A three-dimensional scalar field theory model of center vortices and its relation to k-string tensions

In d=3 SU(N) gauge theory, we study a scalar field theory model of center vortices that furnishes an approach to the determination of so-called k-string tensions. This model is constructed from string-like quantum solitons introduced previously, and exploits the well-known relation between string partition functions and scalar field theories in d=3. Center vortices corresponding to magnetic flux J (in units of 2\pi /N) are composites of J elementary J=1 constituent vortices that come in N-1 types, with repulsion between like constituents and attraction between unlike constituents. The scalar field theory involves N scalar fields \phi_i (one of which is eliminated) that can merge, dissociate, and recombine while conserving flux mod N. The properties of these fields are deduced directly from the corresponding gauge-theory quantum solitons. Every vacuum Feynman graph of the theory corresponds to a real-space configuration of center vortices. We study qualitatively the problem of k-string tensions at large N, whose solution is far from obvious in center-vortex language. We construct a simplified dynamical picture of constituent-vortex merging, dissociation, and recombination, which allows in principle for the determination of vortex areal densities and k-string tensions. This picture involves point-like "molecules" (cross-sections of center vortices) made of constituent "atoms" that combine and disassociate dynamically in a d=2 test plane . The vortices evolve in a Euclidean "time" which is the location of the test plane along an axis perpendicular to the plane. A simple approximation to the molecular dynamics is compatible with k-string tensions that are linear in k for k<< N, as naively expected.Comment: 21 pages; RevTeX4; 4 .eps figure

Identification of the nature of reading frame transitions observed in prokaryotic genomes

Our goal was to identify evolutionary conserved frame transitions in protein coding regions and to uncover an underlying functional role of these structural aberrations. We used the ab initio frameshift prediction program, GeneTack, to detect reading frame transitions in 206 991 genes (fs-genes) from 1106 complete prokaryotic genomes. We grouped 102 731 fs-genes into 19 430 clusters based on sequence similarity between protein products (fs-proteins) as well as conservation of predicted position of the frameshift and its direction. We identified 4010 pseudogene clusters and 146 clusters of fs-genes apparently using recoding (local deviation from using standard genetic code) due to possessing specific sequence motifs near frameshift positions. Particularly interesting was finding of a novel type of organization of the dnaX gene, where recoding is required for synthesis of the longer subunit, tau. We selected 20 clusters of predicted recoding candidates and designed a series of genetic constructs with a reporter gene or affinity tag whose expression would require a frameshift event. Expression of the constructs in Escherichia coli demonstrated enrichment of the set of candidates with sequences that trigger genuine programmed ribosomal frameshifting; we have experimentally confirmed four new families of programmed frameshifts

Valence Quark Distribution in A=3 Nuclei

We calculate the quark distribution function for 3He/3H in a relativistic quark model of nuclear structure which adequately reproduces the nucleon approximation, nuclear binding energies, and nuclear sizes for small nuclei. The results show a clear distortion from the quark distribution function for individual nucleons (EMC effect) arising dominantly from a combination of recoil and quark tunneling effects. Antisymmetrization (Pauli) effects are found to be small due to limited spatial overlaps. We compare our predictions with a published parameterization of the nuclear valence quark distributions and find significant agreement.Comment: 18pp., revtex4, 4 fig

Multi--Pressure Polytropes as Models for the Structure and Stability of Molecular Clouds. I. Theory

Molecular clouds are supported by thermal pressure, magnetic pressure, and turbulent pressure. Each of these can be modeled with a polytropic equation of state, so that overall the total pressure is the sum of the individual components. We model the turbulent pressure as being due to a superposition of Alfven waves. The theory of polytropes is generalized to allow for the flow of entropy in response to a perturbation, as expected for the entropy associated with wave pressure. The equation of state of molecular clouds is "soft", so that the properties of the clouds are generally governed by the conditions at the surface. In general, the polytropes are not isentropic, and this permits large density and pressure drops to occur between the center and the edge of the polytropes, as is observed.Comment: Submitted to ApJ with 10 figure

Extragalactic Sources for Ultra High Energy Cosmic Ray Nuclei

In this article we examine the hypothesis that the highest energy cosmic rays are complex nuclei from extragalactic sources. Under reasonable physical assumptions, we show that the nearby metally rich starburst galaxies (M82 and NGC 253) can produce all the events observed above the ankle. This requires diffusion of particles below $10^{20}$ eV in extragalactic magnetic fields $B \approx 15$ nG. Above $10^{19}$ eV, the model predicts the presence of significant fluxes of medium mass and heavy nuclei with small rate of change of composition. Notwithstanding, the most salient feature of the starburst-hypothesis is a slight anisotropy induced by iron debris just before the spectrum-cutoff.Comment: To appear in Phys. Rev. D, reference adde

Time-resolved measurements of product formation in the low-temperature (550-675 K) oxidation of neopentane : a probe to investigate chain-branching mechanism

Product formation, in particular ketohydroperoxide formation and decomposition, were investigated in time-resolved, Cl-atom initiated neopentane oxidation experiments in the temperature range 550-675 K using a photoionization time-of-flight mass spectrometer. Ionization light was provided either by Advanced Light Source tunable synchrotron radiation or similar to 10.2 eV fixed energy radiation from a H-2-discharge lamp. Experiments were performed both at 1-2 atm pressure using a high-pressure reactor and also at similar to 9 Torr pressure employing a low-pressure reactor for comparison. Because of the highly symmetric structure of neopentane, ketohydroperoxide signal can be attributed to a 3-hydroperoxy-2,2-dimethylpropanal isomer, i.e. from a gamma-ketohydroperoxide (gamma-KHP). The photoionization spectra of the gamma-KHP measured at low-and high pressures and varying oxygen concentrations agree well with each other, further supporting they originate from the single isomer. Measurements performed in this work also suggest that the "Korcek" mechanism may play an important role in the decomposition of 3-hydroperoxy-2,2-dimethylpropanal, especially at lower temperatures. However, at higher temperatures where gamma-KHP decomposition to hydroxyl radical and oxy-radical dominates, oxidation of the oxy-radical yields a new important channel leading to acetone, carbon monoxide, and OH radical. Starting from the initial neopentyl + O-2 reaction, this channel releases altogether three OH radicals. A strongly temperature-dependent reaction product is observed at m/z = 100, likely attributable to 2,2-dimethylpropanedial.Peer reviewe

Echoes of the fifth dimension?

In this article we examine the question of whether the highest energy cosmic ray primaries could be ultra relativistic magnetic monopoles. The analysis is performed within the framework of large compact dimensions and TeV scale quantum gravity. Our study indicates that while this hypothesis must be regarded as highly speculative it cannot be ruled out with present data.Comment: Revised version accepted for publication in Physical Review D. The bibliography has been considerably reduced for the journal version due to limited spac

Climate-driven change in the North Atlantic and Arctic Ocean can greatly reduce the circulation of the North Sea

We demonstrate for the first time a direct oceanic link between climate‐driven change in the North Atlantic and Arctic oceans and the circulation of the northwest European shelf‐seas. Downscaled scenarios show a shutdown of the exchange between the Atlantic and the North Sea, and a substantial decrease in the circulation of the North Sea in the second half of the 21st Century. The northern North Sea inflow decreases from 1.2‐1.3Sv (1Sv=106 m3s‐1) to 0.0‐0.6Sv with Atlantic water largely bypassing the North Sea. This is traced to changes in oceanic haline stratification and gyre structure, and to a newly identified circulation‐salinity feedback. The scenario presented here is of a novel potential future state for the North Sea, with wide‐ranging environmental management and societal impacts. Specifically, the sea would become more estuarine and susceptible to anthropogenic influence with an enhanced risk of coastal eutrophication

Tales of the venerable Honolulu tide gauge

Author Posting. © American Meteorological Society, 2006. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 36 (2006): 967-996, doi:10.1175/JPO2876.1.Surface expressions of internal tides constitute a significant component of the total recorded tide. The internal component is strongly modulated by the time-variable density structure, and the resulting perturbation of the recorded tide gives a welcome look at twentieth-century interannual and secular variability. Time series of mean sea level hSL(t) and total recorded M2 vector aTT(t) are extracted from the Honolulu 1905–2000 and Hilo 1947–2000 (Hawaii) tide records. Internal tide parameters are derived from the intertidal continuum surrounding the M2 frequency line and from a Cartesian display of aTT(t), yielding aST = 16.6 and 22.1 cm, aIT = 1.8 and 1.0 cm for surface and internal tides at Honolulu and Hilo, respectively. The proposed model aTT(t) = aST + aIT cosθIT(t) is of a phase-modulated internal tide generated by the surface tide at some remote point and traveling to the tide gauge with velocity modulated by the underlying variable density structure. Mean sea level hSL(t) [a surrogate for the density structure and hence for θIT(t)] is coherent with aIT(t) within the decadal band 0.2–0.5 cycles per year. For both the decadal band and the century drift the recorded M2 amplitude is high when sea level is high, according to δaTT = O(0.1δhSL). The authors attribute the recorded secular increase in the Honolulu M2 amplitude from aTT = 16.1 to 16.9 cm between 1915 and 2000 to a 28° rotation of the internal tide vector in response to ocean warming

Deep seafloor arrivals : an unexplained set of arrivals in long-range ocean acoustic propagation

Author Posting. © Acoustical Society of America, 2009. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 126 (2009): 599-606, doi:10.1121/1.3158826.Receptions, from a ship-suspended source (in the band 50–100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), “deep seafloor arrivals,” that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.The LOAPEX source deployments, the moored DVLA receiver deployments, and some post-cruise data reduction and analysis were funded by the Office of Naval Research under Award Nos. N00014-1403-1-0181, N00014-03-1-0182, and N00014-06-1-0222. Additional post-cruise analysis support was provided to RAS through the Edward W. and Betty J. Scripps Chair for Excellence in Oceanography. The OBS/Hs used in the experiment were provided by Scripps Institution of Oceanography under the U.S. National Ocean Bottom Seismic Instrumentation Pool (SIO-OBSIP—http://www.obsip.org). To cover the costs of the OBS/H deployments funds were paid to SIO-OBSIP from the National Science Foundation and from the Woods Hole Oceanographic Institution Deep Ocean Exploration Institute