48 research outputs found
Colour, copies and confinement
In this paper we construct a wide class of Gribov copies in Coulomb gauge
SU(2) gauge theory. Infinitesimal copies are studied in some detail and their
non-perturbative nature is made manifest. As an application it is shown that
the copies prevent a non-perturbative definition of colour charge.Comment: 25 pages, 10 figures. Minor changes, two references added. Published
versio
On The Universality Class Of Little String Theories
We propose that Little String Theories in six dimensions are quasilocal
quantum field theories. Such field theories obey a modification of Wightman
axioms which allows Wightman functions (i.e. vacuum expectation values of
products of fundamental fields) to grow exponentially in momentum space.
Wightman functions of quasilocal fields in x-space violate microlocality at
short distances. With additional assumptions about the ultraviolet behavior of
quasilocal fields, one can define approximately local observables associated to
big enough compact regions. The minimum size of such a region can be
interpreted as the minimum distance which observables can probe. We argue that
for Little String Theories this distance is of order {\sqrt N}/M_s.Comment: 25 pages, late
Macdonald Polynomials from Sklyanin Algebras: A Conceptual Basis for the -Adics-Quantum Group Connection
We establish a previously conjectured connection between -adics and
quantum groups. We find in Sklyanin's two parameter elliptic quantum algebra
and its generalizations, the conceptual basis for the Macdonald polynomials,
which ``interpolate'' between the zonal spherical functions of related real and
\--adic symmetric spaces. The elliptic quantum algebras underlie the
\--Baxter models. We show that in the n \air \infty limit, the Jost
function for the scattering of {\em first} level excitations in the
\--Baxter model coincides with the Harish\--Chandra\--like \--function
constructed from the Macdonald polynomials associated to the root system .
The partition function of the \--Baxter model itself is also expressed in
terms of this Macdonald\--Harish\--Chandra\ \--function, albeit in a less
simple way. We relate the two parameters and of the Macdonald
polynomials to the anisotropy and modular parameters of the Baxter model. In
particular the \--adic ``regimes'' in the Macdonald polynomials correspond
to a discrete sequence of XXZ models. We also discuss the possibility of
``\--deforming'' Euler products.Comment: 25 page
P242: Prediction of falls risk with six different biomarkers in mild cognitive impairment using principal component analysis
Novel genetic loci associated with hippocampal volume
The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness
Asymmetric epoxidation of electron-deficient olefins
[EN] This paper focuses on the latest developments in asymmetric epoxidation of electron-deficient olefins since the review by Porter and Skidmore on chiral ligand-metal peroxide systems, polyamino acid catalysed and organocatalysed epoxidations. Particular attention has been paid to the most recent advances using chiral pyrrolidines as organocatalysts.The authors would like to thank the Spanish MEC for a FPU grant to M. G. N., the CICYT (CTQ2006-08296), FSE and Junta de Castilla y Leon (SA007A06) for financial support and Universidad de Salamanca for a grant to A. B. A.Diez, D.; Nunez, M.; Anton, A.; GarcĂa GarcĂa, P.; Moro, R.; Garrido, NM.; Marcos, I.... (2008). Asymmetric epoxidation of electron-deficient olefins. Current Organic Synthesis. 5(3):186-216. https://doi.org/10.2174/157017908785133429S1862165