Integrated Analysis of Pressure Transient Tests in the Gulf of Mexico

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Small entries of neutrino mass matrices

We consider phenomenologically allowed structures of the neutrino mass matrix in the case of three light neutrino species. Constraints from the solar, atmospheric and reactor neutrino experiments as well as those from the neutrinoless double beta decay are taken into account. Both hierarchical and quasi-degenerate neutrino mass cases are studied. Assuming maximal $\nu_\mu-\nu_\tau$ mixing we derive simple approximate expressions giving the values of the neutrino masses and remaining lepton mixing angles in terms of the entries of the neutrino mass matrix. Special attention is paid to the small entries which are usually not specified in discussions of the neutrino mass matrix textures. We specifically discuss the stability of neutrino masses and lepton mixing angles with respect to the choice and variations of these small entries.Comment: LaTeX, 12 pages, no figures. A few minor typos correcte

Deconstructing the Antlia cluster core

The present literature does not give a satisfactory answer to the question about the nature of the "Antlia galaxy cluster". The radial velocities of galaxies found in the region around the giant ellipticals NGC 3258/3268 range from about 1000 km/s to 4000 km/s. We characterise this region and its possible kinematical and population substructure. We have obtained VLT--VIMOS multi-object spectra of the galaxy population in the inner part of the Antlia cluster and measure radial velocities for 45 potential members. We supplement our galaxy sample with literature data, ending up with 105 galaxy velocities. We find a large radial velocity dispersion for the entire sample as reported in previous papers. However, we find three groups at about 1900 km/s, 2800 km/s, and 3700 km/s, which we interpret as differences in the recession velocities rather than peculiar velocities. The high radial velocity dispersion of galaxies in the Antlia region reflects a considerable extension along the line of sight.Comment: 11 pages, 7 figures, accepted in A&

High Energy Cosmic Tau Neutrinos

I discuss the possibility of production of high energy cosmic tau neutrinos ($E \geq 10^{6}$ GeV) in an astrophysical site and study some of the effects of neutrino mixing on their subsequent propagation. I also discuss the prospects for observations of these high energy cosmic tau neutrinos through double shower events in new km$^{2}$ surface area under water/ice neutrino telescopes.Comment: 3 pages, Latex (uses espcrc2), 1 figure included with epsf, talk given at 6th International Workshop on Topics in Astroparticle and Underground Physics (TAUP 99), 6-10 September, Paris, France [to appear in its proceedings in Nucl. Phys. B (Proc. Suppl.) edited by M. Froissart, J. Dumarchez and D. Vignaud

The merger remnant NGC 3610 and its globular cluster system: a large-scale study

We present a photometric study of the prototype merger remnant NGC 3610 and its globular cluster (GC) system, based on new GEMINI/GMOS and ACS/HST archival images. Thanks to the large FOV of our GMOS data, larger than previous studies, we are able to detect a `classical' bimodal GC colour distribution, corresponding to metal-poor and metal-rich GCs, at intermediate radii and a small subsample of likely young clusters of intermediate colours, mainly located in the outskirts. The extent of the whole GC system is settled as about 40 kpc. The GC population is quite poor, about 500 +/- 110 members, that corresponds to a low total specific frequency S_N ~ 0.8. The effective radii of a cluster sample are determined, including those of two spectroscopically confirmed young and metal-rich clusters, that are in the limit between GC and UCD sizes and brightness. The large-scale galaxy surface-brightness profile can be decomposed as an inner embedded disc and an outer spheroid, determining for both larger extents than earlier research (10 kpc and 30 kpc, respectively). We detect boxy isophotes, expected in merger remnants, and show a wealth of fine-structure in the surface-brightness distribution with unprecedented detail, coincident with the outer spheroid. The lack of symmetry in the galaxy colour map adds a new piece of evidence to the recent merger scenario of NGC 3610.Comment: 14 pages, 16 figures. Accepted for publication in MNRA

FIML estimation of an endogenous switching model for count data

We develop FIML code for estimating a Poisson Count data model with lognormal unobserved heterogeneity and an endogenous dummy variable as proposed by Terza (1998). Gauss-Hermite quadrature is used for calculating the log-likelihood and a -ml d0- method is employed. We present an example and discuss the problems found during the development of the code.

A model for the ESR-STM phenomenon

We propose a model to account for the observed ESR-like signal at the Larmor frequency in the current noise STM experiments identifying spin centers on various substrates. The theoretical understanding of this phenomenon, which allows for single spin detection on surfaces at room temperature, is not settled for the experimentally relevant case that the tip and substrate are not spin polarized. Our model is based on a direct tip-substrate tunneling in parallel with a current flowing via the spin states. We find a sharp signal at the Larmor frequency even at high temperatures, in good agreement with experimental data. We also evaluate the noise in presence of an ac field near resonance and predict splitting of the signal by the Rabi frequency.Comment: 5 pages, 3 figure

Relation Between Local Temperature Gradients and the Direction of Heat Flow in Quantum Driven Systems

We introduce thermometers to define the local temperature of an electronic system driven out-of-equilibrium by local ac fields. We discuss the behavior of the local temperature along the sample, showing that it exhibits spatial fluctuations following an oscillatory pattern. We show explicitly that the local temperature is the correct indicator for heat flow.Comment: 3 pages, 2 figure

Reducing the Number of Annotations in a Verification-oriented Imperative Language

Automated software verification is a very active field of research which has made enormous progress both in theoretical and practical aspects. Recently, an important amount of research effort has been put into applying these techniques on top of mainstream programming languages. These languages typically provide powerful features such as reflection, aliasing and polymorphism which are handy for practitioners but, in contrast, make verification a real challenge. In this work we present Pest, a simple experimental, while-style, multiprocedural, imperative programming language which was conceived with verifiability as one of its main goals. This language forces developers to concurrently think about both the statements needed to implement an algorithm and the assertions required to prove its correctness. In order to aid programmers, we propose several techniques to reduce the number and complexity of annotations required to successfully verify their programs. In particular, we show that high-level iteration constructs may alleviate the need for providing complex loop annotations.Comment: 15 pages, 8 figure

Experimental Signatures of Split Fermions in Extra Dimensions

The smallness and hierarchy of the fermion parameters could be explained in theories with extra dimensions where doublets and singlets are localized at slightly separated points. Scattering cross sections for collisions of such fermions vanish exponentially at energies high enough to probe the separation distance. This is because the separation puts a lower bound on the attainable impact parameter in the collision. The NLC, and in particular the combination of the e^+e^- and e^-e^- modes, can probe this scenario, even if the inverse fermion separation is of order tens of TeVs.Comment: 9 pages, latex, 2 figures. Invited talk presented at the 3rd International Workshop on Electron-Electron Interactions at TeV Energies (e-e-99), December, 1999, Santa Cruz, Californi