As a byproduct we give in general the full duality group (quantum monodromy) for an arbitrary rigid $SU(r+1)$ gauge theory, extending previous explicit constructions for the $r=1,2$ cases. In the coupling to gravity, R--symmetry and monodromy groups of the dynamical Riemann surface, whose structure we discuss in detail, are embedded into the symplectic duality group $\Gamma_D$ associated with the moduli space of the dynamical Calabi--Yau threefold.Comment: Latex. Version of previous paper with enlarged and revised appendix 35 pages, plain LaTe

A skeleton approximate solution of the Einstein field equations for multiple black-hole systems

An approximate analytical and non-linear solution of the Einstein field equations is derived for a system of multiple non-rotating black holes. The associated space-time has the same asymptotic structure as the Brill-Lindquist initial data solution for multiple black holes. The system admits an Arnowitt-Deser-Misner (ADM) Hamiltonian that can particularly evolve the Brill-Lindquist solution over finite time intervals. The gravitational field of this model may properly be referred to as a skeleton approximate solution of the Einstein field equations. The approximation is based on a conformally flat truncation, which excludes gravitational radiation, as well as a removal of some additional gravitational field energy. After these two simplifications, only source terms proportional to Dirac delta distributions remain in the constraint equations. The skeleton Hamiltonian is exact in the test-body limit, it leads to the Einsteinian dynamics up to the first post-Newtonian approximation, and in the time-symmetric limit it gives the energy of the Brill-Lindquist solution exactly. The skeleton model for binary systems may be regarded as a kind of analytical counterpart to the numerical treatment of orbiting Misner-Lindquist binary black holes proposed by Gourgoulhon, Grandclement, and Bonazzola, even if they actually treat the corotating case. Along circular orbits, the two-black-hole skeleton solution is quasi-stationary and it fulfills the important property of equality of Komar and ADM masses. Explicit calculations for the determination of the last stable circular orbit of the binary system are performed up to the tenth post-Newtonian order within the skeleton model.Comment: 15 pages, 1 figure, submitted to Phys. Rev. D, 3 references added, minor correction