Methods for local gravity field approximation

The most widely known modern method for estimating gravity field values from observed data is least-squares collocation. Its advantages are that it can make estimates at arbitrary locations based on irregularly spaced observations, and that it makes use of statistical information about errors in the input data while providing corresponding information about the quality of the output estimates. Disadvantages of collocation include the necessity of inverting square matrices of dimension equal to the number of data values and the need to assume covariance models for the gravity field and the data errors. Fourier methods are an important alternative to collocation; having the advantage of greater computational efficiency, but requiring data estimates to be on a regular grid and not using or providing statistical accuracy information. The GEOFAST algorithm is an implementation of collocation that achieves high computational efficiency by transforming the estimation equations into the frequency domain where an accurate approximation may be made to reduce the workload. The forward and inverse Fast Fourier Transforms (FFTs) are utilized. The accuracy and computational efficiency of the GEOFAST algorithm is demonstrated using two sets of synthetic gravity data: marine gravity for an ocean trench region including wavelengths longer than 200 km; and local land gravity containing wavelengths as short as 5 km. These results are discussed along with issues such as the advantages of first removing reference field models before carrying out the estimation algorithm

CoGeNT, DAMA, and Light Neutralino Dark Matter

Recent observations by the CoGeNT collaboration (as well as long standing observations by DAMA/LIBRA) suggest the presence of a $\sim 5$-10 GeV dark matter particle with a somewhat large elastic scattering cross section with nucleons ($\sigma\sim 10^{-40}$ cm$^2$).Within the context of the minimal supersymmetric standard model (MSSM), neutralinos in this mass range are not able to possess such large cross sections, and would be overproduced in the early universe. Simple extensions of the MSSM, however, can easily accommodate these observations. In particular, the extension of the MSSM by a chiral singlet superfield allows for the possibility that the dark matter is made up of a light singlino that interacts with nucleons largely through the exchange of a fairly light ($\sim$30-70 GeV) singlet-like scalar higgs, \hi. Such a scenario is consistent with all current collider constraints and can generate the signals reported by CoGeNT and DAMA/LIBRA. Furthermore, there is a generic limit of the extended model in which there is a singlet-like pseudoscalar higgs, \ai, with \mai\sim \mhi and in which the $\chi^0\chi^0$ and b\anti b, s\anti s coupling magnitudes of the \hi and \ai are very similar. In this case, the thermal relic abundance is automatically consistent with the measured density of dark matter if \mchi is sufficiently small that \chi^0\chi^0\to b\anti b is forbidden.Comment: 6 pages, published versio

Autocatalytic plume pinch-off

A localized source of buoyancy flux in a non-reactive fluid medium creates a plume. The flux can be provided by either heat, a compositional difference between the fluid comprising the plume and its surroundings, or a combination of both. For autocatalytic plumes produced by the iodate-arsenous acid reaction, however, buoyancy is produced along the entire reacting interface between the plume and its surroundings. Buoyancy production at the moving interface drives fluid motion, which in turn generates flow that advects the reaction front. As a consequence of this interplay between fluid flow and chemical reaction, autocatalytic plumes exhibit a rich dynamics during their ascent through the reactant medium. One of the more interesting dynamical features is the production of an accelerating vortical plume head that in certain cases pinches-off and detaches from the upwelling conduit. After pinch-off, a new plume head forms in the conduit below, and this can lead to multiple generations of plume heads for a single plume initiation. We investigated the pinch-off process using both experimentation and simulation. Experiments were performed using various concentrations of glycerol, in which it was found that repeated pinch-off occurs exclusively in a specific concentration range. Autocatalytic plume simulations revealed that pinch-off is triggered by the appearance of accelerating flow in the plume conduit.Comment: 10 figures. Accepted for publication in Phys Rev E. See also http://www.physics.utoronto.ca/nonlinear/papers_chemwave.htm

Proton Lifetime and Baryon Number Violating Signatures at the LHC in Gauge Extended Models

There exist a number of models in the literature in which the weak interactions are derived from a chiral gauge theory based on a larger group than SU(2)_L x U(1)_Y. Such theories can be constructed so as to be anomaly-free and consistent with precision electroweak measurements, and may be interpreted as a deconstruction of an extra dimension. They also provide interesting insights into the issues of flavor and dynamical electroweak symmetry breaking, and can help to raise the mass of the Higgs boson in supersymmetric theories. In this work we show that these theories can also give rise to baryon and lepton number violating processes, such as nucleon decay and spectacular multijet events at colliders, via the instanton transitions associated with the extended gauge group. For a particular model based on SU(2)_1 x SU(2)_2, we find that the $B+L$ violating scattering cross sections are too small to be observed at the LHC, but that the lower limit on the lifetime of the proton implies an upper bound on the gauge couplings.Comment: 36 page

Structure and Composition of Apple Juice Haze

Haze obtained from commercial apple juice over the 1991 season contained from 11.4 to 29.0% protein (w/w) , trace quantities of both metal cations and polymeric carbohydrate, and gave strong responses to tests for phenolic compounds indicating a protein-phenol haze. SDS-PAGE of the 2-mercaptoethanol reduced , guanidinium hydrochloride dissaggregated haze particles gave a continuous smear indicating a population of molecules ranging from 29K to greater than 205K daltons. Transmission electron microscopy of negatively stained preparations revealed the presence of spherical bodies only partially penetrable by stain and possessin g a suhunit structure. These particles were embedded in a material presumably polymerized in such a way as to form chain-like aggregates. Protein-phenol haze particles consist of two structural components: spherical particles, probably protein , embedded in polymerized phenolics

Four Generations and Higgs Physics

In the light of the LHC, we revisit the implications of a fourth generation of chiral matter. We identify a specific ensemble of particle masses and mixings that are in agreement with all current experimental bounds as well as minimize the contributions to electroweak precision observables. Higgs masses between 115-315 (115-750) GeV are allowed by electroweak precision data at the 68% and 95% CL. Within this parameter space, there are dramatic effects on Higgs phenomenology: production rates are enhanced, weak-boson-fusion channels are suppressed, angular distributions are modified, and Higgs pairs can we observed. We also identify exotic signals, such as Higgs decay to same-sign dileptons. Finally, we estimate the upper bound on the cutoff scale from vacuum stability and triviality.Comment: 11 pages, 7 figures, REVTe