Showing papers by "University of California, Santa Barbara published in 1981"
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TL;DR: In the early 1990s, the NSF's Institute for Theoretical Physics in Santa Barbara devoted a 6-month program and an intensive 1-week workshop to the subject as discussed by the authors.
Abstract: In the past few years one of the most exciting areas of research in physics has been the interdisciplinary field of cosmology and particle physics. The NSF's Institute for Theoretical Physics in Santa Barbara devoted a 6-month program and an intensive 1-week workshop to the subject. A brief review is given of both the workshop and this field which is attracting attention, in part, because the early Universe seems to be the only laboratory in which to study grand unification.
3,436 citations
TL;DR: In this article, the authors construct an explicit realistic SU(5) model in which softly broken supersymmetry is used to protect the Higgs doublets from quadratic mass renormalization.
1,916 citations
TL;DR: For systems with negligible self-gravity, the bound follows from application of the second law of thermodynamics to a gedanken experiment involving a black hole as discussed by the authors, and it is shown that black holes have the maximum entropy for given mass and size which is allowed by quantum theory and general relativity.
Abstract: We present evidence for the existence of a universal upper bound of magnitude $\frac{2\ensuremath{\pi}R}{\ensuremath{\hbar}c}$ to the entropy-to-energy ratio $\frac{S}{E}$ of an arbitrary system of effective radius $R$. For systems with negligible self-gravity, the bound follows from application of the second law of thermodynamics to a gedanken experiment involving a black hole. Direct statistical arguments are also discussed. A microcanonical approach of Gibbons illustrates for simple systems (gravitating and not) the reason behind the bound, and the connection of $R$ with the longest dimension of the system. A more general approach establishes the bound for a relativistic field system contained in a cavity of arbitrary shape, or in a closed universe. Black holes also comply with the bound; in fact they actually attain it. Thus, as long suspected, black holes have the maximum entropy for given mass and size which is allowed by quantum theory and general relativity.
1,079 citations
TL;DR: In this paper, a formalism for carrying out Monte Carlo calculations of field theories with both boson and fermion degrees of freedom is presented, and the structure of the effective action for a wide class of theories is studied.
Abstract: We present a formalism for carrying out Monte Carlo calculations of field theories with both boson and fermion degrees of freedom. The basic approach is to integrate out the fermion degrees of freedom and obtain an effective action for the boson fields to which standard Monte Carlo techniques can be applied. We study the structure of the effective action for a wide class of theories. We develop a procedure for making rapid calculations of the variation in the effective action due to local changes in the boson fields, which is essential for practical numerical calculations.
833 citations
TL;DR: In this article, the scale of unification is moved significantly higher, into the range of the Planck mass, which may be suggestive of an eventual unification including gravity, and markedly reduces the predicted rate of nucleon decay.
Abstract: Unified theories which are supersymmetric down to energies \ensuremath{\sim}${10}^{3}$-${10}^{5}$ GeV have been proposed as possible solutions to the gauge-hierarchy problem. The additional particles then required have significant effects on renormalization of coupling constants. The previous successful calculation of the weak mixing angle is only slightly changed, but the scale of unification is moved significantly higher, into the range of the Planck mass. This may be suggestive of an eventual unification including gravity, and markedly reduces the predicted rate of nucleon decay.
785 citations
TL;DR: In this article, a method is proposed to calculate quantum numbers on solitons in quantum field theory, and the method is checked on previously known examples and, in a special model, by other methods.
Abstract: A method is proposed to calculate quantum numbers on solitons in quantum field theory. The method is checked on previously known examples and, in a special model, by other methods. It is found, for example, that the fermion number on kinks in one dimension or on magnetic monopoles in three dimensions is, in general, a transcendental function of the coupling constant of the theories.
619 citations
TL;DR: How advances in cognitive and educati(~nal psychology may be applied to problems in teaching nonprogrammers how to use computers is reviewed.
Abstract: This paper examines the current state of knowledge concerning how to increase the novice's understanding of computers and computer programming. In particular, it reviews how advances in cognitive and educati(~nal psychology may be applied to problems in teaching nonprogrammers how to use computers. Two major instructional techniques are reviewed: providing a concrete model of the computer and encouraging the learners to actively put technical information into their own words.
487 citations
TL;DR: In this article, it was shown that the associated Goldstone bosons live effectively in 1 + 1 dimensions and therefore, by the Mermin-Wagner-Coleman theorem, destabilize the flux tube.
481 citations
TL;DR: In this paper, an alternative estimate of 0.41 × 10 15 gC yr -1 is derived from measurements of the fluvial loss of organic carbon per unit area of land in various ecosystem types.
Abstract: Total transport of organic carbon to the world's oceans in dissolved and particulate form in rivers is estimated as 0.37 × 10 15 gC yr -1 by an inventory and extrapolation of data on loss of carbon per unit volume of river discharge from twelve intermediate and large rivers. An alternative estimate of 0.41 × 10 15 gC yr -1 is derived from measurements of the fluvial loss of organic carbon per unit area of land in various ecosystem types. Rates of loss range from 1 gC m -2 yr -1 in grassland systems to 10 gC m -2 yr -1 in some forests. Organic carbon transport in rivers is a small flux in the global carbon cycle, but our present understanding is limited by inadequate sampling and few data from major world rivers. DOI: 10.1111/j.2153-3490.1981.tb01742.x
425 citations
TL;DR: For example, the authors showed that strong correlations between various local and global estimates of Phanerozoic marine diversity for taxa below the ordinal level indicate a single pattern of change underlying all data on fossil density.
Abstract: Strong correlations between various local and global estimates of Phanerozoic marine diversity for taxa below the ordinal level indicate a single pattern of change underlying all data on fossil density. Geological time alone seems insufficient to explain all of the significant covariation among the data sets, and it is proposed that the common pattern in diversity reflects the signal from a real evolutionary phenomenon strong enough to overcome the biases inherent in the fossil record.
382 citations
TL;DR: All the vestimentiferan worms and several of the molluscs were found to contain enzyme activities associated with sulphide oxidation, the Calvin-Benson cycle and nitrate reduction, suggesting that the putative animal-bacterial symbiosis first described in Riftia pachyptila may be of widespread occurrence in species living in environments offering simultaneous access to sulphide and oxygen.
Abstract: The role of sulphide oxidation-driven production of reduced carbon in the nutrition of animals adapted to life in sulphide-rich habitats such as the deep-sea hydrothermal vents and intertidal mudflats has been a topic of recent interest1–4. Chemoautotrophic sulphide-oxidizing bacteria have been isolated from samples of sulphide-rich vent water5–8, and it has been suggested that these could provide a food source for filter-feeding animals that live at the vents. The recent discovery of prokaryotic cells9 and activities of sulphide-oxidizing enzymes (which generate reducing power and ATP) and Calvin—Benson cycle enzymes10 within the trophosome tissue of the large vestimentiferan tubeworm of the vents, Riftia pachyptila Jones (Phylum Pogonophora)11 suggests that sulphide-oxidizing chemoauto-trophic bacteria exist in a symbiotic relationship with at least this vent species. This discovery led us to measure enzyme activities associated with sulphide oxidation, the Calvin-Benson cycle and nitrate reduction in a variety of other vestimentiferan tube-worms and bivalve molluscs which occur in sulphide-rich habitats. All the vestimentiferan worms and several of the molluscs were found to contain these enzymatic activities, suggesting that the putative animal-bacterial symbiosis first described in Riftia pachyptila may be of widespread occurrence in species living in environments offering simultaneous access to sulphide and oxygen.
TL;DR: In this article, the free energy of a single quark is calculated in the Euclidean theory in terms of a "Wilson line" running the length of the system along the (periodic) time axis.
Abstract: Quark confinement in a finite-temperature $\mathrm{SU}(N)$ gauge theory is formulated as the realization of a global ${Z}_{N}$ symmetry. Spontaneous breakdown corresponds to a transition to a nonconfining, plasma phase. The free energy of a single quark is an order parameter which probes the phase structure, and it may be calculated in the Euclidean theory in terms of a "Wilson line" running the length of the system along the (periodic) time axis. We present results of a Monte Carlo calculation in the SU(2) lattice theory which confirm the transition at a critical temperature computed in terms of the zero-temperature string tension; data for the quark-antiquark potential are presented as well. We discuss the implications of the finite-temperature transition for efforts to calculate zero-temperature quantities on finite-size lattices. Finally, we note that restoration of ${Z}_{N}$ symmetry as the temperature is lowered may be understood as a condensation of instantons and other topological objects.
TL;DR: Results of a paired comparisons experiment indicate that decision variable variance is nearly constant over the range of contrasts used in these experiments and the implications for several models of contrast detection and discrimination are considered.
TL;DR: In this paper, a block adaptive filtering procedure is proposed in which the filter coefficients are adjusted once per each output block in accordance with a generalized least mean-square (LMS) algorithm.
Abstract: Block digital filtering involves the calculation of a block or finite set of filter outputs from a block of input values This paper presents a block adaptive filtering procedure in which the filter coefficients are adjusted once per each output block in accordance with a generalized least mean-square (LMS) algorithm Analyses of convergence properties and computational complexity show that the block adaptive filter permits fast implementations while maintaining performance equivalent to that of the widely used LMS adaptive filter
TL;DR: A unidirectional flux of tubulin from one end of the microtubule to the other, or ‘treadmilling’, can occur, which could be fundamentally linked to the functions of microtubules, as, for example, in the translocation of chromosomes during mitosis.
Abstract: Microtubule polymerization in vitro is the summation of different reactions occurring at each end of the polymer. In steady-state conditions in vitro, net tubulin addition on the microtubule occurs at one end of the polymer, and net tubulin loss occurs at the opposite end. Thus, a unidirectional flux of tubulin from one end of the microtubule to the other, or "treadmilling', can occur. The opposite end assembly--disassembly behaviour of microtubules, if it occurs within cells, could be fundamentally linked to the functions of microtubules, as, for example, in the translocation of chromosomes during mitosis.
TL;DR: In this paper, the authors studied the modification of optical properties of two metal spheres brought about by their electromagnetic interactions, and computed the excitation spectrum of the two sphere system and studied the shape and the magnitude of the local fields.
TL;DR: In this paper, the authors investigated the power-law creep behavior of polycrystalline magnesium over the temperature range from 473 to 820 K. The results show the occurrence of three different mechanisms, with the creep process depending on the testing temperature and stress level.
TL;DR: In this article, the common basis for this fortunate convergence between condensed matter and relativistic field theories is examined, and it is shown that fractional fermion charge can lead to unexpected but experimentally verified predictions for one-dimensional electron-phonon systems like polyacetylene.
TL;DR: A block adaptive filtering procedure in which the filter coefficients are adjusted once per each output block in accordance with a generalized least mean-square (LMS) algorithm shows that it permits fast implementations while maintaining performance equivalent to that of the widely used LMS adaptive filter.
Abstract: Block digital filtering involves the calculation of a block or finite set of filter outputs from a block of input values. This paper presents a block adaptive filtering procedure in which the filter coefficients are adjusted once per each output block in accordance with a generalized least mean-square (LMS) algorithm. Analyses of convergence properties and computational complexity show that the block adaptive filter permits fast implementations while maintaining performance equivalent to that of the widely used LMS adaptive filter.
TL;DR: A theoretical study of topological excitations (kinks) in a one-dimensional one-third-filled Peierls system is presented in this article, where the charges associated with the kinks are found to be fractional.
Abstract: A theoretical study of topological excitations (kinks) in a one-dimensional one-third-filled Peierls system is presented. The charges associated with the kinks are found to be fractional $Q=\ifmmode\pm\else\textpm\fi{}\frac{1}{3}e,\ifmmode\pm\else\textpm\fi{}\frac{2}{3}e$. Calculations of the spatial widths and electronic structure of different types of kinks are carried out numerically. Possible applications to tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) are mentioned.
TL;DR: In this paper, Euler's rigid body equations are modified with the addition of a linear feedback, and a system of three quadratic differential equations is obtained which for certain feedback gains has two strange attractors.
TL;DR: Hadronic collision models based on quantum chromodynamics predict remarkably large cross sections for diffractive scattering of hadrons on a nuclear target as mentioned in this paper, where the diffraction arises from the transparency of a nucleus to the portion of the projectile wave function having small transverse separation between its constituents.
Abstract: Hadronic collision models based on quantum chromodynamics predict remarkably large cross sections for diffractive scattering of hadrons on a nuclear target. The diffraction arises from the transparency of a nucleus to the portion of the projectile wave function having small transverse separation between its constituents. Correspondingly, the typical transverse momentum within the diffracted system is significantly enhanced. This quantum-chromodynamics-based picture leads to large cross sections for diffractive charm production.
TL;DR: In this paper, the authors studied population models which have the following three ingredients: populations are divided into local sub-populations, local population dynamics are nonlinear and random events occur locally in space.
TL;DR: In this article, a set of random networks, increase the density of relations in these networks, and observe how the networks' structure develops in terms of five measures, and conclude that network density is not a useful indicator of structure and that direct measurement of structure is to be preferred.
TL;DR: This investigation systematically assessed whether autistic children's learning of discrimination tasks could be improved if they observed normal children perform the tasks correctly and found that when normal peers modeled correct responses, the autisticChildren's correct responding increased dramatically.
Abstract: Present research and legislation regarding mainstreaming autistic children into normal classrooms have raised the importance of studying whether autistic children can benefit from observing normal peer models. The present investigation systematically assessed whether autistic children's learning of discrimination tasks could be improved if they observed normal children perform the tasks correctly. In the context of a multiple baseline design, four autistic children worked on five discrimination tasks that their teachers reported were posing difficulty. Throughout the baseline condition the children evidenced very low levels of correct responding on all five tasks. In the subsequent treatment condition, when normal peers modeled correct responses, the autistic children's correct responding increased dramatically. In each case, the peer modeling procedure produced rapid achievement of the acquisition which was maintained after the peer models were removed. These results are discussed in relation to issues concerning observational learning and in relation to the implications for mainstreaming autistic children into normal classrooms.
TL;DR: This paper measured the stable isotopic composition of specimens of the branching reef coral Pocillopora damicornis which have grown in the field while seawater temperatures were continuously recorded.
Abstract: Reef corals, both fossil and recent, are potentially useful monitors of the surface ocean ‘climate’. Because coral reefs flourish only in relatively warm water1,2, the very presence of reef corals constrains the estimation of local temperature ranges. Studies of hermatypic corals have shown that coral growth rate3–8, density band formation (in some species)9–15, and stable isotopic composition14–23, all respond to variations in water temperature and light intensity. We have measured the stable isotopic composition of specimens of the branching reef coral Pocillopora damicornis which have grown in the field while seawater temperatures were continuously recorded. Detailed oxygen isotope profiles of branches of this species indicate that seasonal changes in temperature and seawater isotopic composition are precisely recorded. Isotopic profiles may be used to estimate growth rates of branching corals, which lack annual density banding. The method provides a technique for high resolution palaeoclimatic reconstruction of seasonal temperature ranges and accurate estimation of rates of reef carbonate production.
TL;DR: In this paper, a model for intermediate-valence compounds is considered that is based on correlated ionic states with ${n}_{0}$ and${n}{0}+1 f$ electrons and includes the hybridization with band electrons as a perturbation.
Abstract: A model for intermediate-valence compounds is considered that is based on correlated ionic states with ${n}_{0}$ and ${n}_{0}+1 f$ electrons and includes the hybridization with band electrons as a perturbation. The expansion is formulated diagrammatically with Goldstone diagrams for the strongly correlated on-site processes and Feynman propagators between different sites. Suitable infinite-order resummations of the on-site processes lead to Brillouin-Wigner-type self-consistency equations for the $f$ quasiparticle energy shifts. The imaginary part of the single-site $f$-level Green's function exhibits a spike above a continuum which vanishes at the Fermi level. Deviations from the Ruderman-Kittel-Kasuya-Yosida behavior are found for the intersite terms. The effect of the shift of the chemical potential due to the fixed number of electrons is discussed.
TL;DR: A new neuromuscular toxin, lophotoxin, has been isolated from several pacific gorgonians of the genus Lophogorgia, and belongs to the well-known cembrene class of diterpenoid molecules.
Abstract: A new neuromuscular toxin, lophotoxin, has been isolated from several pacific gorgonians of the genus Lophogorgia. The structure of lophotoxin was deduced by combined spectrochemical methods, and belongs to the well-known cembrene class of diterpenoid molecules. Lophotoxin contains furanoaldehyde and alpha, beta-epoxy-gamma-lactone functional groups, in sharp contrast to the cationic ammonium functional groups of the established neurotoxins.
TL;DR: For a given siphonophore species, the number of ingested prey was greatest at localities where prey organisms were most abundant in the surrounding seawater, and there was a tendency for more prey to be consumed at night.
Abstract: Prey consumption patterns are described for 24 species of epipelagic siphonophores studied during 1977–1980 in the Gulf of California, off Southern California, in the Sargasso Sea, and in Friday Harbor, Washington. Of the species, 7 were studied by day and at night, 15 were studied only by day, and 2 were studied only at night. Each of the 3 suborders of siphonophores had a characteristic diet. Siphonophores in the suborder Cystonectae, which had large gastrozooids, fed primarily on fish larvae. Species in the suborder Physonectae, which generally had few, large gastrozooids, consumed some small copepods, but consumed mainly large copepods and a variety of large, noncopepod prey. Species in the suborder Calycophorae, which generally had many small gastrozooids, fed mainly on small copepods, and also on other small prey organisms. The maximum size of prey tended to be correlated with gastrozooid length for all the siphonophores studied. For a given siphonophore species, the number of ingested prey was greatest at localities where prey organisms were most abundant in the surrounding seawater. For siphonophore species collected both day and night, there was a tendency for more prey to be consumed at night. Behavioral observations in the laboratory indicated that of 7 siphonophore species tested, 2 fed only in the light, and another fed only in the dark.
TL;DR: An algorithm is developed for calculating the horizons for each point in a digital terrain grid in order N iterations, whereas all previous methods seem to be of O(N2) time complexity.