325 research outputs found
Instanton -- Antiinstanton interaction and asymptotics of perturbation theory expansion in double well oscillator
Instanton -- antiinstanton pair is considered as a source of singularity at
the Borel plane for the ground state energy of anharmonic oscillator. The
problem of defining the short range instanton -- antiinstanton interaction
reduces to calculation of a smooth part of the Borel function, which cannot be
found without explicit calculation of several terms of ordinary perturbation
theory. On the other hand, the large order terms of perturbative expansion are
dominated by large fluctuations in the functional integral like well separated
instanton and antiinstanton.
The preasymptotics () of large order perturbation theory
contribution to the ground state energy of anharmonic oscillator was found
analytically. To this end the subleading long range asymptotics of the
classical instanton -- antiinstanton interaction, the one -- loop quantum
contribution to instanton -- antiinstanton interaction and the second quantum
correction to a single instanton density were considered.Comment: 12 pages, Latex, BUDKERINP 94-2
The diagnosis of trypanosome infections: applications of novel technology for reducing disease risk
Reliable DNA based methodologies to determine prevalence of trypanosome species in domestic livestock have been available for over 10 years. Despite this, they are rarely used to generate baseline data for control operations for these diseases in the field. Rather, such operations tend to rely on data which can be generated using low technology methods such as direct observation of parasites by light microscopy. Here we show the pitfalls of relying on such low tech methodology which, although simple in its application, can provide inaccurate and inadequate data on which to base control methodologies. Our analysis of 61 cattle selected for trypanosome carrier status by either microscopy, low PCV or poor condition score, showed that 90% were infected with trypanosomes while 84% of the total were infected with T. brucei. Diagnosis by PCR on buffy coat preparations on Whatman® FTA® matrices was the most sensitive methodology relative to the gold standard, whereas microscopy was the least sensitive.
(African Journal of Biotechnology: 2002 1(2): 39-45
Thermal Decay of the Cosmological Constant into Black Holes
We show that the cosmological constant may be reduced by thermal production
of membranes by the cosmological horizon, analogous to a particle ``going over
the top of the potential barrier", rather than tunneling through it. The
membranes are endowed with charge associated with the gauge invariance of an
antisymmetric gauge potential. In this new process, the membrane collapses into
a black hole, thus the net effect is to produce black holes out of the vacuum
energy associated with the cosmological constant. We study here the
corresponding Euclidean configurations ("thermalons"), and calculate the
probability for the process in the leading semiclassical approximation.Comment: 14 pages, 6 figures. Minor correction
Recommended from our members
Advanced thermally stable jet fuels: Technical progress report, July 1994--September 1994
There are five tasks within this project on thermally stable coal-based jet fuels. Progress on each of the tasks is described. Task 1, Investigation of the quantitative degradation chemistry of fuels, has 3 subtasks which are described: Pyrolysis of n-alkylbenzenes; Thermal decomposition of n-tetradecane in near-critical region; and Re-examining the effects of reactant and inert gas pressure on tetradecane pyrolysis--Effect of cold volume in batch reactor. Under Task 2, Investigation of incipient deposition, the subtask reported is Uncertainty analysis on growth and deposition of particles during heating of coal-derived aviation gas turbine fuels; under Task 3, Investigation of the quantitative degradation chemistry of fuels, is subtask, Effects of high surface area activated carbon and decalin on thermal degradation of jet A-1 fuel and n-dodecane; under Task 4, Coal-based fuel stabilization studies, is subtask, Screening potential jet fuel stabilizers using the model compound dodecane; and under Task 5, Exploratory studies on the direct conversion of coal to high quality jet fuels, is subtask, Shape-selective naphthalene hydrogenation for production of thermally stable jet fuels. 25 refs., 64 figs., 22 tabs
Recommended from our members
Advanced thermally stable jet fuels: Technical progress report, October 1994--December 1994
There are five tasks within this project on thermally stable coal-based jet fuels. Progress on each of the tasks is described. Task 1, Investigation of the quantitative degradation chemistry of fuels, has 5 subtasks which are described: Literature review on thermal stability of jet fuels; Pyrolytic and catalytic reactions of potential endothermic fuels: cis- and trans-decalin; Use of site specific {sup 13}C-labeling to examine the thermal stressing of 1-phenylhexane: A case study for the determination of reaction kinetics in complex fuel mixtures versus model compound studies; Estimation of critical temperatures of jet fuels; and Surface effects on deposit formation in a flow reactor system. Under Task 2, Investigation of incipient deposition, the subtask reported is Uncertainty analysis on growth and deposition of particles during heating of coal-derived aviation gas turbine fuels; under Task 3, Characterization of solid gums, sediments, and carbonaceous deposits, is subtask, Studies of surface chemistry of PX-21 activated carbon during thermal degradation of jet A-1 fuel and n-dodecane; under Task 4, Coal-based fuel stabilization studies, is subtask, Exploratory screening and development potential of jet fuel thermal stabilizers over 400 C; and under Task 5, Exploratory studies on the direct conversion of coal to high quality jet fuels, are 4 subtasks: Novel approaches to low-severity coal liquefaction and coal/resid co-processing using water and dispersed catalysts; Shape-selective naphthalene hydrogenation for production of thermally stable jet fuels; Design of a batch mode and a continuous mode three-phase reactor system for the liquefaction of coal and upgrading of coal liquids; and Exploratory studies on coal liquids upgrading using mesopores molecular sieve catalysts. 136 refs., 69 figs., 24 tabs
Tunneling into Extra Dimension and High-Energy Violation of Lorentz Invariance
We consider a class of models with infinite extra dimension, where bulk space
does not possess SO(1,3) invariance, but Lorentz invariance emerges as an
approximate symmetry of the low-energy effective theory. In these models, the
maximum attainable speeds of the graviton, gauge bosons and scalar particles
are automatically equal to each other and smaller than the maximum speed in the
bulk. Additional fine-tuning is needed in order to assure that the maximum
attainable speed of fermions takes the same value. A peculiar feature of our
scenario is that there are no truly localized modes. All four-dimensional
particles are resonances with finite widths. The latter depends on the energy
of the particle and is naturally small at low energies.Comment: 21 pages, references and comments added, final version to appear in
JHE
Frustration and the Kondo effect in heavy fermion materials
The observation of a separation between the antiferromagnetic phase boundary
and the small-large Fermi surface transition in recent experiments has led to
the proposal that frustration is an important additional tuning parameter in
the Kondo lattice model of heavy fermion materials. The introduction of a Kondo
(K) and a frustration (Q) axis into the phase diagram permits us to discuss the
physics of heavy fermion materials in a broader perspective. The current
experimental situation is analysed in the context of this combined "QK" phase
diagram. We discuss various theoretical models for the frustrated Kondo
lattice, using general arguments to characterize the nature of the -electron
localization transition that occurs between the spin liquid and heavy Fermi
liquid ground-states. We concentrate in particular on the Shastry--Sutherland
Kondo lattice model, for which we establish the qualitative phase diagram using
strong coupling arguments and the large- expansion. The paper closes with
some brief remarks on promising future theoretical directions.Comment: To appear in a special issue of JLT
- …