1,655 research outputs found
Transport Coefficients of Quark Gluon Plasma for Pure Gauge Models
The transport coefficients of quark gluon plasma are calculated on a lattice
16**3X8, with the pure gauge models. Matsubara Green's functions of energy
momentum tensors have very large fluctuations and about a few million MC sweeps
are needed to reduce the errors reasonably small in the case of the standard
action. They are much suppressed if Iwasaki's improved action is employed.
Preliminary results show that the transport coefficients roughly depend on the
coupling constant as a**(-3)(g) in the case of SU(2).Comment: Talk presented at LATTICE96(finite temperature), 3 pages in latex, 4
Postscript figure
Phylogeny of Discosia and Seimatosporium, and introduction of Adisciso and Immersidiscosia genera nova
Discosia (teleomorph unknown) and Seimatosporium (teleomorph Discostroma) are saprobic or plant pathogenic, coelomycetous genera of so-called ‘pestalotioid fungi’ within the Amphisphaeriaceae (Xylariales). They share several morphological features and their generic circumscriptions appear unclear. We investigated the phylogenies of both genera on the basis of SSU, LSU and ITS nrDNA and β-tubulin gene sequences. Discosia was not monophyletic and was separated into two distinct lineages. Discosia eucalypti deviated from Discosia clade and was transferred to a new genus, Immersidiscosia, characterised by deeply immersed, pycnidioid conidiomata that are intraepidermal to subepidermal in origin, with a conidiomatal beak having periphyses. Subdividing Discosia into ‘sections’ was not considered phylogenetically significant at least for the three sections investigated (sect. Discosia, Laurina, and Strobilina). We recognised Seimatosporium s.l. as a monophyletic genus. An undescribed species belonging to Discosia with its associated teleomorph was collected on living leaves of Symplocos prunifolia from Yakushima Island, Japan. We have therefore established a new teleomorphic genus, Adisciso, for this new species, A. yakushimense. Discostroma tricellulare (anamorph: Seimatosporium azaleae), previously described from Rhododendron species, was transferred to Adisciso based on morphological and phylogenetic grounds. Adisciso is characterised by relatively small-sized ascomata without stromatic tissue, obclavate to broadly cylindrical asci with biseriate ascospores that have 2 transverse septa, and its Discosia anamorph. Based on these features, it can easily be distinguished from Discostroma, a similar genus within the Amphisphaeriaceae
Conductivity landscape of highly oriented pyrolytic graphite surface containing ribbons and edges
We present an extensive study on electrical spectroscopy of graphene ribbons
and edges of highly oriented pyrolytic graphite (HOPG) using atomic force
microscope (AFM). We have addressed in the present study two main issues, (1)
How does the electrical property of the graphite (graphene) sheet change when
the graphite layer is displaced by shear forces? and (2) How does the
electrical property of the graphite sheet change across a step edge? While
addressing these two issues we observed, (1) variation of conductance among the
graphite ribbons on the surface of HOPG. The top layer always exhibits more
conductance than the lower layers, (2) two different monolayer ribbons on the
same sheet of graphite shows different conductance, (3) certain ribbon/sheet
edges show sharp rise in current, (4) certain ribbons/sheets on the same edge
shows both presence and absense of the sharp rise in the current, (5) some
lower layers at the interface near a step edge shows a strange dip in the
current/conductance (depletion of charge). We discuss possible reasons for such
rich conducting landscape on the surface of graphite.Comment: 13 pages, 9 figures. For better quality figures please contact autho
Cu- and Cl-NMR Studies of Triplet Localization in the Quantum Spin System NHCuCl
Cu- and Cl-NMR experiments were performed to investigate
triplet localization in the dimer compound NHCuCl, which shows
magnetization plateaus at one-quarter and three-quarters of the saturation
magnetization. In Cu-NMR experiments, signal from only the singlet Cu
site was observed, because that from the triplet Cu site was invisible due to
the strong spin fluctuation of onsite 3-spins. We found that the temperature
dependence of the shift of Cu-NMR spectra at the singlet Cu site
deviated from that of macroscopic magnetization below T=6 K. This deviation is
interpreted as the triplet localization in this system. From the
Cl-NMR experiments at the 1/4-plateau phase, we found the two
different temperature dependences of Cl-shift, namely the temperature
dependence of one deviates below T=6 K from that of the macroscopic
magnetization as observed in the Cu-NMR experiments, whereas the
other corresponds well with that of the macroscopic magnetization in the entire
experimental temperature region. We interpreted these dependences as reflecting
the transferred hyperfine field at the Cl site located at a singlet site and at
a triplet site, respectively. This result also indicates that the triplets are
localized at low temperatures. Cu-NMR experiments performed at high
magnetic fields between the one-quarter and three-quarters magnetization
plateaus have revealed that the two differently oriented dimers in the unit
cell are equally occupied by triplets, the fact of which limits the theoretical
model on the periodic structure of the localized triplets.Comment: 19 pages, 9 figures, submitted to PRB (in press
Metal-Insulator Transition and Spin Degree of Freedom in Silicon 2D Electron Systems
Magnetotransport in 2DES's formed in Si-MOSFET's and Si/SiGe quantum wells at
low temperatures is reported. Metallic temperature dependence of resistivity is
observed for the n-Si/SiGe sample even in a parallel magnetic field of 9T,
where the spins of electrons are expected to be polarized completely.
Correlation between the spin polarization and minima in the diagonal
resistivity observed by rotating the samples for various total strength of the
magnetic field is also investigated.Comment: 3 pages, RevTeX, 4 eps-figures, conference paper (EP2DS-13
Estimation of Spin-Spin Interaction by Weak Measurement Scheme
Precisely knowing an interaction Hamiltonian is crucial to realize quantum
information tasks, especially to experimentally demonstrate a quantum computer
and a quantum memory. We propose a scheme to experimentally evaluate the
spin-spin interaction for a two-qubit system by the weak measurement technique
initiated by Yakir Aharonov and his colleagues. Furthermore, we numerically
confirm our proposed scheme in a specific system of a nitrogen vacancy center
in diamond. This means that the weak measurement can also be taken as a
concrete example of the quantum process tomography.Comment: 4 pages, 1 table, 2 figures, to appear in Europhysics Letter
Poincar\'{e} gauge theory of gravity
A Poincar\'{e} gauge theory of (2+1)-dimensional gravity is developed.
Fundamental gravitational field variables are dreibein fields and Lorentz gauge
potentials, and the theory is underlain with the Riemann-Cartan space-time. The
most general gravitational Lagrangian density, which is at most quadratic in
curvature and torsion tensors and invariant under local Lorentz transformations
and under general coordinate transformations, is given. Gravitational field
equations are studied in detail, and solutions of the equations for weak
gravitational fields are examined for the case with a static, \lq \lq spin"less
point like source. We find, among other things, the following: (1)Solutions of
the vacuum Einstein equation satisfy gravitational field equations in the
vacuum in this theory. (2)For a class of the parameters in the gravitational
Lagrangian density, the torsion is \lq \lq frozen" at the place where \lq \lq
spin" density of the source field is not vanishing. In this case, the field
equation actually agrees with the Einstein equation, when the source field is
\lq \lq spin"less. (3)A teleparallel theory developed in a previous paper is
\lq \lq included as a solution" in a limiting case. (4)A Newtonian limit is
obtainable, if the parameters in the Lagrangian density satisfy certain
conditions.Comment: 27pages, RevTeX, OCU-PHYS-15
Large Diffeomorphisms in (2+1)-Quantum Gravity on the Torus
The issue of how to deal with the modular transformations -- large
diffeomorphisms -- in (2+1)-quantum gravity on the torus is discussed. I study
the Chern-Simons/connection representation and show that the behavior of the
modular transformations on the reduced configuration space is so bad that it is
possible to rule out all finite dimensional unitary representations of the
modular group on the Hilbert space of -functions on the reduced
configuration space. Furthermore, by assuming piecewise continuity for a dense
subset of the vectors in any Hilbert space based on the space of complex valued
functions on the reduced configuration space, it is shown that finite
dimensional representations are excluded no matter what inner-product we define
in this vector space. A brief discussion of the loop- and ADM-representations
is also included.Comment: The proof for the nonexistence of the one- and two-dimensional
representations of PSL(2,Z) in the relevant Hilbert space, has been extended
to cover all finite dimensional unitary representations. The notation is
slightly improved and a few references are added
Complex joint probabilities as expressions of determinism in quantum mechanics
The density operator of a quantum state can be represented as a complex joint
probability of any two observables whose eigenstates have non-zero mutual
overlap. Transformations to a new basis set are then expressed in terms of
complex conditional probabilities that describe the fundamental relation
between precise statements about the three different observables. Since such
transformations merely change the representation of the quantum state, these
conditional probabilities provide a state-independent definition of the
deterministic relation between the outcomes of different quantum measurements.
In this paper, it is shown how classical reality emerges as an approximation to
the fundamental laws of quantum determinism expressed by complex conditional
probabilities. The quantum mechanical origin of phase spaces and trajectories
is identified and implications for the interpretation of quantum measurements
are considered. It is argued that the transformation laws of quantum
determinism provide a fundamental description of the measurement dependence of
empirical reality.Comment: 12 pages, including 1 figure, updated introduction includes
references to the historical background of complex joint probabilities and to
related work by Lars M. Johanse
Dimensions and clusters of aesthetic emotions: A semantic profile analysis
Aesthetic emotions are elicited by different sensory impressions generated by music, visual arts, literature, theater, film, or nature scenes. Recently, the AESTHEMOS scale has been developed to facilitate the empirical assessment of such emotions. In this article we report a semantic profile analysis of aesthetic emotion terms that had been used for the development of this scale, using the GRID approach. This method consists of obtaining ratings of emotion terms on a set of meaning facets (features) which represent five components of the emotion process (appraisal, bodily reactions, action tendencies, expression, and feelings). The aims here were (a) to determine the dimensionality of the GRID features when applied to aesthetic emotions and compare it to published results for emotion terms in general, and (b) to examine the internal organization of the domain of aesthetic emotion terms in order to identify salient clusters of these items based on the similarity of their feature profiles on the GRID. Exploratory Principal Component Analyses suggest a four-dimensional structure of the semantic space consisting of valence, power, arousal, and novelty, converging with earlier GRID studies on large sets of standard emotion terms. Using cluster analyses, 15 clusters of aesthetic emotion terms with similar GRID feature profiles were identified, revealing the internal organization of the aesthetic emotion terms domain and meaningful subgroups of aesthetic emotions. While replication for further languages is required, these findings provide a solid basis for further research and methodological development in the realm of aesthetic emotions
- …