1,358 research outputs found
Asperisporium and Pantospora (Mycosphaerellaceae): epitypifications and phylogenetic placement
The species-rich family Mycosphaerellaceae contains considerable morphological diversity and includes numerous anamorphic genera, many of which are economically important plant pathogens. Recent revisions and phylogenetic research have resulted in taxonomic instability. Ameliorating this problem requires phylogenetic placement of type species of key genera. We present an examination of the type species of the anamorphic Asperisporium and Pantospora. Cultures isolated from recent port interceptions were studied and described, and morphological studies were made of historical and new herbarium specimens. DNA sequence data from the ITS region and nLSU were generated from these type species, analysed phylogenetically, placed into an evolutionary context within Mycosphaerellaceae, and compared to existing phylogenies. Epitype specimens associated with living cultures and DNA sequence data are designated herein. Asperisporium caricae, the type of Asperisporium and cause of a leaf and fruit spot disease of papaya, is closely related to several species of Passalora including P. brachycarpa. The status of Asperisporium as a potential generic synonym of Passalora remains unclear. The monotypic genus Pantospora, typified by the synnematous Pantospora guazumae, is not included in Pseudocercospora sensu stricto or sensu lato. Rather, it represents a distinct lineage in the Mycosphaerellaceae in an unresolved position near Mycosphaerella microsora
High-Temperature Properties of the Z(3) Interface in (2+1)-D SU(3) Gauge Theory
We study the high-temperature properties of the Z(3) interface which forms
between the various ordered phases of pure SU(3) gauge theory above a critical
temperature. On a (2+1)-D Euclidean lattice, we perform an accurate measurement
of the interface tension, which shows good agreement with the prediction of
perturbation theory. We also examine the behaviour of the Debye electric
screening mass, and compare this with theoretical predictions.Comment: 10 pages, 3 figures, uuencoded gzipped tar fil
-- mixing and oblique corrections in an model
A global fit for experiments is included in this revised version.Comment: IFP-460-UNC, TRI-PP-93-11, 20 pages, 2 figures are appende
Critical properties of the Z(3) interface in (2+1)-D SU(3) gauge theory
We study the interface between two different Z(3) vacua in the deconfined
phase of SU(3) pure gauge theory in 2+1 dimensions just above the critical
temperature. In simulations of the Euclidean lattice gauge theory formulation
of the system we measure the fluctuations of the interface as the critical
temperature is approached and as a function of system size. We show that the
intrinsic width of the interface remains small even very close to the critical
temperature. Some dynamical exponents which govern the interaction of the
interface with our Monte Carlo algorithm are also estimated. We conclude that
the Z(3) interface has properties broadly similar to those in many other
comparable statistical mechanical systems.Comment: 26 pages, LaTex with 16 postscript figure
Impurity state in Haldane gap for S=1 Heisenberg antiferromagnetic chain with bond doping
Using a new impurity density matrix renormalization group scheme, we
establish a reliable picture of how the low lying energy levels of a
Heisenberg antiferromagnetic chain change {\it quantitatively} upon bond
doping. A new impurity state gradually occurs in the Haldane gap as ,
while it appears only if with as . The
system is non-perturbative as . This explains the
appearance of a new state in the Haldane gap in a recent experiment on
YCaBaNiO [J.F. DiTusa, et al., Phys. Rev. Lett. 73 1857(1994)].Comment: 4 pages of uuencoded gzip'd postscrip
Franck-Condon Effect in Central Spin System
We study the quantum transitions of a central spin surrounded by a
collective-spin environment. It is found that the influence of the
environmental spins on the absorption spectrum of the central spin can be
explained with the analog of the Franck-Condon (FC) effect in conventional
electron-phonon interaction system. Here, the collective spins of the
environment behave as the vibrational mode, which makes the electron to be
transitioned mainly with the so-called "vertical transitions" in the
conventional FC effect. The "vertical transition" for the central spin in the
spin environment manifests as, the certain collective spin states of the
environment is favored, which corresponds to the minimal change in the average
of the total spin angular momentum.Comment: 8 pages, 8 figure
Relational Hidden Variables and Non-Locality
We use a simple relational framework to develop the key notions and results
on hidden variables and non-locality. The extensive literature on these topics
in the foundations of quantum mechanics is couched in terms of probabilistic
models, and properties such as locality and no-signalling are formulated
probabilistically. We show that to a remarkable extent, the main structure of
the theory, through the major No-Go theorems and beyond, survives intact under
the replacement of probability distributions by mere relations.Comment: 42 pages in journal style. To appear in Studia Logic
Three loop renormalization of the SU(N_c) non-abelian Thirring model
We renormalize to three loops a version of the Thirring model where the
fermion fields not only lie in the fundamental representation of a non-abelian
colour group SU(N_c) but also depend on the number of flavours, N_f. The model
is not multiplicatively renormalizable in dimensional regularization due to the
generation of evanescent operators which emerge at each loop order. Their
effect in the construction of the true wave function, mass and coupling
constant renormalization constants is handled by considering the projection
technique to a new order. Having constructed the MSbar renormalization group
functions we consider other massless independent renormalization schemes to
ensure that the renormalization is consistent with the equivalence of the
non-abelian Thirring model with other models with a four-fermi interaction. One
feature to emerge from the computation is the establishment of the fact that
the SU(N_f) Gross Neveu model is not multiplicatively renormalizable in
dimensional regularization. An evanescent operator arises first at three loops
and we determine its associated renormalization constant explicitly.Comment: 40 latex pages, 14 postscript figure
Cavity QED and quantum information processing with "hot" trapped atoms
We propose a method to implement cavity QED and quantum information
processing in high-Q cavities with a single trapped but non-localized atom. The
system is beyond the Lamb-Dick limit due to the atomic thermal motion. Our
method is based on adiabatic passages, which make the relevant dynamics
insensitive to the randomness of the atom position with an appropriate
interaction configuration. The validity of this method is demonstrated from
both approximate analytical calculations and exact numerical simulations. We
also discuss various applications of this method based on the current
experimental technology.Comment: 14 pages, 8 figures, Revte
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