433 research outputs found
Quantization and holomorphic anomaly
We study wave functions of B-model on a Calabi-Yau threefold in various
polarizations.Comment: 15 page
Conductivity sum rule, implication for in-plane dynamics and c-axis response
Recently observed -axis optical sum rule violations indicate non-Fermi
liquid in-plane behavior. For coherent -axis coupling, the observed flat,
nearly frequency independent -axis conductivity implies
a large in-plane scattering rate around and therefore any
pseudogap that might form at low frequency in the normal state will be smeared.
On the other hand incoherent -axis coupling places no restriction on the
value of and gives a more consistent picture of the observed sum rule
violation which, we find in some cases, can be less than half.Comment: 3 figures. To appear in PR
Media Effects Reconsidered
Arguments are presented for looking at cognitive outcomes as dependent variables in communication research rather than placing emphasis only on affective realms. This approach also brings attention to the independent-dependent variable emphases found in the communication literature over the last few decades. The social context of media use and the motivations that spring from this contextual embeddedness are also discussed with regard to information utility and the distribution of information availability. Finally a comment is offered on how these perspectives may relate to developments in new media technology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66556/2/10.1177_009365027400100205.pd
The Ruled Vertex and Nontoric del Pezzo Surfaces
We construct the topological partition function of local nontoric del Pezzo
surfaces using the ruled vertex formalism.Comment: 16 pages, 4 figure
A matrix model for the topological string II: The spectral curve and mirror geometry
In a previous paper, we presented a matrix model reproducing the topological
string partition function on an arbitrary given toric Calabi-Yau manifold.
Here, we study the spectral curve of our matrix model and thus derive, upon
imposing certain minimality assumptions on the spectral curve, the large volume
limit of the BKMP "remodeling the B-model" conjecture, the claim that
Gromov-Witten invariants of any toric Calabi-Yau 3-fold coincide with the
spectral invariants of its mirror curve.Comment: 1+37 page
Optical sum rule violation, superfluid weight and condensation energy in the cuprates
The model of hole superconductivity predicts that the superfluid weight in
the zero-frequency -function in the optical conductivity has an
anomalous contribution from high frequencies, due to lowering of the system's
kinetic energy upon entering the superconducting state. The lowering of kinetic
energy, mainly in-plane in origin, accounts for both the condensation energy of
the superconductor as well as an increased potential energy due to larger
Coulomb repulsion in the paired state. It leads to an apparent violation of the
conductivity sum rule, which in the clean limit we predict to be substantially
larger for in-plane than for c-axis conductivity. However, because cuprates are
in the dirty limit for c-axis transport, the sum rule violation is found to be
greatly enhanced in the c-direction. The model predicts the sum rule violation
to be largest in the underdoped regime and to decrease with doping, more
rapidly in the c-direction that in the plane. So far, experiments have detected
sum rule violation in c-axis transport in several cuprates, as well as a
decrease and disappearance of this violation for increasing doping, but no
violation in-plane. We explore the predictions of the model for a wide range of
parameters, both in the absence and in the presence of disorder, and the
relation with current experimental knowledge.Comment: submitted to Phys.Rev.
Optical Sum Rule anomalies in the High-Tc Cuprates
We provide a brief summary of the observed sum rule anomalies in the
high-T cuprate materials. A recent issue has been the impact of a
non-infinite frequency cutoff in the experiment. In the normal state, the
observed anomalously high temperature dependence can be explained as a `cutoff
effect'. The anomalous rise in the optical spectral weight below the
superconducting transition, however, remains as a solid experimental
observation, even with the use of a cutoff frequency.Comment: 4 pages, 2 figures, very brief review of optical sum rule anomal
A framework for the analysis of the potential performance of Chief Information Officers
Information Systems Function is an organisational area of major importance in the context of the competitive development of organisations. At the centre of the Information Systems Function we find the Chief Information Officer (CIO), who is the main responsible for the organisation and leadership of this function. Given the nature of the duties assigned to the CIO, her/his work directly influences the development of an organisation, so it has become important to assess her/his potential performance before s/he finds herself/him in charge of the information systems function. This article proposes the CIO Performance Square - a framework for analysing the potential performance of CIOs based on their education and experience.- (undefined
Shear viscosity of the Quark-Gluon Plasma from a virial expansion
We calculate the shear viscosity in the quark-gluon plasma (QGP) phase
within a virial expansion approach with particular interest in the ratio of
to the entropy density , i.e. . The virial expansion approach
allows us to include the interactions between the partons in the deconfined
phase and to evaluate the corrections to a single-particle partition function.
In the latter approach we start with an effective interaction with parameters
fixed to reproduce thermodynamical quantities of QCD such as energy and/or
entropy density. We also directly extract the effective coupling \ga_{\rm V}
for the determination of . Our numerical results give a ratio
at the critical temperature , which is very
close to the theoretical bound of . Furthermore, for temperatures
the ratio is in the range of the present
experimental estimates at RHIC. When combining our results for
in the deconfined phase with those from chiral perturbation theory or
the resonance gas model in the confined phase we observe a pronounced minimum
of close to the critical temperature .Comment: Published in Eur. Phys. J. C, 7 pages, 2 figures, 3 tabl
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