A Quantum Cosmological Model With Static and Dynamic Wormholes

Quantization is performed of a Friedmann-Robertson-Walker universe filled with a conformally invariant scalar field and a perfect fluid with equation of state $p=\alpha \rho$. A well-known discrete set of static quantum wormholes is shown to exist for radiation ($\alpha =1/3$), and a novel continuous set is found for cosmic strings ($\alpha = -1/3$), the latter states having throat radii of any size. In both cases wave-packet solutions to the Wheeler-DeWitt equation are obtained with all the properties of evolving quantum wormholes. In the case of a radiation fluid, a detailed analysis of the quantum dynamics is made in the context of the Bohm-de Broglie interpretation. It is shown that a repulsive quantum force inversely proportional to the cube of the scale factor prevents singularities in the quantum domain. For the states considered, there are no particle horizons either.Comment: LaTex file, 13 pages. To appear in General Relativity and Gravitatio

Effect of Water Content on the Thermal Inactivation Kinetics of Horseradish Peroxidase Freeze-Dried from Alkaline pH

The thermal inactivation of horseradish peroxidase freeze-dried from solutions of different pH (8, 10 and 11.5, measured at 25 C) and equilibrated to different water contents was studied in the temperature range from 110 to 150 C. The water contents studied (0.0, 1.4, 16.2 and 25.6 g water per 100 g of dry enzyme) corresponded to water activities of 0.0, 0.11, 0.76 and 0.88 at 4 C. The kinetics were well described by a double exponential model. The enzyme was generally more stable the lower the pH of the original solution, and for all pH values, the maximum stability was obtained at 1.4 g water/100 g dry enzyme. Values of z were generally independent of water content and of the pH of the original solution, and in the range of 15–25 °C, usually found in neutral conditions, with the exception of the enzyme freeze dried from pH 11.5 and equilibrated with phosphorus pentoxide, where a z-value of the stable fraction close to 10 C was found

Full-duplex massive MIMO with physical layer network coding for the two-way relay channel

The role of interference in wireless networks has recently been profoundly re-thought with the emergence of new techniques for combating it and exploit it to maximize the use efficiency of the physical resources. This paper presents a two-way relay channel using a lattice-based physical layer network coding scheme, a massive MIMO array, and in-band full-duplex, taking into account the residual self-interference that results after applying recently developed cancellation techniques for the loopback interference. The proposed scheme is able to ultimately exchange information across the TWRC in only one time slot, whereas four time slots would be needed in a conventional TWRC. The system's performance is shown to be mostly dependent on the number of antennas at the relay, and also dependent on the channel state information of all the channel matrices, including the one describing the loopback interference at the relay. For base-stations and relays with a few hundred antennas, the proposed scheme is feasible for wireless systems.info:eu-repo/semantics/acceptedVersio

Dynamical Vacuum in Quantum Cosmology

By regarding the vacuum as a perfect fluid with equation of state p=-rho, de Sitter's cosmological model is quantized. Our treatment differs from previous ones in that it endows the vacuum with dynamical degrees of freedom. Instead of being postulated from the start, the cosmological constant arises from the degrees of freedom of the vacuum regarded as a dynamical entity, and a time variable can be naturally introduced. Taking the scale factor as the sole degree of freedom of the gravitational field, stationary and wave-packet solutions to the Wheeler-DeWitt equation are found. It turns out that states of the Universe with a definite value of the cosmological constant do not exist. For the wave packets investigated, quantum effects are noticeable only for small values of the scale factor, a classical regime being attained at asymptotically large times.Comment: Latex, 19 pages, to appear in Gen. Rel. Gra

Rotating Relativistic Thin Disks

Two families of models of rotating relativistic disks based on Taub-NUT and Kerr metrics are constructed using the well-known "displace, cut and reflect" method. We find that for disks built from a generic stationary axially symmetric metric the "sound velocity", $(pressure/density)^{1/2}$, is equal to the geometric mean of the prograde and retrograde geodesic circular velocities of test particles moving on the disk. We also found that for generic disks we can have zones with heat flow. For the two families of models studied the boundaries that separate the zones with and without heat flow are not stable against radial perturbations (ring formation).Comment: 18 eps figures, to be published PR

Gravitational collapse to toroidal, cylindrical and planar black holes

Gravitational collapse of non-spherical symmetric matter leads inevitably to non-static external spacetimes. It is shown here that gravitational collapse of matter with toroidal topology in a toroidal anti-de Sitter background proceeds to form a toroidal black hole. According to the analytical model presented, the collapsing matter absorbs energy in the form of radiation (be it scalar, neutrinos, electromagnetic, or gravitational) from the exterior spacetime. Upon decompactification of one or two coordinates of the torus one gets collapsing solutions of cylindrical or planar matter onto black strings or black membranes, respectively. The results have implications on the hoop conjecture.Comment: 6 pages, Revtex, modifications in the title and in the interpretation of some results, to appear in Physical Review

Quantum cosmological perfect fluid models

Perfect fluid Friedmann-Robertson-Walker quantum cosmological models for an arbitrary barotropic equation of state $p = \alpha\rho$ are constructed using Schutz's variational formalism. In this approach the notion of time can be recovered. By superposition of stationary states, finite-norm wave-packet solutions to the Wheeler-DeWitt equation are found. The behaviour of the scale factor is studied by applying the many-worlds and the ontological interpretations of quantum mechanics. Singularity-free models are obtained for $\alpha \alpha > - 1$.Comment: Latex file, 12 pages. New paragraphs in the Introduction and Conclusion, and other minor corrections in the text and in some formulas. Accepted for publication in General Relativity and Gravitatio

Fatores condicionantes a eficiência técnica e econômica da cajucultura nordestina.

Com base em dados levantados pelo CNPCa/EMBRAPA, relativos a safra 1988/89, testou-se a hipotese de que a baixa eficiencia tecnica e economica da cajucultura nordestina esta condicionada a fatores economicos, sociais e agronomicos. No Estado do Ceara, constatou-se que, dentro as variaveis com maior influencia positiva sobre a eficiencia tecnica e economica, destacaram-se o valor da terra ou qualidade dos solos, mao-de-obra empregada, educacao e montante de credito de custeio. No piaui, as variaveis da maior importancia na explicacao da eficiencia tecnica e economica foram idade do plantio, numero de plantas por hectare, assistencia tecnica e mao-de-obra empregada.bitstream/item/33715/1/Bp-003.pd

Non-minimal coupling for the gravitational and electromagnetic fields: A general system of equations

We establish a new self-consistent system of equations for the gravitational and electromagnetic fields. The procedure is based on a non-minimal non-linear extension of the standard Einstein-Hilbert-Maxwell action. General properties of a three-parameter family of non-minimal linear models are discussed. In addition, we show explicitly, that a static spherically symmetric charged object can be described by a non-minimal model, second order in the derivatives of the metric, when the susceptibility tensor is proportional to the double-dual Riemann tensorComment: 15 page

Displacements of Slopes Under Earthquake Loading

The displacements and rates of displacement of slopes post-rupture are influenced by the dynamic response of soils. Pre-existing shear surfaces at or close to residual strength are frequently present in slopes of clay and weak mudstone, due to previous slope movement or tectonic disturbance. Knowledge of the strength of such surfaces under rapid loading is necessary of stability during and after an earthquake is to be examined. To obtain such data, high speed displacement controlled ring shear tests have been performed, on samples after being pre-sheared to residual conditions. With the results from those tests, suitable constitutive laws were derived for the soils and numerical analysis were made of an old landslide submitted to dynamic earthquake loading. Analysis were also performed for first landslides, on plastic clays, in order to calculate the maximum velocity, displacement and duration of sliding. The calculation is based on the assumption that the whole moving mass is displaced as a single rigid body with resistance mobilised along the sliding surface. Newmark\u27s sJjding block was used, sliding on a nonlinear surface involving a resistance dependent on factors such as displacement and rate of slip