12,073 research outputs found
Comment on "Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn"
Recently, Rourke et al. reported point-contact spectroscopy results on the
heavy-fermion superconductor CeCoIn [1]. They obtained conductance spectra
on the c-axis surfaces of CeCoIn single crystals. Their major claims are
two-fold: CeCoIn has i) d-wave pairing symmetry and ii) two coexisting
order parameter components. In this Comment, we show that these claims are not
warranted by the data presented. [1] Rourke et al., Phys. Rev. Lett. 94, 107005
(2005).Comment: accepted for publication in Phys. Rev. Lett., final for
&-prolog and its performance: exploiting independent and-parallelism
An Independent And-Parallel Prolog model and implementation, &-Prolog, are described. The description includes a summary of the system's architecture, some details of its execution model (based on the RAP-WAM model), and most importantly, its performance on sequential workstations and shared memory multiprocessors as compared with state-of-the-art Prolog systems. Speedup curves are provided for a collection of benchmark programs which demónstrate significant speed advantages over state-of the art sequential systems
K\"ahler Potential of Moduli Space of Calabi-Yau -fold embedded in
We study a kaehler potential K of a one parameter family of Calabi-Yau d-fold
embedded in CP^{d+1}. By comparing results of the topological B-model and the
data of the CFT calculation at Gepner point, the K is determined unambiguously.
It has a moduli parameter psi that describes a deformation of the CFT by a
marginal operator. Also the metric, curvature and hermitian two-point functions
in the neighborhood of the Gepner point are analyzed. We use a recipe of tt^{*}
fusion and develop a method to determine the K from the point of view of
topological sigma model. It is not restricted to this specific model and can be
applied to other Calabi-Yau cases.Comment: 10 pages, 2 figure
Optimizing the speed of a Josephson junction
We review the application of dynamical mean-field theory to Josephson
junctions and study how to maximize the characteristic voltage IcRn which
determines the width of a rapid single flux quantum pulse, and thereby the
operating speed in digital electronics. We study a wide class of junctions
ranging from SNS, SCmS (where Cm stands for correlated metal), SINIS (where the
insulating layer is formed from a screened dipole layer), and SNSNS structures.
Our review is focused on a survey of the physical results; the formalism has
been developed elsewhere.Comment: (36 pages, 15 figures, to appear in Int. J. Mod. Phys. B
The &-prolog system: Exploiting independent and-parallelism
The &-Prolog system, a practical implementation of a parallel execution niodel for Prolog exploiting strict and non-strict independent and-parallelism, is described. Both automatic and manual parallelization of programs is supported. This description includes a summary of the system's language and architecture, some details of its execution model (based on the RAP-WAM model), and data on its performance on sequential workstations and shared memory multiprocessors, which is compared to that of current Prolog systems. The results to date show significant speed advantages over state-of-the-art sequential systems
On Free Quotients of Complete Intersection Calabi-Yau Manifolds
In order to find novel examples of non-simply connected Calabi-Yau
threefolds, free quotients of complete intersections in products of projective
spaces are classified by means of a computer search. More precisely, all
automorphisms of the product of projective spaces that descend to a free action
on the Calabi-Yau manifold are identified.Comment: 39 pages, 3 tables, LaTe
Construction of a Cantilever-Andreev-Tunneling rig and its applications to superconductors
A technique for point-contact spectroscopy, based on an electro-mechanical
mechanism for the contact formation, has been developed. It is designed to be
used in both He and He cryostats. The performance has been demonstrated
by conductance measurements on various kinds of superconductors, including the
conventional superconductor Nb, the two-band superconductor MgB, and the
heavy-fermion superconductor CeCoIn. Characteristic conductance spectra
obtained prove this technique is useful for the investigation of the
superconducting order parameter. Advantages of this technique such as its
simplicity and versatility are described.Comment: 7 Pages, 7 figures, typeset in LaTeX, submitted to Rev. Sci. Instru
The Josephson current in Fe-based superconducting junctions: theory and experiment
We present theory of dc Josephson effect in contacts between Fe-based and
spin-singlet -wave superconductors. The method is based on the calculation
of temperature Green's function in the junction within the tight-binding model.
We calculate the phase dependencies of the Josephson current for different
orientations of the junction relative to the crystallographic axes of Fe-based
superconductor. Further, we consider the dependence of the Josephson current on
the thickness of an insulating layer and on temperature. Experimental data for
PbIn/BaK(FeAs) point-contact Josephson junctions are
consistent with theoretical predictions for symmetry of an order
parameter in this material. The proposed method can be further applied to
calculations of the dc Josephson current in contacts with other new
unconventional multiorbital superconductors, such as and
superconducting topological insulator .Comment: 16 pages, 14 figure
Inositol for the prevention of neural tube defects: a pilot randomised controlled trial
Although peri-conceptional folic acid (FA) supplementation can prevent a proportion of neural tube defects (NTD), there is increasing evidence that many NTD are FA non-responsive. The vitamin-like molecule inositol may offer a novel approach to preventing FA-non-responsive NTD. Inositol prevented NTD in a genetic mouse model, and was well tolerated by women in a small study of NTD recurrence. In the present study, we report the Prevention of Neural Tube Defects by Inositol (PONTI) pilot study designed to gain further experience of inositol usage in human pregnancy as a preliminary trial to a future large-scale controlled trial to evaluate efficacy of inositol in NTD prevention. Study subjects were UK women with a previous NTD pregnancy who planned to become pregnant again. Of 117 women who made contact, ninety-nine proved eligible and forty-seven agreed to be randomised (double-blind) to peri-conceptional supplementation with inositol plus FA or placebo plus FA. In total, thirty-three randomised pregnancies produced one NTD recurrence in the placebo plus FA group (n 19) and no recurrences in the inositol plus FA group (n 14). Of fifty-two women who declined randomisation, the peri-conceptional supplementation regimen and outcomes of twenty-two further pregnancies were documented. Two NTD recurred, both in women who took only FA in their next pregnancy. No adverse pregnancy events were associated with inositol supplementation. The findings of the PONTI pilot study encourage a large-scale controlled trial of inositol for NTD prevention, but indicate the need for a careful study design in view of the unwillingness of many high-risk women to be randomised
Where does Cosmological Perturbation Theory Break Down?
We apply the effective field theory approach to the coupled metric-inflaton
system, in order to investigate the impact of higher dimension operators on the
spectrum of scalar and tensor perturbations in the short-wavelength regime. In
both cases, effective corrections at tree-level become important when the
Hubble parameter is of the order of the Planck mass, or when the physical wave
number of a cosmological perturbation mode approaches the square of the Planck
mass divided by the Hubble constant. Thus, the cut-off length below which
conventional cosmological perturbation theory does not apply is likely to be
much smaller than the Planck length. This has implications for the
observability of "trans-Planckian" effects in the spectrum of primordial
perturbations.Comment: 25 pages, uses FeynM
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