5,146 research outputs found
Logarithmic conformal field theories with continuous weights
We study the logarithmic conformal field theories in which conformal weights
are continuous subset of real numbers. A general relation between the
correlators consisting of logarithmic fields and those consisting of ordinary
conformal fields is investigated. As an example the correlators of the
Coulomb-gas model are explicitly studied.Comment: Latex, 12 pages, IPM preprint, to appear in Phys. Lett.
The Logarithmic Conformal Field Theories
We study the correlation functions of logarithmic conformal field theories.
First, assuming conformal invariance, we explicitly calculate two-- and three--
point functions. This calculation is done for the general case of more than one
logarithmic field in a block, and more than one set of logarithmic fields. Then
we show that one can regard the logarithmic field as a formal derivative of the
ordinary field with respect to its conformal weight. This enables one to
calculate any -- point function containing the logarithmic field in terms of
ordinary --point functions. At last, we calculate the operator product
expansion (OPE) coefficients of a logarithmic conformal field theory, and show
that these can be obtained from the corresponding coefficients of ordinary
conformal theory by a simple derivation.Comment: 17 pages ,latex , some minor changes, to appear in Nucl. Phys.
A Logarithmic Conformal Field Theory Solution For Two Dimensional Magnetohydrodynamics In Presence of The Alf'ven Effect
When Alf`ven effect is peresent in magnetohydrodynamics one is naturally lead
to consider conformal field theories, which have logarithmic terms in their
correlation functions. We discuss the implications of such logarithmic terms
and find a unique conformal field theory with centeral charge
, within the border of the minimal series, which satisfies
all the constraints. The energy espectrum is found to be \newline .Comment: Latex, 9 page
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Impact of void ratio and state parameters on the small strain shear modulus of unsaturated soils
Zero tension Kardar-Parisi-Zhang equation in (d+1)- Dimensions
The joint probability distribution function (PDF) of the height and its
gradients is derived for a zero tension -dimensional Kardar-Parisi-Zhang
(KPZ) equation. It is proved that the height`s PDF of zero tension KPZ equation
shows lack of positivity after a finite time . The properties of zero
tension KPZ equation and its differences with the case that it possess an
infinitesimal surface tension is discussed. Also potential relation between the
time scale and the singularity time scale of the KPZ
equation with an infinitesimal surface tension is investigated.Comment: 18 pages, 8 figure
Quantum teleportation with nonclassical correlated states in noninertial frames
Quantum teleportation is studied in noninertial frame, for fermionic case,
when Alice and Bob share a general nonclassical correlated state. In
noninertial frames two fidelities of teleportation are given. It is found that
the average fidelity of teleportation from a separable and nonclassical
correlated state is increasing with the amount of nonclassical correlation of
the state. However, for any particular nonclassical correlated state, the
fidelity of teleportation decreases by increasing the acceleration.Comment: 10 pages, 3 figures, expanded version to appear in Quantum Inf.
Proces
Cryoprotectant-free vitrification of human spermatozoa in new artificial seminal fluid
Vitrification is a new method that has been recently introduced in Assisted Reproduction Technique programs. The aim of this study was to design a new medium similar to normal human seminal fluid (SF), formulation artificial seminal fluid (ASF), and to compare the cryoprotective potency of this medium with SF and human tubal fluid (HTF) medium. Thirty normal ejaculates were processed with the swim-up technique and sperm suspensions were divided into four aliquots: (i) fresh sample (control); (ii) vitrification in HTF medium supplemented with 5 mg/mL human serum albumin and 0.25 mol sucrose (Vit HTF); (iii) vitrification with patients' SF (Vit SF); and (iv) vitrification in ASF (Vit ASF). After warming, sperm parameters of motility, viability, and morphology were analyzed using WHO criteria. Also, sperm pellets were fixed in 2.5% glutaraldehyde and processed for scanning electron microscopy and transmission electron microscopy observations. The results showed that progressive motility (46.09 ± 10.33 vs. 36.80 ± 13.75), grade A motility (36.59 ± 11.40 vs. 16.41 ± 11.24), and normal morphology (18.74 ± 8.35 vs. 11.85 ± 5.84) and viability (68.22 ± 10.83 vs. 60.86 ± 11.72) of spermatozoa were significantly higher in Vit ASF than in Vit HTF. All parameters were better in Vit ASF than in Vit SF, but only viability was significantly different (p = 0.006). After cryopreservation, deep invagination in cytoplasm and mechanically weak point sites and folded tail were commonly observed. But, this phenomenon was more significant in Vit HTF and Vit SF than in ASF (p < 0.05). In transmission electron microscopy evaluation, acrosome damage, plasma membrane loss, chromatin vacuolation, and disruption of mitochondria arrangement and structures were observed in all vitrified groups. Adherence of several tail sections together was also seen in all cryo groups. But this was seen more in Vit HTF and Vit SF than in ASF (p < 0.05). In conclusion, vitrification of human spermatozoa with ASF can effectively preserve the quality of sperm motility in comparison with Vit HTF. © 2016 American Society of Andrology and European Academy of Andrology
Pseudospectral Model Predictive Control under Partially Learned Dynamics
Trajectory optimization of a controlled dynamical system is an essential part
of autonomy, however many trajectory optimization techniques are limited by the
fidelity of the underlying parametric model. In the field of robotics, a lack
of model knowledge can be overcome with machine learning techniques, utilizing
measurements to build a dynamical model from the data. This paper aims to take
the middle ground between these two approaches by introducing a semi-parametric
representation of the underlying system dynamics. Our goal is to leverage the
considerable information contained in a traditional physics based model and
combine it with a data-driven, non-parametric regression technique known as a
Gaussian Process. Integrating this semi-parametric model with model predictive
pseudospectral control, we demonstrate this technique on both a cart pole and
quadrotor simulation with unmodeled damping and parametric error. In order to
manage parametric uncertainty, we introduce an algorithm that utilizes Sparse
Spectrum Gaussian Processes (SSGP) for online learning after each rollout. We
implement this online learning technique on a cart pole and quadrator, then
demonstrate the use of online learning and obstacle avoidance for the dubin
vehicle dynamics.Comment: Accepted but withdrawn from AIAA Scitech 201
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