293 research outputs found
Remarks on Finite W Algebras
The property of some finite W algebras to be the commutant of a particular
subalgebra of a simple Lie algebra G is used to construct realizations of G.
When G=so(4,2), unitary representations of the conformal and Poincare algebras
are recognized in this approach, which can be compared to the usual induced
representation technique. When G=sp(2,R) or sp(4,R), the anyonic parameter can
be seen as the eigenvalue of a W generator in such W representations of G. The
generalization of such properties to the affine case is also discussed in the
conclusion, where an alternative of the Wakimoto construction for sl(2) level k
is briefly presented. This mini review is based on invited talks presented by
P. Sorba at the ``Vth International Colloquium on Quantum Groups and Integrable
Systems'', Prague (Czech Republic), June 1996; ``Extended and Quantum Algebras
and their Applications to Physics'', Tianjin (China), August 1996; ``Selected
Topics of Theoretical and Modern Mathematical Physics'', Tbilisi (Georgia),
September 1996; to be published in the Proceedings.Comment: LaTeX, 16 pages, references adde
Relativistic center-vortex dynamics of a confining area law
We offer a physicists' proof that center-vortex theory requires the area in
the Wilson-loop area law to involve an extremal area. Area-law dynamics is
determined by integrating over Wilson loops only, not over surface fluctuations
for a fixed loop. Fluctuations leading to to perimeter-law corrections come
from loop fluctuations as well as integration over finite -thickness
center-vortex collective coordinates. In d=3 (or d=2+1) we exploit a contour
form of the extremal area in isothermal which is similar to d=2 (or d=1+1) QCD
in many respects, except that there are both quartic and quadratic terms in the
action. One major result is that at large angular momentum \ell in d=3+1 the
center-vortex extremal-area picture yields a linear Regge trajectory with Regge
slope--string tension product \alpha'(0)K_F of 1/(2\pi), which is the canonical
Veneziano/string value. In a curious effect traceable to retardation, the quark
kinetic terms in the action vanish relative to area-law terms in the large-\ell
limit, in which light-quark masses \sim K_F^{1/2} are negligible. This
corresponds to string-theoretic expectations, even though we emphasize that the
extremal-area law is not a string theory quantum-mechanically. We show how some
quantum trajectory fluctuations as well as non-leading classical terms for
finite mass yield corrections scaling with \ell^{-1/2}. We compare to old
semiclassical calculations of relativistic q\bar{q} bound states at large \ell,
which also yield asymptotically-linear Regge trajectories, finding agreement
with a naive string picture (classically, not quantum-mechanically) and
disagreement with an effective-propagator model. We show that contour forms of
the area law can be expressed in terms of Abelian gauge potentials, and relate
this to old work of Comtet.Comment: 20 pages RevTeX4 with 3 .eps figure
Genome-Wide RNAi Screen Identifies Regulators of Cardiomyocyte Necrosis
Regulation of cellular death is central to nearly all physiological routines and is dysregulated in virtually all diseases. Cell death occurs by two major processes, necrosis which culminates in a pervasive inflammatory response and apoptosis which is largely immunologically inert. As necrosis has long been considered an accidental, unregulated form of cellular death that occurred in response to a harsh environmental stimulus, it was largely ignored as a clinical target. However, recent elegant studies suggest that certain forms of necrosis can be reprogrammed. However, scant little is known about the molecules and pathways that orchestrate calcium-overload-induced necrosis, a main mediator of ischemia/reperfusion (IR)-induced cardiomyocyte cell death. To rectify this critical gap in our knowledge, we performed a novel genome-wide siRNA screen to identify modulators of calcium-induced necrosis in human muscle cells. Our screen identified multiple molecular circuitries that either enhance or inhibit this process, including lysosomal calcium channel TPCN1, mitophagy mediatorTOMM7, Ran-binding protein RanBP9, Histone deacetylase HDAC2, chemokine CCL11, and the Arp2/3 complex regulator glia maturation factor-γ(GMFG). Notably, a number of druggable enzymes were identified, including the proteasome β5 subunit (encoded by PSMB5 gene), which controls the proteasomal chymotrypsin-like peptidase activity. Such findings open up the possibility for the discovery of pharmacological interventions that could provide therapeutic benefits to patients affected by myriad disorders characterized by excessive (or too little) necrotic cell loss, including but not limited to IR injury in the heart and kidney, chronic neurodegenerative disorders, muscular dystrophies, sepsis, and cancers
Vortex waistlines and long range fluctuations
We examine the manner in which a linear potential results from fluctuations
due to vortices linked with the Wilson loop. Our discussion is based on exact
relations and inequalities between the Wilson loop and the vortex and electric
flux order parameters. We show that, contrary to the customary naive picture,
only vortex fluctuations of thickness of the order of the spatial linear size
of the loop are capable of producing a strictly linear potential. An effective
theory of these long range fluctuations emerges naturally in the form of a
strongly coupled Z(N) lattice gauge theory. We also point out that dynamical
fermions introduced in this medium undergo chiral symmetry breaking.Comment: 17 pages, LaTex file with 7 eps figures, revised references, minor
comments adde
Scattering States of Plektons (PARTICLES with Braid Group Statistics) in 2+1 Dimensional Quantum Field Theory
A Haag-Ruelle scattering theory for particles with braid group statistics is
developed, and the arising structure of the Hilbert space of multiparticle
states is analyzed.Comment: 18 pages, LATEX, DAMTP-94-9
Do You See What Eyes See? Implementing Inattentional Blindness
This paper presents a computational model of visual attention incorporating a cognitive imperfection known as inattentional blindness. We begin by presenting four factors that determine successful attention allocation: conspicuity, mental workload, expectation and capacity. We then propose a framework to study the effects of those factors on an unexpected object and conduct an experiment to measure the corresponding subjective awareness level. Finally, we discuss the application of a visual attention model for conversational agents
Fixed twist dynamics of SO(3) gauge theory
We perform a throughout study of 3+1 dim. SO(3) LGT for any fixed-twist
background. We concentrate in particular on the physically significant trivial
and 1-twist sectors. Introducing a Z(2) monopole chemical potential the 1st
order bulk transition is moved down in the strong coupling region and weakened
to 2nd order in the 4-dim Ising model universality class. In this extended
phase diagram we gain access to a confined phase in every fixed twist sector of
the theory. The Pisa disorder operator is employed together with the Polyakov
loop to study the confinement-deconfinement transition in each sector. Due to
the specific properties of both operators, most results can be used to gain
insight in the ergodic theory, where all twist sectors should be summed upon.
An explicit mapping of each fixed twist theory to effective positive plaquette
models with fixed twisted boundary conditions is applied to better establish
their properties in the different phases.Comment: 20 pages, 11 Figures. Minor changes in text and figures, to appear in
Eur.Phys.J.
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Detection of underground structures and tunnels
This is the final report of a one year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. There is a continuing need in the United States defense and drug interdiction for effective over, convert, and standoff means of detecting underground tunnels, structures, and objects. This project sought to begin an assessment of electromagnetic and gravitational gradient detection approaches to the detection of underground structures and tunnels
The genomic basis of the plant island syndrome in Darwin’s giant daisies
The repeated, rapid and often pronounced patterns of evolutionary divergence observed in insular plants, or the ‘plant island syndrome’, include changes in leaf phenotypes, growth, as well as the acquisition of a perennial lifestyle. Here, we sequence and describe the genome of the critically endangered, Galápagos-endemic species Scalesia atractyloides Arnot., obtaining a chromosome-resolved, 3.2-Gbp assembly containing 43,093 candidate gene models. Using a combination of fossil transposable elements, k-mer spectra analyses and orthologue assignment, we identify the two ancestral genomes, and date their divergence and the polyploidization event, concluding that the ancestor of all extant Scalesia species was an allotetraploid. There are a comparable number of genes and transposable elements across the two subgenomes, and while their synteny has been mostly conserved, we find multiple inversions that may have facilitated adaptation. We identify clear signatures of selection across genes associated with vascular development, growth, adaptation to salinity and flowering time, thus finding compelling evidence for a genomic basis of the island syndrome in one of Darwin’s giant daisies
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